ML20127P111

SER Accepting Licensee Commitment to Implement GIP-2, Including Clarifications,Interpretations & Exceptions Identified in Sser 2 as Method for Resolving USI A-46 at Plant

ML20127P111
Person / Time
Site:	Millstone
Issue date:	11/20/1992
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20127P109	List: ML20127P105 ML20127P111
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR GL-87-02, GL-87-2, NUDOCS 9212020070
Download: ML20127P111 (5)

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ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO 120-DAY RESPONSE TO SUPPLEMENT NO. 1 TO GENERIC LETTER 87-02 NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION. UNIT 2 DOCKET NO. 50-336 BACKGROUND By letter dated September 21, 1992, the Northeast Nuclear Energy Company, the licensee, submitted the response to Supplement No. I to Generic Letter 87-02 (GL FG -J2), " Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors, Unresolved Safety Issue (USI) A-46," dated May 22, 1992, for the Millstone Nuclear Power Station, Unit 2. In Supplement No. I to GL 87-02, the staff requested that affected licensees submit the following information within 120 days of the issue date of the supplement:

1. A statement whether you commit to use botn the Seismic Qualification Utility Group (SQUG) commitments and the implementation guidance provided in the Generic Implementation Procedure, Revision 2 (CIP-2) as supple 0ented by the staff's Supplemental Safety Evaluation Report No. 2 gSSER-2) for the resolution of USI A-46. In this case, any deviation from GlP-2, as supplemented by the SSER No. 2, must be identified, justified, and documented. If you do not make such a commitment, you must provide your alternative for responding to GL 87-02,

2. A plant-specific sc dule for the implementation of the GIP and submission of a regrt to the staff that summarizes the results of the USI A-46 review, if you are committing to implement GIP-2. This schedule shall be such that each affected plant will complete its implementation and submit the summary report within 3 years after the issuance of the SSER No. 2, unless otherwise justified.

3. The detailed information as to what procedures and criteria were used to generate the in-structure response spectra to be used for USI A-46 as requested in the SSER No. 2. The licensee's in-structure response spectra are considered acceptable for USI A-46 unless the staff indicates otherwise during a 60-day review period.

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r In addition, the stcff requested in SSER No. 2 that the licensee inform the staff in the 120-day response if it intends to change its licensing basis _to reflect a commitment to the USI A-46 (GIP-2) methodology for verifying the seismic adequacy of mechanical and electrical equipment, prior to receipt of the sta~f's plant-specific safety evaluation resolving USI A-46. This report provides the staff's evaluation of the licensee's response.

EVALVAT!0N With regard to Item I, the licensee stated that, "CYAPC0 and NGC0 intend to comply with the SQUG commitments set forth in Revision 2 of the GIP, including the clarifications, interpretations, and exceptions identified in SSER-2 in order to satisfy GL 87-02." The staff recognizes that the licensee has chosen to implement GIP-2, including both the SQUG vammitments and the implementation guidance, for responding to GL 87-02. The staff finds that this is an acceptable method to resolve USI A-46 Millstone Nuclear Powe" Station, Unit 2. .

The licensee indicated that it plans to use existing seismic qualification test reports to demonstrate seismic adequacy for any equipment on its safe shutdown equipment list (SSEL) which were previously qualified to IEEE 344-1975. The staff finds that tnis approach is acceptable for verifying equipment operability, but the licensee should also verify the seismic adequacy of the anchorage of this equipment in accordance with the criteria and procedures approved by the staff in SSER No. 2.

The licensee stated that it intends to use the Seismic Margin Methods defined in the Electric Power Research Institute's (EPRI) Report NP-6041-SL, dated August 1991, as one option for the resolution of equipment outliers. The methods defined in this report were intended to be used in conjunction with the seismic margin earthquake (SME), and not with the safe shutdown earthquake (SSE) used in USI A-46 reviews. The criteria and methods defined in the EPRI rep -t are less conservative than those defined in GIP-2. Therefcre, the methods defined in this report are, in general, not acceptable to the staff for resolving USI A-46 issues. Although the-staff acknowledges that outlier resolution is beyond the scope of GIP-2, the staff generally endorses, with the clarifications provided in SSER No. 2, the types of outlier resolution described in Section 5 of GIP-2 (_1.e., dynamic testing, engineering analysis, physical repair, and replacement). As stated in Section II.5 of SSER No. 2, "It is the responsibility of the utility to resolve outliers, using existing procedures (e.g., plant-spect:;c procedural controls and QA requirements) as it would resolve any other seismic concerns."- The staff will corsider the application of rome of the criteria provid d in EPRI Report NP-6041-SL, for the _ resolution of equipment outliers, on a case-by-case basis.

With regard 0 Item 2. the licensee stated that it will submit the Safe Shutdown Eque ant List Report, the Relay Evaluation Report, and the Seismic Evaluation Re,. ct to the NRC providino the results of the USI A-46 program at the Millstone Nuclear Power Station, Unit 2, within 180 days following the

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4 completion of Cycle #12 refueling-outage (Winter 1994). The proposed schedule for Millstone Unit 2 is within the 3-year response period requestod by the

-staff and is therefore acceptable.

With regard to Item 3, the staff has reviewed the licensee response with 'a particular objective of assessing the acceptability of the response to items 11.4.2.3 and 11.4.2.4 (as applicable) of the Supplemental Safety Evaluation No. 2 (SSEP.-2).

In compliance with the requirements of SSER-2, the licensee submitted the requested information on the subject matter. The staff has reviewed and evaluated the .nformation which can be summarized as follows:

1. The ground response spectra used envelopes the Housner spectra at all frequencies and the Modified Newmark spectra at frequencies higher than 7 cps. The input accelerations are: 0.099 horizontal and 0.06g vertical for OBE, and 0.179 horizontal and 0.llg vertical for SSE.

2. Structural damping values used are either less than or equal to those in R.G. 1.61.

3. The dynamic analysis codels used ere basically stick models with lumped masses.

4. All of the structures are supported basically on bedrock. However some of the structures are supported on shallow compacted structural backfill above the bedrock.

5. Fixed base assumption is used for the structures supported on bedrock, and.

soll springs and dashpots are used in the dynamic analysis for structures supported on compacted backfill.

6. The effects of the vertical and horizontal components of the earthquakes are assumed to occur simultaneously-and combined directly.

7. Analyses for vertical direction as well as for horizontal direction using the ground design spectrum curves are performed.

8. The in-structure response spectra are broadened in accordance with RG 1.122.

9, a) To obtain in-structure response spectra for SSE, the values developed i for-0BE are multiplied by the factor of 2 b) The time history used to generate the in-structure responses is a composite of the N69W components of the 1952 Taft earthquake and N-S components of the 1940 EL Centro earthquake.

c) The response spectrum method of analysis is used for the seismic analysis of structures.

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, it is the :taff position that if the licensee follows the criteria and procedure _as summarized above in the generation of the in-structure response i spectra, " Conservative Design" in-structure response spectra should result.

Based on our review of the licensee response and the staft positions delineated in SSER-2, we conclude that the licensee response is adequate and acceptable. This_ conclusion is based on the assumption that the statements made in the submittal 1 cluding the criteria and procedure used in the generation of the in-structure response spectra, correctly reflect what is contained in the FSAR on seismic design and bther licensing basis. The str.ff may audit the process by which the in-structure response spectra were generated.

The licensee indicated that, as part of the resolution of GL 87-02, it intends to change its licensing basis, via 10'CFR 50.59, to include the GIP methodologies as an option for demonstrating the seismic adequacy of new and replacement plant equipment. The staff recognizes that the licensee may-revise its licensing basis in-accordance with 10 CFR 50.59 to reflect the acceptability of the USI A-46 (GIP, methodviogy for verifying the seismic adequacy of electrical and mechanical equipment covered by the GIP. However, since the licensee intends to augment its licensing _ basis to include the GIP .

methodology as an option for verifying seismic adequacy, rather than revise its licensing basis such that the GIP-2 would be the sole methodology, the staff caution, that it is not acceptable to combine any part of GIP-2 with the current licensing basis methodologies such that it results in a less conservative approach than if CIP-2 cr the current licensing basis methe ciogies were applied separately.

-CONLLUSIONS The staff finds that the licenste's commitment to implement GIP-2, including the clarifications, interpretations and exceptions identif'ed in SSER No. ~2, is an acceptable method for resolving USI A 46 at the Millstone Nuclear Power Station, Unit 2.

The staff finds that it is acceptable for the licensee to use previously performed anchorage evaluations for USI A-46 provided that the evaluations meet the criteria and procedures approved in SSER No. 2 (Section 11.4.4). The i -staff also finds that it is acceptable to use existing seismic. qualification test reports to demonstrate operability for SSEL equipment which was qualified to IEEE 344-1975.

N methods defined-in EPRI Report NP-6041-SL are, in general, not acceptable t; the staff for resolving equipment outliers. However, the staff will

consider the application of some of the criteria provided in EPRI Report NP-6041-SL, for the resolution of equipment outliers, on a case-by-case basis.

The proposed implementation schedule for Millstone Unit 2 is within the 3-year response period requested by the staff and is therefore acceptable.

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J The staff concludes that the licensee response with respect to in-structure response spectra is adequate and acceptabi'. This conclusion is based on the assumption that the statements made in the s'ibmittal, including the criteria and procedure used in the g-aneration of the in-structure response spectra, ccrrectly ret' lect what is contained in the FSoR on seismic design and other-licensing basis. The staff may audit the process by which the in-structure response spectra were generated.

The staff recognizes that the licensee may revise its licensing basis in accordance with 10 CFR 50.59 to reflect the acceptibility of the USI A-46 I, GIP) methodology for verifying the seismic adequacy of electrical and mechanical equipment covered by the GIP. However, since the licensee intends ,

to augment its licensing basis to include the GIP methodology as an option for !

verifying seismic adequacy, rather than revise its licensing basis such that the GIP-2 would be the sole methodology, the staff cautions that it is not acceptable to combine any part of GIP-2 with the current licensing basis methodologies such that it results in a less onservative approach than if GIP-2 or the current licensing basis methodoiogies were applied separately.

Principal Contributors: C. P. Tan M. McBrearty P. Chen Date: November 20, 1992 P

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