ML20046B153
| ML20046B153 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 07/30/1993 |
| From: | Keaten R GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 5000-93-0052, 5000-93-52, C321-93-2208, GL-92-04, GL-92-4, NUDOCS 9308030181 | |
| Download: ML20046B153 (2) | |
Text
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J GPU Nuclear Corporation l
a i pan, e Je s y07054 201-316-7000 TELEX 136-482 1
Writers Direct Dial Number July 30, 1993 C321-93-2208 5000-93-0052
'i U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
Dear Sir:
Subject:
Oyster Creek Nuclear Generating Station i
Docket 50-219 Response to Generic letter 92-04 Generic Letter (GL) 92-04 dated August 19, 1992, requested licensees to determine the impact of potential level indication errors after a rapid depressurization event on how the plants are operated. GL 92-04 also requested licensees to take short term compensatory measures to mitigate the consequences of potential level indication errors after a rapid depressurization event and provide the staff with plans for long term corrective actions including any proposed hardware modifications. Short term corrective actions were addressed in GPUN letter dated September 29, 1992.
The purpose of this letter is to address long term corrective actions.
i Backaround i
On August 28, 1992, the BWR Owner's Group submitted to the NRC a Generic Report which identified that BWR's use hot reference leg level instrumentation, cold reference leg instrumentation, or a combination of both for safety system actuation.
By letter dated September 29, 1992, GPUN identified that concerns relative to noncondensible gases coming out of solution have no impact on OCNGS -
automatic safety. system response during licensing basis transients or accidents.
The lo and Lo-Lo reactor water level signals associated with the RPS and ECCS are sensed by the hot leg Yarway instrumentation, which are not susceptible to the noncondensible gas phenomenon due to their geometric configuration.
The OCNGS emergency operating procedures (E0Ps) direct the operator to flood the reactor whenever confidence is lost in the level indication.
In addition, the operator practice of verifying level indication prior to termination of injection for i
level control has been reinforced.
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I C321-93-2208 Page 2 j
4 By the letter dated June 14, 1993, GPUN summarized reactor vessel water level measurement capability at OCNGS and associated protective functions, and j
concluded that the concerns raised by NRC Bulletin 93-03, dated May 28, 1993,
" Resolution of Issues Related to Reactor Vessel Water Level Instrumentation in BWRs" did not apply to OCNGS. The draindown scenario during cooldown conditions addressed by NRCB 93-03 is precluded at OCNGS by the fact that drywell isolation i
valves for the shutdown cooling system and the reactor water cleanup system are j
actuated based on Lo-Lo RPV water level. As noted above, Lo-Lo water level is sensed by Yarways, which are not susceptible to the noncondensible gas, i
Lona Term Corrective Actions Although OCNGS does not rely upon cold reference leg instrumentation for safety l
system actuation, GPUN recognizes the importance of maintaining all instrumentation as accurate as possible, and of accounting for those situations which impact instrument accuracy.
j In order for errors due to entrainea noncondensible gases to occur, two conditions must be present: 1) a concentrating mechanism which occurs when gases are stripped from condensate returning to the reactor vessel by inlet steam to the chamber, and 2) reference leg leakage enabling concentrated noncondensible i
2 gases dissolved in the condensate to be drawn into the reference leg.
To preclude the possibility for this type of error at OCNGS, GPUN intends to modify 2
the steam line/ condensing chamber configuration so as to eliminate the counterflow of steam and condensate, thereby eliminating the concentrating mechanism.
GPUN intends to install this modification consistent with the l
Integrated Scheduling Plan.
At present, this plan calls for installing the modification during the 15R refueling outage, scheduled to begin in October 1994.
Should you have any questions, please contact Brenda DeMcchant, Licensing Engineer at 609-971-4642.
Very Truly Yours, l
1 i
l Robert W. Keaten Director, Technical Functions SMK/mev cc: Administrator, Region 1 4
NRC Oyster Creek Project Manager Sr. Resident Inspector i
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