You're absolutely correct. The quantities of interest are the neutron absorbed dose in Gy and the photon absorbed dose in Gy. Neutrons are more effective than photons in causing deterministic detriment, but by factors very much less than suggested by the stochastic weighting factors used to convert absorbed dose to equivalent dose. Put another way, an acute whole-body equivalent dose of 8 Sv from photons would almost always be fatal. An acute equivalent dose of 8 Sv from fast neutrons (an inappropriate quantity for acute exposures) would almost never be fatal, because (ignoring differences in radiation transport through the body) the absorbed dose is 10 or 20 times less, depending on the stochastic weighting factors implied in the (inappropriate) use of units used for quantities used to express stochastic detriment. What may have been meant in the reports was that, for the markers looked at, the dose was the equivalent of a photon dose of so many Sv, which would be the same absorbed dose in Gy, assuming photons. But this was not stated.
Bruce Heinmiller
heinmillerb@aecl.ca
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From: Christoph_Hofmeyr/CNS1@cns.co.za[SMTP:Christoph_Hofmeyr/CNS1@cns.co.za]
Reply To: radsafe@romulus.ehs.uiuc.edu
Sent: Friday, October 01, 1999 9:55 AM
To: Multiple recipients of list
Subject: Re: Units of high dose
Radsafers,
The Japanese criticality accident which has been filling the headlines, has
apparently caused severe radiation injury to a few workers. Possible doses
received have been reported in Sievert. The question I would like to pose
to the experts: in the dose range where deterministic effects are
prevalent, is it not more correct to measure in Gray?
Chris Hofmeyr
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