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Radiation protection instrumentation and its application
366
Book reviews
special unit rad were still to be assigned solely to the widely used quantity absorbed dose. Part I I of I C R U Report I0 deals with quantities and units for use in radiation protection. In addition to the old quantity dose equivalent, two new quantities absorbed dose index a n d dose equivalent index are included. The dose equivalent is still the product of the absorbed dose, the quality factor, and any other modifying factors. The absorbed dose index at a point is defined as the maximum absorbed dose within a 30-cm diameter tissue-equivalent sphere centered at this point. Similarly the dose equivalent index at a point is defined as the maximum dose equivalent within a 30-era diameter tissue-equivalent sphere centered at this point. These two quantities have been defined to help characterize the ambient radiation levels at any location for purposes of radiation protection. In many radiation protection situations the numerical values of these new quantities may be adequate approximations to the numerical values of the maximum dose equivalent in the human body. The special unit for dose equivalent, when absorbed dose is expressed in fads, is, as before, the rem. The two new quantities absorbed dose index and dose equivalent index also have the special units rad and rem, respectively, since they are defined in terms of absorbed dose and dose equivalent. The need to have a special unit for dose equivalent has never been made clear and the recommendation to continue to use rein in radiation protection does leave room for confusion. In actual practice, the average health physicist frequently uses these units incorrectly. The roentgen, rad and rem are often used interchangeably, ignoring their differences. Since it is the biological effectiveness of absorbed dose that is ultimately important in inferring any effects of radiation, it would have been helpful even at this last stage to delete the use of rein. I C R U Report 19 will probably have little impact on the average radiation physicist. The three widely used radiation quantities exposure, absorbed dose, and dose equivalent have not been changed in any manner. The micro-dosimetric concepts and the concept of stochastic and non-stochastic quantities may prove useful to a small limited group interested in radiation research. However, the entire report is useful reading and a determined effort by all radiation workers strictly to adhere to the definitions and units given therein is strongly recommended. N. SUNTHARALINGAM
R a d i a t i o n P r o t e c t i o n ][nstrum~entatlon a n d Its A p p H c a t i o n ~ I C R U Report 20. International Commission on Radiation Units and Measurements, Washington, D.C. (1972) 60 pp. $3.50. Tins report was prepared to give practical guidance on measurement and interpretation problems faced
by those who use or review the use of ionizing radiation or radioactive materials. The first section is entitled "Basic Considerations", and includes somewhat simplified definitions, neutron fluence rate per unit M A D E rate, the relationship between absorbed dose and kerma, etc. While it may be an improvement in the long term, it is disconcerting to find a number of symbol changes: H is used for dose equivalent, Q for quality factor, etc. One must inquire about the logic which permits: (1) D E changed to H; (2) Dm used for maximum value of absorbed dose; and (3) M A D E for maximum dose equivalent rather than the consistent and more usual designation of maximum by the subscript " m " with the original symbol to produce Hrn ! H m m m ? There are even two terms defined here but " n o t available for use in this report." The remainder of the report consists of sections on instrument characteristics, choice and use of instruments, calibration of instruments, appendixes, etc. The writing of such a report is surely difficult and perhaps impossible to do well in 60 pages. Th e authors are well known and obviously highly qualified. Perhaps they had little enthusiasm for this project and found the reading of this report as difficult as I did, for the report is marred by a number of technical errors which one does not expect in an I C R U Report. It is somewhat astounding to read that "because of the dead-time problem, G-N[ counters should not be used when the count rate is more than a few thousand counts per minute." Compare this with the 80,000 counts per minute which corresponds to 20 m R/ h r on one commercially available instrument! Further, there are numerous commercially G - M counters which do not j am in high fields and only these instruments should be recommended. Similarly astounding is the statement that G - M counters undergo "changes in . . . energy dep e n d e n c e . . , from time to t i m e . . . " There are numerous other errors or debatable statements which cannot be adequately discussed in a review, but brief mention may be of service to the interested reader " . . . it is uneconomical to set up a film badge service for fewer than 200 films per reading cycle." I would place the number at least as high as 2000. Finger badges are not even mentioned. On page 22 we read that shielding of electron accelerators is based on bremsstrahlung which/s true for low energies but for high energies the shielding must be based on high energy neutrons. O n page 23 one reads that unsealed radioactive sources are usually small enough that the hazard from external irradiation of the body can be neglected. In the discussion re charged particle accelerators, the a2C(n, 2n)nC reaction is discussed as though only the (p, pn) reaction competes thus neglecting the (7, n) reaction which in some cases may be responsible for
Book reviews most of the 11C p r o d u c e d . T h e discussion of the b i s m u t h fission r e a c t i o n is similarly deficient. T h e "ill-defined t h r e s h o l d for fission" is m e n t i o n e d . N o t m e n t i o n e d is the fact t h a t the t h r e s h o l d does n o t necessarily refer to neutron cross section. H o w v a l u a b l e is a m e a s u r e m e n t b a s e d o n a r e a c t i o n for w h i c h the n e u t r o n cross section has n o t b e e n m e a s u r e d ? For quite different reasons, b o t h novice a n d expert
367
will h a v e difficulty with this report. T h e effort e x p e n d e d in p r e p a r i n g this r e p o r t m u s t h a v e b e e n s u b s t a n t i a l a n d too v a l u a b l e to waste. A f u r t h e r effort to i m p r o v e this r e p o r t would b e justified. T h i s reviewer hopes the I C R U will see fit to issue a carefully revised edition at the earliest possible date.
~AYMOND C. BARRALL
Book reviews
special unit rad were still to be assigned solely to the widely used quantity absorbed dose. Part I I of I C R U Report I0 deals with quantities and units for use in radiation protection. In addition to the old quantity dose equivalent, two new quantities absorbed dose index a n d dose equivalent index are included. The dose equivalent is still the product of the absorbed dose, the quality factor, and any other modifying factors. The absorbed dose index at a point is defined as the maximum absorbed dose within a 30-cm diameter tissue-equivalent sphere centered at this point. Similarly the dose equivalent index at a point is defined as the maximum dose equivalent within a 30-era diameter tissue-equivalent sphere centered at this point. These two quantities have been defined to help characterize the ambient radiation levels at any location for purposes of radiation protection. In many radiation protection situations the numerical values of these new quantities may be adequate approximations to the numerical values of the maximum dose equivalent in the human body. The special unit for dose equivalent, when absorbed dose is expressed in fads, is, as before, the rem. The two new quantities absorbed dose index and dose equivalent index also have the special units rad and rem, respectively, since they are defined in terms of absorbed dose and dose equivalent. The need to have a special unit for dose equivalent has never been made clear and the recommendation to continue to use rein in radiation protection does leave room for confusion. In actual practice, the average health physicist frequently uses these units incorrectly. The roentgen, rad and rem are often used interchangeably, ignoring their differences. Since it is the biological effectiveness of absorbed dose that is ultimately important in inferring any effects of radiation, it would have been helpful even at this last stage to delete the use of rein. I C R U Report 19 will probably have little impact on the average radiation physicist. The three widely used radiation quantities exposure, absorbed dose, and dose equivalent have not been changed in any manner. The micro-dosimetric concepts and the concept of stochastic and non-stochastic quantities may prove useful to a small limited group interested in radiation research. However, the entire report is useful reading and a determined effort by all radiation workers strictly to adhere to the definitions and units given therein is strongly recommended. N. SUNTHARALINGAM
R a d i a t i o n P r o t e c t i o n ][nstrum~entatlon a n d Its A p p H c a t i o n ~ I C R U Report 20. International Commission on Radiation Units and Measurements, Washington, D.C. (1972) 60 pp. $3.50. Tins report was prepared to give practical guidance on measurement and interpretation problems faced
by those who use or review the use of ionizing radiation or radioactive materials. The first section is entitled "Basic Considerations", and includes somewhat simplified definitions, neutron fluence rate per unit M A D E rate, the relationship between absorbed dose and kerma, etc. While it may be an improvement in the long term, it is disconcerting to find a number of symbol changes: H is used for dose equivalent, Q for quality factor, etc. One must inquire about the logic which permits: (1) D E changed to H; (2) Dm used for maximum value of absorbed dose; and (3) M A D E for maximum dose equivalent rather than the consistent and more usual designation of maximum by the subscript " m " with the original symbol to produce Hrn ! H m m m ? There are even two terms defined here but " n o t available for use in this report." The remainder of the report consists of sections on instrument characteristics, choice and use of instruments, calibration of instruments, appendixes, etc. The writing of such a report is surely difficult and perhaps impossible to do well in 60 pages. Th e authors are well known and obviously highly qualified. Perhaps they had little enthusiasm for this project and found the reading of this report as difficult as I did, for the report is marred by a number of technical errors which one does not expect in an I C R U Report. It is somewhat astounding to read that "because of the dead-time problem, G-N[ counters should not be used when the count rate is more than a few thousand counts per minute." Compare this with the 80,000 counts per minute which corresponds to 20 m R/ h r on one commercially available instrument! Further, there are numerous commercially G - M counters which do not j am in high fields and only these instruments should be recommended. Similarly astounding is the statement that G - M counters undergo "changes in . . . energy dep e n d e n c e . . , from time to t i m e . . . " There are numerous other errors or debatable statements which cannot be adequately discussed in a review, but brief mention may be of service to the interested reader " . . . it is uneconomical to set up a film badge service for fewer than 200 films per reading cycle." I would place the number at least as high as 2000. Finger badges are not even mentioned. On page 22 we read that shielding of electron accelerators is based on bremsstrahlung which/s true for low energies but for high energies the shielding must be based on high energy neutrons. O n page 23 one reads that unsealed radioactive sources are usually small enough that the hazard from external irradiation of the body can be neglected. In the discussion re charged particle accelerators, the a2C(n, 2n)nC reaction is discussed as though only the (p, pn) reaction competes thus neglecting the (7, n) reaction which in some cases may be responsible for
Book reviews most of the 11C p r o d u c e d . T h e discussion of the b i s m u t h fission r e a c t i o n is similarly deficient. T h e "ill-defined t h r e s h o l d for fission" is m e n t i o n e d . N o t m e n t i o n e d is the fact t h a t the t h r e s h o l d does n o t necessarily refer to neutron cross section. H o w v a l u a b l e is a m e a s u r e m e n t b a s e d o n a r e a c t i o n for w h i c h the n e u t r o n cross section has n o t b e e n m e a s u r e d ? For quite different reasons, b o t h novice a n d expert
367
will h a v e difficulty with this report. T h e effort e x p e n d e d in p r e p a r i n g this r e p o r t m u s t h a v e b e e n s u b s t a n t i a l a n d too v a l u a b l e to waste. A f u r t h e r effort to i m p r o v e this r e p o r t would b e justified. T h i s reviewer hopes the I C R U will see fit to issue a carefully revised edition at the earliest possible date.
~AYMOND C. BARRALL