ML19290E818
| ML19290E818 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 06/19/1979 |
| From: | NRC COMMISSION (OCM) |
| To: | |
| Shared Package | |
| ML19290E817 | List: |
| References | |
| NUDOCS 8003170073 | |
| Download: ML19290E818 (7) | |
Text
{{#Wiki_filter:J uue 19, iRy STAFFPOSITION SAFE SHUTDOWN CAPABILITY Staff Concern During the staff's evaluation of fire protection programs at operating plants, one or more specific plant areas may be identified in which the staff does not have adequate assurance that a postulated fire will not damage both redundant divisions of shutdown systems. This lack of assurance in safe shutdown capability has resulted from one or both of the following situations: Case A: The licensee has not adequately identified the systems and components required for safe shutdown and their location in specific fire areas. Case B: The licensee has not demonstrated that the fire protection for specific plant areas will prevent damage to both redundant divisions of safe shutdown components identified in these areas. For Case A, the staff has required that an adequate safe shutdown analysis be performed. This evaluation includes the identification of the systems required for safe shutdown and the location of the system components in the plant. Where it is determined by this evaluation that safe snutdown components of both recundant divisions are located in the same fire area, the licens.ee. is recuired to demonstrate tnat a postulated fire will not camage both civisions or provide alternate shutcown capability as in Case B. For Case B, the staff may have recuired that an alternate shutdown capability be provided with is independent of tne area of concern or the licensee may have proposed such a capability in lieu of certain additional fire protection modifications in the area. The specific modifications associated with the area of concern along with other systems and equipment already independent of the area form the alternate shutdown capability. For each plant, the modifications needed and the combinations of systems which provide the shutdown functions may be unique for each critical area; however, the shutdown functions provided should maintain plant parameters within the bounds of the limiting safety consequences deemed acceptable for the design basis event. Staff Position. Safe shutdown capability should be demonstrated (Case A) or alternate shutdown cacability provided (Case B) in accordance with the guidelines proviced below:
- 1. Desien Basis Event The design basis event for considerir.g the need for alternate shutcown is a postulated fire in a specific fire area containing redundant safe shutcown cables / equipment in close proximity wnere it has been determined tnat fire protection means cannot assure that safe shutdown capability will be preserved.
Two ctses should be considered: (1) offsite power is available; and (2) offsite power is not available. 8003170073
- 2. Limitinc Safety Consecuences and Recuired Shutdown Functions 2.1 No fission product boundary integrity shall be affected:
a. No fuel clad damage; b. No rupture of any primary coolant boundary; c. No rupture of the containment boundary. 2.2 The reactor coolant system process variables shall be within those predicted for a loss of normal ac power. 2.3 The alternate shutdown capability shall be able to achieve and maintain subcritical conditions in the reactor, maintain reactor coolant inventory, achieve and maintain hot standby
- conditions (hot shutdown
- for a BWR) for an extended period of time, achieve cold shutdown
- conditions within 72 hours and maintain cold shutdown conditions thereafter.
As defined in the Standard Technical Specifications.
- 3. Performance Guals 3.1 The reactivity cortrol function shall be cacable of acnieving and maintaining cold shutdown reactivity conditions.
3.2 The reactor coolant makeup function shall be capable of maintaining the reactor coolant level above the top of the core for SWR's and in the pressurizer for PWR's. 3.3 The reactor heat removal function shall be capable of achieving anc maintaining decay heat removal. 3.t The process monitoring function snail be capable of providing direct readings of the process variables necessary to perform and control tne above functions. 3.5 The supporting function shall be capable of providing the process cooling, lubrication, etc. necessary to permit the operation of the equipment used for safe shutdown by the systems identified in 3.1 - 3.4. 3.6 The ecuipment and systecs used to achieve and maintain hot standby conditions (hot shutdown for a BWR) should be (1) free of fire damage; (2) capable of maintaining such conditions for an extended time period longer than 72 hours if the equipment required to achieve and maintain cold shutdown is not available due to fire darage; and (3) powered by an onsite emergency power system. 3.7 The ecuipment and systems used to achieve and maintain cold shutdown concitions should be either free of fire damage or the fire damage to such systems snould be limited such that repairs can be made and cold shutdown conditions achieved within 72 hours. Equipment and systems used prior to 72 hours after the fire should be powered by an onsite emergency power system; those used after 72 hours may be powered by
offsite power. 3.8 These systems need not be designed to (1) seismic category I criteria; (2) single failure criteria; or (3) cope with other plant accid'ents such as pipe breaks or stuck valves ( Appendix A BTP 9.5-1), except those portions of these systems which interface with or impact existing safety systems.
- 4. PWR Eouioment Generally Necessary For Hot Standby (1)
Reactivity Control Reactor trip capability (scram). Boratien capability e.g., charging pump, makeup pump or high pressure injection pump taking suction from concentrated borated water supplies, and letdown system if required. (2) Reactor Coolant Makeuo Reactor coolant makeup capability, e.g., charging pumps or the hign pressure injection pumps. Power operated relief valves may be required to reduce pressum to allow use of the high pressure injection pumps. (3) Reactor Coolant System Pressure Control Reactor pressure control capability, e.g., charging pumps or pressurizer heaters and use of the ie:cown systems if required. (4) Decay Heat Removal Decay heat removal capability, e.g., power operated relief valves (steam generator) or safety relief valves for heat removal with a water supply and emergency or auxiliary feecwater pumps for makeup to the steam generator. Service water or other pumps may be required to provide water for auxiliary feed pump suction if the condensate storage tank capacity is not adequate for 72 hours. (5) Process Monitoring Instrumentation Process monitoring capability e.g., pressurizer pressure and level, steam generator level. (6) Succort. The equipment required to support operation of the above described shutdown ecuipment e.g., component cooling water service water, etc. and onsite power sources ( AC, DC) with their associated electrical distribution system.
-4
- 5. PWR Eouioment Generally Necessary For Cold Shutdown *
(1) Reactor Coolant System Pressure Reduction to Residual Heat Removal System RHR) Cacaollity Reactor coolant system pressure reduction by cooldown using steam generator power operated mlief valves. or atmospheric dump valves. (2) Decay Heat Removal Decay heat removal capability e.g., residual heat removal system, component cooling water system and service water system to removal heat and maintain cold shutdown. (3) Succort Support capability e.g., onsite power sources (AC & DC) or offsite af ter 72 hours and the associated electrical distribution system to sucoly the above equipment. Ecuipment necessary in addition to that alreadv rovided to maintain not stancby.
- 6. BWR Ecuioment Generallv Necessary For Hot Shutcown (1) Reactivity Control Reactor trip capability (scram).
(2) Reactor Coolant Makeuo Reactor coolant inventory makeuo capability e.g., reactor core isolation cooling system (RCIC) or the high pressure coolant injection system (HPCI). (3) Reactor Pressure Control and Decay Heat Removal Depressuri:ation system valves or safety relief valves for dump to the suppression pool. The residual heat removal system in steam condensing mode, and service water system may also be used for heat removal to the ultimate heat sink. (4) Sucoression Pool Cooling Residual heat removal system (in suppression cool cooling moce) service water system to maintain hot shutdown. (5) Process Monitoring Process monitoring capacility e.g., reactor vessel level and pressure and suporession pool temperature.
. (6) Suecort Support capability e.g., ensite power source (AC & DC) and their associated distribution systems to provide for the shutdown equipment.
- 7. BWR Eouipment Generally Necessary For Cold Shutdown
- At this point the equipment necessary for hot shutdown has reduced the primary system pressure and temperature to where the RHR system may be placed in service in RHR cooling mode.
(1) Decay Heat Removal Residual heat removal system in the RHR cooling mode, service water system. (2) Succort Onsite sources ( AC & DC) or offsite af ter 72 hours and their essociated distribution systems to provide for shutcown equipment. Ecuipment provided in addition to that for achieving het shutdown.
- 8. Information Recuired For Staff Review (a)
Description of the systems or portions thereof used to pro /ide the shutcown capability and modifications required to achieve the alternate shutdown capability if recuired. (b) System design by drawings which show normal and alternate shutdown control and power circuits, location.of components and that wiring which is in the area and the wiring which is out of the area that reouired the alternate system. (c) Verification that changes to safety systems will not degrade safety systems. (e.g., new isolatien switches and control switches should meet design criteria and standards in FSAR for electrical equipment in the system that the switch is to be installed; cabinets that the switches are to be mounted in should also meet the same criteria (FSAR) as other safety related cabinets and panels; to avoid inadvertent isolation from the control room, the isolatica switches should be keylocked, or alarmed in the control room if in tne " local" or ' isolated" position; periodic checks should be made to verify switen is in the procer position for normal coeration; and a single transfer switch or otner new device should not be a source for a single failure to cause loss of redundant safety systems). (d) Verification that wiring, including power sources for the control circuit and ecuipment operation for the alternate shutdown metnod, is independent of equiprant wiring in the area to be avoided. i
s ,. (e) Verification that alternate shutdown power sources, inclu'ing d all breakers, have isolation devices on control circuits that are routed through the area to be avoided, even if the breaker is to be operated manually. ( f) Verification that licensee procedure (s) haie been developed which describe the tasks to be parformed to effect the shutdown me thod. A surmary of these procedures should be reviewed by the staff. (g) Verification that spare fuses are available for control circuits where these fuses,may be required in supplying power to control circuits used for the shutdown method and may be blown by the effects of a cable spreading room fire. The spare fuses should be located :envenient to the existing fuses. The shutdown procedure should inform the coerator to check these fuses. (n) Verification that the manpower required to cerform the snutoown functions using the procedures of (f) as well as to provide fire brigade members to fight the fire is available as required by the fire brigace technical specifications. (i) Verification that adecuate acceptance tests are performed. These should verify tnat: equipment operates from the local control station when the transfer or isolation switch is placed in the "incal" position and that the equipment cannot be operated from the control room; and tnat equip-ment operates from the control room but cannot be operated at the local control station when the transfer or isolation switch is in the " remote" position. (j) Technical Specifications of the surveillance requirements and limiting conditions for operation for that equipment not already covered by existing Tech. Specs. For example, if new isolation and control switches are added to a service water system, the existing Tech. Soec. surveillance require-ments on the service water system should add a statement similar to the following: "Every third pump test should also verify that the pump starts from the alternate shutdown station after moving all service water system isolation switches to the local control position." (k) Verification that the systems available are adequate to perform the necessary shutdown functions. The functions recuired should be based on previous analyses, if possible (e.g., in the FSAR), such as a loss of normal a.c. power or snutdown on a Group I isolation (SWR). The eouipment required for tne alternate capability should be the same or ecuivalent to tnat relied on in the above analysis.
s (1) Verification that repair procedures for cold shutdown systems are developed and material for repairs is maintained on site. =}}