ML110550313

Spent Fuel Pool Criticality Documents

ML110550313
Person / Time
Site:	Peach Bottom
Issue date:	02/23/2011
From:	David Helker Exelon Generation Co, Exelon Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML110550313 (14)

Text

Ex&on Nudear Exeen 200 Exelon Way K0000ttScfuare, PA9,48 February 23, February 23, 2011 2011 UU.S. Nuclear Regulatory S. Nuclear Regulatory Commission Commission ATTN:

ATTN: Document Document Control Control Desk Desk Washington, DC Washington, DC 20555-0001 20555-0001 Peach Bottom Peach Bottom Atomic Atomic Power Power Station, Units 22 and Station, Units and 33 Facility Operating Renewed Facility Operating License DPR-44 and Nos. DPR-44 License Nos. and DPR-56 DPR-56 Docket Nos, NRC Docket Nos. 50-277 50-277 and and 50-278 50-278

Subject:

Spent Fuel Pool Criticality Documents Documents

Reference:

1)

1) Letter from D. P. Helker Helker (Exelon Generation Company, LLC) LLC) to U.S. Nuclear to US. Nuclear Regulatory Commission, Spent "Spent Fuel Pool Criticality Documents, dated Documents,II dated February 9, 2011 In the Reference 1 1 letter, as requested by the U.S. Nuclear Regulatory Commission Senior Resident Inspector at Peach Bottom Atomic Power Station, Exelon Generation Company, LLC (Exelon) submitted several documents for NRC review. We note that there is no outstanding license amendment request associated with this issue.

In aa telephone discussion between Tom Loomis (Exelon) and John Hughey (U.S. Nuclear Regulatory Commission) on February 18, 2011, Mr. Hughey also requested a copy of Operability Regulatory Operability Evaluation 10-007.

Evaluation 10-007. Attached is that evaluation.

IfIf any any additional additional information information is needed, please contact Tom Loomis at (610) 765-5510.

is needed, Respectfully, Respectfully, David P.

David P. Helker Helker Manager, Licensing &

Manager, Licensing & Regulatory Affairs Regulatory Affairs Exelon Exelon Generation Generation Company, Company, LLC LLC

Attachment:

Operability Operability Evaluation 10-007 Evaluation 10-007 cc:

cc: USNRC USNRC Region Administrator Regional Administrator Region I,I, Regional USNRC USNRC Senior Senior Resident Resident Inspector, PBAPS Inspector, PBAPS USNRC USNRC Project Project Manager, PBAPS Manager, PBAPS R.

R. R.

R. Janati, Janati, Bureau Bureau of Protection (w/o Radiation Protection of Radiation Attachment)

(w/o Attachment)

S.

S. T.

T. Gray, Gray, State State of (w/o Attachment) of Maryland (w/o Attachment)

Maryland

Attachment juowipejjy Ajq1?Jod UOIjeflIBA3 .

LOO-O Operability Evaluation 10..007

OP-AA-108-115 OP-AA-108-i 15 1.0 1.0 ISSUE IDENTIFICATION:

ISSUE IDENTIFICATION:

1.1 IR#: 1127773-03 1.2 1.2 OpEval #:

OpEval #: 10-007 10-007 Revision: 11 Revision:

1.3 1.3 ECEC Number:

Number: N/A N/A Revision:

Revision: N/A N/A HU-AA-1 212 review:

HU-AA-1212 review An HU-AA-1212 An HU-AA-1212 review review was was performed performed andand perper OP-PB-108-115-1002, OP-PB-108-1 15-1002, an ITPR ITPR and a QRT review is required for required for the the Operability Operability Evaluation.

Evaluation.

Revision 11 summary:

Revision summary: This revision corrects This revision corrects the value contained in section 2.3 for the rack with the minimum areal minimum areal density density to match the value contained in paragraph 1.8.1. Revision bars also reflect to match formatting changes.

formatting changes This This isis considered considered a minor revision per OP-AA-1 OP AA-108-115 08-115,, paragraph 4.3.2.24322 and has no impact no impact on on the conclusion of this evaluation.

General Information:

1.4 1.4 Affected Station: Peach Bottom Atomic Power Station

1.5 Units

and3 Units: 2 and 3

1.6 Systems

N/A 1.7 Components Affected:

The affected components are the Boraflex panels utilized in the Unit 2 and Unit Unit 3 Spent Fuel Pool (SFP) storage racks.

1.8 Detailed description of what SSC is degraded or the nonconformi nonconforming condition, by ng condition, by what what means means and when first discovered, and extent of condition for all all similarly affected SSCs: SSCs:

1.8.1 Purnose

Purpose:

This Op-eval addresses aa non-conserva non-conservative tive Technical Specification Specification (4.3.1.1 (4.3.1.1.a) resulting from

.a) resulting from degrading Boraflex due to some of of the fuel rack panels panels having having anan average average areal areal density density less less than than the minimum 2 minimum certified 0.021 2 gm/cm assumed in the spent fuel 0.021 gm/cm assumed in the spent fuel storage rack storage rack criticality criticality analyses analyses forfor Units 22 and 3. This Op Op Eval Eval evaluates evaluates thethe acceptability acceptability of of storing storing fuel bundles in fuel bundles in the the Unit Unit 22 and and 33 SEP SFP storage storage racks racks with with aa minimum minimum B-i B-100 average average area!

areal density density ofof 0.01155 gm/cm 2 , which 0.01155 gm/cm

,

2 which isis 55%

55%

of 0.021g/cm 2 2 0.021 g/cm (45% (45% degradation) degradation).. ThisThis will will show show that that the the SEP SFP will will bebe maintained maintained 5% 5% subcritical subcritical (K eff :s; 0.95).

(Keff 0.95). The The basis basis for for this this approach approach is is to to reduce reduce the the design design basis basis limiting limiting fuel fuel assembly assembly reactivity to to aa maximum maximum Kinf of of 1.26, 1.26, which which isis consistent consistent with with NE-AA-61 NF-AA-610, 0, paragraph paragraph 4.6.44.6.4 (2).

(2).

This Op Eval will demonstrate that the Keff for each SEP rack cell is maintained Op Eval will demonstrate that the Keff for each SFP rack cell is maintained subcritical subcritical asas required required by by Tech Tech Specs.

Specs.

Nonconform Nonconforming inQ Condition:

Condition:

The The current current Peach Peach Bottom Bottom Units Units 22 and and 33 high-density high-density Spent Spent Fuel Fuel Pool Pool (SFP)

(SFP) storage storage racks racks were were designed designed and and manufactured manufactured by by Westinghous Westinghouse e Electric Electric Corporation Corporation and and placed placed in-service in-service inin 1986 1986 (Unit 2)

(Unit 2) and and 1989 1989 (Unit (Unit 3)3) under under plant plant modification modification ## 1140.

1140. The The high high density density racks racks utilize utilize Boraflex Boraflex 11

OP-AA-108-115 OP-AA-1 08-1 15 as as aa neutron neutron absorber absorber material material for reactivity reactivity control. It is used to maintain a 5% 5% subcriticality margin. A margin. A Safety Analysis Report Safety Analysis (SAR) in support of the upgraded racks and associated Report (SAR)

Technical Technical Specification Specification changes (Reference 2.5.3.8) was submitted to NRC as part of a License Amendment RequestRequest (LAR) in June of 1985 1985 and supplemented in August of 1985 and December of 1985. Section 3.1 of 1985. 3.1 of this Safety Analysis Report addressed the criticality control capability of the racks. The LAR was subsequently reviewed and approved by NRC, as documented in the racks.

license license amendments amendments 116 116 and 120 120 for Peach Bottom Units 2 and 3, respectively.

The The rack rack Boraflex Boraflex design and Peach Bottom Licensing Basis ensure that the SFP SEP will remain subcritical with the fuel pool fully loaded with fuel assemblies having a Kinf:s. Kf 1.362.

t362. assuming a uniform Boron-10 uniform (B-b) areal density of 0.021 g/

Boron-lO (B-10) ,

2 cm 2 , the minimum certified manufactured B-10 g/cm density. A reduction in the amount of Boraflex in the spent fuel pool racks will reduce the criticality margin (K criticality (Keff eff 0.95) such that actions are required to ensure that the Licensing Basis requirements continue to be met.

requirements In June of 1996, In 1996, the NRC issued Generic Letter 96-04 to address the issue of Boraflex degradation in spent fuel pool storage racks. As documented in NRC Generic letter 96-04, the Electric Power Research Institute (EPRI) identified two issues with respect to using Boraflex in SEP racks. The first issue related to gamma radiation-induced shrinkage of Boraflex and the SFP potential to develop tears or gaps in the material. The second issue concerned long-term Boraflex performance throughout the intended service life of the racks as a result of gamma irradiation and exposure to the wet pool environment. All licensees operating racks containing the Boraflex material were requested to provide an assessment of the physical condition of the Boraflex material and the impact on margin to criticality, as well as proposed actions to monitor ongoing Boraflex degradation.

Nuclears response to the generic letter for Peach Bottom confirmed minimal Boraflex PECo Nuclear's degradation at that time and substantial margin to the regulatory limit existed based on Peach blackness testing" Bottom 2 Boraflex "blackness testing calculations performed using the EPRI-developed RACKLIEE RACKLIFE computer program, and criticality analyses performed by AEA Technologies. PECo Nuclear also implemented an ongoing Boraflex monitoring program, to include RACKLIEE RACKLIFE simulation of the racks and blackness testing using the BADGER B-b B-10 areal density measurement system.

Since 1996 Peach Bottom has continued to monitor the condition of the Boraflex material in in the Unit 2 and 3 racks by evaluating the B-10 B-b areal density of each Boraflex panel using the RACKLIEE computer program at six-month intervals. This monitoring program is controlled by RACKLIFE station procedure RT-R-004-990-2(3), "Boraflex Boraflex surveillance using the RACKLIFE program. program". The RACKLIEE RACKLI FE program has been calibrated using empirical B-b B-10 density data data derived from aa sampling of Boraflex panels. This benchmarking of RACKLIFE is performed approximately 4-performed at approximately 4-year intervals using the EPRI-developed BADGER system. BADGER testing is is controlled by by station procedure RT-R-004-995-2(3), Boraflex "Boraflex surveillance using the BADGER test test device.

device".

Peach Bottom UFSAR Section 10.3 10.3 4.1.1.2, Neutron "Neutron Absorbing Material Material" specifies thatthat the the Boraflex contains a minimum B-10 B-b areal density of 0.021 gm/cm .

2gm/cm 2 . Tech. Spec. 4.3.1.1.a limits Spec. 4.3.1.1.a limits fuel assemblies to a maximum K f 1

Kinf (infinite lattice multiplication factor) of 1.362 1.362 in in the normal normal reactor core configuration at cold conditions. This limit ensures that the fuel pool pool will will remain 5% 5%

subcritical with the SEP SFP fully loaded with fuel assemblies with K f 1

Kinf == 1.362 1.362 assuming assuming the the minimum minimum B-b areal density of 0.021 g/ cm certified B-10 cm 2

• Peach Bottom currently meets

.

2 meets the Kf Kinf criteria, criteria, however, the current design basis analysis for the fuel rack Kf Kinf limit limit was was derived derived using the B-i using the 0 B-10 minimum certified

'minimum certified' areal density of 0.021 gm/cm gm/cm 2 or 11.9%

2 11.9% less than than the the as-manufactured average areal density of 0.0235 g/ cm cm 2 . Per industry standard RACKLIEE

.

2 RACKLIFE Boraflex Boraflex surveillance surveillance testing on November 1, 2010, the average B-i B-100 areal density density for Unit Unit 22 was 0.0203 0.0203 g/cm2 g/cm2 and and for 22

OP-AA-108-115 OP-AA-1 08-1 15 Unit 3 was 0.0209 g/cm2. Panels with the greatest degradation have areal densities of 0.0146 g/cm2 (Unit 2) and 0.0180 g/cm2 glcm2 (Unit 3).

1.8.2 1.82 Fuel Racks:

SEP storage racks provide storage at the bottom of the fuel pool for the spent The high density SFP fuel received from the reactor vessel and new fuel for loading to the reactor vessel. The fuel storage racks at the bottom of the pool are covered with water (normally about 23 ft above the stored fuel) for radiation shielding. Sufficient shielding is provided by maintaining a minimum depth of water at all times. The racks are freestanding, full length top entry and are designed to maintain the spent fuel in a space geometry which preclUdes precludes the possibility of criticality under any conditions. The high density spent fuel storage racks are of the poison "poison" type, utilizing a neutron absorbing material.

Storage Rack:

The high density spent fuel racks are constructed of stainless steel materials and each rack module is composed of cell assemblies, base plate, and base support assembly.

Cell Assembly:

Each cell assembly is composed of (1) a full-length enclosure constructed of 0.075 inch thick stainless steel, (2) sections of Bisco Boraflex (neutron absorbing material) and (3) wrapper plates constructed of 0.020 inch thick stainless steel.

Cell

Enclosure:

The primary functions of the enclosure are to house fuel assemblies, to maintain the necessary separation between assemblies for subcriticality and to provide structural stiffness for the rack module. The inside square dimension of the cell enclosure is 6.070 inches nominal which accommodates either channeled or unchanneled fuel or consolidated fuel assemblies.

Neutron Absorbing Material:

The Bisco Boraflex manufactured by Brand Industrial Services provided the additional neutron absorbing media required above that inherent in the rack structure material. The Boraflex is 10CFR5O, Appendix B, and it consists of boron fabricated to safety-related nuclear criteria of 10CFR50, carbide particles as neutron absorbers held in place by a nonmetallic binder. Boraflex was manufactured with a minimum specified B10 gm/cm 2

• It is a continuous BlO areal density of 0.021 gm/cm

.

2 sheet centered on the length of the active fuel. Depending on the location of the cells in a rack module, some cells have the Boraflex on all four sides, some of three sides and some on two sides, Cells with four wrappers are located in the interior of the rack, cells with three wrappers are sides.

located on the periphery of the rack, and cells with two (adjacent) wrappers are located at the corners of the rack.

Wrapper Plate:

The wrapper plates are attached to the outside of the cell enclosure by intermediate spot welding along the entire length of the wrapper, forming the encapsulation of the Boraflex. A water tight seal is not provided between the wrappers and enclosures since the Boraflex is compatible with the pool environment.

2.0 EVALUATION

2.1 Describe the safety function(s) or safety support function(s) of the SSC. As a minimum the following should be addressed, as applicable, in describing the SSC safety or safety support function(s):

3

OP-AA-108-115 OP-AA-108-1 15 The components associated with this evaluation (Fuel Assemblies and Spent Fuel Racks) are classified Safety Related. The SFP SEP Racks house the spent fuel assemblies and prevent unwanted and uncontrolled criticality. The Boraflex panel areal density does not affect the structural integrity integrity of the SFP SEP racks as the integrity of the inner cell walls and wrapper plates are not dependent upon the Boraflex assemblies for support.

-Does the SSC receive/initiate an RPS or ESF actuation signal?

No. The degraded condition does not affect any electrical or control and instrumentation devices.

The Boraflex panels are physically captured between the side walls of adjacent cells of the spent fuel pool storage racks in Units 2 and 3. The SFPSEP storage racks, including the Boraflex panels receive no actuation signals.

- Is the SSC in the main flow path of an ECCS or support system?

-

No. The Boraflex panels are not part of or in the main flow path of an ECCS system or EGOS ECCS support system.

- Is the SSC used to:

-

- Maintain reactor coolant pressure boundary integrity?

-

No. The subject Boraflex panels are part of the SFP SEP storage racks. The SEP SFP is not part of the reactor coolant pressure boundary (RCPB), and as such do not maintain the RCPB.

- Shutdown the reactor?

-

No. The subject Boraflex panels are part of the SFPSEP storage racks. Their purpose is to ensure the spent fuel remains subcritical. Boraflex is not associated with the Control Rods or the Standby Liquid Control System and hence is not used to shutdown the reactor

- Maintain the reactor in a safe shutdown condition?

-

No. The subject Boraflex panels are part of the SFPSEP storage racks. Their purpose is to ensure the spent fuel remains subcritical. The condition of the SEP SFP storage racks has no impact on maintaining the reactor in a safe shutdown condition.

-Prevent or mitigate the consequences of an accident that could result in offsite exposures comparable to 10 CFR 50.34(a)(1), 10 CFR 5067(b)(2), 50.67(b)(2), or 10 CFR 100.11 100.11 guidelines, as applicable.

Yes. The SFPSEP racks are designed to maintain K eff S 0.95 (5%

Keff (5% subcriticality) for all normal, off-normal and accident conditions. Additionally, under accident conditions, the spent fuel rack design needs to be of sufficient robustness as to prevent offsite exposures which exceed the 10 10 CER 50.34(a)(1),

CFR 50.34(a)(l), 10 CFR CER 50.67(b)(2) and 10 CFR 100.11 guidelines and regulatory limits.

The following accident scenarios involving criticality were considered in the development of the fuel racks:

• drop of a fuel assembly on top of storage racks

• drop of a fuel assembly between the rack periphery and pool wall 4

OP-AA-108-115 OP-AA-108-1 15

• drop of a fuel assembly through the bottom of the storage racks

• Loss of cooling system (lower moderator density reduces Keff) Keff )

The existing station procedures and mitigating actions for SEP SFP accident analyses and offsite exposures are unaffected by the degraded Boraflex condition.

• Does the sseSSC provide required support (i.e., cooling, lubrication, etc.) to aa TS TS required SSe?

SSC?

Yes. Even though the Boraflex panels do not perform a support function like cooling or lubricating, lubricating, their purpose is to ensure the spent fuel remains subcritical, which can be considered to be aa support function.

- Is the sse

- SSC used to provide isolation between safety trains, or between safety and non-safety ties?

No. The Boraflex panels are not used to provide any isolation between safety trains or between safety and non-safety ties. They exist to maintain the spent fuel pool at subcriticality.

- Is the sse

- SSC required to be operated manually to mitigate a design basis event?

No. The Boraflex panels cannot be utilized to mitigate a design basis event. They are passive devices that maintain the spent fuel pool at subcriticality.

- Have all specified safety functions described in TS

- TS been included?

4.3,1 "Criticality" Yes. TS 4.3.1 Criticality specifies that the spent fuel pool storage racks are designed for and shall be maintained with:

Euel assemblies having a maximum K Fuel f 1

K inf of 1.362 in the normal reactor core configuration at cold conditions; (Using the more realistic limit of K Kin =1 .26 is within this value, and

=1.26 therefore acceptable)

K Keff (5% subcritical) if fully flooded with unborated water, which includes an eff ~ 0.95 (5%

allowance for uncertainties as described in Section 10.3 of the UESAR; UFSAR; and a nominal 6.280 inch center to center distance between fuel assemblies placed in the storage racks.

- Have all safety functions of the sse

- SSC required during normal operation and potential accident conditions been included?

Yes. The subject Boraflex panels have one safety function, to ensure the spent fuel remains 5% 5%

subcritical.

- Is the sse

- SSC used to assess conditions for Emergency Action Levels (EAL5)? (EALs)?

No. The subject Boraflex panels are not used to assess the EALs. However, severe degradation could result in abnormal radiation levels necessitating entry into an EAL.

2.2 Describe the following, as applicable:

(a) the effect of the degraded or nonconforming condition on the SSC sse safety function(s) 5

OP-AA-108-115 QP-AA-1 08-115 The subject Boraflex panels are utilized in the spent fuel pool storage racks to ensure the spent fuel remains 5% 5% subcritical. The original Westinghouse design analysis for the racks (and subsequent derived maximum K Kfinf of 1.362) was based on an assumed nominal areal density of 0.021 grams of B-1 B-i 0 per square centimeter of Boraflex material. Reduction of the areal density of the Boraflex material results in a reduction of SFP SEP shutdown margin. However, since none of the fuel stored in either fuel pool has a K Kf inf of greater than 1.26, the SEP SFP subcritical multiplication factor remains less than the 0.95 specified by Tech spec 4.3.1.1(b) 4.3.1.1 (b) for each cell and the overall entire fuel pool. Each SFP SEP storage rack cell currently provides margin to K < 0.95 as required Keff <

by 10 CFR CER 50.68(b)(4) assuming that all stored fuel assemblies have a Kf than1.26.

Kinf of less thanl,26.

sse (b) any requirements or commitments established for the SSC and any challenges to these The Peach Bottom rack criticality analysis is based on the minimum 'minimum certified B-1 0 areal certified' Boraflex B-iO 2

density (0.021 gm/cm ).

2 gm/cm ). The actual average, as fabricated B-iO B-10 areal density of all panels manufactured for the PB2 and 3 racks was 0.0235 gm/cm gm/cm 2 , 11.9%

,

2 11.9% higher than the density assumed in the original analysis.

The existing Peach Bottom Boffom licensing basis rack criticality analysis is based on a bundle with an in-core K Kf inf of 1.362. The aforementioned technical evaluation identifies the margin associated with the actual, as-loaded peak bundle reactivity (in-core K Kfinf of 1.2344).

1.2344). A large majority of assemblies in the Peach Bottom pools have been depleted well beyond peak reactivity conditions, with in-core, cold, uncontrolled K Kfinf values less than 1.0, 1 .0, providing additional currently unaccounted for margin.

Boraflex is used as a neutron absorber material for reactivity control in SEP SFP storage racks. It is used to maintain a 5% 5% subcriticality margin. As defined in Technical Specification 4.3.1 and UESAR 10.3.3 all arrangements of fuel in the spent fuel storage racks must be maintained in a UFSAR subcritical configuration having a Keff K :::; 0.95 for all conditions. UESARUFSAR Section 10.3 10.3 4.1.1.2, 4.1.1.2, "Neutron Material specifies that the Boraflex contains a minimum B-i Neutron Absorbing Material" B-10 density of 0 areal density 2

.

2 gm/cm 0.021 gm/cm

• Per Commitment #T04330 for Boraflex Management Activities per UESAR UFSAR appendix 0, Q, the Boraflex management activities provide for aging management of the spent fuel rack neutron poison material. These activities involve monitoring the condition of Boraflex by routinely sampling fuel pool silica levels and periodically performing in-situ measurement measurement of B-iO B-1 0 areal density. The existing Boraflex management activities (ref UFSAR, Appendix Q, 0, paragraph 2.2) are not impacted by this condition.

(c) the circumstances of the degraded/nonconforming condition, including the possible failure mechanism(s)

Use of Boraflex neutron absorber in SFP SEP storage racks exposes the Boraflex to an aqueous environment as well as high intensity gamma radiation. The synergistic effects of gamma radiation and water cause the chemical composition of the polymer matrix of Boraflex to change from polydimethyl siloxane (PDMS) to amorphous silica, which is somewhat soluble in water. As the transferred matrix dissolves, it releases boron carbide and crystalline silica filler materials to the interior of the fuel racks and eventually to the SFP. SEP. The released boron carbide particles are larger than the silica particles and tend to settle on the floor of the pool and remain there. The smaller crystalline silica particles settle on the horizontal surfaces of the pool, fuel and other equipment in the pool under stagnant conditions. However, when fuel assemblies are moved moved and/or when natural circulation flow increases, such as during refueling operations, the crystalline 6

OP-AA-108-115 OP-AA-1 08-1 15 silica silica can can become become re-suspended re-suspended in the pool water causing pool turbidity due to its high reflectance.

reflectance.

In June In June of 1996 1996 NRCNRC issued Generic Letter 96-04 to address the issue of Boraflex degradation in SEP storage racks.

SFP racks. As documented in NRC Generic letter 96-04, the Energy Power Research Institute (EPRI) identified two issues with respect to using BORAFLEX in SFP Institute (EPRI) SEP racks. The first issue issue related related to gamma radiation-induced radiation-induced shrinkage of BORAFLEX BORAELEX and the potential to develop tears tears or gaps in or gaps in the material.

material. The second issue concerned long-term BORAFLEX performance throughout the intended throughout intended service life of the racks as a result of gamma irradiation and exposure to the wet the wet pool pool environment.

environment. All licensees operating racks containing the Boraflex material were requested to provide an assessment of the physical condition of the Boraflex material and the impact on margin to criticality, as well as proposed actions to monitor ongoing Boraflex degradation.

degradation.

Nuclears response to the generic letter for Peach Bottom confirmed minimal Boraflex PECo Nuclear's degradation at that time and substantial margin to the regulatory limit of 5%

degradation 5% subcritical based on Peach Bottom Peach Boratlex "blackness Bottom 2 Boraflex testing calculations performed using the EPRI-developed blackness testing" RACKLIFE computer program, and criticality analyses performed by AEA Technologies. PECo RACKLIFE Energy also proposed an ongoing Boraflex monitoring program, to include RACKLIFE simulation of the racks and blackness testing using the BADGER B-10 B-b areal density measurement system.

Since 1996 Peach Bottom has continued to monitor the condition of the Boraflex material in the Unit 2 and 3 racks by evaluating the B-10 B-b density of each Boraflex panel using the RACKLIEE RACKLIFE computer program at six-month intervals. This monitoring program is controlled by station Boratlex surveillance using the RACKLIFE program".

procedure RT-R-004-990-2(3), "Boraflex program. The RACKLIFE program has been calibrated using empirical B-10 density data derived from a sampling of Boraflex panels. This benchmarking of RACKLI RACKLIEE FE is performed at approximately 4-year intervals using the EPRI-developed BADGER system. BADGER testing is controlled by station procedure RT-R-004-995-2(3), "BoraflexBoraflex surveillance using the BADGER test device. device".

A reduction in the amount of Boraflex in the SFP SEP racks will reduce the criticality margin (Keff (Keff ::;;

0.95) such that compensatory and corrective actions are required to ensure that the Technical Specification and UFSARUESAR requirements continue to be met. These mitigating actions are Action Item Lisf' described in detail in Section 3.0 "Action List of this Op-Eval.

d) whether the potential failure is time dependent and whether the condition condition will continue continue to degrade and/or will the potential consequences increase Boraflex panel degradation is time dependent. Degradation increases with time as the panels are are continually exposed to radiation fields and water flow.

The rate at which the Boraflex panels degrade is primarily dependent upon upon the activity activity of of the the spent fuel bundles stored adjacent to them. Eor For any particular cell in the spent fuel storage storage racks the Boraflex degradation is not uniform. The reduction in margin is specific and unique unique to aa rack rack cell resulting in local reductions in margin. By ensuring margin for each individual individual cell cell is is maintained, subcriticality for the entire fuel pool is also maintained.

maintained.

This is because:

o Different fuel types (e.g., GNE-2, GNF-2, GE-14, etc...)

etc...) have have different activity levels.

levels.

o Eor a given fuel type, activity decreases with time.

For The potential consequence of the degrading Boraflex, i.e., i.e., reducing the criticality margin margin to aa point point K 0.95, does not increase as degradation continues, however, of exceeding Keff::;; however, the margin will the margin will bebe reduced.

77

OP-AA-108-115 OP-AA-108-1 15 (e) the aggregate effect of the degraded or nonconforming condition in light of other open Op Evals A review of the current Peach Bottom open Op Evals and issues associated with the impacted SSCs has revealed no aggregate or latent failure affects.

YES NO 2.3 Is SSC operability supported? Explain basis (e.g., analysis, test, operating experience, [X [ X]J [[ 1]

engineering judgment, etc.):

If 2.3 =

= NO, notify Operations Shift Management immediately.

If 2.3 =

= YES, clearly document the basis for the determination.

An assessment of margin to criticality limits has been performed for the Peach Bottom spent fuel pool storage racks via IRlR 864431-15, 864431-1 5, R3. The evaluation is premised on all fuel loaded in the racks (Kinf) of less than 11.26 having an in-reactor, cold, uncontrolled infinite lattice multiplication factor (Kf) .26 at GNFs NRC approved TGBLAO6A peak reactivity conditions, as evaluated using GNF's TGBLA06A lattice physics methodology. The evaluation accounts for actual fuel in storage as well as fuel projected to be stored in the future, and relies principally upon criticality analyses previously reviewed and approved by NRC. Historical analysis results have been validated using more current methods and applied in a conservative manner. The condition of the Boraflex panels in the racks has been and will continue to be determined using the industry standard EPRI RACKLIFE methodology, which uses fuel pool silica in conjunction with the gamma exposure history of each panel. The RACKLIFE RACKLI FE model is regularly benchmarked to Boraflex blackness measurements obtained using using the EPRI-developed BADGER system. The BADGER system inserts a neutron source and detector on opposite sides of a panel and measures the areal density of the B-lU B-10 in the panel by comparing the number of neutrons reaching the detector (count rate) with results obtained from a similarly constructed test standard containing a known areal density of B-lU.B-10. The underlying underlying Westinghouse and GNF analyses apply NRC approved methods and account for appropriate modeling biases and uncertainties.

This evaluation concludes that Technical Specification 4.3.1.1 (5% subcriticality requirements) is

.b (5%

4.3.1.1.b currently met for all storage cells in both Peach Bottom fuel pools, and will continue to be met at least until such time as individual Boraflex panels contain a minimum B-lU B-10 areal density of 2

.

2 gm/cm 0.01155 gm/cm

• This evaluation is based on a conservative assessment of reactivity as a B-b areal density in the racks. The most significantly degraded panel in either Peach function of B-10 Bottom fuel pool, as evaluated by the RACKLIFE methodology, is currently operating with an areal 2

0.01 46 gm/cm density of 0.0146 .

2 gm/cm

• To proactively preserve margin, any panel which is determined by RACKLIFE to have an areal density of 0.01155 gm/cm gm/cm 2 will be administratively removed from 2

service.

analysis/Tech-Eval (I(IR Conservatisms with the analysislTech-Eval R 864431, A15, Rev 3) include the following:

1) As described in the Tech Eval (pg. 8) the Delta-K to B-10B-i 0 loading relationship is a conservative treatment of the Westinghouse 95/95 uncertainty band. It results in a more 0.1177% Delta-K to B-b conservative relationship (steeper curve) yielding a 0.11770/0 B-10 loading relationship compared to the original Westinghouse slope of 0.0756%. Therefore, for every 11% B-lU

% B-1 (% Delta-K) is approximately doubled. This 0 density loss the reactivity (%

conservatism is uniformly applied to all B-10 B-b density loss terms.

2) Based on BADGER testing performed in 2001, 2006, & & 2010, the areal density measured has been consistently greater than that predicted by RACKLI RACKLIFE.FE. The lowest measured 8

OP-AA-108-115 OP-AA-1 08-1 15 areal density of any panel in either fuel pool was 0.0169 2 gm/cm 2 (U2 panel 2D61 North, in gm/cm 2

2006) compared to the required 0.01155 gm/cm .*

2 gm/cm

3) The Boraflex panels that have been tested in multiple years have not shown an increase in the degradation rate.

4) All fuel assemblies are considered to have a peak K Kf < 1.26; inf of < 1.26; while the maximum peak reactivity for a bundle in either Unit 2 or 3 fuel pool is 1.2344.

1.2344.

5) Typical discharge bundle burnup is beyond the point of peak reactivity. Therefore, the reactivity of bundles stored in the pool is well below their peak.

Given the aforementioned conservatisms and available margin, continued operation of the Peach Bottom spent fuel pool storage racks is acceptable within the constraints designated below:

1. A fuel rack storage location will be administratively removed from service when RACKLIFE indicates the associated Boraflex panel B-10 B-i 0 average areal density does not meet the 2

minimum 0.01155 gm/cm .

2 gm/cm *

2. The maximum K f 1

Kinf of any stored fuel is limited to :S 1.260 1.260 YES NO 2.4 Are compensatory measures and/or corrective actions required? [X]]

[X [1

[]

If 2.4 =

= YES, complete section 3.0 (if NO, N/A section 3.0).

2.5 Reference Documents 2.5.1 Technical Specifications Sections:

2.5.1.1 Criticality Section 4.3.1, "Criticality" 2.5.2 UFSAR Section:

10,3 4.1.1.2, "Neutron 2.5.2.1 Chapter 10.3 Neutron Absorbing Material" Material 2,5.2.2 Appendix 0.2.2, 2.5.2.2 Boraflex Management Activities (T04330)

Q.2.2, "Boraflex (T04330)"

2.5.3 Other

2.5.3.1 IR 864431-15, "Peach Peach Bottom Boraflex Degradation Technical Evaluation, Revision 3 3" LaSalle Unit 2 SFP 2.5.3.2 EC 357424, "LaSalle SEP Criticality Analyses Impact from Boraflex Degradation Degradation ll LaSalle Unit 2 SFP 2.5.3.3 EC 366864, "LaSalle SEP Criticality Analyses Impact from Boraflex BADGER BADGER Testing Testing" 2.5.3.4 10 CFR 50.68, "Criticality Criticality Accident Requirements" Requirements 2.5.3.5 NUREG 0800, Chapter 9.1.1, Standard Review Plan, Criticality "Criticality Safety of Fresh and Handling Spent Fuel Storage and Handling ll 9

OP-AA-108-115 OP-AA-1 08-1 15 2.5.3.6 NUREG 2.5.3.6 NUREG 0800, 0800, Chapter Chapter 9.1 9.1.2, Standard Review Plan, "New New and Spent Fuel Storage" Storage 2.5.3.7 10 2.5.3.7 10 CFR CFR 50, 50, Appendix A, General Design Criterion (GDC) 61 "Fuel Fuel storage and handling and radioactivity radioactivity control" Prevention of Criticality in Fuel Storage and control and GDC 62, "Prevention Handling Handling" 2.5.3.8 Peach 2.5.3.8 Bottom Atomic Power Station Units 2 &3 Spent Fuel Storage Capacity Peach Bottom Modification Safety Analysis Report, Docket Nos. 50-277 and 50-278, Revision 2, Modification Philadelphia Electric Company, December 1985.

Design Report of High Density Spent Fuel Storage Racks for Philadelphia 2.5.3.9 WNEP 8542, "Design Electric Company, Peach Bottom Atomic Power Station Units 2 & 3" 3 2.5.3.1OGENE-512-92073, 2.5.3.10 GENE-512-92073, "PeachPeach Bottom Atomic Power Station Spent Fuel Pool Storage Kinf Analysis Conversion Analysis" 3.0 ACTION ITEM LIST:

Compensatory Measure #1: Develop method for ensuring new fuel design is limited to a maximum Kinf 1.26 for PBAPS Units 2 & 3.

of 1.26 Responsible Dept./Supv.: NFl Responsible NF/ Tusar Action Due: 12/31/10 Action Tracking #: 1127773, A04 Effects of compensatory action: Controls one of the critical parameters (K 1.26) supporting this (Kinf of << 1.26) op-eval.

Compensatory Measure #2: Revise RT RT-R-004-990-2/3

-R-004-990-2/3 (BORAFLEX Surveillance Using The RACKLIFE Program) to include acceptance criteria sufficient to ensure that the minimum B-b B-10 areal density of any in service panel is > .2

• 2 gm/cm

> 0.01155 gm/cm Responsible Dept./Supv.: PSOR I/ Hesse Action Due: 02/01/2011 Action Tracking #: 1127773, A05 Effects of compensatory action: Controls one of the critical parameters (minimum B-10 B-1 0 areal density density of of 2

)

2 gm/cm any panel is > 0.01155 gm/cm ) supporting this Op-eval.

Compensatory Measure #3: Revise RT-R-004-995-2/3 (Boraflex Surveillance Surveillance Using Using The The BADGER BADGER Test Device) to include acceptance criteria sufficient to ensure that the minimum B-i B-100 areal density density of of 2

any in service panel is > > 0.01155 gm/cm

.

2 gm/cm

• Responsible Dept./Supv.: PSOR/PSORI Hesse Action Due: 02/01/2011 Action Tracking #: 1127773, A06 Effects of compensatory action: Controls one of the critical parameters (minimum B-b B-1 0 areal areal density density of of any panel isis > 0.01155 gm/cm gm/cm 2 ) supporting this Op-eval.

)

2 10 10

Compensatory Measure #4: Develop a procedure to administratively remove any fuel rack storage cell from service which includes a Boraflex panel that does not meet the minimum B-b B-10 areal density of 2

0.01155 gm/cm 0.011 .

2 gm/cm

• This procedure will require a 10 CFR 50.59 review per OP-AA-108-115, paragraph 4.5.18.3.

Dept./Supv.: PSOR 1 Responsible Dept.lSupv.: / Hesse Action Due: 4/01/2011 Action Tracking #: 1127773, A07 Effects of compensatory action: Provides the administrative controls required to ensure fuel pool K Keff remains less than or equal to 0.95.

Corrective Action #1: :: Submit License Amendment request (LAR) supporting installation of borated borated rack inserts, supporting criticality analysis, and associated Tech Spec. changes as a permanent repair/solution for Boraflex degradation. LAR to include criteria for when rack inserts are required to be repairlsolution be installed.

Responsible Dept.lSupv.:

Dept./Supv.: NF/Duniap NE/Dunlap Action Due: 11/04/2011 Action Tracking #: 1127773, A08 Basis for timeliness of corrective action: This due date supports the preparation and review of the updated criticality analysis and having a permanent repair in place prior to having a significant number number of panels with less than the required Boraflex areal density, based on projected panel degradation rates.

Corrective Action #2: Revise tech specs to limit K Kfor inf for new fuel to a maximum of 1.26.

1.26.

Dept./Supv.: Regulatory Assurance 1 Responsible Dept.lSupv.: / Armstrong Action Due: 11/04/2013 Action Tracking #: 1127773, A09 Basis for timeliness of corrective action: This due date supports the goal of having a permanent repair in place prior having a significant number of panels with less than the required Boraflex areal density, based on projected panel degradation rates. The due date also considers the maximum time for regulatory review.

Corrective Action #3: Develop a procedure and process after CA #1 and CA #2 are completed to repair B-iC areal density less than the minimum required (0.01155 gm/cm panels with a B-10 gm/cm 2 ) to support the

)

2 current fuel rack criticality analysis.

Dept./Supv.: PSOR 1/ Hesse Responsible Dept.lSupv.:

Action Due: 5/112014 5/1/2014 Action Tracking #: 1127773, A10 Al 0 Basis for timeliness of corrective action: This procedure cannot be implemented until after CAs CAl s 11 &

&2 are complete.

11

4.0

4.0 SIGNATURES

SIGNATURES:

4.1 4.1 Preparers Preparers Brian Brian Kleback and Dan Dan Thomas (mentor) 11/03/10 Interfacing Interfacing Reviews:

Rx.

Rx. Engineering Steve Hesse, Engineering Steve Hesse, Jeff Holley and Alex Psaros 11/03/10 Reg.

Reg. Assurance Assurance _-=.:=..:..::::...:...:::::.:::::..::::-

Dave Foss _ 11/03/10 4.2 Reviewer Reviewer Mike Hoffman 11/03/10 11/03/10 Corporate Engr. _ _A:....:..:..:.;nd:::..yL-O~ls:.::::o:.:..:n Corporate Andy_Olson _ 11/03/10 1 1/03!10 Nuclear Fuels/

Nuclear Fuels! ITPR ITPR Rosanne Rosanne_Carmean Carmean 11/03/10 1 1!03!10 QRT Skin_Breidenbaucih,_Bill_Reynolds_and_Dave_Henry Skip Breidenbaugh, Bill Reynolds and Dave Henry 11/03/10 4.3 Sr. Manager Design Eng/Designee Concurrence:

Sr. M Weidman 11/5/10 4.4 Operations Shift Management Approval: J. J. Murphy Murnhy 11/03/10 11/03/10 4.5 Ensure the completed form is forwarded to the OEPM for processing and Action Tracking entry as appropriate.

4.0 Revision 11 SIGNATURES:

4.1 Preparers Dan Thomas 11/05/10 11/05/10 Interfacing Reviews:

Rx. Engineering ~-'-A.;;.;.;le::;.;..x;;...;P.....;s;:;.;::a;::.;..ro.;;;;.;s"'_~-----------

Alex Psaros 11/05/10 11/05/10 4.2 Reviewer MikeMike Hoffman Hoffman 11/05/10 11/05/10 4.3 Sr. Manager Design Eng/Designee Concurrence: M M Weidman Weidman 11/05/10 11/05/10 4.4 Operations Shift Management Approval: M. Saare 11/05/10 11/05/10 5.0 OPERABILITY EVALUATION CLOSURE:

5.1 Corrective actions are complete, as necessary, and the OpEval OpEval is ready for closure Date _

(OEPM) 5.2 Operations Shift Management Approval _ Date Date - - - - -

5.3 Ensure the completed form is forwarded to the OEPM for processing, Action Tracking Tracking entry, entry, and and cancellation of any open compensatory measures, as appropriate.

12 12