ENS 43366
ENS Event | |
|---|---|
06:20 Mar 19, 2007 | |
| Title | Invalid Specified System Actuations During Testing |
| Event Description | This 60-day ENS report is being made per 10CFR 50.73(a)(2)(iv)(A) and 10CFR 50.73(a)(1) to report invalid automatic actuations of systems listed in paragraph (a)(2)(iv)(B), namely core spray (CS) and residual heat removal (RHR).
Unit 2 commenced refueling outage activities on Saturday March 10, 2007. Relay replacements for the 4 kv safeguard bus LOCA auxiliary control time delay relays were planned for all four buses due to a relay failure on Unit 1 that was identified during the prior refueling outage testing. On Monday March 19, 2007, at 02:20 hours, during emergency diesel generator (EDG) surveillance testing a Unit 2 Division 3 LOCA signal was inadvertently initiated during the planned replacement of the D23 bus LOCA auxiliary control relay (162-117). The relay was being replaced at a pre-determined step in the test. The relay was in an energized state when removed. When the new relay was installed an unplanned actuation of LOCA load shedding and sequential loading occurred. The relay was subsequently replaced and tested successfully. D23 EDG had been secured just prior to the event. The following loads were tripped and automatically restored: 2C CS pump and D234 load center breaker. The C emergency service water (ESW) pump tripped and did not restart since the EDG was not running. The 2C RHR pump continued to run. The 2A CS loop received a partial actuation in that the Division 3 signal was initiated but the Division 1 signal was not initiated. The 2C CS pump was operating in full flow test mode; therefore, it tripped and re-started as designed and 2A CS pump did not start which was expected. The 2A CS loop automatic valve alignment is initiated by the Division 1 signal; therefore, no automatic 2A CS loop valve alignment occurred. On Wednesday March 21, 2007 at 14:08 hours during EDG surveillance testing a Unit 2 Division 2 LOCA signal was initiated during the test which started the D22 EDG and tripped the D224 load center breaker as expected. However, the load center breaker did not re-close which was not expected and other expected actions did not occur. At 14:41 hours, 33 minutes later, the remaining LOCA actions occurred when 2B RHR pump, 2B CS pump, and 2B reactor enclosure recirculation system (RERS) fan automatically started, and D224 load center breaker automatically closed due to a late actuation of the D22 bus LOCA auxiliary control relay (162-116). At 15:48 an additional unexpected relay actuation caused the 2B CS pump and D224 load center breaker to trip. The relay had been replaced earlier in the day and the ongoing testing was intended to satisfy the post maintenance test (PMT). However, the relay did not actuate at the point in the test designated as the PMT; the relay actuated unexpectedly 33 minutes later. The cause of the first event was a less than adequate technical review of a test revision that added a step to replace the bus LOCA auxiliary control relay. The affected tests have been revised to replace the relay at a point in the test when it is de-energized. The cause of the second event was an equipment failure due to an intermittent connection between the relay pin connector and the relay base. The affected relay and base have been replaced and tested successfully. All of the systems that received start signals functioned successfully. The only equipment malfunction was associated with the degraded relay. The RHR and CS starts were partial actuations. The D22 EDG train start was an expected actuation. The C ESW train was tripped but was not automatically started. This event is reportable per 10CFR50.73(a)(2)(iv)(A) since 2B RHR pump, 2B CS pump, and 2C CS pump automatically actuated on an invalid signal. Component data: Equipment name: D22 Bus LOCA Aux Control Time Delay Relay Equipment number: 162-116 Manufacturer: A348 Amerace Corp Model number: ETR14D3A002 Serial number: 83330224 The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Limerick  Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1400.17 h58.34 days <br />8.334 weeks <br />1.918 months <br />) | |
| Opened: | Mark Arnosky 14:30 May 16, 2007 |
| NRC Officer: | Steve Sandin |
| Last Updated: | May 16, 2007 |
| 43366 - NRC Website | |
WEEKMONTHYEARENS 564642023-02-16T12:05:00016 February 2023 12:05:00
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