ML17305B174
| ML17305B174 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 10/30/1990 |
| From: | Zimmerman R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Berlinger C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 9011080293 | |
| Download: ML17305B174 (4) | |
Text
p,S 0 $g Jf y REMI Wp0 UNITED STATES NUCLEAR REGULATORY COMMISSION REGION V 1450 MARIALANE,SUITE 210 WALNUTCREEK, CALIFORNIA94596
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i'ctober 30, 1990 HEYIORANDUM FOR:
C.
H. Berl.inger, Chief Generic Communications Branch FROM:
SUBJECT:
Roy Zimmerman, Director Division of Reactor Safety and Projects POTENTIAL GENERIC ISSUE, RV-90-01; PALO VERDE SINGLE FAILURE ANALYSIS FOR SBCS VALVES FOUND TO BE NOT VALID Arizona Public Service (APS) has identified what may be a potential generic issue with applicability to Combustion Engineering designs.
APS identified the situation during the post-trip review followup of a Unit 3 reactor trip which occurred on October 20, 1990.
APS reported the situation by telephone to the Headquarters Duty Officer on October 22, 1990 as an information-only call.
The Palo Verde Unit 3 trip was initiated at 100K power as a result of all Steam Bypass Control System (SBCS)
Valves modulating open resulting in an overpower condition causing a plant trip.
Subsequent engineering analysis and troubleshooting identified that the initial alarms and, spurious SBCS valves. modulation.were the result of a single power d'istributi on module failure in a balance of plant instrument cabinet.
Combustion Engineering confirmed to APS that the opening of more than one SBCV was not analyzed in the current Safety Analysis and that the design criteria for the SBCS was that no single failure would result in more than one valve opening.
t The current analysis basis for PVNGS identifies the most limiting e'vent for an Increase in Heat Removal by the Secondary System (FSAR Section 15.1) to be a Main Steam Line Break, which results in limited fuel damage and acceptable offsite dosage.
APS considers that opening of all inservice SBCVs is bounded by the consequences of this event.
The anticipated operating occurrence analyzed in the FSAR Section 15.1 is an inadvertent opening of one steam bypass control or atmospheric dump valve.
The basis for this was the assumption that no single failure would result in more than one valve opening.
The Unit 3 trip demonstrated that a single failure, outside the
- SBCS, can result in all in service valves opening.
The situation is more completely described in the licensee's
- letter, attached, dated'ctober 24, 1990.
901'1 080293 901030 PDR ADOCK 05000530 P
PNU L
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I Region V suggests that NRR evaluate this issue for generic applicability to similar Combustion Engineering designs and take such action as deemed appropriate.
If you have any questions regarding this issue, please contact D. Kirsch (FTS 463-3723) of my staff.
cc w/attachment:
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R Zimmerman, Director Division of Reactor Safety and Projects-M. Slosson, OEDO J. Dyer, NRR S. Peterson, NRR M. Virgilio, NRR C. Rossi, NRR E. Jordan, AEOD J. Martin, RV H. Wong, RV D. Coe, RV Directors, DRP, RI, RII, RIII, RIY
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