Text

IR 05000482-10-008, on 06/21/10 - 11/24/10, Wolf Creek Generating Station, Special Inspection in Response to Component Cooling Water System Gas Accumulation
	ML110070347
Person / Time
Site:	Wolf Creek
Issue date:	01/07/2011
From:	Hay M C; Division of Reactor Safety IV
To:	Sunseri M W; Wolf Creek
References
	IR-10-008
Preceding documents:	ML110070347 (7 January 2011);
	Download: ML110070347 (41)
	v • d • e

January 7, 2011

Mr. M. W. Sunseri, President and Chief Executive Officer Wolf Creek Nuclear Operating Corporation P.O. Box 411 Burlington, KS 66839

SUBJECT: WOLF CREEK GENERATING STATION - NRC SPECIAL INSPECTION REPORT 05000482/2010008

Dear Mr. Sunseri:

On November 24, 2010, the U.S. Nuclear Regulatory Commission (NRC) completed a special inspection at your Wolf Creek Generating Station. The inspection examined activities associated with the discovery of gas accumulation in your component cooling water system on June 1, 2010 and residual heat removal system on July 1, 2010. The NRC's initial evaluation satisfied the criteria in the NRC Management Directive 8.3, "NRC Incident Investigation Program," for conducting a special inspection. The NRC's initial evaluation of this issue using the criteria in NRC Management Directive 8.3, "NRC Incident Investigation Program," determined that the estimated Incremental Conditional Core Damage Probability was in the overlap region between a special and an augmented inspection. However, it was determined that the model utilized likely over estimated the risk due to the failure assumptions. Therefore, based on management discretion, a decision was made that, although the risk for this event was in the overlap region, a special inspection would be performed since the risk for the issue was likely over estimated. The basis for initiating this inspection is further discussed in the inspection charter, which is Enclosure 2 to the report. The enclosed report documents the inspection results, which were discussed at the exit meeting on November 24, 2010, with Mr. S. Hedges, Site Vice President, and other members of your staff. The determination that the inspection would be conducted was made by the NRC on June 15, 2010, and the inspection started on June 21, 2010. The inspection examined activities conducted under your license as they relate to safety and compliance with the Commission's rules and regulations and with the conditions of your license. The inspection team reviewed selected procedures and records, observed activities, and interviewed personnel. This report documents three NRC-identified violations and one self-revealing violation of very low safety significance (Green). Although the safety significance of these issues were determined to be very low the causes for your delay in identifying, evaluating, and correcting the voided conditions is of concern. The inspection determined that your operators and engineering staff missed several opportunities to promptly identify and correct the voiding concerns. These included missed opportunities during review of operating experience, indications of abnormal flow oscillations, and abnormal flow control valve operation. In addition, when the voiding Wolf Creek Nuclear Operating Corporation - 2 - conditions were identified your evaluations failed to take into account all plant conditions affected by the degraded condition. All of these findings were determined to involve violations of NRC requirements. However, because of the very low safety significance and because they are entered into your corrective action program, the NRC is treating these findings as noncited violations, consistent with Section 2.3.2 of the NRC Enforcement Policy. If you contest any NCV, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington, D.C. 20555-0001, with copies to the Regional Administrator, Region IV; the Director, Office of Enforcement, United States Nuclear Regulatory Commission, Washington, D.C. 20555-0001; and the NRC Resident Inspector at Wolf Creek Generating Station. In addition, if you disagree with the crosscutting aspect assigned to any finding in this report, you should provide a response within 30 days of the date of this inspection report, with the basis for your disagreement, to the Regional Administrator, Region IV, and the NRC Resident Inspector at Wolf Creek Generating Station. The information you provide will be considered in accordance with Inspection Manual Chapter 0305.

In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter, its enclosure, and your response (if any) will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records (PARS) component of NRC's document system (ADAMS). ADAMS is accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).

Sincerely,/RA/ Michael Hay, Chief Technical Support Branch Division of Reactor Safety Docket No: 50-482 License No: NPF-42

Enclosure:

(1) Inspection Report 05000482/2010008 (2) Charter cc w/

Enclosure:

Site Vice President Wolf Creek Nuclear Operating Corporation P.O. Box 411 Burlington, KS 66839 Jay Silberg, Esq.

Pillsbury Winthrop Shaw Pittman LLP 2300 N Street, NW Washington, DC 20037 Wolf Creek Nuclear Operating Corporation - 3 - Supervisor Licensing Wolf Creek Nuclear Operating Corporation P.O. Box 411 Burlington, KS 66839 Chief Engineer Utilities Division Kansas Corporation Commission 1500 SW Arrowhead Road Topeka, KS 66604-4027 Office of the Governor State of Kansas Topeka, KS 66612-1590 Attorney General 120 S.W. 10th Avenue, 2nd Floor Topeka, KS 66612-1597 Chairman Coffey County Courthouse 110 South 6th Street Burlington, KS 66839 Chief, Radiation and Asbestos Control Section Bureau of Air and Radiation Kansas Department of Health and Environment 1000 SW Jackson, Suite 310 Topeka, KS 66612-1366 Chief, Technological Hazards Branch FEMA, Region VII 9221 Ward Parkway Suite 300 Kansas City, MO 64114-3372 Wolf Creek Nuclear Operating Corporation - 4 - Electronic distribution by RIV: Regional Administrator (Elmo.Collins@nrc.gov) Deputy Regional Administrator (Art.Howell@nrc.gov) DRP Director (Kriss.Kennedy@nrc.gov) DRP Deputy Director (Troy.Pruett@nrc.gov) DRS Director (Anton.Vegel@nrc.gov)

DRS Deputy Director (Vacant) Senior Resident Inspector (Chris.Long@nrc.gov) Resident Inspector (Charles.Peabody@nrc.gov) WC Administrative Assistant (Shirley.Allen@nrc.gov) Acting Branch Chief, DRP/B (Don.Allen@nrc.gov)

Senior Project Engineer, DRP/B (Rick.Deese@nrc.gov) Project Engineer, DRP/B (Greg.Tutak@nrc.gov) Project Engineer, DRP/B (Nestor.Makris@nrc.gov) Public Affairs Officer (Victor.Dricks@nrc.gov) Public Affairs Officer (Lara.Uselding@nrc.gov) Project Manager (Balwant.Singal@nrc.gov) Branch Chief, DRS/TSB (Michael.Hay@nrc.gov)

RITS Coordinator (Marisa.Herrera@nrc.gov) Regional Counsel (Karla.Fuller@nrc.gov) Congressional Affairs Officer (Jenny.Weil@nrc.gov) OEMail Resource ROPreports OEDO RIV Coordinator (Geoffrey.Miller@nrc.gov) DRS/TSB STA (Dale.Powers@nrc.gov)

File located: R:\_REACTORS\_WC\2010\WC2010008-RP-MRB.docx ML 110070347 SUNSI Rev Compl. Yes No ADAMS Yes No Reviewer Initials MCH Publicly Avail Yes No Sensitive Yes No Sens. Type Initials RE:DRS/TSB RI:DRS/EB1 SRI:DRP/B C:DRP/B MBloodgood MYoung DDumbacher DAllen /RA/ /RA/ per telecon /RA/ per telecon /RA/ RWD for DBA 01/04/11 01/04/11 01/04/11 01/5/11 C:DRS/TSB MCHay /RA/ 01/07/11 OFFICIAL RECORD COPY T= Telephone E= E-mail F = Fax

-1- Enclosure 1 U.S. NUCLEAR REGULATORY COMMISSION REGION IV Docket: 50-482 License: NPF-42 Report: 05000482/2010008 Licensee: Wolf Creek Operating Corporation Facility: Wolf Creek Generating Station Location: 1550 Oxen Lane SE Burlington, Kansas Dates: June 21 through November 24, 2010 Inspectors: M. Bloodgood, Reactor Engineer M. Young, Reactor Inspector D. Dumbacher, Senior Reactor Inspector Approved By: M. Hay, Chief, Technical Support Branch, Division of Reactor Safety

-2- Enclosure 1 SUMMARY OF FINDINGS IR 05000482/2010008; 06/21/10 - 11/24/2010; Wolf Creek Generating Station; Special Inspection in Response to Component Cooling Water System Gas Accumulation. This report covers a ten day period of onsite inspection, with in office review through a November 24, 2010. The special inspection team consisted of a reactor engineer, a reactor inspector and a senior resident inspector. The inspection identified four findings; all of the findings were NCVs. The significance of most findings is indicated by their color (Green, White, Yellow, or Red) using Inspection Manual Chapter 0609, "Significance Determination Process." The crosscutting aspect is determined using Inspection Manual Chapter 0310, "Components Within the Cross Cutting Areas." Findings for which the significance determination process does not apply may be Green or be assigned a severity level after NRC management review. The NRC's program for overseeing the safe operation of commercial nuclear power reactors is described in NUREG-1649, "Reactor Oversight Process," Revision 4, dated December 2006.

Evaluations and Operability Assessments The inspectors reviewed the licensee evaluations associated with the component cooling water and residual heat removal systems following the identification of the voiding condition. During the review of the licensee evaluations, the inspectors identified inadequate assumptions within the calculations and operability determinations. The assumptions included; the failure to include the effects of the voided condition in the residual heat removal system on the high head safety pumps; the use of nonconservative assumptions during the determination of the size of the initial void contained in the residual heat removal heat exchanger; and the initial troubleshooting following the start of the standby component cooling water pump during a low discharge pressure condition focused on the potential failure of the pressure switch, when the licensee had sufficient information that the pressure switch operated as expected.

In addition, during the inspection the inspectors observed challenges in the licensee's ability to understand abnormal operating conditions, in that, the licensee had multiple opportunities to identify the presence of voids in the residual heat removal and component cooling water systems prior to the actual discovery of the adverse conditions. These included missed opportunities during review of licensee and industry operating experience, indications of flow oscillations during start of system components, and abnormal cycling of flow control valves.

A. NRC-identified and Self-Revealing Findings Cornerstone: Mitigating Systems * Green. The inspectors identified a noncited violation of 10 CFR Part 50, Appendix B, Criterion XVI, "Corrective Action," for the failure to promptly identify voiding conditions in the component cooling water and residual heat removal system piping. The licensee failed to promptly identify the presence of voids in both the component cooling water and residual heat removal systems despite unexpected component cooling water pump auto starts and unexpected audible water hammer and minimum flow valve (EJ-FCV-610) cycling during component cooling water and residual heat removal pump surveillances. This finding was more than minor because the failure to promptly identify conditions adverse to quality associated with the component cooling water and

-3- Enclosure 1 residual heat removal systems is associated with the equipment performance attribute of the Mitigating Systems Cornerstone and affects the associated cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Using Manual Chapter 0609.04, "Phase 1 - Initial Screening and Characterization of Findings," the issue screened as having very low safety significance because it was a qualification deficiency confirmed not to result in a loss of operability. The finding had a crosscutting aspect in the human performance, decision making component, because the licensee failed to use conservative assumptions during the evaluation of the pressure oscillations exhibited during the component cooling water pump starts [H.1.(b)](Section 2.1).

Green. The inspectors identified a self-revealing noncited violation of Technical Specification 5.4.1, "Procedures," for failure to maintain procedures required for filling and venting of the component cooling water system. The licensee failed to ensure that the procedures for filling and venting the component cooling water system were adequately written to prevent gas accumulation and voids to form in the system. This finding was more than minor because the failure to maintain an adequate procedure for filling and venting the component cooling water system is associated with the equipment performance attribute of the Mitigating Systems Cornerstone and affects the associated cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Using Manual Chapter 0609.04,

"Phase 1 - Initial Screening and Characterization of Findings," the issue screened as having very low safety significance because it was a qualification deficiency confirmed not to result in a loss of operability. No crosscutting aspect was assigned, as this condition was not reflective of current licensee performance (Section 2.2).

Green. The inspectors identified a noncited violation of 10 CFR Part 50, Appendix B, Criterion V, "Instructions, Procedures, and Drawings," regarding the failure to follow the requirements of Procedures AP 28-001, "Operability Evaluations," and AP 26C-004, "Technical Specification Operability," associated with deficiencies resulting from the presence of voiding in the train A residual heat removal heat exchanger. This condition resulted in the failure to adequately address the impact of the voided condition for the high head pumps and the heat removal capacity of the heat exchanger. This finding is more than minor because it is associated with the Mitigating Systems Cornerstone attribute of equipment performance and adversely affects the objective to ensure equipment availability and reliability. Using Manual Chapter 0609.04, "Phase 1 - Initial Screening and Characterization of Findings," the issue screened as very low risk significant since the finding did not represent a loss of system safety function. The inspectors determined that this finding had a crosscutting aspect in the area of problem identification and resolution associated with the corrective action program component because the licensee failed to thoroughly evaluate a similar problem such that extent of condition of the voiding was considered and the cause was resolved P.1(c)(Section 2.3).

-4- Enclosure 1 Green. The inspectors identified a noncited violation of 10 CFR Part 50, Appendix B, Criterion XVI, "Corrective Action," for the failure to promptly identify and take corrective actions to address inadequacies in the residual heat removal system fill and vent procedure. The licensee failed to perform corrective actions to incorporate minimum flow rates required to sweep air out of the residual heat removal heat exchangers into the system fill and vent procedure during performance of revisions incorporating previous operating experience and corrective actions associated with NRC inspections. This finding is more than minor because it affected the Mitigating Systems Cornerstone attribute of design control for ensuring the availability, reliability, and capability of safety systems. Using Manual Chapter 0609.04, "Phase 1 - Initial Screening and Characterization of Findings," this finding was determined to be of very low safety significance because the voided heat exchanger was a design or qualification deficiency confirmed not to result in loss of operability. The inspectors determined that the finding has a crosscutting aspect in the area of problem identification and resolution associated with the corrective action component because the licensee staff evaluation of previous Performance Improvement Request 2002 2765 was not thorough enough to result in inclusion of minimum flows necessary to sweep voids out of the residual heat removal heat exchanger P.1(c)(Section 2.4). B. Licensee-Identified Violations None.

-5- Enclosure 1 Report Details 1.0 Special Inspection Scope The NRC conducted a special inspection at the Wolf Creek Generating Station to better understand the identification of a potential safety issue involving gas voiding in the component cooling water (CCW) and residual heat removal (RHR) systems. On June 1, 2010, the licensee identified voids in train A of the CCW system following an automatic start of CCW pump D during the performance of an inservice test of CCW pump A on May 24, 2010, due to low discharge pressure. On June 2, 2010, the licensee identified a 22.5 cubic foot void in train B on the CCW system side of the RHR heat exchanger. On July 1, 2010, the licensee identified a 9.8 cubic foot void in Train A of the RHR system located in the RHR heat exchanger u-tubes following the erratic operation of the mini flow valve EJ-FCV-610 and indications of water hammer.

The NRC's initial evaluation satisfied the criteria in the NRC Management Directive 8.3, "NRC Incident Investigation Program," for conducting a special inspection. The NRC's initial evaluation of this issue using the criteria in NRC Management Directive 8.3, "NRC Incident Investigation Program," determined that the estimated Incremental Conditional Core Damage Probability was in the overlap region between a special and an augmented inspection. However, it was determined that the model utilized likely overestimated the risk due to the failure assumptions. Therefore, based on management discretion, a decision was made that, although the risk for this event was in the overlap region, a special inspection would be performed since the risk for the issue was likely over estimated. The basis for initiating this inspection is further discussed in the inspection charter, which is Enclosure 2 to the report.

Background Gas accumulation or voiding of safety related fluid systems can cause air binding in pumps or water hammer events in piping systems. Instances of gas accumulation or voiding in safety related fluid systems have occurred on several instances in the nuclear industry, and as a result, the NRC published information notices, generic letters, and a NUREG related to this issue.

It is important that systems relied upon to mitigate accidents and events are able to perform their designed safety function. Specifically, a fluid system whose successful operation is dependent upon the proper operation of a pump to be able to supply water should be sufficiently filled to ensure that it can reliably perform its intended function under all accident and non-accident conditions as required.

Inadequate control of gas introduction or void formation in a fluid system can have the following safety implications: * The introduction of gases into a pump can cause the pump to become air bound that results in little to no flow being generated by the pump, rendering the pump inoperable. An air bound pump can become damaged quickly, thereby

-6- Enclosure 1 eliminating the possibility of recovering the pump during an event by venting the pump casing and suction piping. * Gas introduction into a pump can render a pump inoperable, even if the gas does not air bind the pump. This occurs when there is gas accumulation in the pump casing, which reduces the pump's discharge pressure and flow capacity to the point that the pump can no longer perform its design safety function. * Void formation in heat exchangers can result in decreased heat transfer capability resulting in the inability to remove heat during operation of the system. This occurs when insufficient flow is present in the system to remove air voids in the heat exchangers. * Void formation and gas accumulation can also result in a system pressure transient event known as water hammer. This is most commonly seen in the discharge piping, but can also occur in the suction piping. This phenomenon occurs when a pressure surge or wave is generated when a fluid in motion is forced to suddenly stop or change direction. Specifically, when there is a rapid venting or void collapse in a system, followed by a rapid refill of the piping with water, there is the potential to have water hammer due to the system configuration. 1.1 Event Summary On May 24, 2010, during a planned start of CCW pump A for inservice testing, operators at Wolf Creek observed a pressure drop and a CCW surge tank level drop of 68 gallons. During this system transient, standby pump C started as designed to address the low discharge pressure condition and maintain the system pressurized. Initially, the licensee attributed the starting of CCW pump C to a faulty pressure relay. On June 1, 2010, CCW system train A experienced an additional 65-gallon surge tank level drop following the start of pump C. The licensee subsequently determined gas pockets caused the level changes in the CCW system. Follow-up venting on June 1, 2010, uncovered the presence of an additional 0.4 cubic feet of gas. An extent of condition check of train B on June 2 uncovered the presence of a 22.4 cubic feet void in that piping. On June 2, 2010, ultrasonic testing of standby CCW train A identified several additional voids in unvented horizontal piping runs. The licensee declared the train inoperable and commenced dynamic venting operations to sweep the voids from the piping.

On June 28, 2010, during an inservice RHR system pump test, a licensee operator observed the cycling of minimum flow valve EJ-FCV-610 concurrent with indications of water hammer. During troubleshooting conducted on July 1, 2010, the licensee concluded that a 9.8 cubic foot void existed in the RHR heat exchanger u-tubes. Sequence of Events Date Discovery / Action October 10, 2002 Operating experience from Callaway noted that nitrogen gas from safety injection accumulators had migrated past leaking

-7- Enclosure 1 check valves and had come out of solution in the lower pressure RHR cold leg injection lines. This same phenomenon was documented in NRC Special Inspection Report 05000482/2008007 and in Wolf Creek Root Cause Report Incident Investigation Team 08-001 as occurring in the safety injection system. November 2002 Performance Improvement Request (PIR) 2002-2765 suggested an enhancement to the dynamic RHR fill and vent procedure. It resulted in changing the discharge path for the system fill and vent to the reactor vessel versus the refueling water storage tank suction header. The PIR also noted minimum flow rates to sweep air out of the RHR heat exchanger. Specifically, 3268 gpm of flow was listed as required for an effective heat exchanger fill and vent evolution. Although extensive procedure changes were made, the minimum flow requirement was not added to the procedure. March 13, 2008 NRC completed the special inspection associated with discovery of voids in the safety injection system on January 2, 2008. April 9, 2008 Wolf Creek Condition Report 00008212-03-31, recommended reviewing/revising the emergency core cooling system fill and vent procedures against isometric drawings. Despite the vertical RHR heat exchanger design requiring 3268 gpm of dynamic flow to sweep the RHR tubes, no minimum flow guidance was added to the new fill and vent procedures. November 5, 2009 Plant in Refueling Outage 17 November 2009 As part of fill and venting of the RHR system, air (0.001 cubic feet) was found and vented off at valve EJ-V-221 in RHR pump A common suction line. Following maintenance on the component cooling water system, both trains were filled and vented in accordance with Procedure SYS EG-400, Revision 17, "Component Cooling Water Fill and Vent." December 2009 Operators performed RHR train A pump quarterly inservice testing surveillance. During surveillance, the mini flow Valve EJ-FCV-610 cycled closed and then open due to system flow collapsing a void in the heat exchanger. The system engineer noted cycling of the valve but did not address the condition to operations. In addition, the operators missed the 16 second valve stroke and loud noise due to water hammer during the pump start. March 2010 Performed RHR train A pump quarterly surveillance. During surveillance, the mini flow valve EJ-FCV-610 cycled closed and then open due to system flow collapsing a void in the heat exchanger. The system engineer noted cycling of the valve. The operators missed the 16 second valve stroke and loud noise due to water hammer. May 24, 2010 During surveillance test using Procedure STS-EG-100A,

-8- Enclosure 1 "Component Cooling Water Pumps A/C Inservice Pump Test," the CCW pump C unexpectedly auto started. After the pump started, the pump vibration technician was leaning against the CCW discharge line and felt the line vibrate and then stop and then start vibrating again, indicative of a system flow anomaly. The operator expressed concern to control room about the piping vibration. The control room observed that the system was operating appropriately and continued with the test. Following the test the licensee declared the system operable. May 25, 2010 Operations personnel requested maintenance to troubleshoot the low-pressure switch on CCW train A due to a belief that the pump auto started because of a faulty switch. Operator reviewed past pump starts, identifying previous starts with low amps, discharge pressure, and discharge flow similar to indications to the pump start on May 24, 2010. The licensee started troubleshooting plans for the CCW pump discharge pressure switch even though the pump curves indicated that an actual low-pressure condition did exist during the pump start. May 26, 2010 Wolf Creek entered Technical Specification Extended Outage for maintenance of emergency diesel generator train A. The licensee performed a risk assessment of having the emergency diesel generator out of service and a failure of the CCW pump A. May 28, 2010 The troubleshooting plan for the CCW voiding issue was moved to June 1. June 1, 2010 The troubleshooting plan for CCW train A commenced. Licensee discovered void in EJ-V-0163, "RHR HX A, CCW Outlet Line Vent," and EJ-V-0205, "RHR HX A, Vent Outer Isolation Valve," located on the CCW side of the RHR heat exchanger. The licensee sampled the gas and determined that it was 97-99 percent nitrogen. Operators started the CCW train A pumps in reverse order to identify if the CCW pump A would exhibit the same low amperage, discharge pressure and flowrate as previously noted. The pump did in fact exhibit the same condition identified during the pump start on May 24, 2010. Operators considered CCW train A operable because the pump operated normally during steady state condition, however, the control room requested engineering support for a prompt operability determination. June 2, 2010 Operators vented the CCW side of both RHR heat exchangers and identified 0.45 cubic foot void in train A and 22.4 cubic foot void in train B. The 22.4 cubic foot void was quantified while venting the system using a rotometer. Engineering performed ultrasonic testing on both trains A and B and found both piping systems water solid. June 3, 2010 Engineering examined CCW system trains A and B suction points and the CCW side of the RHR heat exchangers and found the system water solid. However, ultrasonic testing performed

-9- Enclosure 1 on the train A discharge points identified a total void volume of 2.275 cubic feet. Operators declared CCW train A inoperable due to voids discovered and initiated Action Requests 25947 and 25948. As a corrective action the licensee wrote temporary procedures TMP 10-007, "Component Cooling Water Train A Dynamic Vent," and TMP 10-008, "Component Cooling Water Train B Dynamic Vent," to vent trains A and B to ensure that all voids in locations which could not be vented would be swept to locations which voids could be vented. June 4, 2010 Operators performed dynamic venting of CCW train A in accordance with TMP 10-007 three times. Following the venting engineering performed ultrasonic testing of CCW pump D discharge piping and discovered a void of 0.0007 cubic feet. Operators performed an Immediate Operability Determination and requested engineering to perform a Prompt Operability Determination in Action Request 25952. Engineering continued to monitor gas accumulation through periodic ultrasonic testing and venting of high point locations. June 5, 2010 Operators performed STS EG-100A, "Component Cooling Water Pumps A/C Inservice Pump Test," satisfactorily. Engineering completed operability evaluations EG-10-006, train A CCW system, and EG-10-007, train B CCW system. June 6, 2010 CCW train A was declared operable. Ultrasonic testing of CCW Train B found one void on the CCW Pump D discharge piping and at the RHR heat exchanger A discharge high point vent. The licensee declared train A CCW inoperable due to discovered voids. June 8, 2010 The licensee returned CCW train A to service with compensatory actions that consisted of periodic ultrasonic testing, monitoring, and venting. June 21-25, 2010 NRC special inspection team conducted onsite review of the CCW system voiding event. June 28, 2010 During RHR train A pump quarterly surveillance the minimum flow Valve EJ-FCV-610 unexpectedly cycled closed and then open due to pump flow collapsing a void in the heat exchanger. pump ran for 34 minutes. The licensee identified both the water hammer event and Valve EJ-FCV-610 closing. July 1, 2010 Troubleshooting Valve EJ-FCV-610 unexpected closure the licensee checked the calibration of the valve logic. Residual heat removal train A was declared inoperable and the system was vented at Valve EJ-FCV-610. July 2, 2010 Licensee identified voids were present in RHR train A. Found void at the containment recirculation sump isolation vent valve EJ-V-0059. July 4, 2010 Void at valve EJ-V-0059 identified as 133 inches long and

-10- Enclosure 1 1.2 Operating Experience The inspectors examined the licensee's program for reviewing industry operating experience, including reviewing the governing procedure and self-assessments.

Specifically, the inspectors reviewed incorporation of past industry operating experience pertaining to the component cooling water system voiding issue to assess whether the licensee had appropriately evaluated the notifications for relevance to the facility. The inspectors then examined the licensee's program and program procedures when screening and determining applicability of industry operating experience. The inspectors determined the Industry Operating Experience Program previously lacked rigor when evaluating industry operating experience and its applicability to the facility. Specifically, the licensee performed inadequate evaluations of system piping configurations, piping arrangements designed with inappropriate or no high-point vents, and procedural guidance which contribute to gas intrusion in safety related systems. Below are examples of missed opportunities to adequately review industry operating experience: 0.643 cubic feet. Determined that heat exchanger voids transporting to high point at valve EJ-V-0059. Ran pump four times for about 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />. During the pump runs, there was insufficient flow to sweep void out of heat exchanger. July 5, 2010 Licensee RHR pump A five times for about eight hours. Based on strip chart recorder and pump flow measurements engineering determined the RHR heat exchanger void to be 7.9 cubic. feet and declared the train operable per operating evaluation EJ-10-009. July 6, 2010 Voids discovered in the containment spray system during quarterly containment spray testing at high points. Suction void was enough to initially declare the train inoperable (0.9 cubic feet). The voids were vented off and the system was declared operable. July 12, 2010 Wolf Creek root cause team for CCW system voiding re-formed for the emergency core cooling system voiding issue. Root cause report for the CCW voiding delayed to allow inclusion of emergency core cooling system voiding causal analysis. July 19-22, 2010 NRC special inspection performed to follow up on RHR and containment spray voids. August 23, 2010 Licensee performed a vacuum fill of RHR train A system. Final void contained in the RHR heat exchanger is 4.1 cubic feet. September 2, 2010 Root cause report issued.

November 11, 2010 Licensee completed the engineering disposition for the past operability of the RHR heat exchanger with 9.8 cubic foot void and performed a dynamic venting of the RHR system to remove all remaining gas voids during plant shutdown.

-11- Enclosure 1 * The licensee determined that the evaluation of Condition Report CR-2008-00091 and the response to Generic Letter 2008-01 was inadequate and initiated Condition Report 14120 dated January 9, 2010. The licensee's actions focused primarily on essential service water supply to the auxiliary feedwater and essential service water emergency make-up to the CCW system because vent valves upstream of the auxiliary feedwater and CCW systems did not exist. Component cooling water was not formally evaluated for potential voiding locations. An action that resulted from Condition Report 14120 was enhancement of training to engineering, operations, and maintenance for safety systems susceptible to gas intrusion, but this was implemented differently for each organization.

Self-Assessment SEL 2009-139 did not identify a weakness in the evaluation of the industry operating experience related to gas voiding. The assessment provided seven recommendations, but no recommendations were applied to the CCW system. * Incident Investigation Team 08-001 focused primarily on emergency core cooling system and containment spray systems. The licensee stated in the root cause that the extent of condition for the Incident Investigation Team 08-001 was limited due to the initial problems being associated with the emergency core cooling system and there being no indication of problems in other systems. This was another missed opportunity for the licensee to address inadequacies related to the CCW system. * Three industry operating experience events that were related to CCW did not result in any action being taken by the licensee. The events were OE30299 (St. Lucie event dated October 16, 2008), OE30659 (St. Lucie event dated November 6, 2009), and a San Onofre event dated February 9, 2007. All three events involved the CCW system, but Wolf Creek determined none of the events to be applicable. Even though the events were not applicable, there was an opportunity for the licensee to identify that the CCW system was a safety system susceptible to gas voiding. Overall, corrective actions were developed to evaluate other safety and balance of plant systems to ensure the potential for gas voiding will not adversely affect the systems. The evaluations will utilize the recommendation of industry operating experience which includes a review of system isometrics, walkdowns of piping, and other system characteristics that could lead to gas accumulation. 1.3 Assessment of Licensee's Root Cause The inspectors reviewed and assessed the licensee's root cause analysis for technical accuracy, thoroughness, and corrective actions proposed and implemented. The inspectors reviewed the scope and process used by the licensee personnel to identify the root and contributing causes that led to the voiding conditions identified in the CCW and RHR systems. The inspectors compared information obtained during the conduct of the special inspection and

-12- Enclosure 1 review of the root cause analysis. The inspectors interviewed licensee personnel, reviewed licensee documents, logs and system design information. The licensee completed on September 2, 2010, a Level 2 root cause analysis as part of Condition Report 25918 that encompassed three separate conditions where plant voiding in safety systems was experienced. This evaluation was conducted to confirm the gas intrusion sources and to determine if there was a common cause for the three events. The three events included: * Component Cooling Water System: On May 24, 2010, during the start of CCW pump A the CCW pump D unexpectedly started on low discharge header pressure. Troubleshooting commenced on July 1, 2010, that identified multiple voids in the suction and discharge piping, and resulted in the CCW system train A being declared inoperable. On June 2, 2010, the licensee identified and vented a 22.1 cubic foot void on the CCW side of the RHR train B heat exchanger. * Residual Heat Removal System: On June 28, 2010, the licensee observed that the minimum flow valve automatically cycled open then closed upon start of the RHR pump A. On July 7, 2010, the licensee declared the RHR train A inoperable due to voiding concerns. The licensee determined that a 9.8 cubic foot void was present in RHR train B heat exchanger. * Containment Spray System: On July 6, 2010, the licensee identified during a routine ultrasonic testing surveillance a void in the containment spray Pump A suction line near the containment sump between the motor operated Valve ENHV01 and check Valve ENV002. Operators declared the containment spray system, train A, inoperable. The root/apparent cause identified that personnel had a lack of knowledge concerning gas voiding and accumulations within piping systems, specifically with the CCW, RHR, and containment spray systems. The root cause identified three examples of lack of understanding: (1) Misconception that the CCW system was self-venting, (2) Failure to identify that dynamic venting of the RHR system requires a minimum flow rate to completely sweep air voids out of non-vented locations, and (3) Lack of knowledge in the methods of gas void formation.

In addition, the licensee included as a contributing cause the failure of operations and engineering personnel to use conservative decision making when performing evaluations of current operating conditions. This was identified by the NRC as a failure to promptly identify conditions adverse to quality and further discussed in Section 2.1 of this report.

1.4 Operating Practices and Design that Allowed the Voiding Condition to Exist Operating Practices: The inspectors found the following performance deficiencies contributed to the voided conditions in piping systems:

-13- Enclosure 1 * Failure to promptly identify conditions adverse to quality following indications of RHR valve cycling and oscillations in CCW pump amperage, flow, and discharge pressure during pump starts * Failure to identify sections of the CCW and RHR systems that due to configuration required a dynamic vent * Failure to maintain an adequate procedure for filling and venting the CCW and RHR systems * Failure to incorporate changes in the RHR venting procedure to fully address recommendations in 2002 from the Incident Investigation Team RC-1 00008218 These performance deficiencies are provided in more detail in Sections 2.1, 2.2, 2.3 and 2.4 of this report. 1.5 Licensee's Corrective Action and Extent of Condition The inspectors evaluated the scope, adequacy, and timeliness of the licensee's corrective measures that were planned and implemented in response to the CCW and residual heat removal system voiding. The inspectors concluded that the actions both planned and implemented by the licensee were appropriate to address the identified issue, to prevent recurrence, and were consistent with the safety significance of the issue. These corrective actions included: * Increased monitoring of the RHR and CCW systems for voids using ultrasonic testing and venting * Revisions of the component cooling water fill and vent procedures to incorporate the use of dynamic venting in addition to improving the valve operating sequences * Revision of the residual heat removal systems fill and vent procedures to incorporate a minimum flow rate required during the dynamic flush of the system * Modifications to the component cooling water system piping which includes the redesign of the surge tank connection piping and the addition of high point vents * Perform training to increase operations and engineering personnel knowledge, awareness, and expectations with regard to voiding in safety and non-safety related systems 1.6 Operability Determinations and Evaluations The inspectors reviewed the licensee's operability assessments and evaluations resulting from the voiding identified in the CCW, RHR, and containment spray systems. During the review, the inspectors determined that the licensee

-14- Enclosure 1 exhibited challenges in fully evaluating both normal and abnormal plant conditions. During the review of the events on May 24, 2010, the inspectors identified that operations and engineering personnel, after reviewing CCW pump curves and operator reports, determined that the low-pressure limit switch was the potential cause of the standby CCW pump automatic start. Review of the pump startup curves indicated a reduction in motor amperage, discharge pressure and flow, which are indicative of system voiding. In addition, the reduced discharge pressure, shown on the curves, revealed that the low-pressure switch acted as expected and the startup of the standby pump was a result of the voiding not a failed pressure switch. In addition, it was determined that the personnel at the pump observed flow oscillations and vibrations during the startup of CCW pump A. During interviews operations and engineering personnel understood that gas voids in the system would cause flow oscillations and vibrations, but did not consider this abnormal due to being a normal occurrence. This was similar to the failure of the licensee to identify previous cycling of RHR minimum flow valve EJ-FCV-610, in which, engineering personnel identified the valve cycling before the June 28, 2010, event without taking any corrective action. This issue is further discussed in Section 2.1 of this report. During the review of Operability Evaluation EJ-10-009 for the RHR system voiding the inspectors identified that the licensee did not consider the possibility of the void transferring to the high head safety injection pumps (further discussed in Section 2.4) while evaluating the effects of the 7.9 cubic foot void identified in the RHR heat exchanger u-tubes. The licensee addressed this concern in Revision 1 of the operability evaluation. On August 24, 2010, the licensee performed a vacuum fill of RHR train A and reduced the RHR heat exchanger void size to 4.1 cubic feet. Revision 2 of the operability evaluation was completed to account for the smaller void size and a slight calculation error identified during the revision. The inspectors determined from the review of the calculations that the RHR system remained functional. This issue is further discussed in Section 2.3 of this report.

In addition, the inspectors questioned the quantification of the initial void identified in the RHR heat exchanger. The licensee failed to take into account the volume of gas vented from the system when calculating the initial volume of 7.9 cubic feet, and determined an actual initial volume of 9.8 cubic feet when recalculated. The inspectors reviewed the past operability evaluation for the 9.8 cubic foot void size and identified that the licensee did not assess the reduced heat transfer capability of the heat exchanger due to the larger void size. On November 11, 2010, the licensee completed an engineering disposition for the past operability of the RHR heat exchanger. The inspectors determined that the RHR system maintained functionality during the time that the 9.8 cubic foot void was present in the RHR heat exchanger.

Overall, the inspectors determined that the licensee failed to thoroughly evaluate problems when performing operability evaluations.

-15- Enclosure 1 1.7 Reportability Review The inspectors reviewed the licensee's evaluation of the voiding conditions associated with the CCW, RHR, and containment spray systems and determined that the events were not reportable to the NRC in accordance with 10 CFR 50.73. 1.8 Generic Issues The inspectors evaluated the circumstances associated with the potential voiding issue and assessed the root cause analysis. Along with this, the inspectors interviewed numerous licensee personnel and reviewed industry operating experience, evaluations the station had performed to analyze this issue, as well as NRC generic communications with the goal of identifying any potentially generic issues that should be addressed because of this event. The inspectors concluded that, while there is a potential for voiding to occur in any fluid system at any facility, there are no potentially previously unrecognized generic concerns associated with the issues reviewed at Wolf Creek. 2.0 NRC Identified and Self Revealing Findings 2.1 Failure to Promptly Identify and Correct a Condition Adverse to Quality Introduction. The inspectors identified a Green noncited violation of 10 CFR Part 50, Appendix B, Criterion XVI, "Corrective Actions," for the failure to promptly identify voiding conditions in the CCW and RHR system piping. The licensee failed to promptly identify the presence of voids in both the CCW and RHR systems despite unexpected CCW pump auto starts and unexpected audible water hammer and minimum flow valve EJ-FCV-610 cycling during CCW and RHR pump surveillances. Description. The inspectors identified that the licensee failed to promptly identify and correct voiding condition in the following two examples.

Example 1. On May 24, 2010, during the performance of Procedure STS EG-100A, "Component Cooling Water Pumps A/C Inservice Pump Test," the licensee observed the automatic start of the CCW pump A pump due to low discharge pressure. Operations personnel reviewed the pump startup data and identified that the pumps' flow and pressure oscillations had dipped below the low-pressure setting of 25.5 psig causing the auto start of CCW pump C. In addition, an operator stated that there were indications of a low flow condition on the return line of the residual heat removal heat exchanger.

Licensee operation and engineering personnel reviewed data obtained from previous pump starts. During the review, the licensee identified that there were previous pump starts that exhibited similar oscillations in the pumps amperage, flow, and discharge pressure since January 4, 2010. Further inspection identified that the decreases in amperage, flow, and pressure have occurred since May 9, 2007. The licensee determined that these indications were normal and consistent with a normal pump start.

-16- Enclosure 1 On June 1, 2010, the licensee identified voids in the shell side of the RHR train A heat exchanger and at vent valve EJ-V-0163 on the CCW return from the RHR train A heat exchanger to the suction of CCW pumps A and D. On June 2, 2010, the licensee vented the CCW side of RHR train B heat exchanger and identified a 22.1 cubic foot void. Subsequent void monitoring identified additional voided locations resulting in CCW train A being declared inoperable on June 3, 2010, a week after the initial May 24, 2010, event. The licensee continued periodic monitoring and venting of the CCW system and restored operability of the system on June 5, 2010. On June 6, 2010, the licensee identified a larger than the acceptable void affecting CCW train A and declared the train inoperable. The licensee restored operability on June 8, 2010, after additional venting. Example 2. After exiting Refueling Outage 17 in November 2009, at least three RHR inservice test quarterly pump surveillances and other pump runs were performed with only a recirculation flowpath. These pump runs exhibited the abnormal condition of temporary closing and re-opening of the pump minimum flow motor operated valve EJ-FCV-610. The normal stroke closed time for this valve was about 8 seconds. Position indication for the valve was provided on the main control board next to the pump start switch. A system engineer documented the abnormal valve cycling as part of system monitoring documentation but did not initiate a condition report as required per Corrective Action Procedure AP 28 100, "Condition Reports." The minimum flow valve is designed to close on increasing flow above 1700 gpm. Due to an approximately 8 cubic foot void in the heat exchanger, the flow increased to approximately 5000 gpm for about 1 second while collapsing the voided area in the heat exchanger tubes during a pump start.

During Refueling Outage 17, both trains of the RHR system were drained for maintenance. Following the maintenance on November 9, 2009, the RHR train A system was filled and vented per Procedure SYS EJ-110, "RHR System Fill and Vent Including Initial RCS Fill." However, shortly after starting the RHR pump for the train A fill and vent process, the RHR heat exchanger outlet valve was closed by the plant operators to allow for heat up of the reactor coolant system. The impact of closing the heat exchanger outlet valve was that insufficient RHR flow existed to remove the voided heat exchanger tubing. This condition was not discovered until seven months after the fill and vent was performed.

On June 28, 2010, during the quarterly inservice pump test, operators at the pump noted very loud noise and significant shaking of the RHR train A system suction and discharge piping. This resulted in the troubleshooting efforts that, on July 1, 2010, concluded that a void existed in the heat exchanger. Due to potential water hammer concerns, the operators declared the train inoperable due to water hammer concerns. During the troubleshooting efforts, it was noted that for each pump start the pump minimum flow valve was closing despite the expected pump flows being far below the setpoint for the control circuitry to call for valve closure. Recognition of loud noises and unexpected valve operation on RHR pump starts was not entered into the corrective action process from December 2009 until June 28, 2010.

-17- Enclosure 1 Analysis. The licensee's failure to promptly identify a condition adverse to quality was a performance deficiency. Specifically, the licensee failed to promptly identify voided conditions in the RHR train A heat exchanger and CCW system piping and CCW side of both RHR heat exchangers. This finding was more than minor because the failure to correct these conditions adverse to quality affects the associated cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Using Manual Chapter 0609.04, "Phase 1 - Initial Screening and Characterization of Findings," the issue screened as having very low safety significance because it was a qualification deficiency confirmed not to result in a loss of operability. The finding had a crosscutting aspect in the human performance, decision making component, because the licensee failed to use conservative assumptions following indications of gas voiding in the RHR and CCW systems during pump starts [H.1.(b)]. Enforcement. Title 10 of the Code of Federal Regulations, Part 50, Appendix B, Criterion XVI, "Corrective Action," requires, in part, that measures shall be established to assure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and nonconformance are promptly identified and corrected. Contrary to the above, engineering personnel failed to promptly identify and correct gas accumulation and voiding conditions in the CCW and RHR systems. Specifically, from May 24 to June 1, 2010, the licensee failed to promptly identify that voids were adversely affecting the CCW system following an unexpected start of a CCW pump. In addition, from November 9, 2009 to July 1, 2010, the licensee failed to promptly identify that voids in the RHR system were causing abnormal conditions. Because this finding is of very low safety significance and has been entered into the licensee's corrective action program as Condition Report 26417 and 27107, this violation is being treated as a noncited violation, consistent with Section 2.3.2 of the NRC Enforcement Policy: NCV 05000482/2010008-01, "Failure to Promptly Identify and Correct a Condition Adverse to Quality." 2.2 Inadequate Procedure for Fill and Vent of the Component Cooling Water System Introduction. The inspectors identified a self-revealing Green noncited violation of Technical Specification 5.4.1, "Procedures," involving the failure to maintain adequate procedures required for fill and venting of the component cooling water system to prevent gas accumulation and voids to form in the system. Description. During the fall 2009 outage, the licensee filled and vented both trains A and B CCW systems in accordance with Procedure SYS EG-400, "Component Cooling Water System Fill and Vent," Revision 17.

On May 24, 2010, during the performance of STS EG-100A, "Component Cooling Water Pumps A/C Inservice Pump Test," the licensee observed the automatic start of CCW pump A due to low discharge pressure. Operations personnel reviewed the pump startup data and identified that the pumps' flow and pressure oscillations had dipped below the low-pressure setting of 25.5 psig causing the auto start of CCW pump C. In addition, an operator at the pump stated that there were indications of a low flow condition on the return of the residual heat removal heat exchanger. The licensee operations and engineering

-18- Enclosure 1 personnel reviewed past pump start data and determined that the characteristics identified during the pump start had previously occurred. On June 1, 2010, the licensee identified voids in the shell side of RHR train A heat exchanger and vent valve EJ-V-0163 on the CCW return from the heat exchanger to the suction of CCW pumps A and D. On June 2, 2010, the licensee vented the CCW side of the RHR train B heat exchanger and identified a 22.1 cubic foot void. On June 3, 2010, the licensee engineering personnel examined CCW trains A and B suction points and the CCW side of the RHR heat exchangers and found the system water solid. However, ultrasonic testing performed on the train A discharge points identified a total void volume of 2.275 cubic feet. The licensee conducted ultrasonic testing and identified a total of 33 void locations throughout the CCW system. In addition, the CCW train A pump discharge piping contained an inverted U section of piping that could not be statically vented due to the lack of high point vents. Due to the inability of the system to be statically vented, the licensee wrote temporary procedures TMP 10-007, "Component Cooling Water Train A Dynamic Vent," and TMP 10-008, "Component Cooling Water Train B Dynamic Vent," to dynamically vent the system. These procedures were written to ensure that all voids in locations that could not be vented are swept to locations which voids could be vented. Analysis. The licensee's failure to ensure that adequate procedures were available for the filling and venting of the component cooling water system was a performance deficiency. This finding is more than minor because the failure to maintain adequate fill and vent procedures affected the equipment performance attribute of the Mitigating Systems Cornerstone and affects the associated cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Using Manual Chapter 0609.04, "Phase 1 - Initial Screening and Characterization of Findings," Phase 1 Screening Worksheet, the issue screened as having very low safety significance because it was a qualification deficiency confirmed not to result in a loss of operability. No crosscutting aspect was assigned, as this condition was not reflective of current licensee performance. Enforcement. Technical Specification 5.4.1, "Procedures," requires, in part, that written procedures shall be established, implemented, and maintained covering the applicable procedures recommended in Regulatory Guide 1.33, Revision 2, Appendix A, dated February 1978. Regulatory Guide 1.33, Appendix A, Section 3.e, requires, in part, that instructions for filling and venting the component cooling water system should be covered by written procedures. Contrary to the above, from October 2009 until June 1, 2010, the licensee failed to provide adequate instructions for filling and venting the component cooling water system. Specifically, station procedures allowed for gas accumulations in the component cooling water system, which affected the proper operation of the pumps during startup. Because this violation was of very low safety significance and it was entered into the licensee's corrective action program as Condition Report 26420, this violation is being treated as a noncited violation, consistent with Section 2.3.2 of the NRC Enforcement Policy: NCV 05000482/2010008-02,

-19- Enclosure 1 "Inadequate Procedure for the Fill and Vent of the Component Cooling Water System." 2.3 Failure to Perform an Adequate Operability Evaluation Introduction. The inspectors identified a Green noncited violation of 10 CFR Part 50, Appendix B, Criterion V, "Instructions, Procedures, and Drawings,"

regarding the failure to follow the requirements of Procedures AP 28-001, "Operability Evaluations," and AP 26C-004, "Technical Specification Operability," associated with deficiencies resulting from the presence of voiding in the train A RHR heat exchanger. This condition resulted in the failure to adequately address the impact of the voided condition for the high head pumps and the heat removal capacity of the RHR heat exchanger. Description. Following the November 2009 Wolf Creek refueling outage three train A RHR quarterly pump tests exhibited water hammer symptoms related to heat exchanger voiding. On June 28, 2010, during the quarterly inservice pump test, operators at the pump noted very loud noise and significant shaking of the system suction and discharge piping. This resulted in the troubleshooting efforts that, on July 1, 2010, concluded that a void existed in the RHR heat exchanger. The void size in the RHR heat exchanger was initially determined to be 7.9 cubic feet. Wolf Creek engineering staff determined that none of the possible void effects resulted in a loss of component or system operability. On July 4, 2010, Wolf Creek operators declared the RHR system degraded but operable with the still existing void in the RHR heat exchanger because of the relative small void size and insufficient flows needed for transport out of the heat exchanger. An NRC special inspection team reviewed the licensee Operability Evaluation OE EJ-10-009, Revision 0, associated with Condition Report 26463 description of the heat exchanger void. The operability evaluation considered many possible effects of the void including: (1) pump operation, (2) water hammer affecting the RHR piping, valves, nozzles, and pipe supports, (3) the reactor coolant system, (4) heat transfer through the heat exchanger, (5) the combined effects of voiding on both sides of the RHR heat exchanger tubing, and (6) the effects of this gas being injected into the safety injection and charging system pump suctions. The licensee concluded that the RHR system was degraded but operable and the void could remain in the RHR heat exchanger. The NRC inspectors noted that the operability evaluation assumed that insufficient design basis accident flows existed to allow the void to travel to the suction of the safety injection and charging system pumps. The inspectors challenged this assumption. With an unavailable RHR train B pump, cold leg recirculation would require the RHR train A pump to provide flow to both charging pumps and both safety injection pumps. The licensee re-reviewed this aspect of the design basis loss of coolant accidents and determined that the gas in the heat exchanger would transport to the cold leg recirculation path to the suction of the high-pressure pumps. An analyses was performed to determine the distribution of the gas to the various flow paths and the resulting void fractions at the pump inlets. This analysis input assumed a 7.9 cubic foot void and the Wolf Creek emergency core cooling system to the GOTHIC 2-phase flow model. The GOTHIC model determined that the 7.9 cubic foot void size would never result in

-20- Enclosure 1 greater than the operability limit for void fraction at any of the high-pressure pumps. The void was only able to transport out of the RHR heat exchanger at RCS pressures less than 160 psig. At this pressure, the RHR pump itself was able to deliver about 1000 gpm and provide the necessary cooling in this cold leg recirculation mode. At lower reactor coolant system pressures, most of the void bubble would go directly to the reactor coolant system and not affect the suction of the high-pressure pumps. Revision 1 of Operability Evaluation OE EJ-10-009 addressed the inspectors concerns and determined all void fractions were below the operability limit. Revision 2 of the operability evaluation addressed a slight calculation error and justified the void condition after the vacuum fill and vent reduced the void to 4.1 cubic feet. Another assumption error noted by the inspectors was that the original measurement of the RHR heat exchanger void size should have been 9.8 cubic feet. This also resulted in acceptable void fractions at the high-pressure pumps. After the NRC inspection, short-term corrective actions were implemented to perform a vacuum fill and vent of the heat exchanger on August 23, 2010. Long-term corrective actions were addressed by the actions associated with the root cause evaluation performed by Wolf Creek. Analysis. The licensee's failure to perform an adequate operability evaluation for the train A emergency core cooling system voiding discovered on June 28, 2010, was a performance deficiency. This finding is more than minor because it is associated with the Mitigating Systems Cornerstone attribute of equipment performance and adversely affects the objective to ensure equipment availability and reliability. Using Manual Chapter 0609.04, "Phase 1 - Initial Screening and Characterization of Findings," the issue screened as having very low risk significance since the finding did not represent a loss of system safety function. The inspectors determined that this finding had a crosscutting aspect in the area of problem identification and resolution associated with the corrective action program component because the licensee failed to thoroughly evaluate a similar problem such that extent of condition of the voiding was considered and the cause was resolved P.1(c). Enforcement. Title 10 of the Code of Federal Regulations, Part 50, Appendix B, Criterion V, "Instructions, Procedures, and Drawings," requires, in part, that activities affecting quality shall be prescribed by documented instructions or drawings of a type appropriate to the circumstances and shall be accomplished in accordance with these instructions or drawings. Contrary to the above, following discovery of voiding in RHR train A heat exchanger on June 28, 2010, the licensee failed to provide a reasonable basis for operability as required by Step 6.1.4 of Procedure AP 26C-004, "Technical Specification Operability." Because of the very low safety significance and Wolf Creek's action to place this issue in their corrective action program as Condition Report 27109, this violation is being treated as a noncited violation in accordance with Section 2.3.2 of the Enforcement Policy: NCV 05000482/2010008-03, "Failure to Perform an Adequate Operability Evaluation."

-21- Enclosure 1 2.4 Failure to Identify and Correct Inadequate RHR Fill and Vent Procedures Introduction. The inspectors identified a Green noncited violation of 10 CFR Part 50, Appendix B, Criterion XVI, "Corrective Action," for the failure to identify and take prompt corrective actions to address inadequacies in the RHR fill and vent procedure. The licensee failed to perform corrective actions to incorporate minimum flow rates required to sweep air out of the RHR heat exchangers into the system fill and vent procedure during performance of revisions incorporating previous operating experience and corrective actions associated with NRC inspections.

Description. Performance Improvement Report 2002-2765, a Wolf Creek 2002 corrective action document, noted after reviewing industry Callaway Plant operating experience that the Wolf Creek dynamic RHR fill and vent procedure needed improvements. Changes were made to reroute the discharge path for the system fill and vent to the reactor vessel versus the refueling water storage tank suction header. The performance improvement report also noted minimum flow rates to sweep air out of the RHR heat exchanger. Specifically 3268 gpm of flow was listed as required for a heat exchanger fill and vent to achieve a Froude number > 1. Although extensive procedure changes were made, the minimum flow requirement was not added to the procedure. On January 2, 2008, the NRC Special Inspection Report 05000482/2008007 discussed discovery of voids in the Wolf Creek emergency core cooling systems.

Wolf Creek Condition Report 8212-03-31, Action 3694 recommended reviewing/revising emergency core cooling system fill and vent procedures against isometric drawings. Despite the vertical RHR heat exchanger design requiring 3268 gpm of dynamic flow to sweep the RHR tubes, no minimum flow guidance was added to the new fill and vent procedures. Condition Report 8212 was generated as a result of the 2008 voiding in the safety injection system and the NRC follow-up special inspection. During the 2009 refueling outage, both trains of the RHR system were drained for maintenance. Following the maintenance, the trains were to be filled and vented per Procedure SYS EJ-110, "RHR System Fill and Vent Including Initial RCS Fill." However, shortly after starting the RHR pump for the train A fill and vent, the RHR heat exchanger outlet valve was closed by the plant operators to allow heat up of the reactor coolant system. The impact of closing the heat exchanger outlet valve was that insufficient RHR flow existed to remove the void in the heat exchanger tubing. This voided condition was not discovered until seven months after the fill and vent was performed.

After exiting the refueling outage in November 2009, at least three RHR quarterly pump surveillances and other pump runs were performed with only a recirculation flow path. These pump runs exhibited the abnormal condition of temporary closing and re-opening of the pump minimum flow motor operated Valve EJ-FCV-610. Due to an approximately 8 cubic foot void in the heat exchanger the RHR pump flow increased to approximately 5000 gpm for about 1 second while collapsing the voided area in the heat exchanger tubes. On June 28, 2010, during the quarterly pump test, operators at the pump noted very loud noise and significant shaking of the RHR train A system suction and

-22- Enclosure 1 discharge piping. This resulted in the troubleshooting efforts that, on July 1, 2010, concluded that a void existed in the heat exchanger. This led to the operators declaring the RHR train A system inoperable due to water hammer concerns. The licensee determined on July 4, 2010, that the RHR system was degraded but operable with the still existing void in the RHR heat exchanger because of the relative small void size and insufficient flows needed for transport out of the heat exchanger. Analysis. The licensee's failure to promptly identify and correct a condition adverse to quality was a performance deficiency. Specifically, the licensee failed to identify and correct the RHR system fill and vent procedures. This finding is more than minor because it affected the Mitigating Systems Cornerstone attribute of design control for ensuring the availability, reliability, and capability of safety systems. Using Manual Chapter 0609.04, "Phase 1 - Initial Screening and Characterization of Findings," this finding was determined to be of very low safety significance because the voided heat exchanger was a design or qualification deficiency confirmed not to result in loss of operability. The inspectors determined that the finding has a crosscutting aspect in the area of problem identification and resolution associated with the corrective action component because the licensee staff evaluation of previous Performance Improvement Report 2002-2765 was not thorough enough to result in inclusion of minimum flows necessary to sweep voids out of the RHR heat exchanger P.1(c). Enforcement. Title 10 of the Code of Federal Regulations, Part 50, Appendix B, Criterion XVI, "Corrective Action," requires, in part, that measures be established to assure conditions adverse to quality are promptly identified and corrected.

Contrary to the above, the licensee failed to correct the adverse condition of inadequate fill and vent procedures related to removing voiding in the RHR heat exchangers. Specifically, following draining of the RHR trains in November 2009, Procedure SYS EJ-110, "RHR System Fill and Vent Including Initial RCS Fill," was inadequate in that it did not specify the minimum flows necessary to remove the void existing in the heat exchangers. Because this violation is of very low safety significance and has been entered into the licensee's corrective action program as Wolf Creek Condition Report 27106, this violation is being treated as a noncited violation, consistent with Section 2.3.2 of the NRC Enforcement Policy: NCV 05000482/2010008-04, "Failure to Identify and Correct Inadequate RHR Fill and Vent Procedures." AOA6 Meetings Exit Meeting Summary On June 25, 2010, prior to the team's departure from the facility, an inspection debrief was conducted with Mr. M. W. Sunseri, President and CEO, and other members of the licensee staff to apprise them of the teams results to date and to explain that the inspection would continue with in office review pending resolution of all questions.

On July 23, 2010, prior to the teams departure from the facility, an inspection debrief was conducted with Mr. M. W. Sunseri, President and CEO, and other members of the licensee staff

-23- Enclosure 1 to apprise them of the teams results to date and to explain that the inspection would continue with in office review pending resolution of all questions. On November 24, 2010, the team conducted a telephonic exit meeting to present the inspection results to Mr. S. Hedges, Site Vice President, and other members of the licensee staff. The licensee acknowledged the issues presented. The team acknowledged review of proprietary material, as part of the inspection but no proprietary information was retained or included in the report.

A-1 Attachment SUPPLEMENTAL INFORMATION KEY POINTS OF CONTACT Licensee Personnel T. Card, Supervisor Engineer J. Harris, Engineer, Void Management Program J. Harvey, Manager Engineering NSSS J. Lowery, Engineer G. Pendergrass, Manager, Systems Engineering T. Wilson, Root Cause Evaluator (Lead) NRC Personnel C. Long, Senior Resident Inspector C. Peabody, Resident Inspector M. Hay, Branch Chief, TSB D. Loveless, Senior Risk Analyst ITEMS OPENED, CLOSED AND DISCUSSED Opened and Closed 05000482/2010008-01 NCV Failure to Promptly Identify and Correct a Condition Adverse to Quality 05000482/2010008-02 NCV Inadequate Procedure for Fill and Vent of the Component Cooling Water System 05000482/2010008-03 NCV Failure to Perform an Adequate Operability Evaluation 05000482/2010008-04 NCV Failure to Identify and Correct Inadequate RHR Fill and Vent Procedures LIST OF DOCUMENTS REVIEWED PROCEDURES NUMBER TITLE REVISION STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test 24 STS EG-100B Component Cooling Water Pumps B/D Inservice Pump Test 21 STS EG-201A EG RV-9, CCW Surge Tank A Vent Valve Inservice Valve Test 8 STS EG-201B EG RV-10, CCW Surge Tank B Vent Valve Inservice Valve Test 10 AP 20E-001 Industry Operating Experience Program 14 SYS SJ-002 Void Sampling Using A Sample/Purge Rig 1 A-2 Attachment ALR 00-052B CCW PMP A/C Press Lo 6 ALR 00-051C CCW PMP A Flow Lo 6A ALR 00-051D CCW SRG TK A LEV HiLo 6A ALR 00-067F OSA No. 3 3 OP1610102 SOER 97-1, Gas Intrusion Into Safety Injection Systems (Operations Training) 0 SY1300600 Emergency Core Cooling System (Training) 19 ES1310101 ESP Continuing Training 09-Q2 30 ES1310101 ESP Continuing Training 08-Q1 27 ES1350400 Gas Intrusion/Voiding Events Wolf Creek 0 TMP 10-007 Component Cooling Water Train A Dynamic Vent 0 TMP 10-008 Component Cooling Water Train B Dynamic Vent 0 TMP 10-009 CCW Train A Supplying Service Loop with CCW to Radwaste Isolated 0 AP 28-001 Operability Evaluations 17 AP 28-011 Resolving Deficiencies Impacting SSC's 1B AP 26C-004 Technical Specification Operability 20 AP 28A-100 Condition Reports 12 AI 28A-007 Level 2 CR Evaluation 3 SYS EG-401 Component Cooling Water System Drain Procedure 24 SYS EG-400 Component Cooling Water System Fill and Vent 17 SYS EG-400 Component Cooling Water System Fill and Vent 17A AI 21-100 Operations Guidance and Expectations 18 AP 26A-003 10 CFR 50.59 Reviews 10A STN EJ-003A RHR Train A & Common Void Monitoring & Venting 2 STS BG-002 ECCS Valve Check and System Vent 17 STS BG-007A ECCS Valve Check and Train A & Common Void Monitoring and Venting 3 STS BG-007B ECCS Train B Void Monitoring and Venting 3 SYS EJ-110 RHR System Fill and vent Including Initial RCS Fill 48 SYS EJ-110 RHR System Fill and vent Including Initial RCS Fill 52 SYS EJ-120 Startup of a Residual Heat Removal Train 56 SYS EN-400 Containment Spray System Fill and Vent 5 A-3 Attachment SYS EN-400 Containment Spray System Fill and Vent 10 SYS EJ-110 RHR System Fill and Vent 10 AI-28A-003 Rapid Response to Events of Significance 6A AI-28A-004 Incident Investigation Team (IIT) Guidance 3A AI-28A-010 Screening Condition Reports 5 DRAWINGS NUMBER TITLE REVISION M-13EG01 Piping Isometric Component Cooling Water Sys. Aux. Bldg. "A" Train 7 M-11EG01 System Flow Diagram Component Cooling Water 2 M-13EG02 Piping Isometric Component Cooling Water Sys. "A" Train to Fuel Bldg. 1 M-12EG01 Piping & Instrumentation Diagram Component Cooling Water System 16 M-12EG02 Piping & Instrumentation Diagram Component Cooling Water System 19 M-12EG03 Piping & Instrumentation Diagram Component Cooling Water System 9 M-13EG08(Q) Piping Isometric Component Cooling Water Sys. Surge Tank Area 0 M-13EG03(Q) Piping Isometric Component Cooling Water Sys. Auxiliary Bldg. "B" Train 2 M-13EG04 Piping Isometric Component Cooling Water Sys. Auxiliary Bldg. "B" Train 6 M-13EG05 Piping Isometric Component Cooling Water Sys. "B" Train to Fuel Bldg. 2 M-13EG06 Piping Isometric Component Cooling Water Sys. Aux. Bldg. Common Header 9 M-13EG07 Piping Isometric Component Cooling Water Sys. Aux. Bldg. Common Header 2 M-13EG09 Piping Isometric Component Cooling Water System Reactor Building 3 M-13EG18 Piping Isometric Component Cooling Water System Fuel Building 5 M-13EG19 Piping Isometric Component Cooling Water System Radwaste Building 6 A-4 Attachment M-13EG20 Piping Isometric Component Cooling Water System Radwaste Building 0 M-13EG24 Piping Isometric Component Cooling Water Sys. Auxiliary Building 2 M-13EG26 Piping Isometric Component Cooling Water Sys. Aux. Bldg. "A" Train 2 M-12AN01 Piping and Instrumentation Diagram Demineralized Water Storage and Transfer System 27 M-12EF01 Piping & Instrumentation Diagram Essential Service Water System 21 M-12EF02 Piping & Instrumentation Diagram Essential Service Water System 26 E-11005 List of Loads Supplied by Emergency Diesel Generator 33 J-02EG01A(Q) Control Logic Diagram Component Cooling Water System Pumps 5 5739 Vertical Residual Heat Exchanger Details 3 5736 Vertical Residual H.E. Outline Dwg. 5 5737 Vertical Residual Heat Exchanger Assembly 4 5738 Vertical Residual Heat Exchanger Details 4 5740 Vertical Residual Heat Exchanger Details 4 M-01EJ01 RHR System Flow Diagram in Final Safety Analysis Report Voided M-12EJ01 Piping and Instrumentation Diagram Residual Heat Removal System 43 M-12EJ01 Piping and Instrumentation Diagram Containment Spray System 12 M-01EJ01 FSAR System Flow Diagram 6 (Voided) M-13EJ01 Piping Isometric Residual Heat Removal System, Auxiliary Building A 15 M-13EJ02 Piping Isometric Residual Heat Removal System, Auxiliary Building B 11 M-13EJ03 Piping Isometric Residual Heat Removal System, Auxiliary Building A and B 8 M-13EJ04 Piping Isometric Residual Heat Removal System, Reactor Building 6 M-13EJ08 Small Piping Isometric Residual Heat Removal System, Auxiliary Building 0 M-13EJ09 Small Piping Isometric Residual Heat Removal System, Auxiliary Building 1 A-5 Attachment M-13 EN01 Piping Isometric Containment Spray System, Auxiliary Building A 7 M-13EN02 Piping Isometric Containment Spray System, Auxiliary Building B 7 CALCULATIONS NUMBER TITLE REVISION EG-M-040 Evaluation for the maximum void fraction and transient duration to preclude pump mechanical damage for the Component Cooling Water (CCW) EG System 0 EG-M-42 Pump Start up Pressure Surge Due to Gas in CCW RHR Piping 0 EG-M-43 Transport of Non-Condensable Gas in the Wolf Creek CCW System 0 EJ-M-049 Calculate Volume of RHR Heat Exchanger (EEJ01A/B) Above the Top of the Inlet Nozzle (Inside the Shell). (Ref. CR 00025859) 1 EG-M-041 Water Hammer due to Voids in Component Cooling Water (CCW) EG System Piping 0 EG-S-019 Pipe Stress and Support Review Due to Water Hammer Loads in CCW System 0 EJ-M-050 Evaluation of Void at EJ-V-0163 0 M-EG-5 Calculate NPSH Available to the Component Cooling Water Pumps 1 EJ-M-18 Rate of Heat Up of RHR System in Recirculation Mode due to Pump Heat with no CCW 2 EJ-M-013 Thrust/Torque Calculation for EJHV8811A and EJHV8811B December 12, 2005 EJ-M-051 External Pressure Capacities, Tube, Channel, and Piping Vacuum for RHR Heat Exchanger 0 EJ-M-053 Evaluation of Gas Void in Tube Side of RHR Heat Exchanger 0 EJ-M-054 Transport of RHR HX Bubble to the Charging Pumps 0 CONDITION REPORTS (Formerly Performance Improvement Reports) 00011261 00014120 00024847 00025918 00025947 00025948 00025859 00025860 00026210 00026231 00026232 00026240 00026462 00026562 00026565 00011261 00024847 00025918 00026462 00026562 00026774 00026822 00008212 00026565 00028301 A-6 Attachment 00027543 00027575 00026417 00026420 00026492 00027110 00027108 00027109 00027107 00027112 00027106 PERFORMANCE IMPROVEMENT REPORTS 2002-2765 2008-000861 WORK ORDER 10-329334-000 10-329334-044 10-329565-012 06-290742-000 10-329308-000 10-329565-014 10-329334-001 10-329565-003 10-329334-010 10-329334-011 10-329334-012 10-329334-013 10-329334-014 10-329334-016 10-329334-018 10-329334-049 10-329565-013 10-329334-002 10-329334-003 10-329334-004 10-329334-006 10-329334-007 10-329334-008 10-329334-009 10-329334-020 10-329334-047 10-329334-048 10-329334-055 10-329334-056 10-329334-059 10-329565-001 10-329565-004 10-329565-005 10-329565-011 SURVEILLANCE TEST NUMBER TITLE DATE STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test May 28, 2009 STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test August 26, 2009 STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test August 27, 2009 STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test November 25, 2009 STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test February 23, 2010 STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test February 24, 2010 STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test May 24, 2010 STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test June 5, 2010 STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test June 7, 2010 STS EG-100A Component Cooling Water Pumps A/C Inservice Pump Test June 8, 2010 STS EG-100B Component Cooling Water Pumps B/D Inservice Pump Test November 15, 2009 A-7 Attachment STS EG-100B Component Cooling Water Pumps B/D Inservice Pump Test November 16, 2009 STS EG-100B Component Cooling Water Pumps B/D Inservice Pump Test December 17, 2009 STS EG-100B Component Cooling Water Pumps B/D Inservice Pump Test March 16, 2010 STS EG-100B Component Cooling Water Pumps B/D Inservice Pump Test March 17, 2010 STS EG-100B Component Cooling Water Pumps B/D Inservice Pump Test June 17, 2010 STS EG-100B Component Cooling Water Pumps B/D Inservice Pump Test June 18, 2010 TMP 10-007 Dynamic Vent of Train A CCW June 5, 2010 TMP 10-007 Dynamic Vent of Train A CCW June 6, 2010 TMP 10-009 CCW Train A Supplying Service Loop with CCW to Radwaste Isolated June 17, 2010 STS EG-201A EG RV-9, CCW Surge Tank A Vent Valve Inservice Valve Test March 8, 2010 STS EG-201A EG RV-9, CCW Surge Tank A Vent Valve Inservice Valve Test June 8, 2010 STS EG-201B EG RV-10, CCW Surge Tank B Vent Valve Inservice Valve Test May 23, 2010 MISCELLANEOUS NUMBER TITLE REVISION / DATE OE EG-10-006 "A" Component Cooling Water System Voids June 3, 2010 Revision 1 OE EG-10-007 "B" Component Cooling Water System Voids June 4, 2010 Revision 1 OE EJ-10-009 RHR System, Train A 2 OE EJ-10-010 RHR System, Train A July 27, 2010 Revision 1 WCAP 16717-P Wolf Creek Generating Station (SAP) MSIV/MFIV Replacement Project Small Break LOCA Analysis Engineering Report February 7, 2007 FAI/09-130 Technical Basis for Gas Transport to the Pump Suction December 2009M-10EJ Residual Heat Removal 4 A-8 Attachment M-10EN Containment Spray 4 Cycle 17 ECCS 31 day Surveillance Void Trend Cycle 18 ECCS 31 day Surveillance Void Trend Cycle 17 Containment Spray Void Trend Cycle 18 Containment Spray Void Trend Strip Chart Recorder data of B RHR pump flow vs. time for July 2, 2010 troubleshooting Table of RHR run times since November 2008 RHR pump PEJ01A pump performance (graph) since RF17 Engineering Disposition on Gas Voids in ECCS Piping On the Spot Change (OTSC) 10-0037, STS EJ-100A, RHR System Inservice Pump A Test Applicability Determination for Procedure STS EJ-100A, RHR System Inservice Pump A Test, OTSC 10-0037 Event and Causal Factors Chart for Condition Report 00024847, "B' Train ECCS Voiding July 19, 2010 Barrier (HBT) Analysis for Condition Report 00024847, "B" Train ECCS Voiding July 19, 2010 Nine Month Response to NRC Generic Letter 2008-001, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" October 10, 2008 Wolf Creek response to NRC Request for Additional Information RE: Response to NRC Generic Letter 2008-001,

"Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems" August 17, 2009 Engineering Disposition, Past Operability of RHR Heat Exchanger with 9.8 Cubic Foot Void November 11, 2010 Enclosure 2 June 15, 2010 MEMORANDUM TO: Michael Bloodgood, Inspector, Team Leader Technical Support Branch Division of Reactor Safety Matthew Young, Inspector Engineering Branch 1 Division of Reactor Safety FROM: Roy Caniano, Director Division of Reactor Safety

SUBJECT: CHARTER FOR SPECIAL INSPECTION TO EVALUTE GAS ACCUMULATION IN THE COMPONENT COOLING WATER SYSTEM AT WOLF CREEK GENERATING STATION In response to the discovery of voiding in portions of the Component Cooling Water (CCW) System piping, a Special Inspection will be performed. You are hereby designated as the Special Inspection Team Leader. Matthew Young, Inspector, is designated as a team member. The Senior Reactor Analyst assigned to support the team is David Loveless. A. Basis Specifically, on May 24, 2010, during a planned start of CCW Pump A for inservice testing, operators at Wolf Creek observed a pressure drop and a surge tank level drop of 68 gallons. During this system transient, Pump C started unexpectedly on a feature designed to maintain the system pressurized. At the time, the licensee attributed the anomalous system response to a potentially faulty pressure relay. On June 1, 2010, Train A of CCW experienced a 65-gallon surge tank level drop following the start of Pump C. The licensee subsequently determined the May 24 and June 1 level changes were caused by gas pockets in the CCW system. Follow-up venting on June 1, 2010, uncovered the presence of an additional 0.4 cubic feet of gas in the RHR A heat exchanger shell. Also, an extent of condition check of Train B on June 2 uncovered the presence of a 22.4 cubic foot void in that piping. On June 3, 2010, ultrasonic testing of standby CCW Train A identified several additional voids in unvented horizontal piping runs. The licensee declared the standby train inoperable and commenced dynamic venting operations to sweep the voids from the piping. The gas voids are believed to have come from the use of nitrogen saturated fill water after maintenance conducted on the system during the fall 2009 refueling outage. Between that outage and the time the nitrogen gas was vented, the CCW system was degraded and may not have been able to perform its safety functions. Enclosure 2 A regional Senior Reactor Analyst (SRA) estimated the Maximum Conditional Core Damage Probability for this issue to be between 1E-5 and 1E-4, which is in the overlap region between a special inspection and an augmented inspection team. Based on current available information, the NRC staff recommends that the appropriate level of NRC response is the performance of a special inspection. The special inspection activities will include information gathering to determine whether an augmented inspection is warranted, as well as inspections to understand the extent of condition, source of the gas intrusion, past operability, and to assess the adequacy of the licensee's corrective actions. B. Scope The team is expected to address the following: 1. Throughout the inspection coordinate with the regional SRA to ensure the NRC response to the event is consistent with the potential safety significance. 2. Develop a complete sequence of events related to the discovery of the voided conditions and follow-up actions taken by the licensee. 3. Review operating experience involving voiding of CCW System piping and evaluate actions implemented at Wolf Creek as a result of operating experience. 4. Review the current status of the licensee's root cause analysis and determine if it is being conducted at a level of detail commensurate with the significance of the problem. 5. Review the potential cause or causes of any design deficiencies and/or operating practices that allowed the voiding condition to exist. Independently verify key assumptions and facts. 6. Determine if the licensee's immediate corrective actions have addressed the extent of condition for voiding of safety systems and assess whether these actions are adequate to prevent recurrence. Review the adequacy of any long term corrective actions being implemented or planned that address voiding of safety systems. 7. Review the calculations the licensee used to evaluate the voided conditions. Assess the key factors associated with the total volume of the voids including the expected flow rates of the CCW pumps and the potential impact of voids affecting the pumps, valves, and piping systems. 8. Review the licensee's compliance with the Technical Specifications. 9. Verify the licensee met the proper reporting requirements of 10 CFR 50.72 and 10 CFR 50.73. Also determine if the licensee has plans to issue a Licensee Event Report to document this issue. 10. Evaluate the potential for any generic issues related to the discovery of the voided conditions and promptly communicate any potential generic issues to regional management. Enclosure 2 11. In concert with the SRA, collect data as necessary to support a significance determination of issues. C. Guidance Inspection Procedure 93812, "Special Inspection," will be used during this inspection. The inspection should emphasize fact-finding in its review of the circumstance surrounding this event. It is not the responsibility of the team to examine the regulatory process. Safety concerns identified that are not directly to the event should be reported to the Region IV office for appropriate action. The team will report to the site, conduct an entrance, and begin inspection no later than June 21, 2010. While onsite, you will provide daily status briefings to Region IV management, starting on Tuesday, June 22, 2010. Regional management will coordinate with the Office of Nuclear Reactor Regulation to ensure that all other parties are kept informed. The inspection results will be documented in Special Inspection Report 05000482/2010008. This report will be issued within 45 days of the completion of the inspection.

This charter may be modified should the team develop significant new information that warrants review. Should you require support for the final determination of the risk significance of any issue, contact David Loveless at 817-860-8161. If you have any questions concerning this guidance, contact Michael Hay at (817) 276-6527. Enclosure 2 July 14, 2010 MEMORANDUM TO: Michael Bloodgood, Reactor Engineer, Team Leader Technical Support Branch Division of Reactor Safety Matthew Young, Reactor Inspector Engineering Branch 1 Division of Reactor Safety David Dumbacher, Senior Resident Inspector Projects Branch B Division of Reactor Projects FROM: Roy Caniano, Director Division of Reactor Safety

SUBJECT: AMENDED CHARTER FOR SPECIAL INSPECTION TO EVALUTE GAS ACCUMULATION IN THE COMPONENT COOLING WATER SYSTEM AT WOLF CREEK GENERATING STATION In response to the discovery of voiding in portions of the Component Cooling Water (CCW) System piping, a Special Inspection was initiated. Subsequent to the occurrence of voiding in the CCW system, and while the special inspection to review that event was still ongoing, additional voiding was detected in the Train "A" Residual Heat Removal (RHR) and Containment Spray (CS) systems. Consequently, additional inspection is warranted and the charter dated June 15, 2010, is being amended. David Dumbacher, Senior Resident Inspector, Callaway Plant, has been assigned as an additional team member to review the circumstances related to the voiding identified in the RHR and CS systems. David Loveless, Senior Reactor Analyst (SRA) will continue to support the team.

A. Basis Specifically, on May 24, 2010, during a planned start of CCW Pump A for inservice testing, operators at Wolf Creek observed a pressure drop and a surge tank level drop of 68 gallons. During this system transient, Pump C started unexpectedly on a feature designed to maintain the system pressurized. At the time, the licensee attributed the anomalous system response to a faulty pressure relay. On June 1, 2010, Train "A" of CCW experienced a 65-gallon surge tank level drop following the start of Pump C. The licensee subsequently determined the May 24 and June 1 level changes were caused by gas pockets in the CCW system. Follow-up venting on June 1, 2010, uncovered the presence of an additional 0.4 cubic feet of gas in the RHR Train "A" heat exchanger shell. Also, an extent of condition check of Train "B" on June 2, 2010, uncovered the presence of a 22.4 cubic foot void in that piping. On June 3, 2010, ultrasonic testing of standby CCW Train "A" identified several additional voids in unvented horizontal piping runs. The licensee declared the standby train inoperable and commenced dynamic venting operations to sweep the voids from the piping. The gas voids are believed to have come from the use of nitrogen saturated fill water after maintenance conducted on Enclosure 2 the system during the fall 2009 refueling outage. Between that outage and the time the nitrogen gas was vented, the CCW system was degraded and may not have been able to perform its safety functions. A regional SRA estimated the Maximum Conditional Core Damage Probability for this issue to be between 1E-5 and 1E-4, which is in the overlap region between a special inspection and an augmented inspection team. Based on current available information, the NRC staff recommends that the appropriate level of NRC response is the performance of a special inspection. The special inspection activities will include information gathering to determine whether an augmented inspection is warranted, as well as inspections to understand the extent of condition, source of the gas intrusion, past operability, and to assess the adequacy of the licensee's corrective actions. During the weeks of June 28, 2010, and July 5, 2010, additional voids were discovered in Train "A" of the RHR and CS Systems. Initial causal determinations indicate that the source on the voids discovered in these systems are the same as for the voiding initially discovered in the CCW system. A follow-up estimate of the Conditional Core Damage Probability by a regional SRA, informed by the inspection team for the condition of CCW after their June 21-25, 2010, onsite inspection, combined with the RHR and CS inoperability showed no appreciable change in the risk values. B. Scope The team is expected to address the following: 12. Throughout the inspection coordinate with the regional SRA to ensure the NRC response to the event is consistent with the potential safety significance. 13. Develop a complete sequence of events related to the discovery of the voided conditions for each system with voids and follow-up actions taken by the licensee. 14. Review operating experience involving voiding of CCW, RHR and CS System piping and evaluate actions implemented at Wolf Creek as a result of operating experience. 15. Review the current status of the licensee's root cause analysis and determine if it is being conducted at a level of detail commensurate with the significance of the problem. 16. Review the potential cause or causes of any design deficiencies and/or operating practices that allowed the voiding condition to exist in each system. Independently verify key assumptions and facts. 17. Determine if the licensee's immediate corrective actions have addressed the extent of condition and extent of cause for voiding of safety systems and assess whether these actions are adequate to prevent recurrence. Review the adequacy of any long term corrective actions being implemented or planned that address voiding of safety systems, including any actions enacted for Generic Letter 2008-01, "Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems," and the NRC inspection detailed in Inspection Report 05000482/2008007. Enclosure 2 18. Review the calculations the licensee used to evaluate the voided conditions. Assess the key factors associated with the total volume of the voids including the expected flow rates of the pumps and the potential impact of voids affecting the pumps, valves, and piping systems. 19. Review the licensee's compliance with the Technical Specifications. 20. Verify the licensee met the proper reporting requirements of 10 CFR 50.72 and 10 CFR 50.73. Also determine if the licensee has plans to issue a Licensee Event Report to document this issue. 21. Evaluate the potential for any generic issues related to the discovery of the voided conditions and promptly communicate any potential generic issues to regional management. 22. In concert with the SRA, collect data as necessary to support a significance determination of issues. This includes determinations on the functionality of the CCW, RHR, CS, and any other systems with the presence of indicated voids. C. Guidance Inspection Procedure 93812, "Special Inspection," will be used during this inspection. The inspection should emphasize fact-finding in its review of the circumstance surrounding this event. It is not the responsibility of the team to examine the regulatory process. Safety concerns identified that are not directly to the event should be reported to the Region IV office for appropriate action. The team will report to the site, conduct an entrance, and begin inspection no later than June 21, 2010. While onsite, you will provide daily status briefings to Region IV management, starting on Tuesday, June 22, 2010. Regional management will coordinate with the Office of Nuclear Reactor Regulation to ensure that all other parties are kept informed. The inspection results will be documented in Special Inspection Report 05000482/2010008. This report will be issued within 45 days of the completion of the inspection. This charter may be modified should the team develop significant new information that warrants review. Should you have any questions concerning this guidance, contact Michael Hay at (817) 276-6527.

IR 05000482/2010008

Text

Dear Mr. Sunseri:

Enclosure:

Enclosure:

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