ML18152B073
| ML18152B073 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 08/11/1988 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML18152A096 | List: |
| References | |
| IEB-80-11, NUDOCS 8808160095 | |
| Download: ML18152B073 (2) | |
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e UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 ENCLOSURE SAFETY EVALUATION VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 DOCKET NOS. 50-280/281 MASONRY WALL DESIGN The findings reported in this Safety Evaluation (SE) are based on the attached Technical Evaluation Report (TER), prepared by Franklin Research Center (FRC) as a contractor to NRC.
This TER contains the details of construction techniques used, technical information reviewed, acceptance criteria, and technical findings with respect to masonry \\vall construction at the Surry Power Station, Units 1 and 2.
The NRC staff has reviewed this TER and concurs with its technical findings.
The following is our summary of the major technical findings:
- 1.
The licensee has used working stress criteria to qualify 112 safety-related masonry walls in the Surry units, along with modifications to 33 of these walls to make them compatible with the criteria.
An additional seven walls around the fuel pool, which did not comply with the licensee's working stress criteria, have now been replaced with "blow-off" siding.
The latter modifi-cation is identical to the wall modification performed at the licensee's North Anna units.
The adequacy of the siding modification has been discussed in an earlier staff Safety Evaluation Report on the spent fuel pool expansion at the North Anna units and was found acceptable.
- 2.
As discussed in Section 3.1 of the TER, the licensee's working stress criteria, as used in the re-evaluation of the masonry walls at the Surry units, either comply with or meet the intent of the staff acceptance criteria. However, the staff questions the licensee's assumptions regarding boundary conditions used in the analysis of some of the cantilevered walls. This issue is further discussed in Item 3 below.
- 3.
The licensee has made the assumption that the mortar bed joint at the base of the cantilevered wall can be used as fixed end condition.
Such a reliance on the mortar bed joint to transfer moment and prevent rotation is questionable.
Positive means in the form of clamping devices must be provided for load transfer in this situation. Therefore, to achieve staff acceptance, the cantilevered walls now relying on the mortar bed joint for the fixed end condition must be in conformance with the following s ta ff po s i ti on :
~. The cantilevered walls should be upgraded to provide positive means to prevent rotation at the fixed end conditions.
These modifications should be consistent with the staff acceptance criteria outlined in Appendix A of the TER.
Alternatively, the walls should be modified and analyzed such that the reliance on the mortar bed joint as.fixed boundary condition is not required.
Again, the modifications should render walls in compliance with the staff acceptance criteria.
Based on the above findings, the staff concludes that, with the exception of the walls requiring implementation of the staff position as discussed in Item 3 of this SE, Items 2(b) and 3 of the IE Bulletin 80-11 have been fully implemented at Surry and that there is a reasonable assurance that the safety-related masonry walls at the Surry units will withstand the specified design load conditions without impairment of (a) wall integrity or (b) the performance of the required safety functions.
Dated:
August 11, 1988 Principal Contributor:
N. Chokshi