05000306/LER-2001-001
| Docket Number | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3062001001R00 - NRC Website | |
EVENT DESCRIPTION
On April 9, 2001, testing of the Unit 2 emergency diesel generatorl D6 was being performed. At 0845, surveillance procedure SP2307, "D6 Diesel Generator 6 Month Fast Start Test" was begun as part of the requirement to complete surveillance procedure SP2335, "D6 DG 18 Month 24 Hour Load Test". At 0930, at the normal step in SP2307, D6 was removed from service just prior to taking manual control.
Concurrently, Technical Specification 3.7.B was entered placing D6 in a 7-day Limiting Condition for Operation (LCO) action statement.
At 1045, the 24-hour load test was begun. At 1330, D6 was unloaded and stopped, and remained out of service until April 17, 2001. Technical Specification (TS) 3.7.B.1. LCO requires, in the event of the inoperability of one of the unit's two emergency diesel generators:
"One diesel generator may be inoperable for 7 days provided (a) the OPERABILITY of the other diesel generator is demonstrated* by performance of surveillance requirement 4.6.A.1.e within 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s**, (b) all engineered safety features equipment associated with the operable diesel generator is OPERABLE, (c) the two required paths from the grid to the unit 4 kV safeguards distribution system are OPERABLE and (d) the OPERABILITY of the two required paths from the grid shall be verified OPERABLE within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter.
Items (a), (b), and (c) were met as specified. For item (d), the OPERABILITY of the two required paths from the grid was verified prior to removal of D6 from service. at approximately 0855 on April 9, 2001, via SP2118, "Verifying Paths from the Grid to Unit 2 Busses," the designated method of meeting this TS requirement. SP2118 was repeated at 1505 on April 9, 2001. However, at 0130 on April 10, 2001, it was discovered that the eight hour limit for the next verification had been exceeded. Eleven minutes later, at 0141, SP2118 was completed satisfactorily and the eight hour limit was met thereafter until D6 was returned to service the night of April 17, 2001.
CAUSE OF THE EVENT
The event was evaluated by a root cause team which concluded that the root cause was an inadequate shift turnover. There were several performance error prevention barriers broken which allowed this event to occur:
1. Turnover logs were not utilized to inform the oncoming crew of the next time to perform SP2118.
2. Shift briefing did not cover LCO Action Statements that were in effect, as recommended by Operations Department work instruction SWI-O-2, "Shift Organization, Operation and Turnover," Paragraph 6.4.1.f.2.
3. A mechanical timer was set to alarm but NOT started by the day shift.
1 EIIS Component ID: DG 4. Procedures SP2307, "D6 Diesel Generator 6 Month Fast Start Test" and SP2335, "D6 DG 18 Month 24 Hour Load Test" had no sign-off to indicate that SP2118 has been performed every 8 hrs during the LCO.
5. The day shift operator with responsibility for performing SP2118 had the function of designated diesel operator. However, since the diesel testing had been completed for the time being, there was no oncoming operator to whom to provide a turnover, as no diesel generators were running at turnover time.
This event is unique in that it is the first time this surveillance has been missed where required by an LCO. However, several barriers were broken which could lead to similar events in the future if not corrected. Therefore, actions to prevent recurrence are warranted.
ANALYSIS OF THE EVENT
Since this event consisted of a condition prohibited by the plant's TS, it is reportable per 10CFR 50.73(a)(2)(i)(B). Per the reasons discussed below in the "Significance Determination," health and safety of the public was not affected.
Loss Of Safety Function and Other Performance Indicator Impact There was no loss of safety function because the other Unit 2 emergency diesel generator was available during this event. None of the other performance indicators will be affected by this event.
Significance Determination Review of the plant emergency response computer and control board annunciators has confirmed that the two required paths to the grid were operable during the entire time from 1505 on April 9, 2001 until 0141 on April 10, 2001. Therefore this event had no safety significance, since the function required to be verified was indeed available throughout the period.
CORRECTIVE ACTION
Prairie Island is making the following enhancements to prevent recurrence of this event or occurrence of similar events:
1. Remind operators of the importance of passing information to their reliefs via the turnover log.
(Action 20014133) 2. Create a time tracking form and revise SP1118/2118 to include a step to initiate the use of the new form to track performance of the verification of two paths from the grid. (Action 20014134) 3. Use consistent wording among surveillance procedures that address grid verification requirements and the use of the new form to track when SP1118/2118 are due. (Action 20014135) 4. Revise the turnover log for shift managers, shift supervisors, and control room operators to include space to log TS action requirements in effect. (Action 20014136) 5. Change the procedural time requirement for grid verification to every 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to provide some margin for the TS limit of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. (Action 20014138) 6. Revise the Operations Department instruction SWI 0-2 to specify the responsibilities of "non-duty" operators for informing the "duty" operator of activities to be performed. (Action 20014139) 7. Evaluate possible computer aided methods for alerting operators to requirements for time scheduled actions. (Action 20014141)
FAILED COMPONENT IDENTIFICATION
None.
PREVIOUS SIMILAR EVENTS
No licensee event reports have been made in the last six years for a missed (or late) LCO-required surveillance.