ML20012A295
| ML20012A295 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 02/23/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20012A293 | List: |
| References | |
| NUDOCS 9003090181 | |
| Download: ML20012A295 (6) | |
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NUCLEAR REGULATORY COMMISSION o-
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORT 1HG AMENDMENT NO.162 TO FACILITY OPERATING LICENSE NO. DPR-44 PHILADELPHIA ELECTRIC COMPANY y
PUBLIC SERVICE ELECTRIC AND GAS COMPANY i
DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC C N PEACH BOTTOM ATOMIC POWER STATION. UNIT NO. 2 DOCKET NO. 50-277 1.0. INTRODUCTION By letter dated February 14, 1990 and supplemented by letter dated February 16, 1990, Philadelphia Electric Company requested an Emergency License Amendment to Facility Operating License No. DPR-44'for the Peach Bottom Atomic Power Station, Unit No. 2.
The proposed amendment would provide for a one time extension'of the seven day limi".ing condition for operation of Technical Specification (TS) 3.5.E.2 for-continued operation with one inoperable Automatic Depressurization System (ADS) valve. The allowed outage time would be extended to 11:59 pm on March 3,1990.
2.0 BACKGROUND
During surveillance testing performed on February 12, 1990 the lice.nsee identifiedafailedelectricalcircuitforthesolenoidvalveassociated with one of the five ADS valves. The licensee postulated that-there was a failed winding in the solenoid valve which is located inside-the drywell, it was determined that plant shutdown would be necessary to fix the valve.
The licensee determined that this condition existed during surveillance testing conducted ca February 7, 1990, and that the ADS valve was inoperable at that time. Facility Technical Specifications allow seven days of operation with one valve inoperable, after which the unit is required to be shutdown and to be at a reactor system pressure at or below 105 psig within the next 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The seven day allowed outage time expired at about 2:00 p.m. on February 14, 1990.
By letter dated February 14, 1990, the licensee requested relief from TS 3.5.E.2 to allow continued operation with one inoperable ADS valve. The proposed license amendment involving an interim TS change would allow a one time extension of the seven day allowed outage time to 11:59 March 3, 1990, provided the reactor core isolation cooling (RCIC)p.m. on system remains operable.
In its submittal, the licensee stated that power levels were restricted by feedwater heater tube leaks to 80% or less of the licensed power level.
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Licensee calculations concluded that operation at the restricted power L
level will decrease the currently calculated peak clad temperature (PCT) for a small break less-of-coolant-accident (SBLOCA) from approximately l
L 1500 degrees F, which assumed operation at 100% power, to less than 1350 degrees F.
The staff understands ~that Unit 2 will continue to operate at i
or below the restricted power level discussed above until the scheduled mid-cycle outage.
The licensee discussed the results of its design basis review for ADS i
valve and system operability requirements. The review concluded that the
.high pressure coolant injection (HPCI) system, in combination with the ADS system with four operable ADS valves and low pressure core standby cooling systems -(CSCS), would be able to provide adequate core cooling for the most limiting condition recuiring ADS initiation, a SBLOCA, 1
assuming a single failure to either the ADS or HPCI system.
Results of best estimate calculations were discussed which indicated that three ADS b
valves (which assumes an additional ADS valve failure) would be sufficient t
to fulfill. the ADS safety function. In addition, results of analyses to support continued 10 CFR 50, Appendix R safe shutdown capability was presented, given that the inoperable ADS valve,' denoted as the K relief valve, was associated with the licensee's safe shutdown methcJ "D."
3.0 EVALUATION
-The staff has reviewed the licensee's submittal and reached the following conclusions:
1)
The licensee indicated that the peak cladding temperature estimated 4
for the worst-case small break LOCA (using licensing basis models) is about 1500 degrees F when performed at 100% power.
In addition operation during the period with one inoperable ADS valve will be,
limited to less than 80% power. This provides an additional reduction in PCT which the licensee in conjunction with the NSSS vendor has estimated to be approximately 150 degrees F.
The resultin relative to the requirements of 10 CFR 50 (2200 degreesF)gmargin is there-fore on the order of 850 degrees F.
2)
The number of operable ADS valves will be at least four, and the number assumed to actuate in licensing basis small break loss of coolant accident analyses was four.
The licensee is required by the proposed TS to initiate a plant shutdown if it is determined that any other ADS valve is inoperable, if the HPCI system is inoperable, or if RCIC is inoperable.
3)
The condition requiring continued cperability of the RCIC system provides assurance of additional capability to depressurize and provide coolant injection at operating pressure, w
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Best estimate calculations of small break LOCAs for BWR/3 and BWR/4 p(assuming 100% power), calculated peak clad temperatures will notlan exceed 2200 degrees F.
5)
Operation with one inoperable ADS valve is limited to a short time.
period, until March 3, 1990.
6)
The safety valve (spring actuated) function of the inoperable ADS valve is still operable and will function for overpressurization protection.
7)
The licensee has reviewed fire protection requirements for shutdown from alternate control stations and has determined that the combination of HPCI, two ADS valves, and low pressure CSCS is sufficient to depres-surize the. plant and remove decay heat following a fire which prevents safe shutdown from the main control' room.
Besed on the supporting analyses discussed above, we find operation with one inoperable ADS valve acceptable until 11:59 p.m. on March 3, 1990.
4.0 EMERGENCY CIRCUMSTANCES In its February 14, 1990 letter, the licensee requested that its application for license amendment be processed as an emergency change per 10 CFR 50.91(a)(5).and that a-Temporary Waiver of Compliance be. granted until the license amendment was approved. During surveillance testing performed on February 12, 1990, the licensee identified a failed electrical circuit for the solenoid valve associated with one of the five ADS valves.. The licensee postulated that there was'a failed winding in the solenoid valve which is located inside the drywell.
It was determined that plant shutdown would be necessary to fix the valve. The licensee determined that this condition existed during surveillance testing conducted on February 7, 1990, and that the ADS valve was inoperable at that time. Facility Technical Specifications allow seven days of operation with one valve inoperable, after which the unit is required to be shutdown and to be at a reactor system pressure at or below 105 psig within the next 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The seven day allowed outage time expired at about 2:00 p.m. on February 14, 1990. The licensee stated that although the inoperability of the valve was traced back to February 7, 1990, identification of the situation at that time would not have allowed sufficient time for the normal or exigent processing of a license amendment. The emergency license-amendment would allow operation to continue until a mid-cycle outage which was scheduled to begin on March 3, 1990.
The NRC staff concluded a preliminary review of the licensee's request and agreed that a plant shutdown to fix the inoperable ADS valve was unnecessary prior to the scheduled mid-cycle outage. On February 14, 1990, the staff granted a Temporary Waiver of Compliance which was immediately effective and remained in effect until the proposed license
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amendment was issued. The staff has reviewed the circumstances associated with the licensee's request for an emergency Technical Specifications.
i change. Without the proposed change Peach Bottom, Unit 2 would be forced into an unnecessary shutdown. Additionally, this condition could not J
have been reasonably foreseen prior to this time as it is a direct result i
of the identification of an inoperable ADS valve during surveillance-testing performed on February 7 and February 12, 1990.
It is therefore -
3 concludedthatthischangesatisfiesthecriteriaof10CFR50.91(a)(5).
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5.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMItlATION
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The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a-license amendment involves no s
significant hazards consideration if operation of the facility in accordance with the amendment would not:
(1)L Involve a significant increase in the probability or consequences of an accident previously evaluated; or 4
(2) Create the po'ssibility of a new or different kind of accident from any accident previously evaluated; or
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Involve a significant reduction in a margin of safety.
The licensee proposed that the proposed TS chanpe did not involve significant hazards censideration. Based on a review of the' licensee's determination, the staff has determined the following:
1.
The Irability of the inoperable ADS valve to perform its Automatic l
Depressurization System function is not considered to increase the orobebility of a previously evaluated accident. Although the failure of the inoperable valve to perform its ADS function will affect plant response to an intermediate or small break LOCA, the inoperability of the ADS valve is not considered to be related to a potential accident initiator.
Based on a review of the facility's updated final safety analysis report (UFSAR) discussions on the ADS valves, it was concluded that the open circuit for the solenoid valve associated with the in-L operable ADS valve does not affect the overpressurization protection capability of the ADS valve or increase the probability of the ADS u
valve failing in the open position.
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A single failure to either the HPCI system or the ADS system would not prevent the existing operating condition with four ADS valves operable with low pressure Core Standby Cooling Systems (CSCS), in conjunction with High Pressure Coolant Injection, to provide for adequate core cooling for intermediate and small brea( loss-of-coolant-accidents. One inoperable ADS valve does not affect the operability of the four remaining ADS valves. LOCA analyses presented in the facility's UFSAR were based on maintaining four ADS valves operable.
In addition,10 CFR 50, Appendix R safe shutdown capability y
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will also be assured with the K ADS valve inoperable because for safe shutdown method "D," only two of the three provided nuclear system pressure relief valves are. required. Licensee engineering calculations
- releted to Appendix' R safe shutdown analyses has determined that only two nuclear system pressure relief valves are required for low pressure CSCS to renove decay heat after reactor shutdown.
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,Therefore, operation of the facility in accordance with the proposed l
amendment would not involve a significant increase in the probability or consequences of an accident previously evaluated.
2.
A single ADS valve out of service has already been evaluated in the
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UFSAR. The failure mode of the inoperable ADS valve an electrical
.open circuit, does not interfere with the pressure re, lief valve
_,o function. Adequate core cooling ability during small-and intermediate break LOCA's is.not affected given that LOCA analyses presented in _
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.the facility's UFSAR were based on maintaining four ADS valves
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operable. Additional assurance of. adequate core cooling exists with!
continued operation at less than 80% of the licensed power. level and with the requirement for continued RCIC system operability.. Therefore, operation.of the facility in accordance with the proposed amendment would not create the possibility of a new or different kind of accident from any previously evaluated.
3.
The current LOCA analysis assumes four ADS valves are operable. The large break LOCA peak clad temperature margin is' unchanged since the ADS does not initiate during this scenario. The small and intermediate break PCT margin is not-significantly reduced with four operable ADS valves given that LOCA anelyses presented in the facility's UFSAR -
were based on maintaining four ADS. valves operable. The currently analyzed small and _ intermediate break LOCA PCT is on the order cf i
1500 F which is significantly below the 2200 degrees F PCT limit.
In ac'dition, operation at less than 80% of the licensed power level provides an additional reduction in PCT estimated to be approximately 150 degrees F.
Finally, if another ADS valve, HPCI or RCIC becomes ino:erable, an orderly shutdown will be initiated per facility Tecinical Specification 3.5.E.3.
It is therefore concluded that operation of the facility in accordance with the proposed amendment would not involve a signifi-cant reduction in a margin of safety.
Based on the above discussion the staff concludes that this amendment rieets the criteria and therefore does not involve a significant hazards consideration.
6.0. STATE CONSULTATION The Commonwealth of Pennsylvania was consulted on this matter and had no comments on the determination, 4
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7.0 ENVIRONMENTAL CONSIDERATION
S This. amendment involves a change to a. requirement with respect to the installation or use of a fecility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amerdment involves no significant increase in the amounts, and no significant change -in the _ types, of any effluents that riey be released offsite erd that there is no significant increese in individual or cumulative occupational radiation cFp0sure. The Commission has made a final no significant ha:ards
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finding with respect to this amendment., Accordingly, this amendment meets the elicibility criteric for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact staterent nr environmental crsessment need be prepar,ed in connection wit 1 the issuance of this mendment.
8.0 CONCLUSION
The staff has. concluded, based on the considerations discussed above, that: ' (1) the amendment does not (a) significantly increase the probability or consequences of an accident previously evaluated (b) increase the possibility of a new or different kind of accident from any previously evaluated or (c) significantly reduce a safety margin and, therefore, the amendment does not involve significant hazards consideration; (2) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner; and (3) public such activities will be conducted in compliance with the Commission's-regulations,
- and the-issuance of this amendment will not be inimical to the comon defense and security nor to the health and safety cf the public.
Principal Contributors:
T. E. Collins and G. Y. Suh Dated: February 23, 1990 E
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