ML20246F564
| ML20246F564 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 08/23/1989 |
| From: | Fitzpatrick E GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8908310055 | |
| Download: ML20246F564 (3) | |
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n GPU Nuclear Corporation NUC Mr One Upper Pond Road Parsippany, New Jersey 07054 201-316-7000 TELEX 136-482 Writer's Direct Dial Number August 23, 1989 U.
S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C.
20555 Gentlemen l'
Subjects Oyster Creek Nuclear Generating Station Docket No. 50-219 Teclinical Specification Change Request No. 164 Additional Information GPU Nuclear Corporation (GPUN) submitted Technical Specification Change Request (TSCR) No. 164 on March 31, 1988. This TSCR proposed revised specifications regarding recirculation loop operation. In subsequent telecon discussions with the NRC Staff, the Staff requested GPUN to provide additional information. The information is contained in the attachment to this letter.
Very truly yours, jf6 E. E. Fitzfdtrick Vice President & Director Oyster Creek EEF/crb TSCR#164 Attachment cc: Administrator Region I U.
S. Nuclear Regulatory Commission 475 Allendale Road King of Prubsia, PA 19406 NRC Resident Inspector Oyster Creek Nuclear Generating Station Forked River, NJ 08731 Mr. Alex Dromerick, Jr.
U.
S. Nuclear Regulatory Commission I
Mail Station P1-137 Washington, DC 20555 h0I i
8908210055 890823 PDR ADOCK 05000219 g
i P
FDC GPU Nuclear Corporation is a subsidiary of General Public Utilities Corporation j
pr ATTACHMENT Technical Specification Change Request No. 164 Additional Information TSCR No. 164 was submitted on March 31, 1988 and proposed revised specifications regarding recirculation loop operability in Section 3.3 of the Oyster Creek Technical Specifications. Additional information was requested by the NRC Staff in subsequent telecon discussions. The requested information is provided below.
NRC Recuest
- 1) Discuss the consequences of a spurious isolation of the single unisolated recirculation loop when in a hot shutdown condition.
GPUN Response It is very unlikely that all recirculation loops would remain isolated, while in a hot shutdown condition, for a period of time sufficient to significantly affect reactor water level. Proposed specification 3.3.F.4 would require at least one fully open recirculation loop while in hot shutdown.
If, as the NRC staff has postulated, a spurious isolation of the fifth recirculation loop occurs when the other four have already been isolated, the loop closure alarm would reflash and the operator would take immediate action to unisolate at least one loop. There would be no significant reactor water level perturbation during the several minutes the above scenario would take to happen.
If, as the NRC staff further postulates, a recirculation loop could not be unisolated for some reason, the resulting water level transient would depend upon decay heat generation, reactor coolant makeup capability and initial conditions.
As mentioned above, the recirculation loop closure alarm annunciated in the control room when the fourth recirculation loop is isolated. This alarm will reflash when the fifth loop isolates. The alarm alerts the operator to unisolate at least one loop.
In addition to the alarm, the operator has other indications, including recirculation loop valve position indication and individual loop flow indication, to ascertain or verify loop status.
If, as postulated, all recirculation loops remain isolated as a result of a spurious condition, tne operator will be directed by symptem-besed emergency operating procedures to utilize available coola.t nakecp sources i f core region water level 10 decreasing. When recirculation pumpa nrG not operating, fuel zone level instrumentation senses water level directly from the bottom of the core region and has an upper range of 180 inches top of active fuel (TAF), so that the operator enn note a decreasing trend fron the normal cperating reactor water level range. Alro, triple low level (4' 8" TAF), which is sensed from inside the core region, is annunciated in the control room. With all recirculation loops isolated, feedvater and condensate pumps can flood the reactor vessel annulus allowing coolant to spill back through the steam separators into the core region. The core spray and control rod drive systems can provide makeup directly to the core region.
In addition, the fire suppression water system can be manually aligned to provide makeup via core spray piping.
s/
s TSCR NO. 164:
ADDITIONAL INFORMATION PAGE 2 i
I The core' region makeup sources are supplemented by the-limited flow available through hydraulic communication with the annulus via any open recirculation loop discharge bypass valves and associated suction valves.
If.the shutdown cooling system is operable, forced. flow from the annulus;to core regions is possible when reactor pressure is less than 150 psig and coolant temperature is less than 350'F.
Whether a shutdown is performed normally or is a result lof.a scram with no concurrent or resultant recirculation pump trip, operating recirculation pumps.
are normally kept in operation'while remaining in a hot shutdown condition or while a cooldown'is in progress. This assures uniform recirculation pump cooldown and thus' minimizes pump seal temperature and stress cycles.
In addition,.if all' operating recirculation pumps trip during power operation, the operator is directed to. scram the reactor and verify that the loops associated with the tripped pumps remain unisolated.. Operation in the above manner tends to minimize the time the plant would be in a hot shutdown condition with only one recirculation loop unisolated.
In' conclusion, the preceding discussion indicates that a spurious isolation of all recirculation loops while in hot shutdown can be detected with mitigating measures available to the operator. We believe that such a spurious isolation-combined with the inability to unisolate at'least one recirculation loop is of extremely low probability and there is no basis to so postulate.
NRC Recuest
- 2) What. advantages are there in maintaining one rather than two recirculation loops fully open when plant conditions permit?
QEUN Resoonse Shutdown cooling system (SDC) effectiveness is improved with one rather than two loops open. Each open loop providos a path for SDC flow to recirculate from the lower planum backward through the loep to the annulus where SDC taken suction. This flow bypasses the core when the loop's recirculation pump is not l
operating.
Fewer open loops results in less SDC flow bypassing the core j
region. As a resule, lack of core decay heat removal leading to thermal stratification and inadvertent vessel precourizations or steaming are minimized. Of course + operating recirculation pumps would also preclude
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thermal stratification and the potential for steaming. However, operating recirculation pumps at low pressures for extended periods reduces pump seal life.
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