ML20094H578
| ML20094H578 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 02/23/1992 |
| From: | Eliason L NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9203110113 | |
| Download: ML20094H578 (3) | |
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i, Norttwm States Power Company 414 N(ollet Mall IAnneopclis, Minnen A !6401 1927 1cicphont. (61P) 330 58 00 February 23,1992 U.S. Nuclear Regulatory Commission Atto: Document Control Desk Warhington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 0PP-60 We have completed our initial investigations and determined the prirnori causes of the loss of decay heat removal and unplanned modo change occurrence dunng reduced inventory operation at Prairie Island Unit 2 on February 20,1992. We have discussed the causes with memberr of the NRC Augmerded Inspection Team (Aff). We have also discussed corrective actions necessary for release of tne hold on reactor coolant inventory with members of the AIT.
Initial teview of the event by plant management determined the apparent rvot causes. Error Reduction Task FuT9 review, though not yet complete, agrees with plant management conclusions. The primary root causes are:
1.
Difficulty in determining Reactor Coolant System (RCS) level due to nitrogen over pressure in the RCS.
- 2. Lack of a dedicated team leador during reduced inventory operations.
- 3. Lack of a senior experienced reduced inventory engineer available to Operations per sonriel for consultation, The magnitude of the heat up associated with the event was partially due to the time needed for transition from abnormal to emergency procedures. Early transition was not specifically required by existing procedures.
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Northern States Power Company USNRC Feburary 23,1992 Page 2 Cotrective actions taken foi draindown to install steam generator nozzio dams aio:
1.
Development of a new reduced inventory procedule which rec;uire.s:
- That iho RCS be fu'ly vented (depressurimd) during reduced inventory,
- That a dedicatud member of operation management be clearly designated as the team leadet during draindown with no other concurrent dutios.
- That a senior engineer experienced with reductd irmntory operations will be immediately available to Operati personnel during draindown opelationt,.
- 2. Abnorrnal and Eniorgency procedures have been revised to require impicmentation when RCS temperature exceeds 150'F.
- 3. An Eme>gency Plan implementing Proceduro has been revised to clearly Jefine the Emergency Action Leve! associated with reduced inventory events.
Additional access provisions and lighting have been installed to 4
aid the Operator taking local level readings.
New and revised procedures will bo reviewed and discussed with Operations personnel before use.
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Northern States Power Company USNRC Febut at y 23,1992 Pn00 3 in addition, other near term actions ata planned which will apply, in a broad perspective, lessons learned to other operating activities as, appr oprinte. Evaluation of long tcrni actions for reduced inventory operations are 10 progtess which will concider other hardware, p ocedure and hunmn f actors enhancements, t
Sincer ely, C,'Q...
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L R. [;liason [
[sv Vice President Nuclear Generation cc: Regional Adrninistrator - Region 111, NRC Cenior Resident inspector, NRC NRR Project Manager NRC J li Silberg
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