ML20083N869
| ML20083N869 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 04/10/1984 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Harold Denton, John Miller Office of Nuclear Reactor Regulation |
| References | |
| TAC-57063, TAC-57064, NUDOCS 8404190312 | |
| Download: ML20083N869 (2) | |
Text
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l WISCONSIN Electnc mwen couraur 231 W. MICHIGAN, P.O. BOX 2046, MILWAUKEE, WI 53201 April 10, 1984 Mr. H.
R. Denton, Director Office of Nuclear Reactor Regulation U.
S.
NUCLEAR REGULATORY COMMISSION Washington, D. C.
20555 Attention:
Mr.
J.
R. Miller, Chief Op" rating Reactors, Branch 3 Gentlemen:
DOCKET NOS. 50-266 AND 50-301 REACTOR CAVITY ANNULUS SEAL RING POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 In a letter dated October 2, 1979 Wisconsin Electric Power Company, licensee for the Point Beach Nuclear Plant, was directed to either provide an analysis demonstrating that the reactor cavity annulus seal ring would not become a destructive missile in the event of reactor vessel cavity rapid pressurization due to a loss-of-coolant-accident (LOCA) pipe break or commit to removing the seal ring from the vicinity of the annulus.
Although we did not concur that the seal ring would cause any damage to safety-related systems in the event of a LOCA pipe break and pressurization, we agreed in our letter dated December 20, 1979.
to raise the seal ring more than twelve feet above the cavity floor to remove the seal ring from the vicinity of the annulus.
We, subsequently, revised this commitment in our letter dated July 27,, 1983 to maintain the seal ring at a height of eight feet or more above the cavity floor.
On February 1, 1984 in Generic Letter 84-04 to all operating PWR licensees, Mr. Darrel G. Eisenhut forwarded the results of the NRC staff's safety evaluation of the Westinghouse Owner's Group's topical reports dealing with elimination of postulated pipe breaks in PWR primary system main coolant loops (Unresolved Safety Issue A-2).
In that evaluation, the Staff concludes that an acceptable technical basis has been provided so that the asymmetric blowdown loads resulting from double-ended pipe breaks in main coolant piping need not be considered as a design basis for Westinghouse Owner's Group plants, which includes the Point Beach Nuclear Plant, Units 1 and 2.
The fracture mechanics
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believe it is h 7eet a cavity annulus seal ring greater than eig tspecifically a main coolant the basis of the concern,in a sudden pressurization of the floor since impingement on the loop pipe break resulting cavity around the reactor vessel causing jet i
need no longer be considered as a design bas s.your permission to restore seal ring, we hereby request location originally Accordingly, reactor cavity seal rings to the stowage sufficiently above the cavity is, designed for the plant, thatflow through the annulus.
floor to permit cooling air l be Your consideration and response to this request wil 2 refueling A response prior to the Point Beach Unit appreciated.this fall would be satisfactory.
outage Very truly yours, Q) i L.ig 43 g
/
Vice President-Nuclear Power C.
W.
Fay Inspector Copy to NRC Resident
//
/
I Mr. II.
R.
Denton April 10, 1984 analyses contained in the topical reports demonstra' sed that the potential for a significant failure of the stainles, steel primary piping was low enough that pipe whip or jet impingement devices for any postulated pipe locations in the main loop piping should not be required.
In light of these conclusions, we no longer believe it is appropriate to continue to suspend the reactor cavity annulus seal ring greater than eight feet above the cavity floor since the basis of the concern, specifically a main coolant loop pipe break resulting in a sudden pressurization of the cavity around the reactor vessel causing jet impingement on the seal ring, need no longer be considered as a design basis.
Accordingly, we hereby request your permission to restore the reactor cavity seal rings to the stowage location originally designed for the plant, that is, sufficiently above the cavity floor to permit cooling air flow through the annulus.
Your consideration and response to this request will be appreciated.
A response prior to the Point Beach Unit 2 refueling outage this fall would be satisfactory.
Very truly yours,
?fiU a Vice President-Nuclear Power C.
W.
Fay Copy to NRC Resident Inspector