Use of Ambient Dose Equivalent, Directional Dose Equivalent, Routine, specials and accident monitoringKhalil-ur-RahmanAE, CNS, PNRA.

Radiation Protection Course

15.04.2008Radiation Protection Course*ContentsAmbient Dose Equivalent and use Directional Dose Equivalent Individual dose Equivalent, SuperficialIndividual dose Equivalent, Penetrating

Radiation Protection Course

15.04.2008Radiation Protection Course*Environmental MonitoringAmbient Dose equivalent and Directional Dose equivalent are used for the purpose of Environment and area monitoringDefinition: Ambient Dose equivalent, H*(d), at a point in a radiation field, is the dose equivalent that would be produced by the corresponding aligned and expanded field, in the ICRU sphere at a depth d on the radius opposing the direction of the aligned field. H*(d=10) is appropriate for strongly penetrating radiations in environmentIt is similar to Equivalent Dose except that it accounts for absorption and scattering of radiation by the human body.

Radiation Protection Course

15.04.2008Radiation Protection Course*Environmental Monitoring (contd.) Directional dose equivalent, H(d), at a point in the radiation field, is the dose equivalent that would be produced by the corresponding expanded field in the ICRU sphere at depth d on radius in a specified direction.

H(d) is suitable for weekly penetrating radiations in the environmental monitoringThe recommended value of d for penetrating radiation is 10 mm.

Radiation Protection Course

15.04.2008Radiation Protection Course*Important terms

Radiation is therefore considered to be STRONGLY penetrating when the skin dose is lower than ten times the effective dose.

Radiation is considered to be WEAKLY penetrating, when upon normal incidence, the skin dose is higher than ten times the effective dose.

Radiation Protection Course

15.04.2008Radiation Protection Course*Individual Monitoring Hp (10) Individual Dose Equivalent, penetrating, Hp(d= 10), is suitable for organs and tissues deeply situated in the body which will be irradiated by strongly penetrating radiation.Def: Hp(d =10) is the dose equivalent in the soft tissue, defined as in the ICRU sphere below a specified point on the body at depth d that is appropriate for strongly penetrating radiations.

Radiation Protection Course

15.04.2008Radiation Protection Course*Hp (10)How to verify that a personal dosimeter measures Hp(10)? One would have to measure response while the dosimeter is worn on the body. Since volunteers for that purpose are rare, the definition of Hp(10) has been extended to the slab phantom (a square slab dimensioned 300mm x 300mm x 150mm, PMMA walls, filled with water). The slab phantom may also be used to calibrate dosimeters to Hp(10).

Radiation Protection Course

15.04.2008Radiation Protection Course*Individual Monitoring (contd.)Individual Dose equivalent, superfcial, Hs(d = 0.07), is the dose equivalent in soft tissue below a specified point on the body at a depth d that is appropriate for weakly penetrating radiations.It is suitable for superficial tissues or organs which will be irradiated by both weakly and strongly penetrating radiation.Hp(0.07) dosimeters are calibrated on rod phantoms simulating fingers, arms, or legs.

Radiation Protection Course

15.04.2008Radiation Protection Course*ICRU SphereA 30 cm diameter sphere of unit density tissue and composition as specified by ICRU (H, 10.1%; C, 11.1%; N, 2.6%; O, 76.2%; %-compositions are given by weight) was exposed to a parallel particle beam uniformly expanded over its front surfaceThe medium between the source and the ICRU sphere was assumed to be vacuum.

Radiation Protection Course

15.04.2008Radiation Protection Course*In order to obtain the depth-dose distributions along the principal axis of the sphere, the energy deposited has been scored as a function of the depth and radius in an R-Z binning cylindrical structure. Different grids have been selected according to the depth: 0.2 cm longitudinal bins have been considered up to 2 cm, and 1 cm longitudinal bins for larger depths. The radial bin was taken to be 1 cm.

Radiation Protection Course

15.04.2008Radiation Protection Course*ICRU Quantities for Monitoring

Radiation Protection Course

15.04.2008Radiation Protection Course*WORKPLACE MONITORINGWorkplace (area) monitors are primarily intended to provide information on the dose-rates within the working area to permit decisions to be made on its occupancy.

It is necessary to know the dose equivalent rates in the various working areas to assess and control occupational exposure.

Radiation Protection Course

15.04.2008Radiation Protection Course*AREA MONITORING (a) ROUTINEContinuous or periodically surveillance of the radiation level or contaminationDaily, weekly, monthlyIntended to show that working environment is satisfactory for continued operation. No change occur which would call for a review of the operating procedure

Radiation Protection Course

15.04.2008Radiation Protection Course*AREA MONITORING (contd.)(b) OPERATIONALContinuous carried out during a particular operationBefore and after operationTo provide check on particular operation for immediate decision on the conduct of the operation

Radiation Protection Course

15.04.2008Radiation Protection Course*AREA MONITORING (contd.)(c) SPECIALCarried out in case of the occurrence or possibility of abnormal conditionTo obtain information for better control of accident involve

Radiation Protection Course

15.04.2008Radiation Protection Course*

Radiation Protection Course