ML20003D423
| ML20003D423 | |
| Person / Time | |
|---|---|
| Issue date: | 12/02/1980 |
| From: | Pasedag W Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20003D415 | List: |
| References | |
| FOIA-81-16 NUDOCS 8103270099 | |
| Download: ML20003D423 (3) | |
Text
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.,m RE-ASSESSMENT OF ACCIDENT SOURCE TEPJiS 1.
Claims made at the L1/18/80 Commission Meeting 1.1 Stratton, et al stated that the assumptions concerning iodine release in in Reg. Guides (1.3 and 1,4) are wrong (i.e., too large a release of molecular iodine is assumed) and that evidence points to the release fonn as
', Cesium Iodide, provided that a reducing environment and reasonable containment integrity is maintained.
1.2 Levinson said that the "part 100 source term" (i.e., the TID 14844 source term) is too conservative, and inconsistently interpreted by the staff by giving credit for ESFs, but not for various natural attenation processes.
1.3 Wall reiterated Levinson's "Part 100 source term" issues, but his main emphasis was related to WASH-1400. He stated that various natural attenuating processes have not been considered in WASH-1400.
1.4 Kouts used the TMI-2 experience to reevaluate the iodine releases assumed in WASH 1400. Using a 2% release would substantially reduce the
" iodine risk" from that given in the Reactor Safety Study.
1.5 Schikarski noted that new computer codes for aerosol behavior predict substantial agglomeration and settling of aerosols in a time frame of hours, provided that reasonable containment integrity is maintained.
2.
Needs for Resolution of Issues 2.1 Research Several aspects of these claims need to be addressed by continuing research programs, particularly in the area of the physiochemical forms of fission product release's under various accident conditions.
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2.2 Rulemaking Those aspects of these claims which address siting policy, the perceived inconsistencies in the staff's allowances for ESF's to reduce site distance factors, and those aspects related to emergency planning neasures will be addressed by rulemaking currently in progress.
2.3 Licensing Requirements Although several of the claims have zeroed in on the shortcomings of RASH-1400 most of the accident scenarios discussed or' implied are limited to those event sequences for which containment %
integrity is maintained. Under those conditions the primary impact of a re-assessment of accident source terms would be in the area of the design bases for engineered safety features (ESFs), and regulatory requirements related to the TMI Action Plan.
The regulatory assumptions concerning iodine have attracted particular attention from the various speakers.
However, reduction or elimination of the elemental iodine source tem would not necessarily result in substantial modifications in licensing requirements, since 16 dine is often used as a surrogate for other fission products, and many l
conservatisms in the iodine assumptions are incorporated for the I
l purpose of balancing non-conservative omissions elsewhere.
It is recognized that there is a need to examine these requirerents to ascertain whether significant distortions of ESF design requirements have arisen -
from this staff practice, to determine the feasibility of alternate methods for specifying fission product retention and consequence mitigation features, and to assess the potential for relaxation of regulatory requirements for mitigating systems..The attached outline lists the steps necessary for such a review of the licensing requirements.
. l I.
Define Alternative Source Tems (by dominant species) for the following:
1.
Noble gas release only (as base case)
L 2.
N.G., + iodine as Cs! in oxidizing environment 3.
N.G. + iodine as Cs1 in reducing environment 4.
N.G. + particulate aerosol II. Determine the effects of the alternative source terms on':
1.
Containment Leakage Requirements 2.
Control of leak paths through Auxiliary Bldgs. (via liquid systems) l 3.
Secondary Containment Systems 4.
Charcoal and liEPA filter systems 5.
Containment Spray and Spray Additive Systems 6.
MSIV Leakage Control Systems II. Determine effects of alternative source term criteria on regulatory requirements of:
~
1.
Reg. Guides and Standard Review Plan 2.
TMI Action Plan Requirements 3.
NRR Input to Siting, Degraded Core, Emeroency Preparedness and Min.imum Engineered Safety Feature Rulemakings QV. Cenclusions l
Include assessment of research program to identify specific information l
required for justification of revised source term.
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