ML111890441
| ML111890441 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 07/08/2011 |
| From: | Joustra J Decommissioning Branch I |
| To: | Pacilio M Exelon Nuclear, Exelon Generation Co |
| References | |
| IR-10-010 | |
| Download: ML111890441 (12) | |
See also: IR 05000277/2010010
Text
UNITED STATES
NUCLEAR REGULATORY COM MISSION
REGION I
475 ALLENDALE ROAD
KING OF PRUSSIA, PENNSYLVANIA 19406-1415
July 8,2011
Docket No. 05000277 License No. DPR-44
MichaelJ. Pacilio
Senior Vice President, Exelon Generation Company, LLC
President and Chief Nuclear Officer, Exelon Nuclear
4300 Winfield Road
Warrenville. lL 60555
SUBJECT: PEACH BOTTOM ATOMIC POWER STATION - NRC ISFSI INSPECTION
REPORT 05000277 1201 00 1 0
Dear Mr. Pacilio:
On November 1 , 2010 through May 27 ,2011 , Mark Roberts, John Nicholson, and Stephen
Hammann of this office conducted a safety inspection at the Peach Bottom Atomic Power
Station of activities authorized by the above listed NRC license. The inspection was limited to a
review of routine and non-routine (helium leak of cask #1) activities associated with dry fuel
storage at the Peach Bottom Atomic Power Station and its Independent Spent Fuel Storage
Installation (lSFSI). The findings of the inspection were discussed with Garey Strathes, and
other members of your staff of your organization, at the conclusion of the inspection. The
enclosed report presents the results of this inspection.
The inspection examined activities conducted under your license as they relate to compliance
with the Commission's rules and regulations and with the conditions of your license. The
inspectors reviewed selected procedures and records, observed activities, and interviewed
personnel.
Based on the results of this no findings of significance were identified.
In accordance with 10 CFR Part 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 component of the NRC's
document system (ADAMS). ADAMS is accessible from the NRC Web Site at
http ://vr,rww. nrc. qov/readi no-rm/adams. html (the Pu blic Electric Reading Room).
M. Pacillo
Thank you for your cooperation during this inspection.
Decommissioning Branch
Division of Nuclear Materials Safety
Enclosure:
lnspection Report No. 05000277 l2O1OO1O
cc: dencl: Distribution via List Serv
M. Pacillo
Thank you for your cooperation during this inspection.
Sincerely,
/RA/ Kathy Modes for:
Judith A. Joustra, Chief
Decommissioning Branch
Division of Nuclear Materials Safety
Enclosure:
f nspection Report No. 05000277 12010010
cc: Mencl: Distribution via List Serv
Distribution w/encl: (via E-mail)
W. Dean, RA (RIORAMAIL Resource) S. lbarrola. DRP
D. Lew, DRA (RIORAMAlL Resource) F. Bower, DRP, SRI
D. Roberts, DRP (RIDRPMAlL Resource) A. Ziedonis, DRP, Rl
J. Clifford, DRP (RIDRPMAlL Resource) S. Schmitt, DRP, OA
C. Miller, DRS (RlDRSMailResource) S. Bush-Goddard, Rl OEDO
RidsNrrPMPeachBottom Resource
P. Wilson, DRS (RlDRSMail Resource)
RidsNrDorlLpl 1 -2 Resource
P. Krohn, DRP
ROPreoorts Resource
A. Rosebrook, DRP
E. Torres, DRP
E. Benner, NMSS
J. Joustra, DNMS
R. Lorson, DNMS
D. Collins, DNMS
M. Roberts, DNMS
S. Hammann, DNMS
J. Nicholson, DNMS
D. Screnci, PAO
N. Sheehan. PAO
DOCUMENT NAME: G :\WordDocs\Current\lnsp Letter\LDPR-44.201 00 1 0'doc
SUNSI Review Complete: MRoberts ML111890441
After declaring this document 'An Official Agency Record' it will be released to the Public.
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OFFICE DNMS/RI I N DNMS/RI DNMS/RI DNMS/RI
NAME MRoberts/mcr JNicholsonimcr for: SHammann/sth JJoustra/kdm for
0710812011 07t08t2011 07t08t2011 0710812011
DATE
OFFICIAL RECORD COPY
U.S. NUCLEAR REGULATORY COMMISSION
REGION I
INSPECTION REPORT
lnspection No. 45400277t2010010
Docket No. 05000277
License No. DPR-44
Licensee: Exelon Nuclear
Location: Peach Bottom Atomic Power Station
1848 Lay Road
Delta, PA.17314
Inspection Dates: November 1,2010 - May 27,2011
lnspectors: Mark Roberts, Senior Health Physicist
Decommissioning Branch
Division of Nuclear Materials Safety
Stephen Hammann, Senior Health Physicist
Decommissioning Branch
Division of Nuclear Materials Safety
John Nicholson, Health Physicist
Decommissioning Branch
Division of Nuclear Materials Safety
Fred Bower, Peach Bottom Senior Resident Inspector
Branch 4
Division of Reactor Projects
Adam Ziedonis, Peach Bottom Resident lnspector
Branch 4
Division of Reactor Projects
Approved By: Judith A. Joustra, Chief
Decommissioning Branch
Division of Nuclear Materials Safety
Document Name: G:\WordDocs\Current\lnsp Report\RDPR-44.201 001 0.doc
EXECUTIVE SUMMARY
Exelon Nuclear
Peach Bottom Atomic Power Station
NRC lnspection Report No. 0500027712010010
The inspection was a review of spent fuel storage activities at the Peach Bottom Atomic Power
Station and the Independent Spent Fuel Storage lnstallation (lSFSl) at the site. The inspection
included a review of activities during a routine spent fuel storage campaign and the
troubleshooting, unloading, root cause evaluation, and corrective action development of a
loaded spent fuel storage cask that had developed a helium leak in the main lid seal. The report
covers announced safety inspection visits conducted by three regional inspectors with support
from two NRC resident inspectors. The inspection included an evaluation of the licensee's
programs for radiation protection, maintenance, and operations as they related to routine
preparation, loading, and transport of a spent fuel cask and the non-routine activities associated
with troubleshooting the helium leak, opening and unloading a loaded cask, conducting a causal
analysis for the leaking cask, and developing and implementing corrective actions.
The licensee safely implemented its maintenance, radiation protection, and operations programs
to support routine and non-routine activities associated with dry fuel storage.
Based on the results of this inspection, no findings were identified.
lnspection Report No. 05000277 12010010
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REPORT DETAILS
1.0 Helium Leak ldentification on ISFSI Gask #1
a. lnspection Scope
The inspectors reviewed the activities related to the response to a low pressure alarm
condition on spent fuel storage cask TN-68-01. The inspectors interviewed personnel
and reviewed the licensee's relevant documents.
b. Observations and Findinqs
Exelon Nuclear utilizes the Transnuclear, Inc. (Transnuclear) TN-68 cask storage system
at the Peach Bottom site for storage of spent fuel assemblies at its lSFSl. TheTN-68
casks are vertical stainless steel casks with bolted lids. A metal (aluminum-clad) O-ring
seal with an inner and an outer sealing surface is fitted into a groove in the bottom of the
cask lid. After loading a cask in the fuel pool with spent fuel assemblies, the cask lid is
bolted on and residual moisture is removed from the cask. When the lid bolts are
torqued into the lid, the two sealing surfaces of the metal O-ring are compressed against
the top of the cask to form two seals. Access to the cask once the lid is in place is
through a pair of vent and drain ports. The cask is back-filled with helium and the drain
and vent ports are bolted on. The vent and drain port covers also have metal O-ring
seals with inner and outer sealing surfaces. The helium backfill provides an inert storage
environment. A helium overpressure tank, positioned on a small port on the cask lid,
supplies helium overpressure to the space between the cask seals. The combined
helium leak rate for all closure seals and the overpressure system is continuously
monitored for indications of helium leakage and compliance with the Certificate of
Compliance (COC) technical specifications. A bolted on carbon steel protective cover,
with an elastomer O-ring seal, provides environmental protection for the cask lid and
helium pressurization system. Currently approximately 50 casks are stored at the Peach
Bottom lSFSl.
On October 11,2010, a cask seal overpressure monitoring system low pressure alarm
was received for Cask TN-68-01. This cask was initially loaded with spent fuel
assemblies on June 12,2000, and was in storage at the lSFSl. Preliminary helium leak-
testing was conducted at the lSFSl. In order to perform further troubleshooting of the low
pressure alarm, the overpressure monitoring system was re-pressurized and the cask
was moved to the Unit 2 Containment Building. Testing conducted on October 27,2010,
identified that a helium leak existed in the cask main lid sealing area at a leak rate
greater than allowed by the ISFSI cask COC technical specifications.
No findings of significance were identified.
c. Conclusions
The licensee identified and responded to a cask seal overpressure monitoring system
low pressure alarm for Cask TN-68-01. The cask was safely moved to the Unit 2
Containment Building where testing confirmed a helium leak in the cask main lid sealing
area at a leak rate greater than allowed by the ISFSI cask COC technical specifications.
1 Inspection Report No. 0500027712010010
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2.0 Helium Leak Troubleshooting on ISFSI Gask #1
a. Inspection Scope
The inspectors reviewed the activities related to troubleshooting the low pressure alarm
condition on cask TN-68-01. The inspectors observed troubleshooting activities
performed on the cask, interviewed personnel, and reviewed the licensee's relevant
documents.
b. Observations and Findinqs
The licensee, in consultation with Transnuclear, re-torqued each of the 48 cask lid bolts
progressively to a level of 900 foot-pounds. The bolt torque sequence was provided by
Transnuclear. Torquing was repeated until there was no visual movement of any bolt
head. The licensee then performed a sequence of helium leak tests and identified that
the outer sealing surface of the main cask lid seal was leaking. The cask inner seal and
the seals on the vent and drain ports were confirmed to be functional. Although the
licensee was able to reduce the helium leak-rate to levels below the requirements of the
COC technical specifications, they decided that they did not want to return the cask to
long-term storage at the lSFSl. Plans were then developed to breach the cask and
unload the spent fuel assemblies back into the spent fuel pool in order to perform
additional inspections on the cask lid and seals.
No findings of significance were identified.
c. Conclusions
The licensee conducted helium leak test troubleshooting of a loaded spent fuel storage
cask and confirmed that the outer sealing surface of the main cask lid seal was leaking.
Plans were developed to breach the cask and unload the spent fuel assemblies back into
the spent fuel pool in order to perform additional inspections on the cask seals.
3.0 Spent Fuel Unloading Activities for ISFSI Cask #1
a. lnspection Scope
The inspectors reviewed the licensee's activities associated with opening the cask,
returning the cask to the spent fuel pool, and unloading the spent fuel back into the spent
fuel poolfuel storage racks. The inspectors interviewed licensee personnel, reviewed
planning documents, and directly observed activities associated with opening, moving,
and unloading the spent fuel cask.
b. Observations and Findinos
The licensee had confirmed through testing that each of the fuel assemblies that were
loaded into the cask were not leaking, when the cask was initially loaded. However,
because the condition of the fuel assemblies in the cask were unknown after ten years of
storage, licensee staff took conservative measures in coordinating maintenance and
radiation protection activities to safely breach the cask. In addition to their own practical
2 Inspection Report No. 0500027712010010
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experience gained from loading spent fuel casks, the licensee used operating experience
gained from another operating nuclear power plant licensee that breached loaded fuel
casks with a similar helium leak problem. Major concerns that were considered if the fuel
integrity had not been maintained were the potential for elevated radiation levels at the
drain and vent port covers, high activity discrete radioactive particles, and release of
fission product gasses. Pre-job briefings by maintenance and radiation protection
personnelwere thorough and appropriately emphasized the areas of major concern.
Radiation protection surveys did not identify significantly elevated radiation levels or
discrete radioactive particles. Radiological surveys and sampling and analysis of the
atmosphere in the cask did not identify any release of fission product gasses once the
cask was breached. The cask was then placed in the Unit 2 fuel pool for removal of the
lid and unloading the fuel assemblies. The cask lid and cask were returned to Unit 2 fuel
floor for inspection and evaluation.
No findings of significance were identified.
c. Conclusions
The licensee safely implemented its plan for breaching the spent fuel cask, placing the
cask in the spent fuel pool, removing the cask lid, unloading spent fuel from the cask,
and returning the cask lid and cask to the fuel floor for inspection. No unusual or
unexpected conditions were identified.
4.0 Evaluation and Gorrective Action Activities
a. lnspection Scope
The inspectors reviewed the licensee's activities associated with the cask seal
evaluation, extent of condition implications, and corrective actions that had been
implemented and proposed. The inspection consisted of field observations, review of
licensee documentation, and interviews with responsible personnel.
b. Observations and Findinqs
Licensee and cask vendor personnel inspected the cask, cask lid, cask lid seals, vent
and drain cover seals, protective cover, and the sealing surfaces on the protective cover.
The inspections of the protective cover were performed during the initial cask
disassembly on the fuel floor. The inspections of the cask, lid, and seals were conducted
after the unloaded cask was returned to the fuel floor. The initial evaluation revealed
corrosion of the main lid outer seal, lower-than-expected torque on some of the main lid
bolts, and corrosion on the threads of the lid bolts. The inner seal remained intact, and
therefore the cask's primary containment was not compromised. Observations when the
protective cover was removed found streaks of rust on the underside of the cover, a
pronounced pattern of rust directly under the access plate, and water or signs of moisture
around most of the bolt lid holes and bolts. The elastomer O-ring seal on the bottom of
the protective cover was found to be completely intact and sealed against the top of the
cask lid.
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In order to determine the root cause of the event, the licensee initiated a root cause
evaluation that included licensee and vendor personnel. The evaluation team concluded
that the mechanical cause of the helium leak was determined to be galvanic corrosion of
the main lid's outer seal due to the presence of moisture at the interface of the
aluminum-clad seal and the stainless steel cask body. The presence of the moisture at
the interface of the two dissimilar metals set up a galvanic cell that caused the aluminum
to corrode and allow helium to leak through the outer seal of the metal O-ring. The
helium leak test detection system performed its intended function.
The evaluation team identified two root causes for the event; both associated with the
performance of the protective cover that was intended to prevent water infiltration. The
first root cause was determined to be an inadequate design for sealing the access plate
in the protective cover. The second root cause was the lack of any verification of the
integrity of the water-tight cover. Based on the identified root causes, the licensee
developed two primary corrective actions and additional corrective actions to prevent
recurrence of the event. The two primary corrective actions, both intended to maintain
the integrity of the protective cover, include improving the design of the access plate and
developing a verification method for the integrity of the protective cover seals. The
licensee and cask vendor are currently working on a redesign of the protective cover and
developing a method for testing the integrity of the cover. Installation and testing for
Cask #1 is planned for mid-2012. Additional corrective actions include a change to the
torquing process for the lid bolts and ensuring that the access plate gasket and
protective cover O-ring are inspected at installation. These changes are incorporated in
the current procedure revision.
As part of the extent-of-condition review, the licensee has planned inspections for water
infiltration under the protective cover for the remaining casks that have been previously
loaded. Casks with a similar protective cover design (casks #2 - #9) are scheduled for
testing in August 201 1 followed by testing of the remaining casks (#10 - #52) that had
previous design changes of the protective covers. Replacement of covers is expected to
be based on the test results.
No findings of significance were identified.
c. Conclusions
The licensee conducted evaluations to determine the root cause of the helium-leak event
and concluded that the mechanical cause of the event was corrosion of the lid seal from
water infiltration through the protective cover. The licensee identified two root causes of
the event, both related to performance of the protective cover. Long-term corrective
actions to redesign the access plate to the protective cover and develop an enhanced
cask monitoring method are in the design stages by the licensee and cask vendor and
are expected to be completed and implemented in mid-2012. Short{erm corrective
actions including procedure changes for bolt torquing and verification steps for
confirming the integrity of the elastomer seals on the protective cover and protective
cover access plate have been implemented. As part of its extent of condition review, the
licensee has planned testing of the protective covers of the remaining loaded casks.
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5.0 ISFSI Routine Loading Campaign
a. Inspection Scope
The inspectors observed a routine ISFSI loading campaign from May 23,2011 to May
27,2011. The inspection consisted of field observations, review of license
documentation, and interviews with responsible personnel.
b. Observations and Findinos
The inspectors observed a portion of the cask preparation activities and movement of the
cask from the preparation area into the spent fuel pool. The inspectors then observed
the loading of spent fuel into the cask by the licensee's fuel handlers. The fuel
assemblies were properly identified and verified before being moved into the cask. The
licensee's reactor engineers did a further verification that the correct fuel assemblies had
been loaded by making a video recording of the fully-loaded cask and viewing the
recording for the identification numbers of the fuel assemblies. The inspectors also
viewed portions of the video recording to spot check that the correct spent fuel
assemblies were in the correct locations. The inspectors observed the placement of the
lid on the cask, the removal of the cask from the spent fuel pool and subsequent draining
of the cask and decontamination of the cask. Inspectors also observed placement of the
neutron shield, gamma shield and protective cover on the cask as well as part of the
overpressure system installation. Inspectors toured the ISFSI pad and the GentralAlarm
Station and viewed the alarm system for the cask overpressure system. All ISFSI
procedures and procedures for ISFSl-related activities were examined. The personnel
involved in the various ISFSI activities were interviewed and found to be knowledgeable
and experienced. The pre-job briefings were thorough and covered all aspects of the
activity to be performed.
No findings of significance were identified.
c. Conclusions
The licensee successfully performed the cask loading and storage on the ISFSI pad.
The licensee has a documented ISFSI program and trained personnel needed to meet
the criteria set forth in the Certificate of Compliance (CoC), Final Safety Analysis Report
(FSAR), and NRC regulations for an lSFSl.
Exit Meetinq Summarv
The inspection results were discussed with Garey Stathes, Site Manager and members of his
staff on May 27,2011, at the conclusion of on-site inspection activities.
ATTACHMENT: SUPPLEMENTAL INFORMATION
5 lnspection Report No. 05000277 12010010
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SUPPLEMENTAL INFORMATION
PARTIAL LIST OF PERSONS CONTACTED
Licensee
Jim Armstrong, Regulatory Assurance Manager
Jimmy Carter, Reactor Services Manager - Oyster Creek
Brian Cummings, Site Reactor Services Manager
Mark Dedrich, ISFSI Project Manager
Nick Dube, Reactor Services Supervisor
Dave Foss, Regulatory Assurance
Stuart Gray, Fuel Handling Director
Steve Hess, NOS Manager
Carl Kelly, Reactor Services Supervisor
Dan Kern, Lead Radiation Protection Technician
Brian Kozemchak, Work Group Supervisor
Pat Navin, Operations Director
Sarah Shewmaker, Reactor Engineer
Ron Smith, Regulatory Assurance
Garey Stathes, Plant Manager
Mike Summers, Reactor Services Supervisor
INSPECTION PROCEDURES USED
60855 Operation of an Independent Spent Fuel Storage Installation
60855.1 Operation of an Independent Spent Fuel Storage Installation at Operating Plants
ITEMS OPEN. CLOSED. AND DISCUSSED
None
LIST OF DOCUMENTS REVIEWED
50.59 Evaluation No. PB-2010-02-E
50.59 Screening No. PB-2010-019-5
7 2.48 Screening PB-201 1 -40-S
72.75 (g) Cask Event Report, December 1,2010
AR 01 131123 Report, ISFSI Cask #1 - Potential Helium Leak
AR 01201309 Report, ISFSI Cask #1 - Prepare for Storage
AR 01202466 Report, Site Align With ISFSI CoC and FSAR Review
AR 01207763 Report, lnspect ISFSI Casks 2-9 for Water Intrusion
AR01207767 Report, Inspect ISFSI Casks 10-20 forWater Intrusion
AR01207768 Report, lnspect ISFSI Casks 21-52 for Water Intrusion
AR01214782 Report, ISFSI Cask 45 Main Lid Binding On Guide Pins
AR 01219452 Report, ISFSI Cask TN-68-47 0 Degree Upper Trunnion Gauge
ECR PB 10-00061 000, Incorporate TN-68 Amendment 1
ECR PB 11-00099 000, Process Rev. 5 of TN-68 Dry Storage Cask FSAR
6 lnspection Report No. 0500027712010010
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ECR PB 11-00250 000, Removal of ISFSI Cask Alignment Pin for Lid Installation
FH-35, Control of Material Movement in the Fuel Pool
lR 1131123 ISFSI Cask #1 Helium Leakage - Root Cause
Letter TN to PB, Subject: Guidance for Rework of Damaged TN-68-47-0 Upper Trunnion
LS-AA-104-1001, 50.59 Review Coversheet Form
LS-AA-1 04-1 002, 50.59 Applicability Review Form
LS-AA-1 04-1004, 50.59 Evaluation Form PB-201 0-02-E
MA-AA-71 6-008, Foreign Material Exclusion Requirements
Micro ALARA Ptan 10-085, ISFSI Cask 1 (TN-68-1), Transport to/from pad, Troubleshoot,
Repair & Associated Support
Micro ALARA Plan 10-086, ISFSI Cask 1 (TN-68-1), Insert into SFP, Unload and/or repair main
lid seal
RT-W-071-901-2,ISFSI Cask and Storage Area Inspection
SF-150, Control of Cask Placement and Location on ISFSI Pad
SF-210, Preparation For An lndependent Spent Fuel Storage lnstallation Campaign
SF-220, Spent Fuel Casks TN-68-01 through TN-68-47 Loading and Transport Operations
SF-250, Varian 979-70 Helium Leak Detector Operations and Calibration
SF-290, Spent Fuel Cask Transport and Unloading Operations
SF-300, TN-68 Cask Spent FuelAssemblies Storage Selection and Document Requirements
SF-420, Radiation Protection Requirements During Spent Fuel Cask Loading and Transport
Operations
SF-490, Radiation Protection Requirements During Spent Fuel Cask Unloading and Transport
Operations
ST-H-071-804-2, ISFSI Casks TN-68-48 through TN-68-52 Surface Dose Rate and
Contamination
TN-68 Generic Technical Specifications
TN Drawing9T2-30-1
TN Drawing 972-70-2
LIST OF ACRONYMS USED
ADAMS Agency Wide Document Access and Management System
CFR Code of Federa.l Regulations
COC Certificate of Compliance
FSAR Final Safety Analysis Report
ISFSI Independent Spent Fuel Storage Installation
NRC Nuclear Regulatory Commission
lnspection Report No. 05000277 12010010
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