ML20246F716

Suppls 890503 Response to NRC Bulletin 88-011, Pressurizer Surge Line Thermal Stratification Pressurizer Nozzle Loads Evaluation. Increased Nozzle Loads Will Not Affect Structural Integrity of Pressurizer Surge Line & Shell

ML20246F716
Person / Time
Site:	North Anna
Issue date:	07/05/1989
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-006C, 89-6C, IEB-88-011, IEB-88-11, NUDOCS 8907130378
Download: ML20246F716 (3)

Text

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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 )

July 5, 1989 United States Nuclear Regulatory Commission Serial No. 89-006C Attention: Document Control Desk PES /AVB R2 Washington, D. C. 20555 Docket No. 50-339 )

License No. NPF-7

]

Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY i NORTH ANNA POWER STATION UNIT 2 RESPONSE TO NRC BULLETIN NO. 88-11 PRESSURIZER SURGE LINE THERMAL STRATIFICATION PRESSURIZER NOZZLE LOADS EVALUATION q As discussed in our letter (Serial No. 89-006A) dated May 3,1989, Virginia Electric ,

and Power Company committed to complete a pressurizer nozzle loads evaluation for j North Anna Power Station Unit 2. This letter provides the results of the evaluation performed for the Unit 2 pressurizer surge nozzle. The evaluation was necessary 4 because the calculated loads for the pressurizer surge nozzle exceeded the allowable loads specified by the equipment manufacturer when the effects of thermal stratification were factored into the surge line analysis.

A detailed analysis was performed by the equipment manufacturer to determine if the pressurizer surge nozzle and shell will maintain its structural integrity throughout the remaining life of the plant. The analysis results at the worst location of the pressurizer surge nor:zle and shell are:

Maximum Stress = 41.0 ksi (<3Sm)

Maximum Cumulative Usage Factor = 0.35 These results indicate that the pressurizer surge nozzle and shell meet the stress and fatigue analysis requirements of the ASME Code, Section 111, 1968 Edition through Winter '68 Addenda, Article 4. Therefore, the effect of increased nozzle loads due to thermal stratification will not affect the structuralintegrity of the pressurizer surge line and shell through the remaining life of the plant. The effect of increased loads on the pressurizer supports due to thermal stratification is already enveloped by higher pipe rupture and safety valve discharge loads as indicated in our May 3,1989, letter.

Very truly yours, I W A

\)M' W. L. Stewart Senior Vice President - Power

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cc: U. S. Nuclear Regulatory Commission Region ll 101 Marietta Street, N. W.

Suite 2900 Atlanta, Georgia 30323 Mr. J. L Caldwell NRC Senior Resident inspector North Anna Power Station I

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3 COMMONWEALTHOFVIRGINIA )

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COUNTYOFHENRICO )

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today' by W. L. Stewart who is Senior Vice President - Power, of Virginia Electric and Power Company. He is duly authorized to execute and file the foregoing document in behalf of that Company, and the statements in.the document are true to the best of his knowledge and belief.

Acknowledged before me this 8 day of /s , 1989_.

My Commission Expires: adfoeso ,JS 1_ff_.

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" Notary Yublic l

(SEAL)

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