ML17306B366
| ML17306B366 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 03/23/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17306B365 | List: |
| References | |
| IEIN-89-054, IEIN-89-54, NUDOCS 9303300119 | |
| Download: ML17306B366 (3) | |
Text
~P,S REC0,Mp0 0p Ihp Cy
+n
~O k~*y4 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO REACTOR COOLANT PUMP HIGH PRESSURE SEAL COOLER FOR RIZONA PUBLIC SERVICE COMPANY PALO VERDE NUCLEAR GENERATING STATION UNITS 1
2 AND 3 DOCKET NOS. 50-528 50-529 AND 50-530
1.0 INTRODUCTION
During the review of NRC Information Notice No. 89-54, "Potential Over-pressurization of the Component Cooling Water System," the licensee (Arizona Public Service Company) of Palo Verde Nuclear Generating Station (PVNGS),
Units 1, 2 and 3, identified a scenario in which a break in the reactor coolant pump high pressure seal coolers (HPSC) could potentially result in a reactor coolant system (RCS) leak being released to the outside of the containment building.
2.0 DISCUSSION AND EVALUATION The scenario involves a leak from the reactor coolant pump HPSC into the lower pressure nuclear cooling water system (NCWS).
The resulting leakage could potentially overpressurize the NCWS. If this were to occur the containment isolation valves for the NCWS would be unable to shut against the pressure or flow and the operators would be unable to identify and isolate the leaking seal cooler.
It could result in reactor coolant being discharged to the atmosphere through the NCWS surge tank relief valve located on the auxiliary building roof.
Consequently, the licensee determined that NCWS design modification was needed.
In the interim, the licensee established procedures (compensatory measures) to ensure that in the event of a failure in the
- HPSC, any leakage from the RCS would be detected in a timely manner and that the resulting off-site dose will not exceed the acceptance criteria described in the Standard Review Plan.
In addition, the licensee performed an analysis to evaluate the effects of this scenario and to justify the continued operation of PVNGS until the implementation of a permanent design change to eliminate the possibility of reactor coolant leakage through the HPSC to the atmosphere.
The modified design utilizes two new redundant safety-related safety relief valves inside containment in conjunction with the existing redundant safety-related containment isolation valves installed on the NCWS.
The installation of safety relief valves will limit the NCWS pressure to below the system 9303300il9 930323
- PDR, ADQCK 05000528(
P,-,'
design pressure and will ensure that a potential reactor coolant pump (RCP) seal cooler pipe rupture would be isolated inside containment.
The licensee indicated that modification to.the NCWS containment isolation valves is also required to ensure that each valve will close and remain closed following a loss-of coolant accident.
,In addition, PVNGS emergency operating procedures have been revised to provide direction to the operators to isolate the HPSC in the event HPSC isolation is required.
By letter dated November 3, 1992, the licensee provided the status of the Justification for Continued Operation (JCO) at the PVNGS.
The licensee indicated that the above system modification (final corrective actions) in Unit 1 had been implemented.
Accordingly, all compensatory measures require'd by the JCO have been suspended for Unit 1.
The system modification for Unit 3 is being implemented, and for Unit 2 implementation is planned during the fourth refueling outage in Spring 1993.
The JCO for Units 2 and 3, respectively, will be in effect until the implementation of the system modification is complete.
This implementation schedule is in accordance with its commitment described in the licensee's letter of April 13, 1991.
3.0 CONCLUSION
Based on our review, we find the above system modification and implementation schedule for Units 2 and 3, and the licensee's suspension of all compensatory measures required by JCO for Unit 1, to be acceptable.
Principal Contributor:
D.
Shum Date:
March 23, 1993
P II