L-2009-277, Acceptance Criteria for Emergency Core Cooling Systems for Light Water Nuclear Power Reactors 10 CFR 50.46 Change Report

Acceptance Criteria for Emergency Core Cooling Systems for Light Water Nuclear Power Reactors 10 CFR 50.46 Change Report

ML093480181
Person / Time
Site:	Saint Lucie
Issue date:	11/30/2009
From:	Katzman E Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2009-277
Download: ML093480181 (6)

Text

Florida Power & Light Company, 6501 S. Ocean Drive, Jensen Beach, FL 34957 November 30, 2009 F=PL L-2009-277 10 CFR 50.46 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re: St. Lucie Unit 1 Docket No. 50-335 Acceptance Criteria for Emergency Core Cooling Systems for Light Water Nuclear Power Reactors 10 CFR 50.46 Change Report Florida Power and Light (FPL) was informed of inaccuracies in the large and small break loss of coolant accident (LOCA) analyses. The subsequent calculation that assessed the effects of these issues, along with other previous changes and errors in the accident analysis, resulted in a new peak cladding temperature (PCT) value within the regulatory limit of 2200 'F provided in 10 CFR 50.46. However, the accumulated effect on PCT was greater than 50 'F.

According to 10 CFR 50.46, when a cumulative PCT change in errors or changes to the analysis of 50 'F occurs, a 30 day report shall be sent to the NRC with a proposed schedule for providing reanalysis or taking action as may be needed to show compliance with 50.46 requirements. This information is provided in the attachment to this letter.

Please contact Ken Frehafer at (772) 467-7748 should you have any questions regarding this submittal.

Sincerely, Eric S. Katzman Licensing Manager St. Lucie Plant ESK/KWF Attachment Aoc an FPL Group company

St. Lucie Unit I L-2009-277 Docket No. 50-335 Attachment 10 CFR 50.46 Change Report Page 1 of 5 St. Lucie Unit 1 10 CFR 50.46 30-Day Change Report Emergency core cooling system (ECCS) analyses for St. Lucie Unit 1 is performed by AREVA NP Inc. The following 30-Day report pertaining to the application of the AREVA NP Inc. large break loss of coolant accident (LBLOCA) evaluation model (SEM/PWR-98) and small break loss of coolant accident (SBLOCA) evaluation model (ANF-RELAP) to St. Lucie Unit 1, is provided pursuant to 10 CFR 50.46(a)(3)(ii). A summary of the calculated peak cladding temperature (PCT) changes for LBLOCA and SBLOCA is provided in Tables I and 2, respectively.

1.0 Changes to LBLOCA 1.1 Pellet thermal conductivity degradation with burnup effect on RODEX2 An issue is identified with the RODEX2 code wherein burnup dependent thermal conductivity is not accounted for. The code may under-predict fuel pellet temperatures at burnups beyond approximately 20 GWd/MTU and, therefore, may under-predict the stored energy initial condition for LOCA analyses. The impact on PCT for St. Lucie Unit 1 is estimated to be +200 F.

1.2 Previous LBLOCA PCT changes are documented in References 3.1 and 3.2. Table 1 summarizes the estimated impact of the changes/errors on the St. Lucie Unit 1 LBLOCA PCT. The limiting LBLOCA PCT with the estimated effect of all the changes/errors is 2079' F. With the impact of all changes/errors, St. Lucie Unit 1 LBLOCA PCT of 2079' F continues to comply with the 10 CFR 50.46 acceptance criterion of < 2200' F.

Therefore, no reanalysis is required.

LBLOCA is currently being re-analyzed as part of the ongoing Extended Power Uprate (EPU) project, and is tentatively scheduled to be completed in the first half of Year 2010.

2.0 Changes to SBLOCA

2. .a Error in the radiation heat transfer model The radiation to fluid heat transfer model in ANF-RELAP is identified to have used flawed figure as the basis for determining coefficients for the correlation of emissivity of water vapor. The result is that the radiation to fluid correlation under predicts the radiative heat transfer. This issue was caused by flawed data used within the industry community. The impact on PCT for St. Lucie Unit I is estimated to be -64' F.

St. Lucie Unit I L-2009-277 Docket No. 50-335 Attachment 10 CFR 50.46 Change Report Page 2 of 5 2.1.b Legacy error in the RELAP5 series point kinetics model Previously Idaho National Laboratory (INL) announced an error in the coding of the point kinetics model in RELAP5 series of codes. Recently, INL announced that the previous error corrections were incorrect and that the recommended convergence criteria supplied with those corrections should be retained. ANF-RELAP used in SBLOCA analysis was not modified since it used strict convergence criteria and, as noted by INL, the index corrections were of secondary importance. The estimated impact on PCT for St. Lucie Unit I is +80 F. (This is a retraction of previously reported estimated impact of

-8o F.)

2.1 .c Legacy error in the RELAP5 series heat conduction model INL announced that the heat conduction solution in RELAP5 series of codes is incorrectly programmed. The error is associated with using the incorrect heat capacity when evaluating the right boundary mesh point. Instead of using the last (adjacent) mesh interval heat capacity, the code incorrectly uses the next to last mesh interval heat capacity. The impact is minimized with an increased number of mesh points. SBLOCA methodology guidelines further minimize the effect by requiring close mesh spacing at the left and right boundaries. The impact on PCT for St. Lucie Unit 1 is estimated to be 00 F.

2.1 .d Pellet thermal conductivity degradation with burnup effect on RODEX2 An issue is identified with RODEX2 code wherein burnup dependent thermal conductivity is not accounted for. The code may under-predict fuel pellet temperatures at burnups beyond approximately 20 GWd/MTU and, therefore, may under-predict the stored energy initial condition for LOCA analyses. SBLOCA analysis is insensitive to initial stored energy because sufficient excess cooling capacity exists during the blowdown phase of the transient to effectively remove any excess initial stored energy prior to the extended heatup period when PCT occurs. The estimated impact on PCT of this error for St. Lucie Unit 1 is 00 F.

2.2 Previous SBLOCA PCT changes are documented in References 3.1 and 3.2. Table 2 summarizes the estimated impact of the changes/errors on the St. Lucie Unit I SBLOCA PCT. The limiting SBLOCA PCT with the estimated effect of all the changes/errors is 17020 F. With the impact of all changes/errors, St. Lucie Unit 1 SBLOCA PCT of 17020 F continues to comply with the 10 CFR 50.46 acceptance criterion of < 22000 F.

Therefore, no reanalysis is required.

SBLOCA is currently being re-analyzed as part of the ongoing Extended Power Uprate (EPU) project, and is tentatively scheduled to be completed in the first half of Year 2010.

St. Lucie Unit I L-2009-277 Docket No. 50-335 Attachment 10 CFR 50.46 Change Report Page 3 of 5 3.0 References 3.1 FPL Letter L-2009-061, Eric Katzman to U.S. Nuclear Regulatory Commission Document Control Desk, "St. Lucie Units 1 and 2, Docket Nos. 50-335 and 50-389, Acceptance Criteria for Emergency Core Cooling Systems for Light Water Nuclear Power Reactors 10 CFR 50.46 Annual Report," March 11, 2009.

3.2 FPL Letter L-2008-254, Eric Katzman to U.S. Nuclear Regulatory Commission Document Control Desk, "St. Lucie Unit I Docket No. 50-335 Acceptance Criteria for Emergency Core Cooling Systems for Light Water Nuclear Power Reactors 10 CFR 50.46 Change Report," December 4, 2008.

St. Lucie Unit 1 L-2009-277 Docket No. 50-335 Attachment 10 CFR 50.46 Chanae Renort Page 4 of 5 Table 1: St. Lucie Unit 1 LBLOCA PCT Margin Summary Sheet Day Report Evaluation Model: EMF-2087(P)(A), Revision 0 Evaluation Model PCT: 2005 OF Absolute Net PCT Effect PCT Effect A. Prior 10 CFR Corrections - 50.46 PreviousChanges Years or Error (L-2009-061, r+ APcT 54rF 56F Reference 3.1) ___

B. Prior 10 CFR 50.46 Changes or Error APCT 0°F 0°F Corrections - Year 2009 ' _

C. Current 10 CFR 50.46 Changes

1. Effect of pellet thermal conductivity degradation with bumup not included in APCT + 20°F 20°F RODEX2 D. Absolute Sum of 10 CFR 50.46 Changes APCT 76 0F The sum of the PCTfrom the most recent analysis using an acceptable evaluation model and the estimates of PCT impactfor 2079OF < 2200°F changes and errors identified since this analysis

St. Lucie Unit 1 L-2009-277 Docket No. 50-33 5 Attachment 10 CFR 50.46 Change Report Page 5 of 5 Table 2: St. Lucie Unit 1 SBLOCA PCT Margin Summary Sheet Day Report Evaluation Model: XN-NF-82-49(P)(A), Revision 1, Supplement 1 Evaluation Model PCT: 1765 OF Absolute Net PCT Effect PCT Effect Prior 10 CFR 50.46 Changes or Error A. Corrections - Previous Years (L-2009-061, APCT - 70F I1T Reference 3.1) ',

Prior 10 CFR 50.46 Changes or Error Corrections - Year 2009 PC F ,

C. Current 10 CFR 50.46 Changes

1. Error in the radiation heat transfer model APCT - 64 0 F 64 0F

2. Legacy error in the RELAP5 series point kinetics model

3. Legacy error in the RELAP5 series heat APCT ', 0F ', 0F conduction model C ,

4. Effect of pellet thermal conductivity degradation with burnup not included in 0 APCT 0°F " F RODEX2 ',

D. Absolute Sum of 10 CFR 50.46 Changes APCT 83 0 F The sum of the PCTfrom the most recent analysis using an acceptable evaluation model and the estimates of PCT impactfor 1702°F < 2200°F changes and errorsidentified since this analysis