ML13246A381

Email from G. Matharu, NRR to P. Sahay, NRR FW: Wolf Creek Ifr 2012-04 - TAC ME8004

ML13246A381
Person / Time
Site:	Wolf Creek
Issue date:	10/24/2012
From:	Matharu G Office of Nuclear Reactor Regulation
To:	Sahay P P Office of Nuclear Reactor Regulation
References
FOIA/PA-2013-0273, IFR 2012-04, TAC ME8004
Download: ML13246A381 (3)

Text

ICIAndersen, JamesFrom:Sent:To:Cc:Subject:Matharu, GurcharanWednesday, October 24, 2012 9:03 AMSahay, PremRobles, Jesse; Andersen, James; Mathew, RoyRE: Wolf Creek IFR 2012-04 -TAC ME8004Outside of ScopeSinghFrom: Matharu, GurcharanSent: Wednesday, October 24, 2012 8:50 AMTo: Sahay, PremCc: Robles, Jesse; Andersen, James; Mathew, RoySubject: FW: Wolf Creek IFR 2012-04 -TAC ME8004Prem,In the Wolf Creek event, root cause for LOOP was the transformer wiring and inadequate attention to detailduring the modification process.I44 Outside of ScopeSingh .eFrom: Robles, JesseSent: Friday, October 19, 2012 1:53 PMTo: Matharu, GurcharanSubject: FW: Wolf Creek IFR 2012-04 -TAC ME8004I also forgot to mention that the transformer issue resulted in a Yellow Finding:Apparent ViolationInitiating Events 01/13/2012 WC Yellow *SC WE N *HP: Y *PJR: NDocket/Status: 05000482 (0)Open: ML12227A919(PIM) Failure to provide adequate oversight of contractors during maintenance on the Startup TransformerThe team reviewed a self-revealing apparent violation of Technical Specification 5.4.l.a and Regulatory Guide1.33 for the failure to follow procedures. Specifically, the electrical penetration seal and wiring assemblyassociated with the HI /CT4 and H2/CT5 current transformers installed in the startup transformer (XMRO 1)were replaced without insulating two of the splices, as required by Work Order 11-240360-006, Revision 3.This affected safety-related equipment on January 13, 2012, when the startup transformer experienced aspurious trip and lockout during a plant trip because the two uninsulated wires touched and provided a falsehigh phase differential signal to the protective relaying circuit. The protective lockout caused a prolonged lossof offsite power to Train B equipment. The licensee's root cause analysis concluded that the StartupTransformer failure on January 13, 2012, was caused by the failure to provide adequate oversight of contractors.As a result, the licensee failed to identify that electrical maintenance contractors had failed to install insulatingsleeves on wires that affected the differential current protection circuit. This issue was entered into thecorrective action program as Condition Report 47653. The licensee's corrective actions included reworking thecurrent transformer junction block to correct the missing insulation sleeves and updating station procedures torequire oversight of contractors performing work on risk significant components. This finding was more thanminor because it affected the human performance attribute of the Initiating Events Cornerstone and affected thecornerstone objective of limiting the likelihood of those events that upset plant stability and challenge criticalsafety functions. This deficiency resulted in the failure of the fast bus transfer and the failure to maintain offsitepower to safety-related loads during a reactor/turbine trip. The team performed the significance determinationusing NRC Inspection Manual Chapter 0609, Attachment 0609.04, "Phase 1 -Initial Screening andCharacterization of Findings," dated January 10, 2008, because it affected the Initiating Events Cornerstonewhile the plant was at power. The Phase 1 screened to a Phase 3 because the finding contributed to both thelikelihood of a reactor trip and the likelihood that mitigation equipment would not be available; it was alsopotentially risk significant due to seismic external initiating event core damage sequences. A Senior Reactor2 I ,kA nalyst performed a Phase 3 analysis using the Wolf Creek SPAR model, Revision 8.20. The performance'deficiency was determined to impact all transient sequences, particularly those involving losses of essential'service water and/or component cooling water that led to a reactor coolant pump seal loss of coolant accident.The loss of cooling water prevented successful room cooling for mitigation equipment as well as loss ofcontainment recirculation phase cooling. The analyst used half (98.5 days) of the period since the last successful* load transfer, since the actual time of failure could not be determined from the available information. Credit for* recovery of limited non-vital loads on the startup transformer was given based on licensee troubleshootingresults, however no recovery credit was available for room cooling, since the licensee had no preplannedalternate room cooling measures. The evaluation of external events showed a small contribution due to fires.* The increase in the core damage probability (ICCDP) was determined to be 2.59E-5. This was a YELLOWsignificance. The evaluation of large early release failures resulted in an ICLERP of 1.62E-7. This was aWHITE significance, which is superseded by the YELLOW significance of the ICCDP. This finding had a*human performance cross-cutting aspect associated with the work control component in that licensee personnelassociated with the oversight of the work did not appropriately coordinate work activities, and address the*impact of changes to the work scope consistent with nuclear safety H.3(b) (Section 40A5.2).From: Robles, JesseSent: Thursday, October 18, 2012 1:47 PMTo: Matharu, GurcharanSubject: Wolf Creek IFR 2012-04 -TAC MEB004Attached is the information for IFR 2012-04. You can see some examples of IFR evaluation memos here. Ifyou have any questions, please let me know. Thank you.Jesse E. RoblesU.S. Nuclear Regulatory CommissionReactor Systems EngineerNRR/DIRS/IOEB301-415-2940301-415-3061 (fax)Jesse. Robles.56irc.gyo3