L-2009-264, Issuance of Amendment Regarding Spent Fuel Boraflex Remedy Supplement 6 to Request for a Change in Implementation Date

Issuance of Amendment Regarding Spent Fuel Boraflex Remedy Supplement 6 to Request for a Change in Implementation Date

ML093200209
Person / Time
Site:	Turkey Point
Issue date:	11/12/2009
From:	Kiley M Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2009-264
Download: ML093200209 (16)

Text

0 FPL.

POWERING TODAY.

EMPOWERING TOMORROW. 10 CFR 50.90 L-2009-264 November 12, 2009 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington D.C. 20555-0001 Re: Turkey Point Unit 4 Docket No. 50-251 Issuance of Amendment Regarding Spent Fuel Boraflex Remedy Supplement 6 to Request for a Change in Implementation Date

References:

1. Letter from Michael Kiley (FPL) to USNRC, "Implementation Date Change for License Amendments 234 and 229," L-2009-200, September 1, 2009.

2. Letter from Michael Kiley (FPL) to USNRC, "Withdrawal of License Amendment Request No. 201 for Turkey Point Unit 3," L-2009-260, November 9, 2009.

Florida Power and Light Company (FPL) submitted an application for amendment of the Unit 3 and 4 licenses in Reference 1. The application for Unit 3 was withdrawn by FPL in Reference 2.

This letter provides FPL responses to an NRC staff request for additional information (RAI) provided to FPL via email dated November 10, 2009. The FPL RAI response is attached.

FPL has determined that the additional information provided in this correspondence does not impact the conclusions of the No Significant Hazards Consideration determination in Reference 1.

If you have any questions or require additional information, please contact Robert Tomonto at 305-246-7327.

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

Very truly yours, 11/12/2009 Executed on Michael Kiley Vice President - Turkey Point Nuclear Plant cc: Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, Turkey Point Nuclear Plant USNRC Project Manager for Turkey Point Mr. William Passetti, Florida Department of Health an FPL Group company N R ýZ

Attachment to FPL Letter L-2009-264 Issuance of Amendment Regarding Spent Fuel Boraflex Remedy Supplement 6 to Request for a Change in Implementation Date Response to NRC Request for Additional Information 14 Pages

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 1 of 14 Florida Power and Light Company Response to NRC Request for Additional Information NRC Question 1 By letter dated July 27, 2001, the NRC staff concluded that the Westinghouse methodology of WCAP-14416 could no longer be referenced as "approved methodology" by the NRC staff or the licensees. In its letter, the NRC stated that, "[f]or future licensing actions, licensees will need to submit plant-specific criticality calculations for spent fuel pool configurations that include technically supported margins." In order for the staff to find reasonable assurance that Turkey Point Unit 4 fuel storage will comply with the regulatory limit of k.ff less than 1.0 under unborated conditions, please address the following additional questions.

NRC Question (la)

NSAL-00-015 states that, "typical range of values of the non-conservatism is 0 to 0.03000 delta-K." Please describe the method you used to determine the Turkey Point penalty of 0.0 1665 and explain how the penalty is conservative for Turkey Point.

FPL Response (la)

A core depletion calculation is used to generate axial burnup profiles from the 3D nodal code ANC. These profiles are generated with control bank D (D-bank) inserted to 215 steps withdrawn. The impact of rod insertion is to skew the power shapes to the bottom of the core. The 215 step D-bank position is deeper than typical for Turkey Point Unit 3 and 4 operations, and because the rods are not removed, the insertion extends for a significantly longer duration than typical during operations. Operation with control rod insertion is the primary expected mechanism to create bottom skewed power shapes in Westinghouse cores.

These calculations are performed for a typical 12-foot tall core. The burnup profiles generated are generically applicable to 12-foot Westinghouse designed cores, including Turkey Point Units 3 and 4. The ANC calculations were performed to generate steep burnup gradients at the top of the fuel assemblies. These steep gradients lead to a conservative determination of "end-effect" reactivity and, in this case, a conservatively large axial burnup bias penalty.

The axial burnup profile is determined for four assemblies with average burnups near 15,000, 35,000, 45,000, and 55,000 MWd/MTU. A bias is determined between the generated shape at each assembly average burnup and a uniform profile depleted to that same burnup. This bias is then fit as a function of burnup so that the bias can be determined at specific burnup points. The burnups and bias values are presented below in Table 1. The table also contains the cubic fit of the data provided.

A burnup value of 36,834 MWd/MTU was used in the fit provided in Table 1 to determine the axial burnup bias penalty of 0.01665 Aklff. The Turkey Point Units 3 and 4 Region II

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 2 of 14 burnup limit for the allowable maximum enrichment is 36,746 MWd/MTU. The bias at the actual burnup limit is 0.01659 Akeff. Therefore, the penalty evaluated for the NSAL of 0.01665 Aklff is conservative.

The use of a rodded configuration during the depletion produces axial bumup profiles with low burnup at the top of the core, therefore the burnup bias penalty represents a conservative estimate of the "end-effect" for Turkey Point Units 3 and 4.

Table 1. Burnup Shape Bias Points and Fit Assembly Average Burnup (MWd/MTU) Bias (10-5 Akeff) 15210 -233 36790 1662 44736 2323 54507 3461 Penalty = 5.17887e-11*(BU 3) - 5.16652e-06*(BU 2) + 2.45415e-01*(BU) - 2.95275e+03 NRC Question (1b)

Please provide the boron letdown curve that was credited for the Turkey Point NSAL-00-0 15 analysis. Please demonstrate that the credited curve bounds those curves from the recent past cycles and future cycles.

FPL Response (1b)

The boron concentration assumed in the depletion calculations performed for the Turkey Point Units 3 and 4 analysis of record is a constant 1500 ppm. A more realistic, yet still conservative, letdown curve is used to provide a conservative estimate of the reactivity margin inherent in the constant 1500 ppm assumption.

The assessment was evaluated with a 17x 17 fuel assembly. The more realistic case depleted the fuel assuming a boron letdown curve of 1600 ppm at 0 MWd/MTU, 900 ppm at 15,000 MWd/MTU, and 10 ppm at 30,000 MWd/MTU. This letdown curve was used again for a second cycle of operation to deplete the fuel assembly to a total of 60,000 MWd/MTU. This depletion also considered the presence of an 8-fingered WABA during the first cycle of operation and 104 IFBA rods present throughout the depletion. The use of the WABA and IFBA was designed to harden the spectrum associated with the depletion during the simulated first cycle of operation. The Turkey Point Units 3 and 4 Region II burnup limit for the allowable maximum enrichment is 36,746 MWd/MTU Therefore, the benefit for the use of a more realistic letdown curve is primarily calculated from the first simulated depletion cycle. It is therefore concluded that the presence of the burnable absorber provides sufficient spectral hardening to generate a conservative estimate of discharged assembly reactivity. As discussed below, the more realistic boron letdown curve bounds the actual operating history at both Turkey Point units, and is therefore still a conservative letdown curve for determining discharged assembly reactivity.

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 3 of 14 The reactivity difference between the two letdown curves is determined at 30,000 and 60,000 MWd/MTU. The boron letdown credit values are 0.00326 and 0.01481 Akeff respectively.

These differences are fit as a function of burnup, including zero credit at zero bumup, to generate the following equation:

Credit (10-5 Akeff) = 4.60556e-07*(BU 2) - 2.95e-03*(BU) - 5.68434e-14 A burnup value of 36,834 MWd/MTU is used in the fit above to determine the burnup letdown curve credit of 0.00516 Akeff. The Turkey Point Units 3 and 4 Region II Technical Specification burnup limit is 36,746 MWD/MTU. The credit determined at this burnup is 0.00513 Akeff from the more realistic boron letdown curve. This reduces the credit by 0.00003 Aklff, but the axial burnup shape penalty associated with the Technical Specification bumup limit was lowered by 0.00006 Akcff. The final margin determined with the burnup value of 36,834 MWd/MTU is therefore a conservative value.

Turkey Point cycle specific boron letdown data was reviewed (8 cycles for each unit) to determine the most limiting boron letdown curve based on boron concentration and cycle length. Based on the review, the most limiting Turkey Point cycle had a peak boron concentration of 1300 ppm with a cycle length of 17,500 MWD/MTU which is bounded by the boron letdown assumed in NSAL-00-0 15. This conclusion will also apply to future Turkey Point cycles.

NRC Question (ce)

Please list the isotopes that you credited prior to applying the "Samarium and fission product buildup credit." What other fission product isotopes are credited under the "Samarium and fission product buildup credit?"

FPL Response (1c)

The isotopes considered in the analysis of record for Turkey Points Units 3 and 4 are listed below in Table 2. The presence of all these isotopes is credited; however, the increased concentrations created by decay after reactor shutdown are not credited. The last sentence of the section on samarium and fission product buildup in NSAL-00-0 15 indicates that the credit is derived from this buildup after shutdown.

The credit is determined by a series of depletion and decay calculations utilizing a 17x17 lattice. In the base calculation, the fission products, including samarium, are held constant.

In the perturbed calculation, the number densities are allowed to change over decay intervals of 100 and 200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> after shutdown. The reactivity difference between these two cases is determined at a range of enrichments from 1.25 to 5.0 w/o 235U. A range of burnups was considered for each enrichment, ranging from 4 MWd/MTU for 1.25 w/o to 60,000 MWd/MTU for 5.0 w/o. The samarium and fission product buildup credit diminishes at higher enrichments. The 100-hour cooling time also generates a lower credit than does the

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 4 of 14 200-hour cooling time. A penalty is also included to account for the lower fission product inventories resulting from operation at less than full power. This is included to cover reduced power operation extending to the end of a cycle. The generic credit of 0.00200 Akeff is determined based on the limiting conditions of 5 w/o and 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> of decay time. The impact of fission product absorption is largely invariant to lattice type, so this credit is applicable to the Turkey Point units. The current technical specifications for Turkey Point Units 3 and 4 only allow fuel of up to 4.5 w/o 235U enrichment, so the use of the credit as determined for 5 w/o fuel is conservative.

Table 2: List of Isotopes Used in the Analysis of Record for Turkey Point Units 3 and 4 Name I Identifier Name Identifier U-235 92235 U-236 92236 U-238 92238 Np-237 93237 Pu-238 94238 Pu-239 94239 Pu-240 94240 Pu-241 94241 Pu-242 94242 Am-241 95241 Am-242m 95242 Am-243 95243 Cm-242 96242 Cm-244 96244 Rh-103 45103 Rh-105 45105 Ag-109 47109 Xe-131 54131 Cs-133 55133 Cs-134 55134 Cs-135 55135 Nd-143 60143 Nd-145 60145 Pm-147 61147 Pm-148 61148 Pm-148m 61248 Sm-147 62147 Sm-149 62149 Sm-150 62150 Sm-151 62151 Sm-152 62152 Eu-153 63153 Eu-154 63154 Eu-155 63155 Gd-155 64155 Kr-83 36083 Lumped FP-2 99002 Lumped FP-1 99001 1-135 53135 Pm- 149 61149 0-16 8016 NRC Question (1d)

Please provide the uncertainties and biases "rackup" determined in the Turkey Point NSAL-00-015 analysis for both Region I and Region II.

FPL Response (1d)

NSAL-00-0 15 does not discuss Region I of the Turkey Point Units 3 and 4 spent fuel pool because no burnup credit is required for fuel storage in Region I in the analysis of record.

The NSAL specifically addresses the potential non-conservatism caused by the use of a 2-D

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 5 of 14 to 3-D burnup shape bias in depletion calculations. Since no burnup is credited, no non-conservatism exists. For completeness, the rackup is provided below in Table 3.

The bias and uncertainty rackup for Region II of the Turkey Point Units 3 and 4 spent fuel pools is shown below in Table 4. The column labeled "AOR" presents the original analysis of record values for each bias and uncertainty. The column labeled "NSAL" provides the less conservative values determined for each uncertainty, as appropriate, during the evaluation of the impact of the potential non-conservatism of the bumup shape bias.

A generic uncertainty was determined for the enrichment uncertainty, the dishing and chamfering uncertainty, and the fuel density uncertainty. The lower enrichment uncertainty is generated by applying the +/-0.05 w/o tolerance at enrichments more representative of the assemblies needing burnup credit. The lower uncertainty on fuel density is determined by reducing the tolerance band to cover the process maximum. The Turkey Point analysis of record considered a theoretical density tolerance that was conservatively bounding the process maximum density in the fuel fabrication plant. The uncertainty in dishing and chamfering actually increased slightly because of the generic methodology that reduced the calculated uncertainty. The value was then halved because the calculations to determine the uncertainty compared nominal dishing with no dishing. Use of a halved uncertainty is still conservative when compared to the small variation found due to the actual dishing tolerance.

The difference in the convoluted sum of uncertainties is demonstrated to be 0.00467 Akeff.

This is 0.00001 Aklff larger than shown in the summary of credits table provided previously.

This slight difference is due to rounding of individual uncertainty terms in the rackup.

Table 3. Bias and Uncertainty Rackups for Turkey Point Units 3 and 4 Region I Parameter AOR Fuel Enrichment Uncertainty 0.00191 Fuel Density Uncertainty 0.00250 Fuel Pellet Dishing Uncertainty 0.00145 Rack Cell Inner Dimension Uncertainty 0.00153 Rack Cell Pitch Uncertainty 0.01022 Rack Wall Thickness Uncertainty 0.00024 Wrapper Plate Thickness Uncertainty 0.00000 Poison Panel Thickness Uncertainty 0.00973 Poison Cavity Thickness Uncertainty 0.00004 Poison Panel Width Uncertainty 0.00047 Asymmetric Assembly Position 0.00534 Calculation Uncertainty 0.00129 Benchmark Bias Uncertainty 0.00300 Statistical Convolution of Uncertainties 0.01590 Benchmark Bias 0.00770 Pool Temperature Bias 0.00077 Boron Particles in Boraflex Bias 0.00384 Sum of Biases 0.01231 Overall Sum of Biases and Uncertainties 0.02821

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 6 of 14 Table 4. Bias and Uncertainty Rackups for Turkey Point Units 3 and 4 Region II Parameter AOR NSAL Fuel Enrichment Uncertainty 0.00972 0.00300 Fuel Density Uncertainty 0.00254 0.00064 Fuel Pellet Dishing Uncertainty 0.00116 0.00125 Rack Cell Inner Dimension Uncertainty 0.00000 0.00000 Rack Cell Pitch Uncertainty 0.00116 0.00116 Rack Wall Thickness Uncertainty 0.00000 0.00000 Wrapper Plate Thickness Uncertainty 0.00000 0.00000 Poison Panel Thickness Uncertainty 0.00582 0.00582 Poison Cavity Thickness Uncertainty 0.00000 0.00000 Poison Panel Width Uncertainty 0.00026 0.00026 Asymmetric Assembly Position 0.00000 0.00000 Calculation Uncertainty 0.00041 0.00041 Benchmark Bias Uncertainty 0.00300 0.00300 Statistical Convolution of Uncertainties 0.01211 0.00744 Benchmark Bias 0.00770 0.00770 Pool Temperature Bias 0.00103 0.00103 Boron Particles in Boraflex Bias 0.00450 0.00450 Sum of Biases 0.01323 0.01323 Overall Sum of Biases and Uncertainties 0.02534 0.02067

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 7 of 14 NRC Question 2 In the letter dated October 28, 2009, you provide that for Unit 4, the projected Boraflex degradation on 9/30/2012 for Region I and Region II is 19% and 8% respectively. During a call with the licensee, the staff was informed that for Unit 3, the projected Boraflex degradation on 9/30/2012 for Region I and Region II is 68% and 64% respectively. The staff also understands that Unit 4 projection has not been benchmarked by measurements. To allow the staff to determine the level of confidence on the Unit 4 predictions and to understand the large difference between the two units, please provide the following additional information:

FPL Response 2 Please note that in Letter L-2009-247 dated October 29, 2009 FPL committed to perform our next scheduled Boraflex panel surveillance using the EPRI BADGER neutron attenuation methodology in the Unit 4 spent fuel pool (SFP). The test will occur no later than May 30, 2010. This will provide additional validation of the EPRI RACKLIFE model for the Unit 4 SFP that is used to predict the extent of Boraflex degradation in the Unit 4 SFP.

Additionally, FPL will provide to the NRC a copy of the vendor's surveillance report within 120 days of completing the surveillance.

NRC Question (2a)

Please provide the "measured to predicted" comparison for the maximum degradation for Unit 3 based on measurements conducted in 2001, 2004, and 2007.

FPL Response (2a)

The tables and figures below provide the complete set of measured to predicted degradation comparisons for all panels measured during the Unit 3 2001, 2004 and 2007 measurement campaigns.

This complete set of data is used to validate the performance of the RACKLIFE model. As can be seen from the data, RACKLIFE predicted panel degradation is predominately conservative relative to measured degradation. Using the results from all the measurements is a better indication of the validity of the RACKLIFE model because a single measurement is subject to not only measurement variability, but also as-built B- 10 areal density variability which can be as great as 63% and isolated incidents of Boraflex wrapper plate damage.

The measured to predicted results shown below have some conservatisms inherent to the data test method and RACKLIFE predictions. The BADGER B-10 areal density testing measured panel degradation results shown below include panel shrinkage and gaps in the average areal density degradation values. Boraflex panel shrinkage and gap formation is not considered in RACKLIFE, but is handled separately as a conservative assumption in the licensing basis

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 8 of 14 criticality analysis. This inconsistency results in the RACKLIFE predictions appearing to be less conservative.

Furthermore, the RACKLIFE predictions are used conservatively to determine future actions.

RACKLIFE predicted panel degradation assumes the initial B- 10 areal density to be at the minimum certified areal density when projecting whether a panels B-10 areal density will fall below the minimum degraded areal density assumed in the licensing basis criticality analysis.

Additionally, although RACKLIFE predicts that many panels are above the minimum degraded areal density, no credit is taken for the additional areal density in these panels.

The average RACKLIFE predicted degradation is conservative compared to average measured panel degradation, as well as the majority of the panels. This demonstrates the conservative nature of the RACKLIFE predictions. Furthermore, the conservative application of the RACKLIFE model as discussed above provides further conservatism.

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Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 11 of 14 Region I Measured vs. Predicted Degradation Measured Degradation from Predicted Degradation from Test Unirradiated Panel Unirradiated Panel Year Cell Panel DM Dp 2007 LL75 North -6.10% -2.3%

2007 LL75 North 3.70% -2.3%

2007 LL79 North -39.40% -2.3%

2007 JJ73 East -42.90% -8.4%

2007 JJ73 West -30.70% -8.2%

2007 LL79 West -24.80% -23.3%

2007 JJ73 South -28.90% -19.2%

2007 EE74 East -21.50% -25.7%

2007 EE75 North -23.30% -30.6%

2007 KK79 East -37.00% -38.2%

2007 FF75 West -30.10% -36.4%

2007 FF74 East -33.50% -36.3%

2007 HH79 South -23.50% -42.4%

2007 HH79 West -35.70% -42.6%

2007 EE82 North -26.10% -44.6%

2007 DD79 North -18.80% -44.6%

2007 DD81 North -28.90% -45.5%

2007 EE81 East -23.50% -45.4%

2007 DD79 South -19.30% -45.6%

2007 GG81 West -27.90% -45.4%

2007 DD80 West -19.10% -46.1%

2004 LL63 North 3.40% -2.1%

2004 LL63 South -3.40% -2.1%

2004 JJ73 West -26.50% -5.8%

2004 JJ73 South -21.40% -14.0%

2004 KK78 East -3.10% -27.0%

2004 KK79 East -5.90% -27.8%

2004 KK77 South -8.20% -30.2%

2004 HH79 South -3.90% -30.5%

2004 EE82 East 22.10% -31.6%

2004 HH79 West 2.90% -30.6%

2004 CC77 East 3.00% -31.9%

2004 EE82 North 15.70% -32.1%

2004 CC76 East 3.20% -32.2%

2004 DD79 North 27.30% -32.1%

2004 HH81 East 0.70% -32.1%

2004 EE80 West 4.40% -32.8%

2004 FF81 West 3.50% -32.9%

2004 DD79 South -2.60% -32.8%

2004 DD80 East 15.60% -33.2%

2004 DD80 North 15.70% -33.2%

2001 LL63 North 0.30% -1.7%

2001 LL63 South -0.30% -1.7%

2001 JJ73 West -34.00% -3.4%

2001 JJ73 East -3.80% -3.8%

2001 JJ73 South 16.80% -7.4%

2001 GG74 East 4.00% -9.3%

2001 GG74 South 4.80% -9.7%

2001 FF74 East 0.80% -10.7%

2001 FF74 South 2.50% -11.0%

2001 KK77 South 26.90% -12.4%

2001 KK77 West -28.30% -12.4%

2001 EE81 East 19.50% -13.2%

2001 EE80 West 8.50% -13.3%

2001 FF81 West 12.10% -13.3%

2001 DD80 East 8.00% -13.4%

2001 DD80 South -4.10% -13.4%

2001 DD80 North 15.70% -13.4%

2001 DD80 West 21.30% -13.4%

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 12 of 14 Region II Measured vs. Predicted Degradation Measured Degradation from Predicted Degradation from Test Unirradiated Panel Unirradiated Panel Year Cell Panel D, Dp 2007 T53 East -3.10% -3.21%

2007 V53 West 1.50% -3.21%

2007 V53 West 1.60% -3.21%

2007 M31 East -33.10% -20.15%

2007 T30 West -24.10% -21.94%

2007 T32 South -6.60% -18.03%

2007 L28 East -11.10% -33.35%

2007 L30 East -31.40% -32.58%

2007 R27 East -7.30% -25.22%

2007 L27 East -16.40% -33.46%

2007 T25 East -17.90% -19.24%

2007 L38 East -55.90% -35.42%

2007 N23 East -39.50% -43.73%

2007 T25 South -7.90% -22.37%

2007 R17 East -31.20% -46.18%

2007 R17 South -9.00% -46.10%

2007 R25 North -12.10% -42.61%

2007 P16 East -15.80% -46.56%

2007 P16 South -2.10% -46.70%

2007 M16 South -12.60% -46.77%

2007 L17 North -20.00% -46.72%

2004 T53 East 4.00% -2.89%

2004 T53 West 12.90% -2.89%

2004 V53 West -16.80% -2.89%

2004 V53 North 8.50% -2.89%

2004 T53 North 6.80% -3.69%

2004 V14 West 0.20% -13.70%

2004 Ull East -10.90% -18.05%

2004 Vii West 8.50% -18.05%

2004 U11 North 19.00% -22.97%

2004 V14 North 15.50% -26.78%

2004 U12 South 16.60% -29,44%

2004 U13 North 18.60% -29.44%

2004 U13 East -5.20% -29.25%

2004 R19 East -62.50% -31.56%

2004 R19 North -9.90% -32.03%

2004 R19 South -2.70% -32.07%

2004 R19 West -21.00% -32.66%

2004 P18 East -45.30% -33.17%

2004 S18 East -8.30% -33.06%

2004 N17 South -0.60% -33.33%

2004 N18 North 11.10% -33.33%

2004 P18 South 2.60% -33.30%

2004 M18 South -34.80% -33.31%

2004 M19 North -7.00% -33.31%

2004 N19 South -2.00% -32.84%

2004 P16 East 5.40% -33.44%

2004 L16 South 3.40% -33.52%

2004 L17 North 6.10% -33.52%

2004 P16 South 10.50% -33.53%

2004 M16 South 4.30% -33.56%

2001 T53 West 1.40% -2.27%

2001 U53 East 53.90% -2.27%

2001 U53 West -4.70% -2.27%

2001 U53 West 3.40% -2.27%

2001 V53 North 42.50% -2.27%

2001 U53 North 10.30% -2.46%

2001 V12 North 19.80% -6.29%

2001 U11 East 56.00% -9.50%

2001 U11 West 67.80% -10.89%

2001 U11 North 54.20% -11.06%

2001 U13 South 44.80% -10.84%

2001 Ull South 91.50% -12.20%

2001 U13 North 69.50% -12.40%

2001 U13 East 30.10% -11.98%

2001 R15 West 5.90% -13.32%

2001 R15 East 66.60% -13.32%

2001 R15 South 36.00% -13.38%

2001 M16 East 4.80% -13.44%

2001 P16 West 10.50% -13.43%

2001 P16 East 13.30% -13.44%

2001 M16 West -48.60% -13.49%

2001 M16 South 4.50% -13.46%

2001 P16 South 48.10% -13.46%

2001 M16 North 31.80% -13.49%

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 13 of 14 NRC Question (2b)

Was RACKLIFE recalibrated after each measurement campaign (i.e., 2001, 2004, 2007) to perform the subsequent predictions?

FPL Response (2b)

No, the RACKLIFE model was not recalibrated after any of the measurement campaigns because the results show that RACKLIFE predictions were predominately conservative compared to measurements. This is consistent with recommendations from NETCO in the latest (2007) BADGER measurement campaign report (NET-279-01, Rev. 2).

NRC Question (2c)

Please explain how the bulk pool silica measurement properly reflects the predicted maximum Boraflex degradation. Please address the impact of silica being trapped in the "tab" of the Unit 4 racks on the fidelity of the silica measurement as a correlation for Boraflex degradation (i.e., if silica content in the SFP water is an indication of neutron absorber degradation how is the trapped silica measured or accounted for as an indicator of neutron absorber degradation in Unit 4?).

FPL Response (2c)

The measurement of the bulk pool silica concentration is only reflective of the total degradation of all Boraflex panels. In the absence of pool dilutions or extensive cleanup operations (e.g. reverse osmosis) it approaches an equilibrium value but slowly increases as a result of continued degradation of all Boraflex panels. Thus in a semi-static environment, the lower measured silica concentration of the Unit 4 SFP is indicative of less pool wide Boraflex degradation than that of the Unit 3 SFP. As described in our letter L-2009-24 dated October 29, 2009, RACKLIFE is used determine individual panel performance by modeling the key Boraflex dissolution mechanisms in the SFP, modeling and tracking the irradiation history and silica transport of each Boraflex panel in the SFP. The Turkey Point RACKLIFE models for Units 3 and 4 have been adjusted by the code vendor such that the model shows reasonable agreement between the calculated silica concentration and the historical measured concentration. In this way the RACKLIFE models provide the individual panel performance, including the maximum panel degradation, consistent or conservative with respect to bulk pool silica measurements.

The poison cavity is surrounded by a rectangular stainless steel wrapper plate that is not water tight and as a result the aqueous solution within the poison cavity leaks out into the bulk pool water through the various pathways as the bulk pool water flows into and out of the poison cavity. The silica concentration in the poison cavity is higher than that of the bulk pool silica concentration and increases to a point where there is chemical balance with the bulk pool silica concentration unless the surrounding environment is disturbed. Both the

Florida Power and Light Company L-2009-264 License Amendment Request No. 201 Attachment Unit 4, Supplement 6 Page 14 of 14 physical degradation mechanism just described and that modeled by RACKLIFE are reflective of this process.

The "tab" indicated to be present at the top of the Unit 4 wrapper plate is judged to restrict the flow of water through the poison cavity to a greater extent than that of Unit 3. The other flow paths between the tack welds affixing the wrapper plate to the storage cell wall, the four folded comers at the edges of the wrapper plate, and the small inspection port of the wrapper plate for Region II are otherwise similar due to their similarity in construction. The chemical form of the silica that is measured is reactive silica and is soluble in solution, thus it is not trapped within the poison cavity since it can flow out of and into the poison cavity through the available pathways just mentioned.

NRC Question (2d)

Please describe the factors causing the large differences in predicted Boraflex degradation betweenthe Unit 3 and Unit 4.

FPL Response (2d)

There are two factors that are judged to account for the large differences in the predicted Boraflex degradation between the Unit 3 and Unit 4:

The first factor is due to the differences in the poison cavity flow characteristics due to the difference in the wrapper plate design discussed above in FPL Response 2.c. This is reflected in the Unit 4 RACKLIFE model by lower escape coefficients for the release of silica from the poison cavity to the bulk pool water. The predicted bulk pool silica concentration from the Unit 4 RACKLIFE model is more in line with the measured silica concentration of the Unit 4 pool than that of the Unit 3 RACKLIFE model which predicts a significantly higher bulk pool silica concentration than is measured in the Unit 3 pool. Thus the Unit 3 RACKLIFE model can be expected to predict higher values of Boraflex degradation than the Unit 4 RACKLIFE model.

The second factor is the differences between the times in service for each pool. The Unit 4 pool went into service approximately four years after Unit 3 and the peak gamma radiation dose to the Unit 4 Boraflex panels is lower than that of Unit 3. This is indicative of less degradation in the Unit 4 pool since the release rate of silica in the RACKLIFE model for the Boraflex panels is a function of gamma dose and pool water temperature. Even though the dose profile of the Boraflex panels for both pools may be similar, the differences in the time in service would explain the remaining differences in degradation since the cumulative degradation to any panel is an integral of the silica release rate over time. Thus the Unit 3 RACKLIFE model can be expected to predict higher values of Boraflex degradation than the Unit 4 RACKLIFE model.