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Gamma Spectroscopy

HPT001.204Revision 1Page 1 of 81

NUCLEAR TRAININGTRAINING MATERIALS COVERSHEET

RADIOLOGICAL PROTECTION TECHNICIAN INITIAL TRAININGPROGRAMFUNDAMENTALS TRAINING HPT001COURSEGAMMA SPECTROSCOPY

COURSE NO.HPT001.204

LESSON TITLE LESSON PLAN NO.

INPO ACCREDITED YES X NO

MULTIPLE SITES AFFECTED YES X NO

PREPARED BYRalph G. Wallace/Brian K. Fike

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PROCESS REVIEW David L. Stewart

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LEAD INSTRUCTOR/PROGRAM MGR. REVIEWR. L. Coleman

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TVA 40385 [NP 6-2003] Page 1 of 2


NUCLEAR TRAININGREVISION/USAGE LOG

Rev. # Description of Changes Date Pages Affected Reviewed By

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1

Initial Issue

Program was inactive. Procedure Reviewed and completely revisedto update and reactive.

5/17/88 All

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TVA 40385 [NP 6-2003] Page 2 of 2


I. PROGRAM: Radiological Control (RADCON) Individualized Instruction

II. COURSE: Fundamentals Training

III. TITLE: Gamma Spectroscopy

IV. LENGTH OF LESSON: 16 hours

V. TRAINING OBJECTIVES

A. Terminal Objective

Upon completion of this module, participants will demonstrate knowledge and understanding of gamma spectroscopy by achieving a score of > 80% on a written examination.

B. Enabling Objectives

Standards and conditions apply to all enabling objectives. They include under the examination ground rules, without the use of training materials or outside assistance and utilizing information presented in this lesson plan.

1. State the characteristics of gamma rays and the purpose of gamma-ray spectroscopy.

2. Identify the most common technique for measuring photon energy.

3. Name the three basic mechanisms by which photons interact with matter and describe each mechanism.

4. Identify the energy range of each interaction mechanism.

5. Define the following:

a. Amplitude

b. Annihilation radiation

c. Backscatter peak

d. Bremsstrahlung

e. Characteristic X-Rays

f. Energy resolution


g. Full Width at Half Max (FWHM)

h. Multiplet

i. Photopeak

j. Summation effects/Sum peak

k. X-Ray escape peak

6. State the minimum energy necessary to cause pair production to take place.

7. State and define the unit of measurement for radiation energy.

8. Demonstrate familiarity with nuclide decay schemes.

9. Identify the primary material used in scintillation detectors and state the characteristics of the material.

10. Describe the basic components of a gamma spectroscopy system and tell the purpose of each.

11. Describe the two primary shapes of NaI(Tl) detectors.

12. Calculate the energy resolution from a gamma-ray spectrum.

13. Describe at least seven (7) of the features that can contribute to the gamma-ray spectrum.

14. Define detector efficiency and describe the difference between absolute efficiency and intrinsic efficiency.

15. Describe the two methods used to account for background and calculate the peak area under a spectrum curve.

16. Be able to use available references to identify the gamma-emitting radionuclides by their gamma spectrum.

17. Describe two types of materials used in late model gamma spectroscopy systems today.


VI. TRAINING AIDS

A. Whiteboard with markers.B. Networked computer and overhead projector.C. Graph paperD. Portable scintillation detectors (NaI, ZnS, as available).

VII. TRAINING MATERIALS :

A. Appendices

1. Handouts

a. HO-01 – Enabling Objectivesb. HO-02 – Obtaining Peak Areas from Multichannel Spectrac. HO-03 – Determining Peak Aread. HO-04 – I-131 + Background Spectrume. HO-05 – Background Spectrumf. HO-06 – Example Exerciseg. HO-07 – Gamma Ray Intensity with Corresponding Isotopesh. HO-08 – Example Exercise – Solutioni. HO-09 – Practical Exercise Problem # 1j. HO-10 – Practical Exercise Problem # 1 Solutionk. HO-11 – Practical Exercise Problem # 2l. HO-12 – Practical Exercise Problem # 2 Solutionm. HO-13 – Practical Exercise Problem # 3n. HO-14 – Practical Exercise Problem # 3 Solutiono. HO-15 – Practical Exercise Problem # 4p. HO-16 – Practical Exercise Problem # 4 Solutionq. HO-17 – Practical Exercise Problem # 5r. HO-18 – Practical Exercise Problem # 5 Solution

B. ATTACHMENTS

1. Power Point Transparencies, Slide show located at P\Training\Technical Programs and Services\Radcon\Initial Program\Lesson Plan Library\Power Point Files

a. TP-01 – Gamma Spectroscopyb. TP-02 – Enabling Objectives – 1c. TP-03 – Enabling Objectives – 2d. TP-04 – Enabling Objectives – 3e. TP-05 – Gamma Raysf. TP-06 – Cs-137 Gamma Energyg. TP-07 – Purpose of Gamma Ray Spectroscopy


h. TP-08 – Most Common Technique for Measuring Photon Energyi. TP-09 – Gamma Interactionsj. TP-10 – Interaction Processesk. TP-11 – Photoelectric Absorption (Diagram)l. TP-12 – Photoelectric Absorptionm. TP-13 – Compton Scattering (Diagram)n. TP-14 – Compton Scatteringo. TP-15 – Pair Production (Diagram)p. TP-16 – Pair Productionq. TP-17 – Electron Energyr. TP-18 – Electron Energy Equations. TP-19 – Wavelength of Photonst. TP-20 – Decay Schemesu. TP-21 – Cs-137 Decay Schemev. TP-22 – Co-60 Decay Schemew. TP-23– Scintillation Detectorsx. TP-24 – NaI(Tl)y. TP-25 – Gamma Ray Spectroscopyz. TP-26 – Photomultiplier (PM) Tubeaa. TP-27 – Crystal Shapesbb. TP-28 – Solid Crystal with Marinelli Beakercc. TP-29 – Solid and Well Crystalsdd. TP-30 – Components of a Gamma Spectroscopy Systemee. TP-31 – MCA Outputff. TP-32 – Gaussian Distributiongg. TP-33 – Ideal Gamma Ray Spectrumhh. TP-34 – Spectrumii. TP-35 – Energy Resolution – Diagramjj. TP-36 – The Gamma Spectrumkk. TP-37 – Energy Resolutionll. TP-38 – The Gamma Spectrum – Compton Scatteringmm. TP-39 – The Gamma Spectrum – X-Ray Escape Peaksnn. TP-40 – The Gamma Spectrum – Annihilation Radiationoo. TP-41 – The Gamma Spectrum – Bremsstrahlungpp. TP-42 – The Gamma Spectrum – Backscatterqq. TP-43 – The Gamma Spectrum – Characteristic X-Raysrr. TP-44 – The Gamma Spectrum – Summation Effectsss. TP-45 – Sum Peak, Sc-46tt. TP-46 – The Gamma Spectrum – Background Radiationuu. TP-47 – Potassium-40 Spectrumvv. TP-48 – Single Channel Analyzer Spectrumww. TP-49 – Components of a Gamma Spectrumxx. TP-50 – Spectrum with Componentsyy. TP-51 – Detector Efficiencyzz. TP-52 – Detector Efficiency – Solid Right Cylinderaaa. TP-53 – Detector Efficiency – Well Crystal


bbb. TP-54 – Detector Efficiency – Critical Dataccc. TP-55 – Peak Area Determinationddd. TP-56 – Peak Area Determination – Equationeee. TP-57 – Peak Area Determination – Background Subtractionfff. TP-58 – Background Subtraction – Spectrum Strippingggg. TP-59 – I-131 Spectrum, with Backgroundhhh. TP-60 – Background Spectrumiii. TP-61 – I-131 Spectrum – Background Subtractedjjj. TP-62 – Identifying Gamma Emitters – Unknown Spectrumkkk. TP-63 – Identifying Gamma Emitters – Solution Spectrum lll. TP-64 – Comparison of NaI(Tl) and GeLi Spectrammm. TP-65 – Other Detectors – Advantagesnnn. TP-66 – Other Detectors – Disadvantagesooo. TP-67 – Practical Exercises – Problem # 1ppp. TP-68 – Practical Exercises – Problem # 1 Solutionqqq. TP-69 – Practical Exercises – Problem # 2rrr. TP-70 – Practical Exercises – Problem # 2 Solutionsss. TP-71 – Practical Exercises – Problem # 3ttt. TP-72 – Practical Exercises – Problem # 3 Solutionuuu. TP-73 – Practical Exercises – Problem # 4vvv. TP-74 – Practical Exercises – Problem # 4 Solutionwww. TP-75 – Practical Exercises – Problem # 5xxx. TP-76 – Practical Exercises – Problem # 5 Solutionyyy. TP-77 – Summary – 1zzz. TP-78 – Summary – 2aaaa. TP-79 – Summary – 3bbbb. TP-80 – Summary - 4

VII. REFERENCES:

A. ACAD 93-008, “Guidelines for Training and Qualification of Radiological Protection Technicians,” National Academy For Nuclear Training, August 1993.

B. Basic Radiation Protection Technology, 2nd Edition, Daniel A. Gollnick, Pacific Radiation Corporation, Altadena, CA, 1988.

C. Radiological Health Handbook, U.S. Department of Health, Education, and Welfare, Public Health Service, Rockville, MD, 1970

D. The Health Physics and Radiological Health Handbook, Bernard Shleien, Editor, Scinta, Inc., Silver Spring, MD, 1992.


E. Scintillation Spectrometry, Gamma Ray Spectrum Catalogue, R. L Heath, γ-Ray Spectrometry Center, Idaho National Engineering and Environmental Laboratory, Idaho Falls, 2nd Edition, Electronic Update February 1997. Available on-line at: http://id.inel.gov/gamma/pdf/naicat.pdf, orhttp://wastenot.inel.gov/cgi-bin/byteserver.pl/gamma/pdf/naicat.pdf

F. Radiation Detection and Measurement, Glenn F. Knoll, John Wiley & Sons, New York, Second Edition, 1989.

G. P. Hofstadter, Phys Rev. 74, 100 (1948) (Referenced in Reference F)

H. NRC/NEU Exam Study Guide, NP-4, Particle Behavior/Gamma Interactions, at, http://www.nukeworker.com/study/hp/neu/index.shtml.

I. NRC/NEU Exam Study Guide, RP-3, Radiation Detection and Instrumentation, at, http://www.nukeworker.com/study/hp/neu/index.shtml.

J. The Southern Company, Farley Nuclear Plant Procedure RAD-30102B, Interactions with Matter, August 2001.

K. Least-Squares Resolution of Gamma-Ray Spectra in Environmental Samples, Larry G. Kanipe, Stephen K. Seale, and Walter S. Liggett, U. S. Environmental Protection Agency, EPA-600/7-77-089, Washington, DC, August 1977

L. Radioactive Decay Data Tables – A Handbook of Decay Data For Application to Radiation Dosimetry and Radiological Assessments, David C. Kocher, Publication DOE-TIC-11026, Technical Information Center, U. S. Department of Energy, Springfield, VA, 1981.

M. TVA Nuclear Training Lesson Plan HPT307.048, Isotopic Identification, January 2004.

N. Internal Dosimetry System Training, ABACOS II Body Burden System Operations (SU-419-3) Training Manual, Canberra Industries, Meriden, CT, August 1988.

O. http://www.drake.edu/artsci/physics/Gamma_Ray_Spectroscopy.pdf

P. http://www.phys.jyu.fi/research/gamma/publications/ptgthesis/node31.html

Q. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/ev.html

R. http://musr.physics.ubc.ca/~jess/hr/skept/E_M/node14.html

S. http://physicscourses.okstate.edu/flanders/phys3622/handouts/Gamma~ray~spectroscopy~and~absorption.pdf

http://physicscourses.okstate.edu/flanders/phys3622/handouts/Gamma~ray~%0Bspectroscopy~and~absorption.pdf

http://physicscourses.okstate.edu/flanders/phys3622/handouts/Gamma~ray~%0Bspectroscopy~and~absorption.pdf

http://musr.physics.ubc.ca/~jess/hr/skept/E_M/node14.html

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/ev.html

http://www.phys.jyu.fi/research/gamma/publications/ptgthesis/node31.html

http://www.drake.edu/artsci/physics/Gamma_Ray_Spectroscopy.pdf

http://www.nukeworker.com/study/hp/neu/index.shtml

http://www.nukeworker.com/study/hp/neu/index.shtml

http://id.inel.gov/gamma/pdf/naicat.pdf


T. http://www.home.earthlink.net/~prsteinm/gammaspec.html.

U. www.cs.jmu.edu/common/coursedocs/ ISAT301/Gamm-ray%20Spectroscopy.doc

V. Other web sites of potential interest:1. http://artemis.austincollege.edu/acad/physics/lrobin/gamma%20exp

%2098.pdf.2. http://www.acad.carleton.edu/curricular/PHYS/P128/lab/Gamma.pdf.3. http://www.oberlin.edu/faculty/yijiri/phy314/gammaray.pdf.4. http://www.shokabo.co.jp/sp_e/optical/labo/opt_cont/opt_cont.htm .5. http://cat.middlebury.edu/~PHManual/gamma.html 6. http://phys-advlab.physics.lsa.umich.edu/Phys441_442/Gamma-ray%20

Spect/gamma_ray_spectroscopy.pdf.7. http://www.phys.ufl.edu/courses/phy4803L/gamma/gamma.html .8. http://www.physics.isu.edu/radinf/

http://www.physics.isu.edu/radinf/

http://www.phys.ufl.edu/courses/phy4803L/gamma/gamma.html

http://phys-advlab.physics.lsa.umich.edu/Phys441_442/Gamma-ray%20

http://cat.middlebury.edu/~PHManual/gamma.html

http://www.shokabo.co.jp/sp_e/optical/labo/opt_cont/opt_cont.htm

http://www.home.earthlink.net/~prsteinm/gammaspec.html


IX INTRODUCTION:

Gamma rays are forms of electromagnetic radiation like light and X-rays. Gamma rays originate in atoms and result from transitions of the nucleus from a higher to a lower energy state. The energy difference is a fixed value for a given isotope of a nuclide so that the gamma rays from a specific radionuclide will all have the same characteristic energy which can be used to signal the presence of that particular radionuclide in a substance.

Handout # 01

Objective 1TP-01TP-02TP-03TP-04TP-05

Reference B

TP-06

The purpose of spectroscopy is to measure the energy and number of photons. In order to do this, we must detect the presence of photons in a way that allows us to differentiate one photon from another based on the energy of the photon. In the infrared, visible, ultraviolet and low-energy X-ray regions of the electromagnetic spectrum, this is usually accomplished with a diffraction grating that uses the wave length of the light to disperse the photons according to their wavelength. For visible light, a prism may also be used.

Objective 1

TP-07

Reference O

These techniques will not work with higher energy X-rays and gamma rays; therefore, other methods must be used. The most common technique for measuring photon energy employs a scintillating material coupled with a detector. When a high-energy photon interacts with a scintillating material, the photon’s energy is converted to visible light. The intensity of the light produced is proportional to the energy of the original photon.

TP-08

Objective 2

Reference O

Since X-rays and gamma photons are uncharged and create no direct ionization or excitation of the materials through which they pass, in order to measure these photons we must cause the photons to undergo an interaction that transfers all or part of the photon energy to an electron in the absorbing medium. These electrons have a maximum energy equal to the energy of the incident photon and will slow down and lose their energy in the same manner as other fast electrons, such as a beta particle.

Reference F


You will recall that gamma photons and X-rays interact with matter in three basic mechanisms: photoelectric absorption, Compton scattering, and pair production. The relative importance of these three modes of interaction to the absorption process is a function of the atomic number of the absorber (Z) and the energy of the incident gamma ray. Photoelectric absorption predominates for low-energy gamma rays (up to several hundred KeV), pair production predominates for high-energy gamma rays (above 5-10 MeV) and Compton scattering is the most probable process over the range of energies between these extremes. Before we consider the measurement of photons by spectroscopy, let’s review these three mechanisms.

Objective 3TP-09

Reference K

TP-10

Objective 4


X. LESSON BODY INSTRUCTOR NOTES

A. Definitions Objective 5

1. Amplitude – The extent of a vibrating movement (as of a pendulum) measured from the mean position to an extreme, or the maximum departure of the value of an alternating current or wave from the average value.

2. Annihilation radiation – The radiation resulting when a positron from beta positive decay comes to rest. It encounters an electron, and they annihilate each other and convert their rest mass into two 0.511-MeV gamma rays emitted in exactly opposite directions.

3. Backscatter peak – Radiation which passes completely through the crystal without interaction and which then interacts by Compton scattering in the shielding or parts of the detecting equipment, and is scattered through 180o back into the crystal where it is detected.

4. Bremsstrahlung – German for braking radiation, is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. The term is also used to refer to the process of producing the radiation. Bremsstrahlung has a continuous spectrum.

5. Characteristic X-Rays – Characteristic X-rays are produced in an inner-shell ionization process when the incoming electron collides with the atom and ejects one of the atom's inner-shell (K shell) electrons. The excited atom then can emit a characteristic (K) x-ray as it returns to the stable state.

6. Energy resolution – For a given detector, the energy resolution is defined as the full width half maximum FWHM of the pulse height distribution, divided by the centroid, expressed as a percentage.

7. Full Width at Half Max (FWHM) – The width of the distribution at a level that is half the maximum value of the peak

http://www.amershamhealth.com/medcyclopaedia/medical/Volume%20I/full%20width%20%20%20half%20maximum%20%20FWHM%20.html

http://www.amershamhealth.com/medcyclopaedia/medical/Volume%20I/full%20width%20%20%20half%20maximum%20%20FWHM%20.html

http://www.amershamhealth.com/medcyclopaedia/medical/Volume%20I/detector.html

http://en.wikipedia.org/wiki/Spectroscopy

http://en.wikipedia.org/wiki/Atomic_nucleus

http://en.wikipedia.org/wiki/Electron

http://en.wikipedia.org/wiki/Electromagnetic_radiation

http://en.wikipedia.org/wiki/German_language


X. LESSON BODY INSTRUCTOR NOTES8. Multiplet – A spectral line having more than one

component, representing slight variations in the energy states characteristic of an atom, as in overlapping peaks in a spectrum.

9. Photopeak – Peak photon energy in a spectrum of gamma rays radiated from a radionuclide. The primary photopeak is the peak which results from the total absorption of the energy in the scintillation detector.

10. Summation effects/Sum peak – In some cases an isotope emits multiple gamma rays in its decay. If these photons are close enough together the detector identifies them as a single event. This phenomenon is known as the summation effect and a sum peak will be registered in the spectrum at a pulse height that corresponds to the sum of the two individual photon energies.

11. X-Ray escape peak – the peak resulting from the photoelectric effect in the detector and escape, from the sensitive part of the detector, of the X-ray photon emitted as a result of the photoelectric effect.

http://www.amershamhealth.com/medcyclopaedia/Volume%20I/radionuclide.html



B. Photon interaction with matter.

1. Photoelectric absorption

In the process of photoelectric absorption an incident photon is completely absorbed by an atom in the absorber material, and one of the atomic electrons (usually a tightly bound electron from the K or L shell) is ejected. This ejected electron is known as a photoelectron. The electron must be bound to the atom to conserve energy and momentum. The vacancy left in the atomic structure by the ejected electron is filled by one of the electrons from a higher shell. This transition is accompanied by an emission of an X-ray. These X-rays are also absorbed by the detector. Photoelectric absorption is the predominant mode of interaction for gamma rays or X-rays of relatively low energy (≤200 keV). The interaction is again dependent upon the atomic number (Z) of the absorber.

Reference P

Objective 3

TP-11

Reference B

TP-12

Objective 4

The effect of photoelectric absorption is the liberation of a photoelectron, which carries off most of the photon energy, together with one or more low-energy electrons. If nothing escapes from the detector, the sum of the kinetic energies of the electrons that are created must equal the original energy of the gamma-ray photon.

Reference F

2. Compton Scattering TP-13

Compton scattering or Compton effect is the process whereby an x-ray or gamma ray collides with a single loosely bound electron. The result is that the essentially free electron is ejected from its parent atom and the incident photon is scattered and now possesses a lower energy.

Reference B


X. LESSON BODY INSTRUCTOR NOTESThe Compton effect is important for gamma-ray energies between 200 kev and 5 Mev in most light elements. The Compton effect decreases with increasing gamma energy, but not as quickly as the photoelectric effect. An important feature of Compton scattering is that a photon is still in existence after the scattering collision has taken place.

Objective 4, TP-14

References J & P

In normal circumstances, all scattering angles will occur in the detector; therefore, a continuum of energies can be transferred to the electron, ranging from zero up to the maximum predicted by the scattering equation. The calculated energy is a function of the scattering angle and the original energy of the incident photon. For example, for Cesium-137, the gamma ray has an energy of 662 keV and the maximum electron energy is 478 keV.

References F & O

3. Pair production References B & O

If the incident gamma ray has enough energy (>1.022 MeV) when it passes close to a nucleus, it may interact with the nucleus and create an electron-positron pair. Since the rest mass energy of an electron (or a positron) is 0.511 MeV, it takes at least 1.022 MeV to supply the necessary energy. In fact, in an absorber such as tissue, pair production accounts for less than 10% of the interactions for photon energies up to 5 MeV. In general, this type of interaction is not observed for photons having energies less than about 2.5 Mev. Any energy in the gamma ray beyond 1.022 MeV ends up in the kinetic energy of the electron and positron and the nucleus which must also move to conserve momentum. The positron will eventually collide with another electron and annihilate producing two gamma rays of 0.511 MeV each (the equivalent energy to the Annihilation mass of each particle). These will then interact via photoelectric effect or Compton effect.

TP-15

Objective 6

TP-16

Ask how these secondary photons will interact.(Photoelectric absorption or Compton effect)


X. LESSON BODY INSTRUCTOR NOTESC. Measuring photons and photon energy

We have looked at the ways in which photons interact with matter. Now let’s consider how we can use this information to measure amount and type of radioactive material producing the photons.

1. Gamma emitting radionuclides References F, R, & Q

a. The traditional unit for the measurement of radiation energy is the electron volt, or eV. The electron volt is defined as the energy given to an electron by accelerating it through 1 volt of electric potential difference. One electron volt (1 eV) = 1.602 * 10-19 joules (J). (Electric charge is usually measured in coulombs, abbreviated C, and a volt is a J/C).

Objective 7, TP-17

The multiples of kiloelectron volt (keV) and megaelectron volt (MeV) are the more common forms used in measuring the energies for ionizing radiation.

The energy of an X- or gamma-ray photon is related to the radiation frequency by:

E = h ν, where,

E = Energy, in eVh = Planck’s constant (4.135 * 10-15 eV-s)ν = frequency, s-1;

Reference F

TP-18

Stress that units of frequency are inverse seconds or 1/s; the “-1” does NOT affect the outcome mathematically.

And the wavelength, λ, is related to the photon energy by:

λ = (1.24 * 10-6)/E where

λ is in meters and E in eV.

TP-19

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elevol.html#c1


X. LESSON BODY INSTRUCTOR NOTESb. Gamma radiation is emitted by excited nuclei in

their transition to lower nuclear levels. In many radionuclides, the excited nuclear states are created when a parent radionuclide decays. Let’s consider the decay of the 2 common radionuclides, cesium-137 and cobalt-60.

Reference F

TP-20

Objective 8

TP-21In both examples, the decay of the parent by the emission of an electron (beta particle) leads to the population of the excited state in the daughter nucleus.

The beta decay in these radioisotopes is a relatively slow process as indicated by half-lives on the order of 30 and 5 years, respectively; however, the excited states in the daughter nuclei have a much shorter average lifetime, typically on the order of picoseconds or less.

As these unstable states strive to reach stability, they release a gamma-ray photon whose energy is essentially equal to the difference in energy between the initial and final energy states. The gamma rays appear with a half-life characteristic of the parent beta half-life, but with an energy that reflects the energy level structure of the daughter nucleus.

Note transparency 21. Although the Cs-137 gamma ray is emitted with the 30 year half-life characteristic of Cs-137, the photons actually arise from the transitions in the barium-137 nucleus.

Note that the energy of the gamma ray, 662 keV, is the difference between the energy of the excited state, 662 keV, and the energy of the stable state, 0 keV.

Reference E


X. LESSON BODY INSTRUCTOR NOTESNow note the Co-60 decay as shown in transparency 22. The energy of the first gamma ray is the difference between the energies of the two excited states (2505.8 keV less 1332.5 = 1173.3 keV) and the energy of the second photon is equal to the difference between the energy of this lower excited state and energy of the stable state (1332.5 keV minus 0 keV = 1332.5 keV). Similar decay schemes for most other gamma emitting radionuclides can be found in reference E as well as other documents.

TP-22

Since these unstable nuclear states have very well-defined energies, the energies of photons emitted in the state-to-state transitions are also very specific. The gamma rays from any single transition are almost monoenergetic.

2. Scintillation Detectors

a. If a material gives off light when radiation interacts with it, it is said to scintillate. The amount of light given off is proportional to the amount of incident radiation. This light can be measured and the information used to calculate the intensity of the radiation emitted.

Reference I

Different types of scintillating material are used to detect different types of radiation. For example, a thin layer of zinc sulfide is generally used to detect alpha radiation; an anthracene crystal is used for beta.

TP-23

b. In 1948 Robert Hofstadter first demonstrated that crystalline sodium iodide, in which a trace of thallium iodide had been added, produced an exceptionally large scintillation output compared with other materials which had been used. This discovery ushered in the era of modern scintillation spectroscopy of gamma radiation.

References F & G

Objective 9


X. LESSON BODY INSTRUCTOR NOTESNaI(Tl) is hygroscopic and will absorb water and deteriorate if exposed to the atmosphere for any length of time; therefore, the crystals must be sealed in an air-tight container for normal use.

Objective 9 (Cont’d)

The most important characteristic of NaI(Tl) is its excellent light yield. Its response to electrons (and gamma rays) is close to linear over most of the significant energy range.

TP-24

Gamma photons interact with the crystal in several ways to produce energetic electrons. The electrons ionize some of the atoms in the crystal. When molecules of sodium iodide (NaI) are ionized, the electron ejected is not energetic enough to be a free electron. The exciton, as it is called, leaves its original orbital position, but does not leave the atom itself. The energy of the exciton is eventually imparted to the activating material (thallium, in the case of a NaI (TI) crystal), raising certain atoms of the material to an excited state. These excited atoms then radiate this energy in the form of light. This entire interaction, from the time a gamma photon enters the crystal until the light is emitted, takes place in a fraction of a microsecond.

c. Now that we have the light pulse generated, the next step is to detect or analyze the pulse. We detect light in this wavelength region using a photocathode. This is a device with a light-sensitive material that emits electrons when struck by light. In other words, it is a photoelectric device that generates electrons in response to being struck by a photon.

Reference O

Objective 10


X. LESSON BODY INSTRUCTOR NOTESThe preferred packaging technique is to use an aluminum cylinder with an aluminum cap at one end to form a close-fitting “cup.” The inside is then coated with a white reflective paint, or more recently, dry MgO powder packed around the surfaces of the crystal, to increase light output. The NaI(Tl) crystal is machined to fit snugly inside the container and a glass or quartz window is sealed over the open end and a photomultiplier tube (PM tube) cemented to the entrance window. The purpose of the PM tube is to amplify the weak light pulses into a large electrical signal.

TP-25

Reference B

Transparency 26 demonstrates the operation of the photomultiplier tube. Since it is difficult to detect a single electron, we need to increase the number of electrons generated by a single photon. To accomplish this, a series of metal plates called dynodes is arranged in such a way that when an electron strikes the first dynode, it has enough energy to kick several electrons out of that material. These electrons are then accelerated toward another dynode where each electron can again kick out several more. Each dynode has to be at more positive voltage than its predecessor so that the electrons are continually accelerated. This multiplying effect produces a total gain of about 106.

TP-26

Reference O

The output of a scintillation detector is a pulse of electrons that is proportional to the energy of the original radiation interacting with the scintillating material. The electrons are detected at the anode or final dynode as a current flowing through a resistor. Voltage is supplied to each dynode in turn from a voltage divider chain of resistors in the base of the PM tube.

Reference I

d. Two general shapes of sodium iodide crystals are in widespread use today.

Objective 11, TP-27

Reference F


X. LESSON BODY INSTRUCTOR NOTES(1) The solid right circular cylinder is the

most common crystal in use. The height-to-diameter ratio is generally around 1, with dimensions typically 2, 3, or 4 inches in height and 2, 3, or 4 inches, respectively, in diameter. The light collection properties are quite favorable in this geometry. This type of detector is commonly used in whole body counters and to count samples that can be placed on or around the detector.

TP-28

(2) A well crystal is a right circular cylinder into which a cylindrical well has been machined into the crystal. The well is drilled along the cylindrical axis of the crystal. In this configuration a much higher counting efficiency can be achieved by placing the sample to be counted into the well. Almost all of the gamma rays emitted from the source are intercepted by at least a portion of the detector crystal. For low-energy photons, the counting efficiency can approach 100%. For higher energy photons, some of this advantage is lost because more of the photons will pass through the detector without interacting with it. Well crystals provide very similar counting geometries resulting in more uniform counting efficiencies. They are commonly used to analyze low activity samples such as air filters or samples of environmental media.

TP-29

3. The gamma spectrum

a. We now have a current pulse with a height that is proportional to the energy of the incident gamma ray. This pulse is now sent to an amplifier, or series of amplifiers, where it is amplified and shaped to a steady output voltage proportional to the peak input voltage.

Reference S

TP-30


X. LESSON BODY INSTRUCTOR NOTESThe pulse is next sent to an analog-to-digital converter (ADC) where it is converted into a number. The number generated by the ADC is once again proportional to the energy deposited in the crystal. These numbers are forwarded to the analyzer where they are deposited into energy bins or channels.

There are two basic types of analyzers; single channel analyzers (SCAs) and multi-channel analyzers (MCAs). We will first consider the multi-channel analyzer.

b. The number of “channels” will vary depending on the capabilities of the MCA, but will typically be a multiple of 256 (256, 512, 1024, 2048, etc.). Each channel will represent a gamma energy level. The system is calibrated using a known radioactive source to determine the number of counts (proportional to the gamma ray intensity) versus the channel number (proportional to the gamma ray energy). After we have analyzed a string of voltage pulses (arising from the gamma rays hitting the scintillator), we have a set of memory locations (channels) that contain the number of pulses at a particular voltage. This is the gamma ray spectrum.

TP-31

The numbers observed correlate with sample activity while the amplitudes reflect gamma energy. Measured amplitudes are directly proportional to energy deposited in the detector. The pulse height peak that results from the largest light pulse is called the photopeak. Because the photopeak is directly proportional to the energy, we can use it to identify a radionuclide. If everything were perfect we would always get a perfect Gaussian curve. The Gaussian feature in this spectrum represents the full energy of the interacting gamma rays.

TP-32


X. LESSON BODY INSTRUCTOR NOTESc. In a perfect world we would expect that all of

the pulses generated from a monoenergetic photon to appear in one channel, so that our spectrum would be a vertical line when plotted. This is not the case, however. There are a number of phenomena that interfere with this perfect expectation.

References F & O

TP-33

(1) Rather than a sharp, narrow peak to represent the photon energy, the measured response is more of a blurred effect due primarily to the ability of the detector system to place the pulse in the precise channel.

References F & T

TP-34

As a result, all the peaks have some finite width rather than appearing as a vertical line. This distribution of the energy spectrum is called the response function of the detector. The performance of the detector is defined by its ability to resolve this blur of energies.

In transparency 35, the distribution of the pulses is assumed to include only the radiations from a single energy source. The full width at half maximum (FWHM) is defined as the width of the distribution at a level that is half the maximum value of the peak. This assumes that the background or ‘noise pulses’ has been subtracted away.

TP-35



The energy resolution, R, of a detector is defined as the FWHM divided by the location of the peak centroid.

TP-36

Reference F

R = (FWHM * 100)/Ho

Where:

R = Energy Resolution

FWHM = Full Width Half Max, Mev or keV

Ho = Location of the peak centroid, MeV or keV.

Objective 12

Error Prevention Tools:Self-Checking – Ensure that FWHM and Ho have the same units.

The energy resolution is therefore a dimensionless fraction expressed in percentage. From this figure, if we assume that the FWHM is 50 keV and the photon energy is 662 keV, then R = 0.0755 or 7.55 %.

Calculate the energy resolution from the hypothetical data given.

TP-37

The smaller the energy resolution, the better the detector will be able to distinguish between two radiations whose energies are near each other. The energy resolution of Sodium Iodide scintillation detectors generally ranges from 5 to 10 %.

Reference F

(2) The result of Compton scattering is the creation of recoil electrons and scattered gamma-ray photons, with the energy being divided between the two dependent on the scattering angle. In normal circumstances, all scattering angles will occur in the detector, producing a continuum of energies that can be transferred to the electron, ranging from zero up to the maximum energy. This Compton continuum overlaps the lower part of the spectrum and hinders identification of some of the peaks.

Reference F

TP-38

Reference M


X. LESSON BODY INSTRUCTOR NOTES(3) If the detector is relatively small relative to

the typical secondary electron range, a significant portion of the electrons may escape from the detector and their energy will not be detected. This secondary electron escape will tend to shift the response curve by moving the events to a lower amplitude from which they would have originally been collected.

(4) In some cases, if the photoelectric absorption process occurs near the surface of the detector, the characteristic X-ray emitted by the absorber atom may escape from the detector. When this occurs, the energy deposited in the detector is decreased by the amount equal to the X-ray photon energy. A new energy level is then created with an energy equal to the difference between the photopeak energy and the energy of the X-ray.

TP-39

These peaks are called X-ray escape peaks, and are usually most prominent at low incident gamma-ray energies.

(5) If the source decays by positron emission, an additional peak is introduced into the spectrum at 0.511 MeV when the annihilation photons created when the positron combines with an electron. This peak, referred to as annihilation radiation is superimposed on the spectrum generated from the decay of the source.

TP-40

(6) Since most gamma-ray sources decay by beta-minus emissions, some secondary bremsstrahlung radiation will be generated. The bremsstrahlung spectrum may extend to an energy equal to the maximum beta energy, but significant yields are confined to energies that are much lower than this value.

TP-41

Ask what type of detector material would exacerbate this problem.

(High Z material)


X. LESSON BODY INSTRUCTOR NOTESThe bremsstrahlung spectrum does not typically lead to peaks in the spectra, but adds to the continuum. This can lead to errors in the quantification of measurements under the peaks.

(7) When gamma-rays interact by Compton scattering in one of the materials surrounding the detector (such as a shield in which the detector is housed), a portion of these scattered gamma-rays are backscattered into the detector and contribute to the spectrum. These backscatter peaks usually occur at energies of 0.25 MeV or less.

TP-42

(8) Photoelectric absorption in materials used to shield the detector can result in the generation of characteristic X-rays that may be absorbed by the detector.

If the shielding is made from materials with a high atomic number, the X-ray photon will be relatively energetic and can penetrate the detector container and contribute to the measured spectrum.

Therefore, many detector shields are made of graded material in which the bulk of the shield is made from high-Z material, but the inner surface is lined with a material with a lower atomic number, like copper. This inner lining serves to absorb the characteristic X-rays emitted from the bulk of the shield.

TP-43

(9) Another phenomenon that can contribute additional peaks to the spectrum is referred to as the summation effect. This typically occurs when an isotope emits multiple gamma rays in its decay.

References F & K

TP-44

TP-45


X. LESSON BODY INSTRUCTOR NOTESIn some of these cases, the lifetime of the intermediate energy state is so short that the two gamma rays are sometimes emitted so closely together that the detector identifies them as a single event.

If enough of these events occur, a sum peak will be registered in the spectrum at a pulse height that corresponds to the sum of the two individual photon energies. One of the more common nuclides in which this can occur is Co-60.

(10) A final complicating factor that we will consider is background interference.Since gamma rays are very penetrating, many background sources are capable of impacting the analysis of low level power plant samples.

Reference M

TP-46

Background signal sources may be categorized as: Terrestrial Cosmic Laboratory

(a) As a rule, long-lived naturally occurring background sources are considered separately from shorter lived, man-made ones. In this respect, terrestrial background consists primarily of isotopes of the naturally occurring heavy element decay chains. Small levels of such isotopes are present in all materials available for the construction of detector system components and shielding.


X. LESSON BODY INSTRUCTOR NOTESCommon examples of such background isotopes include: Ac-228, Ra-224, Bi-212, Pb-212, Tl-208, Ra-226, Pb-214 and Bi-214 all of which occur as daughters of the thorium and uranium decay series. In addition to these heavier isotopes, K-40 (E = 1.460 MeV) can be an important natural background contributor.

TP-47

Included as terrestrial background, although actually man-made, are fission products resulting from early atmospheric nuclear weapons testing. Such products include as: Zr-95, Nb-95, Ru-106, Sb-125, Cs-137, Ce-144. Sr-90 also falls into this category, but it emits a beta only with no gamma.

These materials can be imbedded in shielding materials fabricated after atmospheric weapons testing. If this is a problem, pre-weapons testing materials should be used for shielding. These materials, which are available in TVA, include steel from decommissioned navy ships annealed prior to weapons testing.

(b) Background classified as cosmic is due to high energy photons and particles such as muons, mesons, electrons, protons and neutrons. Interaction of such cosmic radiation with detector system components can produce low level noise. Extraterrestrial in origin, cosmic background is effectively reduced by proper shielding design.


X. LESSON BODY INSTRUCTOR NOTES(c) Background classified as laboratory

includes all source, sample and contamination related activity. Examples include natural thorium in certain glasses, plant samples contaminated through poor technique and shielding related gamma ray sources.

d. Single channel analyzers

(1) This type of analyzer involves the use of two independent discrimination levels. The analyzer produces an output pulse only if the input pulse amplitude lies between the two levels.

(a) A lower-level discriminator (LLD) sets the minimum pulse amplitude that will produce an output pulse to the analyzer.

Error Prevention Tools:Self-Checking and/or Peer Checking -

(b) An upper-level discriminator (ULD) sets the maximum pulse amplitude that will produce an output pulse to the analyzer.

Ensure the LLD and ULD levels are set properly.

(2) The SCA can then select only a limited range of amplitudes from all those generated by the detector. This will allow the operator to establish a ‘window’ to correspond only to those events in the detector which deposit the full energy of an incident radiation (for example, the photopeak).

TP-48

(3) In this way, one type or energy of radiation often can be measured selectively in the presence of other radiations.


X. LESSON BODY INSTRUCTOR NOTES(4) This technique is prescribed in TVA’s

Radiological Emergency Plan for the analysis samples in the field during emergency events. The LLD and ULD are set on either side of the I-131 photopeak area so that the output of the analyzer represents the count rate in the portion of the spectrum attributable to I-131.

4. Analyzing the gamma spectrum

a. Components of the spectrum

As noted earlier, the gamma ray spectrum consists of several components. Let’s briefly review some of the features which may be found in many spectra.

Reference KObjective 13TP-49

Briefly review the list from TP-49, then point out the features on TP-50.

(1) The primary photopeak is the peak which results from the total absorption of the energy in the scintillation detector. It is the most important feature of the spectrum because its amplitude and intensity are direct measures of the energy and intensity of the incident gamma photon.

TP-50

The width of the photopeak reflects the energy resolution of the spectroscopy system and the fraction of the total counts in the photopeak is a function of the detector volume.

Therefore, the photopeak is used to qualify and quantify the nuclides in the source.

A spectrum may contain more that one photopeak, either because the isotope produces more than one photon, or because there is more than one nuclide in the sample. If these peaks overlap, they are called multiplets.


X. LESSON BODY INSTRUCTOR NOTES(2) A backscatter peak results from the 180

degree backscatter during the Compton interaction. These peaks are typically found between 200 and 250 keV.

(3) The Compton continuum stretches essentially from zero to the maximum energy value indicated as the Compton edge.

Reference N

(4) The Compton edge is found at the energy of the photopeak minus the energy of the backscatter peak.

(5) If positron-electron annihilation occurs outside the detector, an annihilation photon of 0.511 MeV can penetrate the detector. This can add a small peak, the annihilation peak, in the spectrum at 0.511 MeV.

(6) Escape peaks are produced by the repeated escape of a discrete amount of energy from the detector. The most common escape peak arises from pair production and is associated with annihilation radiation.

When one annihilation photon does escape repeatedly, a second peak will appear in the spectrum at an energy 0.511 MeV less than that of the photopeak.

If both annihilation photons escape the detector, another escape peak will occur at an energy of 1.022 MeV less than that of the photopeak.

(7) If more that one photon enters the detector simultaneously, the PM tube will consider the event as a single light pulse. Repeated occurrence of this type of event will result in the production of a sum peak at an energy level equal to the sum of the individual photon energies.


X. LESSON BODY INSTRUCTOR NOTES(8) Two non-gamma components that frequently

appear in the spectra are bremsstrahlung and X-rays. Bremsstrahlung radiation is emitted when an electron decelerates while moving away from the strong, attractive electric field of the nucleus. X-ray contributions to the gamma spectrum are produced principally by the photoelectric interaction process.

(9) Background photopeaks are caused by the presence of external contamination on or near the counting equipment, high activity sources in the area, or the presence of naturally occurring radioactive materials in the environment.

Error Prevention Tools:Procedure AdherenceSelf-Checking - Stress the importance of NOT cross-contaminating counting equipment.

b. Detector efficiency TP-51

(1) There are two primary methods efficiency data are generated: the measurement of known activity sources and the use of general efficiency curves.

Ask which appears preferable.

(a) The most straightforward and preferred method is to measure the count rate produced by a gamma-ray source of known activity.

The standard spectrum should be produced with the source in the same geometry as the unknown sample to be counted. If this is not possible, the geometry should be as close to the sample geometry as possible. For example, a human phantom is used to calibrate a whole body counting system.

Ideally, a separate efficiency calibration should be performed for each possible geometry used by the system.


X. LESSON BODY INSTRUCTOR NOTES(b) A less desirable technique for

determining counter efficiency involves calculations based on the assumed knowledge of the various gamma-ray interaction probabilities. This technique involves the use of complicated computer programs to estimate the efficiencies for various geometries.

(2) Data relating to the efficiency of the detection system are commonly presented in graphical form. Two examples are shown in TP-48 (solid cylindrical NaI(Tl) crystal and TP-49 (well crystal). A number of parameters must be identified before using this type of data. These parameters include:

TP-52

TP-53

TP-54

(a) The specific category of the tabulated efficiency must be identified.

Reference F

1) The absolute efficiency is based on amount of radiation emitted by the source.

Objective 14

2) The intrinsic efficiency is based on the amount of radiation incident on the detector.

(b) The size and shape of the scintillation crystal have a significant influence on the counting efficiency.

Solid or Well Crystal

(c) The size and physical nature of the source are also important considerations in determining the efficiency. For example, is the source in a marinelli beaker, on a flat air filter, or in a “cottage cheese” container? Is the detector used in a whole body counter?

Marinelli Beaker, “Cottage Cheese” container,Nasal smears,Hot particles.


X. LESSON BODY INSTRUCTOR NOTES(d) Any absorption taking place between

the photon source and the detector will influence the efficiency.

c. Peak Area Determination Objective 15

(1) In order to apply the peak efficiency data, the area under the full-energy peaks appearing in the spectrum must be determined.

(2) It can be a rather straightforward procedure to subtract the background counts from the sample spectrum, but many times the photopeaks are superimposed on a continuum caused by many of the complicating effects we have discussed.

(3) If the spectrum did not contain a continuum, like the spectrum shown in TP-51, Figure A, the area under the peak could be determined by simple integration between the limits, or the addition of the counts in each channel under the curve.

TP-55

Reference F

A simple equation for determining the area under this curve is given by:

Reference F

BPeak Area = ∑ Ci i=A

Where,

A = the channel at the left side of the curve

B = the channel at the right side of the curve

Ci = the number of counts in the i channel, where i ranges from A to B.

TP-56

Write the equation on the board.

Handouts # 02 & 03


X. LESSON BODY INSTRUCTOR NOTESPractice Exercise: Using the equation from Figure A in Handout # 02, and the data from Handout # 03, calculate the area under the curve in Figure A

From the equation on the board, show the summation.

(4) However, in most cases, the spectrum will be superimposed over a continuum containing counts that must be subtracted. We will consider two techniques and note a third. Objective 15

(a) We can assume a shape under the continuum within the peak region and apply a linear interpolation between the continuum values on either side of the peak. The equation given in Figure B of TP-55 and Handout # 02 provides a mechanism for evaluating this area. This method essentially calculates an average background and subtracts it from the area under the photopeak.

TP 57

Write the equation on the board.

BPeak Area = ∑ Ci – (B – A)[(CA + CB)/2] i=A

Where,

A = the channel at the left side of the curve

B = the channel at the right side of the curve

Ci = the number of counts in the i channel, where i ranges from A to B.

CA = the number of counts in channel A

CB = the number of counts in channel B.

Refer to Handouts # 02 & 03


X. LESSON BODY INSTRUCTOR NOTESPractice Exercise: Using the equation from Figure B in Handout # 02, and the data from Handout # 03, calculate the area under the curve in Figure B

From the equation on the board, show the calculations for(B – A)[(CA+CB)/2] and subtract it from the summation of Ci.

(b) A second technique for determining the area under the photopeak involves taking a background spectrum and subtracting it from the sample spectrum. This is known as spectrum stripping. In its simplest form, spectrum stripping involves the channel-by-channel subtraction of the background spectrum from the sample spectrum. This technique works best if there is only one photopeak in the spectrum. If there are additional peaks, additional factors must be considered before stripping the spectrum. For many of these spectra, complicated computer programs are required to account for the background radiation.

Objective 15, TP-58


X. LESSON BODY INSTRUCTOR NOTESPractice Problem:

1) Handout # 04 is a spectrum from the analysis of a sample on a NaI(Tl) detector. The energy scale is approximately 10 keV (0.01 MeV) per channel.

a) Plot the spectrum on a sheet of graph paper, channels 1-80 only.b) Select the channels of interest under the peak.c) Use the equation from Handout # 02, Figure B to determine the area under the peak.d) Determine the energy resolution of the detector using the FWHM.

TP-59

Handout # 04

Hand out graph paper.

Let the students make suggestions for selecting the channels of interest, then guide them to select channels 34-43.

Guide the students in performing the calculations.

Area under the peak = 1969 counts

R = 10.8 % where FWHM = 0.04 MeV at 640 counts and centroid channel at 0.37 MeV. This reflects a rather poor resolution, with the typical resolution between 5 and 10%.

Error Prevention Tools:Self-Checking – Ensure the appropriate channels are used. This is especially important when using the following technique to subtract the background spectrum from the sample spectrum.


X. LESSON BODY INSTRUCTOR NOTESEnsure the background data is subtracted from the corresponding channel from the sample spectrum.

2) Handout # 05 is a background spectrum with the same energy scale as the sample spectrum. For channels 1-80 only, perform the following:

TP-60

Handout # 05

a) Strip the background spectrum from the sample spectrum.a) Plot the resulting spectrum on graph paper. Substitute zero for any negative number.a) Sum the numbers under the peak and compare this number with the value determined from the technique used above.

Assist the students as needed. Ask why some of the numbers are negative. (Background fluctuations in both the background spectrum and the sample spectrum).

TP-61

Area under the peak = 1474 counts.

(c) In most cases, closely spaced or overlapping photopeaks do not permit one of the straightforward techniques discussed above. For these spectra more complex methods must be used. These methods usually involve the use of computer codes to apply various forms of curve fitting and advanced mathematical techniques to the data.

5. Identifying Photopeaks in Gamma Spectra

Example Exercise

Let’s look at the spectrum in this handout. We have a number of peaks but we cannot tell which is the primary photopeak.

TP-62

Handout # 06

Objective 16

Handout # 07, - Peak Energies


X. LESSON BODY INSTRUCTOR NOTESa. First we should identify the pulse height

(energy) of the peaks that may be the primary photopeak. Note that the scale makes it difficult to narrow the energy down as much as we would like it, so we will have to identify a range of energies.

(1) The first peak is in the range of 0-100 keV. This probably represents X-rays and is not likely to be the primary photopeak.

Instructor Note: Point out the peaks on the slide and have the students follow along on their handout.

(2) The second peak appears to be in the range of 230-250 keV, and the third peak in the range of 330-350 keV.

Error Prevention Tools:Self-Checking;Peer-Checking;

(3) The next significant peak slightly less than 600 keV with a smaller peak around 700-730 keV. The final peak in this region is at about 900-920 keV. Note the small hump on the side of this peak in the range of 950-975 keV. This could indicate another peak under the larger one at 900-920 keV.

Questioning Attitude (i.e. Are subsequent peaks secondary peaks of the primary radionuclide, or are they peaks from other radionuclides?)

(4) The last three peaks are in the higher energy range at approximately 1500-1600 keV, 2000-2100 keV, and 2500-2600 keV. Note that the NaI(Tl) detectors are not completely linear at the higher energy levels, so these peaks may be offset slightly.

b. The next step is to compare these peaks with the photopeak energies listed in Attachment 1. (1) First, let’s look for isotopes with energies

in the range of the peak we identified at 230-250 keV.


X. LESSON BODY INSTRUCTOR NOTES(2) We note that there are 15 isotopes with

primary photopeak energies between 230 and 250 keV.

c. We must now look at the secondary peaks to determine if any of these isotopes have secondary peaks that match our unknown spectrum.

(1) As we come down the chart, we note that Pu-233 has a secondary peak at 534.8 keV, but the other secondary peaks do not match our spectrum.

(2) Looking further down the chart we note that Th-232 has a secondary peak at 2614 keV. Remember that these detectors are not completely linear at higher energies, so let’s look at the other secondary peaks for Th-232.

(3) This isotope has secondary peaks at 583, 911, and 969 keV. The 583 and 911 keV peaks for Th-232 match two of the peaks found on our spectrum. Remember the hump? The 969 keV peak matches the hump on the side of the 911 keV peak.

(4) From reference L we can determine that the photons emitted around the 1500-1600 keV range are only emitted 4 % of the time or less, therefore they are not listed in our table.

d. From our review of the unknown spectrum, we have now identified it as the spectrum of the thorium-232 isotope.

TP-63

Handout # 08


X. LESSON BODY INSTRUCTOR NOTES6. A word about other detectors.

In the last 15-20 years, significant advances have been made in gamma spectroscopy equipment. Newer detectors have been developed which provide much greater spectrum resolution than the NaI(Tl) detectors. The whole body counting equipment at TVA uses both NaI(Tl) and GeLi detectors with the same or similar analyzer equipment used for the two types of detectors. From the spectroscopy standpoint, the most obvious difference between the two systems is the output spectra. Since these are typically resolved by computer software, we will not go into additional detail regarding the operation of these advanced detectors. Procedures regarding the operation and special handling of the GeLi detectors will be addressed in applicable whole body counter-specific training.

Objective 17

One of the major limitations of scintillation counters is their relatively poor energy resolution. The chain of events required to convert incident radiation energy to light and the subsequent generation of an electrical pulse involves a number of inefficient steps. For example, the energy required to produce one information carrier (photoelectron) is on the order of 100 eV or more, and the number of carriers is relatively small.

Reference F

The only way to increase the resolution is to increase the number of information carriers per pulse. The best energy resolution today is realized through the use of semiconductor materials as radiation detectors. The basic information carriers are electron-hole pairs created along the path taken by the charged particle (primary radiation or secondary particle) through the detector. The electron-hole pair is somewhat analogous to the ion pair created in gas-filled detectors.

Modern semiconductor detectors are called solid state detectors. We will consider two types of these detectors used today in gamma spectroscopy.


X. LESSON BODY INSTRUCTOR NOTESa. In the first type of detector, germanium crystals

are grown and the impurities are balanced by an equal concentration of other impurities that offset the influence of the original impurities. Consequently, the process of lithium ion drifting has been applied to these and to silicon detectors to compensate the material after the crystals are grown. Germanium detectors produced by the lithium drifting process are referred to as GeLi detectors.

TP-60 compares the resolution of a germanium detector with that of a NaI(Tl) detector. Note the narrow photopeaks on the GeLi spectrum as compared to the wide peaks on the NaI(Tl) spectrum. In addition to superior energy resolution, solid state detectors have other advantages, including:

TP-64

TP-65

(1) Compact size(2) Relatively fast timing characteristics(3) An effective thickness that can be varied

to match the requirements of the application.

The major drawback to these detectors is that they must be cooled to prevent damage to the detector. At room temperature a major redistribution of the drifted lithium will take place which would essentially destroy the detector. To overcome this problem, the GeLi detector must be cooled to liquid nitrogen temperatures at all times.

TP-66


X. LESSON BODY INSTRUCTOR NOTESb. The second type of solid state detector we will

consider is the high-purity germanium, or HPGe, detector. These detectors consist of a high purity germanium which does not have to have the lithium additive. The advantages of this detector are similar to those of the GeLi detectors, but they only have to be cooled to liquid nitrogen temperatures while in use. Consequently, today most manufacturers have discontinued production of the GeLi detectors in favor of the HPGe type.

7. Practical Exercises

a. Problem # 1

Using the data from the Gamma Ray Intensity table identify the radionuclide spectrum presented in HO # 07

Handout # 09

TP-67

Instructor Note: After the students identify the radionuclide, pass out the solution (Handout # 10)

TP-68

b. Problem # 2

Using the data from the Gamma Ray Intensity table identify the radionuclide spectrum presented in Handout # 11.

Handout # 11

TP-69

Solution: Handout # 12

TP-70

c. Problem # 3

Using the data from the Gamma Ray Intensity table, identify the radionuclide spectrum presented in Handout # 13.

Handout # 13

TP-71

Solution:Handout # 14

TP-72


X. LESSON BODY INSTRUCTOR NOTESd. Problem # 4


Handout # 15

TP-73


TP-74

Note: May need to remind students about sum peaks.

e. Problem # 5


Handout # 17

TP-75


TP-76

Note: Remind students that the first peak is not always the primary peak. Give hints if needed that the primary peak is at 1430 (1400) keV.

Error Prevention Tools:Questioning AttitudeIs the first peak the primary peak?


XI SUMMARY

Gamma Rays are forms of electromagnetic radiation like light and X-rays. Gamma rays from a specific radionuclide will all have the same characteristic energy which can be used to identify that radionuclide. Gamma spectroscopy is the process used to measure the energy and number of photons emitted by radioactive sources emitting gamma rays.

INSTRUCTOR NOTES

TP-77

Gamma rays interact with matter in three basic mechanisms: photoelectric absorption, Compton scattering, and pair production. Photoelectric absorption is the primary mechanism for low-energy gamma rays (≤ 200 keV) and Compton scattering is the dominant mechanism for gamma ray energies between 200 keV and 5 MeV. Pair production will not occur unless there is at least 1.022 MeV of energy available. This process seldom occurs for photon energies below 5 MeV.

Gamma rays are generally measured by a scintillation detector. One of the primary materials used for detecting gamma rays is sodium iodide (NaI) activated by thallium (Tl). Light pulses generated in the scintillator are multiplied, amplified, and shaped before being changed to digital pulses and stored in a multi-channel analyzer. There the measured pulses are proportional to the sample activity while the amplitudes of the pulses are proportional to the energy deposited in the detector. By analyzing these two parameters we can identify and quantify the source of the gamma rays.

The gamma ray spectrum consists of several features, including (1) the photopeak; (2) backscatter peaks; (3) the Compton continuum; (4) annihilation peaks; (5) escape peaks; (6) sum peaks; (7) bremsstrahlung; (8) characteristic X-rays; and (9) background radiation peaks.

TP-78


SUMMARY INSTRUCTOR NOTES

The efficiency of a detection system may be based on the amount of radiation released from the source (absolute efficiency) or the amount of radiation that reaches the detector (intrinsic efficiency). The efficiency of a system is a function of (1) the category of the efficiency; (2) the size and shape of the scintillation detector, ; (3) the size and physical nature of the source; and (4) any absorption taking place between the source and the detector.

TP-79

Gamma ray spectra may be analyzed with a straightforward background subtraction process or complicated computer programs that consider several parameters in accounting for the background.

Other types of detectors used to measure gamma ray activity include lithium drifted germanium (GeLi) detectors and high purity germanium (HPGe) detectors. These solid state systems are more efficient, use smaller size detectors, and are much faster than the NaI(Tl) detectors, but they must be cooled to liquid nitrogen temperatures.

TP-80

Note to Instructor: When printing this document, the figures print much better on a color printer. Also, the margins will have to be reset to fit Handouts # 4 & 5 properly on the page and Handout # 7 must be printed in ‘Landscape’ mode.


Handout # 01Enabling Objectives

1. State the characteristics of gamma rays and the purpose of gamma-ray spectroscopy.

2. Identify the most common technique for measuring photon energy.

3. Name the three basic mechanisms by which photons interact with matter and describe each mechanism.

4. Identify the energy range of each interaction mechanism.

5. Define the following:

a. Amplitude

b. Annihilation radiation

c. Backscatter peak

d. Bremsstrahlung

e. Characteristic X-Rays

f. Energy resolution

g. Full Width at Half Max (FWHM)

h. Multiplet

i. Photopeak

j. Summation effects/Sum peak

k. X-Ray escape peak

6. State the minimum energy necessary to cause pair production to take place.

7. State and define the unit of measurement for radiation energy.

8. Demonstrate familiarity with nuclide decay schemes.

9. Identify the primary material used in scintillation detectors and state the characteristics of the material.


10. Describe the basic components of a gamma spectroscopy system and tell the purpose of each.

11. Describe the two primary shapes of NaI(Tl) detectors.

12. Calculate the energy resolution from a gamma-ray spectrum.

13. Describe at least seven (7) of the features that can contribute to the gamma-ray spectrum.

14. Define detector efficiency and describe the difference between absolute efficiency and intrinsic efficiency.

15. Describe the two methods used to account for background and calculate the peak area under a spectrum curve.

16. Be able to use available references to identify the gamma-emitting radionuclides by their gamma spectrum.

17. Describe two types of materials used in late model gamma spectroscopy systems today.


Handout # 02

Obtaining Peak Areas From Multichannel Spectra

A

B


Handout # 03

Determining Peak Area

Using the figure and equations from Handout # 04, assume that the following data were obtained from the spectrum:

Channel Number Counts, Figure A Counts, Figure B

58 100 17059 120 20060 150 22061 180 25062 200 30063 250 34064 280 40065 300 47066 320 56067 300 49068 270 39069 240 34070 190 29071 170 23072 130 19073 100 120


Handout # 04

I-131 + Background Spectrum

I-131 + Background Spectrum Counts per Channel

Channel # 1 2 3 4 5 6 7 8 9 0

1-10 0 0 0 0 0 0 178.2 667.3 772.9 853.111-20 792.7 669.5 781.8 771.4 791.8 916.3 945.2 916.8 789.2 84521-30 896.3 739.8 699.6 791.4 695.1 713.5 709.7 634.6 596.3 69931-40 602 554.2 527.6 524.3 693.7 675 829.6 798.8 605.6 480.241-50 392.3 357.3 293.7 304.7 332.7 309.7 297.4 368.3 331.6 346.151-60 335.2 356.2 299.1 314.9 300.7 238.8 297.4 229.7 253.4 304.761-70 262.1 320.6 268.2 207.6 252.8 207.6 190.8 171.3 170.8 166.971-80 174.8 171.2 170.4 189.1 142 125 140 141.7 137.3 138.981-90 112.2 117.6 134.8 146 120.8 150 129.8 160.2 118.9 144.5

91-100 137.8 134.5 123.5 143 108.1 88.5 128.8 101.1 107.9 108.5101-110 107.8 121.1 86.7 104.9 122.9 103.3 127.1 117.2 90 95111-120 99.1 93.7 105.7 79.2 95.1 101.6 78.6 78.2 94.3 93.9121-130 95.5 81.7 63.6 75.3 61.4 53.3 65.8 89.6 71.2 59.3131-140 77 86.3 71.5 81.4 76.1 88.2 86.8 91.2 107.1 92.4141-150 103.1 87 62.5 63.4 76.4 57 59.6 48.1 62.3 77.2151-160 43.6 52.2 62.8 45.7 53.1 39.2 39.6 40.8 60.1 51.9161-170 38.8 37.8 32 58.3 53.6 52.8 46.2 41.3 52.4 54.7171-180 56.1 54.7 40 41.8 45.6 33.2 40 22.6 36 26181-190 36.8 24 27 20.8 22.6 27.6 30.6 27.6 28.1 33.5191-200 19 20.9 22.8 35.6 34.2 18.5 27.8 27.9 26.1 30.1201-210 24.6 20.9 21.1 32.5 42.1 33.7 26.8 31.1 27.8 36211-220 25.8 38 31.5 26.2 34.1 38.6 20.2 26 27.8 33.4221-230 9.7 15.5 7.5 12 14.8 14.1 13.4 20.9 22.2 13.5231-240 11.1 18.6 9.5 20.3 18.2 19.4 5.5 17.8 14 9241-250 17.7 9.6 18.7 6.9 1.5 -1.1 0.3 -2 2.5 -0.7251-256 2.1 1.8 0.8 0.4 0.2 0.7


Handout # 05

Background Spectrum

Background SpectrumCounts per Channel

Channel # 1 2 3 4 5 6 7 8 9 0

1-10 0 0 0 0 0 190.9 638.1 751.2 777.511-20 719.2 675.6 704.7 732.6 779 781.6 773.7 748.9 728 73621-30 705.2 702.2 668 706.5 713.2 664.8 614 581.2 583.4 579.131-40 555.1 516.9 495.5 491.4 510.3 534.9 494.9 435.2 387.6 35841-50 337.9 332.8 333.9 311.5 309.7 316.2 324.7 329.8 333.2 343.451-60 350.7 353.1 317.1 290.4 276.8 244.9 249.1 259.5 254.7 272.961-70 265.9 267.1 244 221.2 206 197.6 178 179.9 179.8 175.171-80 174.5 164.7 161.2 168.1 151.8 158.8 157.1 148.4 152.4 155.381-90 146.7 141.7 141.2 142.3 136.7 134.2 138.1 135 132.8 124.9

91-100 124.7 124.1 125.1 128.5 114.7 112.3 112.5 115.2 109.5 110.5101-110 110.7 105.8 103.6 105.1 106.6 102.5 104.8 106.1 110.8 108.7111-120 107.6 99.8 101.3 91.2 93.9 91.1 87.6 87.3 82.8 86.8121-130 83.2 80 79.9 72 79.9 70.3 72.6 75.9 70.3 76.6131-140 74.6 74.8 80.3 80.1 90.3 93.6 98.3 95.3 99.6 93.4141-150 94.9 93.9 85.9 75.4 73.3 64.9 57.5 52.7 51.5 48.9151-160 46.2 48.2 45.7 45.3 46.9 45 42.7 45.8 44.3 45.6161-170 45.3 46.2 45.3 48.5 49.9 48.3 51.7 53 56.3 49.6171-180 50.7 47.4 45.9 45 39.3 35.7 31.5 37.4 31.3 32.5181-190 28.5 27.6 31.2 26 32.1 28.3 26.9 27.8 24 26.9191-200 25.6 24.1 25.4 24.7 23.7 24 22.9 24.8 25.8 24.3201-210 23.8 26.6 25.8 26.8 27.8 30.1 26.3 27.9 28.1 31.5211-220 32.1 31.8 28.3 27.3 28.4 27.8 26.6 25.8 23.4 20.7221-230 22.5 19.2 17.9 17.5 17.4 17.2 17.5 16.8 15.3 17.7231-240 16.8 16.7 17.1 16.6 16.3 16.8 15.8 16.7 17.2 17.7241-250 18.4 16.3 18.8 7.3 0.2 0.1 0 0 0 0251-256 0 0 0 0 0 0


Handout # 06

Example Exercise


Handout # 07

Gamma Ray Intensity With Corresponding Isotope

PrimaryPhoton,keV

% Abd. Isotope Half-Life,Seconds

SecondaryPhoton,keV

% Abd. SecondaryPhoton,keV



% Abd.

186.17 10.0 Au-193 6.354e+04 255.57 (7) 268.22 (4) 173.52 (3)

186.21 03.2 Ra-226 5.049e+10

186.60 16.0 Hg-193 1.368e+04 258.00 (14) 861.10 (13) 429.50 (11) 381.60 (11)

186.72 27.6 Re-190M 1.920e+03 605.21 (15) 557.97 (14) 569.31 (14) 361.14 (12)

186.72 48.4 Re-190 1.860e+02 557.97 (29) 223.81 (26) 569.31 (25) 828.99 (23)

186.72 49.7 Ir-190 1.018e+06 63.00 (43) 605.14 (38) 518.55 (33) 557.98 (28)

188.43 54.9 Xe-125 6.048e+04 243.40 (29) 54.96 (6) 453.83 (4) 846.50 (1)

188.90 47.6 Pd-109M 2.820e+02

189.90 17.7 In-114M 4.320e+06 558.27 (5) 725.21 (5)

190.30 65.7 Rb-81 1.649e+04 12.65 (31) 446.14 (19) 12.60 (16) 456.71 (2)

190.33 46.0 Ba-141 1.096e+03 304.18 (25) 276.95 (23) 343.66 (14) 647.88 (6)

191.98 18.8 Mo-101 8.772e+02 590.87 (16) 1012.50 (13) 2032.00 (7)

193.59 05.8 Th-229 2.316e+11 210.93 (4) 124.68 (2) 137.06 (2) 31.24 (1)

197.10 95.9 O-19 2.690e+01 1356.80 (50) 1444.10 (3) 109.90 (3) 1554.00 (1)

197.90 59.0 Ta-186 6.300e+02 214.90 (50) 510.60 (44) 737.50 (34) 615.30 (33)

Page 1 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

228.16 88.0 Te-132 2.754e+05 49.72 (14) 116.30 (2) 111.76 (2)

229.30 64.4 Gd-147 1.370e+05 41.54 (48) 396.00 (34) 40.90 (27) 928.90 (19)

229.33 25.6 Re-182 2.300e+05 1121.22 (22) 1221.35 (17) 100.10 (16) 1230.97 (14)

229.50 32.0 Ag-115 1.200e+03 213.50 (8) 473.20 (6) 2156.80 (5) 131.40 (5)

231.69 84.7 Sr-85M 4.080e+03 151.18 (12) 13.37 (7)

233.50 09.9 Xe-133M 1.892e+05

235.40 100.0 Pu-233 1.254e+03 534.80 (90) 500.30 (39) 688.10 (33) 1004.00 (31)

235.60 25.6 Nb-95M 3.132e+05

236.00 11.0 Th-227 1.620e+06 50.10 (8) 256.30 (6) 329.90 (2) 300.00 (2)

238.63 44.6 Pb-212 3.830e+04 300.11 (3) 115.19 (1)

238.63 44.6 Th-232 4.434e+17 2614.60 (36) 583.14 (31) 911.07 (28) 968.94 (17)

239.00 01.6 As-77 1.400e+05 520.65 (1)

241.00 03.9 Ra-224 3.162e+05

242.70 100.0 Tm-165 1.080e+05 806.80 (33) 459.90 (11) 218.60 (10) 346.60 (9)

245.40 94.0 In-111 2.425e+05 171.28 (90)

245.40 94.0 Cd-111M 2.920e+03 150.80 (30)Page 2 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

247.90 65.0 Rb-84M 1.216e+03 215.40 (37) 463.70 (32)

247.90 80.6 Tb-154M2 8.136e+04 346.70 (71) 43.00 (61) 1419.90 (47) 123.10 (44)

249.65 89.8 Xe-135 3.277e+04 608.60 (3)

252.85 06.1 Am-245 7.340e+03 109.29 (6) 104.61 (4)

253.80 02.5 Se-73M 2.340e+03 511.00 (36) 84.50 (2) 25.71 (2) 393.40 (2)

255.12 21.1 Ba-142 6.360e+02 1204.30 (15) 895.20 (14) 231.52 (12) 1078.70 (12)

256.90 97.5 Dy-152 8.568e+03 44.48 (40) 43.74 (22) 50.30 (12) 51.70 (4)

257.97 61.4 Hg-193M 4.248e+04 407.70 (25) 573.20 (14)

258.41 31.5 Xe-138 8.448e+02 434.56 (20) 1768.26 (17) 2015.82 (12) 396.51 (6)

258.50 00.0 At-217 3.230e-02

260.07 79.0 Tb-162 4.680e+02 807.53 (42) 888.20 (38) 185.29 (17) 882.32 (13)

261.00 52.0 Ag-101 6.660e+02 511.00 (138) 21.10 (21) 588.00 (10) 667.30 (10)

261.26 12.7 Kr-79 1.260e+05 511.00 (14) 397.56 (9)

261.70 67.9 Au-195M 3.050e+01 68.81 (11) 66.99 (6) 77.90 (4) 200.40 (2)

261.75 37.9 Hg-195M 1.440e+05 560.27 (9) 387.87 (3) 200.38 (1) 1241.17 (1)Page 3 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

357.30 81.0 La-130 5.220e+02 511.00 (156) 550.60 (27) 544.40 (18) 907.90 (17)

357.96 89.0 Tc-104 1.086e+03 530.40 (16) 535.10 (13) 884.33 (12) 892.90 (9)

360.90 62.0 Gd-161 2.220e+02 315.20 (23) 102.30 (15) 283.70 (6) 56.40 (5)

361.10 96.5 Se-73 2.590e+04 511.00 (132) 67.00 (77) 10.54 (16) 10.51 (8)

363.56 11.5 Gd-159 6.696e+04 58.00 (2)

364.49 82.4 I-131 6.930e+05 636.90 (7) 284.31 (6) 80.16 (3) 722.91 (2)

364.50 01.5 As-79 5.400e+02 432.00 (1) 878.50 (1)

367.90 18.9 Au-200M 2.904e+03 1225.40 (11) 1262.90 (3) 70.82 (1)

367.90 77.0 Au-200 6.732e+04 497.80 (73) 579.20 (72) 255.90 (71) 759.50 (66)

367.90 87.2 Tl-200 9.396e+04 70.82 (40) 1205.70 (30) 68.89 (24) 579.30 (14)

372.80 22.5 Sc-43 1.400e+04 511.00 (156)

372.80 87.9 K-43 8.028e+04 617.50 (78) 396.90 (11) 593.40 (10) 220.60 (4)

381.10 78.0 Y-87M 4.644e+04

381.80 77.0 Os-183 4.680e+04 61.14 (72) 59.72 (42) 69.20 (25) 114.40 (21)

385.80 91.4 Tl-197M 5.400e-01 222.70 (30) 72.87 (8) 70.83 (5) 82.50 (3)Page 4 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

439.90 33.0 Ne-23 3.724e+01 1636.50 (1)

440.40 27.4 Bi-213 2.735e+03

441.60 53.5 Gd-162 6.200e+02 402.80 (46) 38.80 (6)

442.89 17.5 I-128 1.500e+03 526.62 (2)

442.90 25.8 Cs-128 2.340e+02 511.00 (137) 29.80 (13) 29.50 (7) 33.60 (4)

450.80 97.0 W-180 5.500e-03 350.70 (95) 390.00 (90) 234.30 (84) 103.65 (23)

453.70 63.0 Pm-146 1.750e+08 747.00 (37) 735.60 (23) 633.10 (2)

453.70 66.0 Hf-179M 2.169e+06 55.79 (56) 362.60 (38) 54.61 (32) 122.70 (27)

453.80 48.0 Pr-146 1.440e+03 1525.40 (18) 735.80 (8) 789.00 (8) 1376.50 (6)

454.90 100.0 Ac-230 1.220e+02 508.20 (63) 1243.90 (43) 1347.70 (19) 1949.80 (15)

455.51 31.0 Xe-137 2.292e+02 849.00 (1)

464.50 77.0 La-132 1.730e+04 511.00 (82) 32.20 (24) 567.10 (16) 31.80 (13)

471.80 71.3 Cm-241 2.834e+06 106.52 (36) 102.08 (23) 120.00 (14) 123.80 (5)

472.30 100.0 Ne-24 2.030e+02 874.40 (8)

475.02 06.7 Tc-102 5.300e+00 468.90 (1) 865.50 (1) 627.70 (1) 1105.50 (1)

475.06 46.0 Rh-102M 1.788e+07 511.00 (29) 628.05 (4) 468.58 (3) 1103.16 (3)Page 5 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

475.06 87.2 Tc-102M 2.610e+02 628.05 (27) 630.29 (17) 1615.30 (16) 1103.30 (13)

475.06 96.7 Rh-102 9.150e+07 631.29 (57) 697.49 (45) 1046.59 (34) 766.84 (34)

477.59 10.4 Be-7 4.605e+06

482.16 83.0 Hf-181 3.660e+06 133.05 (41) 345.95 (12) 136.25 (7)

482.30 62.3 Sn-128 3.558e+03

482.60 96.7 Ir-194M 1.480e+07 328.50 (93) 600.50 (62) 687.80 (59) 338.80 (55)

483.50 92.0 Y-87 2.880e+05 511.00 (4)

490.90 99.0 Sn-127 2.480e+02 1348.00 (5) 1564.00 (4)

496.36 47.0 Ba-131 1.002e+06 123.80 (29) 216.08 (20) 373.24 (15) 249.43 (3)

497.04 91.1 Ru-103 3.390e+06 610.33 (6)

510.00 55.0 Os-182 7.776e+04 61.14 (43) 180.20 (37) 59.72 (25) 69.20 (15)

511.00 140.0 Ag-106 1.440e+03

511.00 162.0 C-11 1.220e+03

511.00 193.4 F-18 6.590e+03

511.00 199.8 P-30 1.500e+02Page 6 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

511.00 200.0 N-13 5.980e+02

511.00 200.0 O-15 1.230e+02

511.00 200.0 Ne-19 1.740e+01

511.00 200.0 Cl-34 1.526e+00

511.00 200.0 Ca-39 8.700e-01

511.00 200.0 V-46 4.260e-01

511.00 200.0 Al-26M 6.370e+00

511.00 200.0 K-38M 9.250e-01

511.60 30.0 Zn-71 1.440e+02 910.30 (7) 390.00 (4) 121.52 (3) 1120.00 (2)

511.70 86.0 Rh-106M 7.920e+03 1046.70 (31) 716.20 (29) 450.80 (24) 616.10 (20)

511.70 86.0 Ag-106M 7.260e+05 804.30 (41) 717.30 (31) 1045.00 (29) 616.00 (23)

511.80 20.5 Rh-106 2.980e+01 621.80 (10) 1050.10 (1) 616.70 (1)

513.97 00.4 Kr-85 3.383e+08

513.97 99.2 Sr-85 5.603e+06

517.90 72.5 V-55 6.540e+00 880.60 (18) 921.20 (5) 565.80 (5) 1214.70 (4)

520.43 47.0 Rb-83 7.440e+06 529.65 (30) 552.63 (17) 790.10 (1)Page 7 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

657.70 94.3 Ag-110M 2.158e+07 884.20 (73) 937.40 (34) 1383.85 (24) 763.80 (22)

657.73 05.6 Ag-110 2.460e+01

657.73 98.8 In-110M 1.760e+04 884.72 (95) 937.49 (70) 707.38 (31) 641.70 (27)

657.92 98.3 Nb-97 4.416e+03 1024.53 (1)

661.60 89.9 Ba-137M 1.530e+02 32.00 (6)

661.64 86.0 Cs-137 9.512e+08 32.00 (6)

665.00 100.0 Tc-98 1.300e+14 765.00 (100)

666.33 99.6 Sb-126 1.080e+06 695.00 (100) 414.70 (83) 720.50 (54) 697.00 (29)

666.70 100.0 Sb-126M 1.140e+03 696.10 (100) 414.40 (88)

667.68 98.7 I-132 8.225e+03 772.60 (76) 954.55 (18) 522.64 (16) 630.21 (14)

667.69 97.4 Cs-132 5.594e+05 29.78 (39) 29.46 (21) 33.57 (11) 34.40 (2)

669.71 08.4 Zn-63 2.300e+03 511.00 (186) 962.14 (7)

677.20 78.4 S-30 1.180e+00 511.00 (200) 2341.40 (2)

678.80 94.3 In-107M 5.050e+01

684.34 100.0 At-204 5.400e+02 516.32 (95) 426.24 (71) 511.00 (26) 609.14 (26)

684.70 99.6 Mo-93 2.480e+04 1477.20 (99) 263.10 (56)Page 8 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

803.30 00.0 Tl-206 2.520e+02

805.52 20.5 Xe-140 1.360e+01 1413.66 (13) 1315.05 (9) 621.98 (8) 1309.08 (7)

810.76 99.4 Co-58 6.127e+06 511.00 (29) 6.41 (23) 7.06 (3) 863.94 (1)

812.80 45.7 Sb-129 1.588e+04 914.60 (21) 544.70 (19) 1030.10 (13) 966.40 (8)

818.50 99.7 Cs-136 1.132e+06 1048.00 (80) 340.60 (47) 1235.00 (20) 176.60 (14)

825.20 71.4 Pb-203M 6.100e+00 74.97 (8) 820.30 (6) 72.80 (4) 84.80 (3)

826.50 61.5 Er-161 1.166e+04 47.55 (46) 46.70 (26) 53.75 (15) 55.30 (4)

831.69 33.0 Rb-90 1.530e+02 4365.90 (9) 1060.70 (8) 4135.50 (7) 3383.24 (7)

831.69 96.5 Rb-90M 2.580e+02 1375.36 (18) 3317.00 (15) 2752.69 (12) 1060.70 (10)

834.00 79.7 As-72 9.360e+04 629.86 (8) 1464.00 (1) 1050.76 (1)

834.00 95.6 Ga-72 5.080e+04 2201.67 (26) 629.86 (25) 2507.80 (13) 894.22 (10)

834.80 97.0 V-54 4.980e+01 989.00 (80) 2259.40 (46) 1961.50 (10) 1463.50 (9)

834.81 99.9 Mn-54 2.702e+07 5.41 (22) 5.95 (3)

839.40 99.8 Sb-130M 3.900e+02 793.60 (86) 182.30 (41) 1017.50 (30) 816.30 (12)

841.54 12.5 Eu-152M1 3.350e+04 963.20 (10) 121.77 (7) 344.26 (2) 1314.50 (1)

843.76 71.8 Mg-27 5.675e+02 1014.40 (28) 170.69 (1)Page 9 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

846.74 98.8 Mn-56 9.283e+03 1810.69 (27) 2113.05 (14) 2522.88 (1) 2657.45 (1)

846.75 99.9 Co-56 6.797e+06 1238.30 (66) 511.00 (38) 6.41 (22) 2598.57 (17)

847.03 95.4 I-134 3.156e+03 884.09 (65) 1072.55 (15) 595.36 (11) 621.79 (11)

870.80 03.3 N-17 4.170e+00

870.90 100.0 Tc-94 1.760e+04 702.60 (100) 849.70 (98) 916.20 (7) 449.10 (3)

871.10 94.0 Tc-94M 3.120e+03 1868.80 (6) 1522.00 (5) 2740.00 (4) 993.10 (2)

879.36 28.5 Tb-160 6.220e+06 298.58 (27) 966.15 (24) 1177.93 (14) 86.79 (13)

881.50 42.0 Br-84M 1.910e+03 1897.30 (15) 3927.50 (7) 2484.10 (7) 1015.90 (6)

881.50 67.7 Rb-84 2.930e+06 511.00 (54) 12.65 (22) 12.60 (11) 1897.30 (1)

889.30 99.9 Sc-46 7.242e+06 1120.50 (100)

891.50 100.0 Bk-244 1.566e+04 217.60 (89) 921.50 (19) 490.50 (16) 187.60 (15)

893.70 65.8 Eu-145 5.132e+05 40.10 (41) 39.50 (23) 1658.70 (16) 653.50 (15)

895.20 54.0 Er-173 8.400e+01 199.20 (48) 192.80 (46) 50.74 (34) 122.40 (21)

897.70 00.2 Tl-207 2.860e+02

899.15 99.1 Pb-204M 4.014e+03 374.74 (94) 911.74 (91) 74.97 (4) 72.80 (3)Page 10 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

909.10 00.0 Sr-89 4.368e+06

909.10 99.4 Zr-89 2.823e+05 511.00 (44) 1729.20 (1) 1712.90 (1)

911.07 27.8 Ac-228 2.207e+04 968.90 (17) 338.40 (11) 328.00 (4)

912.58 62.8 Te-133M 3.324e+03 647.60 (22) 863.91 (18) 914.72 (12) 334.14 (9)

912.82 100.0 Ir-187 3.960e+04 427.08 (87) 400.88 (83) 610.88 (79) 977.39 (61)

918.24 49.0 Y-94 1.122e+03 1139.20 (7) 550.10 (6) 1670.00 (3) 750.52 (2)

931.50 75.0 Co-55 6.314e+04 511.00 (152) 477.20 (20) 1408.70 (16) 1316.70 (7)

933.60 01.7 Cd-115M 3.871e+06

934.44 13.7 Y-92 1.274e+04 1405.44 (5) 561.11 (2) 448.50 (2) 844.12 (1)

934.51 99.1 Nb-92M 8.752e+05 911.90 (2) 1847.50 (1)

934.53 100.0 Nb-92 1.100e+15 561.10 (100)

943.60 44.0 Sb-131 1.382e+03 932.80 (24) 642.10 (18) 1123.80 (9) 658.00 (6)

944.20 43.1 Tb-158 3.760e+10 43.00 (39) 42.31 (22) 962.10 (20) 48.70 (12)

954.20 18.8 Y-95 6.200e+02 2176.00 (8) 3577.10 (8) 1324.30 (5) 2633.00 (5)

960.62 23.5 Lu-169 1.230e+05 191.21 (21) 1449.74 (10) 889.75 (5) 1466.84 (3)

960.70 91.4 Pb-202M 1.271e+04 422.10 (85) 787.00 (50) 490.50 (9) 459.70 (9)Page 11 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

960.70 99.3 Bi-202 6.192e+03 422.10 (84) 657.50 (61) 74.97 (43) 72.80 (26)

961.80 04.7 Cd-105 3.360e+03 346.87 (4) 1302.40 (4) 607.22 (4) 1693.34 (4)

969.32 43.0 Pa-232 1.132e+05 894.35 (20) 150.06 (11) 453.66 (9) 819.19 (8)

973.90 99.9 Sb-132 1.680e+02 697.05 (86) 989.60 (15) 103.00 (14) 816.60 (11)

974.80 14.0 Na-25 5.960e+01 585.10 (14) 389.70 (13) 1611.80 (9)

983.50 100.0 Sc-48 1.580e+05 1312.09 (100) 1037.50 (97) 175.36 (7) 1212.00 (2)

983.50 100.0 V-48 1.380e+06 511.00 (100) 1312.09 (97) 4.51 (9) 944.10 (8)

984.00 58.0 Bi-204 4.039e+04 74.97 (39) 72.80 (23) 84.80 (13) 912.00 (11)

984.45 27.8 Np-238 1.829e+05 1028.54 (20) 1025.87 (10) 923.98 (3) 882.37 (1)

987.80 73.2 Am-240 1.875e+05 103.76 (29) 888.80 (25) 99.55 (18) 116.90 (11)

992.20 45.0 Ga-64 1.572e+02 511.00 (196) 3366.90 (16) 809.40 (14) 1387.80 (13)

997.10 87.0 Tl-207M 1.330e+00 351.00 (80) 72.87 (12) 70.83 (7) 82.50 (4)

1001.20 00.5 Pa-234 7.050e+01

1006.30 89.6 V-53 9.660e+01 1289.50 (10) 283.10 (1)

1007.50 24.0 Cu-69 1.620e+02 834.40 (13) 531.20 (6) 1429.80 (4) 594.90 (3)Page 12 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

1024.25 33.5 Sr-91 3.413e+04 749.77 (24) 652.98 (12) 925.77 (4) 620.17 (2)

1025.00 25.0 Cd-119M 1.320e+02 2021.30 (22) 720.80 (18) 1203.70 (13) 1101.90 (10)

1031.00 21.0 Se-83M 7.000e+01 356.00 (17) 676.00 (16) 989.00 (15) 2054.00 (12)

1031.88 58.0 Rb-89 9.090e+02 1248.10 (42) 2196.00 (13) 657.71 (10) 2570.14 (10)

1039.20 09.0 Cu-66 3.060e+02

1039.29 38.8 Ga-66 3.420e+04 2752.10 (24) 833.56 (6) 2190.00 (6) 4295.70 (4)

1039.40 00.5 Ga-70 1.266e+03

1039.60 41.6 As-70 3.180e+03 511.00 (82) 744.00 (11) 668.20 (11) 1114.40 (11)

1056.50 02.0 Sm-143 5.340e+02 511.00 (92)

1056.90 100.0 O-20 1.360e+01

1067.10 09.0 Sn-125 8.316e+05 1089.15 (4) 822.48 (4) 915.55 (4) 2001.84 (2)

1076.63 08.6 Rb-86 1.612e+06

1076.63 82.5 Y-86 5.260e+04 627.72 (33) 1153.05 (31) 777.37 (22) 1920.72 (21)

1077.35 03.2 Ga-68 4.100e+03 511.00 (176)

1077.70 66.3 Cu-68 3.000e+01 1261.80 (13) 1337.70 (10) 805.70 (2) 577.60 (2)

1078.86 27.9 Am-246 1.500e+03 798.80 (25) 1062.04 (17) 1036.00 (13)Page 13 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

1089.00 00.6 Sn-123 1.115e+07

1093.60 68.9 Lu-172 5.789e+05 52.39 (54) 900.70 (33) 51.35 (31) 181.50 (23)

1099.22 56.5 Fe-59 3.844e+06 1291.56 (43) 192.33 (3) 142.65 (1)

1102.00 50.0 Os-183M 3.564e+04 61.14 (34) 1108.00 (23) 59.72 (19) 69.20 (11)

1106.40 27.0 Ge-69 1.406e+05 511.00 (73) 573.90 (12) 871.70 (10) 1336.20 (3)

1114.30 29.8 Sn-127M 7.560e+03 1095.60 (15) 823.10 (8)

1115.45 50.7 Zn-65 2.109e+07 8.04 (34) 8.91 (5) 511.00 (3)

1118.70 38.0 Kr-90 3.230e+01 121.82 (33) 539.49 (30) 242.19 (10) 1537.85 (9)

1126.80 01.0 Nd-141 9.360e+03 511.00 (6)

1129.10 92.0 Nb-90 5.260e+04 2319.20 (82) 141.15 (69) 2186.40 (18) 132.60 (4)

1153.70 12.0 Eu-156 1.312e+06 811.77 (10) 88.95 (9) 1230.71 (8) 1242.43 (7)

1157.00 58.2 K-44 1.326e+03 2150.80 (23) 2519.00 (10) 1499.50 (8) 1126.10 (8)

1157.00 99.8 Sc-44 1.414e+04 511.00 (188) 1499.45 (1)

1171.28 100.0 Sb-120M 5.010e+05 1023.06 (99) 197.20 (89) 89.86 (77) 1112.92 (1)

1172.20 01.3 Sb-120 9.540e+02 511.00 (87)Page 14 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

1172.90 83.8 Co-62 9.000e+01 2301.80 (15) 1128.90 (11) 1985.10 (2) 2345.90 (1)

1172.90 97.9 Co-62 8.340e+02 1163.50 (68) 2003.70 (19) 1718.60 (7) 2104.60 (6)

1173.23 100.0 Co-60 1.663e+08 1332.51 (100)

1204.90 00.3 Y-91 5.055e+06

1229.50 02.5 Sb-118 2.100e+02 511.00 (150)

1229.50 100.0 Sb-118M 1.840e+04 1050.80 (98) 253.90 (93) 41.00 (18) 1091.80 (2)

1241.76 09.0 Lu-174 1.050e+08 76.50 (8)

1260.41 29.0 I-135 2.380e+04 1131.51 (23) 1457.56 (9) 1038.76 (8) 1791.20 (8)

1266.10 01.1 S-31 2.560e+00 511.00 (200)

1266.20 00.0 Si-31 9.430e+03

1273.30 01.3 P-29 4.120e+00 511.00 (200)

1273.50 91.0 Al-29 3.960e+02 2425.70 (5) 2027.80 (3)

1274.55 99.9 Na-22 8.206e+07 511.00 (181)

1283.20 07.3 Cs-139 5.640e+02 627.30 (2)

1293.54 84.5 In-116M 3.249e+03 1097.21 (55) 416.99 (28) 2112.30 (15) 818.67 (12)

1293.64 99.1 Ar-41 6.577e+03Page 15 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

1297.10 75.0 Ca-47 3.919e+05 807.86 (7) 489.20 (7)

1299.83 00.1 In-114 7.190e+01

1300.50 52.2 S-39 1.150e+01 1696.60 (44) 396.50 (40) 874.30 (13) 484.90 (11)

1313.20 67.0 I-136 8.300e+01 1321.20 (25) 2289.60 (11) 2414.80 (7) 2635.50 (7)

1313.30 100.0 I-136M 4.600e+01 381.37 (100) 197.33 (78) 370.13 (17) 750.05 (6)

1332.50 88.0 Cu-60 1.392e+03 1791.60 (45) 826.40 (22) 1861.60 (5) 3124.10 (5)

1332.51 100.0 Co-60 1.663e+08 1173.23 (100)

1346.90 00.5 Pr-139 1.620e+04 511.00 (18)

1354.50 01.6 La-141 1.404e+04

1362.95 66.0 Tc-93 9.900e+03 1520.28 (24) 1477.15 (10)

1368.55 100.0 Na-24 5.407e+04 2754.10 (100)

1368.60 96.0 Al-24 2.070e+00 511.00 (200) 7069.50 (43) 2754.00 (41) 5392.70 (18)

1377.90 77.9 Ni-57 1.282e+05 511.00 (81) 6.90 (18) 127.60 (16) 1919.50 (13)

1383.94 93.3 Sr-92 9.436e+03 953.32 (4) 430.56 (3) 241.52 (3) 1142.30 (3)

1420.00 32.0 Br-87 5.570e+01 1476.19 (12) 531.90 (8) 1095.40 (6) 1360.90 (5)Page 16 of 17


Handout # 07


PrimaryPhoton,keV


SecondaryPhoton,keV




% Abd.

1434.06 99.0 Mn-52 4.483e+05 935.50 (94) 744.20 (90) 511.00 (59) 5.41 (16)

1434.10 98.3 Mn-52M 1.266e+03 511.00 (193) 377.74 (2)

1434.19 100.0 V-52 2.250e+02 1333.62 (1)

1435.80 66.7 La-138 4.039e+18 788.74 (33)

1435.86 19.0 Cs-138M 1.740e+02 462.79 (19) 191.70 (15) 112.50 (2) 324.50 (1)

1435.86 76.3 Cs-138 1.932e+03 462.79 (31) 1009.78 (30) 2218.00 (15) 546.94 (11)

1460.75 10.6 K-40 4.030e+16

1465.12 22.2 Pm-148 4.640e+05 550.27 (22) 914.85 (11) 611.26 (1) 896.42 (1)

1481.84 23.5 Ni-65 9.072e+03 1115.52 (15) 366.27 (5)

1509.60 100.0 Tc-92 2.640e+02 773.10 (97) 329.30 (78) 147.90 (55) 243.70 (15)

1524.60 18.3 K-42 4.450e+04

1528.20 03.7 Cr-55 2.130e+02

1564.62 62.0 Br-86 5.550e+01 2751.15 (19) 1361.66 (10) 1389.76 (10) 1534.20 (8)

1566.90 100.0 Tl-209 1.320e+02 465.10 (98) 117.25 (86)

1575.60 03.7 Pr-142 6.910e+04

1596.20 00.4 Pr-140 2.030e+02 511.00 (101)Page 17 of 17


Handout # 08

Example Exercise – Solution


Handout # 09

Practical Exercises

Problem # 1

Using the data from the Gamma Ray Intensity table identify the radionuclide spectrum presented below.


Handout # 10

Practical Exercises

Problem # 1, Solution


Handout # 11

Practical Exercises

Problem # 2


Handout # 12

Practical Exercises



Handout # 13

Practical Exercises

Problem # 3


Handout # 14

Practical Exercises



1.46 MeVBremsstrahlung, 1.32 MeV β-


Handout # 15

Practical Exercises

Problem # 4


Handout # 16

Practical Exercises



Handout # 17

Practical Exercises

Problem # 5


Handout # 18

Practical Exercises


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