ML19308C294
| ML19308C294 | |
| Person / Time | |
|---|---|
| Site: | 05000514, 05000515, Crane  |
| Issue date: | 09/24/1979 |
| From: | Hebdon F Office of Nuclear Reactor Regulation |
| To: | Deyoung B NRC - NRC THREE MILE ISLAND TASK FORCE |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001220665 | |
| Download: ML19308C294 (3) | |
Text
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/* f .4 BWST volume cf 575,000 gal, about 50 uin is available for the operator to make his decision to implement the HPI piggyback mode prior to Containment sump recirculation. Should the operator fail to cross-connect the HPI system and LPIS prior to Containment sump recirculation, he will have at least 30 min additional oefore HPI flow would terminate. (2) Realignment of ECCS Equipment for the Prevention of Boron Precipitation In Section 15.13.2.3(3), potential boron precipitation is briefly discussed and a reference is given for an analysis of this phenomenon. (3) Stabilized Transient ( For a.very_small_Ih TCwhgth,e, pressurizer le_ vel'isj g E5 [ rega_ined, the operator may desire to stabilize the transient prior to initiating an as near normal cooldown as possible under the transient situation. The following actions may be necessary: (a) Maintenance of Decay Heat Removal With[ decay.,KeiDiesoR via__thie's team" fen'e.rati _rj j l use of the modulating atmospheric dump valves is desirable. The atmospheric dump valves will normally open to hold the steam pressure at a l preset level. To reduce the steam pressure level, and thus increase the rate of heat removal, the operator will manually open the valve and monitor j steam pressure until he has obtained the desired heat removal rate. Since decay heat diminishes l/ gradually, c.ntrol of these valves is infrequent 15.13-27 Amendment 11 (April 1978) -- + 2
P and ticing not too critical. The operator would monitor the decay heat removal process by observing \\ the reactor coolant temperature. (b) Inventory Control The operator must control pressurizer level to , prevent filling of the pressurizer and thus increase 'the reactor coolant pressure. This is accomplished ,by controlling HPI flow. The operator would first take manual control over the HPI system by depressing the manual reset button on the,ESFAS control panel. The HPI valves can then be closed using the hand switch in the control room. The operator would slowly decrease HPI flow until a stable pressurizer i level is maintained. 13e operator may alterna-tively' elect to start and stop the HPI pump to maintain pressurizer level. = ( e No other actions would be required for long-term maintenance of a safe condition. Cooldown, upon restoration of offsite power, would then proceed in a simila. manner as shown in Figure 15.0-3. Use of the LPIS in the decay heat removal mode is desirable but not mandatory since continued operation of the ECCS in the sump recirculation mode ensures a safe condition. Actions to initiate the post-LOCA Gas Analyzer and Hydrogen Recombiner Sy~ stem would be the same as those ider.tified in Section 15.13.3.1. Figure 15.13-27 shows the operating sequence diagram for a small-break LOCA requiring the HPI piggyback mode of operation. 15.13.3.4 Core Flood Line Break The initial transient for this accident situation is described in Sections 6.3.1.1 and 6.3.1.4.2. The required operator actions are the same as those identified for the large-break LOCA discussed in Section 15.13.3.1. The time frame, however, for actions such as securing the HPI pumps would be extended, due to the somewhat slower rate of RCS depressurization for this break size. Amendment 11 15.13-28 (April 1978) __ _ _ _ _ _ _ _ _ _ _ _ _ _ _}}