ML20044A856
| ML20044A856 | |
| Person / Time | |
|---|---|
| Issue date: | 06/26/1990 |
| From: | Chilk S NRC OFFICE OF THE SECRETARY (SECY) |
| To: | Taylor J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| References | |
| REF-10CFR9.7 NUDOCS 9007160185 | |
| Download: ML20044A856 (5) | |
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UNITED STATES L
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NUCLE AR REGULATORY COMMISSION 3
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June 26,1990 l
RELEASED TO THE PDR a
orricE OF THE p
j/gp SECRETARY seeoeoooooosees.eeeeeese MEMORANDUM FOR:
James M. Taylor, Executive Director for Operatio s
FROM:
amuel J.
Chil,,
'c etary
SUBJECT:
SECY-90 EVOLUTIONARY LIGHT WATER REACTOR (LWR) CERTIFICATION ISSUES AND THEIR RELATIONSHIPS TO CURRENT REGULATORY REQUIREMENTS This is to advise you that the Commission as detailed below has approved in part and disapproved in part the staff's recommendations in SECY-90-16.
I.
General Issues.
OOiOb A.
ALWR Public Safety Goal.
The Commission (with Chairman Carr and Commissioners Roberts,CurtgsandRemickagreeing) has disapproved the use of 10 per year of reactor operation as a core damage frequency for advanced designs.
As noted in the SRM on SECY-89-102 (dated June 15 1990), the t4 commission supports the use of 10 per year of reactor operation as a core damage frequency goal.
Although the commission strongly supports the use of the information and experience gained from the current generation of reactors as a basis for improving the safety performance of new designs, the NRC should not adopt industry objectives as a basis for establishing new requirements.
However, if the staff in applying the criteria of 10 CFR Part 52 (and in view of the
-uncertainties associated with PRA's) concludes that additional requirements are needed, based on our experiences with prior designs, in order to provide NOTE:
THIS SRM AND THE SUBJECT SECY PAPER WILL BE MADE PUBLICLY AVAILABLE 10 WORKING DAYS AFTER ISSUANCE OF THE SRM.
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.2 assurance that future designs will meet the Safety Goal Policy Statement, then the staff should provide those l
additional requirements to the Commission for i
consideration as they are identified.
-5 Commissiors a s gers approved the staff's use of 10 as an expecteo design target for ELWR designers and endorsed a requirement that. applicants be able to demonstrate that they have taken reasonable steps to reach these targets.
However, he does not endorse' those goals as an absolute requirement for approval of e
any specific design.
Consistent eith the Commission's decision on SECY-89-102, the Commission approved the overall mean frequency of a large release of radioactive matsrial to the environment from a reactor accident as less than ene in one million per year of reactor operation.
The Commission has not agreed on a definition of a large release _and has requested a paper from the staff (See SRM from SECY-89-102).
B.
Source Term.
The Commission (with all Commissioners agreeing) has approved the staff's approach to the source term with the addition of the following element:
o on an expedited basis, incorporate appropriate changes to regulations, regulatory practices, and the review process resulting from source term research.
L II.
Preventative Feature Issues.
1 A..
ATWS.
The Commission (with all Commissioners agreeing) has approved the staff position.
However, if the applicant-I can demonstrate that the consequences of an ATWS are acceptable the staff should accept the demonstration as an alternative to the diverse scram system.
Commissioner Curtiss further believes that the staff should retain the flexibility to accept designs with non-diverse scram logic in those instances where it is demonstrated to the staff's satisfaction that the reliability of the scram function is such that the risk from ATWS is insignificant.
B.
Mid-Looo coeration.
The Commission (with all Commissioners agreeing) has approved the staff's proposed position, with the ACRS recommendation of April 26, 1990, that four additional specific requirements be considered for mid-loop operation.
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,1 C.
Station Blackout.
I The Commission (with all Commissioners agreeing) has approved the staff's position that the evolutionary ALWR's have an alternate ac power source of diverse design capable of powering at least one complete set of normal shutdown loads.
The staff should provide a clear definition of " diversity" so as to provide guidance on whether it means different types, different manufacturers, different models, etc.
Commissioner i
Curtiss noted that, in his view, the clarification i
should focus on limiting common mode failure potential but need not go so far as to require completely different generator driver technologies (e.g. should not necessarily require both diesel and gas turbine drl+ren generators).
D.
Fire Protection.
The Commission (with all Commissioners agreeing) has approved the staff's position on fire protection as presented in SECY-90-16 and supplemented by the staff's April 27, 1990, response to the ACRS comments.
E.
Intersystem LOCA.
The Commission (with all Commissioners agreeing) has approved the staff's position on intersystem LOCA provided that, as recommended by the ACRS, all elements of the low pressure system are considered (e.g.
instrument lines, pump seals, heat exchanger tubes, and valve bonnets.)
III. Biticative Feature Issues.
A.
Hydrocen Generation and Control.
i The Commission (with all Commissioners agreeing) has approved the staff's position that the requirements of 10 CFR 50.34 (f) (2) (ix) should remain unchanged for evolutionary plants.
The staff should seek additional technical information, as suggested-by the ACRS, and if reconsideration is warranted the Commission should be advised.
D.
Core-Concrete Interaction--Ability to Cool Core Debris.
The Commission (with all Commissioners agreeing) has approved the staff's position.
C.
Hiah Pressure core Melt Eiection.
The Commission (with all-Commissioners agreeing) has approved the staff's position that the ELWR designs include a depressurization system and cavity design to contain core debris.
The cavity design, as a
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4 mitigating feature, should not unduly interfere with operations including refueling, maintenance, or surveillance activities.
D.
Containment Performance.
The Commission (with all Commissioners agreeing) has approved, consistent with SECY-89-102, the use of a 0.1 CCFP as a basis for establishing regulatory guidance for the ELWRs.
This objective should not be imposed as a requirement in and of itself.
The use of the CCFP should not discourage accident prevention and the staff should review suitable alternative, deterministically-established, containment performance objectives providing comparable mitigation capability if submitted by applicants.
Any such alternatives should be submitted to the Commission following staff review.
E.-
ADWR Containment Vent Desian.
The Commission (with all Commissioners agreeing) has approved the staff's recommended use of the containment cverpressure protection system on the ABWR, subject to the results of the comprehensive regulatory review which should fully weigh the potential "downside" risks with the mitigation benefits of the system.
Staff should ensure that full capability to maintain control over the venting process is provided.
F.
Equiement survivability.
The Commission (with all Commissioners agreeing) has approved'the staff's position.
IV.
Non-Severe Accident Issue.
A.
Oneratina Basis Earthauake (OBE)/ Safe Shutdown l
Ea rthoua ke (SSE).
The Commission (with all Commissioners agreeing) has approved the staff's position.
B.
Inservice Testina of Pumr,s and Valves.
The Commission (with all commissioners agreeing) has approved the staff's position as supplemented in their April 27, 1990, response to the ACRS comments.
The Commission notes that due consideration should be given to the practicality of designing testing capability, particularly for large pumps and valves.
Ths Commission also agreed that in those cases where the staff proposed requirements depart from current regulations, con 2ideration should be given to incorporating these requirements into the regulations.
(See SRM dated May 27, 1990, M90053A).
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Finally, the. staff is encouraged to strive to sustain the level of attention and resources that have been devoted recently to the review process for the EPRI requirements document.
The recent t'
comments of the EPRI representatives at the June 4, 1990 Commission briefing suggest that such a commitment, if sustained, can be most beneficial in assisting EPRI and the NRC staff in our respective' efforts to reach a common understanding on the key technical issues.
cc:
Chairman Carr Commissioner Roberts Commissioner Rogers Commissioner Curtiss Commissioner Remick OGC ACRS i
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