ML19242A525
| ML19242A525 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 06/22/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19242A523 | List: |
| References | |
| NUDOCS 7908030080 | |
| Download: ML19242A525 (7) | |
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MAINE YANKEE NUCLEAR POWER PLANT EVALUATION OF FIRE PROTECTION SER OPEN ITEM 3.2.1 Safe Shutdown During our previous evaluation we identified eleven plant areas in which there may be a potential for a fire to adversely affect redundar.t divisions of safety The licensee asserted, for each area of concern, chat the facility systems.
has the capacity to safely shut down in the event of a fire. The licensee agreed to provide additional infomation to demonstrate the capability to achieve safe shut down conditions in the event of a fire in any one of the areas.
The additional information was required because prior submittals lacked an adequate description of the separation between redundant safe shutdown This infomation was needed to allow the staff to cables within the areas.
determine whether the existing separation, in conjunction with the fire protection proposed by the licensee, was adequate to assure that safe shut-down capability would not be lost as a result of fire in these areas.
Without this infomation, the staff could not make such a determination and would then require that an alternate shutdown capability be provided independent of the existing capability. The additional infomation has been provided in the licensee's submittal WMY 78-52, dated May 31, 1978.
In WMY 78-52, the licensee states that for each of the areas, safe shutdown capability does exist even if the area was completely burned out and briefly describes the shutdown capability that would be available. We have reviewed the infomation and find that in most of the areas addressed by the licensee, our minimum requirements regarding safe shutdown capability are not met and the description of separation and fire protection measures is not adequate to assure safe shuttown capability.
The licensee should show how our minimum requirents regarding sai'e shutdown capability are met for fires which cause loss of tne. cables for each of the identified areas. This provision of alternate shutdown capability is to satisfy separation concerns and does not relieve the licensee from providing fire protection for safety-related equipment and cables.
Our minimum require-ments for safe shutdown capability are described in the attached staff position.
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STAFF POSITION SAFE SHUTDOWN CAPABILITY Staff Concern During the staff's evaluation of fire protection programs at operating plants, cne 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 shutdewn 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 systens required for safe shutdown and the location of the system components in the plant. Where it is determined by this evaluation that safe shttdown components of both redundant divisions are located in the same fire area, the licensee is required to demonstrate that a postulated fire will not damage both divisions or provide alternate shutdown capability as in Case B.
For Case B, the staff may have required that an alternate shutdown capability be provided with is independent of the area of concern or the licensee may have proposed such a capability in lieu of certain additicnal fire protection modifications in the area. The specific modifications associated with the area cf cor.cern 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 shculd be demonstrated (Case A) or alternate shutdcwn capability provided (Case B) in accordance with the guidelines provided below:
- 1. Desian Basis Event The design basis event for considering the need for alternate shttdown is a postulated fire in a specific fire area containing redundant safe shutdown cables / equipment in close proximity where it has been cetermined that fire protection means cannot assure that safe shutdown capability will be preserved.
Two cases should be considered: (1) offsite power is available; and (2) offsite power is not available.
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. 2. Limiting Safety Consecuences and Raouired Shutdown Fu,1ctions 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 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and maintain cold shutdown conditions thereafter.
As defined in the Standard Technical Specifications.
- 3. Performance Goals 3.1 The reactivity control function shall be capable of achieving and maintaining cold shutdown reactivity conditions.
3.2 The reactor coolant makeup function shall be capable of maintaining the reactor coplant level above the top of the core for BUR's and in the pressurizer for PWR's.
3.3 The reactor heat removal function shall be capable of achieving and maintaining decay heat removal.
3.4 The process monitoring function shall be capable of providing direct readings of the process variables necessary to perform and control the above functions.
3.5 The supporting fur.ction shall be capable of providing the process cooling, lubrication, etc. necessary to permit tne operation of the equipment used for safe shutdcwn by the sy:tems identified in 3.1 - 3.4.
3.6 The equipment and systens 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 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> if the equipment required to achieve and maintain cold shutdcwn is not available due to fire damage; and (3) powered by an ensite emergency power system.
3.7 The equipment and systems used to achieve and maintain cold shutdown conditions should be either free of fire damage or the fire damage to such systems should be limited such that rerairs can be made and cold shutdown conditions achieved witnin 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Equipment and systems used prior to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after the fire should be powered by an onsite emergency power system; those used after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> may be powered by RPO
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3.8 These systems need not be designed to (1) seismic category I criteria; (2) single failure criteria; or (3) cope with other plant accidents 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 Equipment Generally Necessary For Hot Standby (1) Reactivity Control Rr tor trip capability (scram). Beration capability e.g.,
cho.ging 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 high pressure injection pumps.
Power operated relief valves may be required to reduce pressure 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 letdown 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 feedwater 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 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
(5) Process Monitorino Instrumentation Process monitoring capability e.g., pressurizer pressure and level, steam generator level.
(6) Succor.
The equipment required to support operation of the above described shutdown equipment e.g., comoonent cooling water service water, etc. and cnsite pcwer sources ( AC, DC) with their associated electrical distribution system.
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. 5. PWR Equipment Generally Necessary For Cold Shutdown *
(1) Reactor Coolant System Pressure Reduction to Residual Heat Removal System (RHR Capac111ty Reactor coolant system pressure reduction by cooldown using steam generator power operated relief valves or atmospheric dump valves.
(2) Decay Heat Removal Decay heat removal capability e.g., residual heat remcval system, component cooling water system arrd service wata, system to removal heat and maintain cold shutdown.
(3) Suoport Support capability e.g., onsite power sources (AC & DC) or offsite after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and the associated electrical distribution system to supply the above equipment.
Equionnt necessary in addition to that already provided to maintain Nt standby.
- 6. BWR Ecuipment Generally Necessary For Hot Shutdown (1) Reactivity Control Reactor trip capability (scram).
(2) Reactor Coolant Makeuo Reactor coolant inventory makeup capability e.g., reactor core isolaticn cooling system (RCIC) or the high pressure coolant injection system (HPCI).
(3) Reactor Pressure Control and Decav Heat Removal Depressurization system valves or safety relief valves for dump to the suppression pool.
The residual heat removal system in steam condensing made, and service water system may also be used for heat removal to the ultimate heat sink.
(4) Socoression Pool Coolinc Residual heat removal system (in suppression pool cooling moce) service water system to maintain hot shutdown.
(5) Process Monitoring Process monitoring capability e.g., reactor vessel level and pressure and suporession pool temperature.
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. (6) Succort Support capability e.g., onsite power source (AC & DC) and their associated distribution systems to provide for the shutdown equipment.
- 7. BWR Ecuipment Generally hecessary 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 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and their associated distribution systems to provide for shutdown equipment.
Equipment 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 provide the shutdown 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 02t of the area that required the alternate system.
(c) Verification that changes to safety systems will not degrade safety systems.
(e.g., new isolation 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 switenes 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 isolation switches should be keylocked, or alarred in the control roan if in tne " local" or " isolated" cosition; periodic checks should be made to verify switch is in the procer position for normal oceration; and a single transfer switch or other new device should not be a source for a single failure to cause loss of redundant safet/ systems).
(d) Verification that wiring, including pcwer sources for the control circuit and equipment operation for the alternate shutdown method, is independent of equipment wirir.g in the area to be avoided.
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. (e) Verification that alternate shutdown power sources, including all breakers, have isolation devices on control circuits thit are routed through thJ area to be avoided, even if the breake r is to be operated manually.
(f) Verification that licensee procedure (s) have been developed which describe the tasks to be perfomed to effect the shutdown me thod. A sum.ary of toese 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 convenient to the existing fuses. The shutdown procedure should
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infom the operator to check these fuses.
(h) Verification that the manpower required to perform the shutdown runctions using the procedures of (f) as well as te provide fire brigade members to fight the fire is available as required by the fire brigade technical specifications.
(i) Verification that adequate acceptance tests are perfomed.
These should verify that: equipment operates from the local control station when the transfer or isolation switch is placed in the " local" nosition and that the equipment cannot be operated from the control room; and that equip-ment operates from the control room but cannot be operated at the local control station when the transfer or isolation swi tch is in the " remote" posi tion.
(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. Spec. surveillance require-ments on the service water system should add a statement similar to the following:
"Every third pump test should also verify tnat the pump starts from the alternate shutdown station after moving all service water system isolation switches to the local contrcl position."
(k) Verification that the systems available are aaquate to perform the necessary shutdown functions. The functions recuired shculd be based on previous analyses, if possible (e.g.,
in the FSAR), such as a loss of normal a.c. pwer or shutdcwn on a Group I isolation (BWR). The equipment required for ne alternate capability should be the same or equivalent to that relied on in the above analysis.
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7-(1) Verification that repair procedures for <;old shutdown systems are developed and material for mpairs is maintained on site.
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