ML20153H534

Proposed Tech Specs 3/4.5.1 Re Safety Injection Accumulator Boron Concentration Verification

ML20153H534
Person / Time
Site:	North Anna
Issue date:	09/24/1998
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML20153H528	List: ML20153H522 ML20153H534
References
NUDOCS 9810020082
Download: ML20153H534 (5)

Text

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TECHNICAL SPECIFICATIONS BASES CHANGES NORTH ANNA UNITS 1 AND 2 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA UNITS 1 AND 2 9910020082 980924 PDR ADOCK 05000338 P Pm i

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a4J EMERGENCY CORE COOLING SYSTEMS BASES 3/4.5.1 ACCUMULATORS l Tile OPERABILITY of each RCS accumulator ensures that a sufficient volume of l borated water will be immediately forced into the reactor core through each of the cold legs in the cvent the RCS pressure falls below the pressure of the accumulators. This initial surge of water into l

l the core provides the initial cooling mechanism during large RCS pipe ruptures.

The limits on accumulator volume, boron concentration and pressure ensure that the l assumptions used for accumulator injection in the safety analysis are met.  ;

1 Although the run of piping between the two Safety Injection Accumulator (SIA) '

discharge check valves is credited in demonstrating compliance with Technical Specification 3.5.1 ,

minimum SIA volume requirement, the minimum boron concentration requirement does not apply to this run of piping. Applicable accident analyses have explicitly considered in-leakage from the RCS, and the resulting reduction in boron concentration in this run of piping, which is not sampled.

The accumulator power operated isolation valves are considered to be " operating bypasses"in the context of IEEE Std. 279-1971, which requires that bypasses of a protective function be removed automatically whenever permissive conditions are not met. In addition, as these accumulator isolation valves fail to meet single failure criteria, removal of power to the valves is required.

The limits for operation with an cccumulator inoperable for any reason except an  ;

isolation valve closed minimizes the time exposure of the pir.at to a LOCA event occurring concurrent with failure of an additional accumulator which may result in unacceptable peak cladding temperatures. If a closed isolation valve cannot be immediately opened, the full capability of one accumulator is not available and prompt action is required to place the reactor in a mode where this capability is not required.

3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS The OPERABILITY of two independent ECCS subsystems ensures that sufficient emergency core cooling capability will be available in the event of a LOCA assuming the loss of one subsystem through any single failure consideration. Either subsystem operating in conjunction with the accumulators is capable of supplying sufficient core cooling to limit the peak cladding temperatures within acceptable limits for all postulated break sizes ranging from the double ended break of the largest RCS cold leg pipe downward. In addition, er..:h ECCS subsystem provides long 1:rm core cooling capability in the recirculation mode during the accider.t recovery period.

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4 l 3/4.5 EMERGENCY CORE COOLING SYSTEMS l BASES 3/4.5.1 ACCUMULATORS The OPERABILITY of each RCS accumulator ensures that a sufficient volume of borated water will be immediately forced into the reactor core through each of the cold legs in the event the RCS pressure falls below the pressure of the accumulators. This initial surge of water into the core provides the initial cooling mechanism during large RCS pipe ruptures.

The limits on accumulator volume, boron concentration and pressure ensure that the assumptions used for accumulator injection in the safety analysis are met.

Although the run of piping between the two Safety Injection Accumulator (SIA) discharge check valves is credited in demonstrating compliance with Technical Specification 3.5.1 minimum SIA volume requirement, the minimum boron concentration requirement does not apply to this run of piping. Applicable accident analyses have explicitly considered in-leakage from the RCS, and the resulting reduction in boron concentration in this run of piping, which is not sampled.

The accumulator power operated isolation valves are considered to be " operating bypasses" l in the context of IEEE Std,279-1971, which requires that bypasses of a protective function be removed automatically whenever permissive conditions are not met. In addition, as these accumulator isolation valves fail to meet single failure criteria, removal of power to the valves is required.

The limits for operation with an accumulator inoperable for any reason except an isolation valve closed minimizes the time exposure of the plant to a LOCA event occurring concurrent with failure of an additional accumulator which may result in unacceptable peak cladding temperatures.

If a closed isolation valve cannot be immediately opened, the full capability of one accumulator is not available and prompt action is required to place the reactor in a mode where this capability is not required.

3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS The OPERABILITY of two independent ECCS subsystems ensures that sufficient emergency core cooling capability will be available in the event of a LOCA assuming the loss of one subsystem through any single failure consideration. Either subsystem operating in conjunction with the accumulators is capable of supplying sufficient core cooling to limit the peak cladding temperatures within acceptable limits for all postulated break sizes ranging from the double ended break of the largest RCS cold leg pipe downward. In addition, each ECCS subsystem provides long term core cooling capability in the recirculation mode during the accident recovery period. l 1

NORTH ANNA - UNIT 2 B 3/4 51  !