ML20091E067
| ML20091E067 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 05/25/1984 |
| From: | Jens W DETROIT EDISON CO. |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| EF2-68-206, NUDOCS 8406010037 | |
| Download: ML20091E067 (2) | |
Text
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a Cayne H. Jena clear tons Deholt Edison E?ti!P3" May 25, 1984 EF2-68,206 Director of Nuclear Reactor Regulation Attention:
Mr.
B.
J.-Youngblood, Chief Licensing Branch No. 1 Division of Licensing U.
S. Nuclear Regulatory Commission Washington, D.
C.
20555
Dear Mr. Youngblood:
References:
(1)
Fermi-2 NRC Docket No. 50-341 (2)
Letter B.
J.
Youngblood to W.
H.
- Jens,
" Request for Additional Information for the Fermi 2 Facility Regarding a Postulated Failure of a HPCI Steam Line Without Isolation", February 22, 1984
Subject:
HPCI Steam Line Isolation Valve Integrity Reference 2 identified an ACRS concern regarding a postulated HPCI steam line break coupled with the failure to close of both the inboard and outboard isolation valves. Tne letter requested Detroit Edison to provide information on HPCI-steam line isolation valves at Fermi 2.
Consistent with the solution preposed in the reference (2) letter, the Fermi 2 design presently requires the outboard isolation valve on the HPCI steam line to be maintained in the closed position.
To permit rapid startup of the HPCI system, while minimizing thermal stresses on the piping, the HPCI steam line is kept hot by requiring both the inboard isolation valve and the (1-inch) bypass valve-around ' the outboard isolation valve to ' be kept open.
n-PDR ADO oh! g A
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OfyO
Mr.
B. J. Youngblood May 25, 1984 EF2-68,206-Page 2 In response to an isolation signal due to a postulated break in the HPCI steam line downstream of the outboard isolation valve, both the 1" outboard valve and the 10" inboard valve would automatically close.
Steam flow from this break would be limited by the 1" outboard bypass valve.
Furthermore, reliability of this isolation system is enhanced by the diversity in size of the isolation valves and the fact that they-mast close only against the flowrate allowed by the 1" valve.
Accordingly,-testing to verify valve closure, under full-flow conditions, is not required.
The environmental effects of this postulated break in.the steam tunnel, HPCI room, and torus room were conservatively calculated based on the valve alignment described, and it was found that the environmental qualification conditions for systems in the steam tunnel, torus room, and the corner rooms are bounded by other events.
No other ECCS equipment would be adversely affected by a postulated break in the HPCI room.
Finally, the-probability of a HPCI steam line break during HPCI operation is considered to be negligible due to the limited operating time of this system and the fact that the steam line is preheated by the 1" bypass.
The preceding discussion should resolve the ACRS concern.
The various purchase, design and testing documents specif-ically rcquested in Reference 2 are available for your review and audit at the Fermi 2 site.
If you have any questions regarding3this issue, please contact Mr..O. Keener Earle at'(313) 586-4211.
Sincerely, cc:
Mr.
P.
M. Byron Mr. M.
D. Lynch USNRC, Document Control Desk Washington, D.C.
20555 I
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