ML20133L717
| ML20133L717 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 08/07/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20133L719 | List: |
| References | |
| NUDOCS 8508120709 | |
| Download: ML20133L717 (1) | |
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VYNpS 3.7.A (Cont'd)
In conjunction with the Mark I Containment Leng-Term program, a plant unique analys is was performed (see Vermont Yankee letter, dated April 27, 1984, transmitting Teledyne Engineering Services Company Reports, TR-5319-1, Revision 2, dated November 30, 1983 and TR-5319-2, Revision 0) which demonstrated that all stresses in the suppression chamber structure, including shell, external supports, vent system, inte;nal structures, and attached piping meet the structural acceptance criteria of NUREG-0661. The maintenance of a drywell-suppression chamber differential pressure of 1.7 psid and a suppression chamber water level corresponding to a downcomer submergence range of 4.29 to 4.54 ft.
will assure the integrity of the suppression chamber when subjected to post-LOCA suppression pool hydrodynamic fceces.
Using a 500F rise (Section 5.2.4 FSAR) in the suppression chamber water temperature and a minimum water volume of 3
68,000 f t, the 1700F temperature which is used for complete condensation would be approached only if the suppression pool temperature is 1200F prior to the DBA-LOCA.
Maintaining a pool temperature of 100 F will assure 0
that the 1700F limit is not approached.'
Experimental data indicate that excessive steam condensing loads can be avoided if the peak temperature of the suppression pool is maintained below 1600F during any period of relief valve operation with sonic conditions at the discharge exit. Specifications have been placed on the envelope of reactor operating conditions so that the reactor can be depressurized in a timely manner to avoid the regime of potentially high suppression chamber loadings.
In addition to the limits on temperature of the suppression chamber pool water, operating procedures define the action to be taken in the event a relief valve inadvertently opens or sticks open. This action would include:
(1) use of all availabic means to close the valve, (2) initiate suppression pool water cooling heat exchangers, (3) initiste reactor shutdown, and (4) if other relief valves are used to depressurize the reactor, their discharge shall be separated from that of-the stuck-open relief valve to assure mixing and uniformity of energy insertion to the pool.
Double isolation valves are provided on lines which penetrate the primary containment and open to the free space of the containment. Closure of one of the valven in each line would be sufficient to maintain the integrity of the pressure suppression system. Automatic initiation is required to minimize the potential leakage paths from the containment in the event of a loss-of-coolant accident. Details of the isolation valves are discussed in Section 5.2 of the FSAR.
Amendment No.
se, as, Ltr dtd 7/1/85 139 8508120709 850807 PDR ADOCK 05000271 p
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