ML20205L263
| ML20205L263 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 04/05/1999 |
| From: | COMMONWEALTH EDISON CO. |
| To: | |
| Shared Package | |
| ML20205L251 | List: |
| References | |
| NUDOCS 9904140199 | |
| Download: ML20205L263 (2) | |
Text
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EMERGENCY CORE COOLING SYSTEM B 3/4.5 BASES With the HPCI system inoperable, adeounte core cooling is assured by the OPERABILITY of the redundant and diversified Automatic Depressurization System and both the CS system and LPCI j
4 subsystem. In addition, the Reactor Core isolation Coo!ing (RCIC) system, a system for which no credit is taken in the safety analysis, will automatically initiate on c reactor low water level condition. The HPCI out-of service period of 14 days is based on the demonstrated OPERABILITY of redundant and diversified low pressure core cooling systems and the RCIC system.
The surveillance requirements provide adequate assurance that the HPCI system will be OPER etTrCiation through a test loop during reactor operation, a com requires a reactor shutdown. The pump discharge piping is maintained full to prevent water hammer damage and to provide cooling at the earliest moment.
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Upon failure of the HPCI system to function properly after a small break loss-of-coolant, the Automatic Depressurization System (ADS) automatically causes all OPERABLE main steamline rel valves to open, depressurizing the reactor so that flow from the low pressure core cooling system can enter the core in time to limit fuel cladding temperature to less than 2200'F. ADS is conservatively required to be OPERABLE whenever ieactor vessel pressure exceeds 150 psig. This pressure is substantially below that for which the low pressure core coolihg systems can provide adequate core cooling for avents requiring ADS.
ADS automatically contrais the five main steamline relief valves although the safety analyses support a minimum of 4 OPERABLE valves. It is therefore appropriate to permit one valve to be out-of-service for up to 14 days without materially reducing system reliability. A manual actuation of each ADS valve is performed to verify that the valve and solenoid are functioning properly a that no blockage exists in the ADS discharge lines. This is demonstrated by the response of the turbine control or bypass valve or by a change in the measured steam flow or by any other method suitable to verify steam flow. Adequate reactor steam dome pressure must be available to perfo this test to avoid damaging the valve. Sufficient time is therefore allowed after the required pressure is achieved to perform this test once only. The pressure specified for this test is that pressure recommended by the valve manufacturer. Reactor startup is allowed prior to performing this test t,ecause valve OPERABILITY and the setpoints for overpressure protection are verifie ASME requirements, prior to valve installation. Thus, a footnote is included in this SR to indicate that 4.0.D does not apply.
To preserve single failure criteria, a minimum of two independent OPERABLE low-pressure ECCS i
subsystems / loops are required in OPERATIONAL MODE (s) 4 and 5 to ensure adequate vessel inventory makeup in the event of an inadvertent vessel draindown. Only a single LPCI pump is required per loop because of the large injection t apacity. All of the ECCS may be inoperable provided the reactor head is removed, the reactor cavity is flooded, the spent fuel gates are removed, and the water level is maintained within the limits required by the Refueling Operations specifications.
i OUAD CITIES - UNITS 1 & 2 B 3/4.5-2 Amendment Nos.
171 & 167 9904140199 990405 PDR ADOCK 05 24 P
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INSERT A:
Showd either the high pressure or low pressure flow test fail, Technical Specifications 3.5.A, Action 3 is applied.