ENS 51536

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v t e ENS Event
12:39 Nov 13, 2015
Title	Notification of Unusual Event Due to Unidentified Rcs Leakage Greater than 10 Gpm
Event Description	While in Mode 3, South Texas Project Unit 1 declared an Unusual Event at 0639 CST on 11/13/15, due to SU7 of EAL1- Unidentified RCS or Pressure Boundary leakage greater than 10 gpm. The excessive leakage to the WHT (waste holding tank) occurred when a letdown system demineralizer was placed in service. Operators bypassed the demineralizer and the RCS leakage was stopped. The excess leakage lasted for approximately 8 minutes and the maximum leakage was estimated to be 12-15 gpm. There was no impact on South Texas Unit 2 which continues to operate at 100% power. South Texas Project Unit 1 exited the Unusual Event at 0802 CST on 11/13/15, after verifying Unidentified RCS leakage less than 1 gpm. The demineralizer drain valve was partially open and was the cause of the excess leakage. The drain valve has been closed. The licensee has notified the NRC Resident Inspectors. Notified DHS SWO, FEMA Ops Center, FEMA NWC, NICC Watch Officer, and NuclearSSA via email * * UPDATE AT 1414 EST ON 11/13/2015 FROM JASON BERRIO TO MARK ABRAMOVITZ * * * Due to entering the STP [South Texas Project] Emergency Plan (Unusual Event), STP has officially determined to make a planned press release. Per 10 CFR 50.72(b)(2)(xi), STP is making a notification to the NRC via the emergency notification system (ENS). The NRC Resident Inspector has been notified of the press release. The planned press release shares the following information: On November 13, 2015, STP Nuclear Operating Station, Unit 1, declared an Unusual Event at 0639 CST. Plant operators identified increasing reactor coolant system leakage in Unit 1. Plant Operators took immediate actions to verify the source and safely isolate and stop the leakage. Upon identifying the source of the leakage, the Unusual Event was exited at 0802 CST on November 13, 2015. The leakage was captured and maintained within an on-site storage tank and there was no radioactive release to the environment. STP Unit 1 is preparing for restart following a scheduled refueling and maintenance outage. Notified the R4DO (Gaddy). * * RETRACTION AT 1221 EST ON 12/08/15 FROM MARC HILL TO JEFF HERRERA * * * The purpose of this report is to retract the ENS report made in accordance with 10 CFR 50.72 (a)(1)(i) on November 13, 2015, at 08:21 EST (ENS # 51536). STP Nuclear Operating Company declared an Unusual Event at 0639 CDT on November 13, 2015, based on Initiating Condition for Reactor Coolant System (RCS) Leakage Emergency Action Level (EAL) SU7. The event was reported to the NRC under EN # 51536 and the event was subsequently terminated on November 13, 2015 at 0802 CST. After further review, the emergency declaration is being retracted because the source of the leakage was from the Chemical and Volume Control System (CVCS) and not from the RCS. The NRC Resident Inspector will be notified. Notified the R4DO (Hagar).

ENS 51536 +/- *RETRACTED*
Where
South Texas Texas (NRC Region 4)
Reporting
Emergency class:	Unusual Event
10 CFR 50.72(a) (1) (i), Emergency Class Declaration 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release
Time - Person (Reporting Time:+-4.3 h-0.179 days <br />-0.0256 weeks <br />-0.00589 months <br />)
Opened:	Jeffrey Hestand 08:21 Nov 13, 2015
NRC Officer:	John Shoemaker
Last Updated:	Dec 8, 2015
51536 - NRC Website
v • d • e

v t e Emergency Notification System
South Texas with 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration
WEEKMONTHYEAR2023-03-30T06:03:00 [Table view]
[ENS list for South Texas]

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