L-PI-05-110, Supplement to License Amendment Request (LAR) to Revise the Spent Fuel Pool Criticality Analyses and Technical Specifications (TS) 3.7.17, Spent Fuel Pool Storage and 4.3, Fuel Storage

Supplement to License Amendment Request (LAR) to Revise the Spent Fuel Pool Criticality Analyses and Technical Specifications (TS) 3.7.17, Spent Fuel Pool Storage and 4.3, Fuel Storage

ML053390121
Person / Time
Site:	Prairie Island
Issue date:	12/02/2005
From:	Thomas J. Palmisano Nuclear Management Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
10 CFR 50.90, L-PI-05-110, TAC MC5811, TAC MC5812 WCAP-16517-NP, Rev 0
Download: ML053390121 (83)

Text

DEC 0 2 2005 L-PI-05-110 10 CFR 50.90 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 License Nos. DPR-42 and DPR-60 Supplement to License Amendment Request (LAR) to Revise the Spent Fuel Pool Criticality Analyses and Technical Specifications (TS) 3.7.17, "Spent Fuel Pool Storage" and 4.3, "Fuel Storage" (TAC Nos. MC5811 and MC5812)

By letter dated February 1,2005, Nuclear Management Company (NMC) submitted an LAR to revise the spent fuel pool criticality analyses and Technical Specifications (TS) 3.7.17, "Spent Fuel Pool Storage" and 4.3, "Fuel Storage". By letter dated September 16, 2005, NMC provided responses to the NRC request for additional information regarding this LAR. This letter supplements the subject LAR to address October 6 and November 15, 2005 telephone discussions with the Nuclear Regulatory Commission (NRC) Staff. NMC is submitting this supplement in accordance with the provisions of 10 CFR 50.90.

Enc1osur.e Iprovides supporting information on the regulatory basis for NRC approval of this LAR.

Enclosure 2 to this letter provides Westinghouse WCAP-16517-NP, "Prairie Island Units 1 & 2 Spent Fuel Pool Criticality Analysis", dated November 2005. This WCAP replaces in its entirety the Westinghouse calculation provided as Exhibit D in the NMC February 1, 2005 LAR. This WCAP differs technically from the calculation in that the analysis and results are based on demonstration that kefiis less than 0.995 using no soluble boron, including biases and uncertainties, for the fresh and spent fuel storage configurations.

The WCAP also contains administrative differences that include removal of the Appendices and references to them, and removal of references to Westinghouse internal procedures. This WCAP is marked as Westinghouse Non-Proprietary Class 3 on each page, and therefore, NMC is not requesting that the document be withheld from public disclosure under Title I 0 Code of Federal Regulations Section 2.390.

Enclosure 3 provides revised TS Figure 3.7.17-1, Figure 4.3.1-3 and Figure 4.3.1-4 which have been revised to incorporate the results from WCAP-16517-NP. These figures replace the figures previously submitted in Exhibit C with the NMC February 1, 2005 LAR.

1717 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.1121

Document Control Desk Page 2 The proposed changes in this supplement do not impact the conclusions of the Determination of No Significant Hazards Consideration and Environmental Assessment presented in the February I,2005 submittal as supplemented February 22, 2005 and September 16, 2005.

In accordance with 10 CFR 50.91, NMC is notifying the State of Minnesota of this LAR supplement by transmitting a copy of this letter and enclosures to the designated State Official.

Summarv of Commitments This letter contains no new commitments and no revisions to existing commitments.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on Thomas J. Palmisano Site Vice President, Prairie Island Nuclear Generating Plant Units 1 and 2 Nuclear Management Company, LLC Enclosures (3) cc: Administrator, Region Ill, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC State of Minnesota

Enclosure 1 Regulatory Basis for Prairie Island Nuclear Generating Plant Fuel Storage Criticality Prevention The Prairie lsland Nuclear Generating Plant (PINGP) regulatory basis for fuel storage criticality prevention is Atomic Energy Commission (AEC) General Design Criterion (GDC) 66, "Prevention of Fuel Storage Criticality" as proposed on July 10, 1967. AEC GDC 66 specifies, "Criticality in new and spent fuel storage shall be prevented by physical systems or processes. Such means as geometrically safe configuration shall be emphasized over procedural controls".

Physical systems require analyses, including criticality analyses, to demonstrate that they provide a safe configuration.

For the original plant license, the specific neutron multiplication factor, keR,criteria which the criticality analyses were required to meet to demonstrate compliance with AEC GDC 66 were included in TS Section 5.6.A. The original plant Technical Specifications (TS) required keff5 0.90 with unborated water. This limit became the licensing basis and thus, the regulatory basis for future analyses, through issuance of the PINGP TS by the AEC. Nuclear Management Company (NMC) is not aware of any regulations in effect at that time that specified this neutron multiplication factor limit.

To support reracking of the fuel storage pools, in 1976 Northern States Power Company (NSP') submitted a License Amendment Request (LAR) to the NRC with new criticality analyses and revised TS 5.6.A to limit keff5 0.95 with unborated water. The NRC reviewed and approved the proposed criticality analyses and issued the revised TS in License Amendments (LA) -22 (Unit 1)/16 (Unit 2), dated August 16, 1977. With this license amendment the NRC revised the PINGP licensing basis fuel pool analysis multiplication factor acceptance criteria and the regulatory basis for future analyses to k e5~0.95. NMC is not aware of any regulations in effect at that time that specified this neutron multiplication factor limit.

In the mid-1990s, PINGP was the pilot plant for a Westinghouse Owners Group initiative to license criticality analyses crediting soluble boron. NSP submitted an LAR with new criticality analyses and proposed to revise TS 5.6.A.1 requiring the pool to be maintained with:

b. keff< 1.0 if fully flooded with unborated water, which includes an allowance for uncertainties as described in Reference 3;

c. keff5 0.95 if fully flooded with water borated to 750 ppm, which includes an allowance for uncertainties as described in Reference 3;

' NSP was the plant operating entity prior to NMC.

Page 1 of 2

Reference 3 above was "Northern States Power Prairie Island Units 1 and 2 Spent Fuel Rack Criticality Analysis Using Soluble Boron Credit", Westinghouse Commercial Nuclear Fuel Division, dated February 1997. This analysis utilized the methodology in WCAP-14416-NP-A, "Westinghouse Spent Fuel Rack Criticality Analysis Methodology".

The NRC reviewed and approved the SFP analyses (identified as Reference 3 above) which credited soluble boron and issued TS 5.6.A.1 on June 12, 1997 with the paragraph b. and c. requirements quoted above in LA-1291121. This LA approval was based on NRC approval of WCAP-14416-NP-A. NMC is not aware of any regulations in effect at that time that specified these neutron multiplication factor limits. The multiplication factor analysis limits became the regulatory limit and licensing basis through NRC issuance of the TS. This LA established new PlNGP licensing basis multiplication factors for future fuel storage analyses.

On February I, 2005, NMC submitted an LAR to the NRC with new SFP criticality analyses based on a different methodology and proposed to revise TS curves relating to fuel storage. This LAR proposes to replace the reference in TS 4.32, "Fuel Storage", with a reference to the new analyses. The new analyses continue to meet the current PlNGP licensing basis multiplication factor limits, that is, keff< I.O if fully flooded with unborated water and keff5 0.95 if fully flooded with borated3water. The February 1, 2005 submittal did not propose to change the multiplication factor limits, thus, the current licensing basis continues to be met and these limits form the regulatory basis for issuance of the LA. NMC only proposes to replace the methodology and analyses which demonstrate compliance with these limits.

In conclusion, the regulatory basis, for approving the LAR dated February 1, 2005 as supplemented on February 22,2005, September 16,2005 and by this letter, is AEC GDC 66 as it has been throughout the plant operating history. The current NRC approved licensing basis for demonstrating compliance with AEC GDC 66 is the neutron multiplication factor limits in the current PlNGP TS 4.3.

The methodology and analyses presented in the February 1, 2005 LAR and its supplements demonstrate that these current licensing basis limits are met.

• LA-1581149 converted the PlNGP TS to the format and content guidance of NUREG-1431, "Standard Technical Specifications, Westinghouse Plants". The new TS 4.3 contains the same requirements as TS 5.6.A previously contained.

3 Based on the new analyses, the boron limit is proposed to be changed to 730 ppm.

Page 2 of 2

Enclosure 2 WCAP-16517-NP Prairie Island Units 1 & 2 Spent Fuel Pool Criticality Analysis November 2005 74 pages follow

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP November 2005 Revision 0 Prairie Island Units 1 and 2 Spent Fuel Pool Criticality Analysis

Westinghouse Non-Proprietary Class 3 Prairie Island Units 1 & 2 Spent Fuel Pool Criticality Analysis November, ZOO5 Author:

V. N. Kucukboyaci Approved:

B. J. Johansen, Manager Business Development Westinghouse Electric Company LLC Nuclear Fuel 4350 Northern Pike Monroeville, PA 15146 02005 Westinghouse Electric Company LLC All Rights Reserved "Official Record Electronically Approved in EDMS"

Westinghouse Non-Proprietary Class 3 Table of Contents Section .

Title Page 1.0 Objective ............................................................................................................................

1 1.1 Design Criteria ..............................................................................................................1 1.2 Design Approach ........................................................................................................... 3 1.3 Methodology ................................................................................................................ 3 1.4 Assumptions ..................................................................................................................8 2.0 Design Input .....................................................................................................................

12 2.1 Design Input from NMC ............................................................................................. 12 2.2 Spent Fuel Pool Storage Configuration Description ................................................... 12 2.3 Individual Storage Cell Description ............................................................................ 12 3.0 Analysis ............................................................................................................................

18 3.1 KENO Models ............................................................................................................. 18 3.2 Design Basis Fuel Assembly ....................................................................................... 20 3.3 Modeling of Axial Burnup Distributions .................................................................... 21 3.4 Tolerance / Uncertainty Calculations .......................................................................... 23 3.5 No Soluble Boron 95/95 keffCalculational Results ..................................................... 24 3.6 Soluble Boron ..............................................................................................................27 4.0 Summary of Results ......................................................................................................... 54 4.1 Allowable Storage Configurations and Interfaces ...................................................... 54 4.2 Burnup Credit ..............................................................................................................55 4.3 Total Soluble Boron Requirement ...............................................................................55 5.0 Computer Codes Used In Calculation ............................................................................. 66 6.0 References ........................................................................................................................

67 Page i of iv

Westinghouse Non-Proprietary Class 3 List of Tables Table -

Title Papre Table 1-1 Calculational Results for Cores X Through XXI of the B&W Close Proximity Experiments ........................................................................................... 9 Table 1-2. Calculational Results for Selected Experimental PNL Lattices, Fuel Shipping and Storage Configurations ................................................................... 10 Table 1-3. Standard Material Compositions Employed in Criticality Analysis ....................11 Table 2-1. Prairie Island Units I & 2 Storage Cell Dimensions ............................................ 13 Table 2-2. Prairie Island Units 1 & 2 Spent Fuel Pool #2 Dimensions ................................. 14 Table 3-1. Summary of Fuel Assembly Characteristics .......................................................3 1 Table 3-2. Relative Power, Fuel, and Moderator Temperatures for Eight Zone Mode1........32 Table 3-3. Burnup and Initial Enrichment Combinations Used to Determine the Isotopic Number Densities ................................................................................... 33 Table 3-4. bflfor the Various Physical Tolerance Cases for the "All-Cell" Storage Configuration. .......................................................................................................

34 Table 3-5 bfffor the Various Physical Tolerance Cases for the Unshimmed "3x3" Storage Configuration ......................................................................................... -35 Table 3-6. keK for the Various Physical Tolerance Cases for the Shimmed "3x3" Storage Configuration ......................................................................................... .36 Table 3-7. bffversus Initial Enrichment and Assembly Burnup for the "All-Cell" Storage Configuration with No Soluble Boron .................................................... 37 Table 3-8. bffversus Initial Enrichment and Assembly Burnup for the Unshimmed bb 3x3" Storage Configuration .............................................................................. .38 Table 3-9. keff versus Initial Enrichment and Assembly Burnup for the Shimmed bb 3x3" Storage Configuration .............................................................................. .39 Table 3-10. Fuel Assembly Burnup versus Initial Enrichment for the "All Cell" Storage Configuration ......................................................................................... -40 Table 3- 1 1. Fuel Assembly Burnup versus Initial Enrichment for the Unshimmed bb 3x3" Storage Configuration ................................................................................ 41 Table 3-12. Fuel Assembly Burnup versus Initial Enrichment for the Shimmed "3x3" Storage Configuration ......................................................................................... .42 Table 3-13. Entire Spent Fuel Pool #2 and Infinite Array bRResults for the Allowable Storage Configurations ....................................................................... 43 Table 3-14. bffas a Function of Soluble Boron Level ............................................................ 44 Table 3-15. Reactivity Associated with 5 % Burnup Uncertainty for the Storage Configurations ......................................................................................................

45 Table 3-16. k,ff for Accident Events ........................................................................................46 Page ii of iv

Westinghouse Non-Proprietary Class 3 List of Tables Table -

Title Table4-1. Fuel Assembly Burnup versus Initial Enrichment for the "All-Cell" Storage Configuration ..........................................................................................

56 Table 4-2. Fuel Assembly Burnup versus Initial Enrichment for the Unshimmed "3x3" Storage Configuration as a hnction of decay time .................................... 57 Table 4-3. Fuel Assembly Burnup versus Initial Enrichment for the Gd2O3Shimmed "3x3" Storage Configuration as a function of decay time ................................... 58 Page iii of iv

Westinghouse Non-Proprietary Class 3 List of Figures Table Title

. Page Figure 2.1 . Prairie Island Units 1 & 2 Storage Cell .............................................................. 15 Figure 2.2 . Prairie Island Units 1 & 2 Spent Fuel Pool .......................................................... 16 Figure 2.3 . Prairie Island Units 1 & 2 Assembly Storage Cell .......................................... 17 Figure 3.1 . Westinghouse 14x14 OFA & STD Fuel Assembly .............................................. 47 Figure 3.2 . Gd203 Burnable Absorber Pin Pattern ................................................................. 48 Figure 3.3 . Sketch of Axial Zones Employed in Fuel Assembly ...........................................49 Figure 3.4 . KENO Output Plot of the "All Cell" Model ........................................................ 50 Figure 3.5 . KENO Output Plot of the "3x3" Storage Model .................................................. 51 Figure 3.6 . KENO Output Plot of the "All-Cell" Spent Fuel Pool Model .............................52 Figure 3.7 . KENO Output Plot of the "3x3" Spent Fuel Pool Model ..................................... 53 Figure 4- 1. Allowable Fuel Assembly Combinations for the "All-Cell" Storage Configuration ........................................................................................................

59 Figure 4.2 . Allowable Fuel Assembly Combinations for the Unshimmed "3x3" Storage Configuration ..........................................................................................60 Figure 4.3 . Allowable Fuel Assembly Combinations for the Gd203Shimmed "3x3" Storage Configuration ..........................................................................................61 Figure 4.4 . Boundary Between the "3x3" and "All-Cell" Storage Configurations ................62 Figure 4.5 . Prairie Island Units 1 & 2 Assembly Burnup Requirements for the "All-Cell" Storage Configuration ................................................................................. 63 Figure 4.6 . Assembly Burnup Requirements for the Peripheral Fuel Assemblies in the Unshimmed "3x3" Storage Configuration ....................................................64 Figure 4.7 . Assembly Burnup Requirements for the Peripheral Fuel Assemblies in the Shimmed "3x3" Storage Configuration .........................................................65 Page iv of iv

Westinghouse Non-Proprietary Class 3 1.0 Objective This report presents the results of criticality analyses for the Prairie Island Units 1 & 2 spent he1 storage racks with credit for assembly burnup, Fuel Burnable Absorber (Gd203),2 4 1 decay~ ~ and soluble boron. The primary objectives of this calculation are as follows:

1. To determine the design basis fuel assembly for all of the fuel assembly storage configurations. They include the "All-Cell" and "3x3 array" he1 assembly storage configurations.

2. To determine the assembly burnup versus initial enrichment limits required for safe storage of fuel assemblies in the "All-Cell" storage configuration

3. To determine the assembly burnup versus initial enrichment limits required for safe storage of peripheral fuel assemblies in the "3x3 array" with the center fuel assembly initially enriched to 4.95 wlo 2 3 5 ~ .This will be accomplished with credit for 5, 10, 15, and 20 years of 2 4 1 decay.

~ ~

4. To determine the assembly burnup versus initial enrichment limits required for safe storage of peripheral fuel assemblies in the "3x3 array" with the center fuel assembly initially enriched to 4.95 wlo 2 3 5 and

~ shimmed with 4 Gd203 rods. These limits will be derived based upon a Gd2O3concentration of 4.0 wlo. This will be accomplished with credit for 5, 10, 15, and 20 years of 2 4 1 decay.

~ ~

5. To determine if the current interface between storage configurations is still valid

6. To determine the amount of soluble boron required to maintain bRless than or equal to 0.95, including all biases and uncertainties, assuming the most limiting plausible reactivity accident.

The methodology employed in this analysis for soluble boron credit is analogous to that of Reference 2 and employs analysis criteria consistent with those cited in the Safety Evaluation by the Office of Nuclear Reactor Regulation, Reference 3. Reference 2 was reviewed and approved by the US NRC. The methodology employed in this analysis and in Reference 2 employs axially distributed burnups to represent discharged he1 assemblies. This analysis was prepared in accordance with the Westinghouse Quality Assurance Program.

1.1 Design Criteria The design criteria are consistent with GDC 62, Reference 4, and NRC guidance given in Reference 5. Section 1.4 describes the analysis methods including a description of the computer codes used to perform the criticality safety analysis. A brief summary of the analysis approach and criteria follows.

1. Determine the fresh and spent fuel storage configurations using no soluble boron conditions such that the 95/95 upper tolerance limit value of hff,including applicable Page 1 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP biases and uncertainties, is less than 0.995. This is accomplished with infinite arrays of either fresh or spent fuel assembly configurations. Note that the actual NRC bff limit for this condition is unity. Therefore, an additional safety margin equal to 0.005 Ak,ff units is included in the infinite array analysis results. Additional margin to the bfflimit will be identified based upon the KENO results for the entire spent fuel pool

1. 2.

2. Determine the amount (ppm) of soluble boron necessary to reduce the bffvalue of all storage configurations by at least 0.05 A b f f units. This is accomplished by constructing a KENO model for spent fuel pool #2 which includes the storage configurations which are least sensitive to changes in soluble boron concentration. As an example, storage configurations which contain depleted fuel assemblies (and represented by depleted isotopics) are less reactivity-sensitive to changes in soluble boron concentration than an assembly represented by zero burnup and a relatively low initial fuel enrichment. Note that spent fuel pool #2 is much larger than spent he1 pool #1 and therefore the results will be bounding for both spent fuel pools.

3. Determine the amount of soluble boron necessary to compensate for 5% of the maximum burnup credited in any storage configuration. In addition, determine the amount of soluble boron necessary to account for a reactivity depletion uncertainty equal to 1.0% h k , ~per 30,000 MWDMTU of credited assembly burnup. This is accomplished by multiplying this derivative by the maximum burnup credited in any storage configuration and converting to soluble boron using the data generated in Step 2.

4. Determine the largest increase in reactivity caused by postulated accidents and the corresponding amount of soluble boron needed to offset this reactivity increase.

An alternative form of expressing the soluble boron requirements is given in Reference 3.

The final soluble boron requirement is determined from the following summation.

SBC,,,,, = SBC,, ,,, + SBC, + SBC, Where:

SBC,,,,, = total soluble boron credit requirement (pprn).

SBC,,,,, = soluble boron requirement for 95/95 bffless than or equal to 0.95 (pprn).

SBC, = soluble boron required to account for burnup and reactivity depletion uncertainties (pprn).

SBC, = soluble boron required to maintain bflless than or equal to 0.95 under accident conditions (pprn).

For purposes of the analyses contained herein, minimum burnup limits established for fuel assemblies to be stored in the storage racks do include burnup credit established in a manner which takes into account approximations to the operating history of the he1 Page 2 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP assemblies. Variables such as the axial burnup profile as well as the axial profile of moderator and fuel temperatures have been factored into the analyses. Also, the axial reactivity effect associated with the absence of Gd203 at both ends of the fuel assembly was directly included in this analysis 1.2 Design Approach The Soluble Boron Credit Methodology provides additional reactivity margin in the spent fuel storage analyses which may then be used to implement added flexibility in storage criteria and, for example, to eliminate the need to credit any of the degraded Boraflex.

Boraflex in the spent he1 racks is not credited in this analysis.

All of the storage cells modeled in this analysis employ a realistic representation of the pitch between storage locations. The square storage cell pitch for the "All-Cell" and "3x3" fuel assembly storage configurations employed for this analysis is equal to 9.5 inches.

The selection of the design basis fuel assembly type was based on an evaluation of the variety of fuel assemblies employed in the reactor to date and selecting the most reactive type for a given he1 assembly storage configuration. The candidate fuel assembly types include the Westinghouse and Exxon 14x14 Standard (STD), the Westinghouse 14x14 Optimized (OFA), and the Exxon TOPROD fuel assembly designs. The Westinghouse 14x14 OFA fuel assembly has been evaluated to be the design basis fuel assembly to represent fresh fuel assemblies in the center location of the "3x3" fuel assembly storage configurations. The Westinghouse 14x14 Standard fuel assembly has been evaluated to be the design basis fuel assembly to represent discharged fuel assemblies in the "All-Cell", and peripheral locations of the "3x3" fuel assembly storage configurations. The most reactive moderator conditions (water density equal to 1.0 glcc) will be employed for each he1 assembly storage configuration such that the analysis results are valid over the nominal spent fie1 temperature range (50 to 150 degrees Fahrenheit).

The reactivity characteristics of the storage racks were evaluated using infinite lattice analyses; this environment was employed in the evaluation of the burnup limits versus initial enrichment as well as the evaluation of physical tolerances and uncertainties. A full spent fuel pool model was also employed to evaluate soluble boron worth, the reactivity worth of postulated accidents, and the multiplication factor for the zero soluble boron condition.

1.3 Methodology This section describes the methodology employed to assure the criticality safety of the spent fuel pools and to define limits placed on fresh and depleted fuel assembly storage configurations. The analysis methodology employs: (1) SCALE-PC, a personal computer version of the SCALE-4.3 code system, as documented in Reference 6, with the updated SCALE-4.3 version of the 44 group ENDFB-V neutron cross section library, and (2) the two-dimensional integral transport code DIT, Reference 7, with an ENDFIB-VI neutron cross section library.

Page 3 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP SCALE-PC was used for calculations involving infinite arrays for the "All-Cell" and "3x3" fuel assembly storage configurations. In addition, it was employed in a fwll representation of spent fuel pool #2 to evaluate soluble boron worth and postulated accidents.

SCALE-PC, used in both the benchmarking and the fuel assembly storage configurations, includes the control module CSAS25 and the following functional modules: BONAMI, NITAWL-11, and KENO V.a. All references to KENO in the text to follow should be interpreted as referring to the KENO V.a module.

The DIT code is used for simulation of in-reactor fuel assembly depletion. The following sections describe the application of these codes in more detail.

1.3.1 SCALE-PC The SCALE system was developed for the Nuclear Regulatory Commission to satis@ the need for a standardized method of analysis for evaluation of nuclear fuel facilities and shipping package designs. SCALE-PC is a version of the SCALE code system that runs on specific classes of personal computers.

1.3.2 Validation of SCALE-PC Validation of SCALE-PC for purposes of fuel storage rack analyses is based on the analysis of selected critical experiments from two experimental programs. The first program is the Babcock & Wilcox (B&W) experiments carried out in support of Close Proximity Storage of Power Reactor Fue:l, Reference 8. The second program is the Pacific Northwest Laboratory (PNL) Program carried out in support of the design of Fuel Shipping and Storage Configurations; the experiments of current interest to this effort are documented in Reference 9. Reference 10, as well as several of the relevant thermal experiment evaluations in Reference 11, were found to be useful in updating pertinent experimental data for the PNL experiments.

Nineteen experimental configurations were selected from the B&W experimental program; these consisted of the following experimental cores: Core X, the seven measured configurations of Core XI, Cor~esXI1 through XXI, and Core XIIIA. These analyses employed measured critical data, rather than the extrapolated configurations to a fixed critical water height reported in Reference 8, so as to avoid introducing possible biases or added uncertainties associated with the extrapolation techniques. In addition to the active fuel region of the core, the full environment of the latter region, including the dry fuel above the critical water height, watj represented explicitly in the analyses.

The B&W group of experimental configurations employed variable spacing between individual rod clusters in the nominal 3 x 3 array. In addition, the effects of placing either SS-304 or Borated Aluminum plates of different boron contents in the water channels between rod clusters were measured. Table 1-1 summarizes the results of these analyses.

Eleven experimental configurations were selected from the PNL experimental program.

These experiments included unpoisoned uniform arrays of fuel pins and 2 x 2 arrays of rod clusters with and without interposed SS-304 or B/AI plates of different blackness. As Page 4 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP in the case of the B&W experiments, the full environment of the active fuel region was represented explicitly. Table 1-2 summarizes the results of these analyses.

The approach employed for the determination of the mean calculational bias and the mean calculational variance is based on Criterion 2 of Reference 12. For a given KENO calculated value of bffand associated one sigma uncertainty, the magnitude of k95195 is computed by the following equation; by this definition, there is a 95 percent confidence level that in 95 percent of similar analyses the validated calculational model will yield a multiplication factor less than k95195.

kg,,, = kN

,O + Akh, + MW95 (0: + ~ : m Y 2

Where, k,,,,, is the KENO calculated multiplication factor, Ak,,a,s is the mean calculational method bias, M,,,,, is the 95/95 multiplier appropriate to the degrees of freedom for the number of validation analyses, and is obtained from the Tables of Reference 13.

0: is the mean calculational method variance deduced from the validation analyses, oi,cNo is the square of the KENO standard deviation.

M,,,,, ( a  :+ oii;NO)'I2is equal to the methodology uncertainty The equation for the mean calculational methods bias is as follows.

Where k, is the iih value of the multiplication factor for the validation lattices of interest.

The equation for the mean calculational variance of the relevant validating multiplication factors is as follows.

where k,,, is given by the following equation.

Page 5 of 68

Westinghouse Non-Proprietary Class 3 a,2,,is given by the following equation.

G, is the number of generations.

For purposes of this bias evaluation, the data points of Table 1-1 and Table 1-2 are pooled into a single group. With this approach, the mean calculational methods bias, Akbias,and the mean calculational variance, , ):

o

( calculated by equations given above, are determined to be 0.00259 and (0.002882)~,respectively. The magnitude of M95/95 is obtained from Reference 13 for the total number of pooled data points, 30.

The magnitude of k95/95 is given by the following equation for SCALE 4.3 KENO analyses employing the 44-group ENDFIB-V neutron cross section library and for analyses where these experiments are a suitable basis for assessing the methods bias and calculational variance.

k ,,,,, = k,, + 0.00259 + 2.22[(0.00288)' + a~,,

Based on the above analyses, the mean calculational bias, the mean calculational variance, and the 95/95 confidence level multiplier are deduced as 0.00259, (0.00288)~,

and 2.22, respectively 1.3.3 Application to Fuel Storage Pool Calculations As noted above, the CSAS25 control module was employed to execute the functional modules within SCALE-PC. The CSAS25 control module was used to analyze either infinite arrays of single or multiple storage cells or the full spent storage pool.

Standard material compositions were employed in the SCALE-PC analyses consistent with the design input given in Section 2.0; these data are listed in Table 1-3. For fresh fuel conditions, the fuel nuclide number densities were derived within the CSAS25 module using input consistent with the data of Table 1-3. For burned fuel representations, the fuel isotopics were derived from the DIT code as described below.

Page 6 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP 1.3.4 The DIT Code The DIT (Discrete Integral Transport) code performs a heterogeneous multigroup transport calculation for an explicit representation of a fuel assembly. The neutron transport equations are solved in integral form within each pin cell. The cells retain full heterogeneity throughout the discrete integral transport calculations. The multigroup spectra are coupled between cells through the use of multigroup interface currents. The angular dependence of the neutron flux is approximated at cell boundaries by a pair of second order Legendre polynomials. Anisotropic scattering within the cells, together with the anisotropic current coupling between cells, provide an accurate representation of the flux gradients between dissimilar cells.

The multigroup cross sections are based on the Evaluated Nuclear Data File Version 6 (ENDFB-VI). Cross sections have been collapsed into an 89-group structure which is used in the assembly spectrum calculation. Following the multigroup spectrum calculation, the region-wise cross sections within each heterogeneous cell are collapsed to a few groups (usually 4 broad groups), for use in the assembly flux calculation. A B1 assembly leakage correction is performed to modify the spectrum according to the assembly in- or out-leakage. Following the flux calculation, a depletion step is performed to generate a set of region-wise isotopic concentrations at the end of a burnup interval.

An extensive set of depletion chains are available, containing 33 actinide nuclides in the thorium, uranium and plutonium chains, 171 fission products, the gadolinium, erbium and boron depletable absorbers, and all structural nuclides. The spectrum-depletion sequence of calculations is repeated over the life of the fuel assembly. Several restart capabilities provide the temperature, density, and boron concentration dependencies needed for three-dimensional calculations with full thermal-hydraulic feedback effects.

The DIT code and its cross Section library are employed in the design of initial and reload cores and have been extensively benchmarked against operating reactor history and test data.

For the purpose of spent fuel pool criticality analysis calculations, the DIT code is used to generate the detailed fuel isotopic concentrations as a function of fuel burnup and initial feed enrichment. Each complete set of fuel isotopics is reduced to a smaller set of burned fuel isotopics at specified time points after dischar e. The latter burned fuel 258 representation includes the following nuclides: 2 3 5 ~2 ,3 6 ~ ,U, 2 3 9 ~240~Pu,

, 241Pu, 149Sm, 16 0 , and 'OB. The DIT code lists the Samarium-149 isotopics for ' 4 9 ~ m and ' 4 9 D ~ m (a

metastable isomer). Since 1 4 9 ~ ism a stable isotope, the concentration of this Samarium isotope is the sum of the individual concentration of these two isomers.

The isotopic number densities from the DIT calculation are based upon pin cell averaged values. The input to KENO calculations requires that the number densities be specified for the he1 pellet. Therefore, the number densities from the DIT calculations are scaled by the ratio of area of the cell to the area of the he1 pellet for use in the KENO calculations. The concentration of 'OB supplied to KENO is such that the KENO and DIT assembly k, values (at room temperature and unborated conditions) agree to within one sigma of the KENO calculation.

Page 7 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP 1.4 Assumptions The Westinghouse OFA was modeled as the design basis fuel assembly to conservatively represent all he1 assemblies residing in the center locations of the "3x3" fuel assembly storage configurations.

The Westinghouse Standard he1 assembly was modeled as the design basis he1 assembly to conservatively represent all fuel assemblies residing in the "All-Cell" and peripheral locations of the "3x3" fuel assembly storage configurations.

Fresh Standard and OFA fuel assemblies were conservatively modeled with a UOl density equal to 10.576 glcc (96.5% of theoretical density). This translates into a pellet density equal 97.6% of theoretical density with a 1 .I% dishing (void) fraction.

All he1 assemblies, fresh and depleted, were conservatively modeled as containing solid right cylindrical pellets and uniformly enriched over the entire length of the fuel stack height. This conservative assumption bounds fuel assembly designs which incorporate lower enrichment blanket or annular pellets.

All of the Boraflex poison material residing in the storage racks is conservatively omitted for this analysis .

The intra module water gaps were conservatively modeled as 1.0 inches.

Page 8 of 68

Westinghouse Non-Proprietary Class 3 Table 1-1 Calculational Results for Cores X Through XXI of the B&W Close Proximity Experiments Core Run No. KENO La Plate spacing2 Type1 X 2348 0.996 10 f 0.00084 none 3 XI 2355 1.00049 f 0.00080 SS-304 1 XI 2359 0.99884 f 0.00077 SS-304 1 XI 2360 1.00315 f 0.0008 1 SS-304 1 XI 2361 0.9983 1 f 0.00080 SS-304 1 XI 2362 1.00060 f 0.00078 SS-304 1 XI 2363 0.99957 f 0.00078 SS-304 1 XI 2364 1.00246 f 0.00080 SS-304 1 XI1 2370 0.99990 f 0.00082 SS-304 2 XI11 2378 0.99754 f 0.00089 B/Al 1 XIIIA 2423 0.99575 f 0.00087 B/AI 1 XIV 2384 0.99465 f 0.00086 B/AI 1 XV 2388 0.99158 f 0.00084 B/AI 1 XVI 2396 0.99230 f 0.00088 B/AI 2 XVII 2402 0.99478 f 0.00079 B/Al 1 XVIII 2407 0.99440 f 0.00083 B/Al 2 XIX 241 1 0.99821 f 0.0008 1 B/Al 1 XX 2414 0.99498 f 0.00082 B/Al 2 XXI 2420 0.993 18 f 0.00094 B/AI 3

' Entry indicates metal separating unit assemblies.

Entry indicates spacing between unit assemblies in units of fuel rod pitch.

Page 9 of 68

Westinghouse Non-Proprietary Class 3 Table 1-2. Calculational Results for Selected Experimental PNL Lattices, Fuel Shipping and Storage Configurations Experiment k m Comments 043 0.99787 k 0.00106 Uniform rectangular array, no poison 044 1.00104k0.00102 045 0.99955 f 0.00101 046 0.99960 f 0.00103 06 1 0.99792 k 0.00099 2 x 2 array of rod clusters, no poison 062 0.99628 k 0.00096 064 0.99696 + 0.00103 2 x 2 array of rod clusters, 0.302 cm thick SS-304 cross 07 1 0.99970 f 0.00101 2 x 2 array of rod clusters, 0.485 cm thick SS-304 cross 079 0.99463 + 0.00102 2 x 2 array of rod clusters, cross of 0.3666 g boron/cm2 087 0.99423 f 0.00099 2 x 2 array of rod clusters, cross of 0.1639 g boron/cm2 093 0.99787 f 0.00098 2 x 2 array of rod clusters, cross of 0.1425 g boron/cm2 Page 10 of 68

Westinghouse Non-Proprietary Class 3 Table 1-3. Standard Material Compositions Employed in Criticality Analysis for Prairie Island Units 1 & 2 Spent Fuel Storage Racks Material Element Weight Fraction Zr 0.9829 Zircaloy-4, Sn 0.0140 Density = 6.56 g/cm3

@ 293.15 K Fe 0.0021 Cr 0.0010 154~d 0.0007304 Is5~d 0.0050360 4.0 w/o Gd203 156~d 0.0070440

@ 293.15 K lS7Gd 0.0054304 ls8Gd 0.0086676 I6OGd 0.0077296 160 0.0053620 SCALE Standard Composition Library Water Density = 1.O g/cm3 @ 293.15 K SCALE Standard Corn osition Library Stainless Steel  !+'

Density = 7.94 g/cm @ 293.1 5 K Fraction of Theoretical Density = 0.965 Fresh UO2 Enrichment = 4.95 w/o 2 3 5 @ ~ 293.1 5 K SCALE Standard Composition Library Regular Concrete Density = 2.3 g/cm3 @ 293.15 K Page 11 of 68

Westinghouse Non-Proprietary Class 3 2.0 Design Input This section provides a brief description of the Prairie Island Units 1 & 2 spent fbel storage racks with the objective of establishing a basis for the analytical models employed in the criticality analyses described in Section 3.0.

2.1 Design Input from NMC NMC provided Westinghouse a comprehensive package of design data related to the Prairie Island Units 1 & 2 spent fbel pools. This design input package includes the necessary data, drawings, or references required to develop the KENO models discussed herein. Specifically, it includes drawing NF-90044 which was employed to develop the KENO model for spent fbel pool #2. The nominal storage cell dimensions were obtained from drawing NF-90046 provided by NMC. Note that drawing NF-90044 contains a typographical error. Module 90047-1 1 is labeled as a 7x8 module in drawing NF-90044. It is actually a 7x7 module.

2.2 Spent Fuel Pool Storage Configuration Description There are two spent he1 pools which provide storage for Prairie Island Units 1 & 2. Spent fuel pool #1 is the small pool, and spent fbel pool #2 is the large pool. Spent fuel pool # 1 contains 9 spent fbel storage modules; there are six 7x7 modules and three 7x8 modules. Spent he1 pool #2 contains 21 spent fuel storage modules; there are seven 7x7 modules, ten 7x8 modules, and four 8x7 modules. The modules are separated by a minimum water gap of 1 inch. Spent fuel pool #2 has a liner inside dimension equal to 227 inches in the north to south direction and 521 inches in the west to east direction. The modules in spent he1 pool #2 are located 2 inches from the southwest corner. Figure 2-2 displays the arrangement of the spent fuel pool storage modules and was produced by scanning drawing NF-90044. Table 2-2 summarizes the overall geometry data for the Prairie Island Units 1 & 2 spent fuel pool #2.

2.3 Individual Storage Cell Description The nominal storage cell is centered on a pitch equal to 9.5 inches. Each storage cell consists of an inner stainless steel canister and outer stainless steel sheathing. The original Boraflex material (not modeled in this analysis) was located in the cavity between the inner canister and outer sheathing. The inner stainless steel canister has a nominal inside dimension equal to 8.27 inches and is 0.09 inches thick. The outer stainless steel sheathing has an inside dimension equal to 8.70 inches and is 0.024 inches thick.

The nominal storage rack dimensions are summarized in Table 2-1. The nominal rack dimensions are reported with manufacturing tolerances, where available. Figure 2-1 displays the Prairie Island Units 1

& 2 storage cell geometry. Figure 2-3 displays the dimensions of the individual storage cell and was produced by scanning drawing NF-90046.

Page 12 of 68

Westinghouse Non-Proprietary Class 3 Table 2-1. Prairie Island Units 1 & 2 Storage Cell Dimensions (All dimensions given in inches)

Parameter Value Nominal Cell Pitch 9.50 + 0.06 Box Wall Thickness 0.09 + 0.01 Box ID 8.27 f 0.10 Boraflex Cavity Width 8.20 Boraflex Cavity Thickness 0.125 Sheathing Thickness 0.024 Page 13 of 68

Westinghouse Non-Proprietary Class 3 Table 2-2. Prairie Island Units 1 & 2 Spent Fuel Pool #2 Dimensions (All dimensions given in inches)

Parameter Value Pool Length 227 Pool Width 52 1 Intra Module ~a~~ 1.O Wall I Module Gap in SW Corner 2.0 Wall Thickness 24

' The intra module water gap is conservatively modeled as 1 inch.

Page 14 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Figure 2-1. Prairie Island Units 1 & 2 Storage Cell SS Outer sheathing, ID equal to SS Canister, ID equal to 8.27 8.70 inches and 0.024 inches thick inches and 0.09 inches thick Page 15 of 68

Westinghouse Non-Proprietary Class 3 Figure 2-2. Prairie Island Units 1 & 2 Spent Fuel Pool Page 16 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Figure 2-3. Prairie Island Units 1 & 2 Assembly Storage Cell Page 17 of 68

Westinghouse Non-Proprietary Class 3 3.0 Analysis 3.1 KENO Models The Prairie Island Units 1 & 2 spent fuel storage racks employ two different fuel assembly storage configurations; namely the "All-Cell" and "3x3" he1 assembly storage configurations. The "3x3" fuel assembly storage configuration is analyzed with and without credit for Gd203 burnable absorbers. The purpose of this section is to describe the models employed in KENO to represent these assembly storage configurations and spent fuel pool #2.

3.1.1 KENO Model for the "All-Cell" Fuel Assembly Storage Configuration An "All-Cell" fuel assembly storage configuration is modeled in KENO as an infinitely repeating storage cell that contains either a fresh or depleted fuel assembly. An inner stainless steel canister controls the fuel assembly position.

Each cell location is modeled in KENO as a square cell with a pitch equal to 9.50 inches.

The inner stainless steel canister is modeled with an inside dimension equal to 8.27 inches and is 0.09 inches thick. The outer stainless steel sheathing is modeled with an inside dimension equal to 8.70 inches and is 0.024 inches thick. The cavity between the canister and outer sheathing is modeled with water. All of these dimensions employed to model the Prairie Island Units 1 & 2 storage cell are consistent with the values given in Table 2- 1.

The fuel assembly, inner stainless steel canister, and outer stainless steel sheathing are modeled in KENO as 144 inches tall. Reflective boundary conditions are applied to the X and Y surfaces of the assembly, thus simulating an infinitely repeating array. A two-foot water reflector is modeled above and below the storage cell geometry. The pool water is simulated to be full density (1 g/cm3) at room temperature (68 O F ) . The top and bottom surfaces of the water reflector have reflected boundary conditions.

The fhel assembly modeled in KENO represents the Westinghouse 14x14 Standard design. Note that the fuel pellets in a fuel rod are modeled as a fully enriched right solid cylinder that is 144 inches tall. This assumption conservatively bounds fuel rod designs that incorporate annular and/or lower enrichment fuel pellets such as those employed for axial blankets. A top down image of a KENO produced plot of a single "All-Cell" he1 assembly storage configuration is shown in Figure 3-4.

3.1.2 KENO Model for the "3x3" Fuel Assembly Storage Configuration The "3x3" fuel assembly storage configuration is modeled in KENO as a repeating 3x3 array with a fresh fuel assembly occupying the center location of the array and the remaining locations are occupied by discharged fuel assemblies. This storage configuration is analyzed with and without credit for Gd203 burnable absorbers. An inner stainless steel canister controls each fuel assembly position within the array.

Page 18 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Each of the nine storage cell locations is modeled in KENO as a square cell with a pitch equal to 9.50 inches. The inner stainless steel canister is modeled with an inside dimension equal to 8.27 inches and is 0.09 inches thick. The outer stainless steel sheathing is modeled with an inside dimension equal to 8.70 inches and is 0.024 inches thick. The cavity between the canister and outer sheathing is modeled with water. All of these dimensions employed to model the Prairie Island Units 1 & 2 storage cell are consistent with the values given in Table 2-1.

The fuel assembly, inner stainless steel canister, and outer stainless steel sheathing are modeled in KENO as 144 inches tall. Reflective boundary conditions are applied to the X and Y surfaces of the 3x3 array, thus simulating an infinitely repeating "3x3" fuel assembly storage configuration. A two-foot water reflector is modeled above and below the storage cell geometry. The pool water is simulated to be full density (1 g/cm3) at room temperature (68 OF). The top and bottom surfaces of the water reflector have reflected boundary conditions.

The center he1 assembly that is modeled in KENO represents the Westinghouse 14x14 OFA design. The enrichment of all fuel pellets is equal to 4.95 w/o 2 3 5 (with

~ no Gd2O3 credit) and the pellet density is equal to 96.5% of theoretical density. The remaining &el assemblies that are modeled by KENO represent the Westinghouse 14x14 Standard design. Note that the fuel pellets in a fuel rod are modeled as fully enriched right solid cylinders that are 144 inches tall. This assumption conservatively bounds fuel rod designs which incorporate annular and/or lower enrichment fuel pellets such as those employed for axial blankets. A top down image of a KENO produced plot of a single "3x3" fuel assembly storage configuration is shown in Figure 3-5.

Storage of fresh fuel assemblies with Gd2O3burnable absorbers in the center location of the 3x3 array allow for storage of more reactive fuel assemblies on the periphery than is allowed by the configuration described above. Gd203 credit accounts for the reactivity decrease associated with the addition of a neutron poison material. The following assumptions are used to represent the Gd2O3 pellets in the KENO model of the 3x3 storage region.

A 6 inch burnable absorber cutback (top and bottom) is used. This produces a 132 inch shimmed length that is centered about the active fuel height.

The Gd2O3amount is limited to four fuel pins at a concentration of 4.0 w/o Gd203 in Gd203-U02.The pin placement is shown in Figure 3-2.

The 2 3 5 enrichment

~ is reduced to 4.0 w/o in the shimmed portion of the fuel pin for fuel temperature considerations.

The 2 3 5 ~enrichment in the blanket region of the shimmed fuel pins is also reduced to 4.0 w/o.

The density of the U02 and Gd2O3mixture is found with the following empirical expression (Reference 18),

Page 19 of 68

Westinghouse Non-Proprietary Class 3 where, pII+Gd = density of UO, and Gd,03 mixture pUlh= theoretical UO, density X = Gd,03 concentration in weight percentage The calculation performed for this analysis is as follows, pUth = 10.5764 g cm" (96.5% T.D.) and X = 4.0 wlo, This value is utilized in the "3x3" storage configuration KENO models with GdzO3 credit.

3.1.3 KENO Model for Entire Spent Fuel Pool There is a relatively large amount of leakage in the Prairie Island spent fuel pool #1 (the small pool), therefore only spent k e l pool #2 (the large pool) need be modeled for conservatism. Spent fuel pool #2 is modeled in KENO as a rectangular water cell that is 521 inches in the west to east direction and 227 inches in the north to south direction. The floor and sides of the spent he1 pool are modeled by surrounding the rectangular water cell with two feet of concrete on the bottom and sides.

Twenty one (21) fuel storage modules are inside the spent fuel pool #2 rectangular water cell. The k e l storage modules vary in size from a 7x7 to a 7x818~7array of storage cells.

All of the individual assembly storage cells were modeled exactly the same and as described in Sections 3.1.1 through 3.1.2. The minimum intra module water gap of 1.0 inch was modeled conservatively. The fuel storage rack modules are placed within 2.0 inches fiom the southwest corner of the spent fuel pool liner. Note that a 2 inch gap of water between the modules and pool wall is maintained on the south and west faces and the intra module water gap shown by section A-A in Figure 2-2 is modeled as 9.75 inches wide. These pool dimensions are shown in Table 2-2. The pool water was modeled at room temperature conditions, 68 O F , and as full density (1.0 glcc).

The storage modules are modeled with both the "All-Cell" and "3x3" storage configurations. Figures 3-6 and 3-7 show KENO produced plots of the spent fuel pool loaded with these storage configurations. These arrangements conform to the restrictions outlined in sections 3.1.1 and 3.1.2. No Gd203burnable absorber credit is modeled in this portion of the analysis.

3.2 Design Basis Fuel Assembly Prairie Island Units 1 & 2 have been in operation for many years and during that time interval a variety of reload batches containing different fuel assembly designs have been cycled through the reactors. Thus, the criticality safety analysis of their spent fuel pool Page 20 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP must take into account possible differences in the reactivity characteristics of the different assembly types. For purposes of this analysis, the different types of fuel assemblies were surveyed so as to define a reference design fuel assembly that would assure conservative results for the analysis.

Table 3-1 provides the relevant dimensions employed to model the Westinghouse 14x14 Standard and Westinghouse 14x14 OFA fuel assemblies in the spent fuel pool environment. Figure 3-1 displays the Westinghouse 14x14 fuel assembly with both the OFA and STD parameters. Based on the results of scoping calculations for the 2 3 5 ~

loading and storage configuration considered here, the most reactive fresh fuel assembly design is the Westinghouse 14x14 OFA fuel assembly for the center location of the "3x3" fuel assembly storage configuration. The Westinghouse Standard fuel assembly design was modeled as the design basis fuel assembly to conservatively represent discharged fuel assemblies residing in the "All-Cell" and peripheral locations of the "3x3" fuel assembly storage configurations. Other fuel assembly designs are found to be less reactive in these fuel assembly storage configurations than the design basis fuel assemblies.

The unshimmed design basis fuel assemblies are modeled with the maximum enrichment over the active fuel length. The fresh fuel pellets in a fuel rod are modeled as a solid right cylinder with a UO2 density equal to 10.576 glcc (96.5% of theoretical density). No credit is taken for the nominal 1.1 to 1.2 void fraction percentages that are associated with dishing or chamfering. In addition, no credit is taken for any natural or reduced enrichment pellets. These assumptions result in equivalent or conservative calculations of reactivity for all fuel assemblies used at Prairie Island Units 1 & 2, including those with annular pellets or lower enrichment pellets at the ends of the fuel rods. No credit is taken for any spacer grids or sleeves.

The shimmed fuel assemblies are of the Westinghouse OFA design and incorporate the design features outlined above in section 3.1.2.

3.3 Modeling of Axial Burnup Distributions A key aspect of the burnup credit methodology employed in this analysis is the inclusion of an axial burnup profile correlated with feed enrichment and discharge burnup of the burned fuel assemblies. This effect is important in the analysis of the spent fuel pool characteristics since the majority of spent fuel assemblies stored in the pool have a discharge burnup well beyond the limit for which the assumption of a uniform axial burnup shape is conservative. Therefore, it is necessary to represent the burnt fuel assembly with a representative axial burnup profile.

For any given spent fuel assembly, the fuel burnup is a continuous fbnction of axial position. However, from a computational point of view, this function can be discretized in such a manner that the axial "end-effect" is adequately captured. It is often common practice to divide the fuel assembly into several axial zones with each zone assumed to be uniform in burnup. Moreover, it is required that the size of the top and bottom axial zones be small (typically less than 8 inches) so as to capture the steep burnup gradient with axial position while that of the central zone may be larger. In spent he1 pool calculations, Page 21 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP an eight-zone axial model is found to be adequate (Reference 19) to represent the spent fuel assembly. Such an eight-zone model would have seven zones with fine mesh spacing (four at the top of the fuel assembly and three at the bottom) and the remaining zone represents the center portion of the fuel assembly. Figure 3-3 provides a pictorial view of the axial zones employed in the eight-zone axial model.

The individual power fractions of each zone are so modeled that they give the same volume averaged burnup when compared to a uniform burnup model. This model is validated due to the fact that the relative contribution of the bottom zones of the fuel assembly to the k,ff value is negligible.

Input to this analysis is based on the limiting axial burnup profile data provided in the DOE Topical Report, as documented in Reference 14. The burnup profile in the DOE Topical Report is based on a database of 3169 axial-burnup profiles for PWR fuel assemblies compiled by Yankee Atomic. This profile is derived from the burnups calculated by utilities or vendors based on core-follow calculations and in-core measurement data. The axial burnup profile in the DOE report is based on the most limiting axial burnup shape found in the database. The eight-zone model is constructed based on this limiting axial burnup profile.

DIT was used to generate the isotopic concentrations for each segment of the axial profile. Table 3-2 lists the fuel and moderator temperatures employed in the spectral calculations for each node of the eight-zone axial burnup model. These values are based on mid-cycle temperature profiles for Prairie Island Units 1 and 2. The he1 temperatures for each axial zone are calculated based on a representative he1 temperature correlation while the moderator temperatures are based on a linear relationship with axial position.

These node dependent moderator and fuel temperature data and power profile data were employed in DIT to deplete the fuel to the desired burnup for each initial enrichment and axial zone. The values of assembly average burnups versus feed enrichment for which burned fuel assemblies were simulated are tabulated in Table 3-3.

A constant soluble boron concentration of 800 ppm was employed in all the burnup steps.

This value is representative of a cycle average soluble boron concentration in the core.

For the purpose of extracting the number densities, the DIT computer code was executed in two modes. First, a normal depletion was continued in steps of 1000 MWDIMTU (with respect to the assembly average case) until the desired burnup was reached. Then a restart is performed at cold, spent he1 pool conditions and the he1 assembly is allowed to decay for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />. At this point of time, the reactivity of the burned he1 assembly is at its highest. The k, and the isotopic number densities are then extracted for the KENO model development at these assembly conditions.

The DIT computed isotopic concentrations were transferred into the KENO models of the storage cells using a limited set of isotopes. That is, the 2 3 5 ~23gu,

, 236U, 239pu, 240pu, 2 4 1 ~160,

~ ,and equilibrium ' 4 9 ~ mat shutdown are represented explicitly in the KENO models. All other fission product isotopic number densities are represented by an equivalent 'OB concentration; the magnitude of this concentration is determined by matching the DIT bffvalue with the KENO keffvalue to a one sigma tolerance level.

Page 22 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Reference 19 contains a listing of the isotopic number densities employed in the KENO calculations. The format of the listing is compatible with the KENO input description and can directly be used as part of KENO input for material specification. The isotopic number densities are listed for the combination of initial enrichment and burnup listed in Table 3-3. The listing is for the Westinghouse 14x14 Standard fuel assembly design.

Reference 19 also contains a listing of the 'OB number densities determined by matching the DIT kefland KENO calculated kffvalues. The 'OB number density, the DIT calculated and the KENO calculated kR, for the eight-zone axial model (and the average fuel assembly model)' are listed in each table. The first four tables contain these values for 3.0 W/O,the next four tables contain the data for 4.0 w/o, and the final four tables contain data for 5.0 w/o.

3.4 Tolerance 1 Uncertainty Calculations Previous sections described the storage racks and fuel assembly storage configurations within the spent fuel pool and the KENO models employed to represent repeating arrays of these fuel assembly storage configurations. In addition, the method of modeling the axial profiles of fuel assembly burnup, moderator temperature, and he1 temperature were discussed.

Using the above input, analytic models were developed to perform the quantitative evaluations necessary to demonstrate that the effective multiplication factor for the spent fuel pool is less than 0.995 with zero soluble boron present in the pool water. Applicable biases to be factored into this evaluation are: (1) the methodology bias deduced fiom the validation analyses of pertinent critical experiments, and (2) any reactivity bias, relative to the reference analysis conditions, associated with operation of the spent fuel pool over a temperature range of 50 OF to 150 O F (from Reference 20).

A second allowance is based on a 95/95 confidence level assessment of tolerances and uncertainties; included in the summation of variances are the following.

(a) the 95/95 confidence level methods variance, (b) the 95/95 confidence level calculational uncertainty, (c) fuel rod manufacturing tolerances, (d) storage rack fabrication tolerances, (e) tolerances due to positioning the fuel assembly in the storage cell.

(f) burnup uncertainty (g) burnable absorber concentration (if applicable)

Items a) and b) are based on the calculational methods validation analyses. For Item c),

the fuel rod manufacturing tolerance for the reference design fuel assembly is assumed to consist of two components; an increase in fuel enrichment equal to 0.05 w/o 2 3 5 and ~ an Page 23 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP increase in pellet density from 96.5 to 98.5% of theoretical density; the individual contributions of each change are combined by taking the square root of the sum of the squares of each component. There is no allowance for dishing and chamfer and therefore the pellet density conservatively represents the stack density of the UO2 pellets in the fuel rod.

For item d), the following uncertainty components were evaluated. The inner stainless steel canister ID was increased from 8.27 inches to 8.37 inches and the thickness of the canister was decreased from 0.09 inches to 0.08 inches. The storage cell pitch for the "All-Cell" and "3x3" fuel assembly storage configurations was decreased fiom 9.50 inches to 9.44 inches.

In the case of the tolerance due to positioning of the fuel assembly in the storage cells (item e), all nominal calculations are carried out with fuel assemblies conservatively centered in the storage cells. One case was run to investigate the effect of off-center position of the fuel assemblies for each of the fuel assembly storage configurations.

These cases positioned the assemblies as close as possible in four adjacent storage cells.

Eccentric positioning has a slightly positive reactivity effect for all of the fuel assembly storage configurations.

For item f), a 5% burnup uncertainty is included. The 5% burnup uncertainty is applied to the fuel assembly storage configurations that contain depleted fuel assemblies.

For item g), the nominal gadolinia concentration is equal to 4.0 wt %. The tolerance analyzed for the gadolinia concentration is equal to -0.2 wt %.

Table 3-4, Table 3-5, and Table 3-6 provide a summary of the KENO results used in the calculation of biases and uncertainties for the "All-Cell", "Unshimmed 3x3", and "Shimmed 3x3" fuel assembly storage configurations, respectively. The total biases and uncertainties for these fuel assembly storage configurations are 0.02678, 0.02403, and 0.028 16 Akffunits respectively.

3.5 No Soluble Boron 95/95 kffCalculational Results The purpose of the following five subsections is to present the KENO calculated multiplication factors for the "All-Cell" and "3x3" fuel assembly storage configurations along with the result for the entire spent fuel pool at the zero soluble boron condition.

Due to the burnup requirements for storage in these configurations, 24 1Pu decay and 24 1 Am production burnup credit is included. The concentrations for 2 4 1 are ~ ~ decayed using the equation below and a half life, tin, value of 14.4 years.

- -(In 2 ) I n = n , .e 'X The production rate for 2 4 1 ~ ismequal to the rate of 2 4 1 decay,~ ~ using an initial 2 4 ' ~ m concentration, no, of zero. The decay time, t, extends 20 years in intervals of 5 years.

Page 24 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP 3.5.1 "All-Cell" Fuel Assembly Storage Configuration As described in Section 3.1.1, the "All-Cell" fuel assembly storage configuration consists of an infinitely repeating storage cell that contains either fresh or depleted fuel assemblies. The he1 assembly modeled in this analysis is the Westinghouse Standard fuel assembly design.

k , was

~ evaluated for an infinite array of "All-Cell" storage locations over a range of initial enrichment values up to 5.0 w/o 2 3 5 ~and assembly average burnups up to 45.0 GWDIT. These calculations were performed at 68 OF, with maximum water density equal to 1.0 glcc, to maximize the array reactivity. KENO calculations were performed for this fuel assembly storage configuration with an axially distributed burnup profile. The relative axial burnup profile employed for these calculations is discussed in Section 3.3.

These resulting KENO calculated bffdata are then employed to determine the burnup versus initial enrichment limits for a target bffvalue at zero soluble boron. The target value of k,ff is selected to be less than 0.995 by an amount sufficient to cover the magnitude of the analytical biases and uncertainties in these analyses. From Table 3-4, the sum of the biases and uncertainties is equal to 0.02678. Therefore, the target bflvalue for the "All-Cell" fuel assembly storage configuration is equal to 0.96822 (0.995-0.02678).

Table 3-7 lists the KENO calculated btrvalues for the "All-Cell" fuel assembly storage configuration versus initial enrichment and he1 assembly average burnup for an axially distributed burnup profile. The first entry in each of these tables lists the initial enrichment for no assembly burnup. Based upon the target bffvalue, the interpolated enrichment for no assembly burnup is e ual to 1.79 w/o 2 3 5 ~The . derived burnup limits, for enrichments greater than 1.79 w/o'~~U, are based upon the KENO calculated bn values for 3.0, 4.0, and 5.0 wlo 2 3 5 ~ .For each of these enrichments, KENO calculations were performed at three assembly average burnup values for an axially distributed burnup profile. A second degree fit of the burnup versus bffdata was then employed to determine the burnup required to meet the target bffvalue of 0.96822. The resulting assembly burnup versus initial enrichment storage limits are provided in Table 3-10. The first entry in these tables lists the initial enrichment, 1.79 w/o 2 3 5 ~for , fuel assemblies at zero burnup. The data in this table is plotted in Figure 4-5. The required assembly burnups as a function of initial enrichment were fitted to third degree polynomials. These polynomials are given in Table 4-1 and will be used to determine the burnup as a function of initial enrichment.

3.5.2 "3x3" Fuel Assembly Storage Configuration As described in Section 3.1.2, the "3x3" fuel assembly storage configuration consists of a repeating 3x3 array with a fresh fuel assembly occupying the center location of the array and the remaining locations are occupied by discharged assemblies. The center assembly is the Westinghouse OFA design and the peripheral assemblies are the Westinghouse Standard design. The unshimmed case contains no Gd2O3 burnable absorbers, and the shimmed case contains four Gd203 burnable absorber pins at a concentration of 4.0 w/o.

Page 25 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP keff was evaluated for an infinite array of "Unshimmed 3x3" storage locations over a range of initial enrichment values up to 5.0 w/o 2 3 5 and

~ assembly average burnups up to 55.0 GWD/T. These calculations were performed at 68 OF, with maximum water density equal to 1.0 g/cc, to maximize the array reactivity. KENO calculations were performed for this fuel assembly storage configuration with an axially distributed burnup profile.

The relative axial burnup profile employed for these calculations is discussed in Section 3.3. These resulting KENO calculated bffdata are then employed to determine the burnup versus initial enrichment limits for a target bffvalue at zero soluble boron. The target value of keff is selected to be less than 0.995 by an amount sufficient to cover the magnitude of the analytical biases and uncertainties in these analyses. From Table 3-5, the sum of the biases and uncertainties is equal to 0.02403. Therefore, the target bffvalue for the "Unshimmed 3x3" fuel assembly storage configuration is equal to 0.97097 (0.995-0.02403).

Table 3-8 lists the KENO calculated keffvalues for the "Unshimmed 3x3" fuel assembly storage configuration versus initial enrichment and fuel assembly average burnup for an axially distributed burnup profile. The first entry in these tables lists the initial enrichment for no assembly burnup. Based upon the tar et bffvalue, the interpolated enrichment for no assembly burnup is e ual to 1.30 w/o 23qU.The derived burnup limits, for enrichments greater than 1.30 W/O"~U, are based upon the KENO calculated k,a values for 3.0, 4.0, and 5.0 w/o 2 3 5 ~ .For each of these enrichments, KENO calculations were performed at three assembly average burnup values with an axially distributed burnup profile. A second degree fit of the burnup versus keffdata was then employed to determine the burnup required to meet the target kffvalue equal to 0.97097. The resulting assembly burnup versus initial enrichment storage limits are provided in Table 3-1 1. The first entry in these tables lists the initial enrichment, 1.30 w/o 2 3 5 ~for

, fuel assemblies at zero burnup. The data in this table is plotted in Figure 4-6. The required assembly burnups as a fknction of initial enrichment were fitted to third degree polynomials. These polynomials are given in Table 4-2 and will be used to determine the burnup as a function of initial enrichment.

keffwas also evaluated for an infinite array of "Shimmed 3x3" storage locations over a range of initial enrichment values up to 5.0 w/o 2 3 5 and~ assembly average burnups up to 45.0 GWD/T. These calculations were performed at 68 O F , with maximum water density equal to 1.0 g/cc, to maximize the array reactivity. KENO calculations were performed for this fuel assembly storage configuration with an axially distributed burnup profile.

The relative axial burnup profile employed for these calculations is discussed in Section 3.3. These resulting KENO calculated keff data are then employed to determine the burnup versus initial enrichment limits for a target bffvalue at zero soluble boron. The target value of keff is selected to be less than 0.995 by an amount sufficient to cover the magnitude of the analytical biases and uncertainties in these analyses. From Table 3-6, the sum of the biases and uncertainties is equal to 0.02816. Therefore, the target bffvalue for the "shimmed 3x3" fuel assembly storage configuration is equal to 0.96684 (0.995-0.02816).

Table 3-9 lists the KENO calculated bffvalues for the "Shimmed 3x3" fuel assembly storage configuration versus initial enrichment and &el assembly average burnup for both a uniform and axially distributed burnup profile. The first entry in these tables lists Page 26 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP the initial enrichment for no assembly burnup. Based upon the target bffvalue, the interpolated enrichment for no assembly burnup is equal to 1.39 w/o 2 3 5 ~The . derived burnup limits, for enrichments greater than 1.39 w/o 2 3 5 ~are , based upon the KENO calculated k,ffvalues for 3.0,4.0, and 5.0 w/o 2 3 5 ~For

. each of these enrichments, KENO calculations were performed at three assembly average bumup values for an axially distributed burnup profile. A second degree fit of the burnup versus kffdata was then employed to determine the burnup required to meet the target kffvalue equal to 0.96684.

The resulting assembly burnup versus initial enrichment storage limits are provided in Table 3-12. The first entry in these tables lists the initial enrichment, 1.39 w/o 2 3 5 ~for fuel assemblies at zero burnup. The data in this table is plotted in Figure 4-7. The required assembly burnups as a function of initial enrichment were fitted to third degree polynomials. These polynomials are given in Table 4-3 and will be used to determine the burnup as a function of initial enrichment.

3.5.3 Entire Spent Fuel Pool KENO models for the entire Prairie Island spent he1 pool #2 were constructed for this analysis and are shown in Figures 3-6 and 3-7. Figure 3-6 displays the KENO model for spent fuel #2, based upon the "All-Cell" storage configuration, with the 2 inch wall gap maintained on the south and west sides of spent fuel pool #2. Figures 3-7 illustrate the same KENO models based upon the "Unshimmed 3x3" storage configuration. These spent fuel pool KENO models are described in section 3.1.3. The largest KENO calculated multiplication factors for the spent he1 pool models and the respective infinite array models are shown in Table 3-13, and are based upon no soluble boron. The differences in the infinite array and spent fuel pool model's bffvalues are attributed to neutron leakage from the spent fuel #2 model. The biases and uncertainties, from Table 3-4 and Table 3-5, were added to the spent fuel pool multiplication factors and the results are shown in Table 3-13. As can be seen from Table 3-13, the final kg5195 values at zero soluble for spent he1 pool #2 are all below the design basis limit equal to 0.995 at zero soluble boron.

The interface between the "All-Cell" and "3x3" storage configurations was directly simulated in a KENO model for spent fuel pool #2. The interface modeled is depicted in Figure 4-4. Note that the KENO calculated multiplication factor for this interface model is 0.96346 +/- 0.00038. This value is less than the value given in Table 3-13 for the "3x3" storage configuration. Therefore, the interface configuration (with biases and uncertainties) also meets the design basis limit equal to 0.995 at zero soluble boron.

3.6 Soluble Boron The NRC Safety Evaluation Report (SER) for WCAP-14416-P is given in Reference 3; page 9 of the enclosure to Reference 3 defines the soluble boron requirement as follows.

The total soluble boron credit requirement is defined as the sum of three quantities.

SBC,, ,,, = SBC,,,,, + SBCm + SBC, Page 27 of 68

Westinghouse Non-Proprietary Class 3

where, SBC,,,,, is the total soluble boron credit requirement,(ppm),

SBC,,,,, is the soluble boron requirement for 95/95 bffless than or equal to 0.95, (pprn),

SBC, is the soluble boron required for burnup and reactivity uncertainties, (pprn),

SBC, is the soluble boron required for bffless than or equal to 0.95 under accident conditions, (pprn).

Each of these terms will be discussed in the following subsections.

3.6.1 Soluble Boron Requirement to Maintain knLess Than or Equal to 0.95 Table 3-14 contains the KENO calculated keff values for the Prairie Island Units 1 & 2 spent he1 pool #2 from 0 to 600 pprn of soluble boron, in increments of 200 ppm. These KENO models assume that the pool is filled with the geometries and storage configurations outlined in section 3.1.3. The reactivity worth, A b f f , of the soluble boron was determined by subtracting the bffvalue, for a given soluble boron concentration, from the keff value for zero soluble boron. The soluble boron concentration and reactivity worth data was then fitted to a second degree polynomial, the limiting of which is shown on the bottom of Table 3-14. This polynomial was then employed to determine the amount of soluble boron required to reduce bffby 0.05 Akeff units, which is 276 ppm.

3.6.2 Soluble Boron Requirement for Burnup and Reactivity Uncertainties The soluble boron credit, in units of ppm, required for reactivity uncertainties was determined by converting the uncertainty in he1 assembly reactivity and the uncertainty in absolute fuel assembly burnup values to a soluble boron concentration, in units of ppm, necessary to compensate for these two uncertainties. The first term, uncertainty in he1 assembly reactivity, is calculated by employing a depletion reactivity uncertainty equal to 0.010 Aker units per 30,000 M W I M T U of assembly burnup (obtained from Reference

3) and multiplying by the maximum amount of assembly burnup credited in a storage region analysis. For this analysis, the maximum amount of assembly burnup credited is 52,400 MWDIMTU (for the "Unshimmed 3x3" storage configuration). Therefore, the depletion reactivity uncertainty is 0.017467 Abff.

The uncertainty in absolute fuel assembly burnup values is conservatively calculated as 5% of the maximum be1 assembly burnup credited in a storage region analysis. The maximum he1 assembly burnup credited in the storage configurations considered here, the uncertainty in these burnup values, and the corresponding reactivity values are given in Table 3-15. The reactivity associated with a change in burnup of 2,250 M W M T U at 45,000 M W N T U for the "All-Cell" storage region was conservatively calculated to be 0.0 1016 Akeff units.

Page 28 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP The total of these two reactivity effects is equal to 0.027627 (0.017467 + 0.01016) Abff units. The soluble boron concentration (pprn) necessary to compensate for this reactivity is calculated to be 145 ppm. A value of 183 pprn is conservatively chosen to be used.

3.6.3 Soluble Boron Required to Mitigate Accidents The soluble boron concentration, in units of ppm, required to maintain keffless than or equal to 0.95 under accident conditions is determined by first surveying all possible events which increase the k , value

~ of the spent fuel pool. The accident event which produced the largest increase in spent fuel pool bffvalue is employed to determine the required soluble boron concentration necessary to mitigate this and all less severe accident events. The list of accident cases considered include:

Dropped fresh fuel assembly on top of the storage racks, Misloaded fresh fuel assembly into incorrect storage rack location, Misloaded fresh fuel assembly between storage racks (in gap between storage racks),

Intramodule water gap reduction due to seismic event, Spent fuel pool temperature greater than 150 OF.

It is possible to drop a fresh fuel assembly on top of the spent fuel pool storage racks. In this case the physical separation between the fuel assemblies in the spent fuel pool storage racks and the assembly lying on top of the racks is sufficient to neutronically decouple the accident. In other words, dropping the fresh fuel assembly on top of the storage racks will only produce a very small positive reactivity increase. This very small positive reactivity increase will not be as limiting as the reactivity increase associated with fuel mishandling events.

Several h e l mishandling events were simulated with KENO to assess the possible increase in the bffvalue of the Prairie Island Units 1 & 2 spent fuel pool #2. The fuel mishandling events all assumed that a fresh Westinghouse OFA he1 assembly enriched to 4.95 w/o 2 3 5 (and

~ no burnable poisons) was misloaded into the described area of the spent fuel pool. These cases were simulated with the KENO model for spent fuel pool #2.

These cases involved placing a fresh fuel assembly either inside a storage location intended for a burned fuel assembly or inside the gap of water between the storage modules in the southwest corner of spent fuel pool #2. The results of these KENO cases are contained in Table 3-16 which indicates that the highest increase in reactivity occurred when a fresh fuel assembly was placed in the gap of water between storage modules and next to another fresh fuel assembly. The reactivity increase associated with this accident was calculated to be 0.05914 A h f f units. The amount of soluble boron necessary to mitigate the consequence of this accident was determined to be 263 pprn by performing a KENO case for the same accident at 300 pprn and linear interpolation of the soluble boron for a reduction of 0.05914 Abff units.

For the accident due to a seismic event the intramodule water gap is reduced to zero and each storage module makes contact. Based upon the comparison of the keffvalues for the Page 29 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP entire spent fuel pool and infinite arrays (see Table 3-13) the reactivity associated with this accident is approximately 0.01 1 Ahff units, and therefore not as limiting as the fuel mishandling events discussed above.

For the change in spent fuel pool water temperature accident, a temperature range of 150 F to 240 F was considered. From Reference 20, the maximum reactivity increase occurred for the "All-Cell" storage configuration and was calculated to be 0.01 729 A h f f units. This reactivity increase is far less limiting than the reactivity increase associated with the fuel mishandling events discussed above.

3.6.4 Total Soluble Boron Requirement Soluble boron in the spent fuel pool coolant is used in this criticality safety analysis to offset the reactivity allowances for calculational uncertainties in modeling, storage rack fabrication tolerances, fuel assembly design tolerances, and postulated accidents. The total soluble boron requirement is defined above.

The magnitude of each soluble boron requirement is shown below.

SBC,, ,,, = 276 pprn SBC, = 183ppm SBC, = 263 pprn SBC,,,,, = 722 pprn Therefore, a total of 722 pprn of soluble boron is required to maintain hffless than or equal to 0.95 (including all biases and uncertainties) assuming the most limiting single accident. Note that these soluble boron concentrations assumes an atomic fraction for 'OB equal to 0.199. For a 'OB isotopic fraction equal to 0.197, the soluble boron concentrations, required to maintain the same concentration of 'OB atoms, would be calculated as below.

SBC,,,,, = 279 pprn SBC, = 185ppm SBC, = 266 pprn SBC,,,, = 730 pprn Thus a recommended soluble boron level of 730 pprn is sufficient to accommodate all the design requirements.

Page 30 of 68

Westinghouse Non-Proprietary Class 3 Table 3-1. Summary of Fuel Assembly Characteristics (from Reference 20)

Instrument Tube ID

• Note that 0.3669 inches was conservatively employed to represent this pellet diameter

• • Note that the clad material was conservatively modeled as Zr-4.

ZIRLOTMtrademark property of Westinghouse Electric Company LLC.

Page 31 of 68

Westinghouse Non-Proprietary Class 3 Table 3-2. Relative Power, Fuel, and Moderator Temperatures for Eight Zone Model Zone No. Height (in.) Relative Power Fuel Moderator Temperature Temperature (OF) (OF) 1 6.15 0.488 99 1.022 544.190 2 6.15 0.813 1101.020 545.018 3 6.15 1.003 1211.018 545.360 4 107.1 1.092 1218.956 574.034 5 6.15 0.936 1138.010 603.860 6 3.075 0.841 1085.522 604.526 7 6.15 0.624 980.528 605.741 8 3.075 0.297 875.516 606.488 Page 32 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Table 3-3. Burnup and Initial Enrichment Combinations Used to Determine the Isotopic Number Densities Page 33 of 68

Westinghouse Non-Proprietary Class 3 Table 3-4. kff for the Various Physical Tolerance Cases for the "All-Cell" Storage Configuration Case Description kff Akm 1.80 w/o Nominal case4 0.97157 f 0.00033 4.95 w/o Nominal case5 1.23265 f 0.00038 Increase in 2 3 5 Enrichment

~ 1.23368 f 0.00038 0.00 179 Increase in Stack Density 1.23299 f 0.00038 0.001 10 Decrease in Cell Pitch 0.97962 f 0.00034 0.00872 Decrease in Rack Thickness +

0.97769 0.00033 0.00678 Decrease in Rack ID 0.97364 f 0.00034 0.00274 Off-Center Assembly Positioning 0.97703 f 0.00033 0.00612 Burnup Uncertainty 0.01016 Methodology uncertainty6 0.00646 Statistical Sum of Uncertainties 0.01779 Methodology Bias7 0.00259 Pool Temperature Bias8 0.00640 Sum of Uncertainties and Biases 0.02678

' Note the 1.80 wlo nominal KENO case for the All Cell storage contains STD fuel at the fresh enrichment of 1.80 "1, "'u.

Note the 4.95 wlo nominal KENO case for the All Cell storage contains STD fuel at the fresh enrichment of 4.95 "I, 2 3 5 ~ .

" See page 11 for definition of methodology uncertainty Methodology bias or the mean calculational methods bias is evaluated to be 0.00259.

Pool temperature bias obtained from Reference 20.

Page 34 of 68

Westinghouse Non-Proprietary Class 3 Table 3-5. bfffor the Various Physical Tolerance Cases for the Unshimmed "3x3" Storage Configuration Case Description 4ff Akm 1.20 w/o Nominal case9 0.96471 f 0.00036 4.95 w/o Nominal case" 1.23181 f 0.00037 Increase in 2 3 5 Enrichment

~ 1.23350 f 0.00038 0.00244 Increase in Stack Density 1.23243 f 0.00040 0.00139 Decrease in Cell Pitch 0.96903 f 0.00035 0.00503 Decrease in Rack Thickness 0.96752 f.0.00036 0.00353 Increase in Rack ID 0.96498 f 0.00037 0.00 100 Off-Center Assembly Positioning 0.97372 f 0.00036 0.00973 Burnup Uncertainty 0.00658 Methodology ~ n c e r t a i n t ~ " 0.00646 Statistical Sum of Uncertainties 0.01504 Methodology ~ i a s ' ~ 0.00259 Pool Temperature ~ i a s ' ~ 0.00640 Sum of Uncertainties and Biases 0.02403

" Note the 1.20 wlo nom~nalKENO case for the 3x3 storage contains OFA fuel at the fresh enrichment of 4.95 " I , 13'u,which is surrounded by a ring of STD fuel at the fresh enrichment of 1.20 "I, "'u.

"' Note the 4.95 wlo nominal KENO case for the 3x3 storage contains OFA fuel at the fresh enrichment of 4.95 w/O13'u,which is surrounded by a ring of STD fuel at the fresh enrichment of 4.95 "1, "'u.

See page 11 for definition of methodology uncertainty.

l 2 Methodology bias or the mean calculational methods bias is evaluated to be 0.00259

" Pool temperature bias obtained from Reference 20.

Page 35 of 68

Westinghouse Non-Proprietary Class 3 Table 3-6. kerr for the Various Physical Tolerance Cases for the Shimmed "3x3" Storage Configuration Case Description kern Akfi 1.50 w/o Nominal casei4 0.976 19 f 0.00034 4.95 w/o Nominal casei5 1.22695 f 0.00039 Increase in 2 3 5 Enrichment

~ 1.22923 f 0.00039 0.00306 Increase in Stack Density 1.22880 f 0.00039 0.00263 Decrease in Cell Pitch 0.98347 f 0.00035 0.00797 1 Decrease in Rack Thickness / 0.98016 k 0.00035 / 0.00466 I Increase in Rack ID 0.97704 f 0.00035 0.00154 I Off-Center Assembly Positioning 1 0.98483 f 0.00035 1 0.00933 I Decrease in Gd2O3Concentration 0.97588 f 0.00035 0.00038 I Burnup Uncertainty 1 0.00752 I I I I 1 Methodology uncertaintyi6 I 1 0.00646 I I Statistical Sum of Uncertainties / 1 0.01916' I I Methodology BiasI7 I 1 0.00259 I Pool Temperature Bias" 0.00640 Sum of Uncertainties and Biases 0.028 16

• Conservative, actual value is 0.0 1701 delta k-effective units.

" Note the 1.50 wlo nominal KENO case for the 3x3 storage contains OFA fuel at the fresh enrichment of 4.95 '"1, '"u, which is surrounded by a ring of STD fuel at the fresh enrichment of 1.50 "/, '"U.

l 5 Note the 4.95 wlo nominal KENO case for the 3x3 storage contains OFA fuel at the fresh enrichment of 4 95 "I, '"u, which is surrounded by a ring of STD fuel at the fresh enrichment of 4.95 "1, I3'u.

'"ee page 11 for definition of methodology uncertainty

" Methodology bias or the mean calculational methods bias is evaluated to be 0.00259.

I K Pool temperature bias obtained from Reference 20.

Page 36 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Table 3-7. Lffversus Initial Enrichment and Assembly Burnup for the "All-Cell" Storage Configuration with No Soluble Boron Initial Assembly bmValue Enrichment Burnup (W/O235u) Decay Time (years)

(MWDJMTU) 0 5 10 15 20 1.79 0 N/A N/A N/A N/A N/A 3 .O 5,000 1.05509 1.05296 1.05257 1.05203 1.05189 3 .O 15,000 0.96342 0.95647 0.95173 0.94810 0.945 11 3 .O 25,000 0.89586 0.88528 0.87621 0.87085 0.86581 4.0 15,000 1.04167 1.03695 1.03345 1.03029 1.028 18 4.0 25,000 0.97260 0.96512 0.95878 0.95428 0.95044 4.0 35,000 0.91680 0.90598 0.89802 0.89109 0.88668 5.O 25,000 1.03293 1.02597 1.02081 1.01745 1.01429 5.0 35,000 0.97891 0.97055 0.963 1 1 0.95804 0.95357 5.O 45,000 0.93132 0.92004 0.91 199 0.90535 0.90018 Page 37 of 68

Westinghouse Non-Proprietary Class 3 Table 3-8. bffversus Initial Enrichment and Assembly Burnup for the Unshimmed "3x3" Storage Configuration Initial Assem bIy bfiValue Enrichment Burnup Decay Time (years)

(W/O235u) (MWD/MTU) 0 5 10 15 20 1.30 0 N/A N/ A N/A N/A N/ A 3 .O 15,000 1.02206 1.01827 1.01439 1.01271 1.01091 3.O 25,000 0.98138 0.97613 0.97112 0.96693 0.96371 3.0 35,000 0.95284 0.94771 0.94381 0.93758 0.93601 4.0 25,000 1.02507 1.01832 1.01376 1.00931 1.00722 4.0 35,000 0.98691 0.97992 0.97508 0.97023 0.96734 4.0 45,000 0.95919 0.95277 0.94768 0.94336 0.94058 5.O 35,000 1.02408 1.01798 1.01 123 1.00702 1.00468 5.O 45,000 0.99148 0.98192 0.97837 0.97205 0.96932 5 .O 55,000 0.96393 0.95477 0.95042 0.94501 0.94286 Page 38 of 68

Westinghouse Non-Proprietary Class 3 Table 3-9. hffversus Initial Enrichment and Assembly Burnup for the Shimmed "3x3" Storage Configuration Initial Assembly LffValue Enrichment Burnup (W/O235u) Decay Time (years)

(MWDM'I'U) 0 5 10 15 20 1.39 0 N/A N/A N/A N/ A N/A 3.O 5,000 1.07394 1.07387 1.07322 1.07240 1.07205 3.O 15,000 1.00569 1.00044 0.99736 0.99285 0.99075 3 .O 25,000 0.95830 0.95047 0.94594 0.94165 0.93888 4.0 15,000 1.06381 1.05964 1.05611 1.05356 1.05145 4.0 25,000 1.00643 0.99921 0.99372 0.98953 0.98634 4.0 35,000 0.96284 0.95564 0.94981 0.94696 0.94371 5 .O 25,000 1.05250 1.04664 1.04146 1.03788 1.03478 5.O 35,000 1.00477 0.99767 0.99045 0.98597 0.98254 5.O 45,000 0.96744 0.96138 0.95526 0.95 177 0.94908 Page 39 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Table 3-10. Fuel Assembly Burnup versus Initial Enrichment for the "All Cell" Storage Configuration Initial Burnup (MWDJMTU)

Enrichment Decay Time (years)

(W/O 2 3 5 ~ ) 30 0 5 10 15 1.79 0.0 0.0 0.0 0.0 0.0 3.0 14,373.9 13,563.0 13,102.0 12,754.3 12,498.1 4.0 25,722.1 24,519.2 23,595.7 22,999.5 22,499.8 5 .O 37,148.3 35,441.9 34,058.5 33,189.8 32,452.8 Page 40 of 68

Westinghouse Non-Proprietary Class 3 Table 3-11. Fuel Assembly Burnup versus Initial Enrichment for the Unshimmed "3x3" Storage Configuration Page 41 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Table 3-12. Fuel Assembly Burnup versus Initial Enrichment for the Shimmed "3x3" Storage Configuration Page 42 of 68

Westinghouse Non-Proprietary Class 3 Table 3-13. Entire Spent Fuel Pool #2 and Infinite Array kffResults for the Allowable Storage Configurations Without Biases With Biases &

& Uncertainties Uncertainties Entire Pool Infinite Array Entire Pool Description ken &IT kif All-Cell, 0.96045 0.97157 0.98723 1.80 w/o 2 3 5 ~

and zero burnup Unshimmed 3x3, 0.96647 0.97477 0.99050 1.30 wlo 2 3 5 ~

and zero burnup Page 43 of 68

Westinghouse Non-Proprietary Class 3 Table 3-14. 4ff as a Function of Soluble Boron Level The most limiting case is the "3x3" storage configuration. The following second degree polynomial describes the soluble boron concentration as a function of Akff:

ppm = 8894.9 b4ffZ+ 5059.8 A k a Page 44 of 68

Westinghouse Non-Proprietary Class 3 Table 3-15. Reactivity Associated with 5 % Burnup Uncertainty for the Storage Configurations Maximum BU Considered 5% BU Configuration (MWDIMTU) Uncertainty Aka All-Cell 45,000 2,250 0.01016 Unshimmed 3x3 52,400 2,620 0.0069 Shimmed 3x3 45,000 2,250 0.00752 Page 45 of 68

Westinghouse Non-Proprietary Class 3 Table 3-16. kfffor Accident Events All Cell 3x3 Description of Accident A4ff APPm Aka APPm Dropped fresh fuel assembly on top of Not Not Not Not the storage racks, Limiting Limiting Limiting Limiting Misloaded fresh he1 assembly into 0.04158 179.5 0.05336 244.2 burned storage rack location, Misloaded fresh fuel assembly 0.03207 112.3 0.05914 262.5 between storage racks, Intramodule water gap reduction due Not Not Not Not to seismic event, Limiting Limiting Limiting Limiting Spent fuel pool temperature greater Not Not Not Not than 185 O F Limiting Limiting Limiting Limiting Page 46 of 68

Westinghouse Non-Proprietary Class 3 Figure 3-1. Westinghouse 14x14 OFA & STD Fuel Assembly Instrument Location

? Guide Tube location I

0.5560" OFA 0.5560" STD 0.3659" STD 0.3734" STD 0.4220" STD 1

Page 47 of 68

Westinghouse Non-Proprietary Class 3 Figure 3-2. Gd203Burnable Absorber Pin Pattern Absorber Page 48 of 68

Westinghouse Non-Proprietary Class 3 Figure 3-3. Sketch of Axial Zones Employed in Fuel Assembly Page 49 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Figure 3-4. KENO Output Plot of the "All Cell" Model Page 50 of 68

Westinghouse Non-Proprietary Class 3 Figure 3-5. KENO Output Plot of the "3x3" Storage Model Page 51 of 68

Westinghouse Nan-Proprietary Class 3 WCAP-16517-NP Figure 3-6. KENO Output Plot of the "All-Cell" Spent Fuel Pool Model Note: Rack locations appear violet, pool water appears blue and pool wall appears gray in color.

Page 52 of 68

Westinghouse Non-Proprietary Class 3 Figure 3-7. KENO Output Plot of the "3x3" Spent Fuel Pool Model Note: High enrichment rack locations appear green, low enrichment rack locations appear violet, pool water appears blue and pool wall appears gray in color.

Page 53 of 68

Westinghouse Non-Proprietary Class 3 4.0 Summary of Results The following sections contain the criticality analysis results for the Prairie Island Units 1

& 2 spent fuel pool with soluble boron credit.

4.1 Allowable Storage Configurations and Interfaces Figure 4-1 displays the allowable assembly arrangements for the All Cell storage configuration. The All Cell storage configuration will be employed to store depleted fuel assemblies that meet the requirements of Figure 4-5 or no fuel assembly. The assembly burnup versus initial enrichment limits should be calculated with the third degree polynomial given in Table 4-1 based upon the appropriate decay time.

Figure 4-2 displays the allowable assembly arrangements for the unshimmed "3x3" storage configuration. The unshimmed "3x3" storage configuration will be employed to store depleted fuel assemblies which meet the requirements of Figure 4-6 or no fuel assembly. The center storage cell will be employed to store fresh fuel assemblies of enrichment values of up to and including 4.95 w/o 2 3 5 ~or no fuel assembly. The assembly burnup versus initial enrichment limits for the peripheral locations should be calculated with the third degree polynomial given in Table 4-2 based upon the appropriate decay time.

Figure 4-3 displays the allowable assembly arrangements for the Gd203 shimmed "3x3" storage configuration. The Gd203 shimmed "3x3" storage configuration will be employed to store depleted fuel assemblies which meet the requirements of Figure 4-7 or no fuel assembly. The center storage cell will be employed to store fresh fuel assemblies with a minimum of 4 Gd203 shimmed fuel rods. The minimum concentration of Gd203 is equal to 4.0 wlo. The maximum enrichment for unshimmed fresh fuel rods is equal to 4.95 w/o 235 U. The maximum enrichment for Gd203shimmed fresh fuel rods is equal to 4.0 wlo 2 3 5 ~The

. assembly burnup versus initial enrichment limits for the peripheral locations should be calculated with the third degree polynomial given in Table 4-3 based upon the appropriate decay time.

The allowable interface between the storage configurations is displayed in Figure 4-4.

Note that a row of empty storage cells at the interface may be used to separate the configurations. Also, it is acceptable to replace an assembly with an empty cell.

Note that a Failed Fuel Pin Basket (FFPB), a fully loaded Consolidation Rod Storage Basket (CRSB) with up to two (2) fuel rods missing, or a partially loaded CRSB with a maximum of 18 fuel rods may be substituted for any assembly in either the "All-Cell" or "3x3" he1 assembly storage configurations.

Page 54 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP The FFPB is employed to store up to 16 fresh fbel rods (in a 4x4 array) with a maximum enrichment less than or equal to 4.95 w/o 2 3 5 with

~ no credit for burnup.

The fblly loaded CRSC is a container designed to accommodate all of the fbel rods from two assemblies and fit into a single storage location. Note that up to two fbel rods may be missing from the container. The current burnup versus initial enrichment tech spec limits for the fully loaded CRSC are still valid.

A partially loaded CRSC may contain up to 18 fresh fbel rods with a maximum enrichment less than or equal to 4.95 w/o 2 3 5 with

~ no credit for burnup.

4.2 Burnup Credit Figure 4-5 displays the assembly burnup versus initial enrichment storage curve for the All Cell storage configuration. The All Cell storage requirements are tabulated in Table 4-1 for 0, 5, 10, 15, and 20 years of decay time. The assembly burnup versus initial enrichment limits should be calculated with the third degree polynomial given in Table 4-1 based upon the appropriate decay time.

Figure 4-6 displays the burnup versus enrichment storage curve for the unshimmed "3x3" storage configuration. The unshimmed "3x3" storage requirements are tabulated in Table 4-2 for 0, 5, 10, 15, and 20 years of decay time. The assembly burnup versus initial enrichment limits for the peripheral locations should be calculated with the third degree polynomial given in Table 4-2 based upon the appropriate decay time.

Figure 4-7 displays the burnup versus enrichment storage curve for the shimmed "3x3" storage configuration. The shimmed "3x3" storage requirements are tabulated in Table 4-3 for 0, 5, 10, 15, and 20 years of decay time. The assembly burnup versus initial enrichment limits for the peripheral locations should be calculated with the third degree polynomial given in Table 4-3 based upon the appropriate decay time.

4.3 Total Soluble Boron Requirement The total soluble boron (sum of all three components) required to maintain the bffvalue (including all biases and uncertainties, without the adjustment for 'OB) less than or equal to 0.95 is determined to be 722 ppm for a 'OB atom percent equal to 19.9. The soluble boron concentration required for a 'OB atom percent equal to 19.7 is 730 ppm. The recommended minimum boron level is 730 ppm and is sufficient to accommodate all the design requirements.

Page 55 of 68

Westinghouse Non-Proprietary Class 3 Table 4-1. Fuel Assembly Burnup versus Initial Enrichment for the bbAIl-Cell" Storage Configuration Initial Burnup (MWDMTU)

Enrichment Decay Time (years)

(w/o 2 3 5 ~ ) 0 5 10 15 20 1.79 0.0 0.0 0.0 0.0 0.0 3.0 14,373.9 13,563.0 13,102.0 12,754.3 12,498.1 4.0 25,722.1 24,519.2 23,595.7 22,999.5 22,499.8 5.0 37,148.3 35,441.9 34,058.5 33,189.8 32,452.8 The 3rddegree polynomial that describes the 0 years decay time curve is as follows:

The 31d degree polynomial that describes the 5 years decay time curve is as follows:

The 31d degree polynomial that describes the 10 years decay time curve is as follows:

The 31d degree polynomial that describes the 15 years decay time curve is as follows:

BU = 39.90e3 - 506.32e2+ 12312.99e - 20705.14 The 31d degree polynomial that describes the 20 years decay time curve is as follows:

Page 56 of 68

Westinghouse Non-Proprietary Class 3 Table 4-2. Fuel Assembly Burnup versus Initial Enrichment for the Unshimmed "3x3" Storage Configuration as a function of decay time The 31d degree polynomial that describes the 0 years decay time curve is as follows:

The 31d degree polynomial that describes the 5 years decay time curve is as follows:

The 31d degree polynomial that describes the 10 years decay time curve is as follows:

The 31d degree polynomial that describes the 15 years decay time curve is as follows:

BU = 270.12e3 - 3399.80e2 + 24721.90e - 27016.941 The 31d degree polynomial that describes the 20 years decay time curve is as follows:

BU = 202.95e3 - 2616.35e2 + 21767.79e - 24350.831 Page 57 of 68

Westinghouse Non-Proprietary Class 3 Table 4-3. Fuel Assembly Burnup versus Initial Enrichment for the Gd203Shimmed "3x3" Storage Configuration as a function of decay time The 3rddegree polynomial that describes the 0 years decay time curve is as follows:

BU = 385.78e3- 4530.66e2+ 28423.72e - 31899.431 The 3rddegree polynomial that describes the 5 years decay time curve is as follows:

The 3rddegree polynomial that describes the 10 years decay time curve is as follows:

BU = 335.89e3- 3836.313 + 24635.61e - 27828.70/

The 3rddegree polynomial that describes the 15 years decay time curve is as follows:

The 3rddegree polynomial that describes the 20 years decay time curve is as follows:

Page 58 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Figure 4-1. Allowable Fuel Assembly Combinations for the "All-Cell" Storage Configuration "M" represents Depleted fuel assembly with meets the requirements of Figure 4-5.

An empty location.

Page 59 of 68

Westinghouse Non-Proprietary Class 3 Figure 4-2. Allowable Fuel Assembly Combinations for the Unshimmed "3x3" Storage Configuration "H" represents Depleted fuel assembly which meets the requirements of Figure 4-6.

or An empty location.

"Xyy represents Fresh unshimmed fuel assembly of enrichment values to and including 4.95 W/o or An empty location.

Page 60 of 68

Westinghouse Non-Proprietary Class 3 Figure 4-3. Allowable Fuel Assembly Combinations for the Gd2O3Shimmed "3x3" Storage Configuration

" H represents Depleted fuel assembly which meets the requirements of Figure 4-7.

-or An empty location.

"X" represents Fresh Gd203 shimmed fuel assembly. Minimum of 4 shimmed fuel rods with a minimum of 4 wlo Gd203, Maximum enrichment for unshimmed rods is 4.95 W/o 2 3 5 ~Maximum

. enrichment for shimmed rods is 4.0 "1, 2 3 5 ~ .

or An empty location.

Page 61 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Figure 4-4. Boundary Between the "3x3" and "All-Cell" Storage Configurations i

A = "All-Cell" Storage Location L = "3x3" Low Enrichment Location H = "3x3" High Enrichment Location Notes:

1) A row of empty cells can be used at the interface to separate the configurations.

2) It is acceptable to remove an assembly from any storage location.

Page 62 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Figure 4-5. Prairie Island Units 1 & 2 Assembly Burnup Requirements for the "All-Cell" Storage Configuration Page 63 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Figure 4-6. Assembly Burnup Requirements for the Peripheral Fuel Assemblies in the Unshimmed "3x3" Storage Configuration Page 64 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP Figure 4-7. Assembly Burnup Requirements for the Peripheral Fuel Assemblies in the Shimmed "3x3" Storage Configuration Initial U-235 Enrichment (nominal wlo)

Page 65 of 68

Westinghouse Non-Proprietary Class 3 5.0 Computer Codes Used In Calculation Table 5-1 Summary of Computer Codes Used in Calculation Code Code Name Code Verified and Configured Basis (or reference) that supports Outstanding Issues No. Version (Yes/No) use of code in current calculation (Yes/No).

1 SCALE-PC 4.3 Yes QC- 1 No, see Note Note: There is a recent notification of an error in SCALE associated with the HOLE function. The error is documented in the SCALE notebook, titled "Error in KENO V.a for cylindrical holes with shared boundaries," and dated March 22, 2005. In the standard spent fuel pool analysis, none of the input files involve cylindrical holes with shared boundaries; therefore, the analysis is not affected from this code error.

Page 66 of 68

Westinghouse Non-Proprietary Class 3 6.0 References

1. Not Used.

2. Letter, G. S. Vissing (NRC) to R. C. Mecredy (RGE), "R. E. Ginna Nuclear Power Plant - Amendment Re-Revision to the Storage Configuration Requirements within the Existing Storage Racking and Taking Credit for a Limited Amount of Soluble Boron", December 7,2000.

3. Letter, T. E. Collins (NRC) to T. Greene (WOG), "Acceptance for Referencing of Licensing Topical Report WCAP- 14416-P, Westinghouse Spent Fuel Rack Methodology (TAC No. M93254)", October 25, 1996.

4. Code of Federal Regulations, Title 10, Part 50, Appendix A, Criterion 62, "Prevention of Criticality in Fuel Storage and Handling".

5. L. Kopp (NRC), "Guidance on the Regulatory Requirements for Criticality Analysis of Fuel Storage at Light-Water Reactor Power Plants", February 1998.

6. "SCALE 4.3- Modular Code System for Performing Standardized Computer Analyses for Licensing Evaluation for Workstations and Personal Computers",

NUREGICR-200; distributed by the Radiation Shielding Information Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee, July 1993.

7. "DIT: Discrete Integral Transport Assembly Design Code", CE-CES-11, Revision 4-P, April 1994.

8. M. N. Baldwin, et al., "Critical Experiments Supporting Close Proximity Water Storage of Power Reactor Fuel; Summary Report", BAW- 1484-7, July 1979.

9. S. R. Bierman and E.D. Clayton, "Critical Experiments with Subcritical Clusters of 2.35 Wt% 2 3 5 Enriched

~ U02 Rods in Water at a Water-to-Fuel Volume Ratio of 1.6", NUREGICR-1547, PNL-33 14, July 1980.

10. S.R. Bierman and E.D. Clayton, "Criticality Experiments with Subcritical Clusters of 2.35 and 4.31 Wt% U-Enriched U02 Rods in Water with Steel Reflecting Walls",

Nuclear Technology, Vol. 54, pg. 131, August 1981.

11. International Handbook of Evaluated Criticality Safety Benchmark Experiments, Nuclear Energy Agency and Organization for Economic Cooperation and Development.

12. W. Marshall, et al., "Criticality Safety Criteria", TANS Vol. 35, pg. 278, 1980.

13. D. B. Owen, "Factors for One-Sided Tolerance Limits and for Variables Sampling Plans", SCR-607, Sandia Corporation Monograph, March 1963.

Page 67 of 68

Westinghouse Non-Proprietary Class 3 WCAP-16517-NP

14. "Topical Report on Actinide-Only Burnup Credit for PWR Spent Fuel Packages",

DOEIRW-0472 Rev. 1, May 1997.

15. Not Used.

16. Parrington, Josef R., et al, "Nuclides and Isotopes: Chart of the Nuclides", Fifteenth Edition, General Electric Co. and KAPL, Inc., 1996.

17. "Implementation of ZIRLOTM Cladding Material in CE Nuclear Power Fuel Assembly Designs", CENPD-404-P, Rev. 0, January 2001.

18. "Methodology Manual for Cross Section Tableset Generation", CE-CES-124, Revision 2-P, June 1994.

19. P.F. O'Donnell, et al, "R.E. Ginna Nuclear Power Plant Criticality Safety Analysis for the Spent Fuel Storage Rack Using Soluble Boron Credit", RGE-09-0009, Revision 0, November 1999.

20. J.R. Lesko, et al., "Northern States Power Prairie Island Units 1 and 2 Spent Fuel Rack Criticality Analysis Using Soluble Boron Credit", CAA-97-042, Revision 0, February 1997.

Page 68 of 68

Enclosure 3 Technical Specification revised Figures 3.7.17-1,4.3.1-3 and 4.3.14 3 pages follow

Spent Fuel Pool Storage 3.7.17 i -0 years i

-5 years

-10 years

-15 years

-20 years 1 2 3 4 5 Initial Enrichment (%U235)

Figure 3.7.17-1 Spent Fuel Pool Unrestricted Region Burnup and Decay Time Requirements Prairie Island Unit 1 - Amendment No. 4443 Units 1 and 2 3.7.17-3 Unit 2 - Amendment No. 4-49

Design Features 4.0

-0 years

-5 years

-10 years

-15 years

-20 years 1 2 3 4 5 Initial Enrichment (% U235)

Figure 4.3.1-3 Spent Fuel Pool Checkerboard Region Burnup and Decay Time Requirements

- NO GAD Prairie Island Unit 1 - Amendment No. 43%

Units 1 and 2 4.0-7 Unit 2 - Amendment No. 44-9

Design Features 4.0 1 2 3 4 5 Initial Enrichment (%U235)

Figure 4.3.1-4 Spent Fuel Pool Checkerboard Region Burnup and Decay Time Requirements - Fuel with GAD Prairie Island Unit 1 - Amendment No. 44-8 Units 1 and 2 4.0-8 Unit 2 - Amendment No. 4 4