ML13317A411
| ML13317A411 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/18/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML13317A410 | List: |
| References | |
| TAC-48143, NUDOCS 8211230014 | |
| Download: ML13317A411 (10) | |
Text
SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 SAFETY EVALUATION REPORT APPENDIX R TO 10 CFR PART 50
1.0 INTRODUCTION
On February 19, 1981, the-fire protection rule for nuclear power plants, 10 CFR 50.48 and Appendix R to 10 CFR Part 50 became effective. This rule required all licensees of plants licensed prior to January 1, 1979, to submit by March.19, 1981:
(1) plans and schedules for meeting the applicable requirements of Appendix R, (2) a design description of any modification proposed to provide alternative safe shutdown capability pursuant to Section III.G.3 of Appendix R and (3) exemption requests for which the tolling provisions of Section 50.48(c)(6) was to be invoked.Section III.G of Appendix R, "Fire Protection of Safe Shutdown Capability" was retrofit to all pre-1.979 plants regardless of previous SER positions and resolutions.
The staff's previous fire protection Safety Evaluation Report dated July 19, 1979 concerning Branch Technical Position APCSB 9.5-1 indicated that in certain areas redundant systems could be damaged by a single fire which would affect safe shutdown. The staff requested the licensee to provide alternative shutdown capability for areas which could not be protected by fire barriers, fire detec tion and fire suppression systems. The SER indicated that the 4160-volt switch gear room and cable spreading room should be provided with alternative shutdown capability.
By submittal dated June 30, 1982, the licensee provided conceptual 'descriptions of the proposed modifications to the San Onofre Unit 1 plant to meet the requirements of Appendix R to 10 CFR 50,Section III.G.
The proposed modi fications will also resolve the open items from our previous SER dated July 19, 1979. Additional -information and clarification was obtained through'a-telephone conference on August-20, 1982.
511230014 8211 18 PDR ADOCK 05000206 F
-2 2.0 SYSTEMS USED FOR POST-FIRE SAFE SHUTDOWN A. Systems Required for Safe Shutdown Safe shutdown is initiated from the control room by a manual scram of the control rods.
Reactor coolant inventory and reactor shutdown reactivity are maintained by one of the two charging pumps taking suctions from the refueling water storage tank (RWST). Primary system pressure is maintained by the pressurizer heaters and spray or by a charging pump taking suctipn from the RWST combined with letdown.
For hot shutdown, decay heat removal is accomplished by the auxiliary feedwater pumps supplying water to the steam generators from the condensate storage tank. The atmospheric dump valves are used to remove heat from the st -m generator.
For cold shutdown, decay heat-removal is accomplished by the residual heat removal system andthe component cooling water system.
The salt water cooling system is used to remove heat from the component cooling water system heat exchangers to the ultimate heat sink. Additionally, the component cooling water system provides cooling for the charging pumps, the residual heat removal pumps, the reactor coolant pump oil coolers, the seal water heat exchanger and the letdown heat exchangers.
The above systems will be monitored and controlled from the control room or a remote shutdown panel and local control stations. In the event of a loss of offsite power, the diesel generators and the 125 Volt UC batteries.
will be utilized to power the safe shutdown systems. Additionally, pneumatic control valves will be provided with nitrogen gas bottles backup.
-3 B. Areas Where Alternative Safe Shutdown is Proposed The NRC staff, in its previous fire protection SER, requested that the licensee provide alternative shutdown capability for areas which could not be protected by fire barriers, fire detectors and fire suppression systems.
During discussions with the NRC staff during the week of June 14, 1982, the licensee indicated that the San Onofre Unit 1 plant would be modified to comply with Section III.G.2 of Appendix R in every fire area including the control room. The licensee was informed by the staff that the control room would need to meet Section III.G.2 or the remote shutdown panel could be considered an alternate shutdown system to the control room. Therefore, by.letter dated June 30, 1982, the licensee referring to these discussions, indicated that an alternative shutdown capability would be provided for the control room and cable spreading room by the.remote shutdown panel.
C. Remaining Plant Areas By letter dated June 30, 1982, the licensee stated that the San Onofre Unit 1 plant would be modified to comply with Section III.G.2 of Appendix R except as previously noted. Extensive plant modifications are needed to comply with Section III.G.2.. The proposed plant modifications include:
(1) the relocations of some components for the chemical and volume control system (CVCS), component cooling water system (CCW) and residual heat removal system (RHR); (2) the addition of fire barriers between pumps for the CVCS, the CCW and the RHR; (3) the additions of enclosures and fire suppression for components of the CVCS and the auxiliary feedwater system (AFW);
(4) the relocation of electrical circuits for the reactor coolant system,
-4 the CVCS, the'AFW, the main steam system, the salt water cooling system, the CCW, the RHR and the electrical power system; (5) the addition of new electrical equipment to provide separation of the redundant switchgear; (6) the addition of circuit breakers, fuses and/or isolation switches to isolate associated circuits; (7) the addition of mechanical equipment in the CVCS, the AFW (the addition of a motor driven pump) and the RHR; and (8) the addition of a nitrogen backup system. These modifications are needed to provide.the redundancy and separation requirements of Section III.G.2 of Appendix R.
D. Alternative Safe Shutdown Systems Thealternative shutdown capability will consist of a new remote shutdown panel, the existing auxiliary control panel and local control stations.
TIhnew remote shutdown panel will be located at the south end-of the Turbine Building adjacent to the existing auxiliary control panel.
The alternative shutdown capability will utilize Train 2 equipment of the systems identified in Section A above. The auxiliary feedwater pump, the atmospheric dump valves, the pressurizer heaters, the pressurizer auxiliary spray, the letdown flow and residual heat removal system flow will be controlled from the new remote shutdown panel and the auxiliary control panel.
The charging pump, the residual heat removal pumps, the salt water cooling system and the component cooling water system will be operated from local control stations. The instrumentation for the alterna tive shutdown capability will be provided at the remote shutdown panel and at a local instrument panel in the mezzanine area of the Turbine Building.
The power supply for the alternative shutdown equipment will be supplied by the diesel generator no. 2.
The design of the remote shutdown panel will include transfer switches for each valve control circuit which will disconnect the valve operator and its control system from the main control panels. Access to the remote shutdown panel will be annunciated in the main control room. The transfer switches can be used to electrically isolate the remote shutdown panel from the control room fire. A fire at the remote shutdown panel could only result in loss of control for Train 2 equipment, locally and from the control room.
3.0 EVALUATION A. PerfQrmance Goals For post-fire shutdown, the performance goals of the alternative safe shut down capability will be met using the system and equipment listed in Section 2A, above. Reactivity control will initially be provided by a I
ISNual scram of the control rods from the control room.
A Iocally caii trolled charging pump taking suction from the Refueling Water Storage Tank will provide borated water for continued shutdown reactivity control.
Pressurizer heaters, locally controlled, and the charging pump in conjunction with letdown flow will provide pressure control and reactor inventory control.
Additionally, the pressurizer auxiliary spray which can be controlled from the remote shutdown panel, will be utilized as needed for pressure control or to adjust boron concentration in the pressurizer.
Decay heat removal will initially be provided by the atmospheric.dump valves and a new motor driven auxiliary feedwater pump.
For cold shutdown, the residual heat removal system, the component cooling water system and
-6 the salt water, cooling system will be utilized for decay heat removal.
Process monitoring for safe shutdown will be provided by the instrumen tation at the remote shutdown panel and local control stations. The following instrumentation will be available at the remote shutdown panel:
pressurizer pressure, pressurizer level, reactor coolant hot leg temperature, reactor coolant delta temperature, source range neutron flux monitor, steam generator level, letdown flow and residual heat removal flow. Steam generator pressure, auxiliary feedwater flow, condensate storage tank will be available at local control station. The support systems available include the component cooling water system, the salt water cooling system, nitrogen gas bottles, the diesel generator and 125V battery supply.
B. 72-Hour Requirement The alternative shutdown systems have the capability of achieving cold shutdown within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The alternative shutdown systems can accomplish cold shutdown using only onsite power sources.
C. Repairs The design.of the alternative shutdownsystem does not utilize repairs to achieve safe shutdown.
D. Associated Circuits The licensee has conducted an extensive review of the present eletrical system to determine plant capability to meet the criteria of Appendix R.
The results of the licensee analysis indicate that approximately 300
-7 circuits would need to be relocated. Additionally, the licensee's modifi cations will include a new 4160 V switchgear and reconnection of shutdown equipment to the new switchgear. In that the licensee's design modifications are only conceptual at this time, the detailed methods of protecting the safe shutdown capability from associated circuits was not available for our review. However, the licensee has proposed methods for protecting the safe shutdown capability, as discussed in the succeeding paragraphs.
- 1. Power Source Case -
The licensee indicated that the San Onofre electri cal power distribution system includes non-safety related power circuits powered from safety-related sources. The licensee has committed to provide coordinated breakers or fuses to assure that faults on associated circuits will not cause a loss of-power to equipment required for shutdown.
- 2. Spurious Signal Cases -
The licensee's analysis of the systems needed for safe shutdown, identified the individual components in each system that were needed to assure system function. The licensee's proposed design for the remote shutdown panel and local control station will provide the capability to electrically isolate these components from the fire areas. The proposed design provides the capability to control all needed components independent of the fire area.
The licensee's analysis identified six high/low pressure interfaces where fire induced operation of the redundant valves (in series) could
-8 potentially result in a LOCA. Additionally, the licensee's proposed modi fi cati on provides an additional two high/low pressure interfaces in the residual heat removal system. For these interfaces in the residual heat removal system, the licensee proposes separating the, power and control cables into separate fire areas, for areas outside containment. For areas inside containment, the licensee proposes providing fire detection and automatic fire suppression.
For areas outside containment, the licensee's proposed separation would be adequate only if the separation provided meets the provisions of Section III.G.2 of Appendix R including the control room panel and the 'remote shutdown panel.
If the separation cannot meet Section III.G.2 criteria, we require that a positive means of preventing spurious operation of the valves be provided such as locking out the power breaker to one of the redundant.valves in each interface.
For the interfaces in the two pressurizer relief lines, the licensee proposes providing fire detection and automatic suppression inside containment and separation outside containment.
For the control room panel where the control switches are located, the licensee proposes separation per the criteria of IEEE-384. We find this separation inadequate and require the licensee to provide the capability to close the pressurizer power operated relief valve or the block valve independent of the control room. The licensee proposed similar methods for the interfaces in the letdown lines as described
-9 for the pressurizer relief lines. We also require the licensee to provide the capability of isolating the letdown lines independent of the control room. Note that this capability may exist in one of the let down lines with the nitrogen backup proposed for valve LCV-1112.. For this valve, the licensee should verify this capability.
- 3. Common Enclosure Case - The licensee's proposed modification includes rerouting approximately 300 circuit in order to provide separation as required by Section III.G.2. The licensee will be providing isolation switches for the equipment needed for the alternative shutdown capability. Additionally, the licensee has committed to provide coordinated breakers or fuses to'assure that faults on associated circuits will not cause a loss of shutdown equipment.
E. Safe Shutdown Procedures and Manpower The licensee will develop and implement written procedures for obtaining safe shutdown conditions given a fire event. This commitment is documented in a licensee's letter dated June 30, 1982. The licensee has determined that two operators and the watch engineer will be needed to provide the necessary manpower for safe shutdown operations. No fire brigade members are included in the shutdown manpower requirements..
The licensee will provide Technical Specifications governing the operability and surveillance of remote instrumentation and control and isolation switches.
4.0 CONCLUSION
Based on our review, we conclude that the licensee's proposed modifications will provide one train of systems necessary to achieve and maintain cold shutdown condition free of fire damage. Note that our review did not include the adequacy of fire detectors, fire suppression systems or fire barriers.
The licensee's conceptual design of the alternative shutdown capability for the control room and cabling spreading room complies with the requirements of Sections III.G.3 and III.L of Appendix R pending resolution of our concern' regarding high/low pressure interfaces in the final design.
5.0 ACKNOWLEDGEMENT N. Fioravante and W. Paulson contributed to this evaluation.
Dated:
NOV 18 1982.