ML20062F052

Forwards Info as Final Rept on Conservatism in Axial Pwr Distribution Monitoring Sys.Finds Significant Deficiency in Final Design Due to Rounding Off a 3-place to 2-place Decimal.Expects to Rev Tech Spec Later

ML20062F052
Person / Time
Site:	Summer
Issue date:	11/21/1978
From:	Mary Johnson SOUTH CAROLINA ELECTRIC & GAS CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 7812140057
Download: ML20062F052 (2)

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SOUTH CAROLINA. ELECTRIC h$1$iCOMPANY us's Miu La v.,310R GIA CotuMe:A, SOUTH CAROUNA 29218 ggg,g210 $9.78g.i.

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United States Nuclear Regulatory Commission ATTN:

Mr. James P. O'Reilly Director 1

Region II - Suite 1217 230 Peachtree Street, Northwest Atlanta, Georgia 30303 b'~

Subject:

V. C. Summer Nuclear Station Unit #1 Reportable Item Under 10CFR50.5) l APDMS Non-conservatism Gentlemen:

During NRC Inspection 78-25, discussions were held with the SCE&G NRC Principal Inspector in relation to information providad to the NRC by Westinghouse Electric Corporation under the requirements of 10CFR21. This information was also provided to SCE&G by telephone and applied to certain "round off" errors causing some of the set points generated for the axial power distribution monitoring system (APDMS) to be less conservative than the Technical Specification limits.

Since it appeared that this deficiency existed in the SCE&G design, it was agreed that in addition to the report I

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beftrg transmitted directly by Westinghouse, SCE&G would consider the items reportable under the requirements of 10CFR50.55(e). We have received correspondence from Westinghouse to describe the reported problem and have l

considered our course of action to assure that it is resolved inTrelation to SCE&G.

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From our evaluation of the information provided by Westinghouse', it appears that the item represents "a significant deficiency in final design as approved and released for construction, such that the design does not conform to the criteria cases stated in the Safety Analysis Report or Construction Permit". The deficiency appears to have occurred by rounding l

off a three place decimal to a two place decimal resulting in a non-conservatisa l

when comparing this rounded off value to a measured value. Westinghouse 1

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sI, Mr. Jrmes P. O'Railly Pags 2

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indicates that sensitivity studies suggest that there is margin to the 0

2,200 F LOCA limit even allowing for this potential set point error, which is the result of this non-conservatism. Westinghouse indicates that

'. T because of the complexity and amount of additional analytical work necessary to verify that the round off error would not increase the LOCA peak clad 0

temperature to a value greater than 2,200 F, the analysis has not yet

'l3;N been completed. Since it cannot therefore be established that the 2,2000F

,;iq limit would not be exceeded, this non-conservatism is being considered by

-. L, SCE&G as reportable..

As a permanent solution, SCE&G anticipates a revision of Techniul

+Z Al Specification 3/4.2.6.

It should be noted that at this time', the SCE&G Technical Specifications are not yet finalized and are being jointly reviewed by SCE&G Nuclear Operations personnel and the NRC reviewer responsible for 4

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the Sener Plant. When Westinghouse provides the information necessary to make the revision to Technical Specification 3/4.2.6, the appropriate change will be made. The SCE&G Production Engineering Department has an FSAR change.

i control system which will be utilized to assure that this item is " tracked" until it is ultimately' included as a Technical Specification revision.

SCE&G/QA has audited the Production Engineering FSAR Deviation tracking system in j -

the recent past and considers the system adequate to assure utlimate closeout of this matter.

L We consider the information herein provided as a final report on this matter.

If you desire additional information or clarification of any of the information presented, please feel free to contact us.

.Very truly yours, O

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j DAN /MCJ/jls t,

cc:

C. J. Fritz G. C. Meetze i

Office of Director of Inspection & Enforcement Washington, D. C.

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