IR 05000282/1987011
| ML20236A941 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 07/08/1987 |
| From: | Defayette R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20236A927 | List: |
| References | |
| 50-282-87-11, NUDOCS 8707280278 | |
| Download: ML20236A941 (5) | |
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U.S. NUCLEAR REGULATORY COMMISSION j
REGION III
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Report No. 50-282/87011(DRP)
Docket No. 50-282 License No. DPR-42 Licensee:
Northern States Power Company 414 Nicollet Mall Minneapolis, MN 55401 Facility Name:
Prairie Island Nuclear Generating Plant
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Inspection At:
Prairie Island Site, Red Wing, Minnesota Inspection Conducted:
June 18 through July 2, 1987 Inspectors:
J. E. Hard
M. M. Moser i
Approved By:
R beFayette,-
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Reactor Projects Section 2B Dath '
Inspection Summary l
Inspection on June 18 through July 2, 1987 (Report No. 50-282/87011(DRP))
Areas Inspected:
Special safety inspection by resident inspectors of the conditions surrounding the failure of the No. 11 Safety Injection (SI) Pump to stsrt during testing on June 18, 1987 and of the investigative and corrective actions taken by the licensee.
Results:
One apparent violation, failure to maintain SI pump operability as required by Technical Specifications, was noted.
l 8707280278 870710 PDR ADDCK 05000282 G
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I DETAILS
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Persons Contacted j
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J L. Eliason, General Manager, Nuclear Plants
- E. Watzl, Plant Manager D. Mendele, General Superintendent ~, Engineering and Radiation Protection M. Sellman, General Superintendent,. Operations
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- A. Hunstad, Staff-Engineer J. Curtis, Production Engineer
- Denotes those present at the exit interview of July 1, 1987.
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Introduction and Summary l
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On June 18, 1987, during a monthly surveillance of the Unit 1 Safety Injection' System (SI), with the reactor at.94% power, the do. 11 SI Pump
failed to start when the start signal was initiated in the control room.
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Investigation determined that the SI pump' circuit breaker was not fully racked in and that this condition'may have existed since May' 22
(approximately 27 days).
Plant technical specifications require both SI l
pumps.to be operable with Reactor Coolant System (RCS( temperature greater than 200 degrees F and certain actions are required.if one SI pump is not operable during startup or power operation..These' technical specification requirements apparently were not met for the period May 24 through June 18, 1987.
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3.
Conditions Noted On June 18, 1987 At 8:23 a.m. on June 18, 1987, while Unit 1 was operating at 94% power
and Unit 2 was operating at 100% power, the monthly surveillance Procedure SP 1088 " Safety Injection Pumps Test" was being performed on the Unit 1 Safety Injection (SI) system.
This surveillance performs an i
operability test of both Unit 1 SI-pumps, each of which can deliver 100%-
capacity to their independent trains.
The last time that this surveillance had been performed was on May 11,~1987, near the end of the scheduled refueling outage.
During initial heatup at the conclusion of the outage, the licensee discovered that one of the steam generator (SG) tubes.which was supposed to have been plugged was inadvertently missed.
The reactor therefore was taken back to cold shutdown to make this repair.
As required by procedure during such delays, the'4160 volt circuit breakers for the SI pumps were racked out.
After the SG tube was plugged,:the breakers were racked back in on May 22 and reactor startup commenced.
The surveillance test on the SI pumps was not (and was not required to be) redone at'this
time. The reactor coolant system was heated above 200 degrees F on May 24, j
1987; startup' operations continued through May 28, 1987; and power operation was conducted until June 18.
When the No. 11 SI pump start signal was initiated at the control'
room console on June 18, as part of the surveillance test, the white
" disagreement" light illuminated and the pump did not start even though the indicator lights in the control room indicated the pump was j
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operational.
Per plant procedure, an operator was dispatched to verify that the 4160 volt breaker was racked in.
The operator observed that the ITE 4160 volt breaker indicating lights were normal and that the breaker appeared to be racked in but just to make sure, he inserted the crank in the racking screw and was able to rotate the handle about 1/2 turn when he heard the characteristic click of the mechanical latch on the racking screw. The Nu. 11 SI pump was then retested and operated successfully.
(The No. 12 pump had been successfully retested immediately upon discovery of the No. 11 pump failure.)
Investigation disclosed that conditions of the No. 11 SI pump being inoperable may have existed since the re-racking of the breaker on May 22, 1987, some 27 days before this surveillance.
The other pump,.
No.12, appears to have been operable during this entire period.
The cause of the failure appears to be a design deficiency that allows l
breaker position indicators (warning lights and. racking screw position)
to appear normal whereas in reality the primary disconnects (stabs) of l
the breaker were not engaged.
This same phenomenon was observed on a i
similar type breaker at Prcirie Island in 1982 and as a result, new
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racking tools were purchased to preclude such an event from recurring.
l This corrective action appeared to solve the problem since there were
l no recurrences of it in the intervening five years.
It now appears it
may not have completely solved the problem.
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4.
Technical Specification Requirements
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Technical Specification 3.3.A.1 states, in part, "1. A reactor shall not
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I be made or maintained critical nor shall it be heated or maintained above 200 degrees F unless the following conditions are satisfied except as-permitted in Specification 3.3.A.2....
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Two safety injection pumps are operable...."
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Technical Specification 3.3. A.2 states, in part, "2. During startup operation or power operation, any one of the following conditions of inoperability may exist for each unit provided startup operation is discontinued until operability is restored.
If during power operation operability is not restored within the time specified, the reactor shall be placed in the hot shutdown condition.
If the requirements of TS 3.3.A.1 are not satisfied within an additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, the l
reactor shall be placed in the cold shutdown condition....
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One safety injection pump may be out of service, provided the-pump is restored to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The other safety injection pump shall be tested to demonstrate operability prior to initiating repair of the inoperable pump."
l As noted above, the Unit I reactor coolant system was heated above 200 l
degrees F on May 24, 1987; startup operation proceeded to May 27; and power operation was conducted between May 27 and June 18.
The No. 11 SI pump was inoperable for this entire period; therefore, the Technical Specification requirements listed above were violated.
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Other Observations Other observations made by.the resident inspectors are as'follows:
a.
The-inoperability.of the SI pump was identified'by'the licensee.
b.
The NRC Senior Resident Inspector was notified of.the problem by the licensee within'a few minutes of its identification.
c.
-A licensee event report is being prepared and will be submitted-in accordance with 10 CFR 50.73.
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d.
-Visual verification that a breaker of this type is correctly racked in'is difficult.. The indicating lights were normal and visual observance of the breaker racking screw would lead one to believe the breaker was racked in.
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e.
The No. 12 pump was always operable.
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Status of Licensee Investigation as of July 2, 1987 a.
The plant Operations Committee had met several-times to discuss j
the event.and corrective actions, j
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An Investigator had been assigned from the plant staff to obtain j
all details of the event, c.
All operators who may have been involved in the racking of the a
breaker had been interviewed, d.
The' licensee concluded that although the operator involved is experienced and adequately trained, the highest probable cause of the event was the failure..to correctly rack in the breaker.
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All other safety-related breakers of this type were checked to assure they were operational.
Of those checked all but two had been operated successfully since they were last racked in.
Those two were visually examined and racking screws physically checked
to assure that the breakers were fully and properly engaged.
f.
The licensee had obtained a. training breaker of this type and will re-train all operators in its operation.
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g.
Appropriate modifications to plant procedures were being made to assure that safety equipment vill be test operated following breaker operations of the type which resulted in this event, h.
A mechanical inspection of the subject breaker was being performed.
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Independent. verification procedures for 4160 volt breakers were l
to be updated to reflect the lessons learned from this event.
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7.
Exit Interview The Senior Resident Inspector met the licensee representatives denoted I
in Paragraph 1 at the conclusion of the inspection on July 1, 1987.
The inspector discussed the purpose and scope of the inspection and the findings.
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The inspector also discussed the likely information content of.the inspection report with regard to documents or processes reviewed by the inspector during the inspection.
The licensee did not identify.
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any document / processes as proprietary.
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