ML13322B047

Forwards Request for Addl Info Re Intake Structure Repair Due to Identification of Addl Degradation During Recent Surveillance.Response Expected within 90 Days of Receipt of Ltr

ML13322B047
Person / Time
Site:	San Onofre
Issue date:	11/06/1989
From:	Trammell C Office of Nuclear Reactor Regulation
To:	Ray H Southern California Edison Co
References
TAC-74168, NUDOCS 8911130072
Download: ML13322B047 (8)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 lop November 6, 1989 Docket No. 50-206 Mr. Harold B. Ray Vice President Southern California Edison Company Irvine Operations Center 23 Parker Irvine, California 92718

SUBJECT:

INTAKE STRUCTURE REPAIR, SAN ONOFRE NUCLEAR GENERATING STATION, UNIT NO. 1 (TAC NO. 74168)

References:

1. LER No.84-008 dated September 5, 1984

2. SCE Letter dated October 18, 1984,

Subject:

Intake Structure Degradation and Repair.

3. NRC Letter dated April 24, 1985,

Subject:

Intake Structure Corrosion and Repair

4. NRC Letter dated July 11, 1986,

Subject:

Long-Term Service Seismic Reevaluation Program

5. Second Surveillance Report for SONGS Unit 1 Intake Structure (Cycle X Refueling Outage) dated March, 1989 References 1 and 2 provided information relative to degradation of the Unit 1 intake structure. This matter was reviewed by the NRC staff as documented in References 3 and 4 and resolution of the condition by Southern California Edison Company (SCE) was judged to be acceptable. During your most recent surveillance of the Unit 1 intake structure (Reference 5), additional degradation was identified. Due to the continuing nature of intake structure degradation, the NRC staff is reviewing the current status and adequacy of intake structure repair. We have determined that the information identified in the enclosure is required to facilitate our review. Please provide your response within 90 days of your receipt of this letter.

Following receipt of your response, we plan to meet with you at the site for an in-depth discussion of this matter.

8911130072 891106 PDR ADOCK 05000206 P

PNU

Hdrold November 6, 1989 The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required under Pub. L.96-511.

Please contact us if you should have any questions regarding this request.

Sincerely, Charles M. Trammell, Senior Project Manager Project Directorate V Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation

Enclosure:

Request for Additional Information cc:

w/enclosure See next page

Mr. Harold B. Ray San Onofre Nuclear Generating Southern California Edison Company Station, Unit No. 1 cc David R. Pigott Mr. F. B. Marsh, Project Manager Orrick, Herrington & Sutcliffe Bechtel Power Corporation 600 Montgomery Street P. 0. Box 60860 Sari Francisco, California 94111 Terminal Annex Los Angeles, California 90060 Mr. Robert G. Lacy Manager, Nuclear San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Resident Inspector/San Onofre NPS U.S. NRC P. 0. Box 4329 San Clemente, California 92672 Mayor City of San Clemente San Clemente, California 92672 Chairman Board of Supervisors County of San Diego 1600 Pacific Highway Room 335 San, Diego, California 92101 Regional Administrator, Region V U.S. Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 WalnuE Creek, California 94596 Mr. John Hickman Senior Health Physicist Environmental Radioactive Management Unit Environmental Management Branch State Department of Health Services 714 P Street, Room 616 Sacramento. California 95814 Mr. Don Womeldorf Chief Environmental Management California Department of Health 714 P Street, Room 616 Sacramento, California 95814

ENCLOSURE RAI ON REPAIR OF DEGRADATION OF INTAKE STRUCTURE AT SONGS-1

1. It is quite obvious from the reports (references 2,3) of the first and second surveillances that the rebar corrosion is a continuing process which does not seem to slow down. In spite of the installed modifications, the chloride penetration is going to keep on increasing (though no such observations are made during the surveillances). Provide justification to show that the presently implemented patch-work modifications are sufficient to ensure the integrity of the structure through the remaining plant-life.

2. The core samples taken to measure chloride content in 1984 appeared to indicate low (300 ppm) chloride levels on the back-fill side of the walls (ref. 1).

However, that chloride level may not reflect the conditions below the ground water level and underneath the base slabs.

Provide information on methods of assessing the conditions of concrete in these inaccessible areas.

3. Some reinforced concrete walls (DCP attached to ref. 3) have been considered to be able to withstand the postulated load combinations if their unreinforced (excluding 3" loss due to degradation) moment capacities have been shown larger than the maximum moments due to the postulated load combinations. Provide computations showing the calculations of resisting moment capacity (Mt). Provide information on how the postulated seismic loadings were calculated. It is anticipated that wide-spread degradation will change the model characteristics; and the seismic responses could be quite different. Provide information on how the potential changes in responses were incorporated in arriving at the applied loads.

4. Provide information similar to that requested in "3" above for the plated reinforced concrete walls. Was there any testing performed to understand the behavior of installed modifications (including plate action, composite action, bolt deformation and grout performance)? If yes, provide information on the results of such tests. If no, provide assumptions used in the assessment of the composite behavior considering the potential degradation of concrete between the plates.

5. Provide cross-sectional details of sections (1-1 to 8-8) shown on the attached sketch (Attachment 1) indicating grade levels, water levels (normal and fluctuations), wall and slab thicknesses, beam dimensions, reinforcing provided, major embedments in concrete, and pump support locations. Also, indicate ground water fluctuations in the backfill, and foundation strata below the base slabs and around the tunnel.

-2

6.

We are concerned about the overall integrity of the structure to perform its safety function for the remaining plant-life. Provide information on other corrective measures that could be implemented to preserve the integrity of the structure.

References

1. Report Attached to the SCE letter dated October 18, 1984.

2.

Report of the First Surveillance for SONGS Unit 1 Intake Structure dated June 11, 1986.

3. Second Surveillance Report for SONGS Unit 1 dated March, 1989.

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Harold November 6, 1989 The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required under Pub. L.96-511.

Please contact us if you should have any questions regarding this request.

Sincerely, original signed by Charles M. Trammell, Senior Project Manager Project Directorate V Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation

Enclosure:

Request for Additional Information cc:

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INTAKE STRUCTURE RAI