ML17199F953
| ML17199F953 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 12/04/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17199F952 | List: |
| References | |
| IEB-80-11, NUDOCS 8612170221 | |
| Download: ML17199F953 (2) | |
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UNITED STATES
- NUCLEAR REGU.LATORV COMMISSfON WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR.REACTOR REGULATION RELATING TO IE BULLETIN 80-11, MASONRY WALL DESIGN.
COMMONWEALTH EDISON COMPANY ORESnEN NUCLEAR POWER STATION UNIT NOS. 2 AND 3 DOCKET NOS. 50-237/249 1.0 INTRODllCTION
- On May 8, 19PO, the NRC issued Inspection and Enforcement (IE)Bulletin 80-11, Masonry Wall Design, which*required lic*ensees to reeva.luate the design adequacy of safety-related masonry walls under postulated loads, including seismic load.
Commonwealth Edison Company (the licenseel responded to the bulletin by letters dated July 7, 1980, November 30, 1981, January 27, 1982, June;6, 1983,'
January 8, 1.986 and October 6, 1986.
2.0 DISCUSSION ANO EVALllATION The findings reported in this Safety Evaulation (SE) are based on the attached
- Technical Evaluation Report (TER)*prepared by Franklin Research.Center (FRC)
~s a contractor to NRC.
This TER c6ntains the details of constructjon*techniques.
used, technical information reviewed, acceptance criteria, and technical findings.*.**
- with respect to masonry wall construction at the Dresden Units.: The staff has
- reviewed this TER and concurs with its technical findings.
The following.is the
- staff's summary of the major technical findings:.
- 1.
The licensee has identified 96 safety-related masonry walls at the Dresden Units (64 in Unit 2, 32 in Unit 3). With the exception of seven
- 2.
walls discussed in item 2 below, the licensee has qua1ified the remaining walls on the basis of the working stress criteria. The licensee's reevalu-ation criteria, in general, comply with the intent of the staff acceptance c'riteria delineated in Appendix A of the TER. *.The Dresden 2 walls have * * *
- been evaluated for the Final Safety Analysis Report seismic input (Housner.
Spectrum:anchored at 0.2g) which is more conservative than the site-specific input develOped under the Systematic Evaluation Program (SEP) for the reevaluation of the Dresden site.
A total of ~even walls {Five in Unit 2 and two in Unit 3) h~ve been
- tjualified by an overturning analysis in which a cantilever (free-standing).
wall 1~ analjzed as a rigid body undergoing rocking and sliding motion.-
the factors of safety against rocking and sliding are calculated using a simple energy balance approach.
As discussed in Appendix D of the TER, the.licensee has applied this analysis in a conservative manner assuming*
adequate factors of* safety against sliding and rocking.
- Additional checks to assure that the walls maintain their structural integrity and*
act as rigid bodies during rocking and sliding are also made.
8612170221 861204 PDR ADOCK 05000237 O
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. 3.
The 1 i censee has modified 34 wa 11 s. There are two types of
. modifications:
Type 1 modifications to bring the walls in compliance with the acceptance criteria and Type 2 modifications to protect safety-related equipment from damage caused by falling blocks *
. Modifications include the following:
structural steel members installed across the face of a wall to reduce wall span or ensure two-way plate act*on the removal of courses of block to reduce wall height the installation of a compressible joint between the masonry wall and the building structure to prevent interstory drift effects
- the installation of a steel plate cover over equipment to prevent damage from falling :blocks.
- As presented in item 1, the modified walls meet the intent of the staff acceptance criteria.
- 4.
The licensee has relied on the leak-before-break concept fto support the*
1 eak-before-break concept, the 1 i ce.nsee has conducted a fracture mechanics analysis which was submitted to the staff for review) to determine the pressure loading for the walls which are affected by.
postulated.rupture of a high-energy piping system outside of the primary containment *. The.leak-before break concept is currently under the staff review as.a broad-scope rulemaking issue and its adequacy will be addressed later.
3.0 CONCLUSION
Based on the above findings, the staff concludes that.Items 2(b) and 3 of the IE Rull~tin 80-11 have been fully implemented at the Oresd~n Units and that there is*a reasonable.assurance that the safety-related masonry walls at the Dresden untis will withstand the specified design load conditions without impairment of. {a) wall integrity or (b) the performance of the required safety functions.
Principal contributor:
N. Chokshi Dated:
December 4, 1986
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