RE: Units for Criticality Accident

[David_S_Hyder@RL.gov]

Bruce,

I absolutely agree with you.  However, I still have not seen any data on
how the workers dose was determined.  I doubt that personal nuclear
accident dosimetry was worn as a criticality accident was determined to
be a "non-credible" event.  The workers dosimetry may have been read
but, was a suitable algorithm available, based on the neutron energies
of this "non-credible" event.  I assumed that the doctors are basing the
dose estimate on the physical state of their patients (i.e. blood
chemistry).  The doctors may have done the same as I did on Thursday,
referenced a chart based on onset of symptoms.

I'm not an expert, could the doctors use the sodium activation in the
patients blood, corrected for decay, to determine the neutron flux and
thus determine neutron dose?

I'm just glad that I'm getting some information, I would imagine that
the stress level is pretty high over there right now.  The final report
should get the numbers and units correct.

David Hyder
David_S_Hyder@rl.gov
Health Physicist
Hanford Facility Evaluation Board

> -----Original Message-----
> From:	Heinmiller, Bruce [SMTP:heinmillerb@aecl.ca]
> Sent:	Wednesday, October 06, 1999 9:24 AM
> To:	Multiple recipients of list
> Subject:	RE: S.Korea Launches Probe Into Nuclear Accident
> 
> Correct!  See my 10:40 Oct 1 posting.
> 
> A quoted dose of, say, 10 Sv is ambiguous, because no quantity is
> specified.
> If it was derived from biological dosimetry and represents the
> estimated
> corresponding low-LET dose (10 Gy or 10 Sv) that would have caused the
> observed effects noted, then the prognosis is poor.  On the other
> hand, if
> it represents the true (but inappropriately used) dose equivalent, and
> supposing equal absorbed doses from neutrons and photons (a plausible
> scenario), then the absorbed dose of each would be slightly under 1 Gy
> if a
> quality factor of 10 had been applied to the neutron absorbed dose.
> If
> neutrons are 2 to 3 times as effective for producing the acute effects
> of
> concern, then it would look to the body like a total low-LET dose of
> about 3
> Gy, and the prognosis would be much better.
> 
> Also, here's what ICRU, ICRP, and IAEA have to say about the use of
> dose
> equivalent quantities for high-dose exposures, particular where
> neutrons are
> involved.  I've extracted this from an off-list question that I
> replied to
> earlier.
> 
> For example, ICRU Report 51 states that the quality factor "is
> formulated to
> take account of the relative effectiveness of the different types of
> ionizing radiations at the low exposure levels encountered in routine
> radiation protection practice."
> 
> And ICRP, in Publication 60, states:  "The equivalent dose is not
> always the
> appropriate quantity for use in relation to deterministic effects
> because
> the values of radiation weighting factors have been chosen to reflect
> the
> RBE of the different types and energies of radiation in producing
> stochastic
> effects.  For radiations with a weighting factor greater than 1, the
> values
> of RBE for deterministic effects are smaller than those for stochastic
> effects.  The use of the equivalent dose to predict deterministic
> effects
> for high LET radiations, e.g. neutrons, will thus lead to
> overestimates."
> 
> IAEA in Technical Report Series No. 211 states:  "The dose equivalent
> is
> limited to radiation protection applications and may be used to
> compare
> values of H with the applicable values of the dose equivalent limit.
> It
> should not be used in assessing the effects of high-level, accidental
> exposures such as may be sustained during criticality accidents."  And
> in
> another section:  "In nuclear accidents acute biological effects are
> predominant and, as was stated earlier, the quality factors needed to
> estimate dose equivalent are no longer valid.  In this case neutron
> doses
> should be given in gray (Gy)...".
> 
> With respect to the question of the inappropriateness of using Sv
> instead of
> Gy for criticality accident dosimetry, I'll defer to ICRU, ICRP, and
> IAEA.
> Can we put this one to rest now, and stop talking Sv (or rem) in cases
> where
> the units have no relevance?
> 
> And does anyone know what the latest estimates are for the doses (in
> relevant quantities) these workers got?  That is, the neutron absorbed
> doses
> and the photon absorbed doses?
> 
> Bruce Heinmiller CHP
> heinmillerb@aecl.ca
> 
> 
> > ----------
> > From: 	Carroll,Raymond[SMTP:carrollrg@pgdp.usec.com]
> > Reply To: 	radsafe@romulus.ehs.uiuc.edu
> > Sent: 	Wednesday, October 06, 1999 11:18 AM
> > To: 	Multiple recipients of list
> > Subject: 	RE: S.Korea Launches Probe Into Nuclear Accident
> > 
> > One other little tid bit.  Quality factors are not applicable for
> high
> > acute
> > doses of radiation.  For more information you might want to research
> the
> > NCRP and ICRP documents.
> > 
> > Ray Carroll
> > carrollrg@pgdp.usec.com
> > ___________________________________________________
> > 
> > -----Original Message-----
> > From: Michael McNaughton [mailto:mcnaught@lanl.gov]
> > Sent: Wednesday, October 06, 1999 10:09 AM
> > To: Multiple recipients of list
> > Subject: Re: S.Korea Launches Probe Into Nuclear Accident
> > 
> > 
> > The LD50/60 is normally quoted in Gy, not Sv.
> > 
> > Assuming Hisashi Ouchi received 1.7 SV, and assuming a neutron
> quality
> > factor of 10, one might guesstimate this is about 0.15 Gy gamma and
> 0.15
> > Gy
> > neutron. Would you expect this to be a fatal dose?
> > 
> > At 09:44 AM 10/6/99 -0500, you wrote:
> > >It is unfortunate when even we in the nuclear industry confuse dose
> 
> > >limits from a regulatory perspective with what is considered to be 
> > >"safe". And how does one define safe anyway? This article refers to
> 
> > >the 600 rem as being a fatal dose. Yet we have 2 Japanese workers 
> > >still alive, yet very ill, receiving doses approaching 1700 rem, or
> 
> > >higher. Statements such as quoted in this article, and in others
> from 
> > >our profession only do harm. These statements do not take into 
> > >account medical intervention, which significantly increases an 
> > >individual's chances of surviving extremely high doses.
> > 
> >
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