ML20207F139

Safety Evaluation Supporting Util Responses to IE Bulletin 80-11, Masonry Wall Design, W/Exception of One Open Item

ML20207F139
Person / Time
Site:	North Anna
Issue date:	08/12/1988
From:	NRC
To:
Shared Package
ML20151K754	List: ML20151K749 ML20207F021 ML20207F139
References
IEB-80-11, NUDOCS 8808180225
Download: ML20207F139 (3)

Text

y -

,9 n )g UNITED STATES

[('

• t g

j NUCLEAR REGULATORY COMMISSION WASHING TON, D. C. 20666

\,

/ ENCLOSURE SAFETY EVALUATION VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 DOCKET NOS. 50-338/339 MASONRY WALL DESIGN The findings reported in this Safety Evaluation Report (SER) are based on the attached Technical Evaluation Report (TER), Attachment 1, prepared by Franklin Research Center (FRC) as a contractor tc NRC. This TER contains the details of construction techniques used, technical information reviewed, acceptance criteria, and technical findings with respect to nasonry wall construction at North A,nna units. The staff has reviewed this TER and concurs with its technical findings. The following is our surcary of the major technical findings:

1. The licensee has used working stress criteria to qualify 55 safety related masonry walls ir the North Anna units. An additional 15 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 adequacy of this repair has been discussed in the earlier staff Safety Evaluation Report on the spent fuel pool expansion issue at the North Anna units and was found acceptable.

2. As discussed in Section 3.1 nf the TER, the licensee's working

-gm stress criteria, as used in the re-evaluatinn of the masonry walls

@8 co mo at the North Anna units, either comply with or meet the intent n s:

h co <

of the staff acceptance criteria. However, the staff questions g the licensee's assumptions regarding boundary conoitions used in oce

@@c, the analysis of some of the cantilevered walls. This issue is further discussed in Iten 3 below.

4 . . ,

e

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 staff position:

The cantilevered walls should be upgraded to provida 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 SER, the It.!ms 2(b) and 3 of the IE Bulletin 80-11 have been fully implemented at North Anna and that there is a reasonable assurance

s-. .. .

q -

that the safety-related masonry walls at North Anna 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 12, 1988 Principal Contributor:

N. Chokshi 1

.