ML20217G732

Forwards RAI Re Licensee 970426 Submittal Re USI A-46 Seismic Evaluation Rept

ML20217G732
Person / Time
Site:	Monticello
Issue date:	10/08/1997
From:	Kim T NRC (Affiliation Not Assigned)
To:	Richard Anderson NORTHERN STATES POWER CO.
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR TAC-M69460, NUDOCS 9710140175
Download: ML20217G732 (5)

Text

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4 h October 8, 1997 l

-Mr. Roger 0. Anderson. Director Licensing and Management-Issues i Northern States Power Company 414 Nicollet Hall Minneapolis, Minnesota 55401

SUBJECT:

MONTICELLO NUCLEAR GENERATING PLANT - REQUEST FOR ADDITIONAL INFORMATION RELATED TO UNRESOLVED SAFETY ISSUE (USI) A 46.

SEISMIC EVALUATION REPORT (TAC NO. M69460)

Dear Mr. Anderson:

The NRC staff has reviewed the Northern States Power (NSP) Company's April 29. 1997, submittal related to the subject USI A 46 seismic evaluation report. The sco)e of the staff's review included structural engineering, integrity of anclor bolts and seismic analysis issues. Questions related to ruggedness and integrit Additional information y of asrelays discussed have in beenthe excluded enclosure, from the reviewinscope.

is requested order for the staff to complete its review. NRC requests that NSP respond by December 19. 1997.

As a part of the overall USI A 46 review effort, the staff may conduct an on-site audit of the seismic evaluation report, related appendices, engineering calculations including Screening Evaluation Work-Sheets and Outlier Seismic Verification Sheets, and specific methods used in_ resolution of key outliers.

If you have any questions concerning this request, please contact me at (301) 415 1392.

Sincerely.

OrAginal Signed by Tae Kim, Senior Project Manager Project Directorate 111-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation ,

Docket No. 50-263 \ -

Enclosure:

As stated DFoi , i cc w/ encl: See next page l )lSTRIBUT ON:

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l Mr. Roger O. Anderson, Director Monticello Nuclear Generating Plant  :

Northem States Power Company j

cc' J. E, Silberg, Esquire , Kris Sanda, Commissioner Shaw, Pittman, Potts and Trowbrioge Department of Public Service 2300 N Street, N. W. 121 Seventh Place East Washington DC 20037 Suite 200 St. Paul, Minnesota 55101 2145 U.S. Nuclear Regulatory Commission ,

Resident inspector's Office Adonis A. Nebiett 2807 W. County Road 75 Assistant Attomey General Monticello, Minnesota 55362 Office of the Attomey General 445 Minnesota Street Plant Manager Suite 900 Monticello Nuclear Generating Plant St. Paul, Minnesota 55101 2127 ATTN: Site Licensing Northem States Power Company 2807 West County Road 75 .

Monticello, Minnesota 55362 9637 Robert Nelson, President -

Minnesota Environmental Control Citizens Association (MECCA) 1051 South McKnight Road St. Paul, Minnesota 5511g Commissioner Minnesota Pollution Control Agency

$20 Lafayette Road St. Paul, Minnesota 5511g Regional Administrator, Region 111 U.S. Nuclear Regulatory Commission 801 Warrenville Road Lisle, Illinois 60532 4351 Commissioner of Health Minnesota Department of Health 717 Delaware Street, S. E.

Minneapolis, Minnesota 55440 Daria Groshens, Auditor / Treasurer Wright County Govemment Center 10 NW Second Streni Buffalo, Minnesota 5R 15 January 1996 1 _ . . . _ _ _ _ _ _ - _ __ __ _ , - - _ _ . _ . - _ _ _ _ _ . , _ . -

' RE0 VEST FOR ADDITIONAL INFORMATION PERTAINING TO USI A 46, SEISHIC EVALUATION REPORT HONTICELLO NUCLEAR GENERATING STATION References-A. Letter from William J AH111 to NRC titled. " Response to Request for Additional Information on the Resolution of Unresolved Safety Issue A 46 (TAC No. H69460)," dated April 29, 1997 B. Letter from NRC to Northern State Power Company titled. " Request for Additional Information on the Resolution of the Unresolved Safety Issue u A 46 (TAC No. M69460)," dated January 29, 1997

1. In Reference A, the response to Question 2 stated that damping independent power spectra density (PSD) curves were generated from the available floor response spectra (FRS) to produce res)onse spectrum curves for other damping values. Provide the algoritam used in generating the

• damping independent PSD" from the original 0.5% of-critical damping FRS and the threshold criteria used for the error function. Also provide key examples of the newly generated spectra and their corresponding PSD functions.

2. Question 10 in Reference B specifically requested the rationale (supported by engineering analysis) for concluding that no large relative motion between the tank and the pump house will take place during a safe shutdown earthquake, Provide an a)p11 cable engineering I calculation supporting the conclusion stated in Reference A (as needed, refer to Standard Review Plan Section 3.7,3),

3. In Reference A, the response to Question 11 stated that "these areas were all rooms within a much larger building floor, it is estimated that these areas represent less than 2% of the area under review...." Please indicate how many rooms in the inaccessible areas consisted of the 2% of the area under review. Also, were the "CEVUE" pictures used for all of the inaccessible rooms to ascertain that the cable trays and conduits in these rooms are all well supported and show no visible degradation?

4. NSP letter to the NRC dated April 29. 1997, which provided an update on the status of NSP's response to NRC Generic Letter 87 02, Supplement 1, l indicated that the resolution of outliers listed in Table 81 of Report 91C2687.A46. "USNRC USI A 46 Resolution Seismic Evaluation Report, Monticello Nuclear Generating Plant," was completed. Provide a sumary of the specific analysis or resolution methods adopted for the outlier resolution.

5. In Reference A, the response to Question 15 implied that the peer reviewers selected a sampling of safe shutdown equipment list (SSEL) items that are located outside of the containment, the reactor water cleanup room, and main steam tunnel for the purpose of both document Enclosure

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! review and a walkdown. It is not readily obvious how the peer reviewers reached a conclusion that the remaining set of the SSEL components are acceptable based on their review /walkdown of a subset of the SSEL items.

Discuss any review work performed by the peer reviewers for the SSEL J items located within the above noted areas to support your conclusion t about the adequacy of the peer review. l l

6. In Reference A, the response to Question 21(a) indicated that the I reactor building response spectra (which is also used for buildings other than the reactor building and the emergency filtration train (EFT) building) and the EFT response spectra have in structure response spectra for elevations within 40 feet that have amplitudes higher than 1.5 times the Seismic Qualification Utilities Group (50VG) bounding s>ectrum. Please indicate whether there are any SSEL components within ticse buildings having a natural frequency of less than 8 Hz. For such components, use of the floor response spectra provided in Attachment 2 to Reference A rather than the 1.5 times the bounding spectra may be necessary.

7. In Reference A, the response to Question 21(b) indicated that for Monticello, a> plication of Generic Implementation Procedure (GIP) method A has >een completed in accordance with the requirement that the safe shutdown earthquake (SSE) is defined at the ground surface. As requested in Reference B, please provide a technical justification for not using the in structure response spectra provided in Attachment 2 to Reference A.

8. The NRC staff has concerns about the way the issue regarding the A 46 cable trays conduit raceway was being disposed of by licensees. The staff had issued requests for additional information (RAI) to several licensees on the issue. SOUG responded instead of the licensees because 500G considered the RAI to be generic in nature. The staff issued a subsequent RAI to SOUG as a follow up to SOUG's response. However, the staff found that the correspondence with SOUG did not achieve the intended results in that it did not address the technical concerns of the staff. Therefore, the staff is directing the following question to each affected licensee.

The GIP procedure recommended performing a limited analytic evaluation for selected raceways and cable trays. The procedure further recommended that when a certain cable tray system can be judged to be ductile and if the vertical load ca)acity of the anchorage can be established by a load check using t1ree times the dead weight, no further evaluation is needed to demonstrate lateral resistance to vibration from earthquakes.

The GIP procedure eliminates horizontal force evaluations by invoking" ductility. However, the staff believes that *non ductile cable trays would eventually become ductile by inelastic deformation, buckling or failure of the non ductile cable tray supports and members. The GIP procedure is a departure from conventional methods of engineering

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. 3 evaluation and the GIP does not provide an adequate bases for dealing with those cable trays that initially . ire judged to be non ductile but are eventually called Wetile by postulating failure of the lateral supports. -If this procedure was followed for eliminating cable trays for further assessment at Monticello, then all the c6ble trays could conceivably be screened out from A 46 evaluation. The following questions are to elicit information that would support the staff's safety evaluation of cable trays at Monticello.

a. Provide the total number of raceways that were classified as ductile in your A 46 evaluation and for which you did not perform a horizonta' Mad evaluation. Indicate the approximate perc6itage of such raceways as compared with the entire population of raceways.

Discuss how the ductility concept is used in your walkdown procedures,

b. Provide descriptions of all the typical configurations of ductile raceways (dimension, member size, supports, etc.) your

c. Provide justification for stating that ductile raceways need not be evaluated for horizontal load, When a reference is provided, state the page number and paragraph. The reference should be self contained, and not refer to another reference.

d. In the evaluation of the cable trays and raceways, if the ductility of the attachments is assumed in one horizontal direction, does it necessarily follow that the same system is ductile in the perpendicular direction?

e. Provide a definition of ductility in engineering terms and arovide an assessment of the maximum ductility utilized for the weatest cable tray support,

f. Discuss raceways and cable trays that are outside of the experience data by explaining what criteria are used for making a safety determination, what the configurations of such raceways and cable trays are, and how many of the raceways in number and percentage with respect to the whole population of raceways are outside the experience data? How are they going to be evaluated and disposed?

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