ENS 55972
ENS Event | |
|---|---|
04:05 May 2, 2022 | |
| Title | Invalid Specified System Actuation |
| Event Description | The following information was provided by the licensee via phone and email:
This non-emergency notification is being made pursuant to the provisions of 10 CFR 50.73(a)(1) to report the occurrence of an invalid automatic actuation satisfying the reporting criterion of 10 CFR 50.73(a)(2)(iv)(A), specifically for the actuation of one train of the Essential Service Water (ESW) system that occurred on May 1, 2022. On May 1, 2022, with the plant shut down and the core offloaded, control room personnel were performing a fast power transfer from Engineered Safety Feature (ESF) transformer XNB02 to ESF transformer XNB01. In anticipation of this activity, the `B' load shedder and emergency load sequencer (LSELS) had been removed from service. Also, at the time, a portion of the `A' ESW train was isolated to support performance of a local leak rate test (LLRT) of a containment isolation valve in the affected portion of `A' ESW train piping. Service Water was supplying cooling water flow to `A' train loads (in lieu of ESW cooling water). When the power transfer was performed, an unexpected automatic start of the `A' ESW pump, along with some associated, automatic valve repositioning, occurred. The actuation occurred due to inadvertent satisfaction of automatic start logic for the ESW pump. The logic is intended to detect loss of ESW flow when the opposite train LSELS isolates Service Water during an undervoltage condition on a safety bus. The flow transmitter involved in the actuation is situated in a portion of the ESW piping that was isolated for the LLRT. The low-flow signal from the transmitter was consequently not reflective of low cooling water flow to plant loads in light of the fact that cooling water flow was being supplied to plant loads and the transmitter was locally isolated. In regard to the ESW train actuation, therefore, although the undervoltage signal was considered a valid signal due to the voltage drop caused by the fast transfer activity, the low-flow signal from the noted transmitter was considered to be invalid. For this invalid actuation, it was concluded that the actuation was not part of a pre-planned sequence, that the affected system was not properly removed from service during the occurrence, and that the safety function had not already been performed relative to the occurrence. [The] NRC Resident Inspector has been notified and an email of this report has been sent to hoo.hoc@nrc.gov. |
| Where | |
|---|---|
Callaway  Missouri (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1426.27 h59.428 days <br />8.49 weeks <br />1.954 months <br />) | |
| Opened: | Greg Cizin 14:21 Jun 30, 2022 |
| NRC Officer: | Ossy Font |
| Last Updated: | Jun 30, 2022 |
| 55972 - NRC Website
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WEEKMONTHYEARENS 570912024-03-25T01:56:00025 March 2024 01:56:00
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