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RE: Increased NRC dose limits for hot particles - unproductive doses
Dr. Charles:
I very much appreciate your recent comments on the forthcoming rulemaking by
NRC on discrete radioactive particles. In response to a question in your
remarks, I offer the following:
The study of unproductive dose that was referred to in the SECY was
documented in an EPRI research report. I was one of the two principal
investigators that conducted the study. The study included three sites,
each with two reactor units. One site has experienced discrete radioactive
particles (DRPs) routinely at both units; one site has experienced DRPs
routinely at one unit and only infrequently at the other; and one site has
had little experience with DRPs at either unit.
The study was intended to characterize, not quantitatively define, the
impacts associated with strict compliance with the current NRC regulatory
limit of 50 rem shallow dose equivalent (i.e., DRPs are currently treated in
NRC regulation as analogous to skin dose). The 3-5 rem of unproductive dose
among 15-25 workers represented the upper range each per fuel cycle for the
three units (at two sites) that routinely experience DRPs. Note that 3-5
rem at these plants (all PWRs) represents about 1-4% of the overall
collective dose received during refueling outages at those sites.
The dose was primarily associated with intermittent surveys of radiation
workers and work areas performed in the reactor cavities by radiation
protection technicians. The surveys were performed "in-situ" rather than
having the workers break frequently and come up out of the reactor cavity
due to (1) the excess dose that would have been accrued due to frequent
stopping and starting of work activities, (2) additional physical risk
(cardio-vascular stress or from falling) associated with frequently climbing
out of and back into the reactor cavityin full PCs, and loss of
critical-path time -i.e., it was not ALARA to do so.
The primary purpose of the surveys is to assure and demonstrate compliance
with the 50 rem limit by detecting high-activity DRPs in reduced time-frames
sufficient to prevent the possibility of a DRP on or near the skin for a
duration that could cause the potential (estimated) exposure to exceed the
50 rem limit.
I can provide you with more information upon request.
Personal observation: I've had the opportunity to consult closely with Drs.
John Baum (BNL) and Dan Reece (Texas A&M) regarding their studies of effects
on swine skin from DRP exposure, in addition to previously having been a
radiation protection manager/supervisor at NPPs for many years prior to
coming to my present position. I believe a more apt analogy for comparison
of effective dose equivalent (we're still on ICRP 30) and DRP exposure might
be a cannonball and a beebee, rather than an apple and an orange. The
rulemaking being considered by NRC will likely track the forthcoming NCRP
report on the DRP topic, and, when promulgated, it should provide better
flexibility for radiation protection staff to control real dose to real
people, than does the current regulation. But that's only my opinion.
Regards,
Ralph L. Andersen, CHP
Senior Project Manager
Nuclear Energy Institute
1776 Eye Street, NW
Washington, DC 20006-3708
Phone: 202-739-8111
E-mail: rla@nei.org
> ----------
> From: Monty Charles[SMTP:charlemw@novell1.bham.ac.uk]
> Reply To: m.w.charles@bham.ac.uk
> Sent: Thursday, February 18, 1999 12:40 PM
> To: radsafe@romulus.ehs.uiuc.edu; powernet@support.net
> Cc: P.J.Darley@bham.ac.uk; M.W.Charles@bham.ac.uk
> Subject: Increased NRC dose limits for hot particles - unproductive
> doses
>
>
> The NRC appears to have taken a decision to increase the dose limit
> for skin exposure to hot particles (DRPs)- information circulated by
> Mike Russell on powernet, 12 January 1999. One of the arguments for
> doing this is that the current restrictions lead to increased whole
> body doses. The stochastic risk of these whole body doses are
> considered to be unacceptable in view of the supposed low level of
> detriment from a deterministic lesion of the skin. This seems to be
> a valid argument but of course it is difficult to compare
> stochastic risks with deterministic effects (apples and oranges). I
> have not seen any quantitative arguments to support this view. The
> only related quantitative information is that some EPRI information
> can be interpreted as implying that current DRP limits give rise to
> unproductive collective doses of 3-5 person rems per outage per
> site (information to the NRC Commissioners from William D Travers, 23
> October 1998, SECY-98-245).
>
> Does anyone have any information which can substantiate values of
> unproductive dose. It is also necessary to know individual
> doses for those workers most exposed to potential high DRP doses- so
> how many workers are likely to share the 3-5 person rems which are
> incurred unproductively.
>
> Thanks for your time
>
> Monty Charles
> Dr Monty Charles
> Reader in Radiation Physics
> School of Physics & Astronomy
> University of Birmingham
> Edgbaston
> Birmingham B15 2TT
> United Kingdom
> ----------
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