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Comments concerning the draft ICRP Report on "Assessment of Radiation Exposure of Astronauts in Space" , ICRP ref 4819-7515-1888, 2012 July 03
Dear ICRP Secretary, dear Günther Dietze, dear collegues,
this draft report contains a treasure of valuable information, collected in a very commendable effort of your working group. However, there is a problem with quantities and units, which I will point out and for which I will propose a solution. This will perhaps lead to some further committee work towards an updated version of the report.
1) Concerns about the stability of the ICRP terminology on quantities and units In the present, worldwide used ICRP terminology (ICRP 103) the equivalent dose in an organ or tissue due to radiation type R is defined as H where w However, in the corresponding definition of H H where Q Sorry to say, but this means no less than a violation of the principle that the ICRP terminology should be stable over the years as far as possible. Firstly, since H Secondly, the principle that the ICRP terminology should be stable over the years is also violated insofar as in eq. (2) ICRP's "radiation weighting factor" w To sum up, it must be criticised that this report, otherwise treating successfully a demanding subject, presents a confusing terminology and deviates from the worldwide accepted eq. (1). 2) A proposal for improvement According to present knowledge, it should be possible to maintain the basic equation eq. (1) and to introduce w As shown in Fig. 3.14, NASA (Cuccinotta, 2011) have proposed continuous functions Q Steps a) and b) require the full knowledge of the data basis of Fig. 3.14. However I can supply a little contribution to step c). Based on well-known particle track structure and target conformation models let me suggest a formula whose core is the probability 1-e I have tested the applicability of a variant of this formula to describe function Q(L) which I have simply obtained by adding the Q Q(L) = 2 + a [1 - e Here 2 is the asymptotic Q(L) value for L→0, factor a determines the amplitude of the variable term, factor b performs a shift along the L scale so that the maximum of the formula can be made to coincide with the maximum of the biological Q(L) data, exponent c serves to fit the steepness of the initial curve wing, which is (bL) [The attached hand-drawn plots show that this simple formula is well suited to reproduce the Q(L) = Q Tab.1. Coefficients for use with eq. (3)
As said before in remarks a) and b), these Q(L) = Q Hoping that this letter may contribute to a turnover in this report of the Q(L) terminology to the w I remain with kindest regards, Dietrich Harder. |