ML20080J142
| ML20080J142 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 01/16/1984 |
| From: | GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML20080J070 | List: |
| References | |
| TAC-48294, TAC-54495, TAC-98294, NUDOCS 8402140456 | |
| Download: ML20080J142 (6) | |
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HPCI/PCIC OPERABILITY LIMIT ECWIN I. HA7G NUCLEAR PGER PIRTT - UNIT 1 JANUARY 16, 1984 GENERAL ELECTRIC CO.
8402140456 840206 PDR ADOCK 05000321 P
pg I
INTRODUCTION The Technic 31 Specifications for the E.I. Hatch Nuclear Power Station Unit ) (Hatch 1) specify that the High Pressure Coolant Injection (HPCI)andReactorCoreIsolation(RCIC)systemsbeoperableabove 113 psig. This differs from the Hatch 2 Technical Specifications k
which require HPCI and RCIC to be operable above 150 psig.
Further-more, this is different from the system specifications for either system which require rated flow from 150 psig to 1120 psig reactor pressure (Hatch 1 FSAR Sections 4.7 and 6.3 and Hatch 2 FSAR Sections 5.5 and 6.3). There are no flow rate requirements for either HPCI or RCIC for reactor pressures in the range of 113 psig to 150 psig.
Therefore, a Technical Specifications change is requested to elimi-nate this inconsistency by changing the Hatch 1 Technical Specifica-tinns to be consistent with the Hatch 2 Technical Specifications and l
with the respective system design specifications. A safety eval-uation was performed to support this change. The safety evaluation addresses the need of HPCI and RCIC in the low pressure region for plant transient and loss-of-coolant accident (LOCA) events.
SAFETY EVALUATION This proposed Technical Specifications change does no't constitute a safety concern because this change does not affect the HPCI and RCIC system performance., Although both systems are capable of providing some flow at a reactor pressure below 150 psig, credit for the HPt.i or RCIC flow at the low reactor pressure region is never taken or needed.
In plant transient analyses, the challenges to the fuel integrity and reactor vessel integrity for the limiting events, such as Turbine Trip without Bypass and MSIV Closure with Flux Scram, occur within 10 seconds into the transient which is before HPCI or RCIC could initiate. Long term core cooling is provided by HPCI and/or RCIC at high reactor pressure. When reactor pressure drops below the maximum
1 operating pressure of the low pressure systems, approximately 265 psig-for core. spray and 220 psig for LPCI, the HPCI and RCIC functions are gradually replaced because the capacities of the core spray.and LPCI pumps are larger than that of the HPCI and RCIC pumps.
Th'e HPCI and RCIC are designed to provide some overlap in the operating pressure range down to 150 psig to assure a smooth transition from the high pressure systems to the low pressure systems.
If necessary, reactor depressurization can be achieved by operation of the Safety Relief Valves (SRVs) to assure operability of the low pressure systems. Therefore, this change does not affect the HPCI and RCIC performance in plant transient events documented in the Hatch 1 FSAR.
In the plant LOCA analyses, credit for the RCIC flow is never taken.
The HPCI is assumed to operate but its effectiveness is not fully re-alized.
Figure 6.3-1 of the FSAR for Hatch 1 (Figure 1) shows that the HPCI effectiveness is limited to small breaks. This is because a large break will depressurize the reactor below 113 psig before HPCI can effectively function (Figure 2). Even if HPCI does operate, the limiting break is a break in the downcomer region where the HPCI injects. This results in limited HPCI contribution to core cooling.
For small breaks where HPCI is most effective, the limiting single failure assumed in the LOCA analyses is the HPCI failure. Therefore, this change does not affect the calculated peak cladding temperature for a large or small break LOCA event.
In an actual LOCA or transient event, both HPCI and RCIC can be very valuable at high reactor pressure. However, once the reactor pres-sure drops below the maximum operating pressure of the core snrsy and LPCI pumps, the core cooling responsibility is shifted to these low pressure systems. Even if HPCI or RCIC operation is deemed desirable by the operator at low reactor pressure, the real additional benefit of an operating rpnge down to 113 psig as compared to 150 psig is negligible.
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There' fore, this proposed Technical Specifications change will not change the HPCI or RCIC system performance and will not constitute a safety concern.
11! will eliminate an existina vaguely defined
' requirement for the systen operability in the Hatch 1 Technical f
Specifications.
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FIGURE 2: TYPICAL REACTOR PRESSURE RESPONSE FOR LARGE BREAKS NEO 87 (REV S/31)
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