Refueling Water Level (Generic Letter 80-77)
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D. C. 20555
August 15, 1980
ALL WESTINGHOUSE PRESSURIZED WATER REACTOR LICENSEES
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travel to insure that the fuel assembly is fully withdrawn into the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 22.214.171.124. 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
Thomas M. Novak, Assistant Director
for Operating Reactors
Division of Licensing
cc: w/enclosure Service Lists
LOW WATER LEVEL
LIMITING CONDITION FOR OPERATION
126.96.36.199 Two independent Residual Heat Removal (RHR) loops shall be
APPLICABILITY: MODE 6 when the water level above the top of the reactor
pressure vessel flange is less than 23 feet.
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.
188.8.131.52 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.
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.
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.
4.9.10 The water level shall be determined to be at least its minimum
required depth within 2 hours prior to the start of and at least once per 24
hours thereafter during movement of fuel assemblies or control rods.
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
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 140F 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
Page Last Reviewed/Updated Friday, May 22, 2015