ML20064B396

Proposed Tech Specs Re Deenergization of Containment Emergency Sump Recirculation Valves

ML20064B396
Person / Time
Site:	Davis Besse
Issue date:	10/04/1990
From:	CENTERIOR ENERGY
To:
Shared Package
ML20064B395	List: ML20064B394 ML20064B396
References
NUDOCS 9010160307
Download: ML20064B396 (3)

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L1 Gens Number NPF-3 Page 1 FORINFORMATION DNI.Y .

3/4. 5 EMERGENCY CORE COOLING SYSTEMS (ECCS) i BASES 3/4. 5.1 CORE FLOODING TANXS f

The OPERABILITY of each core flooding tank ensures that a sufficient-  ;

volume of borated water will be imediately forced into the reactor vessel '

in the event the RCS pressure falls below the pressure of the tanks. l This initial surge of water into the vessel provides the initial cooling  ;

mechanism during large RCS pipe ruptures, f The limits on volume, boron concentration and pressure ensure that analysis are met. used for core flooding tank injection in the safety the assumptions The tank power o

" operating bypasses" perated isolation valves are considered to be 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 tank isolation valves fail to meet single failure criteria, removal of power to the valves is required.

i The limits for operation with a core flooding tank inoperable for any reason except an isolation valve closed minimizes the time exposure 4

of the plant to a LOCA event occurring concurrent with failure of an additional tures. If a tank which may result in unacceptable peak cladding tempera-closed isolation valve cannot be imediately opened, the full capability of one tank 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 with RCS average temperature > 280'F 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 l operating in conjunction with the core flooding tanks is capable of supplying . sufficient core cooling to maintain. the peak cladding tempera-tures within acceptable limits for all postulated break sizes ranging from the double ended break of the largest RCS cold leg pipe downward.

in the recirculation mode during the accident recovery 4e i 9010160307 901004 PDP l P ADOCK 05000346 PDC DAVIS-BESSE, UNIT 1 B 3/4 S-l' /cend .ent No. 2 0 l

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l Docket Norber 50-316

. Lic;nco,Nurber NPF-3 Serial Number 1817 1 Attachment 1 I Page 2 EMERGENCY CORE C00LINC SYSTEMS l

BASES Vith the RCS temperature belov 280'F, one OPERABLE ECCS subsystem is acceptable without single failure consideration on the basis of the j stable reactivity condition of the reactor and the limited core cooling <

requirements.

The Surveillance Requirements provided to ensure OPERABILITY of each component ensures, that, at a minimum, the assumptions used in the j safety analyses are met and that subsystem OPERABILITY is maintained. ,

The decay heat removal system leak rate surveillance requirements assure l that the leakage rates assumed for the system during the recirculation ,

phase of the low pressure injection vill not be exceeded. I 1

Surveillance requirements for throttle valve position stops and flov .

balanc e testing provide assurance that proper ECCS flows vill be main-tained in the event of a LOCA. Maintenance of proper flow resistance and pressure drop in the piping system to each injection point is necess ary to: (1) prevent total pump flow from exceeding runout condi: ions when the system is in its minimum resistance configuration, (2) trovide the proper flow split between injection points in accordance with the assumptions used in the ECCS-LOCA analyses, and (3) provide an acceptable level of total ECCS flow to all injection points equal to or A assumed in the ECCS-LOCA analyses.

6 3/4. .4 BORATED VATER STORAGE TANK The OPERABILITY of the borated water storage tank (BVST) as part of the ECCS ensures that a sufficient supply of borated water is available for injection by the ECCS in the event of a LOCA. The limits on BUST minimum volume and boron concentration ensure that 1) sufficient water is available within containment to permit recirculation cooling flow to the core, and 2) the reactor vill remain suberitical in the cold condition following mixing of the BVST and the.RCS vater volumes with all control rods inserted except for the most reactive control assembly.

These assumptions are consistent with the LOCA analyses.

The bottom 4 inches of the borated water storage tank are not available, and the instrumentation is calibrated to reflect the available volume.

The limits on vater volume, and boron concentration ensure a pH value of between 7.0 and 11.0 of the solution sprayed within the containment after a design basis accident. The pH band minimizes the evolution of iodine and minimizes the effect of chloride and caustic stress corrosion cracking on mechanical systems and components.

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DAVIS-BESSE, UNIT 1 B 3/4 5-2 Amendment No. 20,123 l

. Docket Number 50-346 ILic:nse Nu;ber NPF-3 i

. Serial Number 1817 Attachment 1 >

Page 3  ;

a Insert A  :

i Containment Emergency Su"q Tc'arculation Valves DH-9A and DH-9B are  !

de-energized during MODB.i L ;, 3 and 4 to preclude postulated inadvertent opening of the valves in sn event of a control Room fire, which could result

• in draining the Borated Vater Storage Tank to the Containment Emergency Sump  :

and the loss of this water source for normal plant shutdown. .Re-energisation- <

of DH-9A and DH-9B is permitted on an intermittent basis during MODES 1, 2, 3 and 4 under administrative controls. Station procedures identify-the .

precautions which must be taken when re-energizing these valves under such  ;

controls.

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