ML20197J021

Provides Background Info Needed in Answering Questions Raised by Licensee Re Instrument Setpoint Methodology

ML20197J021
Person / Time
Site:	Columbia
Issue date:	08/30/1984
From:	Houston R Office of Nuclear Reactor Regulation
To:	Novak T Office of Nuclear Reactor Regulation
References
CON-WNP-0769, CON-WNP-769 TAC-55579, NUDOCS 8409120349
Download: ML20197J021 (5)

Text

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..7 MEMORANDUM FOR: Thomas M. Novak, Assistant Director for Licensing Division of Licensing FROM: R. Wayne Houston, Assistant Director for Reactor Safety Division of Systems Integration

SUBJECT:

INSTRUMENT SETP0 INT METHODOLOGY FOR WNP-2

References:

1) Letter from A. Schwencer (NRC) to D.W. Mazur (WPPSS) dated September 7, 1983, " Request for Additional Information"

2) Letter from G.C. Sorensen (WPPSS) to A. Schwencer dated September 23, 1983, "WNP-2, Setpoint Method-ology"

3) Letter from G.C. Sorensen to A. Schwencer dated August 2, 1984, "WNP-2, Request for Confirmation of CRGR Review"

4) Letter from T.M. Novak to J.F. Carolan (Chairman, ISMG) dated May 15, 1984, "NRC Staff Report on Set-point Methodology"

5) Letter from J.F. Carolan to T.M. Novak, dated June 29,1984, " Action Plan to Answer the Staff Con-cerns on Setpoint Methodology"

6) Letter from L.T. Gucwa (Georgia Power) to J. Stolz (NRC), dated June 7, 1984, " Response to NRC Staff Questions on Proposed ATTS Technical Specification Changes" Plant Name: Washington Public Power Supply System Nuclear Project No. 2 Docket No.: 50-397 l TAC No.: 55579 l Licensing Stage: OL Project Manager: Raj Auluck l

Review Branch: ICSB Review Status: Complete for TAC No. 55579 The purpose of this memorandum is to provide the background information needed in answering the questions raised by the licensee for WNP-2 regarding CRGR approval and Office of Management and Budget clearance for certain requests for information.

During the OL review of the WNP-2 Technical Specifications, the staff l

1dentified a concern regarding the values selected for protection CONTACT:

M. Virgilio, ICSB l X29454 8409120349840830Xk 4W~ ADOCK 05000397 5 9 :)

T.M. Novak system instrument setpoints. By letter dated September 7, 1983 (Reference 1), this staff concern was transmitted to the Washington Public Power Supply System (the applicant) in the form of a request for additional information, and a proposed license condition. The staff requested that the applicant provide revised Technical Specification instrument setpoint allowable values and proposed a license condition for providing additional information regarding the setpoint methodology, plant specific error allowances that were input to the setpoint methodology, and confirmation that the setpoints selected for WNP-2 ensure that the reactor core and reactor coolant system are prevented from exceeding the licensing safety limits.

By letter dated September 23, 1983 (Reference 2), the applicant responded to the request for information and proposed license condition. In this response, the applicant expressed the opinion that the staff concern was a generic issue, common to all plants with a General Electric nuclear steam supply system (NSSS). The applicant proposed that, in lieu of the plant specific schedule proposed by the staff, they be permitted to join other BWR applicants who had banded together in an effort to conserve resources in answering requests for information. The applicant proposed that the schedule for answering the request for information be based on the generic schedule proposed by this BWR owners group.

On December 20, 1983, WNP-2 was granted an operating license by the NRC.

By letter dated August 2,1984 (Reference 3), the licensee for WNP-2 requested confirmation that CRGR had formally reviewed the NRC staff's request for additional information on the setpoint methodology issue, and l confirmation that the request for information has received an Office of Management and Budget approval.

l The Commission's regulations relevant to the issue of protection system setpoints are General Design Criterion 20,10 CFR Part 50.36 and Part 50.46. Criterion 20, Protection System Functions, states that "the protection system shall be designed (1) to initiate automatically the j operation of appropriate systems including the reactivity control l

systems, to assure that specified acceptable fuel design limits are not l exceeded as a result of anticipated operational occurrences and (2) to l

sense accident conditions and to initiate the operation of systems and components important to safety." Part 50.36 states " limiting safety system settings for nuclear reactors are settings for automatic

, protective devices related to those variables having significant safety functions. Where a limiting safety system setting is specified for a variable on which a safety limit has been placed, the setting shall be so chosen that automatic protective action will correct the abnormal situation before a safety limit is exceeded." Part 50.46 specifies the performance criteria for the emergency core cooling systems. These criteria include a maximum peak cladding temperature, a maximum cladding l

T.M. Novak oxidation, a maximum total amount of hydrogen generated, and requirements that core geometry remain amenable to cooling for long term decay heat removal. Guidance on acceptable methods for complying with these regulations is contained in Regulatory Guide 1.105, " Instrumentation Setpoints" Revision 1, dated November 1976.

The staff has on an audit basis requested applicants to demonstrate compliance with the above cited regulatory requirements. Documentation dating back to the mid-1970's (prior to CRGR) shows that the NRC staff requested the applicants for 0.C.' Cook - Unit 2, Salem - Unit 2, North Anna - Unit 1, Sequoyah - Unit 1, McGuire - Unit 1, and V.C. Summer reply to a series of detailed questions concerning the methodology for determining instrument setpoints. Each follow-up safety evaluation written by the staff received a thorough NRC management review prior to issuance. The safety evaluations document the details of the setpoint methodologies proposed by the individual utilities to confirm compliance with the applicable regulations and the bases for staff approval. As a result of the interactions between the licensees and the staff on this issue, more conservative than originally proposed setpoints were established for several trip functions.

In August 1982, the staff requested the applicant for GESSAR, General Electric, to reply to a series of questions concerning the methodology for determining instrument setpoints. In response, GE stated that the setpoints were outside of the GESSAR scope and that the instrument set ~

point methodology issue would have to be addressed by individual utility applicants proposing the GESSAR design for licensing. Concurrently, on an audit basis, the staff individually requested several~ applicants with GE supplied NSSS to provide a summary discussion of the methodology used to establish the protection system actuation instrumentation setpoints.

These requests for information were either made during the Q1 phase of the staff review or during the technical specification review. Subse-l quently, meetings were held with several of the applicants individually l to discuss their setpoint methodology. On July 14, 1983 the staff met l with a group of applicants formed to address this and <%er licensing i issues (GE Owners Licensing Review Group [LRG] Instru iltation Setpoint i

Methodology Group [ISMG]) at their request. At this meeting, the ISMG presented an outline of a setpoint methodology specifically developed

, for the ISMG by GE in response to the staff's requests for information.

l In response to questions from the NRC staff, the ISMG agreed to provide more detailed information. On January 31, 1984, the staff met again with the ISMG to address the setpoint methodology. At this meeting, the ISMG presented five examples of instrument channel uncertainty evaluations l to demonstrate the margin to safety provided by the protection system instrumentation setpoints.

By letter dated May 15, 1984 (Reference 4), the staff provided its assessment of the ISMG methodology presented up to that point in time.

The staff evaluation identified several deficiencies in the methodology

.~. .

T.M. Novak presented and requested that the ISMG provide additional information in response to ten specific concerns. Section 4.0 of the evaluation summa-rizes the staff's understanding that past and present practice relies on engineering judgment with some conservatisms to account for uncertain-ties in establishing the NSSS setpoints. The systematic setpoint method-ology presented by the ISMG was developed solely for the ISMG plants to justify the use of engineering judgment.

In response to the staff's evaluation, by letter dated June 29, 1984 (Reference 5), the ISMG provided an action plan for resolving the outstanding issues regarding instrument setpoints for the ISMG member plants. The information to be provided in accordance with the action plan schedule will include plant unique setpoint calculations, assump-tions and input data. It should be noted that the list of participating utilities provided as an enclosure to the action plan did not include the licensee for WNP-2.

In summary, although the setpoint methodology issue is generic to all plants, at present there is no evidence to support a conclusion that it is a generic resolution. This is based on the results of our review of the setpoint methodologies submitted by other licensees with GE NSSS plants to support technical specification changes. For examph, by letter dated June 7, 1984 (Reference 6), the licensee for Edwin I. Hatch Nuclear Power Plant - Unit 2 proposed a setpoint methodology to support certain g technical specification setpoint changes. This methodology was substan-tially different from the ISMG proposed methodology and was approved by the staff for use in establishing the new setpoint values. Further, the staff's request for information does not impose or imply any new require-ments subject to CRGR review. The staff simply requested that the appli-cant furnish sufficient information to support a conclusion that the pro-tection system setpoints satisfy GDC 20, 10 CFR Part 50.36 and Part 50.46.

With regard to the staff's compliance with the Paper Work Reduction Act of 1980, each participating member of the ISMG was individually requested to supply certain information as a part of our OL review process. We are currently addressing seven members of the ISMG as one, at their request.

Although we believe that this is permitted by the Act we recommend that DL investigate this further Since the licensee is not a % ember of the ISMG (contrary to their September response to 23,1983 [ Referent)34 the August 2, 19 (Reference 3) letter, you request an2] co action plan for answering tTe staff's setpoint metnodology questions be provided, with a level of detail consistent with that provided by the t

5

T.M. Novak .

d ISMG in their June 29, 1984 (Reference 5), letter. This action plan should be submitted to the NRC for review within four weeks following receipt of the request.

/5/

R. Wayne Houston, Assistant Director For Reactor Safety Division of Systems Integration

! cc: R. Bernero

J. Stefano R. Auluck A. Schwencer B.J. Youngblood J. Conran DISTRIBUTION

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