ML20059L294
| ML20059L294 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 01/26/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20059L292 | List: |
| References | |
| NUDOCS 9402030346 | |
| Download: ML20059L294 (5) | |
Text
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED AMENDMENT NO. 30 TO FACILITY OPERATING LICENSE NO. NPF-85 PHILADELPHIA ELECTRIC COMPANY LIMERICK GENERATING STATION. UNIT 2 DOCKET NO. 50-353 l
1.0 INTRODUCTION
8y letter dated August 27, 1993, as supplemented by letters dated November 10, and December 20, 1993, the Philadelphia Electric Company (the licensee) submitted a request for changes to the Limerick Generating Station, Unit 2, Technical Specifications (TS).
The requested changes would allow a one-time TS change to extend the allowed outage time (A0T) for the Unit 2 residual heat removal service water (RHRSW) as well as the suppression pool spray (SPS) and suppression pool cooling (SPC) modes of the residual heat removal (RHR) system from 72, 168 (i.e. seven days), and 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, respectively, to 288 hours0.00333 days <br />0.08 hours <br />4.761905e-4 weeks <br />1.09584e-4 months <br /> (i.e., twelve days).
The extended A0Ts would be needed on two (2) separate-occasions during the fifth Unit I refueling outage scheduled to begin on January 29, 1994.
These changes apply to Unit 2 TS Sections. 3.6.2.2,
" Suppression Pool Spray," 3.6.2.3, " Suppression Pool Cooling," and 3.7.1.1,
" Residual Heat Removal Service Water System - Common System." The extended A0Ts would allow continued Unit 2 operation _while maintenance isolation valves are to be installed on both loops of the RHRSW system.
The RHRSW' system is common to both Unit I and Unit 2.
Operation of Unit I will continue to comply l
with the applicable Unit 1 TS A0Ts.
The November 10 and December 20, 1993 l
supplemental letters provided clarifying information and did not change the l
original no significant hazards consideration determination.
2.0 EVALUATION The licensee has proposed that Sections 3.6.2.2, Action a, and 3.6.2.3, Action a, of the TS, be modified to allow the SPS and SPC modes of one RHR subsystem to be inoperable for 288 hours0.00333 days <br />0.08 hours <br />4.761905e-4 weeks <br />1.09584e-4 months <br />, and Section 3.7.1.1, Action a.3, be-modified to allow one subsystem of RHRSW to be inoperable for 288 hours0.00333 days <br />0.08 hours <br />4.761905e-4 weeks <br />1.09584e-4 months <br />.
These temporary amendments would allow continued Unit 2 operation during the installation of maintenance isolation valves upstream of RHR heat exchanger inlet valves, HV-51-1(2)F014A(B), and downstream of RHR heat exchanger outlet valves, HV-51-1(2)F068A(B), on both loops of the RHRSW system.
The RHRSW system is common to both Unit 1 and Unit 2.
During this modification, Unit I will be in the fifth refueling outage and will continue to comply with the applicable Unit 1 TS A0Ts for RHRSW.
The Unit 1 TS requirements for the SPS and SPC modes of RHR are not applicable while Unit 1 is in refueling.
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The removal of either 'A' or 'B' RHRSW loop from service will impact the.
operability of the Unit I and Unit 2.RHR heat exchangers in the affected loop.
The RHR heat exchangers provide decay heat removal for normal shutdown cooling and primary containment suppression pool /drywell temperature and pressure control for accident mitigation.
1 The two loops of shutdown cooling are required to be operable in accordance l
with TS Sections 3.4.9.1 (0PCON 3 - Hot Shutdown) and 3.4.9.2 (OPCON 4 - Cold t
Shutdown). Otherwise, an alternate method of decay heat removal is required.
If Unit 2 is required to be shut down, only one RHRSW loop would be operable.
For this condition, the alternate decay heat removal will be available by establishing a shutdown cooling path through the automatic depressurization system (ADS) valves together with suppression pool ' cooling or by using the main turbine condenser as a heat sink when the offsite power is available.
t The staff concludes that these methods would satisfy the shutdown cooling.
requirements while the reactor is in OPCONs 3 and 4.
For the OPCON 5 condition, alter rte decay heat removal can be provided by the Reactor Water Cleanup (RWCU)
- am. The staff finds this approach would satisfy the shutdown cooling requirements following plant shutdown.
The Updated Final Safety Analysis Report (UFSAR) Section 6.2 states that one operable RHR heat exchanger is adequate for accident mitigation.
Two (2) i accident scenarios with one (1) operable RHR heat exchanger are presented in the UFSAR:
(1) the operable RHR heat exchanger is placed in service in the RHR drywell spray and suppression pool spray mode while one RHR pump is in low pressure coolant injection (LPCI) mode of operation and one core spray (CS) loop injects water into the reactor vessel, (2) the operable RHR heat exchanger is placed in service along with an associated RHR pump taking suction from the suppression pool and discharging to the reactor vessel.. Both scenarios assume a loss of offsite power (LOOP), the availability of high t
pressure coolant injection (HPCI) system for the duration of the accident, initial suppression pool temperature and RHRSW temperature at their maximum t
values, all the decay heat from the reactor vessel being rejected through the one operable RHR heat exchanger, and the RHR heat exchanger-in a fully fouled i
condition. For the bounding case of a postulated rupture of a reactor recirculation line, the peak containment pressure is higher for the second scenario, but the pressure is still much less than the containment design pressure.
The RHRSW system was designed with sufficient capacity for one loop of RHRSW with two (2) RHRSW pumps in operation and two (2) spray pond spray networks to mitigate a design basis accident (DBA) on one unit and allow the safe shutdown i
of the other unit, as described in the UFSAR, Section 9.2.3.
The licensee intends to minimize the decay heat load from Unit 1 on'the lone operable RHRSW loop. The licensee does not plan to remove the 'A' or 'B' loop of RHRSW from. service until the Unit I decay heat generation has decreased to a level that will allow the removal of one RHR heat. exchanger from service.
At.this time, cold shutdown would be established, the decay heat generation would be reduced, the spent fuel pool cooling and cleanup system could be
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..: 1 placed in service to remove decay heat from Unit 1, and the recirculation pump'
'i or an RHR pump could be placed in service to assist in decay. heat removal.
Furthermore, draining of the Unit I reactor cavity would not be allowed until both loops of RHRSW are returned to service or an alternate decay heat removal method is available.
Therefore, since one loop of RHRSW can mitigate a DBA on one unit and support the safe shutdown of the other unit, the potential heat removal requirements with respect to Unit 2 during the period that these proposed TS changes will be in effect, is within the capacity of one RHRSW loop.
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A single failure could render the RHR heat exchanger or the RHRSW loop i
inoperable during the proposed extended A0T. However, by limiting the time an RHRSW loop is out of service while maintaining one of the Unit 2. RHR heat exchangers and the associated RHRSW loop operable, the consequences of an accident will remain unchanged.
The staff has reviewed the licensee assessment of the components that can affect the performance of the Unit 2 RHR heat exchanger or a loop of RHRSW, and found the information presented regarding the components' operation, power supplies, failure rates, testing and maintenance, to be acceptable.
The removal of the 'A' or 'B' RHRSW loop from service will not affect the capability of any emergency core cooling systems (ECCS) from injecting water into the reactor vessel.
The RHRSW system is manually operated and is not required during the first ten (10) minutes of an accident.
Therefore, the a
short-term li.e., less than ten minutes) emergency core cooling capability of
. Unit 2 ECCS is unaffected.
The long-term.(i.e., longer than ten minutes) cooling requirements will be met by the operable Unit 2 RHR heat exchanger and i
the associated operable RHRSW loop with the RHR system in either.the SPS or the SPC mode of operation. Additional removal of Unit 2 equipment'and/or systems will be allowed in accordance with existing TS requirements as long as i
the removal does not adversely affect the operability of the RHRSW loop as j
well as the operable ".PS and SPC modes of RHR operation, or places Unit 2 outside of the analysis described in UFSAR, Section 6.2.
The removal of either of the two (2) RHRSW loops from service will affect the emergency service water (ESW) system.
The return flow from the ESW system joins the RHRSW system, and shares one path for each ESW loop to the spray pond. When the 'A' RHRSW loop is inoperable, both ESW loops will be aligned to return to the
'B' RHRSW loop. When the 'B' RHRSW is inoperable, both ESW loops will be aligned to return to the
'A' RHRSW loop. These alignments are within the design capabilities of the ESW system'and will be controlled by approved procedures. -The licensee has performed a computer analysis of the flow distribution to components cooled.by ESW, which indicated that sufficient ESU flow is available to support operability ~ of essential components.
Additionally, the licensee will perform ESW system flow measurements on the most limiting components to validate component and/or system operability.
Physical work on either the 'A' or the 'B' RHRSW loop will not begin until-both loops of the' ESW system are verified to be operable.
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The staff requested information about the availability of training or operational guidance to aid plant operators during a Unit 2 LOCA if it were to s
occur during the proposed A0T. The licensee has stated in a response, by letter dated November 10, 1993, that operations personnel are qualified by-periodic training in response to and mitigation of a DBA, including the actions needed to ensure decay heat removal.
Furthermore, procedures are in-place which cover safe plant shutdown and, as mentioned above, decay heat a
removal for situations applicable to those in the proposed A0Ts.
Decay heat removal for Unit 2 would be provided by the RHR system, the remaining operable RHR heat exchanger, and the associated operable RHRSW loop.
The licensee will emphasize the Unit 2 operational configuration during the proposed extended A0T with a special procedure, in accordance with LGS Administrative Procedure A-23, " Generation and Performance of Special i
Procedures, Modification Acceptance Test, and Plant Evolution /Special Test i
Procedures." Procedure A-23 requires licensee to include in the special procedures the identification of the differences in the system line-ups, plant configuration, operating procedures, and steps to brief operations personnel associated with the operational configurations.
Also, the licensee has committed to confirm the operability of the systems required to mitigate the effects of a Unit 2 LOCA during the proposed extended A0Ts by addressing those systems in the special procedures. These sys'. cms are the remaining loop of RHRSW, the assaciated RHR loop and heat exchanger, the ESW system, the associated emergency diesel generators, the HPCI system,.the CS system and at least one alternate decay heat removal method, depending on OPCON, such as ADS, the main condenser, or RWCU.
In addition, the special i
procedures will require that these systems be verified by operations personnel to be in compliance with respect to individual technical specifications surveillance requirements prior to entry into and during the proposed extended A0Ts.
Furthermore, any testing of these systems would be accomplished, to every extent possible, such that no testing would be performed during the time that the plant is in the condition permitted by the proposed extended ACTS.
To ensure adequate heat removal capability for the accident scenario of a LOCA/ LOOP on one unit and a simultaneous safe shutdown of the other unit, the
.i RHRSW system is designed such that the A0T for operation with less than three (3) RHRSW pumps operable along with their associated operable emergency diesel generators (EDGs), is limited to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The reduction in margin of safety associated with increasing the A0Ts from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and 168 hours0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br /> to 288 hours0.00333 days <br />0.08 hours <br />4.761905e-4 weeks <br />1.09584e-4 months <br /> is minimal, since the reduction reflects a small increase in the probability that a LOCA/ LOOP event would occur on Unit 2 during the 288-hour A0T pericd as compared during the 72-hour A0T period currently allowed by the TS. The licensee has supported this conclusion with a probabilistic risk assessment evaluation.
The results indicated that the increased risk of extending the A0T for TS Section 3.6.2.2, Action a, TS Section 3.6.2.3, Action a, and TS-i Section 3.7.1.1, Action a.3 to 288 hours0.00333 days <br />0.08 hours <br />4.761905e-4 weeks <br />1.09584e-4 months <br /> is minimal.
Furthermore, the 9
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licensee has committed to establish a fire watch for those areas'where fire could damage the systems necessary to support decay heat removal through the
' lone operable RWRSW loop.
The staff has evaluated the proposed one-time extension of the A0Ts for the RHRSW system as _well as the SPS and the SPC modes of the RHR system from 72, 168 (i.e., seven days), and 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, respectively, to 288 hours0.00333 days <br />0.08 hours <br />4.761905e-4 weeks <br />1.09584e-4 months <br /> (i.e., twelve days), while the maintenance isclation valves are being installed on both loops of the RHRSW system.
Based on the evaluation, the staff concludes-that the proposed TS change is acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendment.
The State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20..The NRC staff has determined that the amendment involves 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 _
t significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a' proposed finding that the amendment involves no significant hazards consideration, and there has been_ no public comment on such finding (58 FR 50970). Accordingly, the amendment meets 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 amendment.
5.0 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 amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
F. Rinaldi
)
T. Liu r
S. Jones Date: January 26, 1994 i
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