ML110070347
| ML110070347 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 01/07/2011 |
| From: | Hay M Division of Reactor Safety IV |
| To: | Matthew Sunseri Wolf Creek |
| References | |
| IR-10-008 | |
| Download: ML110070347 (41) | |
See also: IR 05000482/2010008
Text
UNITED STATES
NUCLEAR REGULATO RY COM M I SS I ON
R E G I ON I V
612 EAST LAMAR BLVD, SUI TE 400
ARLI NGTON , TEXAS 76011-4125
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 NRCs initial evaluation
satisfied the criteria in the NRC Management Directive 8.3, NRC Incident Investigation
Program, for conducting a special inspection. The NRCs 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 Commissions 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
NRCs 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
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
-1- 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 NRCs 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 licensees 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
-2- 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).
-3- 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.
-4- 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 NRCs initial evaluation satisfied the criteria in the NRC Management Directive 8.3,
NRC Incident Investigation Program, for conducting a special inspection. The NRCs
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
-5- 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
-6- 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,
-7- 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
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
-8- 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
-9- Enclosure 1
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
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.
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 licensees 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:
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- 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 licensees 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 Licensees Root Cause
The inspectors reviewed and assessed the licensees 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
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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:
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- 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
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 Licensees Corrective Action and Extent of Condition
The inspectors evaluated the scope, adequacy, and timeliness of the licensees
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:
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 licensees 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
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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.
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1.7 Reportability Review
The inspectors reviewed the licensees 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.
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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.
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Analysis. The licensees 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 licensees 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
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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 licensees 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 licensees 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,
-18- 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
-19- 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 licensees 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 Creeks 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.
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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
-21- 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 licensees 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 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
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
-22- 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.
-23- Enclosure 1
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-1 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 0
(Operations Training)
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 0
Isolated
AP 28-001 Operability Evaluations 17
AP 28-011 Resolving Deficiencies Impacting SSCs 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 3
Venting
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-2 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 7
Train
M-11EG01 System Flow Diagram Component Cooling Water 2
M-13EG02 Piping Isometric Component Cooling Water Sys. A Train to 1
Fuel Bldg.
M-12EG01 Piping & Instrumentation Diagram Component Cooling Water 16
System
M-12EG02 Piping & Instrumentation Diagram Component Cooling Water 19
System
M-12EG03 Piping & Instrumentation Diagram Component Cooling Water 9
System
M-13EG08(Q) Piping Isometric Component Cooling Water Sys. Surge Tank 0
Area
M-13EG03(Q) Piping Isometric Component Cooling Water Sys. Auxiliary Bldg. 2
B Train
M-13EG04 Piping Isometric Component Cooling Water Sys. Auxiliary Bldg. 6
B Train
M-13EG05 Piping Isometric Component Cooling Water Sys. B Train to 2
Fuel Bldg.
M-13EG06 Piping Isometric Component Cooling Water Sys. Aux. Bldg. 9
Common Header
M-13EG07 Piping Isometric Component Cooling Water Sys. Aux. Bldg. 2
Common Header
M-13EG09 Piping Isometric Component Cooling Water System Reactor 3
Building
M-13EG18 Piping Isometric Component Cooling Water System Fuel 5
Building
M-13EG19 Piping Isometric Component Cooling Water System Radwaste 6
Building
A-3 Attachment
M-13EG20 Piping Isometric Component Cooling Water System Radwaste 0
Building
M-13EG24 Piping Isometric Component Cooling Water Sys. Auxiliary 2
Building
M-13EG26 Piping Isometric Component Cooling Water Sys. Aux. Bldg. A 2
Train
M-12AN01 Piping and Instrumentation Diagram Demineralized Water 27
Storage and Transfer System
M-12EF01 Piping & Instrumentation Diagram Essential Service Water 21
System
M-12EF02 Piping & Instrumentation Diagram Essential Service Water 26
System
E-11005 List of Loads Supplied by Emergency Diesel Generator 33
J-02EG01A(Q) Control Logic Diagram Component Cooling Water System 5
Pumps
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 43
System
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 15
Building A
M-13EJ02 Piping Isometric Residual Heat Removal System, Auxiliary 11
Building B
M-13EJ03 Piping Isometric Residual Heat Removal System, Auxiliary 8
Building A and B
M-13EJ04 Piping Isometric Residual Heat Removal System, Reactor 6
Building
M-13EJ08 Small Piping Isometric Residual Heat Removal System, Auxiliary 0
Building
M-13EJ09 Small Piping Isometric Residual Heat Removal System, Auxiliary 1
Building
A-4 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 0
duration to preclude pump mechanical damage for the
Component Cooling Water (CCW) EG System
EG-M-42 Pump Start up Pressure Surge Due to Gas in CCW RHR 0
Piping
EG-M-43 Transport of Non-Condensable Gas in the Wolf Creek CCW 0
System
EJ-M-049 Calculate Volume of RHR Heat Exchanger (EEJ01A/B) Above 1
the Top of the Inlet Nozzle (Inside the Shell). (Ref.
CR 00025859)
EG-M-041 Water Hammer due to Voids in Component Cooling Water 0
(CCW) EG System Piping
EG-S-019 Pipe Stress and Support Review Due to Water Hammer 0
Loads in CCW System
EJ-M-050 Evaluation of Void at EJ-V-0163 0
M-EG-5 Calculate NPSH Available to the Component Cooling Water 1
Pumps
EJ-M-18 Rate of Heat Up of RHR System in Recirculation Mode due to 2
Pump Heat with no CCW
EJ-M-013 Thrust/Torque Calculation for EJHV8811A and EJHV8811B December 12,
2005
EJ-M-051 External Pressure Capacities, Tube, Channel, and Piping 0
Vacuum for RHR Heat Exchanger
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-5 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-6 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 June 17,
Isolated 2010
STS EG-201A EG RV-9, CCW Surge Tank A Vent Valve Inservice Valve March 8,
Test 2010
STS EG-201A EG RV-9, CCW Surge Tank A Vent Valve Inservice Valve June 8, 2010
Test
STS EG-201B EG RV-10, CCW Surge Tank B Vent Valve Inservice Valve May 23, 2010
Test
MISCELLANEOUS
NUMBER TITLE REVISION /
DATE
OE EG-10- A Component Cooling Water System Voids June 3, 2010
006 Revision 1
OE EG-10- B Component Cooling Water System Voids June 4, 2010
007 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- Wolf Creek Generating Station (SAP) MSIV/MFIV February 7,
P Replacement Project Small Break LOCA Analysis 2007
Engineering Report
FAI/09-130 Technical Basis for Gas Transport to the Pump Suction December 2009
M-10EJ Residual Heat Removal 4
A-7 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 July 19, 2010
00024847, B Train ECCS Voiding
Barrier (HBT) Analysis for Condition Report 00024847, B July 19, 2010
Train ECCS Voiding
Nine Month Response to NRC Generic Letter 2008-001, October 10,
Managing Gas Accumulation in Emergency Core Cooling, 2008
Decay Heat Removal, and Containment Spray Systems
Wolf Creek response to NRC Request for Additional August 17,
Information RE: Response to NRC Generic Letter 2008-001, 2009
Managing Gas Accumulation in Emergency Core Cooling,
Decay Heat Removal, and Containment Spray Systems
Engineering Disposition, Past Operability of RHR Heat November 11,
Exchanger with 9.8 Cubic Foot Void 2010
A-8 Attachment
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.
-1- 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
licensees 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 licensees 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 licensees 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 licensees 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.
-2- 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.
-3- 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
-4- 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 licensees 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 licensees 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 licensees 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.
-5- 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 licensees 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.
-6- Enclosure 2