Re: Anyone hear of "flawed rad detectors"...

[DWhitfil@kdhe.state.ks.us]

No doubt that neutron and beta dosimetry is challenging. NUREG/CR-2956,
Neutron Dosimetry at Commercial Nuclear Plants (Final Report of Subtask B:
Dosimeter Response), by Cummings, Endres, and Brackenbush, 1983 is a very
interesting.

Part of the abstract:

"The most precise (reproducible) dosimeters for the irradiations were the
TLD-albedos. Of those, two dosimeters were in reasonable agreement with the
SNOOPY remmeter: a TLD-albedo dosimeter calibrated using a D_2O-moderated
252Cf source and the Hankins dosimeter calibrated according to the 9 in. to
3 in. sphere ratios. None of the dosimeters exhibited an accurate
dosimetric response compared to TEPC measurements."

It may be time to do another study, but I would be surprised if any major
improvements in commercial neutron dosimetry have occurred due to the
simple fact that there is no economic incentive to do so. Commercial power
plants generally do not need neutron monitoring by dosimeter, and the few
accelerators and research labs that do monitor for neutrons probably do not
represent a large enough economic base to recover any investment. Probably
the slickest development has been bubble dosimetry, but you will not find
it listed under any major commercial dosimetry vendor's NVLAP certification
(see  http://ts.nist.gov/ts/htdocs/210/214/214.htm).

Another point of contention is the flux-to-dose equivalent conversion
factors: which ones to use? The NRC did not advocate incorporating the
factor of two increase in the quality factor for neutrons recommended in
1985. The NRC considers neutron exposures at most of their licensed
facilities to be small, and foresee no major health or regulatory impact by
deferring the recommended increase in the quality factor until a greater
scientific consensus is reached on a suitable value. Other references refer
to the proliferation of conversion factors as deplorable (NBS Special
Publication 633, by Eisenhauer and Schwartz, 1982) and results in ambiguity
and inaccuracies (Comparison of Neutron Dosimetric Quantities, by C.S.
Sims, Health Physics 54, page 551).

In a sense we are responsible for some misconceptions due to a lack of a
unified front between various scientific agencies and regulatory
authorities. Maybe behind every myth is a hint of truth.

Here is an interesting link:

http://www.rerf.or.jp/eigo/rerfupda/dosphysi/straume.htm

(Neutron Discrepancies in the Dosimetry System 1986 Have Implications
for Radiation Risk Estimates

Evidence for higher-than-predicted neutron exposures in Hiroshima raises
some vexing questions.

by Tore Straume, Lawrence Livermore National Laboratory, University of
California, Livermore, California)

Of course the proliferation of material on the web is a bit vexing, as much
of the information may not be up to date or accurate.

DJWhitfill

Opinions expressed are mine and do not reflect official policies or
positions of the Kansas Department of Health and Environment.

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