ML20206D174

Safety Evaluation Supporting Util Response to IE Bulletin 80-11 Re Reevaluation & Testing Requirements in Items 2(b) & 3 Concerning Masonry Wall Design

ML20206D174
Person / Time
Site:	Pilgrim
Issue date:	06/06/1986
From:	Office of Nuclear Reactor Regulation
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Shared Package
ML20205N862	List: ML20205N857 ML20206D122 ML20206D174
References
IEB-80-11, NUDOCS 8606190665
Download: ML20206D174 (3)

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%...../ SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO MASONRY WALL DESIGN, IE BULLETIN 80-11 30STON EDIS0N COMPANY PILGRIM NUCLEAR POWER STATION UNIT 1 DOCKET N0. 50-293

1.0 INTRODUCTION

The NRC issued IE Bulletin 80-11 on May 8, 1980, requiring power reactor licensees to identify and describe the functions of all masonry walls at their nuclear facilities which are in proximity to or have attachments from safety-related piping or equipment such that wall failure could affect a safety-related system. Licensees were also required to re-evaluate the adequacy of these walls to perform their intended functions under postulated

, loads and to submit a written report upon completion of their re-evaluation programs. ,

The Boston Edison Company (licensee) responded to the IE Bulletin and subsequent NRC requests for additional information concerning Pilgrim Unit 1 in numerous submittals and meetings beginning on July 14, 1980 and ending on December 31, 1985. The findings in this Safety Evaluation are based on the enclosed Technical Evaluation Report (TER-C5506-158) prepared by Franklin Research Center (FRC) as a contractor to the NRC.

2.0 EVALUATION The TER contains the details of construction techniques used, technical information revised, acceptance criteria, and technical findings with respect to masonry wall construction at Pilgrim Station. The staff has reviewed this TER and concurs with its technical findings. The following is our sumary of the major technical findings:

1

1. The licensee has identified 242 safety-related masonry walls at the Pilgrim Station. Except for 11 walls discussed in Items 2 and 3 below, these walls have been qualified using the licensee's criteria. Those criteria comply with the intent of the staff's (Appendix A of the TER). As discussed on acceptance criteria.

l page 34 and in Appendix B of the TER, the licensee's evaluation l of the wall boundary strengths, which partly relies on statistical analysis of the results of the field testing, is judged to be conservative and, therefore, acceptable. The licensee's two-way cracked plate analysis approach was reviewed in considerable detail by the staff, FRC and FRC's consultants. The Pilgrim walls are reinforced vertically at every other cell, with the cell fully grouted. Joint reinforcement is also installed along the horizontal 8606190665 860606 PDR ADOCK 05000293  ;

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- direction (a number of walls also have horizontal bond beams with reinforcing steel). The licensee's analysis employed finite element orthotropic plate bending models. The reduction in the wall rigidity

- was accounted for by using Rranson's equation. In the horizontal direction, if the moment exceeded the unreinforced allowable moment, the section was assumed to be cracked and unable to transmit any load (i.e., the element stiffness in the horizontal direction is set to zero, contribution from grout cores or joint reinforcement was neglected). Rased on the discussion in Appendix B of the TER and the review of sample calculations, the licensee's plate analysis approach is found to be acceptable.

2. In a letter dated December 31, 1985, the licensee informed the staff that three walls in the cable spreading room (194.17, 194.?1 and 194.22) will not qualify for the tornado depressurization loads without considerable modification. Such a modification would require extensive relocation of safety-related cable and conduit to provide access for the structural modification. This would recuire a station outage, involve a lengthy construction schedule, and raise concerns about the extensive interruptions to safety systems.

The above walls only affect safety-related components in the cable spreading room (CSR). The alternate shutdown system backs un the affected components assuming a fire in the CSR. Since a masonry wall collapse is no more damaging than a fire, safe shutdown can be achieved and maintained. Therefore, in lieu of modifyino these walls, the licensee has made procedural chances which require the in Miation of a plant shutdown upon receipt of a tornado alert from the area load dispatcher. The procedure advises the operators that shutdown via the alternate shutdown process may be required.

In addition, the licensee also noted that the critical load, a tornado, is a unidirectional load which would cause a failure away from CSR. The walls are qualified as is to withstand all other design basis loads (i.e., seismic). Thus, even in the event of wall failure, the safety-related components in the CSR would be expected to remain essentially intact. Based on the above discussion, the staff finds the licensee's approach acceptable.

3. Eloht walls in the radwaste corridor (191.29, 191.37, 193.11, 193.12, 193.5,193.6,193.7, and 193.8) are presently classified as safety related solely because of two safety-related cables which are in the zone of influence of these walls. During the next refueling outage (RF0 #7), these two cables will be re-routed out of the zone of )

influence of these walls in order to meet Appendix R requirements. '

I Upon completion of the above mentioned re-routino, these eight walls will be reclassified as nonsafety-related. The licensee has indicated that it will not attempt to " qualify" these walls for safety-related service in the interim. The staff concurs with the licensee's approach as these walls will not be considered safety-related by the next refueling outape.

4. The licensee has modified 88 masonry walls in the Pilgrim Station.

These modifications consist of adding structural steel members

- that act as intermediate supports or boundary reinforcements. The licensee's approach to the wall modifications has been found acceptable as the modified walls comply with the intent of the staff acceptance criteria.

3.0 CONCLUSION

Based on the above findings, the staff concludes that the re-evaluation and testing requirements in Items 2(b) and 3 of IE Bulletin 80-11 have been met for the Pilgrim Station and that there is reasonable assurance that the safety-related masonry walls at Pilgrim will withstand the specific design load conditions without impairment of (a) wall integrity or (b) the performance of required safety functions.

Principal Contributor: N. Chokshi Dated: June 6, 1986 4

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