TXX-6957, Interim Deficiency Rept CP-87-90 Re Relief Valve Piping Connecting to RHR Pump Suction Piping.Initially Reported on 870903.Design Mod Initiated to Comply W/Asme Section III Code.Next Rept Will Be Submitted by 880215
| ML20236S304 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 11/20/1987 |
| From: | Counsil W, John Marshall TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CP-87-90, TXX-6957, NUDOCS 8711250040 | |
| Download: ML20236S304 (2) | |
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E E' Log # TXX-6957
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File # 10110
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905.4 Ref # 10CFR50.55(e)
MlELECTR/C wmi.m c. coman -
November 20, 1987 Executive Via President U. S.: Nuclear Regulatory Commission
" ATTN:
Document Control Desk
. Washington, D.C.
20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) 00CKET'NOS. 50-445 AND 50-446 RilR REllEF VALVE PIPING SDAR:.CP-87-90 (INTERIM REPORT)
Gentlemen:
On September 3,1987, we. verbally notified your Mr. H. S. Phillips of a
.possible-design deficiency regarding relief valve piping connecting to the Residual Heat. Removal (RHR) Pump suction piping.
We have concluded that this deficiency is reportable under the provisions of 10CFR50.55(e) and the
. required information follows.
L DESCRIPT10N' The physical arrangement of the RllR pump suction relief valves inlet piping prevents the valves (1-8708 A and B) from meeting their design basis relieving requirements. 'This' condition is due to the excessive elevation (over 22 ft.)
and~ distance-(over 100 ft.) of the valves from the RHR suction piping.
An l
~ increase in pump suction pressure, when combined with relief valve inlet line losses, elevation head between the relief valves and the RHR pumps, and pump head, could cause the pump discharge piping pressure to exceed the ASME Code allowable value (design + 10"s per NC-7311b) by as much as 15 percent.
This
' condition.does not meet the requirements of paragraphs NC-7141c and NC-7311b l
of.the'ASME B&PV Code,Section III.
Valve chattering could also occur due to the rapid reduction in the valve inlet pressure as soon as the valve lifts.
SAFETY IMPLICATIONS The RHR system serves as an Emergency Core Cooling System (ECCS) during the injection and recirculation phases of a loss of Coolant Accident (LOCA), and
-is in operalion during post-accident plant cooldown.
The potential loss of the RHR system could impair the ability to mitigate the consequences of a DBA-f LOCA or to achieve and maintain safe shutdown.
Had this condition remained uncorrected, it could have led to an overstress of the RHR pump discharge piping which could adversely affect the safety of plant operations.
8711250040 871120 7
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.vovember 11', 1987 j
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CORRECTIVE ACTION-A design modification has been initiated to relocate the relief valves to j
comply with the requirements of the ASME Section 111 code, as well as climinate the large friction loss:in the inlet: piping of the relief valves and a significant portion of the elevation difference between the valves and the suction lines.
Our next re) ort on this issue will be submitted no later than February 15, 1988.
In tie report, we will provide our. assessment of the cause and implications of.this issue and the schedule for completion of corrective actions.
Very truly yours, 6th S, 0cn,1 sd.
W. G. Counsil By: i Ji S. Marshall Supervisor, Generic Licensing CBC/mgt'
. c - Mr. R. D.-Martin, Region IV Resident inspectors, CPSES (3) i
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