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Radiation quantities and units
Imernuthmal Jourmd ~![ Applied Radi,aion and I.sotopes Vol 32. pp. 191 tl~ 192 Pergamon Press Ltd 1981 Printed in Great Britain
BOOK REVIEWS Radiation Quantities and Units, ICRU Report 33. ICRU Publications, P.O. Box 30165, Washington, DC 20014, U.S.A. (15 April 1980). This document is a revision and expansion of ICRU Report 19 and ICRU Report 19S (issued 1 July 1971 and 1 September 1973, respectively), dealing with the same general subject -definitions of quantities and units used in the measurement of ionizing radiation and radiation protection. As a revision of previously distributed documents, this report has had the benefit of comments of readers who have made use of the earlier documents, An expanded introduction including the definition of certain general terms and a clearer depiction of the relationship between quantities are no doubt based upon such a review. For example, the 27 definitions of quantities contained in ICRU Report 19 have been rearranged in logical sequence into 4 generic categories dealing with: (A) R a d i o m e t r y - - t e r m s associated with particle number, N, and particle energy, R (B) Interaction coefficients~ependent upon cross sections. An explicit formula for the mass energy transfer coefficient, ll,~/p, for neutrons, as well as that for photons, is exhibited (C) Dosimetry--quantities related to energy transfer, generally formed by the product of the quantities of (A) and (B) (D) Radioactivity where the more precise definition of activity, A, is given. This definition includes the concept of spontaneous transitions from a particular energy state introduced in NCRP Report No. 5~ 11978) In the second part of the publication, quantities and units in use in radiation protection are presented. Section II, "Dose Equivalent" is based on the modifications of Report 19 already made in Report 19S. Interestingly, the table listing the quality factor, Q, as a function of the linear energy transfer, L~, is no longer explicitly given and instead reference is made to ICRP Publication 26 {1977). Perhaps the most significant change between this document and its predecessors is the integral use of the special names for radiation quantities of the Systbme
lnternationale di'Unitds ($I), Beginning in 1975. organizations such as ICRU were instrumental in convincing the General Conference on Weights and Measures on the desirability of introducing special names for the derived SI units associated with radiation protection, replacing those units which are not coherent with $I. Table 1 is based on a report of the Consultative Committee for Units, listing those units which are to be used for the quantity specified, The last column of Table I lists the values of the S! units in terms of the commonly used u n i t s - - t h e curie (Ci), the r6ntgen (R), the rad and the rem. (There is no special name for the $I unit of exposure.) These units appear in the official SI booklet in the category "Units in use temporarily with the $I", ICRU Report 33 recommends that their use be phased out by 1985 and that they be replaced by the appropriate SI units, Whether or not this will occur is clearly dependent upon the recognition by the practitioners in the field of the desirability for this course of action and, I should hasten to add, by the reinforcement of editors ot the utilization of SI units in papers published in the major journals of the field. This publication presents a set of definitions of quantities used in the field of radiation measurements, Based as it is upon previous documents, it is likely to serve both those knowledgeable in the field and those others who need an explanation of the meaning of radiation terms, though its mathematical notation does restrict the latter group. This reviewer has indeed used ICRU reports such as this in the preparation of technical glossaries. The changes incorporated in this report demonstrate that. as our scientific understanding increases, our measurement language must and can change accordingly. Finally, the use of SI units as the primary system of units should ease the transition from customary to SI by demonstrating the coherence of the radiation measurement units with other physical units, DAVID T. GOLDMAN National Bureau (2/'Standards Washinyton, D.C.
TABLE 1. SI units
Quantity Activity (of a radionuclidej Exposure Absorbed dose, specific energy imparted, kerma, absorbed dose index Dose equivalent, dose equivalent index
Expression in other $I units
Expression in $I base units
Expression in other units
Bq
-Ckg -t
s-l A s k g -l
1 Ci = 3.7 x 10 I° Bq I R = 2.58 x 10 4 C k g - t
gray
Gy
J kg- l
m2s 2
10 2 rad
sievert
Sv
Jkg
m 2s 2
10 2 rem
Name
Symbol
becquerel --
191
J
BOOK REVIEWS Radiation Quantities and Units, ICRU Report 33. ICRU Publications, P.O. Box 30165, Washington, DC 20014, U.S.A. (15 April 1980). This document is a revision and expansion of ICRU Report 19 and ICRU Report 19S (issued 1 July 1971 and 1 September 1973, respectively), dealing with the same general subject -definitions of quantities and units used in the measurement of ionizing radiation and radiation protection. As a revision of previously distributed documents, this report has had the benefit of comments of readers who have made use of the earlier documents, An expanded introduction including the definition of certain general terms and a clearer depiction of the relationship between quantities are no doubt based upon such a review. For example, the 27 definitions of quantities contained in ICRU Report 19 have been rearranged in logical sequence into 4 generic categories dealing with: (A) R a d i o m e t r y - - t e r m s associated with particle number, N, and particle energy, R (B) Interaction coefficients~ependent upon cross sections. An explicit formula for the mass energy transfer coefficient, ll,~/p, for neutrons, as well as that for photons, is exhibited (C) Dosimetry--quantities related to energy transfer, generally formed by the product of the quantities of (A) and (B) (D) Radioactivity where the more precise definition of activity, A, is given. This definition includes the concept of spontaneous transitions from a particular energy state introduced in NCRP Report No. 5~ 11978) In the second part of the publication, quantities and units in use in radiation protection are presented. Section II, "Dose Equivalent" is based on the modifications of Report 19 already made in Report 19S. Interestingly, the table listing the quality factor, Q, as a function of the linear energy transfer, L~, is no longer explicitly given and instead reference is made to ICRP Publication 26 {1977). Perhaps the most significant change between this document and its predecessors is the integral use of the special names for radiation quantities of the Systbme
lnternationale di'Unitds ($I), Beginning in 1975. organizations such as ICRU were instrumental in convincing the General Conference on Weights and Measures on the desirability of introducing special names for the derived SI units associated with radiation protection, replacing those units which are not coherent with $I. Table 1 is based on a report of the Consultative Committee for Units, listing those units which are to be used for the quantity specified, The last column of Table I lists the values of the S! units in terms of the commonly used u n i t s - - t h e curie (Ci), the r6ntgen (R), the rad and the rem. (There is no special name for the $I unit of exposure.) These units appear in the official SI booklet in the category "Units in use temporarily with the $I", ICRU Report 33 recommends that their use be phased out by 1985 and that they be replaced by the appropriate SI units, Whether or not this will occur is clearly dependent upon the recognition by the practitioners in the field of the desirability for this course of action and, I should hasten to add, by the reinforcement of editors ot the utilization of SI units in papers published in the major journals of the field. This publication presents a set of definitions of quantities used in the field of radiation measurements, Based as it is upon previous documents, it is likely to serve both those knowledgeable in the field and those others who need an explanation of the meaning of radiation terms, though its mathematical notation does restrict the latter group. This reviewer has indeed used ICRU reports such as this in the preparation of technical glossaries. The changes incorporated in this report demonstrate that. as our scientific understanding increases, our measurement language must and can change accordingly. Finally, the use of SI units as the primary system of units should ease the transition from customary to SI by demonstrating the coherence of the radiation measurement units with other physical units, DAVID T. GOLDMAN National Bureau (2/'Standards Washinyton, D.C.
TABLE 1. SI units
Quantity Activity (of a radionuclidej Exposure Absorbed dose, specific energy imparted, kerma, absorbed dose index Dose equivalent, dose equivalent index
Expression in other $I units
Expression in $I base units
Expression in other units
Bq
-Ckg -t
s-l A s k g -l
1 Ci = 3.7 x 10 I° Bq I R = 2.58 x 10 4 C k g - t
gray
Gy
J kg- l
m2s 2
10 2 rad
sievert
Sv
Jkg
m 2s 2
10 2 rem
Name
Symbol
becquerel --
191
J