ML19260E152
| ML19260E152 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 12/17/1979 |
| From: | Schwencer A Office of Nuclear Reactor Regulation |
| To: | Profitt W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| References | |
| NUDOCS 8002130484 | |
| Download: ML19260E152 (3) | |
Text
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NUCLEAR REGULATORY COMMISSION
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.\\Y E Decenb er 17, 1979 Docket Nos. 50-280 and 50-281 Mr. W. L. P roffitt Senior Vice President - Power Virginia Electric and Power Company Post Cffice Box 26666 Richm:nd, Virginia 23261
Dear ':
- r. ? roffitt:
We are centinuing our review of the S.-w Pwer Station, Units ics. I anc 2 Inser< ice Testing Drogre (IST).
're ci:' y:ur a tention to tne fact tna; the Reac::r Safety Study (RSS) identif'ed : s pc er.tial intersystem LCC; (rlAS' 140: ever.t V) as a significant con rib.:'an o the risk resulti.g ir core celt.
In Ob's scenario, the two in-series cr.ec-va ves in the injecti:n lines c# the low ; essure safety injection (LPS:) s/s ems are postulated to fail allovng hig" :ressure reactor coolant to c:m-/': ate with low pressure ri-ir; cursice c ont a' nre nt.
Rupture of the low press.re systen would result in loss of reactor coolant catside containment and su:sec.ent c:re reltdown.
The average failure probability of the S;rry check valves was calculated in the.SS to be 4x10-6/ year with an esti a ed scror factor of aoproxicately 10.
o This :robability is in the range genera!'y a:ce: table for other higb consequence events.
Mcwever, the averaging in Sur j was dcne over five yea-s o' lar-op e -a-i o r..
A calculation of the a.e-a;e pr:: ability for plant :pera: ion :eyor.d the #'ve years indicates an increase i
- he average failure pro: ability Men there is no periodic leak testing f : e che:k valves.
We have nc 'nfor ation to incica e that measures are bein; ta<e-by VE?C0 to perfore periccic tests to assure that each barrier check valve 's
- lcing.
Since Surrj Uni : Mcs.1 and 2 have been operating for abou; seis years, we expect that the avera;e probabili y has increased.
It is a necessary but not sufficiert c:rtiti:n to have an adequate level of isolation (barriers) between the reac:cr co:: art system (RCS) and tre inter-conre::ing LPSI system.
It continues c be :ur position that licensees rust demonstrate that the design integrity f s mai-tained throughout :lant life by per'::ically testing at least two :ar-f e vs~ves (valves which :erf m a press.re isolation function) in each '_::: s ster line that connects
- the RCS.
Je :ensider that periodic test" ; -ou': :e a sufficient c:ndi-icn.
This as been substantiated by risk assessmen studies perforne: by 'i: :.
'D]u{D wB a d/n@L, P DWT 8002130 489
"r. W. L. P roffitt December 17, 1979 3arrier valves, such as those in the Surry 1 and 2 LPSI system, which pedor-a pressure isolation function are being considered by us during our review cf the Surry Units Nos.1 and 2 IST program. However, because our overall review of your IST program is not near completion and there may be a long leac time to purchase hardware if needed, we have accelerated our review of the IST program with respect to the LPSI system barrier valves and have concluded that you should take irmediate action to initiate periodic testing of these barrict check valves each refueling. The valves which need to be indivicually leak tested are as folicws for both Surry Units Nos.1 and 2:
SI-79, SI-82, SI-85, SI-241, SI-242 and SI-243.
It is requested that you take the necessary action to periodically test the valves as seca as practica!.
For Unit No. 2, you should plan to provide the testing capability and tests prior to Unit Mc. 2 startup. Please provide us with your schedule for doing so within 20 days of the receipt of this letter.
Si ncerely,
/
~
'guYL(Qi V A. Schwencer, Chief Operating Reactors Branch #1 Division of Operating Reactors
Mr. W. L. Proffitt Virginia Electric and Power Company Decer.5er '.7,1979 cc:
Mr. Michael W. Maupin Hunton and Williams Post Office Box 1535 Richmond, Virginia 23213 Swem Library College of William and Mary Williamsburg, Virginia 23185 Donald J. Burke U. S. Nuclear Regulatory Commission Region II Office of Inspection and Enforcement 101 Marietta Street, Suite 3100 Atlanta. Georgia 30303
.