ML20211D543

Forwards RAI Re Licensee 951120 Submittal of plant-specific Summary Rept IAW Commitment Re GL 87-02, Verification of Seismic Adequacy of Mechanical & Electrical Equipment in Operating Reactors,Usi A-46

ML20211D543
Person / Time
Site:	Prairie Island
Issue date:	09/16/1997
From:	Wetzel B NRC (Affiliation Not Assigned)
To:	Richard Anderson NORTHERN STATES POWER CO.
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR GL-87-02, GL-87-2, TAC-M69474, TAC-M69475, NUDOCS 9709290169
Download: ML20211D543 (7)

Text

t Mr. Roger 0. Anderson. Director september 16, 1997 Licensing and Management Issues Northern States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON THE PRAIRIE ISLAND NUCLEAR GENERATING PLANT. UNITS 1 AND 2. RESOLUTION OF UNRESOLVED SAFETY ISSUE A-46 (TAC NOS. M69474 AND M69475) i

Dear Mr. Anderson:

By letter dated November 20. 1995. Northern States Power Company (NSP) submitted its plant-specific summary report in accordance with its commitment relating to Generic Letter 87-02 (" Verification of Seismic Adequacy of Mechanical and Electrical Ecuipment in Operating Reactors. USI A-46") on the resolution of the unresolvec safety issue (USI) A-46 program at the Prairie Island Nuclear Plant. Units 1 and 2. The NRC staff has reviewed NSP's summary report and determined that additional information is needed to complete our review of NSP's A-46 response. Our request for additional information (RAI) is enclosed.

The Summary Report does not identify any cable tray related outliers, which implies that no deviation from GIP-2 guidelines was found. However. the staff found that the GIP-2 guidelines may be ambiguous on ductility consideration of cable tray support mmbers. Consequently, some cable tray support arrangements may have been prematurely screened out. The staff is currently j assessing the subject and may request additional information if necessary.

Please provide your response to the staff's RAI within 60 days of the date of this letter in order to support the staff's review schedule for USI A-46. If you have any questions regarding the content of the RAI. please contact me at (301) 415-1355.

Sincerely.

ORIGINAL SIGNED BY Beth A. Wetzel. Senior Project Manageri -

Project Directorate III-I /

9709290169 970916 ADOcK 0500 2 Division of Reactor Projects - III/IV I gDR Office of Nuclear Reactor Regulation Docket Nos. 50-282. 50-306 IN/

Enclosure:

As stated cc w/ encl: See next page Ripp

% 1 m?

e- , . . . .

'""P DISTRIBUTION:

Docket File PUBLIC PD# 3-1 Reading EAdensam (EGA1) OGC ACRS JMcCormick-Barger. RIII Shou KManoly RWessman GBagchi DOCUMENT NAME: G:\WPDOCS\ PRAIRIE \PI69474.RAI To receive a copy of this document, indicate in the box C-Copy w/o attachment / enclosure E-Copy with attachment / enclosure N - No copy 0FFICE PM:PD31 LA:PD31 E E 0:PD31//

NAME BWetzel :db@" CJamersonk JHand DATE ) / d /97 i /15 [/97 h /M /97 0FFICIAL RECORD COPY lllllll!llfl

....<.o ll]lllll

Mr. Roger O. Anderson, Director Prairie Island Nuclear Generating Northem States Power Company Plant ec:

J. E. Silberg, Esquire Site Licensing Shaw, Pittman, Potts and Trowbridge Prairie Island Nuclear Generating 2300 N Street, N. W. Plant Washington DC 20037 Northem States Power Company 1717 Wakonade Drive East Plant Manager Welch, Minnesota 55089 Prairie Island Nuclear Generating Plant Tribal Council Northem States Power Company Prairie Island Indian Community 1717 Wakonade Drive East ATIN: Environmental Department Welch, Minnesota 55089 5636 Sturgeon Lake Road s

Welch, Minnesota 55089

) Adonis A. Nebiett Assistant Attomey General Office of the Attomey General 455 Minnesota Stiset Suite 900 St. Paul, Minnesota 55101-2127 U.S. Nuclear Regulatory Commission Resident inspector's Office 4

1719 Wakonade Drive East Welch, Minnesota 55089-9642 I Regional Administrator, Region ill

) U.S. Nuclear Regulatory Commission 801 Warrenville Road Lisle, Illinois 60532-4351 Mr. Jeff Cole, Auditor / Treasurer Goodhue County Courthouse Box 408 Red Wing, Minnesota 55066-0408 Kris Sanda, Commissioner Department of Public Service 121 Seventh Place East Suite 200 St. Paul, Minnesota 55101-2145 .

November 1996

REQUEST FOR ADDITIONAL INFORMATION ON RESOLUTION OF USI A-46 ON EQUIPMENT SEISMIC ADEQUACY AT PRAIRIE ISLAND NUCLEAR GENERATING PLANT. UNITS 1 AND 2 Docket Nos: 50 282 and 50-306

References:

1. Letter (Generic Letter 87-02) from Northern States Power Company to NRC with attachments of a Summary Report and a Relay Evaluation Report, dated November 20, 1995.

2. Letter (Generic Letter 87-02) from Northern States Power Company to NRC with updated outlier resolution schedule, dated December 31, 1996.

1. In the letter of Reference 1. the licensee indicates its intent to apply the USI A-46 methodology to future verification of seismic adequacy of any new or replacement equipment or parts, which may also imply to include equipment identified as part of Regulatory Guide (RG) 1.97 or TMI Action Plan item II.F.2. However, the staff position in Item 2 of Section I.2.3 of the supplemental safety evaluation report (SSER)-2, which clarifies Section 2.3.3 of the generic implementation procedure (GIP)-2 regarding revision of plant licensing bases is that any previous licensing commitments, such as for RG 1.97 and TMI Action Plan item II.F.2, are noi, superseded by the resolution methods of the GIP.

Clarify your commitment with regard to the applicability of the A-46 methodology to new and replacement Category 1 equipment included in the SSEL [ safe-shutdown equi ament list] that are associated with RG 1.97 or TMI Action Plan item 11. 7.2.

2. Referrina to the in-structure resoonse soectra (ISRS) orovided in your 120-day-resoonse to the NRC's reauest in Sucolement No.1 to Generic Letter 87-02. the followina information is reauested:

a. Identify structure (s) that have ISRS with 5% critical dam)ing for elevations within 40-feet above the effective grade, whic1 are higher in amplitude than 1.5 times the SOUG [ Seismic Qualification Utilities Group] Bounding Spectrum.

b. With respect to the comparison of equipment seismic capacity and seismic demand, indicate which method in Table 4-1 of GIP-2 was used to evaluate the seismic adequacy for equipment installed on the corresponding floors in the structure (s) identified in Item (a) ebove. If you have elected to use method A in Table 4-1 of the GIP-2, provide a technical justification for not usir.g the ISRS provided in your 120-day response.

c. It appears that some A-46 licensees are making an incorrect comparison between their plant's safe shutdown earthquake (SSE)

ENCLOSURE

~

2 ground motion response spectrum and the SOUG Bounding Spectrum. The SSE ground motion response spectrum for most nuclear power plants is defined at the )lant foundation level. The SOUG Bounding Spectrum is defined at tie free field ground surface. For plants located at deep soil or rock sites, there may not be a significant difference between the ground motion amplitudes ct the foundation level and those at the ground surface. However, for sites where a structure is founded on shallow soil, the amplification of the ground motion from the foundation level to the ground surface may be significant.

Clarify appropriateness of a direction comparison of the SOUG Bounding Spectrum with the Prairie Island plant ground motion spectrum,

d. For the structure (s) identified in Item (a) above. rovide the ISRS designated according to the height above the effective grade. If the ISRS identified in the 120-day response to Supplement No. I to Generic Letter 87-02 was not used, provide the response spectra that were actually used to verify the seismic adequacy of equipment within the structures identified in Item (a) above. Also, provide a comparison of these spectra to 1.5 times the Bounding Spectrum.

3. In the letter of Reference 2. the licensee submitted its updated commitment regarding the outlier resolution schedule. The pro)osed time frame to complete all outlier resolution actions ranges from tie end of 1996 to the spring of 1999, depending on the determination whether a specific outlier will be resolved by analysis or by modification with or without plant outage. In addition, although 96 outlier equipment and 49 outlier relays were identified in the Summary Report and the Relay Evaluation Report of Reference 1. information regarding their resolution is not included in the reports. Elaborate on your plans for scheduling the resolution of identified outliers, and your evaluation in support of the conclusion that the licensing bases for the plant will not be affected by the outliers resolution schedule. A number of safety-related components in the safe shutdown path have been identified as outliers -- thus rendering their seismic adequacy questionable and their conformance to the licensing bases uncertain. Provide justification of your continued operation without immediately undertaking remedial action.

4. Describe the extent to which the seismic margin methodology, described in the report EPRI NP-6041 ("A Methodology for Assessment of Nuclear Power Plant Seis lic Margin"), was used in the Prairie Island A-46 program including outlier resolutions. Since this methodology is known to yield analytical results that are not as conservative as what might be obtained by following the GIP-2 guidelines, it is generally not acceptable for the A-46 program. Therefore, for each deviation from the GIP-2 guidelines. in situations where the margin methodology is utilized, identify the nature and the extent of the deviation, and provide the justification for its acceptance.

5. Section 3.4 of the Summary Report states that one horizontal ISRS was used for both (North-South and East-West) directions. Indicate whether i

the horizontal ISRS used for the USI A-46 program envelop both horizontal ISRS provided in the NSPC's 120-day response to Sup)lement No. I to Generic Letter 87-02. If not, provide the technical )ases that supports the validity of such an assumption and an explanation of how the results of the A-46 review with such an assumption are still adequate.

6. Section 3.4 of the Summary Report also states that two-thirds of the Housner ground response spectra with peak ground acceleration of 0.04g and 0.089 for OBE [ operating-basis earthquake) and SSE. respectively, were used as the vertical ISRS regardless of location. Indicate whether the vertical ISRS used for the USI A-46 program envelop the vertical ISRS provided in the NSPC's 120-day-response. If not, provide the technical bases that support the validity of such an assumption and an explanation of how the results of the A-46 review are still adequate.

7. Discuss key examples of so-called " rigorously analyzed anchorages." as indicated on page 4-3 of the Summary Report, using hand calculations and the ANCHOR software package, and provide copies of the engineering calculations. Also discuss a few example cases of anchorage verification based on results of tug tests conducted and provide a description of the tests and applicable engineering justification for such an approach.

8. With res)ect to Section 4.1.3 of the Summary Report, the second paragrap1 of page 4-7 reads: " Wall mounted equipment was excluded as allowed by the GIP ...." Identify the specific provision of GIP-2 that allows such an exemption from performing the needed tightness check.

9. The fourth item in Table 5-1 of the Summary Report consists of the licensee's interpretation on meeting the intent of caveats for a group of small solenoid valves mounted on small piping and tubing (<1"). It indicated that the Seicmic Review Team acce)ted the seismic ruggedness of these valves by a tug test for meeting t7e intent of Bounding Spectrum Caveats 4 and 5 for Class 8. The staff notes that, as stated in GIP-2 page B.8-3. the earthquake experience data for equipment Class

1. 8 are limited to valves mounted on piping at least 1" in diameter, and the only suggested option by GIP-2 for meeting the intent of the Caveats 4 and 5 is by analysis. Provide an explanation on how the " tug test" can ensure seismic adequacy of the valves and their connected pipe or tubing.

10. The sixth item in the same Table 5-1 indicated that the piping loads a) plied to the cast-iron body of a group of solenoid valves are low and tlat they meet the intent of Bounding Spectrum Caveat 2 for Class 8 equipment, based solely on the judgement of the Seismic Review Team.

Provide more explanation to assure that, without analysis, the seismic stresses in the valve body due to piping loads are within established acceptable limit, such as less than 20% of the minimum ultimate tensile strength of the valve body material as suggested in GIP-2.

I 4

11. With respect to Table 5-1 of the Sumar.v Peaort, deviations were made to meet the GIP requirements. Provide th( p ciorage analysis calculations for the racks and panels (ID 1Bl. 2R1). & rging pumps (ID 145 041),

feedwater pumps (ID 145 201) and main control panels (ID B-1).

12. Section 6.1 of the Summary Report in Reference 1 states that some deviations and technical justifications were developed for the review of 4

the tanks and heat exchangers. Provide a sample evaluation for each of the vertical tanks (fht bottom as well as supported rn skirts and structural legs if an/) and the horizontal tanks. The evaluation of the anchors that restrain the tank movement should also be provided. If 4

NSPC used the seismic margin methodology described in the report EPRI i NP-6041 for the tank evaluations identify the nature and the extent of the deviation from GIP-2 guidelines, and provide the justification for i

its acceptance. Also, provide calculations for determining the seismic adequacy of the tanks (ID 053-251, 135-021, 153-021 and 253 021) using i the methodology described in Section 7 of the GIP-2.

. 13. Table 7-3 of the Summary Report provides a summary of the limited analytical reviews (LARs) for the selected cable and conduit raceways.

l Provide copies of the calculations of the analyses for LAR Numbers 005 and 010.

$ 14. Discuss the issue described in Information Notice 95 49 (" Seismic Adequacy of Thermo-Lag Panels") regarding Thermo-Lag panels. in i particular, the issue regarding seismic resistance capability of the cable tray and its support when appropriate weight and modulus of the

Thermo-Lag are included in the analysis.

15. Table 8-1 of the Summary Report listed 96 outliers found in 20 classes-of equipment during licensee *s USI A-46 walkdowns. However, no resolution of these outliers was provided in the resort; neither were there methods proposed to resolve these outliers. 3rovide a brief description of implemented resolution, or as a minimum, provide a proposed method to be implemented for resolution, for each outlier listed in Table 8-1.

16. Table 8-1 of the Summary Report does not show any safe-shutdown items (i.e., equipment, tanks, heat exchangers, cable trays or conduit raceways) as outliers because they are located above Elevation (EL) 755 feet. However, the screen verification data sheets in Appendix C of the Summary Report do show several items located more than 40 feet above the efTective grade (or above Elevation 755 feet), and these item were considered "OK" in meeting the seismic demand and caveats. Clarify whether any safety equipment is located above Elevation 755 feet and provide the bases for its acceptance.

-17. - Regarding the tightness check of expansion anchors performed on a representive number of mechanical and electrical components, state whether the representive number meets the sample size for expansion anchor tightnes check as listed on Table C.2-4 of the GIP.

w

18. The Relay Evaluation Report in Reference 1 identified 49 outlier relays.

However, no resolution of these outliers was provided in the report, neither were there proposed methods to resolve these outliers. Provide a brief descri) tion of implemented resolution, or as a minimum, provide a proposed metlod to be implemented for resolution, of each outlier relay listed in Appendix I of the report.

. .