ML20128D451

Safety Evaluation Accepting Evaluation of 120-day Response to Suppl 1 to GL 87-02, Verification of Seismic Adequacy of Mechanical & Electrical Equipment in Operating Reactors, Unresolved Safety Issue A-46

ML20128D451
Person / Time
Site:	Fort Calhoun
Issue date:	11/30/1992
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20128D426	List: ML20128D423 ML20128D451
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR GL-87-02, GL-87-2, NUDOCS 9212070282
Download: ML20128D451 (5)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION E_ VALUATION OF 120-DAY RESPONSE 10 SUPPLEMENT NO.- 1 TO GENERIC LETTER 87-02 OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION. UNIT N0J DOCKETJ10. 50-285

1.0 INTRODUCTION

By letter dated September 21, 1992, Omaha Public Power District (the licensee) -

submitted its response to Supplement No I to Generic Letter (GL) 87-02,

" Verification of Seismic Adequacy of Mechanical and Electrical Equipment-in Operating Reactors, Unresolved Safety Issue (USI) A-46," dated May:22, 1992, for the Fort Calhoun Station, Unit 1. _In this supplement, the NRC requested that the licensee submit the following information within 120 days of the-issue date of the supplement:

1.- A statement whether you commit to use both the Seismic' Qualification Utility Group-(SQUG). commitments and the implementation guidance provided in the Generic Implementation Procedure Revision 2 (GIP-2)-as supplemented by the NRC's Supplemental-Safety Evaluation Report No. 2 (SSER No. 2) for the resolution of USI A-46. In this case, any devia-tion from GIP-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 schedule for the implementation of the iP and- ..

submission of a report to the NRC 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 of the issuance of the SSER No. 2, unless otherwise justified.-

3. The detailed information as to what procedures and criteria were usedLto~-

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 NRC indicates-otherwise during a 60-day _ review ~ period.

, In addition, the NRC: requested in SSER No. 2 that the licensee inform the NRC,.

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:af-the NRC's plant-specific safety evaluation resolving USI A-46.

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. 9212070282 921130 PDR ADOCK 05000285

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j 2.0 EVALUATION With regard to Item 1, the licensee stated that it "... commits to the SQUG commitments set forth in the GIP in their entirety, including the clarifications, interpretations and exceptions identified in SSER-2 as clarified by the August 21, 1992, SQUG letter res)onding to SSER 2." T'e licensee also stated that, " Generally, OPPD will 3e guided by the remai ng (non-commitment) sectio's of the GIP, i.e., GIP implementation guidance, which comprises suggested methods for implementing the applicable GIP commitments."

The licensee's response is unclear as to whether or not the licensee intends to implement both the SQUG commitments and the implementation guidance. In accepting GIP-2 as a method for resolving USI A-46, it was the NRC's under-standing that the SQUG members who chose to implement GIP-2 would essentially use the entire procedure, including the SQUG commitments, which_contain the general programmatic objectives and goals, and the implementation guidance, which cetains the specific criteria and procedures to be used for the resolu-tion of USI A-46. This understanding was the oasis for the NRC's position,-

which was stated in SSER No. 2, that if the licensee commits to use GIP-2 for the implementation of USI A-46, it must commit to both the SQUG commit-ments and the use of the entire implementation guidance provided in GIP-2, unless otherwise justified to the NRC. In order to allow some flexibility in implementing GIP-2, the NRC acknowledged in the supplement to GL 87-02 that SQUG members who commit to GIP-2 (both the SQUG commitments and the implementation guidance) may deviate from it provided that such deviations are identified, documented and justified. However, it was also indicated in SSER No. 2 that if a licensee uses methods that deviate from the criteria and pro-cedures described in the SQUG commitments and in the implementation guidance of GIP-2 without prior NRC approval, the NRC may find the use of such methods unacceptable with regard to satisfying the provisions of GL 87-02.

In light of the above, the NRC interprets the licensee's response to_ .

Supplement No I to GL 87-02 as a commitment to the entire GIP-2 including both the SQUG commitments and the implementation guidance, and therefore considers it acceptable. If the NRC's interpretation is incorrect, then, in accordance with Supplement No. I to.GL 87-02,.the licensee should provide for-

-NRC review, as soon as practicable prior to implementation, its alternative criteria and procedures for responding to GL 87-02.

In addition, Enclosure 2 provides the NRC's response, dated October 2, _1992, to the August 21, 1992,.SQUG 1etter. The NRC does not concur with all of the SQUG's clarifications and positions stated in that letter, and,-thus,-the licensee should not use the August 21, 1992, letter as guidance in responding 4 to Supplement No. I to GL 87-02. T% licensee should refer to Enclosure 2 for the NRC's position on the SQUG letter.

With regard to item 2, the licensee stated that it will submit a summary report to the NRC summarizing the results of the USI A-46 program at Fort

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. Calhoun Station, Unit 1 by September 29, 1995. This submittal date is within.

the 3-year response pericd requested by the NRC rnd 1s therefore acceptable.

With regard to item 3, the licensee stated that the requested information on the subject matter can be found mainly in Appendix F to the updated safety analysis report (USAR). The information in Appendix F was reviewed and evaluated and can be summarized as follows:

1. The ground response spectra used conform to the average spectra developed by Housner Tor frequencies higher than 0.33 cycles per second (cps). The spectra for frequencies lower than about 0.33 cps were prepared using data presented by Newmark. The design horizontal grc,und motions are 0.089 for OBE and 0.179 for SSE, and vertical motions are two-thirds of the horizontal.

2. The structural damping values are equal to or smaller than those of Regulatory Guide (RG) 1.61.

3. The seismic analysis models used consisted of stick models with lumped masses and soil springs.

4. Soil-structure interaction has been taken into consideration through the use of soll springs, the stiffness (vertical and rotary) of which was determined based on the axial rigidity of the piles without taking into account the effect of the soil surrounding the piles. However, the lateral stiffness coefficient of the foundation depends on the soil modulus and elastic properties of the piles.

5. Because piles are used, no variation of foundation medium has been considered.

6. The horizontal and the vertical components of the earthquakes are assumed to be acting simultaneously.

7. The seismic analysis for the motion in the vertical direction.was accomplished by using one lumped mass. The vertical motion was assumed to be uncoupled from the rest of the motions of the system.

'8. There is no mention on peak broadening.

9. a) The time history used in the generation of the floor response spectra consists of ground motions from the 1940 EL Centro and 1952 Taft earthquakes.

b) The information on the alternate seismic criteria is not readily available and is not reviewed.

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. 4-Based on the references aiven in the licensee response, the-NRC has gathered all the available refer Nes and reviewed the information contained therein.

Some of the above summarized information is obtained through the NRC's 1 interpretation of various licensee statements. The NRC finds the information-on the following items to be incomplete:

a) n item 6 above, how the effects of the horizontal and vertical components ;

are combined mathematically is not clear.

b) In item 8 above, it is not certain whether peak broadening is considered or not.

c) Regarding Item 9.a), which components (E-W or N-S) of the EL Centro or Taft earthquakes were used and how they were applied is not clear.

On the basis of the NRC's review of the incomplete information provided, the NRC concludes that the use of the criteria and procedure in Appendix F to the USAR would result in median-centered ;ather than the " Conservative Design" in-structure response spectra. Thus the licensee's in-structure response spectra are accepted as medium-centered spectra.

On the basis of the NRC's review of the incomplete information provided, the NRC concludes that the use of the criteria and procedure in Appendix F to the USAR would result in median-centered rather than the " Conservative Design" in-structure response spectra. Thus the licensee's in-structure response spectra are accepted as medium-centered spectra.

The licensee indicated that it may change its licensing basis methodology, via 10 CFR 50.59, for verifying the seismic adequacy of new, replacement, and existing electrical and mechanical equipment prior to receipt of a final plant-specific SER resolving USI A-46. The NRC 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) methodology for verifying the' seismic adequacy of electrical and mechanical equipment covered by the GIP. However, if the licensee does not commit to implement both the SQUG commitments and the implementation guidance and if the licensee has not committed to any acceptable alternative criteria and procedures, then' the NRC does not believe that it is feasible, at this time, for the licensee to change its licensing basis in the manner described.

3.0 CONCLUSION

The NRC interprets the licensee's response to Supplement No. I to GL 87-02 as a commitment to the entire GIP-2, including both the SQUG commitments and the implementation guidance, and therefore considers it acceptable. If the licensee does not commit to implement the entire GIP-2, then, in accordance with Supplement No. I to GL 87-02, the licensee should provide for NRC review, as soon as practicable prior to impl wentation, its alternative criteria and procedures for responding to GL 87-02. Additionally, the licensee should not

. merely follow the August 21, 1992, SQUG 1etter for_ implementing GIP-2, but should refer to Enclosure 2 for the NRC's response to the SQUG letter.

The implementation schedule proposed by the licensee is within the 3-year response period requested by the NRC in Supplement No. I to CL 87-02 and is therefore acceptable.

The NRC 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) methodology for verifying the seismic adequacy of electrical and mechanical equipment covered by the GIP. However .if the licensee does not commit to implement both the SQUG connitments and the implementation guidance and if the licensee has not committed to any acceptable alternative criteria and procedures, then the NRC does not believe that it is feasible, at this time, for the licensee to change its licensing basis in the manner described.

Principal Contributors: C. Tan S. Bloom P.Y. Chen M. McBrearty Date: November 30, 1992

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EkCLOSURE 2-

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wAsHWO TON, D. C. 20S$6 r.....,I OCT 01 g Mr. Neil Smith, Chairman Seismic Qualification Utility Group c/o EPRI 1019 19th Street, N.W.

Washington, DC 20036 ,

SUBJECT:

NRC RESPONSE TO SEISMIC QUALIFICATION UTILITY GROUP (SQUG)

Re:

Letter, H. Smith, EPRI, To J. Partlow, NRR, dated August 21,-1992, concerning USI A-46 Issues.

Dear Mr. Smith:

This is to acknowledge the receipt of the SQUG response to Suppl'ement No.1- to.

Generic Letter (GL) 87-02, and Supplemental Safety Evaluation (SSER) No. 2, on '

the SQUG Generic Implementation Procedure for Seismic Verification of Nuclear Plant Equipment, Revision 2, as corrected February 14, 1992 (GIP-2) The NRC staff believes that successful implementation of the entire GIP-2, supple-mented by the staff's SSER No. 2, by each SQUG licensee will tresult in cost-effective plant safety enhancement for their USI . A-46 plants.

The staff also believes that the positions delineated in Supplement No.11 to-GL 87-02 and SSER No. 2 are clear and correct, and should'not be_ misinterpret-ed. The staff's comments on SQUG's August 21, 1992,_ letter and attachment are provided in the enclosure to this letter. If you need-further clarification concerning our response, please contact Mr. James Norberg at-504-3288,-

Sincerely, r

hA James G. Partlow -

. Associate Director for Projects Office of Nuclear Reactor Regulation

Enclosure:

As stated .

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.j c ENCLOSURE

!. NRC's Comments on the 500G Letter of Auoust 21. 1992:

1. In regard to the issue of seismic qualification, the staff reiterates the position stated in the SSER No. 2, in that the GIP-2 methodology is not considered to be a seismic qualification method, rather, it is an acceptable evaluation method, for USI A-46 plants only, to verify the seismic adequacy of the safe-shutdown equipment and to ensure that the pertinent equipment

'seisW requirements of General Design Criterion 2 and the purpose of the NRC regulations relevant to equipment seismic- adequacy including 10 CFR Part 100 are satisfied. I

2. The second paragraph on page 2 of your letter addressed the issue of timing of staff response to additional information requested from a licensee. Although you are correct in your statement regarding the sixty-day period for response to initial submittal of in-structure response spectra (ISRS) information,.we do not agree that the same concept applies to a licensee's submittal of additional information received following a rejection or a '

quection from the staff. To eliminate any potential misunder-standing in this regard, the staff has determined that it will i resoond to any submittal of additional information received from a i licensee within 60 days. However, in this response, the staff will either state its approval (or rejection) of the information provided, or indicate the time duration needed for the review of such information, prior to transmitting a follow-up response of acceptance (or rejection) to the-licensee. This time duration-will vary depending on the complexity of the submittal.

3. Regarding the EBAC and ANCHOR computer. codes, the staff's evaluations and concerns stated in the SSER No. 2 are correct and valid. The ANCHOR code does not consider the effects of base plate flexibility on the anchorage capacity.

4. With respect to transfer of knowledge regarding major problems identified, and lessons learned, in the USI A-46 plant walkdowns and third-party iaviews, we request that you include the NRC in the distribution of written communications to all member utilities in this regard, and inform the NRC staff of any planned workshops on A-46 implementation for possible staff participation.

II. NRC's Comments on the Procedure for Reviewino the GIP

1. The staff supports SQUG's establishment of a Peer Review Panel composed of seismic experts since it should serve to enhance the review process of substantive changes to the technical requirements-in the GIP, prior to its submittal to NRC for approval. However, since the NRC no longer intends to help finance a Peer Review Panel, the staff does not believe it a

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is. appropriate to participate in the selection of the Peerf Review -

• i members, who will.be financed by SQUG/EPRI. We would:likelto. 1

. emphasize ~that staff's review of;aLproposed GIP-change will receive thorough. independent NRC evaluation and will be' assessed I on.its merits. .I

2. With respect to the NRC review and approval of the changes to-the GIP (Item 5, page 3 of the procedure), the staff's position'on the issue of its response timing is identical /to that delineated in-

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the response to a licensee submittal of additional _ information a (refer to item 2 of NRC's Comments on the SQUG-letter in this. 1 enclosure). This comment also applies-to the section." LICENSING q CONSIDERATIONS" on page 5 of-the Attachment to the SQUG letter. l

3. With respect to item 4, " Additional Restrictions," the. text should ,

be expanded to reflect that new information which indicates that  :

existing GIP criteria-and guidelines may be-unconservative should. i be evaluated for potential 10-CFR Part-21 implications.

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