ML19263C284
| ML19263C284 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 02/05/1979 |
| From: | Moody D Maine Yankee |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| WMY-79-8, NUDOCS 7902130189 | |
| Download: ML19263C284 (2) | |
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W.Y 79-8 February 5, 1979 United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention: Office of Nuclear Reactor Regulation Robert W. Reid, Chief Operating Reactors Branch No. 4 Division of Operating Reactors
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b) Letter from USNRC to MYAPC dated January 17, 1977 (c) Letter from MYAPC to USNPC dated March 18, 1977 (d) Letter from USNRC to MYAPC dated November 30, 1978, (e) John N. Ramswi, "SKIRON: A Computer Code for Determining Atmospheric Dispersion Conditions for Design Basis Accident Evaluations," Yankee Atomic Electric Company, Technical Report, YAEC-ll38, October 1977 (f) Regulatory Guide 1.XXX, " Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants," U. S. Nuclear Regulatory Commission, October 1978
Dear Sir:
Subject:
- r. valuation of the Radiological Consequences of a Postulated Spent Fuel Handling Accident Inside Containment Reference (b) requested Maine Yankee to evaluate the radiological consequences of a postulated spent fuel handling accident within the containment of the Maine Yankee Atomic Power Station. The criteria specified in Reference (b) required that the resultant dose be well within the exposure guidelines of 10CFR100 (i.e., 500 rem to the thyroid and 25 rem whole body). Reference (c) responded to this request and pro rided the results of an analysis showing that the resultan'. dose to the thyroid at the site boundary wss 170 rem and the whole body dose as being 4 rem.
This analysis and results were based on the unrealistic assumption that the radioactivity released as a result of the fuel handling accident, instantaneously reached the dose evaluation point with no credit for containment isolction, iodine filtration or mixing within the containment.
Reference (d) acknowledged the methodology and assumptions used in Reference (c), but now requested we propose additional Technical Specifica-tions to meet an arbitrarily selected criteria of 100 rem thyroid dose.
Following telephone conversations with members of your staff, the Maine Yankee Containment Fuel Handling Accident Analysis (Reference c) was revised to include the most current meteorological data available.
Adol.5 790mo m
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,5 United States Nuclear Regulatory Commission February 5, 1979 Att: Office of Nuclear Reac Mr Regulation Page 2 The one hour accident X/Q, 5.26E is used for the worst receptor at the Exclusion Area boundary (EAB) and was computed using SKIRON (Reference
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e) a Yankee Atomic computer code based on the latest version of Draft Regulatory Guide 1.XXX (Reference f).
The meteorological data used to compute the accident X/Q is based on the January to December 1977 operating period. The probability that this X/Q value can be exceeded is only 0.5 percent of the total time, or equivalently, only 8.5 percent of the time during which the wind actually blows into the critical sector.
Based on this new X/Q value, the EAB thyroid dose given in Reference (c) has been recalculated to be 114 rem, and is well below the exposure guidelines of 10CFR100 (300 rem thyroid) despite the extreme conservatism of the analysis which takes no credit for any centainment isolation, i'line filtration or mixing within the containment. Even without a containment building, the doses calculat3d using the conservative assumptions of Pegulatory Guide 1.25 are within the limits of 10CFR100 as required.
Therefore, additional requirements to specify isolation times fcr various containment penetrations as suggested in Reference (d) are unnecessary to fulfill the regulations.
It is relevant to observe that the 100 rem thyroid dose limit suggested in Reference (d) is more conservative than the requirement set forth in 10CFR100.ll(2). The Standard Review Plan, Section 15.74, r2 quires that "The dose to an individual from a postulated fuel handling accident should be well within 10CFR Part 100 exposure guidelinas." Assuming for a moment that the SRP is applicable for assessment of an operating plant (which it is not), the limit presented in Reference (d) is apparently a staff interpretation for the "... well within." Under conditions where the staff interpretation of a conservative limit is two-thirds less than required by regulation, a calculated dose of 114 rem is virtually equivalent and both regulation and the staff's extremely conservative limit are satisficJ.
Since the calculated dose of 114 rem is determined without the acenorledged reduction factors afforded by the containment, there is absolutely no reason, in our estimation, to propose additienal tech-nical specifications.
Should ycu have any questions, please contact us.
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY D. E. Moo Manager of Operations DEM/em