ML20211H732
| ML20211H732 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 10/01/1997 |
| From: | Sorensen J NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20211H738 | List: |
| References | |
| RTR-NUREG-1431 NUDOCS 9710070110 | |
| Download: ML20211H732 (3) | |
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Northern States Power company 1717 Wakonado Dr, E.
Welch. MN $5009 Telephone 612 388-1121 i
October 1,1997 10 CFR Pcrt 50 Section 50 90 U S Nue: ear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT
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Docket Nos. 50 282 License Nos. DPR-42 50 306 DPR 60 Supplement to L Icense Amendment Request Dated November 8,1996 Resubmittal of Coo Ina Water System Technical Suecification Amendments The subject license amendment request proposed changes to the Prairie Island Technical Specifications relating to the cooling water system which: 1) allow physical modifications to the turbine building cooling water header isolation logic; 2) allove the plant to remain in Specification 3.3.D.2.a when a diesel driven cooling water pump becomes inoperable; and 3) conform Technical Specifications 5.1 and 5.4 to NUREG-1431. The physical modifications included in change 1) will improve plant safety and therefore NSP proposes to start these modifications during the Unit i outage scheduled to commence on October 18,1997:
1 This supplement requests the NRC Staff to issue a license amandment with the single purpose of allowing Prairie Island to implement the turbine building cooling water header isolation logic modifications. Attachment 1 presents current Technical Specification pages TS.4.5-3 (same markup as submitted November 6,1996) and TS.S.4-1 marked up to show the changes required to allow Prairio Island to make these modifications. Attachment 2 shows these pages after the proposed chang s are incorporated. This license amendment should allow 90 days for implementation to permit the Unit 2 modifications to be performed after the Unit 1 outage is completed.
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USNRC 10/1/97
,P ge;2 of 3 The original plant design isolated the turbine building cooling water header on an SI signal to assure that essential loads were supplied with cooling water during an accident. The header isolation logic was modified during the construction phase of the plant to address concerns with spurious SI signals. Currently the header isolates on high flow coincident with low header pressure.
In 1995 Prairie Island performed a self assessment Service Water System Operational Performance inspection (SWSOPI) and determined that plant safety would be improved by making the turbine building cooling water header isolation logic directly respnnsive to an SI signal. Current inputs 'o the isolation logic are not positive indicatort Sat an accident is in progress and essential loads require priority cooling water supply. Under the plant modification process, Prairie Island plans to remove the high flow signal to the Isolation valve logic and replace it with the Si signal. Earlier concerns with spurious SI signals are addressed by retaining the low pressure input. The low pressure setpoint will also be raised under this modification which will cause the isolation to occur sooner. These changes will assure that essential loads are supplied with cooling water during an accident. These changes will also increase the margin available in the cooling water system and subsequently reduce the two phase flow conditions at the containment fan coil units.
A practical implication of revising the turbine building cooling water header isolation logic is that the actuation circuitry can not be tested quarterly in accordance with Technical Specification Section 4.2 as currently required by TS.4.5.B.3.e. Due to the SI signal inputs into the logic, this circuitry can only be tested during unit outages, Thus proposed changes to page TS.4.5-3 have been provided to require testing of the actuat.: n circuitry during refueling outages. These changes do not fall under the guidance for increased surveillance interval instrument drift contained in Generic Letter 91-04 since the pressure switches wl!! continue to be calibrated in accordance with their current schedules.
A revised Safety Evaluation, Significant Hazards Determination and Environmental Assessment have not been submitted since these evaluations, as originally presented in the November 6,1996 submittal, continue to bound the proposed license amendment as supplemented. License amendments issued by the NRC subsequent to November 6,1996 do not have any impact on the subject license amendment.
NSP further requests that the NRC Staff issue at a later date the other license amendments proposed in the November 6,1996 cubmittal, that is, allow the plant to remain in Specification 3.3.D.2.a when a diesel driven cooling water pump becomes inoperable and conform Technical Specifications 5.1 and 5.4 to NUREG-1431.
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If you have any questions related to this License Amendment Request please contact Dale Vincent at 612 388-6758.
Joel P. Sorensen Plant Manager 1
Prairie Island Nuclear Generating Plant c:
Regional Administrator Ill, NRC NRR Project Manager, NRC Senior Resident inspector, NRC State of Minnesota Attn: Kris Sanda J E Silberg 4
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