ENS 52218
ENS Event | |
|---|---|
13:08 Sep 2, 2016 | |
| Title | Technical Specification Required Shutdown |
| Event Description | While operating in MODE 1 at 100 percent rated thermal power and placing Excess Letdown in service for Reactor Coolant System (RCS) leak detection, RCS operational leakage exceeded 1 gpm [gallon per minute] unidentified leakage as identified by performing RCS Water Inventory Balance using the Nuclear Plant Information System Computer. This required the entry into Technical Specification (TS) Limiting Condition of Operation (LCO) 3.4.13 Condition B at 0808 [CDT] on 9/2/16. The associated action is to place the unit into Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. Trending of containment sump level indicates the leakage is inside containment with the exact location within containment unknown. Containment inspection is being performed to try and identify the source of Reactor Coolant System leakage. NRC Resident Inspector has been notified. Re-alignment of the Letdown System back to its normal arrangement has subsequently reduced RCS leak rate to 0.521 gpm at 0652 CDT on 9/2/16.
Unusual or Not Understood - Leak Location is not known at this time. Maximum leak rate recorded was 1.358 gpm. The leak was first discovered at 08/31/16 at 1519 CDT. Safety Related Equipment not operational - Reactor Vessel Level Indicating System (TS 3.3.3).
Wolf Creek Nuclear Operating Corporation is retracting the 10 CFR 50.72(b)(2)(i) notification based on subsequent review of the event. The calculation of unidentified leak rate which triggered entry into the Mode 3 Required Action Statement was performed immediately after placing RCS Excess Letdown in service. An evaluation of the leak rate calculation determined that the leak rate was invalid due to performance of the RCS water inventory balance during non-steady state operating conditions. This was contrary to the requirements of TS Surveillance Requirement 3.4.13.1, as this test was performed while charging and letdown flows were being stabilized following the alignment of excess letdown. A walk down of the Excess Letdown system while in-service determined no leakage. Subsequent RCS water inventory balances performed with Excess Letdown in service under steady state operating conditions while in Mode 3 at normal operating pressure and temperature determined the maximum calculated unidentified leak rate was 0.675 gpm. After the plant entered Mode 3 a non-RCS pressure boundary leak was identified during equipment walk downs on a seal weld from the reactor vessel head core exit thermocouple nozzle assembly 77. The leakage did not impact the ability to shut down the unit. No TS limits were exceeded during this event. Therefore, the plant shutdown to investigate and correct leakage past the seal weld of a threaded connection does not meet the reporting requirements of 10 CFR 50.72. The NRC Resident Inspector has been notified. Notified the R4DO (Kramer). |
| Where | |
|---|---|
Wolf Creek  Kansas (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
| Time - Person (Reporting Time:+-1.65 h-0.0688 days <br />-0.00982 weeks <br />-0.00226 months <br />) | |
| Opened: | Larry Hauth 11:29 Sep 2, 2016 |
| NRC Officer: | Steven Vitto |
| Last Updated: | Oct 21, 2016 |
| 52218 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
WEEKMONTHYEARENS 572842024-08-23T13:00:00023 August 2024 13:00:00
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