ML20128N596

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Proposed TS Section 3.5.A, Core Spray & LPCI Sys Bases, Reflecting Latest LOCA Analysis Performed by GE
ML20128N596
Person / Time
Site: Pilgrim
Issue date: 02/11/1993
From:
BOSTON EDISON CO.
To:
Shared Package
ML20128N595 List:
References
NUDOCS 9302230309
Download: ML20128N596 (2)
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Text

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3'. 5. A Core Spray and LPCI System This specification assures that adequate emergency cooling capability is-available whenever irradiated fuel is in the reactor vessel.

Based on the loss of coolant analysis performed by General Electric in-accordance with Section 50.46 and Appendix K of 10CFR50, the Pilgrim i Emergency Core Cooling Systems are adequate to provice sufficient cooling to the core to dissipate the energy associated with the loss of coolant accident, to limit calculated fuel clad temperature to less than 2200 F, to limit calculated local metal water reaction to less than or equal-to 17%, and to limit calculated core wide metal water reaction to less than or equal to 1%.

The detai'ed bases is described in NEDC-31852P and summarized in Section 6.5 l of the PNPS FSAR. '

The analyses discussed in NEDC-31852P calculated a peak clad fuel temperature of less than 2200 F with a core spray pump flow of 3200 gallons per minute (gpm). A flow rate of 3300 qpm ensures adequate flow for events involving degraded voltage.

Core spray distribution has been shown, in full-scale tests of systems similar in design to that of Pilgrim, to exceed the minimum requirements by at least 25%. In addition, cooling effectiveness has been demonstrated at less than half the rated flow in simulated fuel assemblies with heater rods to duplicate the decay heat characteristics of irradiated fuel. The accident analysis takes credit for core spray flow into the core at vessel pressure below 205 psig. However, the analysis is conservative in that no credit is taken for spray cooling heat transfer in the hottest fuel bundle until the pressure at rated flow for the core spray (104 psig vessel pressure) is reached.

The LPCI system is designed to provide emergency cooling to the core by flooding in the event of a loss-of-coolant accident. This system functions in combination with the core spray system to prevent excessive fuel clad temperature. The LPCI system and the core spray system provide adequate cooling for break areas of approximately 0.2 square feet up to and including the double-ended recirculation-line break without assistance from the high ~,

pressure emergency core cooling systems. The analyses in NEDC-31852P calculated a peak clad fuel temperature of less than 2200 F with LPCI pump flows of 4550 gpm, 4033 gpm, and 3450 gpm for two, three, and four pump combir, +tions feeding into a single loop. A single pump flow rate of 4800 gpm ensures sufficient flow in meet or exceed the analyses' assumptions.

The analyses of LOCA for PNPS demonstrated the combination of LPCS/LPCI systems are sufficient to provide core cooling even with a single failure of either an active or passive safety-related component. The analyses determined there were four significant single failures that challenge the Emergency Core Coolant Systerre ' capability to prevent fuel damage during the postulated LOCA.

They are:

1) Battery f ailure - Loss of a single battery train could leave only one LPCS pump, two LPCI pumps, and ADS to mitigate the LOCA. This is the most limiting single failure for all but the largest postulated recirculation line breaks and for all postulated non-recirculation line breaks.

Amendment No. 75, 109, 131 135 113 9302230309 930211 i PDR ADOCK 03000293 I P PDR I

NA31.h:

i 3.5.A Core Spray and LPCI Systems (Cont'd)

2) LPCI Injection Valve Failure - Loss of the-injection vLlve selected

-by LPCI loop-Selection Logic for the pathway for all LPCI pumps' flow leaves two core spray. pumps, HPCI, and ADS for LOCA mitigation.

This becomes the limiting single failure for the largest postulated recirculation line breaks.

3) Loss of one emergency diesel generator - This leaves one LPCS pump, two LPCI pumps, and ADS fcr LOCA mitigation.
4) HPCI failure - This leaves all other ECCS resources available. It ic a significant failure primarily for small line breaks.

In all cases above, the remaining ECCS resources are sufficient to prevent PCT from exceeding 2200'F and other criteria pruvided in Sectian 50.46 and Appendix K of 10CFR50.

Each Core Spray system consists of one pump and associated piping and valves with all active components required to be operable. The LPCI system consists of four LPCI pumps and asscciated piping and valves with all active components required to be operable.

Should one Core Spray System become inoperable, the remaining Core Spray and the LPCI system are available should the need for core cooling arise. Based on . judgments of the reliability of the remaining systems (i.e., the Core Spray and LPCI), a seven-day repair period was obtained.

If the LPCI system is not available, at least 2 LPCI pumps must be available to fulfill the containment cooling function. Based on judgments of the reliability of the remaining Core Spray systems, a 7-day repair period was set.

The LPCI system is not considered inoperable when the RHR System is operating in the shutdown cooling mode.

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1 Amendment No. 135 114

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