[ RadSafe ] More questions about 10CFR 20
wlipton at sbcglobal.net
Tue Jun 3 13:41:37 CDT 2008
NOTE: The best source of answers regarding interpreting 10 CFR 20, is found in: "Consolidated Guidance: 10 CFR Part 20 - Standards for Protection Against Radiation (NUREG-1736)". This is available from the NRC web site: www.nrc.gov . From the home page, click on the "Electronic Reading Room" tab, and then on "Collections of Documents By Type." From there, go to the NUREG publications.
As I mentioned in my response to your previous post, the effective limits for nuclear power plants are significantly lower than those of 10 CFR 20.1302. There are tiers of limits. Some apply to the maximum dose at the site boundary. Others apply to the maximum exposure to a real person.
Nuclear power plant licensing requires a detailed, site specific assessment of the offsite doses due to reactor operation. This assessment is summarized in the plant's "Final Safety Analysis Report," and results in an "Offsite Dose Calculation Manual" (ODCM), which has site specific equations for determining offsite doses, based on effluent monitor readings, and for determining the alarm setpoints for these monitors. In general, PWRs use real time meteorological data, since they can control when gaseous effluents are released. The gaseous effluent volumes for BWRs, however, do not permit their storage, requiring continuous releases. Thus, BWRs generally apply a conservative annual average of meteorological parameter values. A nuclear power plant is required to perform an annual "land use census," to determine the critical pathways for populations exposure to gaseous and liquid effluents, and to revise the ODCM if there is a significant change
to a critical pathway.
I recommend looking at the following NRC Regulatory Guides: 1.21, 1.23, 1.109, 1.111., 1.112, 1.113. These are also available from the NRC web site: www. nrc.gov. From the home page, click on the "Electronic Reading Room" tab, and then on "Collections of Documents By Type." From there, go to the Regulatory Guides.
It's not about dose, it's about trust.
----- Original Message ----
From: Sandra Matzkin <matzkin at invap.com.ar>
To: radsafe at radlab.nl
Sent: Tuesday, June 3, 2008 12:31:54 PM
Subject: [ RadSafe ] More questions about 10CFR 20
I'm now fighting with Section 20.1302 (Compliance
with dose limits for individual members of the
public) of 10CFR 20. I have some questions
concerning the possible ways of demonstrating
compliance with the dose limits for individual
members of the public. Quoting again:
(b) A licensee shall show compliance with the
annual dose limit in § 20.1301 by--
(1) Demonstrating by measurement or calculation
that the total effective dose equivalent to the
individual likely to receive the highest dose
from the licensed operation does not exceed the annual dose limit; or
(2) Demonstrating that--
(i) The annual average concentrations of
radioactive material released in gaseous and
liquid effluents at the boundary of the
unrestricted area do not exceed the values
specified in table 2 of appendix B to part 20; and
(ii) If an individual were continuously present
in an unrestricted area, the dose from external
sources would not exceed 0.002 rem (0.02 mSv) in
an hour and 0.05 rem (0.5 mSv) in a year.
Option (2) seems pretty strightforward. However,
I wonder about option (1) since it looks more
like the approach set by the Argentinean
regulatory body. When applying for a license, the
applicant has to assess the allowable activity
for each individual radionuclide (Ki) to be
released (as if radionuclide "i" was the only one
to be released) and demonstrate that the
summation -over all radionuclides released- of
the ratios Si/Ki, where Si is each of the
individual activities to be released, is lower
than or equal to 1. That is, SUM(Si/Ki) < 1.
This formula ensures that the total effective
dose equivalent to the critical group will be
within prescribed limits. The Ki's are calculated
through a long process which requires many data:
meteorological, hydrological, agricultural,
population distribution, even food consumption
habits of the people living in the region, as
well as dosimetric factors associated to each radionuclide.
And now the questions:
a) which is the customary approach to demonstrate
compliance with dose limits to the public when
applying for the licensing of a nuclear (not power) facility in the USA?
b) when (or if) option (1) is used, is the
procedure similar to what I've described above?
if so, which is the official -if there is one-
source for the dosimetric factors? I've searched
through the NRC site but didn't find anything related.
Sorry for the long post. Once again, I'll appreciate your inputs.
Nuclear Engineering Department
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