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Submitted by Marc-Andre Chavy-Macdonald, European Space Agency
   Commenting as an individual
Document Assessment of Radiation Exposure of Astronauts in Space
 

Dear ICRP committee members,

In general, the author wishes to express his approval at the writing of the first ICRP Assessment of Radiation Exposure of Astronauts in Space.  This is a very informative and timely document which will prove very useful in a field where, unfortunately, concepts and terminology may be quite ambiguous.  In addition to the comments which have already been made, the author wishes to comment on the following lines:



Line                Comment 


489-490                It is confusing to be referring to effective dose and equivalent dose in this manner, because these quantities are no longer recommended for space applications.  Recommend inserting “for terrestrial applications”.


848-849                Graph y-axis values to be changed.


891                         Elsewhere (Durante and Cucinotta 2011, etc.) Figure 2.2 has the reference


F. A. Cucinotta, H. Wu, M. R. Shavers, and K. George. Radiation dosimetry and biophysical models of space radiation effects. Gravitational and Space Biology, 16(2):11-18, 2003.


 


901-902                Is this figure with the newest data?  This 2003 graph leads to apparent inconsistencies with newer NASA data (from Table 2.7 on page 30 of NASA/TP-2011-216155). 


1043-1044            Many figures have incorrect legends.


1334                       Effective dose equivalent is also a protection quantity, in fact the recommended one for space, and so should be defined here.  Ideally, it should be contrasted with effective dose, clarifying the difference.  It would perhaps also be helpful to contrast here dose equivalent and equivalent dose.


1402-1404            The previous comment, defining the alternative effective dose equivalent, would help to clarify this obscure point.


1415                       Confusing to have dose equivalent here only, in the “Operational quantities” section, as it is clearly stated on line 156 that no operational quantity is recommended for space.  By recommending the use of the Q(L) function, the ICRP is effectively sanctioning the use of dose equivalent, which has been defined only as an “Operational quantity”.


1432                       The terms “expanded” and “aligned” are not to be found in the Glossary.


1488                       Should specify the time period, as deterministic effects’ limits are over a time period.  If a lifetime value, this should be stated.


1514                       Editorial: increase


1729                       AP incidence should be in the Glossary as Anterior-Posterior.


1980                       See comment on line 1488.  If time is uncertain, “on the order of days”, or similar vague wording would be helpful.


3016                       Citation would be appropriate here.


3017-3018            Citation and argument would be appropriate for this very strong statement.


3055                       This section should be changed to be consistent with the other codes.  The code originates at CERN, and a suite of space applications have been developed by ESA, including GRAS, MULASSIS, SSAT.  GRAS should be cited, MULASSIS should have the correct citation. 


                                MULASSIS citation:


 


F. Lei, P.R. Truscott, C.S. Dyer, B. Quaghebeur, D. Heynderickx, P. Nieminen, H. Evans, and E. Daly. MULASSIS: A Geant4-Based Multilayered Shielding Simulation Tool. IEEE Transactions on Nuclear Science, 49: 2788-2793, December 2002.


 


                                GRAS and SSAT citation:


G. Santin, P. Nieminen, H. Evans, E. Daly, F. Lei, P.R. Truscott, C.S. Dyer, B. Quaghebeur, and D. Heynderickx. New Geant4 based simulation tools for space radiation shielding and effects analysis. Nuclear Physics B, 125:69-74, September 2003.


 


3069-3070            Statement gives the impression that much of the Geant4 code is simply copied from HZETRN and others, and should be softened.  As correctly stated on lines 3058-3059, Geant4 has been developed and is maintained by a large collaboration for many particle physics applications. 


3105                       No Wilson 2009 reference exists.


3301-3302            As dose equivalent cannot be related to current agency dose limits, and is not recommended for use by the present report, it is an odd choice of quantity to be plotting, considering the wealth of alternatives.  Figures 5.9 and 5.10 should be in terms of effective dose equivalent, the recommended quantity for space applications, which changes the shape of the plots significantly.  The use of dose equivalent here also promotes uncertainty as to the recommended quantity.  Excellent NASA figures are available in NASA TM-2012-217361, NASA/TP-2011-216155, or


Martha S. Clowdsley, John W. Wilson, Myung-hee Kim, Brooke M. Anderson, and John E. Nealy. Radiation protection quantities for near earth environments. In AIAA Space 2004 Conference and Exposition, 2004.


 


3312                       This statement cannot be fully verified from Figure 5.9, as the correct approximation to whole-body dose – effective dose equivalent – is not used.


3328                       As in previous point, figures with dose equivalent on the y-axis are misleading in several ways and should be avoided – they cause confusion as to the recommended quantity, and incorrect conclusions about effects of shielding on a complete phantom could be drawn. 


3350                       Paragraph (259).  These statements are true and helpful for trapped radiation and SPEs, but not necessarily for GCRs.  Due to the flatness of dose – depth and effective dose equivalent curves for GCRs, very little geometrical information can be seen.  This point would be obvious if figures 5.9 and 5.10 a) were in the appropriate units.


3363                       The words “effective dose” should be replaced with “effective dose equivalent”, also in several other places in the text.  Great care should be taken to avoid interchanging these terms, especially in this ICRP report.  It is highly recommended that the use of the term “effective dose” be reviewed throughout the document, as its association with dose equivalent vs. equivalent dose remains confusing. 


3363                       A citation is also required here.


3570                       Editorial: the space environment


3571                       Paragraph 278 should be reworded for grammar.  Also, to my knowledge ESA has not adopted these coefficients before a month ago.  The statement “Most space organizations” should then be replaced by “NASA”.  Do you have any evidence that ESA has been using fluence-to-dose equivalent coefficients since the late 1990s?


3394                       It is suggested that it would be extremely helpful to include dose limits of the major space agencies in this section, when publicly available, in their correct units and quantities.  Both short- and long-term limits should be included.  This information is unfortunately difficult to come by and often presented ambiguously, incompletely, or using out-of-date values or units.  As this is the first ICRP report of its kind, precedent has not yet been set as to their presence, and these dose limits are critical for most calculations or measurements.  Their inclusion would thus be highly appropriate; in fact the absence of these critical values would be a grave omission.

Best regards,

Marc-Andre Chavy-Macdonald