ML20046B861
| ML20046B861 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom, Limerick  |
| Issue date: | 07/30/1993 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-93-003, IEB-93-3, NUDOCS 9308060328 | |
| Download: ML20046B861 (5) | |
Text
FR5b.5 f PHILADELPHIA ELECTRIC COMPANY
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NUCLEAR GROUP HEADQUARTERS
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955-65 CHESTERBROOK BLVD.
WAYNE PA 19087-5691 (215) 640*KK)
July 30, 1993 STATION SUPPORT DEPARTMENT Docket Nos. 50-277 50-278 50-352 50-353 License Nos. DPR-44 DPR-56 NPF-39 i
NPF-85 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
Subject:
Peach Bottom Atomic Power Station, Units 2 and 3 Limerick Generating Station, Units 1 and 2 Response to NRC Bulletin No. 93-03, " Resolution of Issues Related to Reactor Vessel Water Level Instrumentation in BWRs" Gentlemen:
This letter provides Philadelphia Electric Company's (PEco's) response to NRC Bulletin (NRCB) No. 93-03, " Resolution of Issues Related to Reactor Vessel Water Level Instrumentation in BWRs," for Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3, and Limerick Generating Station (LGS), Units 1 and 2.
This letter is being submitted under affirmation _in accordance with 10CFR50.54(f), and the required affidavit is enclosed.
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NRCB No. 93-03 was issued on May 28, 1993, to notify Boiling Water Reactor (BWR) licensees about new information concerning level indication errors that may i
occur during plant depressurization. Specifically, this Bulletin identifies a concern that noncondensible gases may become dissolved in the reference legs of BWR reactor vessel water level instrumentation and lead to a false high level indication following a reactor vessel depressurization. The NRC requested that BWR licensees take various short _ term compensatory actions to ensure that potential level errors' caused by reference leg de-gassing will not result in improper system response or improper operator actions during transients and t
accident scenarios initiated from reduced pressure conditions. In addition, the NRC requested that BWR licensees implement level instrumentation system hardware modifications at the first cold shutdown after July 30, 1993, to ensure that the level. instrumentation system design is of high functional reliability for long-term operation.
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6 U.,S. Nuclear Regulatory Commission July 30, 1993 NRCB No. 93-03 Page 2 F
NRCB No. 93-03 also requested that by July 30, 1993, all BWR licensees provide a written response as specified in the " Reporting Requirements" of this Bulletin.
Each reporting requirement is restated below, followed by PEco's response for PBAPS, Units 2 and 3, and LGS, Units 1 and 2.
Reportino Reauirement 1 Addressees choosing not to take the requested short term actions must submit a report within 15 days of the date of this bulletin containing a description of the proposed alternative course of action, the schedule for completing it, and a justification for any deviations from the requested actions.
Resoonse Short term compensatory measures were taken at PBAPS and LGS ww..n 15 days of the date of this Bulletin in accordance with the " Requested Actions" described in NRCB No. 93-03.
Reportina Reouirement 2 By July 30, 1993, all addressees must submit a report providing:
(a) the description of the short term compensatory actions taken, and (b) a description of the hardware modifications to be implemented at the next cold shutdown after July 30, 1993. If an addressee chooses not to take the requested actions specified in the Hardware Modifications section, the report shall contain a description of the proposed alternative course of action, the schedule for completing it, and a justification for any deviations from the requested actions.
Resoonse to 2a Short term compensatory actions were taken at PBAPS and LGS in accordance with those actions described in this Bulletin.
These compensato y measures involved revising plant procedures at PBAPS and LGS to include additional provisions for monitoring reactor vessel water level during a plant shutdown and instructing Operations personnel on de-gassing and appropriate corrective action.
The procedure revisions specifically address the problem associated with de-gassing of the reactor vessel water level instrumentation system reference legs following vessel depressurization.
Plant procedures now indicate that reactor vessel water level may be erroneously high and could effect low-level automatic actuations at reactor pressures below 450 psig.
Therefore, the procedures now require that augmented reactor vessel water level monitoring commence when reactor pressure reaches 450 psig, and can be terminated when reactor water level is at a point to place shutdown cooling in operation at LGS, and when the reactor vessel is in a cold condition (i.e., <212 F) and vented at PBAPS. It is not conducive to discontinue reactor vessel water level monitoring i
activities at PBAPS when shutdown cooling is placed in service due to the design configuration of the reactor vessel water level instrumentation system.
To ensure accurate level indication during shutdown cooling operations at LGS, the l
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U.S. Nuclear Regulatory Commission July 30, 1993 NRCB No. 93-03 Page 3 reference leg for the " Shutdown / Upset" range of the reactor vessel water level instrumentation will be backfilled when reactor pressure reaches 150 psig. This evolution will not be performed at PBAPS due to the reactor vessel water level instrumentation system design differences between PBAPS and LGS. Additionally, plant procedures have been revised to direct shift management to review in-progress and planned work activities that have the potential of draining the reactor vessel during depressurization. Such activities would be evaluated and carefully controlled during a plant shutdown to prevent a reactor vessel water inventory loss during depressurization.
Licensed operators were informed of the potential for confusing and misleading reactor vessel water level indications due to de-gassing, and were instructed to take any necessary action (e.g., manual initiation of the High Pressure Coolant Injection (HPCI) system) based on an evaluation of all reactor vessel water level instrument indications.
Licensed Operator Requalification (LOR) training has been revised to include various scenarios regarding the effects of de-gassing on reactor vessel water level instrumentation and its impact. This training has commenced and will be completed by July 30, 1993, for r
all PBAPS licensed operators and a majority of the LGS licensed operators.
However, not all of the LGS licensed operators will be able to complete the required training by July 30, 1993, as requested in the Bulletin, due to shift rotation schedules.
The remaining LGS licensed operators will complete the i
required training by August 6, 1993.
Response to 2b t
PEco has been working towards a schedule to implement reactor vessel water level instrumentation system modifications at PBAPS, Units 2 and 3, and LGS, Units 1 and 2, during the next cold shutdown at each of the respective units after July 30, 1993.
PEco is aggressively pursuing the resolution of a number of technical issues associated with the modification.
In the event these technical issues are not resolved prior to the next cold shutdown at any of the PBAPS or LGS units after July 30, 1993, we will notify the NRC that installation of the modification will be deferred to a subsequent outage.
The modification to the reactor vessel water level instrumentation systems at PBAPS and LGS consists of installing a continuous " backfill" system on all four (4) reference legs of the reactor water level instrumentation system. The
" backfill" system will prevent the noncondensible gases from accumulating in the reference legs of the reactor vessel water level instrumentation system, thereby eliminating the potential for reference leg de-gassing during reactor vessel depressurization. This system will provide a continuous flow of water up through 7'
the reference legs to the existing condensing chambers, and then back to the reactor vessel via the current steam supply / condensate flow path which connects the condensing chambers to the reactor vessel.
The flow rate up through the reference legs will exceed the steam condensing rate in the condensing chambers; therefore, the reference legs will be continually flushed preventing the accumulation of noncondensible gases.
The source of water for the " backfill" system will be from the Control Rod Drive (CRD) system.
The CRD flow will be directed to a point on the instrument side of the reference legs' containment isolation excess flow check valve. The " backfill" system will be designed with flow control and indication capabilities, and will be provided with manual valves and vents to facilitate system startup, maintenance, and testing.
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U.S. Nuclear Regulatory Commission July 30, 1993 NRCB No. 93-03 Page 4 4
4 Reportina Reouirement 3 Within 30 days of completion of the requested hardware modifications, a i
report confirming completion and describing the modification implemented.
ReSD0nse A report confirming completion and describing the modifications will be provided within 30 days after the modifications have been installed at both PBAPS, Units 2 and 3, and following installation at both LGS, Units 1 and 2.
As requested in NRC Bulletin 93-03, PECo is providing information concerning the time and costs associated with responding to this Bulletin.
PECo estimates that 1600 man-hours, at a cost of $64,000, was expended performing the requested short term compensatory actions. Approximately 30 man-hours, at an estimated cost of $1200, was involved in preparing this initial response to 4
NRCB No. 93-03. The system hardware modifications at PBAPS and LGS are expected to cost approximately $2.0 million (i.e.,
$1.0 million per plant), with additional costs uf approximately $75,000 per year (i.e., $37,500 per plant) for maintenance related activities.
If you have any questions or require additional information, please do not hesitate to contact us.
Very truly yours, ett. c. iG for G. A. Hunger, r.
Director Licensing Section Enclosure cc:
T. T. Martin, Administrator, Region I, USNRC (w/ enclosure)
USNRC, Senior Resident Inspector, PBAPS (w/ enclosure)
N. S. Perry, Senior Resident inspector, LGS (w/ enclosure)
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COMMONWEALTH OF PENNSYLVANIA COUNTY OF CHESTER G. R. Rainey, being first duly sworn, deposes and says:
i That he is Vice President of Philadelphia Electric Company; that he has read the foregoing response to NRC Bulletin No. 93-03, " Resolution of Issues Related to Reactor Vessel Water Level Instrumentation in BWRs," for Peach Bottom Atomic Power Station, Units 2 and 3, and Limerick Generating Station, Units 1 and 2, and knows the contents thereof; and that the statements and matters set forth therein are true and correct to the best of his knowledge, information and belief.
r un At Vice President Subscribed and swor to before me thisef0 day of 1993.
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