ENS 55436
ENS Event | |
|---|---|
23:04 Aug 29, 2021 | |
| Title | Safety System Actuation |
| Event Description | At 1804 CDT on 8/29/2021, Waterford 3 Steam Electric Station (WF3) experienced a Loss of Off Site Power event due to Hurricane Ida (See EN #55435). This event caused an automatic actuation of Emergency Diesel Generators Trains A and B. Both Emergency Diesel Generators started as designed and both are currently operating normally supplying power to their respective Class 1E Safety Busses. This automatic actuation is reportable in accordance with 10 CFR 50.72(b)(3)(iv)(A). Prior to the loss of offsite power, WF3 was in progress of performing a plant cooldown in accordance with procedural guidance. As part of this cooldown and after entering Mode 4, all Safety Injection Tanks were isolated. As a result of losing offsite power, Reactor Coolant System Temperature increased above 350F which is above the temperature requirements for Mode 4. Safety Injection Tanks are required to be unisolated and OPERABLE in Mode 3. Therefore, with no Safety Injection Tanks OPERABLE, this constituted an event or condition that could have prevented the fulfillment of a safety function and the unit entered Technical Specification 3.0.3. The unit was in Technical Specification 3.0.3 for approximately 43 minutes from 1805 CDT until 1848 CDT when Mode 4 conditions were re-established. This event or condition that could have prevented the fulfillment of a Safety Function is reportable in accordance with 10 CFR 50.72(b)(3)(v)(D).
While continuing to perform the Reactor Coolant System Cooldown and prior to placing Shutdown Cooling Train in service, it became necessary to start one train of Emergency Feedwater. Emergency Feedwater Train A was manually started at 1847 CDT to feed the Steam Generators and was secured at 1947 CDT. Emergency Feedwater Train A started and operated normally during this period. This manual actuation is reportable in accordance with 10 CFR 50.72(b)(3)(iv)(A). The licensee notified the NRC Resident Inspector.
The purpose of this notification is to revise Event Notification Report (EN) 55436 to include a partial retraction. On August 29, 2021, Waterford Steam Electric Station, Unit 3 (WF3) experienced a loss of offsite power (LOOP) event due to Hurricane Ida. Prior to the LOOP, WF3 had shutdown to Mode 3 (Hot Standby) in anticipation of the LOOP and was performing a plant cooldown in accordance with procedural guidance. When Mode 4 (Hot Shutdown) was achieved, all Safety Injection Tanks (SITs) were isolated as part of the plant cooldown. After the LOOP, Reactor Coolant System (RCS) temperature increased and the Core Exit Thermocouples (CETs) indicated that RCS temperature had exceeded 350 degrees F. Based on the CETs, this was above the temperature requirements for Mode 4 and, as such, WF3 declared entry into Mode 3. The SITs are required to be unisolated and Operable in Mode 3. Since no SITs were Operable at that time, it was determined that this constituted an event or condition that could have prevented the fulfillment of a safety function and included this as part of the EN 55436 report in accordance with 10 CFR 50.72(b)(3)(v)(D). An engineering evaluation has subsequently been performed to validate whether the RCS temperature excursion following the LOOP actually reached 350 degrees F. As defined in WF3 Technical Specification (TS) Table 1.2, Operational Mode temperatures are a function of RCS average temperature (Tavg), not just the indicated temperature of the CETs. Based on the calculated Tavg using validated temperatures, it was concluded that 350 degrees F was not reached. Thus, WF3 remained in Mode 4 following the LOOP and there was no event or condition that could have prevented the fulfillment of a safety function that was reportable pursuant to 10 CFR 50.72(b)(3)(v)(D). The remainder of EN 55436 remains correct and unchanged. The licensee notified the NRC Resident Inspector. Notified R4DO (Pick) |
| Where | |
|---|---|
Waterford  Louisiana (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+2.77 h0.115 days <br />0.0165 weeks <br />0.00379 months <br />) | |
| Opened: | John Lewis 01:50 Aug 30, 2021 |
| NRC Officer: | Bethany Cecere |
| Last Updated: | Oct 25, 2021 |
| 55436 - NRC Website
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Unit 3 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Hot Shutdown (0 %) |
| After | Cold Shutdown (0 %) |