ML20153E402
| ML20153E402 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 08/31/1988 |
| From: | Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CP-86-16, TXX-88598, NUDOCS 8809060315 | |
| Download: ML20153E402 (2) | |
Text
,
i MPE Log # TXX-88598 File # 10110
=
=
909.5 7UELECTRIC Ref.#10CFR50.55(e) w n. c.commu August 31, 1988 lsecuttw nce Presdent U. S. Nuclear Regulatory Commission Attn Document Control Desk Washington, D.C.
20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION 00CKET NOS. 50-445 AND 50-446 INSTRUMENTATION INSTALLATIONS SDAR: CP-86-19 (SUPPLEMENTALREPORT) j REF: SDAR CP-86-16, "Fire Effects on Instrument Tubing" i
Gentlemen:
On January 21, 1987, TV Electric notified you via TXX-6230 of a reportable deficiency pursuant to 10CFR50.55(e), involving the potential for zinc embrittlement of stainless steel instrument tubing during a fire.
TV Electric subsequently elected to discuss corrective actions for this SDAR under SDAR j
86-19 INSTRUMENT INSTALLATIONS.
The evaluations conducted to determine corrective action for this issue have identified no fire zones requiring I
modification. As a result, TV Electric is reversing the determination of reportability for SDAR CP-86-16, and the purpose of this report is to discuss the basis for this decision.
l 1
The conditions under which zinc embrittlement of stainless steel tubin can I
occur are complex, and have not been precisely defined (quantitatively by the industry. However on the basis of independent reviews conducted following events in which zinc embrittlement has occurred, it is generally acce)ted that failures require the existence of high temperatures and stresses in tie y
stainless tubing concurrently with physical contact by molten zinc.
i As a conservative approach to reviewing this issue. TO Electric identified those plant fire zones in which the combustible loading could be sufficient to 4
result in bulk room temp eratures during a fire which exceed the melting point of zinc.
These areas were then given additional evaluation taking into 4
consideration the fire protection features implemented for these areas.
These fire protection features represent a defense-in-depth concept consisting of:
I j
$ 1 1
f 8809060315 880831 PDR ADOCK 05000445 S
- 0 400 Nonk Ohn Street LBof Osths. Texas 73.Mi
IXX-88598 August 31, 1988 Page 2 of 2 a.
preventing fires from occurring, b.
Rapidly detecting and extinguishing those fires which do occur, and c.
Ensuring that )lant fires that could' burn uncontrolled would not prevent safe slutdown capability.
As a result of this defense-in-depth approach, the majority of safety related fire zones in the plant have sufficiently low combustible loading to preclude room temperatures during a fire which exceed the melting of zinc.
In fire zones where significant combustibles are 3 resent all but two areas contain firealarmandfiresuppressionsystemst1atwillensuretimelycontrolofany fires.
The other two areas are the Battery Rooms and Uninterruptable Power Supply Rooms, and do not contain instrument tubing of concern.
In summary we have concluded that implementation of the CPSES defense-in-depth fire protection program provides adequate confidence that a zine embrittlement mechanism will not result in failure of instrument tubing. Had this condition remained uncorrected, no condition adverse to the safety of 31 ant operations would have existed, and this issue is not reportable under t1e provisions of 10CFR50.55(e).
Very truly yours, 1V7V W. G. Counsil GLB/grr c-Mr. R. D. Martin, Region IV Resident Inspectors, CPSES (3)
I J