ML17311B180
| ML17311B180 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 09/06/1995 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17311B178 | List: |
| References | |
| NUDOCS 9509140199 | |
| Download: ML17311B180 (6) | |
Text
gy,'R RE0I
~P Cy 0
O
~o
++*+~
~
~
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.
TO FACILITY OPERATING LICENSE NO.
NPF-41 AMENDMENT NO.
87 TO FACILITY OPERATING LICENSE NO.
NPF-51 AND AMENDMENT NO.
70 TO FACILITY OPERATING LICENSE NO. NPF-74 ARIZONA PUBLIC SERVICE COMPANY ET AL.
PALO VERDE NUCLEAR GENERATING STATION UNIT NOS.
1 2
AND 3 DOCKET NOS.
STN 50-528 STN 50-529 AND STN 50-530 1.0.
INTRODUCTION By application dated June 17, 1994, the Arizona Public Service Company (APS or the licensee) requested changes to the Technical Specifications (TS)
(Appendix A to Facility Operating License Nos.
NPF-41, NPF-51, and NPF-74, respectively) for the Palo Verde Nuclear Generating Station, Units 1, 2, and 3.
The Arizona Public Service Company submitted this request on behalf of itself, the Salt River Project Agricultural Improvement and Power District, Southern California Edison
- Company, El Paso Electric Company, Public Service Company of New
- Mexico, Los Angeles Department of Water and Power, and Southern California Public Power Authority.
The proposed changes would revise the surveillance requirement and Bases section of TS 4.7. 1.6 to increase the minimum nitrogen accumulator pressure for the atmospheric dump valves (ADVs) from 400 psig to
~615 psig.
2.0 BACKGROUND
The licensee has recently reanalyzed the design basis for nitrogen accumulator sizing.
The limiting factor is ADV availability to reach COLD SHUTDOWN under natural circulation conditions in the event of failure of normal circulation, including failure of the normal control air system.
The licensee has submitted operating plant data for the assumptions used by Combustion Engineering in a computer simulation of the cooldown.
The data were obtained during Unit 1 post-fuel-load natural circulation testing.
All four ADV accumulators were monitored.
The requirements for cycling the ADVs were factored into the calculation for the nitrogen tank pressure accumulator and found to be conservative for cold shutdown.
The analysis showed that the ADVs are required to operate for 13.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />, not for the previously calculated 10.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.
A minimum 615-psig accumulator pressure is required to ensure ADV availability during a natural circulation cooldown.
This discrepancy was not identified until the recent design basis reevaluation.
950914019"P 950906 PDR ADOCK 05000528 P
.4t 4i Pg l
r
'll
The requirement to maintain the nitrogen accumulator pressure at >615 psig ensures that sufficient nitrogen is in the accumulator to operate the associated ADV in HOT STANDBY and to allow the unit to reach COLD SHUTDOWN under natural circulation conditions should the normal control air system fail.
TS 4.7. 1.6 ensures that a minimum number of ADVs are available for plant cooldown.
The accident analysis in Chapter 15 of the Updated Final Safety Analysis Report (UFSAR) credits the ADVs for use in cooling down a unit in the event of a loss of offsite power.
A loss of,offsite power would cause the main condenser to be lost as a heat sink.
The ADVs in conjunction with the auxiliary feedwater system would provide the heat removal function for long-term heat removal and cooldown.
3.0 DESCRIPTION
OF PROPOSED CHANGES Revise Technical Specifications (TS) and Bases to increase the minimum nitrogen accumulator pressure from 400 psig to >615 psig because of the design basis change for the accumulator.
- 4. 0 EVALUATION UFSAR Section 6.3.3.4 assumes operation of the ADVs for long-term heat removal and cooldown.
The ADVs are not credited in Chapter 15 events until 30 minutes after the initiating event.
One ADV per steam generator is assumed available for the duration of the long-.term cooling event.
The licensee has administrative controls in place to maintain nitrogen accumulator pressure between 650 and 680 psig.
The staff verified that the nitrogen-pressure-regulating valves are properly sized from both a pressure and a flow standpoint.
,Nitrogen pressure from the accumulator will continue to be reduced to 105 psig prior to use in the operation of the ADVs.
The requirement to maintain the nitrogen accumulator at a pressure
>615 psig ensures that sufficient nitrogen is in the accumulator to operate the associated ADV.
The licensee's recalculations concluded that a pressure of 615 psig ensures sufficient nitrogen for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of operation at HOT STANDBY and 9.3 more hours of operation to reach COLD SHUTDOWN under natural circulation conditions should the normal control air system fail.
These changes correct an existing discrepancy regarding proper nitrogen accumulator pressure for the ADVs.
Actual operation of the ADVs remains unchanged.
The increased nitrogen pressure allows for continued operability of the ADVs to meet the previously reviewed time to reach cold shutdown.
The licensee's revised minimum nitrogen pressure is based on operating experience rather than on theoretical assumptions.
These changes support the continued operability of the ADVs and are, therefore, acceptable.
4>
a>
5.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Arizona State official was notified of the proposed issuance of the amendments.
The State official had no comments.
- 6. 0 ENVIRONMENTAL CONSIDERATION The amendments change surveillance requirements.
The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released
- offsite, and that. there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a
proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (59 FR 42333).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed
- above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed
- manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
C.
Thomas Date:
September 6,
1995
!I'
+i ~
~r hl l
P E