ML20118D198

Documents 921001 Discussion W/Nrc Re Util Conclusion That It Would Not Be Prudent to Proceed W/Surveillance Testing of Safeguards Bus 16 Undervoltage Restoration Scheme During Current Unit Maint Outage,Per 920803 Emergency Change to TS

ML20118D198
Person / Time
Site:	Prairie Island
Issue date:	10/05/1992
From:	Parker T NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9210090400
Download: ML20118D198 (3)

Text

__ _

Northem States Power Company 414 N;conet Mall Minneapolis, Minnesota $54011927 Telephone (612) 330-6500 October 5, 1992 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISl AND NUCLEAR GENERATING PLANT docket Nos. 50-282 1,1 cense Nos. DPR-42 50 306 DPR-60 Technical Sp.cification Requirements for Surveillance Testing of 4kV Saferunrds Bus Undervoltago Logic Circuitry We are writing this letter to document our discussion of October 1, 1992 with NRC staff regarding our conclusion that it would not be prudent to proceed with surveillance testing of safoguards bus 16 undervoltage restoration scheine during the current Unit 1 maintenance outage.

On July 27, 1992, we determined that Unit 1 safeguards bus 16 had exceeded the Technical Specification (TS) fr,terval for surveillance testing of a portion of its undervoltage logic circuitry. We also determined that Unit 2 would exceed its TS surveillance interval for safeguards bus 26 on August 5, 1992. We then requested a Temporary Waiver of Compliance from TS Surveillance Requirement 4.6.A.3.b.1 for Units 1 and 2. Our request included a discussion of the circumstances leading to the request, safety significance, and compensatory actions. A Waiver of Compliance was verbally granted by NRC staf f on July 27, 1992. By letter dated July 29, 1992, we provided written confirmation of the information provided during the verbal request for a temporary waiver.

By letter dated August 3, 1992, we requested an Emergency Change to the Technical Specifications to delay the performance of the incomplete portion of the surveillance testing on buses 16 and 26 until completion of the electrical system upgrade modifications of the station blackout project during the two unit outage scheduled to begin fn October 1992.

In our request for delay we stated that we would take the following compensatory actions on an interim basis:

1. The relays associated with the 4160V safeguards bus undervoltage restoration scheme will be visually inspected monthly.

2. If either Unit 1 or Unit 2 should be taken to the cold shutdown condition, t.he incomplete portions of the testing required by h0090400921005 p ADOCK 05000282 PDR gh c

h

]

- . .. . . - . - - ~. .-

-k

. ~ ,

44

+

USNRC

' October 5, 1992 Page 2 of 3 Specification 4.6.A.3.b.1 will be completed on the affected unit

, prior to returning that unit to rower operation.

^

• that, in cons!.deration of those compensatory actions, we had determined 4t the second commitment was appropriate on the basis thar 1) Technical dpecification 3 7 allows bus 16 to be out-of-service (wh{.chl1; necessary to t.crform the surveillance testing) while at cold shutdown and 2) prompt opletion of the TS surveillance requirement is desirable.

nit 1 Js presently at cold shutdown for repair of a steam generator tube.and.

eddy current inspection of other tubes in the same steam-generator. When it became apparent that ue would be shutting the unit down, cognizant engineers began preparations to perform the surveillance test on bus 16 in the exp. ed plant outage conditions 's part of :he outage planning, the Outage Pls +n g Committee was consulted 4termine the appre,-Iste conditions for the The committee ccncluded c it would br taking m inappropriate risk to ,

perform the test in any of the plant co:/i tio.. t;.nned for this short l maintenance outage. Having the refueling c+vi-* ,oded would provide an acceptab'e ,!,nt condition for the performance , thir test with the current underve ,

'- toration scheme.

'he Outage Planning Committee reached this conclusion on the basis that we should maintair. two methods of decay heat removcl when we are in the shutdown conditic;, When the unit is in cold shutdown without the refueling cavity flooded, the potentially available sources of decay heat removal are two operable residual heet removal (RHR) trains and two operable steam generators.

When bus 16 is removed from service, 112 RHR pump _is made inoperable. In addition, the Unit 1 a tor-driven auxiliary feedwater (AFW)' pump is made inoperabic, and since the turbine-driven AFW pump is-inoperable below 350 P, both steam generators are made. inoperable. There is tF3' option of utilizing the Unit 2 motor-driven AFW pump but this would involve making it-unavailable for Unit 2 and thereby. entering a Unit 2 Limiting Condition fat Operatioa Action Statement. Contingency plans to restore a decay heat removal path (e.g,, mid-test restoration of bus 16 and the associated RHR crain) were _

evaluated but reliance on any one of these as the primary backup wa. Judged inatpropriate.

A key factor in the decision is the short time interval remaining prior to the Unit 1 and 2 cutages - there:will be less than three weeks left prior to-the shutdown of both units. If there were significantly more time between the scartup oi Ur.it 1 (scheduled for October 7. 1992) and tae scheduled two-unit outage (October 24, 19921, performing _the test would provide aore benefit.

'The relation between the risk of performing the test in less than desirable

__cond i tions and the benefit associated with presently demonstrating the operability of all portions of the undervoltage restoration scheme shifts the decision toward delaying the testing as the time to r: next outage decreases.

We thetefore do n,t believe that it is prudent to pert t.- this test while the anit is in the-turrent cold shutdown conditions.

j

1 1

.=

Northern States Power Company _

USNRC.

' October 5, 1992 Page 3 of 3

.Please cor. tact us if you have any questions related to this letter. l '

i M b\v5Mb '

Mmnas M Parker p%n hanager ,

Nuclear Support Services c: Regional Administrator - Region III, NRG Senior Resident Inspector, NRC NRR Project Manager, NRC J E Silberg l

, J