ML19262B478

Responds to IE Bulletin 79-02,Revision 2, Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts. All Seismic Category I Restraints That Use Concrete Expansion Anchors Were Field Verified

ML19262B478
Person / Time
Site:	Prairie Island
Issue date:	12/07/1979
From:	Wachter L NORTHERN STATES POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-79-02, IEB-79-2, NUDOCS 7912280067
Download: ML19262B478 (2)

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NORTHERN STATES POWER COMPANY M I N N E A PO Li e. MI N N E S OTA 55408 December 7, 1979 Mr. James G. Keppler Director - Region III Office of Inspection and Enforcement United States Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 OPR-60 In response to IE Bulletin 79-02, Revision 2, the following is offered:

Our response, dated July 6, 1979, to IE Bulletin 79-02 gave the status of the program for analysis and testing. The effort described therein has continued with the following results:

1. One hundred percent of the Seismic Category I restraints that use concrete expansion anchors have been field verified with the exception of those inside Unit 2 containment which will be done during the refueling outage scheduled for January, 1980, and those that are inaccessible (< 3% of the total of 1730 restraints) . The typcci of variations found were consistent with those found outside contaicment for Units 1 and 2 and with the same frequency of appearance.

2. Direct pull tests (tensile tests) were performed on 125 concrete expansion anchor bolts used in 55 baseplates inside Unit 1 containment.

These are in addition to the 352 anchor bolts reported in the July 6, 1979, response. Two anchor bolt shells moved when tensile tested.

Their factor of safety still exceeded 4, but they were replaced and the remaining bolts in the respective plates were tensile tested satisfactorily. The tensile tests inside Unit 1 containment were conducted in the same manner as those outside containment for Units 1 and 2 as described in the July 6,1979, response. Tensile tests will be conducted inside Unit 2 containment during the refueling outage scheduled for January, 1980. The tests will be conducted in the same manner used elsewhere in Units 1 and 2 and a representative sample will be chosen.

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. NORTHERN STATES POWER COMPANY Mr. James G. Keppler December 7, 1979 Page 2

3. Stress analysis of 100% of the applicable Seismic Category I restraints that use concrete expansion anchors have been reviewed. A detailed analysis was performed on those baseplates requiring it. Of the 1730 applicable Seismic Category I restraints, 211 required redesign. Those that required immediate repair received it. The others are presently being repaired and should be completed by April, 1980. (There are a few modifications in Unit 1 containment that will be performed during refueling,1980, or the next extended outage.) All redesigned restraints will have new as-built drawings generated. These new as-built drawings will be analyzed to prove adequacy. All Seismic Category I restraints that use concrete expansion anchors were included in all phases of this effort. Applicable large and small bore piping restraints and restraints that did not use baseplates such as structural steel members (angles or channel) that were attached directly to the concrete by expansion anchor bolts with the piping attached to the structural steel member were also included.

Only 2 restraints in the plant used concrete expansion anchor bolts in a concrete block wall (one was in containment on a drain line in the CVCS and the other was on chilled water piping). In both cases, the design load was less than PU/20. If any restraints are found in Unit 2 containment that are installed in block walls, a PU/20 allowable anchor load will be applied '

(hanger drawings show no such supports in Unit 2 containment) .

The effort inside Unit 2 containment is scheduled for completion in January, 1980, with the final redesign analysis of those hangers by March, 1980.

Yours very truly, L. J. achter Vice President - Power Production and System Operation cc: Mr. G. Charnoff NRC Office of Inspection and Enforcement Washington, D.C.

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