PNP 2014-046, 30-Day Report of Changes in Emergency Core Cooling System Models

30-Day Report of Changes in Emergency Core Cooling System Models

ML14128A272
Person / Time
Site:	Palisades
Issue date:	05/08/2014
From:	Gustafson O Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PNP 2014-046
Download: ML14128A272 (6)

Text

Entelgy Pahsades Nuclear Plant 27780 Blue Star Memorial Highway Covert, Ml 49043-9530 Tel 269 764 2000 Otto W. Gustatson Director, Regulatory and Performance Improvement PNP 2014-046 May 8, 2014 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

30-Day Report of Changes in Emergency Core Cooling System Models Palisades Nuclear Plant Docket 50-255 License No. DPR-20

Dear Sir or Madam:

Entergy Nuclear Operations, Inc. (ENO) is submitting this 30-day report of changes in the emergency core cooling system models for the Palisades Nuclear Plant (PNP). The report is submitted in accordance with 10 CFR 50.46(a)(3)(ii). ENO was notified of these changes by a letter from AREVA dated April 9, 2014. The AREVA letter documented a significant change in small break loss of coolant accident (SBLOCA) peak cladding temperature (PCT) of greater than 50 °F as a result of an evaluation in AREVA Condition Report 2012-8371. This change impacts the PNP SBLOCA and large break loss of coolant accident (LBLOCA) analyses of record.

AREVA Condition Report 2012-8371 was written to address a potential non-conservatism in the Thermal-Hydraulic Test Facility (THTF) assessment supporting S-RELAP5 LOCA analyses. Evaluation found that the correlation for vapor absorptivity used in S-RELAP5 was being applied outside of its intended range of applicability.

The impact of the non-conservatism on the previous LBLOCA calculated PCT analysis is estimated to be 0°F, and the impact on the previous SBLOCA calculated PCT analysis is estimated to be 73 °F. Summaries of the cumulative PCT impacts, and a description of the changes, are provided in the attachments. Although the change in SBLOCA PCT is different by more than 50 °F from the PCT from the previous analysis, and the sum of the absolute magnitudes of the temperature changes for the SBLOCA PCT since the last acceptable model is greater than 50 °F, a SBLOCA reanalysis is not considered necessary because the sum total of the PCT cumulative adjustments since the last acceptable model is less than 50 °F. Therefore, PNP continues to meet PNP 2014-046 May 8,2014 U. S. Nuclear Regulatory Commission AnN: Document Control Desk Washington, DC 20555-0001 Entergy Nuclear Operations, Inc.

Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043-9530 Tel 269 764 2000 Otto W. Gustafson Director, Regulatory and Performance Improvement

Subject:

30-Day Report of Changes in Emergency Core Cooling System Models Palisades Nuclear Plant Docket 50-255 License No. DPR-20

Dear Sir or Madam:

Entergy Nuclear Operations, Inc. (ENO) is submitting this 30-day report of changes in the emergency core cooling system models for the Palisades Nuclear Plant (PNP). The report is submitted in accordance with 10 CFR 50.46(a)(3)(ii). ENO was notified of these changes by a letter from AREVA dated April 9, 2014. The AREVA letter documented a significant change in small break loss of coolant accident (SBLOCA) peak cladding temperature (PCT) of greater than 50 of as a result of an evaluation in AREVA Condition Report 2012-8371. This change impacts the PNP SBLOCA and large break loss of coolant accident (LBLOCA) analyses of record.

AREVA Condition Report 2012-8371 was written to address a potential non-conservatism in the Thermal-Hydraulic Test Facility (THTF) assessment supporting S-RELAP5 LOCA analyses. Evaluation found that the correlation for vapor absorptivity used in S-RELAP5 was being applied outside of its intended range of applicability.

The impact of the non-conservatism on the previous LBLOCA calculated PCT analysis is estimated to be 0 of, and the impact on the previous SBLOCA calculated PCT analysis is estimated to be 73 of. Summaries of the cumulative PCT impacts, and a description of the changes, are provided in the attachments. Although the change in SBLOCA PCT is different by more than 50 of from the PCT from the previous analysis, and the sum of the absolute magnitudes of the temperature changes for the SBLOCA PCT since the last acceptable model is greater than 50 of, a SBLOCA reanalysis is not considered necessary because the sum total of the PCT cumulative adjustments since the last acceptable model is less than 50 of. Therefore, PNP continues to meet

PNP 2014-046 Page 2 of 2 continues to meet 10 CFR 50.46 PCT requirements. ENO does not plan on performing a reanalysis to incorporate the changes. contains the LBLOCA PCT cumulative impact summary. Attachment 2 contains the SBLOCA PCT cumulative impact summary. Attachment 3 contains a more detailed description of the changes.

This letter contains no new commitments and no revisions to existing commitments.

Sincerely, owgljse Attachments:

1. Large Break Loss of Coolant Accident Peak Cladding Temperature Cumulative Impact Summary 2: Small Break Loss of Coolant Accident Peak Cladding Temperature Cumulative Impact Summary

3. Description of Changes CC Administrator, Region Ill, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC PNP 2014-046 Page 2 of 2 continues to meet 10 CFR 50.46 PCT requirements. ENO does not plan on performing a reanalysis to incorporate the changes. contains the LBLOCA PCT cumulative impact summary. Attachment 2 contains the SBLOCA PCT cumulative impact summary. Attachment 3 contains a more detailed description of the changes.

This letter contains no new commitments and no revisions to existing commitments.

Sincerely, owg/jse Attachments:

1. Large Break Loss of Coolant Accident Peak Cladding Temperature Cumulative Impact Summary 2: Small Break Loss of Coolant Accident Peak Cladding Temperature Cumulative Impact Summary

3. Description of Changes CC Administrator, Region III, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC

ATTACHMENT 1 LARGE BREAK LOSS OF COOLANT ACCIDENT PEAK CLADDING TEMPERATURE

SUMMARY

zPCT (°F)

PCT (°F)

PCT (Last Acceptable Model Results) New Cycle 21 Analysis 1740 10 CFR_50.46_Changes Condition Report (CR) 2009-337

- S-RELAP5 Radiation to

-27 1713 Fluid Correlation Under Predicts the Radiative Heat Transfer PCT (2009 Annual Report) 1713 10 CFR_50.46_Changes CR 2009-2309

- S-RELAP5 Kinetics and Heat

-22 1691 Conduction_Model PCT (2010 Annual Report) 1691 PCT (2011 Annual Report) 1691 10 CFR_50.46_Changes CR 201 1-71 55

- S-RELAP5 Sleicher-Rouse Correlation

+8 PCT (2012 Annual and 30-Day Report) 1699 PCT (2013 Annual Report) 1699 10 CFR_50.46_Changes CR 201 3-4230 - S-RELAP5 routine associated with the

+6 1705 RODEX3a_fuel_rod_model_in_the_code.

PCT (2014 30-Day Report) 1705 10 CFR_50.46_Changes CR 2012-8371

- S-RELAP5 vapor absorptivity correlation 0

1705 Sum Total of PCT Adjustments

-35 Page 1 of 1 ATTACHMENT 1 LARGE BREAK LOSS OF COOLANT ACCIDENT PEAK CLADDING TEMPERATURE

SUMMARY

APCTCOF)

PCT JLast Acceptable Model Results) New Cycle 21 Analysis 10 CFR 50.46 Changes Condition Report (CR) 2009-337 - S-RELAP5 Radiation to

-27 Fluid Correlation Under Predicts the Radiative Heat Transfer PCT _(2009 Annual Report) 10 CFR 50.46 Changes CR 2009-2309 - S-RELAP5 Kinetics and Heat

-22 Conduction Model PCT (2010 Annual Report)

PCT (2011 Annual Report) 10 CFR 50.46 Changes CR 2011-7155 - S-RELAP5 Sieicher-Rouse Correlation

+8 PCT (2012 Annual and 30-Day Report)

PCT (2013 Annual Report) 10 CFR 50.46 Changes CR 2013-4230 - S-RELAP5 routine associated with the

+6 RODEX3a fuel rod model in the code.

PCT (2014 30-Day Report) 10 CFR 50.46 Changes CR 2012-8371 - S-RELAP5 vapor absorptivity correlation 0

Sum Total of PCT Adjustments

-35 Page 1 of 1 PCT COF) 1740 1713 1713 1691 1691 1691 1699 1699 1705 1705 1705

ATTACHMENT 2 SMALL BREAK LOSS OF COOLANT ACCIDENT PEAK CLADDING TEMPERATURE

SUMMARY

APCT (°F)

PCT (°F)

PCT (Last Acceptable Model Results) New Cycle 21 Analysis 1734 10 CFR_50.46_Changes CR 2009-337

- S-RELAP5 Radiation to

-64 Fluid_Correlation_Under_Predicts_the_Radiative_Heat_Transfer PCT (2009 Annual Report) 1670 10 CFR_50.46_Changes CR 2009-2309

- S-RELAP5 Kinetics Model

+4 PCT (2009 30-Day Report) 1674 PCT (2010 Annual Report) 1674 PCT (2011 Annual Report) 1674 10 CFR_50.46_Changes CR2011 -7155

- S-RELAP5 Sleicher-Rouse Correlation

-3 PCT (2012 Annual and 30-Day Report) 1671 PCT (2013 Annual Report) 1671 PCT (2014 30-Day Report) 10 CFR_50.46_Changes CR 201 2-8371

- S-RELAP5 vapor absorptivity correlation

+73 1744 Sum Total of PCT Adjustments

+10 Page 1 of 1 ATTACHMENT 2 SMALL BREAK LOSS OF COOLANT ACCIDENT PEAK CLADDING TEMPERATURE

SUMMARY

APCTeF)

PCT (Last Acceptable Model Results) New Cycle 21 Analysis 10 CFR 50.46 Changes CR 2009-337 - S-RELAP5 Radiation to

-64 Fluid Correlation Under Predicts the Radiative Heat Transfer PCT (2009 Annual Report) 10 CFR 50.46 Changes CR 2009-2309 - S-RELAP5 Kinetics Model

+4 PCT (2009 30-0ay Report)

PCT (2010 Annual Report)

PCT (2011 Annual Report) 10 CFR 50.46 Changes CR 2011-7155 - S-RELAP5 Sieicher-Rouse Correlation

-3 PCT (2012 Annual and 30-0ay Report)

PCT (2013 Annual ReporU PCT (2014 3Q-Oay Report) 10 CFR 50.46 Changes CR 2012-8371 - S-RELAP5 vapor absorptivity correlation

+73 Sum Total of PCT Adjustments

+10 Page 1 of 1 PCTeF) 1734 1670 1674 1674 1674 1671 1671 1744

ATTACHMENT 3 DESCRIPTION OF CHANGES AREVA Condition Report 2012-8371, Potential Non-Conservatism in THTF Assessment Supporting S-RELAP5 Analyses While preparing an update of the boiling water reactor (BWR) loss of coolant accident (LOCA) Appendix K methodology using S-RELAP5, AREVA reviewed the Thermal-Hydraulic Test Facility (THTF) level swell assessment for BWR for rod wall temperatures and determined it to be non-conservative relative to the data. This observation was unexpected since other assessments (including the THTF steady state and reflood tests) showed good or conservative agreement. The issue was discovered as part of a proactive response to discussions with the NRC. The THTF facility, operated by Oak Ridge National Laboratory, is a large high pressure thermal-hydraulic loop with nonnuclear (electrically heated) rods simulating a nuclear fuel bundle. The facility is designed to simulate the thermal hydraulic environments expected during pressurized water reactor (PWR) small break loss of coolant accident (SBLOCA) events. Some of the phenomena simulated are applicable as well to the PWR large break loss of coolant accident (LBLOCA).

Further investigation found that the correlation for vapor absorptivity used in S-RELAP5 was being applied outside of its intended range of applicability (no limit on the pressure at which the correlation was applied).

The vapor absorptivity correlation applied to the S-RELAP5 based methodologies is provided in the S-RELAP5 Models and Correlation Code Manual (Reference 1, page 4-41). The equation used for the absorption coefficient of vapor contains the term of the pressure which needs to be truncated in order to obtain the correct emissivity values for an optically thick steam. The applicability of the pressure limit is described in literature by S.S. Penner (Reference 2). No lower pressure limit on the vapor absorptivity correlation is required as the correlation is developed for optically thin gases, which already applies at low pressures.

Results show that limiting the vapor absorptivity correlation to within its intended pressure range allows S-RELAP5 to predict the wall temperatures for THTF within the uncertainty bands or above the uncertainty bands (conservative).

A development version of S-RELAP5 was prepared containing the pressure limit for the calculation of the vapor absorptivity in order to assess the impact on the current analysis of record for SBLOCA. The peak cladding temperature (PCT) increase was developed by comparing the analysis of record after the Sleicher-Rouse error correction with the new PCT results obtained with the corrected version of S-RELAP5. The limiting case and multiple break sizes around the limiting case were rerun with the developmental code version of S-RELAP5.

Page 1 of 2 ATTACHMENT 3 DESCRIPTION OF CHANGES AREVA Condition Report 2012-8371, "Potential Non-Conservatism in THTF Assessment Supporting S-RELAP5 Analyses" While preparing an update of the boiling water reactor (BWR) loss of coolant accident (LOCA) Appendix K methodology using S-RELAPS, AREVA reviewed the Thermal-Hydraulic Test Facility (THTF) level swell assessment for BWR for rod wall temperatures and determined it to be non-conservative relative to the data. This observation was unexpected since other assessments (including the THTF steady state and reflood tests) showed good or conservative agreement. The issue was discovered as part of a proactive response to discussions with the NRC. The THTF facility, operated by Oak Ridge National Laboratory, is a large high pressure thermal-hydraulic loop with nonnuclear (electrically heated) rods simulating a nuclear fuel bundle. The facility is designed to simulate the thermal hydraulic environments expected during pressurized water reactor (PWR) small break loss of coolant accident (SBLOCA) events. Some of the phenomena simulated are applicable as well to the PWR large break loss of coolant accident (LBLOCA).

Further investigation found that the correlation for vapor absorptivity used in S-RELAPS was being applied outside of its intended range of applicability (no limit on the pressure at which the correlation was applied).

The vapor absorptivity correlation applied to the S-RELAPS based methodologies is provided in the S-RELAPS Models and Correlation Code Manual (Reference 1, page 4-41). The equation used for the absorption coefficient of vapor contains the term of the pressure which needs to be truncated in order to obtain the correct emissivity values for an optically thick steam. The applicability of the pressure limit is described in literature by S.S. Penner (Reference 2). No lower pressure limit on the vapor absorptivity correlation is required as the correlation is developed for optically thin gases, which already applies at low pressures.

Results show that limiting the vapor absorptivity correlation to within its intended pressure range allows S-RELAPS to predict the wall temperatures for THTF within the uncertainty bands or above the uncertainty bands (conservative).

A development version of S-RELAPS was prepared containing the pressure limit for the calculation of the vapor absorptivity in order to assess the impact on the current analysis of record for SBLOCA. The peak cladding temperature (PCT) increase was developed by comparing the analysis of record after the Sieicher-Rouse error correction with the new PCT results obtained with the corrected version of S-RELAPS. The limiting case and multiple break sizes around the limiting case were rerun with the developmental code version of S-RELAPS.

Page 1 of 2

For the realistic LBLOCA (RLBLOCA), single phase steam only exists for a very limited time just before the beginning of reflood. During the majority of the blowdown phase and during the entire reflood phase, which are the important RLBLOCA phases, the core is in a dispersed flow regime. The S-RELAP5 methodology uses the Full-Length Emergency Core Heat Transfer for the Separate Effects and Systems Effects Tests (FLECHT-SEASET) reflood tests to determine the heat transfer bias and uncertainty under these conditions.

In addition, the transient progression is very quick and the system depressurizes in the first few seconds after the break opening. Due to the fast depressurization, the amount of time that the correlation for vapor absorptivity used in RLBLOCA is applied outside of the range of applicability is limited and therefore the results predicted in the analysis of record remain valid.

The estimated impact of this change on the Palisades SBLOCA analysis calculated peak cladding temperature is +73 °F, leading to a new calculated PCT of 1744 °F.

The estimated impact of this change on the Palisades RLBLOCA analysis calculated peak cladding temperature is 0 °F.

References 1.

AREVA Document EMF-21 00(P), S-RELAP5 Models and Correlation Code Manual, Revision 16.

2.

S. S Penner, Quantitative Molecular Spectroscopy and Gas Emissivities, Addison Wesley Publishing Company, Inc.

Page 2 of 2 For the realistic LBLOCA (RLBLOCA), single phase steam only exists for a very limited time just before the beginning of reflood. During the majority of the b'lowdown phase and during the entire reflood phase, which are the important RLBLOCA phases, the core is in a dispersed flow regime. The S-RELAP5 methodology uses the Full-Length Emergency Core Heat Transfer for the Separate Effects and Systems Effects Tests (FLECHT-SEASET) reflood tests to determine the heat transfer bias and uncertainty under these conditions.

In addition, the transient progression is very quick and the system depressurizes in the first few seconds after the break opening. Due to the fast depressurization, the amount of time that the correlation for vapor absorptivity used in RLBLOCA is applied outside of the range of applicability is limited and therefore the results predicted in the analysis of record remain valid.

The estimated impact of this change on the Palisades SBLOCA analysis calculated peak cladding temperature is +73 of, leading to a new calculated PCT of 1744 of.

, The estimated impact of this change on the Palisades RLBLOCA analysis calculated peak cladding temperature is 0 of.

References

1.

AREVA Document EMF-2100(P), "S-RELAP5 Models and Correlation Code Manual," Revision 16.

2.

S. S Penner, "Quantitative Molecular Spectroscopy and Gas Emissivities,"

Addison Wesley Publishing Company, Inc.

Page 2 of 2