ML20214R409
| ML20214R409 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 05/29/1987 |
| From: | Larson C NORTHERN STATES POWER CO. |
| To: | Guldemond W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 8706080123 | |
| Download: ML20214R409 (4) | |
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Northern States Power Company 414 Nicollet Mall Minneapoks. Minnesota 55401 Telephone (612) 330-5500 May 29, 1987 1
W G Guldemond, Chief Projects Branch 2, Region III U S Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Response to Inspection Reports No. 50-282/87003 and 50-306/87003 In response to your letter of May 1, 1987, which transmitted Inspection Reports No. 282/87003 and 306/87003, the following information is offered.
Violation Technical Specification 3.6, Containment System, A.1 states,
" Containment system integrity as defined in Specification TS.1 shall not be violated except when ene of the following conditions exist:
(a) the reactor is in the cold shutdown condition with the reactor vessel head installed, (b) the reactor is in the refueling shutdown condition with the vessel head removed, or (c) the fuel inside containment has not been used for power operation."
In addition, Technical Specification 1.0, C.
states, in part,
" Containment system integrity exists when the containment vessel, shield building, and Auxiliary Building Special Ventilation Zone (ABSVZ) are closed and the following conditions are satisfied.
7.
At least one door in each shield building airlock is closed."
Contrary to the above, on March 3, 1987, both Unit 1 shield building maintenance airlock doors were found to be open with the reactor coolant temperature greater than 200 degrees F and none of the conditions of T.S.
3.6 above satisfied.
This is a Severity Level IV violation (Supplement 1).
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Northem States Power Company W G Guldemond May 29, 1987 Page 2
Response
Unit 1 had been heated above 200F just hours before the event.
Pre-heatup checklists require that the doors be closed and further that their closed status be independently verified.
The Unit 1 Shift Supervisor had asked a security person in the area (by telephone) to verify that the doors were closed.
The security person reported that they were closed, but in fact he had misunderstood and it was the containment airlock doors that he had reported closed; the shield building doors apparently remained open at this time.
Independent verification of the status of the doors was done by checking the control board annunciator panel for the
" door open" alarm.
No alarm was seen since the control room alarm for these doors was bypassed (as is done routinely at cold shutdown) ; this bypass condition is shown on another annunciator panel, but the operator did not see it.
The status of alarm switches for these doors and similar doors is not checked on any checklist.
Cause of the event was procedural.
The initial status check done by the Shift Supervisor and the independent verifica-tion done by the operator are both methods allowed by plant procedures.
The pre-heatup checklists were revised to require that the ventilation annunciator bypass switches are returned to normal.
While this action should prevent further occur-rences, additional corrective actions are being studied as
)
noted in the Licensee Event Report for this occurrence (50-282-87-003).
Full compliance has been achieved.
Test Procedures Your transmittal letter requested that we provide an explan-ation of why safeguards logic testing procedures were not changed more expeditiously following the two previous reac-tor trips that had occurred within one year during conduct of this testing.
L
Northem States Power Company May 29, 1987 Page 3
Response
Safeguards logic testing is a complex process.
As evidenced by several previous events, this testing has a high proba-bility of spurious actuation.
Thus, proposed changes to these test procedures receive very deliberate preparation and review.
The proposed changes were based on an entirely new approach to performing this test.
The new method required thorough review by those with technical responsibility to assure that all regulatory requirements were covered, that the logic was properly tested, that the susceptibility of the plant to spurious trips was actually reduced by the changes, and that the typing was precise.
Once this process was complete, deliberate user reviews were conducted.
These reviews re-sulted in many comments and suggestions that were considered in the final version.
Please contact us if you have any questions related to our response to there matters.
uh FCC C E Larson Vice President Nuclear eneration cc: Regional Administrator - III, NRC NRR Project Managrir, NRC Sr Resident Inspector, NRC G Charnoff l
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