ML20214U479
| ML20214U479 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/30/1987 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20214U449 | List: |
| References | |
| NUDOCS 8706110207 | |
| Download: ML20214U479 (2) | |
Text
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' Docket No'. 50' 245 -
B12468 l
4 I
Millstone Nuclear Power Station, Unit No.1
- Proposed Revision to Technical Specification Basis Section 3.5E, Isolation Condenser System.
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PDR ADOCK 05000245 P
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A 3.5 CORE AND CONTAINMENT COOLING SYSTEMS BASES The function of the Isolation Condenser during a small break accident is to assist the automatic pressure relief system in depressurizing the reactor as a backup to the FWCI system. The two effects of isolation condenser depressurization are:
(1) the minimization of reactor inventory loss which normally occurs during APR blowdown; this reduces the th e of core uncovery prior to reflooding; and (2) earlier onset of low pressure core spray cooling.
Analysis performed by General Electric in March 1976, in support of extended operation of Millstone whila the isolation condenser was being retubed indicated that from 40% rated power, over 30 minutes is available to initiate operator action to mitigate the consequences of a loss of all feedwater. This is based upon manual depressurization with APR and coolant supplied by all LPCI and core spray subsystems. The FWCI was assumed lost as part of the non-mechanistic assumption of loss of feedwater. The successful mitigation of this postulated event was no uncovering of the fuel.
F.
Emergency Cooling Availability The purpose of Specification F is to assure a minimum of core cooling equipment is available at all times.
If, for example, one core spray were out of service and the emergency power source which powered the opposite core spray were out of service, only two LPCI pumps would be available.
Likewise, if two LPCI pumps were out of service and two emergency service water pumps on the opposite side were also out of service, no containment cooling would be available.
It is during refueling outages that major maintenance is performed and during such time that low pressure core cooling systems may be out of service depending on the activities being performed. Specification F allows removal of one CRD mechanism or fuel removal and replacement while the torus is in a drained condition without compromising core cooling capability. The specification establishes the minimum operable low pressure core cooling system, water inventories, electrical power supplies and other additional requirements that must exist to allow such activities as CRD mechanism maintenance or fuel removal and replacement, to be performed in parallel with other major activities. The available core cooling capability for a potential draining of the reactor vessel while this work is performed is based on an estimated drain rate and the maintained minimum volume of water, 383,000 gallons, in the refueling cavity to be supplied to the reactor vessel. In addition, the available low pressure core cooling systems are lined up to the condensate storage tank which supplements the reactor cavity water with an additional 450,000 gallons of water. Thus, with the torus drained, a volume of approximtely 800,000 gallons of water will be maintained available to be supplied to the reactor vessel.
Millstone Unit 1 B 3/4 5-4