ML20087J728

Submits Status of Mods to Improve Adequacy of Station Distribution Sys Voltages,Per Util & NRC 821029 Ser.All Mods Completed,W/Exception of Changes to Station Air Compresser Starting Circuit

ML20087J728
Person / Time
Site:	Prairie Island
Issue date:	03/16/1984
From:	Musolf D NORTHERN STATES POWER CO.
To:	Office of Nuclear Reactor Regulation
References
TAC-53312, TAC-53313, NUDOCS 8403230051
Download: ML20087J728 (2)

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Northem States Power Company 414 Ncollet Mau Mmneapoks. Minnesota 55401 Telephons 1612) 330-5500 Fbr:h 16, 1984 Director Office of Nuclear Reactor Regulation U S Nuclear Regulatory Commission Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Status of Modifications Planned to Improve Adequacy of Station Distribution System Voltages On July 17, 1981 Northern States Power Company submitted for NRC review an analysis of the adequacy of station electric distribution system voltages. This analysis and additional supporting correspondence was the s' abject of a Safety Evaluation issued by the NRC Staf f on October

." 9 , 1982. A number of modifications to improve the capacity and flexi-bility of the station distribution system were committed to by Northern States Power Company and accepted by the Staff in their Safety Evaluation.

The purpose of this letter is to provide, for the information of the Ctaf f, a report of the status of these modifications as requested during a recent telephone call between our technical staff, Mr Dominic DiIanni, NRC Licensing Project Manager, and Mr John Emani, NAC Fower Systems Branch.

All modifications described in our July 17, 1982 report and accepted by the NRC Staff in their October 29, 1982 Safety Evaluation Report have been completed with the exception of changes to the station air compresser starting circuit to prevent unloading valves timing out before the motor starter has picked up. The possibility of needing this change was discussed in our report. This change will be pursued and will be completed in 1984 The following information is provided relating to other work we have committed to complete:

New 2R Inetallation A ncw 2R transformer has been installed and is fully operrtional. A Safety Evaluation justifying less restrictive grid operating licits based cn the improved capacity and regulation provided by having two reserve transformers (one for each unit) was provided for the information of the NRC Staff with our letter dated December 8, 1983.

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NORTHERN STATEis POWER COM*ANY Dir3ctor of NRR, NRC

/ March 16, 1984 Page 2

?ew CT-1 Installation A new CT-1 transformer has been installed to improve the CT-11 cooling tower safeguards bus scurce. The auto transfer inhibit of CT-12 to CT-11 (described in our letter dated August 17, 1982) is no longer needed. The auto transfer feature has been restored.

The new CT-1 transformer provides improved regulation o'f the CT-11 source over that reported in our ' *y 17, 1981 report. A Safety Evaluation has been prepuced and approved to justify less restrictive operating limits for this source as a result of the new transformer. The revised analysis is available for NRC Staff. review.

161 KV Substation Voltage In discussions with Mr Emani, we were requested to confirm the voltage levels maintained on the 161 KV system. As noted in our earlier report, the 161 KV system is maintained at 168 j 2 KV at all times by the load tap changer en No. 10 transformer. This arrangement is shown on Figure 1 of our July 11, 1981 report and discussed in Section 3.2 of that report.

Please contact us if you have any questione related to the information we have provided.

Di ONe David Musolf Manager - Nuclear Supp t Services DMM/bd .

c: Regional Administrator - III NRR Project Manager, NRC Resident Inspector, NRC J F Streeter, Region III, NRC G Charnoff

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