ML20207L733
| ML20207L733 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 10/10/1988 |
| From: | Larson C NORTHERN STATES POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| IEB-88-004, IEB-88-4, NUDOCS 8810170420 | |
| Download: ML20207L733 (3) | |
Text
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Northem States Power Company 414 Niconet Va1 M,nneapobs. Minnesota 55401 1927 Te'ephone (612) 3345500 October 10, 1988 b7C Bulletin 88 04 131 rector of Nuclear Reactor Regulation U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISIAND NUCLEAR GENERATING PIANT Docket Nos. 50 282 License Nos. DPR 42 50 306 DPR.60 Supplemental Resoonse to NRC Pulletin 88-04 In our initial response to NRC Bulletin 88 04, "Potential Safety.Re-lated Pump Loss", we were unable to fully respond to all of the re.
quired bulletin actions because pump supplier evaluation of the ade.
quacy of the minimum flow bypass lines for safety related centrifugal pumps was still in progress. Those evaluations have been completed, and the following supplemental information is provided to complete our response to NRC Bulletin 88 04 Due to unanticipated delays in the corrpletion of the pump supplier evaluations, we vere unable to provide this supplemental information per the schedule specified in our ini.
tial response. This delay was discussed with the NRC Project Manager j
for Prairie Island in August 29. 1988.
Action 3 of Bulletin 88 04 requested that the adequacy of the minimum flow bypass lines for satety related centrifugal pumps be evaluated with respect to the potential for damage resulting from operation and testing of the pumps in the minimum flow mode.
In response, the Prai.
rie Island Section XI program and flow diagrams were reviewed to de.
termine which pumps were safety related and which of the safety re-larmd pumps had miniflow lines.
The adequacy of the piping configura.
tion to provide adequate miniflow was evaluated by the Plant Staff and the results of the evaluation were reviewed by the operations Corunit.
tee.
In addition, per the guidance in Bullet.1n 88 04, the manufactur-ers of the Prairie Island safety related puaps were contacted and requested to verify that the current miniflow rates are sufficient to ensure that there vill be no pump damege from low flow opcration based on the Prairie Island piping configuration, recirculation flow and puup maintenance history.
The results of these evaluations found that, aside from the exceptions noted below, the present minimum flow piping configutations and flo.i rates are adequate for the Prairie Island safety related pumps.
/d 8910170420 081010
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PDR ADOCK 050002A2 g
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PNV
Director of NRJt t
October 10, 1988 Northern States Pcmer Company Page 'e The first exception involves the safety injes ton pumps.
Because the new evaluation included hydraulic instability ai lov flow conditions, not previous addrsesed, the safety injection pump supplier increased his recommended mintflow rates from 47 gpa (supplied) to 72 gprs (in.
'1 termittent use) or 125 gpm (continuous use).
In response to the re.
suits of this evaluation, the orifices in the safety injection re.
circulation lines will be modified to provide a miniflow rate, either l
72 gpm or 125 gpm, which will provide the proper balance between the required safety injection flow rate and the time the pump is expected d
i to be on miniflow. These modifications will be completed during the j
next refueling outage, presently scheduled for January 1990 for Unit 1 and March 1989 for Unit 2.
The pump supplier concurs with the deci.
sion to delay the modification of the orifices to the next refueling outage based on the operational history of the Prairie Island safety
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injection pumps which have e::perienced no operational problems as a l
result of operating at a miniflow of 47 gpm.
The auxiliary feedwater pump supplier found the existing minimua ilov rate to be adequate to prevent catastrophic pump failure, but recom.
1 I
mended that operation at the minimum flow rate be limited to approxi.
mately 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> per month to minimize cumulative long tera damage and to assure a reasonable trouble free period of operation.
Since the discharge pressure of the auxiliary feedwater pumps exceeds the steam i
generator reitef setpoints, this 10 hour1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> limitation vould only apply to situations where the pumps are run with the motor operated dis-J charge valves closed.
Because the auxiliary feedwater pumps are not j
normally run with the discharge valves closed and if they are run in that mode it would only be for a limited period of time, no further j
action is required in response to the auxiliary feedwater pump sup.
pliers evaluation.
1 In accordance with the requirements of Action 5 of the subject Bulle.
tin, a written report describing the actions taken will be provided to the Commission within 30 days following the completion of the modifi.
cation of all the safety injection pump recirculation line flow ori.
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Pleasa contact us if you have any questions related to the information wehaveprov4q.
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C E 1.arsow d Vice President Nuclear Generation j
c: Regional Administrator. Region III, NRC NRR Project Manager, NRC 3
Senior Resident Inspector. NRC G Charnoff a
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UNITED STATES NUCLEAR REGUIATORY COMMISSION
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NORTHERN STATES POWEk COMPANY 4
PRAIRIE ISt>','D INCLEAR CENERATING P1 ANT DOCKET No. 50 282 i
50 306 i
RESPONSE TO NRC BULLETIN 88 04 I
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J Northern States Povet Company, a Minnesota corporation, with this letter is submitting information roquested by NRC Bulletin 83 04 i
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This letter contains no restricted or other defense information.
f NORTHERN STATES 10VEp OMPAN*.'
l By ADfh C E Larspn j
Vice Pre Qide d Nuclear Generation a
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On this /g day ofMm, M before me a nocary public in and for said County, personally appeared C E Larson, Vice President Nuclear i
Generattoa, and being first duly sworn acknowledgea that he is authorized to execute this document on behalf of Northern Stateu Power Company, that he knows the contents thereof, and that to the best es his knowledge, information, and belief the statements made in it ace true and that it is 3
not interposed for delay, a A1,$
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