Heat Flow Below 100°k and its Technical Applications. Proceedings of the International Institute of...

INTERNATIONAL INSTITUTE OF REFRIGERATION

I N S T I T U T I N T E R N A T I O N A L D U F R O I D

HEAT FLOW BELOW 100°K A N D ITS TECHNICAL

APPLICATIONS

PROCEEDINGS OF THE

INTERNATIONAL INSTITUTE OF REFRIGERATION

COMMISSION 1

GRENOBLE 1965

SYMPOSIUM PUBLICATIONS DIVISION

PERGAMON PRESS

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Copyright © 1966 The International Institute of Refrigeration

and Pergamon Press Ltd.

Edited by the International Institute of Refrigeration and distributed by Pergamon Press Ltd.

Library of Congress Catalog Card No. 59-15722

P R I N T E D I N B E L G I U M BY C E U T E R I C K I N L O U V A I N

3002/63

PREFACE

I N NOVEMBER 1969 the International Commission on Radiological Protection adopted a Report by Committee 3 entitled Protection against Ionizing Radiation from External Sources, which was issued in the following year as ICRP Publication 15. The task of compiling material for that publication was undertaken by a Task Group whose membership is given below. The Task Group also assembled data that were intended to form appendices to the report, but the death of its secretary, Β . E . Jones, led to delays, which were minimized by the decision to issue the appendices as a separate supplement. Accordingly, the Commission, at its meeting in April 1971, appointed a new Task Group, the membership of which is also given below, to complete the preparation of the data for the supplement.

Task Group (1967-71) Task Group (1971-72)

P. GRANDE {Chairman) M. C. O'RIORDAN {Chairman)

K. BECKER {Vice-Chairman) M. J. D U G G A N

Β . E . JONES {Secretary) T. O . MARSHALL

J. P. KELLEY Ε . E . SMITH

K . KOREN

C. B . MEINHOLD

P. PELLERIN

R. H. THOMAS

Membership of Committee 3 during the preparation of ICRP Publication 15 and the Supple-ment:

B . LINDELL {Chairman) H . O . WYCKOFF (to 1969)

Ε . E . SMITH {Vice-chairman) J. P. KELLEY (from 1969)

L . - E . LARSSON Ε . E . KOVALEV (from 1969)

F. P. COWAN R. OLIVER (from 1969)

S. TAKAHASHI P. PELLERIN (from 1969)

J. DUTREIX (to 1969) K . A. ROWLEY (from 1969)

E . D . TROUT (to 1969)

This report also includes amendments to ICRP Publication 15 and extracts from a statement issued by the Commission in April 1971.

V

A M E N D M E N T S TO ICRP P U B L I C A T I O N 15

Paragraph 17

Delete the third, fourth, and fifth sentences and replace with the following: "When the incident radiation is neutrons only and the tissue kerma free in air (in rads) is known, this kerma may be assumed to be numerically equal to the absorbed dose in rads at any point in the body, provided the dose from the capture gamma rays can be ignored. In such circumstances, if the energy of the incident neutrons is not known, a QF of 10 should be assumed. The capture gamma rays become important when a significant part of the neutron spectrum lies below 0.1 MeV, because in these circumstances the capture gamma rays could give rise to a maximum absorbed dose in the body which is as much as 100 times that due to charged particles produced by other neutron reactions. An alternative approach is to use a suitable rem-meter to give an adequate determination of the dose equivalent."

Paragraph 19

After "Appendices 6 and 7" insert the words "of the supplement".

Paragraph 84

For "20:108" write "108".

vi

C O M M I S S I O N S T A T E M E N T ON EXTERNAL R A D I A T I O N S O U R C E S

AFTER the meeting of the International Commission on Radiological Protection in April 1 9 7 1 , a statement was issued, which included two items on external radiation sources. These statements are reproduced below.

Exposure from intra-oral x-ray tubes

The Commission was informed about a new radiation protection problem posed by the use of intra-oral x-ray tubes in dental radiography. With the present trend to use tubes of decreasing diameter, the radiation doses at the surface of the tube may amount to between 5 0 and 1 0 0 rads, or even more, per exposure. Such uses should be clearly deprecated. It is of interest to note that intra-oral x-ray tubes, if used with the appropriate filtration and extra-sensitive films, may not give higher doses than 5 - 1 0 rads to limited parts of the tongue. With these precautions the intra-oral tubes may even have certain advantages from the point of view of radiation protection: they cause lower integral doses than regular dental tubes, and the exposure of the staff is much reduced. Extra "shielding in the applicator can easily limit the radiation field to that which is needed for the examination, thus further reducing the integral dose.

Population dose from consumer products

The Commission noted the increasing use of a number of consumer products containing small amounts of radioactive material, and the contribution to the population dose that these, taken together, could make, even though the dose from individual sources is at present extremely small. In considering the relevance of this to the dose limit for the population, the Commission emphasized the importance of national authorities assessing the contribution being made by these products, so that an effective means of control may be instituted. In this regard, the Commission wishes to draw attention to a publication of the Nuclear Energy Agency (Basic approach for safety analysis and control of products containing radio-nuclides and available to the general public, 1 9 7 0 ) , as an example of a method by which the total individual and population doses from all consumer products may be subject to administrative control.

vii

LIST OF F I G U R E S

F I G . 1. Collision stopping power of protons and electrons in water as a function of energy F I G . 2 . Quality factor as a function of collision stopping power in water F I G . 3 . Quality factors of charged particles as a function of energy. F I G . 4 . Dose equivalent as a function of depth in a 3 0 cm thick slab of tissue irradiated normally, on one

face, by a broad beam of monoenergetic neutrons F I G . 5 . Dose equivalent as a function of depth in a 3 0 cm thick slab of tissue irradiated normally, on one

face, by a broad beam of monoenergetic protons F I G . 6 . * Calculated percentage depth-dose distributions in water for broad beams of normally incident

monoenergetic electrons of high to very high energy F I G . 7 . Percentage depth-dose distributions in tissue-like material for beta particles from large plane

sources virtually in contact with the material. (The maximum energies of the beta particles, in MeV, are shown in parentheses.)

F I G . 8 . Percentage depth-dose distributions along the minor axis of an elliptical water phantom for broad beams of low and high energy photons, from an infinitely distant source, incident in the same direction

F I G . 9 . Backscatter factors at the surface and 5 cm from the surface of an elliptical water phantom for broad beams of low and high energy photons incident along the minor axis

F I G . 10 . Average dose absorbed in the testes per unit exposure measured by a personal dosemeter on the front of the trunk (curves A and B) and per unit exposure measured in free air at the position of the centre of the body (curve C). Curve A: irradiation from the back only. Curve Β: irradiation from the front only. Curve C: rotation during exposure simulating irradiation from all sides

F I G . 1 1 . Average dose absorbed in the ovaries per unit exposure measured by a personal dosemeter on the front of the trunk (curves A and B) and per unit exposure measured in free air at the position of the centre of the body (curve C). Curve A: irradiation from the back only. Curve Β: irradiation from the front only. Curve C: rotation during exposure simulating irradiation from all sides

F I G . 12 . Average dose absorbed in bone marrow per unit exposure measured by a personal dosemeter on the front of the trunk (curves A and B) and per unit exposure measured in free air at the position of the centre of the body (curve C). Curve A: irradiation from the back only. Curve B: irradi-ation from the front only. Curve C: rotation during exposure simulating irradiation from all sides.

F I G . 1 3 . Conversion factors for electrons. Unidirectional broad beam, normal incidence. The curve indicates the values recommended by the Commission

F I G . 1 4 . Conversion factors for neutrons. Unidirectional broad beam, normal incidence. The curves indicate the values recommended by the Commission

F I G . 1 5 . Effective quality factors for neutrons, that is, maximum dose equivalent divided by the absorbed dose at the depth where the maximum dose equivalent occurs. The curve indicates the values recommended by the Commission

F I G . 16 . Conversion factors for protons. Unidirectional broad beam, normally incident on a 3 0 cm thick phantom. The curve indicates the values recommended by the Commission

F I G . 17 . Conversion factors for photons. Unidirectional broad beam, normal incidence. The curves indicate the values recommended by the Commission

F I G . 1 8 . Relationship between photon fluence rate and exposure rate F I G . 19 . Broad-beam dose equivalent transmission of 1 4 - 1 5 MeV neutrons through slabs of concrete,

density 2 . 4 g/cm 3 , and water F I G . 2 0 . Broad-beam dose equivalent transmission of 1 4 - 1 5 MeV neutrons through slabs of steel (density

7.8 g/cm 3) and polyethylene ( 0 . 9 4 g/cm 3) and a combination of steel and polyethylene F I G . 2 1 . Broad-beam dose equivalent transmission of 2 4 1 A m - B e neutrons through water and through

polyethelene, density 0 . 9 4 g/cm 3

F I G . 2 2 . Broad-beam dose equivalent transmission of 2 5 2 C f neutrons through slabs of lead (density 1 1 . 3 5 g/cm 3) and polyethylene ( 0 . 9 6 g/cm 3)

F I G . 2 3 . Broad-beam absorbed dose transmission of 2 5 2 C f gamma rays through slabs of lead (density 1 1 . 3 5 g/cm 3), steel (7 .8 g/cm 3), and concrete ( 2 . 3 5 g/cm 3)

F I G . 2 4 . Neutron dose equivalent rates at the surfaces of spheres of polyethylene (density 0 . 9 6 g/cm 3) paraffin ( 0 . 9 2 g/cm 3), water, and concretes ( 2 . 3 5 g/cm 3), each with 1 μ% 2 5 2 C f at its centre

F I G . 2 5 . Neutron absorbed dose transmission through slab shields of unidirectional broad beams of 0 .5 MeV neutrons incident at various angles to the slabs

4 2 4 3 4 4

4 5

4 6

4 7

4 8

4 9

5 0

5 1

5 2

5 3

5 4

5 5

5 6

5 7

5 8 5 9

6 0

6 1

6 2

6 3

6 4

6 5

6 6

ix

χ LIST OF FIGURES

F I G . 26. Neutron absorbed dose transmission through slab shields of unidirectional broad beams of 1 MeV neutrons incident at various angles to the slabs



F I G . 29. Range of electrons and protons in air F I G . 30. Range of electrons, protons, and alpha particles in water F I G . 31. Range of electrons, protons, and alpha particles in lead F I G . 32. Bremsstrahlung from 1 0 6 R h beta particles stopped in the metal matrix; also from 9 0 Y , 9 0 S r ,

1 4 7 P m , and 1 7 1 T m beta particles stopped in the oxide matrices F I G . 33. Absorbed dose transmission of diverging broad beams of bremsstrahlung from 9 0 S r - 9 0 Y beta

particles stopped in the oxide matrix through slabs of steel (density 7.8 g/cm 3), lead (11.35 g/ cm 3 ) , and uranium (18.9 g/cm 3). Beam axes normal to shields. See note in text regarding uranium

F I G . 34. Output of constant potential x-ray generator at 10 cm target distance for various beam nitrations and a tungsten reflection target. The 1 mm beryllium is the tube window. For output at 1 m, see Glassere/fl/. (1959)

F I G . 35. Output of constant potential x-ray generator at 1 m target distance for various beam nitrations • and a tungsten reflection target. The 1 mm beryllium is the tube window

F I G . 36. Output of constant potential x-ray generators at 1 m target distance for various beam nitrations. The upper curve. is for a 2.8 mm tungsten transmission target followed by 2.8 mm copper, 18.7 mm water, and 2.1 mm brass. The other curves are for tungsten reflection targets with 0.5 mm and 3 mm copper total filtration

F I G . 37. X-ray output of linear accelerators, per unit average beam current, 1 m from a high atomic number transmission target of optimum thickness. The ordinate is the absorbed dose rate measured in air. This chart may also be used for betatrons, although the target configuration is different

F I G . 38. Broad-beam transmission of χ rays through mild steel, density 7.8 g/cm 3 . Constant potential generator; tungsten reflection target; 1 mm beryllium total beam filtration. Ordinate intercepts are: 8.38 at 50 kV; 6.58 at 40; 4.49 at 30.

F I G . 39. Broad-beam transmission of χ rays through Perspex, density 1.2 g/cm 3 . Constant potential generator, tungsten reflection target; 1 mm beryllium total beam filtration. For ordinate intercepts, see Fig. 38.

F I G . 40. Broad-beam transmission of χ rays through concrete, density 2.35 g/cm 3 . 50 to 300 kV: half-wave generator; tungsten reflection target; total beam filtration 1 mm aluminium at 50 kV, 1.5 at 70, 2 at 100, and 3 at 125 to 300. 400 kV: constant potential generator; gold reflection target; 3 mm copper total beam filtration. Ordinate intercepts are 2.7 at 400 kV, 2.4 at 300, 1.6 at 250, 1.02 at 200, 0.6 at 150, 0.45 at 125, 0.32 at 100,0.24 at 70, 0.19 at 50.

F I G . 41. Broad-beam transmission of χ rays through lead, density 11.35 g/cm 3. Constant potential generator; tungsten reflection target; 2 mm aluminium total beam filtration. Ordinate intercepts are 3.3 at 200 kV, 2.1 at 150, 1.1 at 100, 0.7 at 75, 0.3 at 50.

F I G . 42. Broad-beam transmission of χ rays through lead, density 11.35 g/cm 3 . 250 kV: constant poten-tial generator; tungsten reflection target; 0.5 mm copper total beam filtration. 300 and 400 kV: constant potential generator; gold reflection target; 3 mm copper total beam filtration. Ordinate intercepts are 2.7 at 400 kV, 1.3 at 300, 1.9 at 250

F I G . 43. Broad-beam transmission of χ rays through concrete, density 2.35 g/cm 3 . Constant potential generators. 0.5 and 1.0 MV: 2.8 mm tungsten transmission target followed by 2.8 mm copper, 18.7 mm water, and 2.1 mm brass beam filtration. 2 MV: high atomic number transmission target; 6.8 mm lead equivalent total beam filtration. 3 MV: gold transmission target; 11 mm lead equivalent total beam filtration. Ordinate intercepts are 850 at 3 MV, 300 at 2, 20 at 1,1 at 0.5

F I G . 44. Broad-beam transmission of χ rays through lead, density 11.35 g/cm 3 . Constant potential generators. 0.5 and 1.0 MV: 2.8 mm tungsten transmission target followed by 2.8 mm copper, 18.7 mm water, and 2.1 mm brass beam filtration. 2 MV: high atomic number transmission target; 6.8 mm lead equivalent total beam filtration. Ordinate intercepts are 300 at 2 MV, 20 at 1,1 at 0.5

F I G . 45. Broad-beam transmission of χ rays through concrete, density 2.35 g/cm 3 . 4 MV: linear acceler-ator; 1 mm gold target followed by 20 mm aluminium beam flattener. 6-38 MV: Betatron; target and filtration not stated. The 38 MV curve may be used up to 200 MV (Miller and Kennedy, 1956)

F I G . 46. Broad-beam transmission of χ rays through lead, density 11.35 g/cm 3 . Betatron; platinum wire target 2 mm χ 8 mm; no beam filtration. For higher potentials, see Miller and Kennedy (1956)

F I G . 47. Broad-beam transmission of gamma rays from various radionuclides through concrete, density 2.35 g/cm 3

67

68

69 70 71 72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

LIST OF FIGURES

F I G . 48. Broad-beam transmission of gamma rays from various radionuclides through concrete, density 2.35 g/cm 3

F I G . 49. Broad-beam transmission of gamma rays from various radionuclides through steel, density 7.8 g/cm3

F I G . 50. Broad-beam transmission of gamma rays from various radionuclides through lead, density 11.35 g/cm3

F I G . 51. Broad-beam transmission of gamma rays from various radionuclides through lead, density 11.35 g/cm3

F I G . 52. Broad-beam transmission of gamma rays from various radionuclides through uranium, density 18.9 g/cm3. See note in the text of Appendix 11 regarding uranium

F I G . 53. Variation with potential of the absorbed dose rate measured in air due to χ rays scattered at 90° from various materials. The beam is obliquely incident on the thick scatterer. Per cent scatter is related to primary beam measurements in free air at the point of incidence

F I G . 54. Scattering patterns of diverging x-ray and gamma-ray beams normally incident on a concrete shield. Per cent scatter is related to primary beam measurements in free air at the point of incidence

F I G . 55. Broad-beam transmission of 1 3 7 C s gamma rays scattered at various angles from an oblique concrete wall through concrete, density 2.35 g/cm3

F I G . 56. Broad-beam transmission of l 3 7 C s gamma rays scattered at various angles from an oblique concrete wall through lead, density 11.35 g/cm3

F I G . 57. Broad-beam transmission of 6 0 C o gamma rays scattered at various angles from a patient-simulating phantom through concrete, density 2.35 g/cm3

F I G . 58. Broad-beam transmission of 6 0 C o gamma rays scattered at various angles from a patient-simulating phantom through lead, density 11.35 g/cm3

F I G . 59. Broad-beam transmission of 6 MV χ rays scattered at various angles from a patient-simulating phantom through concrete, density 2.35 g/cm3

xi

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98

99

100

LIST OF TABLES

T A B L E 1. Summary of depth-dose calculations in tissue for neutrons, protons, electrons, and photons T A B L E 2. Dose equivalent rate as a function of depth in water for normally incident unidirectional

broad beams of electrons and photons T A B L E 3. Conversion factors for electrons T A B L E 4. Conversion factors and effective quality factors for neutrons T A B L E 5. Conversion factors and effective quality factors for protons T A B L E 6. Conversion factors and mass energy absorption coefficients in water 0* β ο/ρ) for photons T A B L E 7. Energy of neutrons produced by different nuclear reactions involving light nuclei T A B L E 8. Characteristics of some radioactive neutron sources T A B L E 9. Neutron fluence rates and dose rates 1 m from 1 g 2 5 2 C f T A B L E 10. Photon fluence rates and dose rates 1 m from 1 g 2 5 2 C f T A B L E 11. Composition of materials used in calculations for Figs. 25-28. T A B L E 12. Characteristics of the beta sources considered in Appendix 11 T A B L E 13. Photon energy groups and emission rates selected for the shielding calculations for brems-

strahlung from 9 0 S r - 9 0 Y beta particles stopped in the SrO matrix T A B L E 14. Outputs of gamma-ray sources T A B L E 15. References and irradiation geometries for x-ray and gamma-ray transmission data T A B L E 16. Approximate half-value-thicknesses and tenth-value-thicknesses for heavily attenuated broad

beams of χ rays T A B L E 17. Approximate half-value-thicknesses and tenth-value-thicknesses for heavily attenuated broad

beams of gamma rays T A B L E 18. Lead equivalence of various materials for low energy χ rays T A B L E 19. Per cent of absorbed dose rate due to incident radiation scattered to 1 m by a tissue-like

phantom for 400 c m 2 irradiated area T A B L E 20. Primary x-ray beam shielding requirements for 0.1 rem per week T A B L E 21. Scatter and leakage x-ray shielding requirements for 0.1 rem per week

xii

7

7 10 12 14 16 18 18 19 19 20 22

23 24 26

27

27 28

29 33 34

I N T R O D U C T I O N

THIS publication is the Supplement to ICRP Publication 15 (1969) referred to in the Preface to that report. It consists of twelve appendices, which are numbered in accord-ance with references in the text of Publication 15.

The appendices contain information for implementing the recommendations of ICRP Publication 15 and therefore relate to the sources of external radiation encountered in medical, dental, and veterinary radiology, and in industry and research. The reader will appreciate the difficulty of selecting and com-pressing material for presentation in this form and the need to consult the original references as occasion demands.

A substantial portion of the Supplement is allocated to data on shielding, but some shielding problems, such as those associated with nuclear reactors and ultra high energy accelerators, are outside its scope. There is, however, a copious shielding literature, and an excellent citation service is provided by the Radiation Shielding Information Center at Oak Ridge National Laboratory. The creation of the European Shielding Information Service at Ispra has recently been announced. The addresses of both organizations are given

with the general shielding bibliography on page 41.

In 1971 the International Commission on Radiation Units and Measurements published a report entitled "Radiation Quantities and Units" (ICRU Report 19, 1971), which superseded a report with the same title pub-lished in 1968. ICRU Report 19 proposed new symbols for some terms in radiation protection, and these new symbols have been introduced here. ICRP Publication 15, how-ever, uses the old symbols, and the following changes should be noted: dose equivalent, Η for DE; quality factor, Q for QF.

.The International Commission on Radi-ation Units and Measurements recommends the use of the International System of Units (SI) for fundamental quantities, but continues to recognize some existing special units. Accordingly, the International Commission on Radiological Protection will continue to use the special units and certain other con-ventional multiples and submultiples of units, until agreement is reached for their abandon-ment. The following tabulation of quantities in SI and special units is extracted from ICRU Report 19, to which the reader is referred for a fuller discussion of the subject.

Name Symbol SI unit Special unit

Absorbed dose D J k g " 1 rad Absorbed dose rate ύ J k g ^ s " 1 r a d s " 1

Exposure X C k g - 1 R (roentgen) Exposure rate X A k g " 1 R s " 1

Linear energy transfer U J m " 1 keV/xm- 1

Activity A s - 1 Ci (curie)

1

REPORT OF COMMITTEE 3 2

ultra high energy from a few hundred MeV upward.

This nomenclature is also used for x-ray generating potentials.

Axis labels and column headings are chosen so as to bring out the physical meanings of quantities, and for this reason, the use of exponents has been limited.

Throughout the Supplement, four radiation energy regions are identified. They are defined as follows (Cowan, 1969):

low energy below a few hundred keV;

high energy from a few hundred keV to a few MeV;

very high energy from a few MeV to a few hundred MeV;

A P P E N D I X 1

C O L L I S I O N S T O P P I N G POWER OF CHARGED PARTICLES IN WATER

SINCE quality factor is defined in terms of radiation protection. ICRU Report 1 6 ( 1 9 7 0 ) collision stopping power in water (see Appen- provides a useful summary on stopping dix 2 ) , this latter parameter, as a function of powers, charged particle energy, is important in

C O L L I S I O N S T O P P I N G P O W E R O F H E A V Y C H A R G E D P A R T I C L E S IN W A T E R

Extensive tabulations of collision stopping power for heavy charged particles may be found in Rich and Madey ( 1 9 5 4 ) , Atkinson and Willis ( 1 9 5 7 ) , Barkas and Berger ( 1 9 6 4 ) ,

and Fano ( 1 9 6 4 ) .

The foregoing tabulations extend down to a proton energy of 1 MeV. Experimental deter-minations, which have been summarized by Whaling (1958)' , are available for proton energies between 0 . 0 1 MeV and 1 MeV, the values being derived from Phillips ( 1 9 5 3 ) , Reynolds et al. ( 1 9 5 3 ) , and Milani et ai

( 1 9 5 8 ) . Fig. 1 summarizes the data for proton

energies between 0 . 0 1 MeV and 1 0 0 0 MeV. The collision stopping power of other

heavy charged particles in water can be readily calculated, with accuracy sufficient for the normal purposes of radiation protection, from the data for protons: for a particle of mass Μ and charge Ze, the energy scale of Fig. 1 should be multiplied by a factor (M/Mp), where Mp is the proton mass, and the collision stopping power scale should be multiplied by a factor Z 2 . When higher accuracy is required, the tabulations men-tioned above should be consulted.

C O L L I S I O N S T O P P I N G P O W E R O F E L E C T R O N S IN W A T E R

Because of its special importance, the collision stopping powers for electrons are collision stopping power of electrons in water given in Fano ( 1 9 6 4 ) . is also plotted in Fig. 1. Tabulations of

3

A P P E N D I X 2

I N T E R P O L A T E D VALUES OF QUALITY FACTOR

INTERPOLATED values of quality factor as a (1969) and is presented as a common basis for function of collision stopping power in water dose equivalent calculation. The table is can be obtained from Fig. 2. This curve is reproduced below for ease of reference, based on Table 1 of ICRP Publication 15

Lao-Q R E L A T I O N S H I P

Loo in water (keV/ftm) Q

3.5 (and less) 1 7 2 23 5 53 10 175 (and above) 20

4

A P P E N D I X 3

QUALITY FACTOR AS A F U N C T I O N OF CHARGED PARTICLE ENERGY

THE data in Appendices 1 and 2 may be used to calculate the values of quality factor as a function of particle energy (Cowan et al.y

1964). Figure 3 shows some calculated values of quality factor as a function of energy for electrons, muons, pions, kaons, protons, deuterons, tritons, 3 He, and alpha particles.

These data are necessary when calculating dose equivalent by the methods reviewed in Appendix 4, since absorbed dose at a point of interest is delivered by particles with collision stopping powers distributed over a wide range.

R . P . 21—Β

5

A P P E N D I X 4

CALCULATION OF A B S O R B E D D O S E AND D O S E E Q U I V A L E N T D I S T R I B U T I O N IN THE B O D Y

THE data in this Appendix are provided so that organ or tissue doses can be determined for radiological protection purposes; they should not be used in radiotherapy.

In many situations, the absorbed dose and dose equivalent distributions in the human body are identical; in the case of irradiation by photons or electrons below about 10 MeV, for example, the quality factor is unity. The detailed evaluation of whole body and critical organ dose equivalent for other radiation fields, where the quality factor is not unity, is however a complex process.

Factors significantly influencing absorbed dose and dose equivalent distributions are:

the types of radiation present; angular distribution and energy spectrum

of incident radiation; orientation of the body in the radiation

field and movement of the body during exposure;

inhomogeneity of the body, such as the presence of body cavities or bone.

On absorption in the body, primary particles produce a number of secondary particles of lower energy. The local biological effect is therefore due to the sum of the effects of a number of particles reaching the volume under consideration from all directions. The collision stopping power, and hence the quality factor, is in general different from that of the primary particles, and of course the collision stopping power of each particle varies along its track. The effective quality factor applicable to the volume of tissue in question must therefore be obtained from an appropriate weighted average, as discussed in paragraph 13 of ICRP Publica-tion 15 (1969).

D E P T H - D O S E E Q U I V A L E N T C A L C U L A T I O N S F O R N E U T R O N S A N D F O R V E R Y H I G H T O U L T R A H I G H E N E R G Y P R O T O N S ,

E L E C T R O N S , A N D P H O T O N S

Extensive calculations have been made of the depth-dose equivalent distribution in a 30 cm thick slab of material, infinite in lateral extent and equivalent to soft tissue, the front face of which is irradiated by broad beams of monoenergetic neutrons, protons, electrons, and photons. As Table 1 shows, neutron cal-culations range from thermal to ultra high energies; in the other cases, calcula-tions cover the very high and ultra high ranges.

For neutrons and protons, the influence of the angular distribution of the incident particles has been investigated by calculating the upper and lower bounds of dose equiva-

lents in cases of practical interest; with neutrons greater than 0.5 MeV and protons greater than 100 MeV, calculations were done both for normally and isotropically incident particles. From these results, depth-dose equivalent curves for bilateral irradiations can be readily obtained and may be used as an approximation to the case of omni-directional irradiation.

Auxier et al (1968) and Snyder (1971) have reported calculations of dose equivalent and absorbed dose at various depths for neutron irradiation of a finite cylindrical phantom. These calculations embody the best cross section data now available, but they are

PROTECTION AGAINST IONIZING RADIATION FROM EXTERNAL SOURCES 7

S U M M A R Y O F D E P T H - D O S E C A L C U L A T I O N S I N T I S S U E F O R N E U T R O N S , P R O T O N S , E L E C T R O N S , A N D

P H O T O N S

Incident angular Particle Energy range distribution Phantom Authors

1. Neutrons Thermal Normal Semi-infinite slab Snyder (1950) 2. Neutrons Thermal-10 MeV Normal Semi-infinite slab Snyder (1957) 3. Neutrons Thermal-15MeV Normal Cylinder Auxier*?/a/.(1968) 4. Neutrons Thermal-14 MeV Normal Cylinder Snyder (1971) 5. Neutrons 0.5-60 MeV Normal and

isotropic Semi-infinite slab Irving et al. (1967)

6. Neutrons 60-400 MeV Normal and ' isotropic

Semi-infinite slab Zerby and Kinney (1965)

7. Neutrons 60-3 000 MeV Normal Semi-infinite slab Alsmiller etal. (1970) · 8. Neutrons 600-2 000 MeV Normal and

isotropic Semi-infinite slab Wright etal. (1969)

9. Protons 100-400 MeV Normal Semi-infinite slab T u r n e r s al. (1964) 10. Protons 100-400 MeV Normal and

isotropic Semi-infinite slab NeufekU/a/.(1966)

11. Protons 250-660 MeV Normal Semi-infinite slab Dudkin etal. (1972) 12. Protons 400-3 000 MeV Normal Semi-infinite slab Alsmiller al. (1970) 13. Protons 600-2 000 MeV Normal and

isotropic Semi-infinite slab Wright et al. (1969)

14. Electrons 100 MeV-20 GeV Normal Semi-infinite slab Alsmiller and Moran (1968) 15. Electrons 100MeV-20 GeV Normal Semi-infinite slab Beck (1970) 16. Photons 10MeV-20 GeV Normal Semi-infinite slab Alsmiller and Moran (1968) 17. Photons 150 MeV-20GeV Normal Semi-infinite slab Beck(1970)

T A B L E 2

D O S E E Q U I V A L E N T R A T E A S A F U N C T I O N O F D E P T H I N W A T E R F O R N O R M A L L Y I N C I D E N T

U N I D I R E C T I O N A L B R O A D B E A M S O F E L E C T R O N S A N D P H O T O N S

mrem/h per unit fluence rate averaged over depth interval Incident energy,

MeV 0-7.5 cm 7.5-15.0 cm 15.0-22.5 cm 22.5-30.0 cm

Electrons 1 x 10 2 0.16 0.16 0.14 0.10 2 χ 10 2 0.16 0.18 0.19 0.18 5 χ 10 2 0.18 0.20 0.22 0.25 1 x 10 3 0.18 0.21 0.25 0.32

5.2 x 10 3 0.20 0.25 0.36 0.42 1 χ 10* 0.21 0.27 0.37 0.49 2 χ 10* 0.22 0.28 0.43 0.57

Photons 1 χ 10 1 0.007 0.009 0.007 0.007 2 χ 10 1 0.010 0.015 0.012 0.013 5 χ 10 l 0.013 0.030 0.032 0.028 1 χ 10 2 0.016 0.042 0.051 0.065

2 χ 10 2 0.019 0.049 0.077 0.095 5 χ 10 2 0.021 0.062 0.092 0.14 1 χ 10 3 0.023 0.063 0.12 0.16

5.2 χ 10 3 0.026 0.081 0.14 0.22

1 χ 10* 0.029 0.088 0.16 0.24 2 χ 10* 0.03 0.10 0.15 0.26

T A B L E 1

8 REPORT OF COMMITTEE 3

limited to normal incidence and to energies below 15 MeV. These more recent calcula-tions are in substantial agreement with the slab model calculations presented here.

Figures 4 and 5 show typical depth-dose equivalent curves in soft tissue for neutrons and protons of various energies, based upon normal incidence on a semi-infinite slab. Fuller information will be found in the papers referred to in Table 1.

It is convenient to present the data for very

high and ultra high energy electrons and photons in tabular form; depth-dose equiv-alent histograms can be readily constructed. Table 2 presents the results of the Alsmiller and Moran (1968) calculations for broad beams normally incident on semi-infinite slabs of water. The values given in the table are averaged over the stated 7.5 cm depth intervals. These data are compared with those of Svensson and Nelson (1970) and Beck (1970) in Appendix 5.

C A L C U L A T E D D E P T H - D O S E D A T A F O R H I G H T O V E R Y H I G H E N E R G Y E L E C T R O N S

Calculated percentage depth-dose curves in water for broad parallel beams of mono-energetic electrons are presented in Fig. 6 (Berger and Seltzer, 1969); the electrons are assumed to be normally incident on a semi-infinite medium. Depth-dose distributions are sensitive to beam geometry, so these curves may differ from those obtained with

finite field sizes and slightly diverging beams. In practice, furthermore, electron beams are unlikely to be monoenergetic; consequently, it is always advisable to map the distribution in the situation of interest.

Experimental depth-dose data for broad beams of high energy electrons will be found in Fielden and Holm (1970).

E X P E R I M E N T A L D E P T H - D O S E D A T A F O R B E T A P A R T I C L E S

Percentage depth-dose distributions in tissue-like material for beta particles from large plane sources virtually in contact with the absorbing material are given in Fig. 7 (Francis and Seymour, 1972). The data were obtained with a 1 cm diameter extrapolation chamber having a 1 mg/cm 2 window. The sources were in the form of thin foils, pro-

viding low filtration, and they were backed with thick plastic. The foils measured 4 cm X 4 cm, except 6 3 N i , which measured 3 cm x 1 cm. For 6 3 N i and 1 4 7 P m , the absorbing material was polyethylene terephthalate; for 2 0 4 T 1 and 9 0 S r - 9 0 Y , it was polymethyl metha-crylate. Beta particle depth-dose distributions are very dependent on irradiation geometry.

E X P E R I M E N T A L D E P T H - D O S E D A T A F O R L O W A N D H I G H E N E R G Y P H O T O N S

Percentage depth-dose distributions for broad beams of low and high energy photons are given in Fig. 8 (Delafield, 1963). The distributions are along the minor axis of an elliptical water-filled trunk phantom for radiation incident in the same direction; they are normalized to the surface to simulate

infinite source distance, and the surface measurements were made under equilibrium conditions. The sources are uncollimated radionuclides and highly filtered broad x-ray beams giving reasonably monoenergetic radiation.


T H E I N T E R P R E T A T I O N O F R A D I A T I O N M E A S U R E M E N T S I N T E R M S O F O R G A N D O S E S

The basic recommendations of the Com-mission are expressed as dose equivalents to the organs or tissues of the body (ICRP Publication 9, 1965). The results of radiation measurements in the work place, or on the surface of the trunk, may need to be trans-lated to the location of interest in the body. As well as taking into account the spectral, geometrical, and anatomical factors in this procedure, it may be necessary to estimate the degree to which a measurement is representa-tive of an irradiation. The general principles of this subject are treated in ICRP Publication 12(1968).

The interpretation of such measurements of low and high energy photons is of special interest. Backscatter factors for the irradiation conditions described in the preceding section (Delafield, 1963) are presented in Fig. 9; they indicate that the absorbed dose at the body surface may be 50 % higher than at the same location in the absence of the body. This difference decreases with increasing distance from the body, but it may still amount to 25 % for a separation of 5 cm.-

In practice, it is usually necessary to estimate organ doses either from the reading of a personal dosemeter worn on the front of the trunk, or from the exposure, measured in

free air, at the position to be occupied by the body. Figures 10 to 12 give experimental results (Jones, 1966) which are useful for making such estimates. The absorbed dose in tissue was determined from measurements in a lifelike phantom irradiated from the front, from the back, and during rotation about the vertical axis by a broad horizontal beam, rotation during exposure simulating irradi-ation from all sides. The sources were radio-nuclides or filtered χ rays. The results were corrected by the inverse square law and are directly applicable to distant sources.

Figures 10 and 11 give the average dose absorbed in the testes and ovaries for unit exposure measured by a personal dosemeter when the phantom is irradiated from the back (curves marked A) or from the front (curves marked B); these figures also give, for rota-tional irradiation, the average organ dose per unit exposure measured in free air at the position of the centre of the phantom (curves marked C). Figure 12 gives the average bone marrow dose, weighted according to marrow distribution in the body, for the same con-ditions of irradiation and exposure measure-ment. The results for the ovaries may also be applied to the abdominal mid-line (Clifford and Facey, 1970).

D E P T H - D O S E E Q U I V A L E N T , C O N V E R S I O N F A C T O R S , A N D E F F E C T I V E Q U A L I T Y F A C T O R S

In general, irradiation of the body by normally incident particles produces the largest dose equivalent per unit fluence. The values of conversion factor (that is the factor for converting fluence rate to dose equivalent rate) given in subsequent appendices are cal-culated at the maxima in the depth-dose equivalent curves for normal irradiation. This procedure leads to a restrictive interpre-tation of the basic recommendations of the Commission, but it is appropriate in practical radiological protection. The values of effective quality factor given later

are also calculated for normal irradiation. When the maxima of absorbed dose and

dose equivalent occur at the same depth, the effective quality factor at this depth is obtained by dividing the maximum dose equivalent by the maximum absorbed dose. These maxima may occur at different depths, however, and the effective quality factor for any depth, such as that where the maximum dose equivalent occurs, must be obtained by dividing the value of the dose equivalent by the value of the absorbed dose at that depth.

A P P E N D I X 5

C O N V E R S I O N FACTORS FOR E L E C T R O N S

THE conversion factors for electrons recom-mended by the Commission are represented by the curve in Fig. 13 and are also given in Table 3; they refer to irradiation by a uni-directional broad beam of monoenergetic electrons at normal incidence and are evalu-ated at the maxima of the depth-dose equiva-lent curves. The quality factor for electrons is assumed to be unity. See Appendix 4 for a general discussion of conversion factors.

Above 100 MeV, these conversion factors have been obtained from the Monte Carlo calculations of Alsmiller and Moran (1968). More recently, similar computations have been reported by Beck (1970), who included the correction for density effect in the stop-ping power; the resulting decrease in the

stopping power produces a significant increase in the conversion factors derived. Although this refinement might be expected to improve the calculations, subsequent experimental studies by Svensson and Nelson (1970) fail to provide clear corroboration. Measurements of the energy absorption in a water phantom irradiated by 10 GeV electrons do show agreement with Beck's computations at small depths, but better agreement with the pre-dictions of Alsmiller and Moran at greater depths, an interpolated value of 1.6 electrons/ cm 2 . s per mrem/h at 30 cm depth being obtained from the experimental data. Since conversion factors are evaluated at the maximum dose equivalent in the body, the findings of Alsmiller and Moran seem more

T A B L E 3

C O N V E R S I O N F A C T O R S F O R E L E C T R O N S

Electron energy, Conversion factor*, MeV electrons/cm 2.s per mrem/h

1 χ ΙΟ" 1 1.6 2 x 1 0 - 1 2.6 5 x 1 0 - 1 3.9 1 χ 10° 4.8 2 χ 10° 5.5 5 χ 10° 6.2 1 χ 10 l 6.7 2 χ 10 1 7.2 5 χ 10 1 7.2 1 χ 10 2 6.7 2 χ 10 2 5.4 5 χ 10 2 3.6 1 χ 10 3 3.0 2 χ 10 3 2.5 5 χ 10 3 2.1 1 x 10 4 1.8 2 χ 10* 1.5

• Calculated at maximum of depth-dose equivalent curve.

10


appropriate; moreover, in the event of un-resolved discrepancies, it is cautious to use the more restrictive values. Previous, less elaborate, estimates by Tesch (1966) agree within 40% with those of Alsmiller and Moran.

From 100 MeV down to about 100 keV, below which energy the epidermis may not be penetrated, the conversion factors are obtained from calculations by Berger and Seltzer (1969) and Spencer (1959). As noted in Appendix 4, Berger and Seltzer consider broad beams normally incident on a semi-infinite water medium. Spencer considers a plane perpendicular source in infinite poly-

styrene, but his results can be applied to the case of broad beams injected into tissue. Experiments by McLaughlin and Hussmann (1969), Harder and Schulz (1972), and Rosenstein et al. (1972) indicate that the calculations have a satisfactory degree of accuracy.

It should be noted that the skin, the lenses of the eyes, and the testes, for which the Maximum Permissible Doses recommended by the Commission are 30, 15, and 5 rem in a year, successively set the limit to electron irradiation as electron energy is increased (Burlin and Wheatley, 1971).

A P P E N D I X 6

C O N V E R S I O N FACTORS AND EFFECTIVE QUALITY FACTORS FOR N E U T R O N S

THE conversion factors for neutrons recom-mended by the Commission are represented by the curve in Fig. 1 4 and are given in Table 4 ; they refer to irradiation by a unidirectional broad beam of monoenergetic neutrons at normal incidence and are evaluated at the maxima of the depth-dose equivalent curves. The recommended values of effective quality factor are represented by the curve in Fig. 1 5 and are also given in Table 4 , Q being

obtained by dividing the maximum dose equivalent by the absorbed dose at the depth where the maximum dose equivalent occurs.

Some published calculations of conversion factors and effective quality factors, upon which the recommended values are based, are plotted in Figs. 1 4 and 15 . Discretion has been used in drawing the curves so as to simplify the picture and facilitate the use of

T A B L E 4

C O N V E R S I O N F A C T O R S A N D E F F E C T I V E Q U A L I T Y F A C T O R S F O R N E U T R O N S

Neutron energy, MeV

Conversion factor*, neutrons/cm 2.s per mrem/h Effective quality factor 6, Q

2.5 x 1 0 " 8 (thermal) 260 2.3 1 χ ΙΟ" 7 240 2 1 χ i o - 6 220 2 1 χ 1 0 " 5 230 2

1 χ IO" 4 240 2 1 χ I O " 3 270 2 1 χ IO" 2 280 2 1 χ 1 0 " 1 48 7.4

5 χ IO" 1 14 11 1 8.5 10.6 2 7.0 9.3 5 6.8 7.8

10 6.8 6.8 20 6.5 6.0 50 6.1 5.0

1 χ 10 2 5.6 4.4

2 x 10 2 5.1 3.8 5 x 10 2 3.6 3.2 1 x 10 3 2.2 2.8 2 χ 10 3 1.6 2.6

3 x 10 3 1.4 2.5

Calculated at maximum of depth-dose equivalent curve. Maximum dose equivalent divided by the absorbed dose at the depth where the maximum dose equivalent occurs.

1 2


the data. Below 10 MeV, there is good agree-ment between the various calculations, but in the 10-100 MeV region, some discrepancies are in evidence. Differences in the nuclear models used in the calculations explain the discrepancy between the Irving et al. (1967) results and the others. Although insufficient experimental data are available at the time of writing to permit an objective choice, it seems most likely that the nuclear model used by Irving et al. yields a too cautious answer, and less weight is therefore given to their

data. Above 100 MeV, there is also good agreement between the calculations, and the curve has been drawn in an intermediate position compatible with the decision at lower energies.

The inherent limitations contained in the definitions of conversion factor and effective quality factor and the accuracy of the calcu-lations on which they are based should be firmly kept in mind when applying them. See Appendix 4 for a general discussion of these points.

A P P E N D I X 7

C O N V E R S I O N FACTORS A N D EFFECTIVE QUALITY FACTORS FOR P R O T O N S

THE conversion factors for protons recom-mended by the Commission are represented by the curve in Fig. 16 and are also given in Table 5; they refer to irradiation by a uni-directional broad beam of monoenergetic protons normally incident on a 30 cm thick phantom and are evaluated at the maxima of the depth-dose equivalent curves. The recom-mended values of effective quality factor are also presented in Table 5 , Q being obtained by dividing the maximum dose equivalent by the absorbed dose at the depth where the maximum dose equivalent occurs. See Appen-dix 4 for a general discussion of conversion

factors and effective quality factors and for a description of the phantom.

Below 200 MeV, the Bragg peak is devel-oped in the phantom; consequently, the conversion factor is constant down to 2 MeV, at which energy the epidermis may not be penetrated. Above 200 MeV, when the Bragg peak is not developed in the phantom, the conversion factor curve shows a sharp rise initially followed by a steady decline at higher energies.

Effective quality factors increase slowly from 1.4 at 60 MeV to 2.2 at 3 000 MeV.

T A B L E 5

C O N V E R S I O N F A C T O R S * A N D E F F E C T I V E Q U A L I T Y F A C T O R S F O R P R O T O N S

Proton energy, Conversion factor 6, MeV protons/cm 2.s per mrem/h Effective quality factor 0, Q

2 χ 10° to6 χ 10 1 0.40 1.4 1 x 10 2 0.41 1.4 1.5 x 10 2 0.42 1.4 2 χ 10 2 0.43 1.4 2.5 χ 10 2 2.1 1.4 3 x 10 2 2.4 1.5 4 x 10 2 2.5 1.6 6 χ 10 2 2.4 1.7 8 x 10 2 2.2 1.8 1 x 10 3 2.0 1.9 1.5 χ 10 3 1.6 2.0 2 χ 10 3 1.4 2.1 3 x 10 3 1.1 2.2

* For a 30 cm thick phantom. b Calculated at maximum of depth-dose equivalent curve. c Maximum dose equivalent divided by the absorbed dose at the depth where the

maximum dose equivalent occurs.

14

A P P E N D I X 8

C O N V E R S I O N FACTORS FOR P H O T O N S

THE conversion factors for photons recom-mended by the Commission are represented by the curve in Fig. 17 and are also given in Table 6; they refer to irradiation by a uni-directional broad beam of monoenergetic photons at normal incidence. The quality factor for photons is assumed to be unity. See Appendix 4 for a general discussion of conversion factors.

Below 10 MeV, the conversion factors are derived from 1.734 ~ E(peJp), where Ε is the photon energy, in MeV, and (μ^/ρ) the mass energy absorption coefficient for water, in m 2 /kg, quoted by Hubbell (1970) and also presented in Table 6.

Above 10 MeV, the data of Alsmiller and Moran (1968) have been used, the conversion

factors being evaluated at the maxima of the depth-dose equivalent curves. For the reasons given in Appendix 5, these data seem more appropriate than the results of more recent computations by Beck (1970).

It is sometimes convenient to know the photon energy fluence rate corresponding to 1 mrem/h. This may be obtained by multi-plying the values of the conversion factors in Table 6 or Fig. 17 by (1.6 χ 1 0 ~ 9 £ ) ; the energy fluence rate is then in J/m 2 .s .

It is also convenient to be able to relate photon fluence rate and exposure rate. This relationship, based on the mass energy absorption coefficients for air (Hubbell, 1970), is expressed in Fig. 18 for photons between 10 keV and 10 MeV.

15

REPORT OF COMMITTEE 3

T A B L E 6

C O N V E R S I O N F A C T O R S A N D M A S S E N E R G Y A B S O R P T I O N C O E F F I C I E N T S I N

W A T E R (μ β η/ρ) F O R P H O T O N S

Photon energy, MeV

Conversion factors, photons/cm 2 .s per mrem/h

Gzen//>) water, m 2 /kg

1 χ IO" 2 3.6 χ 10 2 4.79 x 1 0 " 1

1.5 χ IO" 2 9.0 χ 10 2 1.28 x 10" 1

2 χ 10~ 2 1.7 χ 10 3 5.12 x IO" 2

3 χ IO" 2 3.9 χ 10 3 1.49 x IO" 2

4 x 1Q- 2 6.4 χ 10 3 6.78 χ 1 0 " 3

5 Χ IO" 2 8.3 x 10 3 4.19 x I O " 3

6 x I O " 2 9.0 x 10 3 3.20 x 1 0 - 3

8 x IO" 2 8.3 x 10 3 2.62 x I O " 3

1 x IO" 1 6.8 x 10 3 2.56 x IO" 3

1.5 x IO" 1 4.2 x 10 3 2.77 x 1 0 " 3

2 x IO" 1 2.9 x 10 3 2.97 χ 1 0 - 3

3 x IO" 1 1.8 x 10 3 3.19 x I O " 3

4 x IO" 1 1.3 x 10 3 3.28 χ IO" 3

5 x I O ' 1 1.1 x 10 3 3.30 χ IO" 3

6 x IO" 1 8.8 χ 10 2 3.29 x IO" 3

8 x 1 0 " 1 6.8 χ 10 2 3.21 x IO" 3

1 χ 10° 5.6 χ 10 2 3.09 x I O " 3

1.5 χ 10° 4.1 χ 10 2 2.82 x I O " 3

2 x 10° 3.3 x 10 2 2.60 χ 1 0 " 3

3 x 10° 2.5 x 10 2 2.27 χ 1 0 " 3

4 x 10° - ' 2.1 x 10 2 2.06 χ 1 0 " 3

5 x 10° 1.8 χ 10 2 1.91 x I O " 3

6 χ 10° 1.6 χ 10 2 1.80 χ IO" 3

8 χ 10° 1.3 x 10 2 1.66 x IO" 3

1 χ ΙΟ1 1.1 x 10 2 1.57 χ IO" 3

1 χ ΙΟ 1 1.1 χ IO 2 1.55 x 1 0 - 3

2 χ ΙΟ1 6.4 χ IO1 1.36 x 1 0 - 3

3 χ 10 ι 4.4 χ IO1 1.31 x IO" 3

4 χ ΙΟ 1 3.4 χ IO1 1.28 x IO" 3

5 χ ΙΟ1 2.8 χ IO1 1.26 χ I O " 3

6 χ ΙΟ1 2.3 x IO 1 1.25 x 1 0 - 3

8 χ ΙΟ 1 1.7 χ IO 1 1.25 x I O " 3

1 χ ΙΟ 2 1.4 x IO 1 1.24 x I O " 3

2 χ ΙΟ 2 9.2 χ 10° 5 χ ΙΟ 2 5.8 x 10° 1 χ ΙΟ 3 4.9 χ 10° 2 χ ΙΟ 3 4.3 x 10°

5.2 χ ΙΟ 3 3.7 χ 10° 1 χ ΙΟ 4 3.4 χ 10° 2 χ ΙΟ 4 3.2 x 10°

16

A P P E N D I X 9

N E U T R O N S O U R C E S AND S H I E L D I N G

THIS Appendix deals mainly with the shielding requirements of accelerators for generating 14-15 MeV neutrons and of some radioactive neutron sources.

An accelerator or a radioactive neutron source produces a radiation field consisting, essentially, of primary neutrons, scattered neutrons of lower energies, and gamma rays generated by the interaction of the neutrons with the target, the capsule, the shield, and other objects. A radioactive source also emits primary gamma rays, and an accelerator may produce χ rays by backward acceleration of electrons into the ion source.

Several calculations of the shielding require-ments for neutron sources have been made. For a given source, the energy distribution of the neutrons is a complicated function of the

shield composition and thickness and of the irradiation geometry, so that various values of quality factor must be used for the calcu-lation of dose equivalent transmission. Furthermore, the shielding calculations are frequently based on different assumptions concerning, for example, the composition of the shield and the cross sections of its constituents; consequently, the calculated requirements show considerable disagree-ment. Careful measurements using reliable neutron dose equivalent rate detectors with appropriate energy dependence, for instance a counter of the Andersson-Braun type, are essential, therefore, for determining shielding requirements: such a counter will not, of course, measure the gamma-ray compo-nent.

A C C E L E R A T O R Ν

In the case of accelerators, where the energy of the bombarding particle does not exceed about 10 MeV, neutrons are generated mainly by nuclear reactions involving light elements. The maximum neutron energies which can be produced by these reactions are given in Table 7 (Brolley and Fowler, 1960). The most commonly used reaction is 3H(rf, >04He, shown in the last column; the deuteron energy is almost invariably chosen to give 14-15 MeV neutrons.

Experimental dose equivalent transmission data for 14-15 MeV neutrons are given in Figs. 19 and 20. The concrete data are due to Hacke (1967) and the other to Marshall and Knight (1971). Both sets of results are for diverging broad beams with the axes normal to the slab shields. Hacke's results are in good agreement with concrete data obtained by Marshall and Knight, and they also agree

U T R O N S O U R C E S

reasonably well with theoretical and experi-mental results obtained by several other authors. The marked increase in the rate of attenuation by the polyethylene of the com-bination shield arises from energy degradation of the neutrons in the steel.

Marshall and Knight also indicate that the absorbed dose due to transmitted gamma rays becomes important for large thicknesses of lightweight shields; for example, it begins to exceed the dose equivalent from transmitted neutrons at a water thickness of 120 cm. They also draw attention to the large amounts of neutron scattering in maze entrances to accelerator rooms. If the corner of a personnel maze is completely irradiated by 14-15 MeV neutrons, the neutron dose equivalent 1 m down the sheltered leg is about 25 % of the dose equivalent at the centre of the corner and then decreases approximately as the inverse


T A B L E 7

E N E R G Y O F N E U T R O N S P R O D U C E D B Y D I F F E R E N T N U C L E A R R E A C T I O N S I N V O L V I N G L I G H T N U C L E I

Target 1 2 C 3 H 7 Li 1 3 C 2 H 9 Be 3 H

Bombarding particle d Ρ Ρ α d α d

Energy of bombarding particle, MeV Neutron energy at 0°, MeV

0 2.07 2.45 5.27 14.05 1 0.69 — — 3.20 4.14 6.68 16.75 2 1.68 1.20 0.23 4.16 5.24 7.71 18.26 5 4.64 4.22 3.33 7.00 8.24 10.60 21.98

10 9.57 9.23 8.35 11.68 13.02 15.23 27.42

square of the distance from the centre of the corner.

14-15 MeV neutron generators with out-puts greater than 1 0 1 2 neutrons per second may induce excessive radioactivity in adjacent

materials, including shields made of ordinary concrete; but the use of calcium concrete, instead of ordinary concrete, reduces the radioactivity by an order of magnitude with-out significantly affecting attenuation.

R A D I O A C T I V E N E U T R O N S O U R C E S

The characteristics of some radioactive neutron sources are presented in Table 8, which is partly constructed from data in NCRP Report No: 23 (1960).

Sources of the (γ,η) type generally produce neutrons with energies below 1 MeV, and the gamma-ray shielding requirements normally exceed the neutron shielding requirements.

Sources based on the (α,/ι) reaction produce neutrons with energies up to 10 MeV approxi-mately; consequently, neutron shielding becomes important, especially when the gamma-ray outputs and energies are low, as in the case of 2 4 1 Am-Be. Several authors have reported on the neutron spectra of ( a ,« ) sources and on the relationship between

T A B L E 8

C H A R A C T E R I S T I C S O F S O M E R A D I O A C T I V E N E U T R O N S O U R C E S

Source Reaction Half-life Average neutron

energy, MeV Yield per Ci, neutrons/s*

2 1 0 P o - B e 2 2 6 R a - B e 2 3 8 Pu-Be 2 4 1 A m - B e

a,/f

α,/ι α,/f

α,Λ

138.4 d 1620 y

86.4 y 458 y

4.2 4.0 4.5 4.5

2.5 χ 10 6

1.3 χ 10 7

2.3 χ 10 6

2.2 χ 10 6

2 1 0 P o - B

1 2 *Sb-3e 2 5 2 C f

α,/ι

spontaneous fission

138.4 d

60d 2.65 y

1 0 B:6.3 " 8 : 4 . 5

0.024 2.35

fission spectrum

6.0 x 10 5 b

1.3 x 10 6 b - c

2.3 x 1 0 1 2

from lg*

• Compacted mixtures. b Relatively monoenergetic. c Radiochemical Centre (1971). Yield can be increased about four times by encasing source in beryllium. d Specific activity 532 Ci/g.


fluence and dose equivalent, especially for 2 4 1 A m - B e . Knight et al. (to be published) derive a mean value of 3.7 χ IO" 8 rem per neutron/cm 2 for 2 4 1 Am-Be sources. They also present experimental dose equivalent trans-mission data for broad beams of 2 4 1 A m - B e neutrons, and these are reproduced in Fig. 21. The slab results are for diverging beams with the axes normal to the shields.

2 5 2 C f produces neutrons by spontaneous fission. Details of the neutron and gamma-ray outputs of a 1 g source are given in Table 8 and in Tables 9 and 10 (Stoddard, 1965).

Experimental dose equivalent transmission data for diverging broad beams of 2 5 2 C f neutrons, with the axes normally incident on slab shields, are presented in Fig. 22 (Wright, 1968). Absorbed dose transmission data for

T A B L E 9

N E U T R O N F L U E N C E R A T E S A N D D O S E R A T E S 1 m F R O M 1 g 2 5 2 C f

Energy Fluence rate, Absorbed dose Dose equivalent interval, MeV neutrons/cm 2.s rate in tissue, rad/h rate, rem/h

0 - 0.5 2.2 χ 10 6 1.3 χ 10 l 1.1 χ 10 2

0.5 - 1.0 2.9 χ 10 6 3.5 χ 10 1 3.5 χ 10 2

1 . 0 - 2.0 6.1 χ 10 6 9.1 χ 10 1 8.5 χ 10 2

2 . 0 - 3.0 3.7 χ 10 6 5.9 χ 10 l 4.8 χ 10 2

3 . 0 - 4.0 2.2 x 10 6 3.7 χ 10 l 2.9 x 10 2

4 . 0 - 5.0 1.3 x 10 6 2.6 χ 10 l 1.7 χ 10 2

5 . 0 - 6.0 4.5 x 10 5 1.0 χ 10 l 6.3 x IO1

6 . 0 - 7.0 3.2 x 10 5 8.0 x 10° 4.8 χ 10 l

7 . 0 - 8.0 . 1.0 χ 10 5 2.5 x 10° 1.5 χ 10 l

8.0 - 10.0 7.9 x 10* 2.1 χ 10° 1.2 χ 10 l

10.0 - 13.0 1.8 x 10* 4.5 χ IO" 1 2.7 χ 10°

0 - 13.0 1.9 χ 10 7 2.8 χ 10 2 2.4 χ 10 3

T A B L E 10

P H O T O N F L U E N C E R A T E S A N D D O S E R A T E S 1 m F R O M 1 g 2 5 2 C f

Energy Fluence rate, Absorbed dose interval, MeV photons/cm 2.s rate in tissue, rad/h

0 - 0 . 5 3.7 X 10 7 1.7 X 10 l

0.5 - 1.0 4.5 X 10 7 6.1 X 10 l

1 . 0 - 1 . 5 1.4 X 10 7 3.0 X 10 l

1 . 5 - 2 . 0 6.1 X 10 6 1.6 X 10 l

2.0 - 2.5 1.8 X 10 6 5.8 X 10° 2.5 - 3.0 8.8 X 10 5 3.3 X 10° 3.0 - 3.5 4.5 X 10 5 1.9 X 10° 3.5 - 4.0 2.4 X 10 5 1.1 X 10°

4.0 - 4.5 1.4 X IO5 7.0 X IO" 1

4.5 - 5.0 6.5 X 10* 3.4 X ί ο - 1

5.0 - 5.5 3.9 X 10 4 2.3 X ί ο - 1

5.5 - 6.0 1.4 X 10 4 8.7 X IO" 2

6.0 - 6.5 8.0 X 10 3 5.3 X IO" 2

0 - 6 . 5 1.1 χ 10 8 1.4 x 10 2


2 5 2 C f gamma rays, calculated for diverging broad beams with axes normal to slab shields, are given in Fig. 23 (U.S.A.E.C. Report No. SRO-153, 1971). Figure 24 shows the calculated neutron dose equivalent rates at the surfaces of spherical shields with 1 /xg 2 5 2 C f at the centre of each sphere (Hootman, 1970; Stoddard and Hootman, 1971). Con-cretes 01 and 03 are ordinary concretes,

density 2.35 g/cm 3 , but concrete 01 contains about four times more hydrogen than concrete 03 because of higher water content. Full details of the concretes may be obtained from the preceding reference. For additional infor-mation on 2 5 2 C f sources and shielding, reference should be made to Nichols (1968), Prince (1969), and Oliver and Moore (1970).

T R A N S M I S S I O N O F O B L I Q U E L Y I N C I D E N T N E U T R O N B E A M S

The effect of a change in the angle of incidence on the absorbed dose transmission of unidirectional broad beams of mono-energetic neutrons through slab shields has been investigated theoretically by Allen and Futterer (1963). Results for 0.5, 1, 2, and 5 MeV neutrons are presented in Figs. 25-28 for water, polyethylene, and concrete, and details of the shield materials are given in Table 11. Although the calculations were done

for borated polyethylene, the results for pure polyethylene, density 0.93 g/cm 3 , differ negligibly.

In Figs. 25-28, neutron absorbed dose transmission is plotted against polyethylene thickness, and abscissa multiplication factors are provided for water and concrete. The angles of incidence are measured from the normals to the slabs, and the thicknesses are measured along the normals.

T A B L E 11

C O M P O S I T I O N O F M A T E R I A L S U S E D I N C A L C U L A T I O N S F O R F I G S . 25-28

Density, Elements Material g/cm 3 contained Atoms/cm 3 χ Ι Ο " 2 1

Borated polyethylene 0.97 Η 76.80 ( 8 % B 4 C b y weight) C 39.20

i o B 0.658 1 X B 2.67

Water 1.00 Η 66.90 Ο 33.45

Concrete 2.26 Η 13.75 Ο 45.87 Al 1.743 Si 20.15

O T H E R I N F O R M A T I O N

In some situations, soil may form pari of a neutron shield. Information on the shielding properties of various soils may be obtained from Allen and Futterer (1963) and Clark (1966).

Neutron shielding for similar sources is re-

viewed in NCRP Report No . 38 (1971), the emphasis being placed on theoretical methods; the Report also contains a copious list of references. For other information on neutron sources, spectra, and measurements, see ICRU Report 13 (1969).

A P P E N D I X 10

R A N G E - E N E R G Y CURVES

RANGE-ENERGY curves for electrons and pro-tons in air are presented in Fig. 29 and for electrons, protons, and alpha particles in water and lead in Figs. 30 and 31 respectively. The range shown is the continuous slowing down approximation range, Rcsda- The curves for electrons are obtained from Fano (1964), those for protons from Janni (1966), and those for alpha particles in lead from Williamson et al. (1966); the alpha particle curve in water is calculated by the method described in Fano (1964).

Rcsda for heavy particles is approximately equal to the mean' projected range, but

Rcsda for electrons significantly exceeds the extrapolated projected range. See ICRU Report 16 (1970) for a general discussion of the relationship between R c s d a and other ranges referred to in the literature.

Since the secondary radiations which may be produced are not considered in these curves, care must be taken when apply-ing the data in practical shielding calcula-tions.

The ranges are given in distance units and in density thickness units; the latter presenta-tion is useful for obtaining approximate thicknesses in other materials.

R . P . 21—-c

21

A P P E N D I X 11

S H I E L D I N G FOR BETA S O U R C E S

THE range-energy curves for electrons, given in Appendix 10, yield a cautious estimate of the shielding normally required for beta sources of activity less than a few millicuries, if a range corresponding to the maximum beta energy is used. With more active sources, bremsstrahlung produced by the deceleration of the beta particles may also need to be shielded.

Detailed calculations have been carried out to determine the quantity and energy spec-trum of external bremsstrahlung (Bethe and Heitler, 1934; Elwert, 1939), and these have been experimentally verified by, among others, Liden and Starfelt (1955). Simplifying assumptions have normally been used to determine shielding requirements (Wyard, 1952; Van Tuyl, 1961); and computer pro-grams have been developed which permit more precise estimates (Arnold, 1964) includ-ing the correction for internal bremsstrahlung (Van Tuyl, 1964).

Figure 32 shows the calculated bremsstrah-lung spectra from various beta sources in which the beta particles interact with the source material; the curves are constructed from the original histogram data (Arnold, 1964). Some characteristics of the sources are given in Table 12. The photon energy groups and emission rates selected for shielding cal-

culations from the 9 0 S r and 9 0 Y spectra in Fig. 32 are given in Table 13, and the result-ing absorbed dose transmission curves in three materials for diverging broad beams are presented in Fig. 33. The emission of gamma rays by a source, or the presence of other radionuclides as impurities, may affect shield-ing requirements.

All these data were calculated by Arnold for high-activity cylindrical sources, but in the case of 9 0 S r - 9 0 Y , comparison can be made with experimental data for conventional plaque sources (Haybittle, 1956-57; Nau-mann and Waechter, 1965). Good agreement exists for bremsstrahlung outputs, the experi-mental values being about 11 mR/Ci.h at 1 m and Arnold's about 13 mR/Ci.h at 1 m; and the transmission curves in lead accord. Both the outputs and the initial shape of the trans-mission curves are affected by the source structure, however, and bremsstrahlung cal-culations should be supported by measure-ments for the particular source.

Note that uranium itself emits radiation. The widely used depleted uranium, which differs from natural uranium only in having a lower 2 3 5 U content, has surface dose rates measured in air of about 200 mrad/h due to beta radiation and 2 mrad/h due to gamma radiation.

T A B L E 12

C H A R A C T E R I S T I C S O F T H E B E T A S O U R C E S C O N S I D E R E D I N A P P E N D I X 11

Maximum beta Average beta Total bremsstrahlung particle energy, particle energy, energy per beta pprticle,

Source MeV MeV MeV/beta Matrix

1 0 6 R h 3.54 1.515 1.29 χ 1 0 - 1 Metal 9 0 γ 2.27 0.944 2.81 χ 1 0 - 2 Oxide (Sr) 9 0 S r 0.545 0.201 1.41 χ IO" 3 Oxide

1 4 7 P m 0.23 0.067 2.02 χ 10"* Oxide 1 7 1 T m 0.097 0.029 3.13 x IO" 5 Oxide

22

PROTECTION AGAINST IONIZING RADIATION FROM EXTERNAL SOURCES

T A B L E 1 3

P H O T O N E N E R G Y G R O U P S A N D E M I S S I O N R A T E S

S E L E C T E D F O R T H E S H I E L D I N G C A L C U L A T I O N S F O R

B R E M S S T R A H L U N G F R O M 9 0 S r - 9 0 Y B E T A P A R T I C L E S

S T O P P E D I N T H E SrO M A T R I X

Photon energy, MeV

Photon emission rate, photons/Ci.s

0 . 2 5 1.3 χ 1 0 9

0 . 5 0 5.8 χ 1 0 8

0 . 8 0 1.8 χ 1 0 8

1 .10 5.5 x 1 0 7

1.40 1.5 x 1 0 7

1.70 2 .7 χ 1 0 6

2 . 0 0 1.9 χ 1 0 5

23

A P P E N D I X 12

X-RAY AND GAMMA-RAY S H I E L D I N G

DESIGNING shields against χ rays and gamma

rays is a very common radiation protection

task; consequently this Appendix is more

detailed than the previous ones. It contains a

substantial amount of output and trans-

mission data in graphical form, some

guidance on design procedures, tabulations

of shielding requirements for selected sources,

and a section on x-ray diagnostic installa-

tions.

T A B L E 14

O U T P U T S O F G A M M A - R A Y S O U R C E S *

Nuclide Half-life

Principal gamma-ray energies, in MeV, and per cent photons

per disintegration b

Exposure rate, R/h at 1 m from

1 Ci c

2 *Na 15.0 h γ: 1.37(100%) 2.75(100%)

1.84

6 0 C o 5.24 y γ: 1.17(100%) 1.33(100%)

1.30

1 2 4 S b 60d γ: 0.60 to 2.09 0.98

1 3 1 J 8.05 d γ: 0.08 to0.72 χ: 0.005(0.6%)

0.03 (5%)

0.22 (and 0.025 due

to x-rays)

1 3 7 C s 30 y γ: 0.66(85%) 0.32

1 8 2 T a 115d - γ: 0.07 to 1.23 0.60

1 9 2 j r 74 d γ: 0.30 to 0.61 0.48

1 9 8 A u 2.70 d γ: 0.41 to 1.09 χ: 0.009(1%)

0.07 (3%)

0.23 (and 0.014 due

to χ rays)

2 2 6 R a and daughters

1 620 y γ: 0.047 to 2.4 0.825 d

• Compiled by Duggan, from several references for the sources for which transmission data are provided in this Appendix.

b X-ray data are included where available. c Self-absorption in the source and absorption by air not taken into account. Bremsstrahlung generated in the

source also ignored. These remarks do not apply to 2 2 6 R a ; see note d. d Measured value assuming point source in 0.5 mm thick platinum capsule with units of R/h at 1 m from 1 g.

24


O U T P U T S O F X - R A Y G E N E R A T O R S

The outputs of x-ray generators, at a certain distance from the target, can be predicted with reasonable accuracy for a given potential, tube current, and beam filtration. The output is, however, a function of the type of generator and of the target material and configuration. When possible, therefore, the output of the generator of interest should be measured.

Typical outputs on the axes of the x-ray beams are shown in Figs. 34-37. The outputs of half-wave generators are approximately

one half the constant potential values. When calculating outputs for distances other than the ones shown, one may find it necessary to take air attenuation into account, especially at low potentials.

The references for Figs. 34-37 are as follows. Fig. 34: O'Riordan and Catt (1968). Fig. 35: Glasser et al. (1959). Fig. 36: Upper curve Wyckoff et al. (1948); centre curve Kaye and Binks (1940); lower curve Miller and Kennedy (1955). Figure 37: MacGregor (1959) and Murray (1964).

O U T P U T S O F G A M M A - R A Y S O U R C E S

The outputs of gamma-ray sources for data, the reader is referred to Nachtigall which transmission data are provided in this (1969). Appendix are given in Table 14. For other

T R A N S M I S S I O N O F P R I M A R Y X R A Y S A N D G A M M A R A Y S T H R O U G H S H I E L D S

Broad-beam transmission data for primary χ rays and gamma rays are presented in Figs. 38-52; the references and the irradiation geometries are given in Table 15. Trans-mission is in terms of exposure rate or absorbed dose rate measured in air.

The x-ray transmission charts are mostly for constant potential generators, but the data can be used for all types of generator without introducing serious discrepancies. Further-more, most of the x-ray curves are for negligibly small beam filtration; thus they are, in effect, dependent only on peak oper-ating potential. If it becomes necessary to make allowance for beam, filtration, Figs. 34-36 will be useful.

With regard to the gamma-ray trans-mission data, cognizance should be taken of the irradiation geometry for each nuclide and

shield, since the geometry affects the trans-mission. For nuclides other than the ones presented here, reference may be made to the manual prepared by Steigelmann (1963).

The concrete considered is made from natural aggregate and has a density of 2.35 g/cm 3 . Local variations from this value can usually be allowed for by applying a correction factor equal to the ratio of the densities. This procedure should not, however, be extended to markedly different aggregates, especially at low photon energies. See the section below on the shielding values of selected materials for low energy χ rays.

It is advisable to use low radioactivity building materials for shielding certain areas such as long-term stores for x-ray film and whole-body counting laboratories (Lindell and Riezenstein, 1964; Hamilton, 1971).


T A B L E 1 5

R E F E R E N C E S A N D I R R A D I A T I O N G E O M E T R I E S F O R X - R A Y A N D G A M M A - R A Y

T R A N S M I S S I O N D A T A

Radiations Shields Geometries**b Authors

10-50 kV steel, Perspex4, diverging broad beam O'Riordan and Catt (1969) 50-300 kV concrete diverging broad beam Trout et al. (1959) 400 kV concrete unidirectional broad beam Miller and Kennedy (1955)

50-200 kV lead diverging broad beam Binks(1943) 250 kV lead diverging broad beam Binks(1955)

300-400 kV lead unidirectional broad beam Miller and Kennedy (1955) 0.5-1 MV concrete, lead diverging broad beam Wyckoff *f a/. (1948)

2 M V concrete, lead narrow beam Evans etal. (1952) diverging broad beam Smith (unpublished)*1

3 MV concrete narrow beam Goldiee/a/.(1954) unidirectional broad beam O'Riordan (unpublished) 0

4 MV concrete diverging broad beam Greene and Massey (1961) 6-38 MV concrete diverging broad beam Kirn and Kennedy (1954) >38 MV concrete diverging broad beam Miller and Kennedy (1956) 4-30 MV lead diverging broad beam Maruyama et al. (1971)

2 4 N a lead cylindrical shield Price et al. (1957) uranium cylindrical shield Wright (1971)

6 0 C o concrete, steel diverging broad beam K e n n e d y s al. (1950) lead unidirectional broad beam Kirn etal. (1954)

uranium cylindrical shield Wright (1971) 1 2 4 S b concrete, lead point source, infinite medium Dealler (unpublished)* 1 3 1 ! concrete diverging broad beam Braestrup and Wyckoff (1958)

lead cylindrical shield West (1963) 1 3 7 C s .concrete, lead unidirectional broad beam Kirn etal. (\95A)

steel unidirectional broad beam O'Riordan (unpublished)*1

uranium cylindrical shield Wright (1971) 1 8 2 T a " lead cylindrical shield Price etal. (1957) 1 9 2 j r concrete, steel, lead diverging broad beam Ritz(1958)

uranium cylindrical shield Wright (1971) 1 9 8 A u concrete, lead unidirectional broad beam Kim et al. (1954) 2 2 6 R a concrete, steel, lead diverging broad beam Wyckoff and Kennedy (1949)

• For diverging broad beams, axes are normal to slab shields. b Unidirectional broad beams are normally incident on slab shields. c Polymethyl methacrylate ( C 5 H 8 0 2 ) « . Other trade names: Lucite, Plexiglass. a Data in unpublished references are calculated.

T R A N S M I S S I O N O F O B L I Q U E L Y I N C I D E N T B E A M S

Attention is drawn to the problem created

by the oblique incidence of beams on slab

shields (Kirn et al., 1954). Shielding estimated

on the basis of slant thickness using normal

incidence data must be increased to allow for

the accentuated transmission of scattered

photons. For example, if the required trans-

mission is 1 0 " 3 and the angle of incidence

45°, the increase required in concrete thick-

ness is about 20 % at low energies and 10 % at

high energies: the increase for lead, in

similar circumstances, is negligible. See

British Standard 4094 (1966) and NCRP

Report No . 34 (1970).


H A L F - V A L U E - T H I C K N E S S E S A N D T E N T H - V A L U E - T H I C K N E S S E S

Half-value-thicknesses (HVT) and tenth-value-thicknesses (TVT) for heavily attenu-ated broad beams of χ rays and gamma rays are presented in Tables 16 and 17, the values being obtained from the lowest decades of the transmission curves in Figs. 38-52.

Because of the shapes of many of the trans-mission curves, HVT and TVT cannot be used to calculate primary shielding requirements: they may be used, however, to calculate the shielding required for leakage radiation.

T A B L E 16

A P P R O X I M A T E H A L F - V A L U E - T H I C K N E S S E S A N D T E N T H - V A L U E - T H I C K N E S S E S

F O R H E A V I L Y A T T E N U A T E D B R O A D B E A M S O F X R A Y S

X-ray source

Half-value-thickness, cm Tenth-value-thickness, cm X-ray source Lead Concrete Lead Concrete

50 kV 0.005 0.4 0.018 1.3 70 — 1.0 — 3.6 75 0.015 — 0.050 —

100 0.025 1.6 0.084 5.5

125 1.9 6.4 150 0.029 2.2 0.096 7.0 200 0.042 2.6- 0.14 8.6 250 0.086 2.8 0.29 9.0

300 0.17 3.0 0.57 10.0 400 0.25 3.0 0.82 10.0 0.5 MV 0.31 3.6 1.03 11.9

1 0.76 4.6 2.52 15.0

2 1.15 6.1 3.90 20.1 3 — 6.9 — 22.6 4 1.48 8.4 4.9 27.4 6 1.54 10.2 5.1 33.8

10 1.69 11.7 5.6 38.6 20 1.63 13.7 5.4 45.7 30 1.57 13.7 5.2 45.7 38 — 13.7 — 45.7

T A B L E 17

A P P R O X I M A T E H A L F - V A L U E - T H I C K N E S S E S A N D T E N T H - V A L U E - T H I C K N E S S E S F O R H E A V I L Y

A T T E N U A T E D B R O A D B E A M S O F G A M M A R A Y S

\ M a t e r i a l \ M a t e r i a l Uranium, cm Lead, cm Steel, cm Concrete, cm

Nuclide \ \ HVT TVT HVT TVT HVT TVT HVT TVT

2 4 N a 0.9 3.0 1.7 5.6 _ 6 0 C o 0.7 2.2 1.2 4.0 2.0 6.7 6.1 20.3

1 2 4 S b — — 1.4 4.5 — — 7.0 23.0 1 3 1 ! — — 0.7 2.4 — — 4.6 15.3 l 3 7 C s 0.3 1.1 0.7 2.2 1.5 5.0 4.9 16.3 l 8 2 T a — — 1.2 4.0 1 9 2 I f 0.4 1.2 0.6 1.9 1.3 4.3 4.1 13.5 , 9 8 A u — — 1.1 3.6 — — 4.1 13.5 2 2 6 R a —~ 1.3 4.4 2.1 7.1 7.0 23.3


S H I E L D I N G V A L U E S O F S E L E C T E D M A T E R I A L S F O R L O W E N E R G Y X R A Y S

Because transmission depends sharply, at low photon energies, on the composition of the shield, it is necessary to know the shield-ing values of materials commonly used in x-ray installations. The traditional way of expressing these shielding values is to tabulate the lead equivalence of the materials as a function of thickness and x-ray generating

potential, and this is done, in Table 18, for clay brick, barytes aggregate concrete, and steel. The data relate to beam geometries between narrow and broad; consequently the shielding values are overestimated. Although determined with pulsating potential gener-ators, the tabulated data may also be used in the constant potential case.

T A B L E 1 8

L E A D E Q U I V A L E N C E O F V A R I O U S M A T E R I A L S F O R L O W E N E R G Y X R A Y S "

Material Material cm lead equivalent at applied kilovoltages of density, thickness,

Material g/cm 3 cm 50 75 100 150 200 250 300 400

Clay 1.6 10 0.06 0.08 0.09 0.08 0.08 0.10 0.11 0.13 brick b 20 0.14 0.17 0.19 0.17 0.17 0.23 0.30 0.45

30 0.22 0.27 0.31 0.26 0.26 0.40 0.55 0.85 40 — 0.38 0.45 0.37 0.37 0.60 0.83 1.27 50 — — — 0.48 0.48 0.81 1.13 1.71

Barytes 3.2 1.0 0.09 0.15 0.18 0.09 0.07 0.06 0.06 0.08 plaster or 2.0 0.18 0.27 0.33 0.18 0.14 0.13 0.14 0.16 concrete 5 2.5 0.23 0.33 0.40 0.22 0.17 0.17 0.18 0.20

5.0 — — — 0.43 0.34 0.36 0.39 0.43 7.5 — — — 0.59 0.50 0.56 0.61 0.68

10.0 — — — — 0.68 0.77 0.84 0.95 12.5 1.08 1.21

Steel c- d 7.8 0.1 0.01 0.02 0.01 0.01 —

0.2 — 0.03 0.03 0.02 0.02 — — — 0.3 — 0.05 0.05 0.03 0.03 — — — 0.4 — 0.07 0.07 0.04 0.04 — —. — 0.5 — 0.09 0.09 0.05 0.04 0.03 0.03 0.04

1.0 0.09 0.08 0.08 0.08 0.09 2.0 — — — 0.17 0.16 0.17 0.19 0.24 3.0 — — — 0.25 0.23 0.28 0.33 0.43 4.0 — — — 0.33 0.30 0.38 0.47 0.65 5.0 — — — 0.40 0.37 0.49 0.63 0.88

• See text regarding geometry. b Binks (1955) c Kaye et al (1938). d Trout and Gager (1950).


S C A T T E R I N G O F X R A Y S A N D G A M M A R A Y S

It is convenient here to refer to all photons emitted by an irradiated object as scatter radiation, although some of them are not due to Compton interactions.

There are two steps in designing a shield against scattered χ rays and gamma rays: firstly, it is necessary to determine the absorbed dose rate resulting from the scatter radiation; secondly, it is necessary to estimate the shield thickness required to reduce this scatter radiation to the acceptable level.

Figures 53 and 54 and Table 19 indicate the absorbed dose rate measured in air due to scatter in typical situations. Figure 53 shows the variation with accelerating poten-tial of χ rays scattered at 90° from various thick scatterers (Wachsmann et al., 1964). The beam is filtered so that its effective energy is about half the maximum photon energy; thus the figure may be used for gamma rays by reading from the curves the percentage scatter at the point corresponding to twice the gamma-ray energy. Note the dominating influence of the characteristic

radiation from lead at low potentials (Lindell, 1954). The scattering patterns of diverging x-ray and gamma-ray beams, normally incident on a thick concrete shield, are shown in Fig. 54. The references are: 100 to 300 kV Radiological Protection Service (unpublished); 6 0 C o , Dixon et al. (1952); 6 Μ V, Karzmark and Capone (1968). Table 19 indicates the amount of radiation scattered at various angles by patient-simulating phan-toms for 6 0 C o gamma rays and for χ rays generated at various potentials.

The percentage scatter varies with the irradiated area; there is an approximately linear relationship between these two para-meters for the field areas normally encoun-tered in medical and industrial radiology. The relationship may, however, lead to an overestimate of scatter for very large fields (British Standard 4094, 1971).

Two situations in which scatter radiation may present special difficulties should be noted (British Standard 4094, 1966 and 1971). * (1) Large amounts of scatter may be encoun-tered in maze entrances to radiation rooms.

T A B L E 19

P E R C E N T O F A B S O R B E D D O S E R A T E D U E T O I N C I D E N T R A D I A T I O N S C A T T E R E D T O

1 m B Y A T I S S U E - L I K E P H A N T O M F O R 400 c m 2 I R R A D I A T E D A R E A *

Angle of scatter 100 kV b 200 kV b 300 kV b 6 0 C o c 6 MV d

15° 0.65 30° 0.02 0.24 0.34 — 0.30 45° 0.03 0.23 0.26 0.18 0.14 60° 0.04 0.19 0.22 0.14 0.08

90° 0.05 0.14 0.19 0.07 0.04 120° 0.12 0.23 0.26 0.05 0.03 135° 0.17 0.30 0.33 0.04 0.03 150° 0.21 0.37 0.48 — —

Per cent scatter is related to primary beam measurements in free air at the point of reference, that is, at the same position as the phantom surface or phantom centre. Bomford and Burlin (1963). Cuboid phantom 30 cm wide χ 22 cm deep. Field area and angle of scatter referred to phantom surface. Dixon et al. (1952). Elliptic cylinder phantom 36 cm major axis, 20 cm minor axis. Field area and angle of scatter referred to phantom centre. Beam along major axis. Karzmark and Capone (1968). Cylinder phantom 27 cm diameter. Field area and angle of scatter referred to phantom centre.


If the corner of a personnel maze is com-pletely irradiated, the exposure rate 1 m down the sheltered leg is about 10% of the exposure rate at the centre of the corner, and it decreases approximately as the inverse square of the distance from the corner centre. (2) With open-top industrial radiography enclosures, scatter from the air and the superstructure of the workshop may exceed the quantity of radiation penetrating the walls of the enclosures. The following examples illustrate the situation by relating the quantity of scatter at head height outside a 3 m high enclosure to the source output, (a) In the case

of an uncollimated gamma-ray source, the external exposure rate is about 1 0 ~ 4 of the source output at 1 m. (b) In the case of 200-400 kV x-ray sets with 40° collimation: if the useful beam is directed upwards, the external exposure rate is about 5 χ 10" 5 of the out-put at 1 m; if the useful beam does not emerge from the enclosure, the external exposure rate is about 5 χ 10" 6 of the output at 1 m. Exposure rates around open-top enclosures are very dependent on the dimen-sions and construction of the enclosures and the workshops.

T R A N S M I S S I O N O F S C A T T E R 1

Figures 55 and 56 show the transmission through concrete and lead of 1 3 7 C s gamma rays scattered from an oblique concrete wall (Frantz and Wyckoff, 1959). Figures 57 and 58 show the transmission through concrete and lead of 6 0 C o gamma rays scattered from a patient-simulating phantom (Dixon et al.9

1952). Figure 59 shows the transmission through concrete of 6 MV χ rays scattered at various angles from a phantom (Karzmark and Capone, 1968). The foregoing refer to broad beams and are in terms of exposure or absorbed dose measured in air.

Where specific x-ray scatter data are not available, an approximate method, suggested by Braestrup and Wyckoff (1958), may be used. 90° scatter is identified as the principal component of scattered radiation in typical shielding situations, and its attenuation characteristics in three bands, below 0.5 MV, 0.5-3 MV, and above 3 MV are considered. Below 0.5 MV, 90° scatter radiation may be

^ D I A T I O N T H R O U G H S H I E L D S

assumed to have the same attenuation characteristics as the primary beam; conse-quently, the transmission data for the primary beam may be used to estimate the shielding required for scatter radiation. Trout and Kelley (1972) indicate the over-estimation inherent in this method at potentials up to 0.3 MV for lead shields: the overestimation is less for concrete. From 0.5.to 3 MV, the attenuation characteristics of 90° scatter are similar to those of a 0.5 MV primary beam (Mooney and O'Riordan, unpublished) so that the transmission data for 0.5 MV χ rays may be used. Above 3 MV, 90° scatter photons may be considered to have an energy of about 0.5 MeV, so that the 1 MV primary beam transmission data may be used in calculating shielding against scatter.

The method may be extended to gamma-ray sources by assuming that the generating potentials, in MV, are numerically twice the photon energies in MeV.

T R A N S M I S S I O N O F L E A K A G E R A D I A T I O N T H R O U G H S H I E L D S

It may be necessary to provide shielding exponential. Shielding against leakage radi-against leakage radiation from a tube or ation may therefore be estimated in terms of source housing. Since this radiation is the requisite number of half-value-thicknesses appreciably attenuated in passing through (HVT) or tenth-value-thicknesses (TVT) the housing, further attenuation is virtually using the values set down in Tables 16 and 17.


S H I E L D I N G F O R C O M B I N E D S C A T T E R A N D L E A K A G E R A D I A T I O N

It is usually necessary to determine the shielding required for scatter and leakage radiation combined. When calculations yield shield thicknesses for scatter and leakage radiation which differ by 1 TVT or more, the thicker shield should be adopted: if they differ by less than 1 TVT, however, the

thicker shield should be adopted and 1 HVT added. This approach saves effort, but in some situations it may be worthwhile to determine the requisite thickness more pre-cisely by repeated calculations, so that the transmitted radiation due to both effects is at the acceptable level.

S P E C I A L P R O B L E M S W I T H H I G H A N D V E R Y H I G H E N E R G Y E L E C T R O N A C C E L E R A T O R S

Attention is drawn to the special problems associated with high and very high energy electron accelerators operated in the electron and x-ray modes:

energy and intensity distributions of χ rays and electrons from an extracted electron beam;

radiation from unexpected locations in the event of accelerator malfunction;

production of neutrons and the relative importance of neutrons and χ rays;

activation of materials, such as accelerator parts and shields, and the possible creation of further external radiation hazards;

induced radioactivity in air and the pro-duction of noxious gases with the possible need for powerful ventilation;

radiation damage, especially to electronic components;

heating effects and the possible creation of fire and explosion hazards.

These problems cannot be treated here, but the following references contain useful data on the various aspects: NCRP Report No. 31 (1964); Less and Swallow (1964); Reetz and O'Brien (1968); Conf-691101; Stevenson (1969); Berger and Seltzer (1970); Bryn-jolfsson and Martin (1971); British Standard 4094 (1971); Baarli and Dutrannois (1971).

F O R M U L A E F O R D E S I G N I N G X-RAY A N D G A M M A - R A Y S H I E L D S

Formulae for designing x-ray and gamma-ray shields are presented here. Roentgens, rads in air, and rems are assumed to be numerically equal. The custom of considering a one-week period of use is followed.

For the primary beam, the maximum allowable transmission Β of a shield is given by:

Pd2

Β = WUT

(1)

Ρ is the weekly design limit, namely 0.1 rem/ week for areas occupied by supervised workers, 0.03 rem/week for areas occupied by non-supervised workers, and 0.01 rem/ week for areas occupied by members of the

public; all these values are derived from the annual Dose Limits for individuals under-going irradiation of the whole body, d is the distance in metres from the source to the location of interest. Wis the weekly workload, or amount of use of the source, expressed in mA.min/week for χ rays generated at poten-tials up to 3 MV, and in rad in air/week at 1 m or Λ/week at 1 m for other sources. U is the use factor, that is the fraction of the workload directed toward the location of interest, and Τ is the occupancy factor or fractional occupancy of that location; the employment of both factors should comply with local regulations. For χ rays up to 3 MV, equation (1) yields Β in units of R/mA.


min at 1 m: for all other sources, Β is trans-mission.

The shield thickness corresponding to the calculated value of Β is read from the appropriate transmission curve.

For scatter radiation, the maximum allow-able transmission Bs of a shield is given by:

Bs = (2) WTS v '

Ρ and Τ are the same as in equation (1). W also is the same, but if the source to scatterer distance is not 1 m, equation (2) must be modified according to the inverse square law; thus, if the source to scatterer distance is 50 cm, the denominator is multiplied by 4. S is the per cent of the incident absorbed dose rate or exposure rate scattered to 1 m for the irradiated area of interest; values of S may be derived from Figs. 53 and 54 and from Table 19. It is useful to note that a change in the source to scatterer distance is balanced by the resulting change in the irradiated area. When the approximate method mentioned in the foregoing section on the transmission of scatter is employed for high energy χ rays, S must be multiplied by the ratio of the output

at the potential of interest to that at 0.5 MV, namely 20 at 1 MV, 300 at 2 MV, and 850 at 3 MV. ds is the distance in metres from the scatterer, the source of radiation in this instance, to the location of interest. The units for Bs correspond to the units for Β in equation (1).

The shield thickness corresponding to the calculated value of Bs is read from the appropriate transmission chart.

For leakage radiation, the number of tenth-value-thicknesses NTVT corresponding to the maximum allowable transmission of a shield is given by:

W Τ JV T V T = l o g 1 0 ^ f i (3)

T, d, and Ρ are the same as in equation (1). WL is the weekly leakage exposure rate, or absorbed dose rate, at 1 m from the source. The number of half-value thicknesses NHVT

is 3.3 T V T V T -

The shield thickness corresponding to the calculated number of tenth-value-thicknesses or half-value-thicknesses is obtained by multiplying NTVT or NHVT by the values given in Tables 16 and 17.

S H I E L D I N G R E Q U I R E M E N T S F O R S E L E C T E D S O U R C E S

Examples of x-ray shielding requirements are given in Table 20 for primary beams and in Table 21 for scatter and leakage combined. The density of lead is 11.35 g/cm 3 and of concrete 2.35 g/cm 3 . The tables are con-structed directly from the information in this Appendix, but the 75 kV concrete data are based on interpolation.

In all cases, the weekly design limit is 0.1 rem. An indication of the shielding require-ments for 0.03 rem per week can be obtained by adding 0.5 TVT to the tabulated values, and for 0.01 rem per week by adding 1 TVT, but it is more accurate to use the formulae for these limits.

The potentials, workloads, and distances selected encompass the ranges of these para-meters in dental, veterinary, and medical diagnosis, in conventional therapy, and in the

bulk of industrial radiography. Use factors and occupancy factors may be incorporated in the effective workload column.

Table 21 is based on typical irradiation characteristics:

50 cm source to scatterer distance; 90° angle of scatter; 400 c m 2 irradiated area, implying 0.1 % of

the incident exposure rate scattered to 1 m;

100 mA.min/h maximum continuous tube rating at 50 and 75 kV, 200 mA.min/h at 100 and 150 kV, and 1 000 mA.min/h at 200-400 kV;

leakage radiation 0.1 R/h at 1 m from the target for 50-150 kV and 1 R/h at 1 m for 200-400 kV, at the maximum continuous tube ratings.


Both tables give the shielding requirements

for a single source of radiation. If more than

one source irradiates the location of interest,

or if individuals regularly move from one

irradiated location to another, the shielding

requirements for each source are increased so

that the total dose equivalent rate equals the

design limit.

T A B L E 20

P R I M A R Y X - R A Y B E A M S H I E L D I N G R E Q U I R E M E N T S F O R 0.1 rem P E R W E E K *

Potential, kV

Effective workload, mA.min per week b

cm lead required at source distances of

1 m 2 m 4 m 8 m

cm concrete required at source distances of

1 m 2 m 4 m 8 m

50

75

500 125 30

8

500 125 30

8

0.04 0.03 0.02 0.01

0.03 0.02 0.01 0.01

0.02 0.01 0.01 0.01 c

0.01 0.01 0.01 c

o d

3.4 2.5 1.6 0.9

2.5 1.6 0.9 0.4

0.10 0.08 0.05 0.03

0.08 0.05 0.03 0.02

0.05 0.03 0.02 0.01

0.03 0.02 0.01

0 d

9.7 7.4 5.0 3.0

7.4 5.0 3.0 1.2

1.6 0.9 0.4 QC.d

5.0 3.0 1.2 0.2

0.9 0.4 Q C d

0 d

3.0 1.2 0.2 0 d

100 1 000 250

60 16

0.24 0.19 0.14 0.09

0.19 0.14 0.09 0.05

0.14 0.09 0.05 0.03

0.09 0.05 0.03 0.01 c

17.0 13.6 10.4 7.1

13.6 10.4 7.1 4.1

10.4 7.1 4.1 1.5

7.1 4.1 1.5 QCd

150 1 000 250

60 16

0.30 0.25 0.19 0.14

0.25 0.19 0.14 0.09

0.19 0.14 0.09 0.05

0.14 0.09 0.05 0.02

25.5 21.1 16.8 12.3

21.1 16.8 12.3 8.0

16.8 12.3 8.0 4.0

12.3 8.0 4.0 0.8

200 40 000 10 000 2 500

625

0.66 0.58 0.51 0.43

0.58 0.51 0.43 0.35

0.51 0.43 0.35 0.28

0.43 0.35 0.28 0.20

46.3 41.0 35.9 30.6

41.0 35.9 30.6 25.4

35.9 30.6 25.4 20.1

30.6 25.4 20.1 15.0

259 40 000 10 000 2 500

625

1.26 1.09 0.91 0.74

1.09 0.91 0.74 0.59

0.91 0.74 0.59 0.44

0.74 0.59 0.44 0.31

51.8 46.5 41.0 35.4

46.5 41.0 35.4 29.8

41.0 35.4 29.8 24.1

35.4 29.8 24.1 18.6

300 40 000 10 000 2 500

625

2.38 2.04 1.70 1.36

2.04 1.70 1.36 1.04

1.70 1.36 1.04 0.76

1.36 1.04 0.76 0.52

58.4 52.5 46.3 40.2

52.5 46.3 40.2 34.0

46.3 40.2 34.0 27.8

40.2 34.0 27.8 21.9

400 40 000 10 000 2 500

625

4.05 3.49 3.02 2.50

3.49 3.02 2.50 2.02

3.02 2.50 2.02 1.54

2.50 2.02 1.54 1.12

65.0 59.0 53.0 46.8

59.0 53.0 46.8 40.6

53.0 46.8 40.6 34.4

46.8 40.6 34.4 28.5

* This table is constructed from the transmission data in Figs. 40-42. Air attenuation is not taken into account. b Shielding is calculated for the exact fraction of the initial workload required by the layout of each section of

the table. c The apparent inconsistency between the lead and concrete requirements is due to the use of transmission data

for a constant potential generator in the case of lead and a half-wave generator in the case of concrete. d May not apply if the total beam filtration is less than that specified for the transmission data in Fig. 40 or 41.


T A B L E 2 1

S C A T T E R A N D L E A K A G E X - R A Y S H I E L D I N G R E Q U I R E M E N T S F O R 0.1 rem P E R W E E K "

cm lead required at cm concrete required at source distances of source distances of

rôieniiai, tneciive worKioau. kV mA.min per week 5 1 m 2 m 4 m 8 m 1 m 2 m 4 m 8 m

50 500 0.02 0.01 0 0 1.0 0.3 0 0 125 0.01 0 0 0 0.3 0 0 0

75 500 0.06 0.02 0.01 0 3.1 1.1 0.1 0 125 0.02 0.01 0 0 1.1 0.1 0 0

30 0.01 0 0 0 0.1 0 0 0

100 1 000 0.08 0.04 0.02 0 5.5 2.7 0.3 0 250 0.04 0.02 0 0 2.7 0.3 0 0

60 0.02 0 0 0 0.3 0 0 0

150 1 000 0.11 0.06 0.03 0 8.9 4.9 1.3 0 250 0.06 0.03 0 0 4.9 1.3 0 0

60 0.03 0 0 0 1.3 0 0 0

200 40 000 0.40 0.32 0.24 0.16 26.9 21.6 16.4 11.3 10000 0.32 0.24 0.16 0.09 21.6 16.4 11.3 6.4 2 500 0.24 0.16 0.09 0.04 16.4 11.3 6.4 2.0

625 0.16 0.09 0.04 0 11.3 6.4 2.0 0

250 40 000 0.78 0.61 0.45 0.28 30.6 25.1 19.4 13.9 10 000 0.61 0.45 0.28 0.14 25.1 19.4 13.9 8.5 2 500 0.45 0.28 0.14 0.05 19.4 13.9 8.5 3.4

625 0.28 * 0.14 0.05 0 13.9 8.5 3.4 0

300 40 000 1.51 1.18 0.84 0.52 34.8 28.7 22.6 16.3 10 000 1.18 0.84 0.52 0.25 28.7 22.6 16.3 10.2 2 500 0.84 0.52 0.25 0.07 22.6 16.3 10.2 4.6

625 0.52 0.25 0.07 0 16.3 10.2 4.6 0

400 40 000 2.33 1.85 1.37 0.91 40.8 34.7 28.7 22.5 10000 1.85 1.37 0.91 0.54 34.7 28.7 22.5 16.2 2 500 1.37 0.91 0.54 0.23 28.7 22.5 16.2 9.6

625 0.91 0.54 0.23 0.02 22.5 16.2 9.6 1.5

a This table is based on the irradiation characteristics given in the text and is constructed from the transmission data in Figs. 40-42 and from Table 16. Air attenuation is not taken into account.

b Shielding is calculated for the exact fraction of the initial workload required by the layout of each section of the table.

X-RAY D I A G N O S T I C I N S T A L L A T I O N S

Exact shielding requirements for medical x-ray rooms can be obtained from the pre-ceding section. However, it may be advisable and eventually more economical to anticipate factors tending to increase shielding require-ments, that is, possible changes in equipment, in the amount and manner of its use, and in the degree and type of occupancy of sur-rounding areas, and to design the installation

accordingly. Such a prospective approach normally ensures that the dose equivalent to individuals is well below the design limit.

Where plans for large numbers of diag-nostic installations are routinely reviewed, it may be convenient to adopt certain thick-nesses as a shielding standard and to promul-gate these in the form of a simplified schedule as shown here.


Categorization should conform to national warning signs, shield marking, and operator or local regulations. Qualifications regarding protection may be added as appropriate, room size, film stores, shield discontinuities,

F O R M O F S T A N D A R D S H I E L D I N G S C H E D U L E F O R M E D I C A L X - R A Y R O O M S

Radiographic installations

Fluoroscopic installations

Categorization of surrounding areas

Radiographic installations floor and

ceiling Categorization of surrounding areas floor ceiling walls

floor and ceiling walls

1 2 3 4 etc.

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GENERAL S H I E L D I N G B I B L I O G R A P H Y AND I N F O R M A T I O N SERVICES

B L I Z A R D , E. P. and A B B O T T , L. S. (eds.) (1962) Reactor handbook. 2nd ed., Vol. I l l , Part B, Shielding. New York, Interscience.

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G O L D B E R G , M. D . , M A G U R N O , Β . Α . , M A Y , V. M., M U G H A B G H A B , S. F . , P U R O H I T , S. N., S T E H N , J. R., W I E N E R -

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—a review. Particle Accelerators, 2,77-104. P A T T E R S O N , H. W., T H O M A S , R. H., and W A L L A C E , R. (1972) Accelerator health physics. LBL-900. California,

Lawrence Berkeley Laboratory. P R I C E , Β . T., H O R T O N , C. C. and S P I N N E Y , Κ . T. (1957) Radiation shielding. London, Pergamon Press. R O C K W E L L , Τ., I l l (ed.) (1956) Reactor shielding design manual. 1st ed. Princeton, Van Nostrand.

S H I E L D I N G I N F O R M A T I O N S E R V I C E S

Radiation Shielding Information Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, U.S.A.

European Shielding Information Service, CCR Euratom, 21020 Ispra, Varese, Italy.

41

1 I^

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, 1

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F I G . 7 . Percentage depth-dose distributions in tissue-like material for beta particles from large plane sources virtually in contact with the material. (The maximum energies of the beta particles,

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F I G . 10. Average dose absorbed in the testes per unit exposure measured by a personal dosemeter on the front of the trunk (curves A and B) and per unit exposure measured in free air at the position of the centre of the body (curve C). Curve A: irradiation from the back only. Curve B: irradiation from the front only. Curve C: rotation during exposure simulating irradiation from all

sides.

ο 1 2

photon energy, MeV

F I G . 11. Average dose absorbed in the ovaries per unit exposure measured by a personal dose-meter on the front of the trunk (curves A and B) and per unit exposure measured in free air at the position of the centre of the body (curve C). Curve A : irradiation from the back only. Curve B : irradiation from the front only. Curve C: rotation during exposure simulating irradiation from

all sides.


10

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tion from all sides. R . P . 21—Ε

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ende

d I

-

• 4

- -/ II

-

j *

* 1 1

1

1

1

1

1

1

1 1

1 1

1 1

1 1

• 1

1 1

I

I I

Γ 1

j *

* 1 1

1

1

1

1

1

1

1 1

1 1

1 1

1 1

IO2

IO3

10

prot

on e

nerg

y, M

eV

FIG

. 16

. Con

vers

ion

fact

ors

for

prot

ons.

Uni

dire

ctio

nal

broa

d be

am,

norm

ally

inc

iden

t o

n a

30 c

m

thic

k p

han

tom

. T

he

curv

e in

dica

tes

the

valu

es r

ecom

men

ded

by t

he

Com

mis

sion

.

conversion factor, protons/emfs per mrem/h

OaiâiroaioJcn


1 I

ι I

l I

l Μ

ι I

I

I I

I I

I I

I I

I I

I I

I I

I I I

I

I I

I I

I I

I I IO

IO

IO

2 IO

3 IO

4 IO

5

phot

on e

nerg

y, M

eV

FIG

. 1

7. C

onve

rsio

n fa

ctor

s fo

r ph

oton

s.

Uni

dire

ctio

nal

broa

d be

am,

norm

al

inci

denc

e.

The

cu

rves

ind

icat

e th

e va

lues

rec

omm

ende

d by

the

Com

mis

sion

.

ι Ο

Ο

m

m

oo

IO"2

IO"'

1

10

II

I!

IO2

ι—ι—

ι τ

τη

. ^

IO3

10 10

conversion factor, photons/cm2s per mrem/h

ΙΑ

phot

on e

nerg

y, M

eV

FIG

. 18

. R

elat

ions

hip

betw

een

phot

on f

luen

ce r

ate

and

expo

sure

rat

e.

IO"2

10"1

1 10

I04r

photons/cm2s per mR/h

δ ill

ir>

2


F I G . 1 9 . Broad-beam dose equivalent transmission of 1 4 - 1 5 MeV neutrons through slabs of concrete, density 2 . 4 g/cm 3 , and water.


1

IO"1

IO"2 =

IO - 3

IO"4

i n - 5

dose

equ

ival

ent

tran

smis

sio

n

0 50 100 150

thickness, cm

F I G . 2 0 . Broad-beam dose equivalent transmission of 1 4 - 1 5 MeV neutrons through slabs of steel (density 7.8 g/cm 3) and polyethylene ( 0 . 9 4 g/cm 3) and a combination of steel and polyethylene.


1

i o - 1

dose

equ

ival

ent

tran

smis

sion

IO"2

IO - 3

0 IO 20 30 4 0 50 60 7 0

thickness, cm


thickness, cm

F I G . 21. Broad-beam dose equivalent transmission of 2 4 1 A m - B e neutrons through water and through polyethylene, density 0.94 g/cm 3 .

1

IO" 1;

: IO"2

I O - 3

dose

equ

ival

ent

tran

smis

sion

0 20 4 0 6 0


£sJ 1 1 1 1 1 1 1

\ polyethyleni

1 1 1 I

lead

1 I

ι ι ι ι 1 1 1 1 1 1 1 1 \ 1 1

0 1 0 2 0 3 0

thickness, cm

F I G . 22. Broad-beam dose equivalent transmission of 2 5 2 C f neutrons through slabs of lead (density 11.35 g/cm 3) and polyethylene (0.96 g/cm 3).

1 do

se

equi

vale

nt

tran

smis

sion

IO"1

i o - 2 L


thickness, cm

F I G . 2 3 . Broad-beam absorbed dose transmission of 2 5 2 C f gamma rays through slabs of lead (density 1 1 . 3 5 g/cm 3), steel ( 7 . 8 g/cm 3), and concrete ( 2 . 3 5 g/cm 3).

1

I O " 1 :

IO" 2:

10" 3

IO" 4 :

IO" 5

abso

rbed

dos

e tr

ansm

issi

on

10 20 30


radius, cm

F I G . 2 4 Neutron dose equivalent rates at the surfaces of spheres of polyethylene (density 0 . 9 6 g/cm 3), paraffin ( 0 . 9 2 g/cm 3), water, and concretes ( 2 . 3 5 g/cm 3), each with 1 /ig * " C f at its

centre.

65

IO 2

10

1 :

IO"1

IO"2

IO - 3

Ι0"4Ξ

IO - 5

I O - 6

neut

ron

dose

equ

ival

ent

rate

, m

rem

/h

per

μq

25

2C

f

0 20 4 0 60 80 I00 I20 I40


thickness, cm multiply scale by 1 for polyethylene, 1.07 for water, and 2.1 for concrete

F I G . 2 5 . Neutron absorbed dose transmission through slab shields of unidirectional broad beams of 0 . 5 MeV neutrons incident at various angles to the slabs.

66

1

IO"'

IO"2

IO"3

IO"4

IO - 5

IO"6

0 10 20 30

abso

rbed

d

ose

tr

ansm

issi

on

Ο 10 20 30

thickness, cm

m u l t i p l y scale by 1 for po lye thy lene , 1.07 for water and 1.7 for concrete

F I G . 26. Neutron absorbed dose transmission through slab shields of unidirectional broad beams of 1 MeV neutrons incident at various angles to the slabs.


1

Ίο-1

IO" 2

abso

rbed

dos

e tr

ansm

issi

on

I O - 3

IO" 4

•


thickness, cm

multiply scale by 1 for polyethylene, 1.16 for water, and 1.85 for concrete

F I G . 2 7 . Neutron absorbed dose transmission through slab shields of unidirectional broad beams of 2 MeV neutrons incident at various angles to the slabs.

1

I O - 1

IO" 2

abso

rbed

dos

e tr

ansm

issi

on

IO" 3 :

IO" 4

0 IO 20 30


thickness, cm

multiply scale by 1 for polyethylene, 1.21 for water, and 1.3 for concrete

F i g . 2 8 . Neutron absorbed dose transmission through slab shields of unidirectional broad beams of 5 MeV neutrons incident at various angles to the slabs.

1

IO" 1

abso

rbed

do

se t

ran

smis

sio

n

I O - 2 -

I O - 3

0 IO 20 30

REPORT OF COMMITTEE 3 7 0

IO6

IO5

IO4

IO3

IO2

10

1

I O " 1

rang

e in

air

, rn

g/c

m2

IO"2 IO"1 1 IO IO2 IO3

particle energy, MeV

F I G . 2 9 . Range of electrons and protons in air.

ιο4,

IO 3;

IO 2;

IO :

1 :

IO"1 :

IO" 2:

I O - 3 .

rang

e in

air

, m



F I G . 3 0 . Range of electrons, protons, and alpha particles in water.

R . P . 21—F*

IO6

IO5

IO4

IO3

IO2

10

1

IO"1

rang

e in

wat

er,

mg

/cm

2

I O - 2 IO"1 1 IO IO2 IO3

rang

e in

wat

er,

cm

10

\0'

IC

1

IO"1

IO"2

IO - 3

IO"4


»——

•—• 1

•••

•••

• ι

ι • •

• ι

1 •

ι ι ι

ι m

i- 1

1 I

MM

M-

1 1

I I I

I ι Μ

1

1 ,1

I II M

l 1

ι ι

ι ι ι

mi

Q-

*0

00

0

00

ran

ge

in l

ead

, m

g/c

m2

IO"2 IO~1 1 IO IO 2 IO 3


F I G . 3 1 . Range of electrons, protons, and alpha particles in lead.

IO 3

IO 2

10

1

IO"1

IO"2

IO"3

IO"4

rang

e in

lea

d,

mm


IO'1

I O ' 2 :

phot

ons/

beta

par

ticle

per

pho

ton

ener

gy i

nter

val

AE

(MeV

)

IO" 3:

IO' 4

10" 5

IO -' 1 5 IO"2

photon energy, MeV

F I G . 3 2 . Bremsstrahlung from I 0 6 R h beta particles stopped in the metal matrix; also from 9 0 Y . 9 0 Sr , l 4 7 P m , and 1 7 ^ m beta particles stopped in the oxide matrices.


10' , -1

10" r 2

C

"</)

ε (0 c σ

10 ,-3

I 0 " 5 b

10 rS

Κ 1 1 ' 1 1 1 1 1 1 1 1 1

1 1

1 1

1 II

I

III 1

1 ι ι

Γ

S,steel

-

1 1

1 1

1 1II

\ lead

II1 1 1 1

1 1 /

1 1

1 1

1 II

I

-

urar lium \

1 1

I 1

1 1

11

1 1

1 1

1 II

I

1 1 1 1 t 1 1 1 1 ! 1

10 15

thickness, cm

F I G . 3 3 . Absorbed dose transmission of diverging broad beams of bremsstrahlung f r o m 9 0 S r - 9 0 Y beta particles stopped in the oxide matrix through slabs of steel (density 7.8 g/cm 3), lead ( 1 1 . 3 5 g/cm 3), and uranium ( 1 8 . 9 g/cm 3). Beam axes normal to shields. See note in text regarding

uranium.

1

5


0 10 2 0 3 0 4 0 5 0

potential, kV

F I G . 34. Output of constant potential x-ray generator at 10 cm target distance for various beam filtrations and a tungsten reflection target. The 1 mm beryllium is the tube window. For output at

1 m, see Glasser et al. (1959).

I 0 4 i

I O 3

I O 2

10 j

1

IO" 1

IO" 2

R/m

A.

min

at

10 c

m


potential , kV

F I G . 35. Output of constant potential x-ray generator at 1 m target distance for various beam filtrations and a tungsten reflection target. The 1 mm beryllium is the tube window.

7 6

1 0 2 Ε

10

1

R/m

A.m

in

at 1

m

I O ' 1

I0"2l 5 0 I 0 0 I 5 0 2 0 0


potential, MV

10'

ε

ο

•1 10 < ε

10"

2 2

1 1

1 1

I 1

II

1 1 1 1 I 1 1 1 -

mplex

1 1

1 1

1 1

1 1

/ f i l ter

- /

0. 5 mm Ο,χι^,^1000*-

mm Cu

t i l l 1 1 1 1

1 1

1 1

1 1

1 1

2 0 0 3 0 0 4 0 0 5 0 0

potential, kV

F I G . 36. Output of constant potential x-ray generators at 1 m target distance for various beam nitrations. The upper curve is for a 2.8 mm tungsten transmission target followed by 2.8 mm copper, 18.7 mm water, and 2.1 mm brass. The other curves are for tungsten reflection targets

with 0.5 mm and 3 mm copper total filtration.

77

c

IO 3

1

potential, MV

F I G . 37. X-ray output of linear accelerators, per unit average beam current, 1 m from a high atomic number transmission target of optimum thickness. The ordinate is the absorbed dose rate measured in air. This chart may also be used for betatrons, although the target configuration

is different.


i'°4

1 IO 3

IO 2

IO

>2

IO' IO IO"2

1

IO"1

rad

in a

ir/y

Â.

min

at

1m

10 T " 3

10 kV 15 kV 20 kV

R/mA. min at 1 m mild steel, cm R/mA. min at 1 m mild steel, cm R/mA. min at 1 m mild steel, cm

2 . 2 x 1 0 ~ 1 0 3.2 χ 10""1 0 2.0 x 10° 0

6.6 χ 10""2 0.0013 2.5 χ 1 0 _ 1 0.0012 6 . 1 x 1 0 ~ 1 0.0014

2.2 χ 1 0 " 2 0.0030 8.2 χ 1 0 " 2 0.0028 2.0 χ 1 0 " 1 0.0031

6.6 χ 1 0 ~ 3 0.0054 2.5 χ 1 0 " 2 0.0048 6.1 χ 10~ 2 0.0055

2.2 χ 1 0 ~ 3 0.0076 8.2 χ 1 0 " 3 0.0070 2.0 χ 1 0 ~ 2 0.0081

6.6 χ 1 0 " 4 0.0102 2.5 χ 1 0 " 3 0.0093 6.1 χ 1 0 " 3 0.0114

2.2 χ 1 0 ~ 4 0.0126 8.2 χ 1 0 ~ 4 0.0116 2.0 χ 1 0 " 3 0.0146

2 . 2 x 1 0 ~ 5 0.0175 8.2 χ 1 0 " 5 0.0166 2.0 χ 1 0 ~ 4 0.0222

2.2 χ 1 0 " 6 0.0226 8.2 χ 1 0 " 6 0.0216 2.0 χ 1 0 " 5 0.0302

50 k V - d

0 O.I 0.2 0.3

mild steel, cm

F i g . 38. Broad-beam transmission of χ rays through mild steel, density 7.8 g/cm 3 . Constant poten-tial generator; tungsten reflection target; 1 mm beryllium total beam filtration. Ordinate intercepts

are: 8.38 at 50 kV; 6.58 at 40; 4.49 at 30.

1

IO"1

IO"2

IO"3:

ι O"4

IO"5

R/m

A.

min

at

1 m


perspex, cm FIG. 3 9 . Broad-beam transmission of χ rays through Perspex, density 1.2 g/cm 3 . Constant potential generator, tungsten reflection target; 1 mm beryllium total beam filtration. For ordinate intercepts,

see Fig. 3 8 .

8 0

10

1

IO"1

IO"2

I 0 _ 3 =

R/m

A.m

in a

t 1

m

I O ' 4 :

I O - 5

0 2 4 6 8


0 10 20 30 4 0 50 60 70

concrete, cm

F I G . 40. Broad-beam transmission of χ rays through concrete, density 2.35 g/cm 3 . 50 to 300 kV: half-wave generator; tungsten reflection target; total beam filtration 1 mm aluminium at 50 kV, 1.5 at 70,2 at 100, and 3 at 125 to 300.400 kV: constant potential generator; gold reflection target; 3 mm copper total beam filtration. Ordinate intercepts are 2.7 at 400 kV, 2.4 at 300, 1.6 at 250,

1.02 at 200, 0.6 at 150, 0.45 at 125, 0.32 at 100, 0.24 at 70, 0.19 at 50.

81

10 I

1

i o - 1

IO"2

R/m

A.m

in a

t 1

m

I 0 - 3 :

IO" 4:

IO" 5.


F I G . 41. Broad-beam transmission of χ rays through lead, density 11.35 g/cm 3 . Constant potential generator; tungsten reflection target; 2 mm aluminium total beam filtration. Ordinate intercepts

are 3.3 at 200 kV, 2.1 at 150, 1.1 at 100, 0.7 at 75, 0.3 at 50.

82

10

1

IO"1

R/m

A.m

in a

t 1m

IO"2

I 0 " 3 :

IO"4

I0"£

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

lead, cm


10

10"1

- 1 1 1 1 1 ! 1

i 1

1 1

1 1 1

!

-

- \ \

Ill 1 I

I 1

1

1 1

1 1

1 II

I

-

1 1

1 I

I II

I

250> 3 0 ( \ 4 0 C ) k v \ .

-

1 1

1 1

1 II

I

Λ I 1 *k 1 1

-

0 0 .4 0.8 1.2 1.6 2.0 2.4 2.8

lead, cm

F I G . 42. Broad-beam transmission of χ rays through lead, density 1 1 . 3 5 g/cm 3. 2 5 0 kV: constant potential generator; tungsten reflection target; 0 . 5 mm copper total beam filtration. 3 0 0 and 4 0 0 kV: constant potential generator; gold reflection target; 3 mm copper total beam filtration.

Ordinate intercepts are 2 .7 at 4 0 0 kV, 1.3 at 3 0 0 , 1.9 at 2 5 0 .

83

1

R/m

A.m

in a

t 1m

δ

ο

ο

ο

ι ι

ι ι

Ν

αϊ

^ m

ro


F I G . 43. Broad-beam transmission of χ rays through concrete, density 2.35 g/cm 3 . Constant potential generators. 0.5 and 1.0 MV: 2.8 mm tungsten transmission target followed by 2.8 mm copper, 18.7 mm water, and 2.1 mm brass beam filtration. 2 MV: high atomic number trans-mission target; 6.8 mm lead equivalent total beam filtration. 3 MV: gold transmission target; 11 mm lead equivalent total beam filtration. Ordinate intercepts are 850 at 3 MV, 300 at 2, 20 at 1,

1 at 0.5.

84

R/m

A.m

in a

t 1m

55

δ

δ

δ

—

5 5

δ

ι ι

ι ι

ι ro

οι

0 20 4 0 60 80 I00 I20 I40

concrete, cm


10'

10

10 - 1

= l I I I 1 1 1 1 I I I I I I I I I I I I

III! I I I

I

I I

Mil

l Mill I

I I

I I

I M

ill

Mill I

I I

^JJJjjjII

\ 1 \ Ο Μ ν

Mill I

I I

- \ \ I \ C IYI V

I I

I M

ill

- \ I

I ll

llll

1 1

1

1111

1

I I I I I I I I U f t I I I I I

ι ι

ι in

n

IO 15

lead, cm

20 25 30

F I G . 44. Broad-beam transmission of χ rays through lead, density 11.35 g/cm 3 . Constant potential generators. 0.5 and 1.0 MV: 2.8 mm tungsten transmission target followed by 2.8 mm copper, 18.7 mm water, and 2.1 mm brass beam filtration. 2 MV: high atomic number transmission target; 6.8 mm lead equivalent total beam filtration. Ordinate intercepts are 300 at 2 MV, 20 at 1, 1

at 0.5.

85

I 0 3

1

R/m

A. m

in a

t 1m

I0"2

I 0 " 3 :

I 0 " 4 E

IO"5

( 5 0


concrete, cm

F I G . 45. Broad-beam transmission of χ rays through concrete, density 2.35 g/cm 3 . 4 MV: linear accelerator; 1 mm gold target followed by 20 mm aluminium beam flattener. 6-38 MV: Betatron; target and filtration not stated. The 38 ΜV curve may be used up to 200 MV (Miller and Kennedy,

1956).

86

1

IO"1

IO""2

tran

smis

sion

IO" 3 :

Ι 0" 4 Ξ

I O - 5

IO" 6

0 50 100 150 2 0 0 250 3 0 0

FIG. 46. Broad-beam transmission of χ rays through lead, density 11.35 g/cm 3 . Betatron; platinum wire target 2 mm χ 8 mm; no beam filtration. For higher potentials, see Miller and Kennedy

(1956).

87 PROTECTION AGAINST IONIZING RADIATION FROM EXTERNAL SOURCES

1

IO" 1

IO" 2

IO" 3

tran

smis

sio

n

IO" 4

I0~ 5

I O - 6

0 4 8 12 16 2 0 2 4 2 8 3 2 3 6

lead, cm


1

IO - 1

IO" 2

I O " 3 :

tran

smis

sion

Ι 0 " 4

Ξ

I O - 5

I O - 6

Ο 25 50 75 100 125 150

concrete, cm

F I G . 47. Broad-beam transmission of gamma rays from various radionuclides through concrete, density 2.35 g/cm 3 .


1

IO" 1 :

IO"2

IO" 3

tran

smis

sio

n

IO" 4

I O - 5

I O - 6

Ο 25 50 75 100 125 150

concrete, cm

F I G . 48. Broad-beam transmission of gamma rays from various radionuclides through concrete, density 2.35 g/cm 3 .

R . P . 21—ο

Fio. 49. Broad-beam transmission of gamma rays from various radionuclides through steel, density 7.8 g/cm 3 .


1

IO - 1

IO"2

IO"3

tran

smis

sion

IO" 4

IO"5

IO" 6

W 1 1 • 1 ' 1 ' 1 1 1 1 1 1 1 ' 1 ' ' 1 1 1 1 '

Ο 5 10 15 20 25 30 steel, cm


1

IO"1

IO" 2 =

I O - 3

tran

smis

sion

IO" 4

IO" 5

I O - 6

0 5 10 15 20 25 30

lead, cm

F I G . 5 0 . Broad-beam transmission of gamma rays from various radionuclides through lead, density 1 1 . 3 5 g/cm 3 .


FIG. 51. Broad-beam transmission of gamma rays from various radionuclides through lead, density 11.35 g/cm 3 .

92

1

IO"1

IO"2

I O - 3

IO" 4

IO" 5

IO" 6

I

tran

smis

sio

n

0 5 ΙΟ 15 20 25 3 0

lead, cm


tran

smis

sio

n

5 10 15

uranium, cm FIG. 5 2 . Broad-beam transmission of gamma rays from various radionuclides through uranium,

density 18.9 g/cm 3. See note in the text of Appendix 11 regarding uranium.


• •

.11

1 1

1 I

II

l—U

0.01

0.

1 1

IO

I00

pote

ntia

l, M

V

FIG

. 53

. Var

iati

on w

ith

pote

ntia

l of

the

abs

orbe

d do

se r

ate

mea

sure

d in

air

due

to

χ ra

ys s

catt

ered

at

90°

fro

m

vari

ous

mat

eria

ls.

The

bea

m

is o

bliq

uely

in

cide

nt o

n th

e th

ick

scat

tere

r. P

er c

ent

scat

ter

is r

elat

ed t

o pr

imar

y be

am m

easu

rem

ents

in

free

air

at

the

poin

t of

inc

iden

ce.

% incident absorbed dose rate scattered to 50 cm per I00 cm

2 irradiated area

ο ο ο ρ ο ο

ι ι ι I I 1 ! 1 I 111!


F I G . 54. Scattering patterns of diverging x-ray and gamma-ray beams normally incident on a concrete shield. Per cent scatter is related to primary beam measurements in free air at the point

of incidence.

95

0.02-

%

inci

dent

ab

sorb

ed

dose

rat

e sc

atte

red

to 1

m p

er 1

00 c

m2 i

rrad

iate

d ar

ea

0.0I5

0.01 -

0.005 •

η 90 I20 I50 I80

scattering angle, degrees

0.08

- 0 . 0 6

0.04

0.02

0

1 κ

ΙΟ"1

ΙΟ" 2 :

tran

smis

sio

n

ΙΟ"3

ι ο - 4

Ο ΙΟ 20 30 4 0 50 60

concrete, cm

F I G . 55. Broad-beam transmission of 1 3 7 C s gamma rays scattered at various angles from an oblique concrete wall through concrete, density 2.35 g/cm 3 .


lead, cm

F I G . 56. Broad-beam transmission of 1 3 7 C s gamma rays scattered at various angles from an oblique concrete wall through lead, density 11.35 g/cm 3 .

97

1

ΙΟ"1

:

IO" 2

tran

smis

sion

IO - 3

IO" 4

Ο I.O 2.0 3.0

1

ΙΟ" 1

ΙΟ" 2

tran

smis

sio

n

Ι Ο - 3

ΙΟ"4

\\J I I I I I 1 I I I I I I I I ! I I I ι ι » ι I ' 1 ' LAJ I L-J Ο ΙΟ 2 0 3 0 4 0 5 0 6 0

concrete, cm

F I G . 57. Broad-beam transmission of 6 0 C o gamma rays scattered at various angles from a patient-simulating phantom through concrete, density 2.35 g/cm 3 .

F I G . 5 8 . Broad-beam transmission of 6 0 C o gamma rays scattered at various angles from a patient-simulating phantom through lead, density 1 1 . 3 5 g/cm 3 .


1

I O " 1 :

IO" 2

tran

smis

sion

I 0 _ 3 =

IO" 4

' ' I ' l l t ι ι ι ι ι ι ^ t ι ι

Ο 1.0 2.0 3.0

lead, cm

concrete, cm

F I G . 59. Broad-beam transmission of 6 M V χ rays scattered at various angles from a patient-simulating phantom through concrete, density 2.35 g/cm 3 .

1

!CT1

IO" 2 :

tran

smis

sion

I O - 3

i o - 4 0 50 I00 I50

OTHER ICRP PUBLICATIONS

Publication No. 5: The Handling and Disposal of Radioactive Materials in Hospitals and Medical Research Establishments.

Publication No. 7: Principles of Environmental Monitoring Related to the Handling of Radioactive Materials.

Publication No. 8: The Evaluation of Risks from Radiation.

Publication No. 9: Recommendations of the ICRP (Adopted September 17thf 1965).

Publication No. 10: Evaluation of Radiation Doses to Body Tissues from Internal Contamination due to Occupational Exposure.

Publication No. 10a: The Assessment of Internal Contamination Resulting from Recurrent or Prolonged Uptakes.

Publication No. 11: A Review of the Radiosensitivity of the Tissues in Bone.

Publication No. 12: General Principles of Monitoring for Radiation Protection of Workers.

Publication No. 13: Radiation Protection in Schools.

Publication No. 14: Radiosensitivity and Spatial Distribution of Dose.

Publication No. 15: Protection Against Ionizing Radiation from External Sources.

Publication No. 16: Protection of the Patient in X-ray Diagnosis.

Publication No. 17: Protection of the Patient in Radionuclide Investigations.

Publication No. 18: The RBE for High LET-Radiations with Respect to Mutagenesis.

Publication No. 19: The Metabolism of Compounds of Plutonium and other Actinides

Publication No. 20: Alkaline Earth Metabolism in Adult Man.

101

Date post:	11-Sep-2021
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Heat Flow Below 100°k and its Technical Applications. Proceedings of the International Institute of...

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