NRC Generic Letter 80-77, Refueling Water Level

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GL80077

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555

August 15, 1980

ALL WESTINGHOUSE PRESSURIZED WATER REACTOR LICENSEES

Dear Sir:

Current Westinghouse Standard Technical Specification (STS) 3.9.10 require "As a minimum, 23 feet of water shall be maintained over the top of irradiated fuel assemblies stored within the reactor pressure vessel" during movement of fuel assemblies or control rods when a plant is in Mode 6. From the vessel seated position a fuel assembly may need to be lifted in excess of 23 feet in order to clear the vessel flange for movement to the fuel transfer system. Typically, there is an additional 12 to 18 inches of upward travel to insure that the fuel assembly is fully withdrawn into the manipulator crane outer mask. Consequently, part of the fuel assembly would be exposed if the depth of water over the assemblies in the core did no exceed 23 feet.

The Staff has recently revised Westinghouse Standard Technical Specifications 3.9.8.2. 3.9.10 and Bases 3/4 9.8 and 3/4 9.10 to require at least 23 feet of water over the top of the reactor pressure vessel flange during movement of fuel assemblies or control rods, copy enclosed. These changes assure that the minimum level of water over the fuel assemblies is approximately 33 feet - sufficient depth to prevent inadvertent exposure of a fuel assembly during transfer.

You are requested to review your Technical Specifications and procedures and to make whatever revisions are necessary to assure that exposure of fuel assemblies and control rods cannot occur during transfer while the plant is in Mode 6. Within 30 days of receipt of this letter, please advise us of the measures if any, required to achieve this assurance for the facility and the implementation schedule.

Sincerely,

Thomas M. Novak, Assistant Director for Operating Reactors Division of Licensing

Enclosure:

As Stated

cc: w/enclosure Service Lists

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REFUELING OPERATIONS

LOW WATER LEVEL

LIMITING CONDITION FOR OPERATION

3.9.8.2 Two independent Residual Heat Removal (RHR) loops shall be OPERABLE.*

APPLICABILITY: MODE 6 when the water level above the top of the reactor pressure vessel flange is less than 23 feet.

ACTION:

a. With less than the required RHR loops OPERABLE, immediately initiate corrective action to return the require RHR loops to OPERABLE status as soon as possible.

b. The provisions of Specification 3.0.3 are not applicable.

SURVEILLANCE REQUIREMENTS 4.9.8.2 The required Residual Heat Removal loops shall be determined OPERABLE per Specification 4.0.5.

• The normal or emergency power source may be inoperable for each RHR loop.

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REFUELING OPERATIONS

3/4.9.10 WATER LEVEL - REACTOR VESSEL

LIMITING CONDITION FOR OPERATION

3.9.10 At least 23 feet of water shall be maintained over the top of the reactor pressure vessel flange.

APPLICABILITY: During movement of fuel assemblies or control rods within the reactor pressure vessel while in MODE 6.

ACTION:

With the requirements of the above specification not satisfied, suspend all operations involving movement of fuel assemblies or control rods within the pressure vessel. The provisions of Specification 3.0.3 are not applicable.

SURVEILLANCE REQUIREMENTS 4.9.10 The water level shall be determined to be at least its minimum required depth within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> prior to the start of and at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter during movement of fuel assemblies or control rods.

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REFUELING OPERATIONS

BASES

MANIPULATOR CRANE (Continued)

and 3) the core internals and pressure vessel are protected from excessive lifting force in the event they are inadvertently engaged during lifting operations.

3/4.9.7 CRANE TRAVEL - SPENT FUEL STORAGE BUILDING

The restriction on movement of loads in excess of the nominal weight of a fuel and control rod assembly and associated handling tool over other fuel assemblies in the storage pool ensures that in the event this load is dropped 1) the activity release will be limited to that contained in a single fuel assembly, and 2) any possible distortion of fuel in the storage rocks will not result in a critical array. This assumption is consistent with the activity release assumed in the accident analyses.

3/4.9.8 RESIDUAL HEAT REMOVAL AND COOLANT CIRCULATION

The requirement that at least one residual heat removal (RHR) loop be in operation ensures that

(1) sufficient cooling capacity is available to remove decay heat and maintain the water in the reactor pressure vessel below 140<deg>F as required during the REFUELING MODE, and

(2) sufficient coolant circulation is maintained through the reactor core to minimize the effect of a boron dilution incident and prevent boron stratification.

The requirement to have two RHR loops OPERABLE when there is less than 23 feet of water above the reactor pressure vessel flange ensures that a single failure of the operating RHR loop will not result in a complete loss of residual heat removal capability. With the reactor vessel head removed and 23 feet of water above the reactor pressure vessel flange, a large heat sink is available for core cooling. Thus, in the event of a failure of the operating RHR loop, adequate time is provided to initiate emergency procedures to cool the core.

3/4.9.9 CONTAINMENT PURGE AND EXHAUST ISOLATION SYSTEM

The OPERABILITY of this system ensures that the containment vent and purge penetrations will be automatically isolated upon detection of high radiation levels within the containment. The OPERABILITY of this system is required to restrict the release of radioactive material from the containment atmosphere to the environment.

3/4.9.10 and 3/4.9.11 WATER LEVEL - REACTOR VESSEL MD STORAGE POOL

The restrictions on minimum water level ensure that sufficient water depth is available to rewove 99% of the assumed 10% iodine gap activity released from the rupture of an irradiated fuel assembly. The minimum water depth is consistent with the assumptions of the accident analysis.

W-STS 8 3/4 9-2 JUN 23 1980