ML19225A533

Responds to IE Bulletin 79-04.All Necessary Mods Have Been Made & Actual Valve Weights Have Been Incorporated Into Piping Analysis,Where Required

ML19225A533
Person / Time
Site:	North Anna
Issue date:	05/30/1979
From:	Brown S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 7907190511
Download: ML19225A533 (4)

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30 May 30, 1979 Mr. James P. O'Reilly, Director Serial No. 430 Office of Inspection & Enforcement PSE&C/CGC:mac: wang U. S. Nuclear Regulatory Conmission Region II Docket No. 50-339 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303

Dear Mr. O'Reilly:

We have reviewed IE Bulletin 79-04 concerning incorrect weights for 1500 psi swing check valves manuf actured by Velan. All necessary modifications have been made to North Anna Unit 2, and the actual valve weights have been incora.srated into our piping analysis where required.

Our review indicates that we have twelve 3" valves (designated 3" C58) and fourteen 6" valves (6" C58) in seismic category I piping systems in North Anna Unit 2. There are no 4", 8", or 10" 1500 psi Velan check valves in Unit 2.

We reported on March 21, 1979, under the provisions of l')CFR50.55(e) and 10CFR21, the presence of the 6" C58 valves in Unit 2. Much of the information requested in this IE Bulletin was given in our letters required by the 55(e) and Part 21; these letters were S.N.189 of March 26, 1979, S.N. 189A of April 20, 1979, and S.N. 189B of May 8, 1979. Where the reporting requirements of this bulletin exceed the information given in those letters, we will provide it herein.

Below is our response to each of the action items listed in the IE Bulletin:

1. The 3" C58 valves are located in the Safety Injection and the Chemical and Volume Control Systems. The 6" valves are located in the Safety Injection System.

2. The check valve weights used in the original stress analyses were determined from the manuf acturer's drawings. These weights were 225 lb. for the 6" C58 valve and 60 lb. for the 3" C58 valve. The correct weight of 450 lb. for the 6" C58 was identified in Westinghouse letter NAW-3365 of March 16, 1979; I.E. Bulletin 79-04 identified the correct weight of 85 lb. for the 3" C58. These corrected weights have been used in our re-evaluation.

3. Re-evaluation of the piping systems affected by the 3" and 6" C58 valves is complete. A brief description for each valve size follows:

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VIRGINtA ELECTRIC AND POWER COMPANY TO Mr. James P. O'Reilly, Director 2 3" C58) Of the twelve 3" CSS valves, four are located in the class 2 and 3 portions of the Charging System. These lines are analyzed by the simplified method described in FSAR Section 3.7.3.1.3.7. Seismic qualification of these lines is assured by conservative support spacing and by conservatively high standard support design loads. The standard load for 3" category I lines at North Anna is 1000 lb. These standards allow for various in-line components such as valves, flanges, flow restricters, etc.

The exact weight of a specific component is not required.

The remaining eight 3" C58 valves are located in Class 1 lines. They are identified below by Stress Report number, problem number, and title:

SSR-3 708&726 High Head Safety 4 Valves Injection SSR-5 1022 Pressurizer Spray 1 Valve SSR-11 744 Charging System 1 Valve Upstream of Regen. HX SSR-12 743A Ch&rging System 2 Valves Downstream of Regen. HX The method of review and evaluation of these Class 1 lines was to perform a worst case analysis in which all systems were reviewed in order to determine which would be the most severely affected by the weight change. This worst cast system was determined to be SSR-5; it was fully reanalyzed by the computer methods described in FSAR Section 3.7.3. The results showed that the increase in stress was small and that the support load chariges could be accommodated by the existing designs.

6" C58) The fourteen 6" C58 valves are located in Class 1 lines, identified below by Stress Report number, problem number, and title:

SSR-3 700, 703, 706, Safety 14 Valves 707, 724, 727, Injection 733, 734 System 7

VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. James P. O'Reilly, Director ssacy so. 3 The method of review and evaluation of these Class 1 lines was to conduct a complete reanalysis of the above stress problems with the actual valve weight. The results indicated modifications were required as listed in item 4 below.

4. No changes are required in the 3" piping nor in the associated supports due to the increased weight of the 3" C58 valves. For the 6" C58 valves, we reported in o - letter S.N.189A of April 20,1979 that 3 snubbers have been a 'ded in order to maintain the stresses below ASME code allowab.es and one rigid restraint required structural modification as a result of the increased load. The determination of where modifications were required was based on Code allowables.

The reanalysis of the worst case stress problem containing a 3" C58 valve using the actual valve weight resulted in loads on the most affected supports which still leave a 22% margin to the allowable. The highest pipe stresses resulting from this review and the allowables are summarized below:

Equation Point Calculated Allowable No. No. Stress (psi) (psi) 9 290 18,285 52,500 10 172 173,323 Not Applicable -

Code requires solving for equations 12 & 13.

12 172 27,167 51,540 13 172 4,032 51,540 12 171 27,861 51,540 13 443 43,564 52,350 The highest cumulative usage factor was at point no. 169 ond was 0.44 which is less than 1.0 and, therefore, acceptable.

The current analyses for the; system which contains the 6" C58 valves are based on the actuel valve weight, and thus the design and actual weight are the sciae.

d 353 177

VIRGINIA EMCTmC ANO POWER COMPANY TO br. James P. O'Reilly, Director swr :T No. 4

5. The analytical techniques and the computer codes used for Unit 2 are described in FSAR Section 3.7.3.

If there are any questions, please inquire.

Very truly yours, Sam C. Brown, Jr.

Senior Vice President - Po'er Station Engineering and Construction cc: Mr. John G. Davis, Acting Director Office of Inspection & Enforcement Mr. Harold R. Denton, Director Office of Nuclear Reactor Reg'21ation 7, a G ~s ) 0