PNP 2013-046, Updated Palisades Nuclear Plant Reactor Vessel Fluence Evaluation

Updated Palisades Nuclear Plant Reactor Vessel Fluence Evaluation

ML13176A412
Person / Time
Site:	Palisades
Issue date:	06/25/2013
From:	Vitale A Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PNP 2013-046, TAC ME5263 WCAP-15353, Suppl 3, Rev 0
Download: ML13176A412 (21)

Text

Entergy Nuclear Operations, Inc.

Palisades Nuclear Plant Iiterf bY 27780 Blue Star Memorial Highway Covert, Ml 49043-9530 Tel 269 764 2000 Anthony J. Vitale Site Vice President PNP 2013-046 June 25, 2013 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Updated Palisades Nuclear Plant Reactor Vessel Fluence Evaluation Palisades Nuclear Plant Docket 50-255 License No. DPR-20

References:

1. Entergy Nuclear Operations, Inc. letter, Updated Palisades Reactor Vessel Pressurized Thermal Shock Evaluation, dated December 20, 2010 (ADAMS Accession No. ML110060692)

2. NRC letter, Updated Reactor Pressure Vessel Pressurized Thermal Shock Evaluation for Palisades Nuclear Plant (TAC No.

ME5263), dated December 7, 2011 (ADAMS Accession No. ML112870050)

Dear Sir or Madam:

As documented in Reference 1, Entergy Nuclear Operations, Inc. (ENO) submitted an updated reactor vessel pressurized thermal shock (PTS) evaluation for Palisades Nuclear Plant (PNP). The submittal included an updated reactor vessel fluence evaluation, WCAP-1 5353 Supplement I NP, Revision 0, Palisades Reactor Pressure Vessel Fluence Evaluation, that calculated fluence based on actual plant operation through Cycle 20 and the finalized design for Cycle 21, with future fluence based on planned future operations. Using data from the fluence calculation, the PTS evaluation concluded that the PNP reactor vessel would not reach the 10 CFR 50.61 PTS screening criteria limit until April2017, during Cycle 26.

In Reference 2, the Nuclear Regulatory Commission (NRC) concluded that the updated PNP PTS evaluation was in accordance with 10 CFR 50.61 and that the PTS screening criteria limit would not be reached until April 2017.

PNP 2013-046 Page 2 ENO has re-calculated PNP reactor vessel fluence, based on actual reactor operation through Cycle 22, and future fluence based on planned operations through Cycle 26.

This is documented in the attached Palisades Reactor Pressure Vessel Fluence Evaluation, WCAP-1 5353 Supplement 3 NP, Revision 0. The evaluation concludes that the PNP reactor vessel would not reach the 10 CFR 50.61 PTS screening criteria limit until August 2017.

The attachment contains no proprietary information.

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

ENO requests that, by December 31, 2013, the NRC complete review and approval of the attached fluence evaluation, and endorse the new date at which the PNP reactor vessel is estimated to reach the PTS screening criteria limit.

I declare under penalty of perjury that the foregoing is true and correct. Executed on June 25, 2013.

Sincerely, ajv/Jse

Attachment:

1. Palisades Reactor Pressure Vessel Fluence Evaluation, WCAP-1 5353 Supplement 3 NP, Revision 0 cc: Administrator, Region Ill, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC

ATTACHMENT I PALISADES REACTOR PRESSURE VESSEL FLUENCE EVALUATION WCAP-I 5353 SUPPLEMENT 3 NP REVISION 0 18 pages follow

Westinghouse Non-Proprietary Class 3 WCAP-15353 - Supplement 3 - NP June 2013 Revision 0 Palisades Reactor Pressure Vessel Fluence Evaluation

Westinghouse Non-Proprietary Class 3 WCAP-15353 - Supplement 3 - NP, Revision 0 Palisades Reactor Pressure Vessel Fluence Evaluation Stanwood L. Anderson*, Fellow Engineer Radiation Engineering & Analysis June 2013 Reviewed:

Benjamin W. Amiri*, Senior Engineer Radiation Engineering & Analysis Approved:

Laurent P. Houssay*, Acting Manager Radiation Engineering & Analysis Work Performed Under Shop Order 450 Sales Order No. 94483 Prepared by Westinghouse for Entergy Nuclear Operations Inc WESTINGHOUSE ELECTRIC COMPANY LLC 1000 Westinghouse Drive Cranberry Township, PA 16066

© 2013 Westinghouse Electric Company LLC All Rights Reserved

• Electronically approved records are authenticated in the electronic document management system.

Westinghouse Non-Proprietary Class 3 EXECUTIVE

SUMMARY

In early 2000, WCAP-15353, Revision 0[1] describing the methodology used in the fluence evaluations for the Palisades plant was submitted to the NRC staff for review. Following that review and a further exchange of information documented in Reference 2, the methodology described in WCAP-15353, Revision 0 was approved for application to the Palisades reactor pressure vessel[3]. Subsequent to that approval, additional submittals[4,5] in support of the benchmarking of this fluence methodology were reviewed and approved by the NRC Staff as being in compliance with the requirements of Regulatory Guide 1.190[6].

The fluence analysis described in WCAP-15353, Revision 0[1] included cycle-specific evaluations through fuel Cycle 14 (the then-current operating cycle). In mid 2010, Supplement 1 to WCAP-15353, Revision 0[10] was issued to provide an updated neutron fluence assessment for the Palisades pressure vessel that included cycle-specific analysis for additional operating cycles for which the design had been finalized (Cycles 15 through 21). Supplement 1 included fluence projections for future operation through approximately 44 effective full power years (EFPY). The results of the evaluation documented in Supplement 1 were used as input to vessel materials studies that included updates to surveillance capsule credibility analysis, material chemistry factor determination, Pressurized Thermal Shock (PTS) evaluation, and generation of Pressure-Temperature (PT) limit curves.

In December of 2010, Entergy Nuclear Operations Inc submitted a request to revise the Palisades PTS evaluation to include new information on surveillance data for the limiting RPV welds (axial welds) fabricated with weld wire heat number W5214 (Weld W5214). Neutron fluence data documented in Supplement 1 to WCAP-15353, Revision 0[10] were used in support of this submittal. In December of 2011, the request for the revised PTS evaluation was approved by the USNRC Staff[14] and a limiting fluence of 1.685e19 n/cm2 (E > 1.0 MeV) was established for Weld W5214. Based on the fluence projections provided in Supplement 1 to WCAP-15353, Revision 0[10] the limiting fluence was expected to be reached in April 2017.

In this supplement, the neutron fluence accrued by Weld W5214 during cycles 21 through 26 has been re-evaluated based on actual fuel cycle designs, fuel cycle lengths, and refueling outage schedules. The result of that re-evaluation is a movement in the date at which the fluence limit (1.685e19 n/cm2) for Weld W5214 corresponding to the PTS screening criterion of 270° F is anticipated to be reached from April 2017 to August 2017.

WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 i TABLE OF CONTENTS Page TABLE OF CONTENTS i LIST OF TABLES ii LIST OF FIGURES iii

1.0 INTRODUCTION

1-1 2.0 NEUTRON TRANSPORT CALCULATIONS 2-1 2.1 Method of Analysis 2-1 2.2 PTS Limit Re-Evaluation 2-5

3.0 REFERENCES

3-1 WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 ii LIST OF TABLES Table Title Page 2.2-1 Comparison of Fast Neutron Flux Values and Fuel Cycle Lengths used in 2-6 the PTS Limit Analysis - Weld W5214 2.2-2 Comparison of Fast Neutron Fluence Accrued at the Conclusion of 2-7 Cycles 21 through 26 - Weld W5214 2.2-3 Fast Neutron Fluence Accumulation as a Function of Irradiation Time 2-8 During Cycle 26 - Weld W5214 WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 iii LIST OF FIGURES Figure Title Page 2.1-1 Palisades r, Reactor Geometry 2-3 2.1-2 Palisades r,z Reactor Geometry 2-4 WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 1-1 SECTION

1.0 INTRODUCTION

In the assessment of the state of embrittlement of light water reactor (LWR) pressure vessels, an accurate evaluation of the neutron exposure of each of the materials comprising the beltline region of the vessel is required. In Section II F of 10 CFR 50[7] Appendix G, the beltline region is defined as:

the region of the rea ctor vessel shell m aterial (including welds, heat affected zones, and plates or forgings) that directly sur rounds the effective height of the reactor cor e and adja cent region s of the re actor vesse l that are predicted to experience sufficient neutron radiation damage to be considered in the selection of the most limiting material with regard to radiation damage.

Each of the materials that is anticipated to experience a neutron exposure that exceeds this fluence threshold must be considered in the overall embrittlement assessments for the pressure vessel.

Regulatory Guide 1.190, Calculational and Dosimetry Methods for Determining Pressure Vessel Neutron Fluence [6], describes state-of-the-art calculation and measurement procedures that are acceptable to the NRC staff for determining pressure vessel fluence. Also included in Regulatory Guide 1.190 is a discussion of the steps required to qualify and validate the methodology used to determine the neutron exposure of the pressure vessel wall.

In early 2000, WCAP-15353, Revision 0[1] describing the methodology used in the fluence evaluations for the Palisades plant was submitted to the NRC staff for review. Following that review and a further exchange of information documented in Reference 2, the methodology described in WCAP-15353, Revision 0 was approved for application to the Palisades reactor pressure vessel (RPV)[3]. Subsequent to that approval additional submittals[4,5] in support of the benchmarking of this fluence methodology were reviewed and approved by the NRC Staff as being in compliance with the requirements of Regulatory Guide 1.190[6].

The fluence analysis described in WCAP-15353, Revision 0[1] included cycle-specific evaluations through fuel Cycle 14 (the then-current operating cycle). In mid 2010, Supplement 1 to WCAP-15353, Revision 0[10] was issued to provide an updated neutron fluence assessment for the Palisades pressure vessel that included cycle-specific analysis for additional operating cycles for which the design had been finalized (Cycles 15 through 21). At that time, Cycle 21 was in operation, but not completed.

WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 1-2 Supplement 1 to WCAP-15353, Revision 0[10] included fluence projections for future operation through approximately 44 effective full power years (EFPY). The results of the evaluation documented in Supplement 1 were used as input to vessel materials studies that included updates to surveillance capsule credibility analysis, material chemistry factor determination, Pressurized Thermal Shock (PTS) evaluation, and generation of Pressure-Temperature (PT) limit curves.

In December of 2010, Entergy Nuclear Operations Inc submitted a request to revise the Palisades PTS evaluation to include new information on surveillance data for the limiting RPV welds (axial welds 2-112A/C & 3-112A/C) fabricated with weld wire heat number W5214 (Weld W5214). Neutron fluence data documented in Supplement 1 to WCAP-15353, Revision 0[10]

were used in support of this submittal. In December of 2011, the request for the revised PTS evaluation was approved by the USNRC Staff[14] and a limiting fluence of 1.685e19 n/cm2 (E > 1.0 MeV) was established for Weld W5214 corresponding to when the PTS screening criterion of 270° F would be reached. Based on the fluence data provided in Supplement 1 to WCAP-15353, Revision 0[10] the limiting fluence was expected to be reached in April 2017. This date corresponds to a time during operation of Palisades Cycle 26.

Since the approval of the revised PTS evaluation, Cycles 21 and 22 have been completed and a design for Cycle 23 has been implemented and is currently in operation. Therefore, it became possible to evaluate the neutron fluence accrued during these fuel cycles based on the more accurate data obtained from actual rather than projected reactor operation.

In this supplement, the neutron fluence accrued by the limiting Weld W5214 during Cycles 21 through Cycle 26 is re-evaluated using revised neutron flux calculations and fuel cycle lengths and based on this re-evaluation an updated time at which the PTS screening limit will be reached is determined.

WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 2-1 SECTION 2.0 NEUTRON TRANSPORT CALCULATIONS As noted in Section 1.0 of this report, the exposure of the Palisades pressure vessel was developed based on a series of fuel cycle-specific neutron transport calculations validated by comparison with plant-specific measurements. Measurement data used in the validation process were obtained from both in-vessel and ex-vessel capsule irradiations. These comparisons along with the benchmarking information described in References 4 and 5 demonstrate that the transport methodology provides results that meet the requirements of Regulatory Guide 1.190[6]. In this section, the neutron transport methodology is discussed in some detail, and the calculated results applicable to the PTS limit re-evaluation are provided.

2.1 - Method of Analysis In performing the fast neutron exposure evaluations for the Palisades reactor, plant-specific forward transport calculations were carried out using the three-dimensional flux synthesis technique described in Section 1.3.4 of Regulatory Guide 1.190. In particular, the following single channel synthesis approach was employed for all fuel cycles:

(r, z )

(r, , z) = (r, ) *

(r )

where (r,,z) is the synthesized three-dimensional neutron flux distribution, (r,) is the transport solution in r, geometry, (r,z) is the two-dimensional solution for a cylindrical reactor model using the actual axial core power distribution, and (r) is the one-dimensional solution for a cylindrical reactor model using the same source-per-unit-height as that used in the r, two-dimensional calculation.

For the Palisades analysis, all of the transport calculations were carried out using the DORT two-dimensional discrete ordinates code Version 3.2[8] and the BUGLE-96 cross section library[9]. The BUGLE-96 library provides a 67-group coupled neutron-gamma ray cross-section data set produced specifically for light water reactor applications. In these analyses, anisotropic scattering was treated with a P5 Legendre expansion and the angular discretization was modeled with an S16 order of angular quadrature. Energy and space dependent core power distributions as well as system operating conditions were treated on a fuel cycle-specific basis.

The geometry used for the Palisades transport analysis is discussed in some detail in Reference 1 and the geometric model established for Cycle 15 and beyond was also used for the current evaluations. A plan view of the r, model of the reactor geometry at the core midplane is shown in Figure 2.1-1. This model depicts a single quadrant of the reactor. A WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 2-2 section view of the r,z model of the Palisades reactor is shown in Figure 2.1-2. The r,z model extended radially from the centerline of the reactor core out to a location interior to the primary biological shield and over an axial span from an elevation one foot below the active fuel to an axial elevation one foot above the active fuel. The one-dimensional radial model used in the synthesis procedure consisted of the same radial mesh intervals included in the r,z model.

Thus, radial synthesis factors could be determined on a meshwise basis throughout the entire geometry.

The core power distributions used in the plant-specific transport analysis for the reactor were provided by Entergy[11]. The data used in the source generation included fuel assembly-specific initial enrichments, beginning-of-cycle burnups and end-of-cycle (EOC) burnups. Appropriate axial burnup distributions were also used.

For each fuel cycle of operation, the fuel assembly-specific enrichment and burnup data were used to generate the spatially dependent neutron source throughout the reactor core. This source description included the spatial variation of isotope-dependent (U-235, U-238, Pu-239, Pu-240, Pu-241, and Pu-242) fission spectra, neutron emission rate per fission, and energy release per fission based on the burnup history of individual fuel assemblies. These fuel assembly-specific neutron source strengths derived from the detailed isotopics were then converted from fuel pin Cartesian coordinates to the [r,], [r,z], and [r] spatial mesh arrays used in the DORT discrete ordinates calculations.

WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 2-3 Figure 2.1-1 Palisades r, Reactor Geometry WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 2-4 Figure 2.1-2 Palisades r,z Reactor Geometry WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 2-5 2.2 - PTS Limit Re-evaluation The limiting RPV axial welds (Weld W5214) are exposed to the neutron flux characteristic of the 60° azimuthal location. A summary of the neutron flux and cycle time data used in both the prior analysis and the current re-evaluation is given in Table 2.2-1. Note that the updated data include new neutron flux values for Cycles 21, 22, and 23, as well as new cycle lengths for Cycles 21, 22, 23, and 24. The projected neutron flux for Cycles 24, 25, and 26 and the projected cycle lengths for Cycles 25 and 26 remain the same as those used in Reference 10.

The updated data included in Table 2.2-1 were provided via References 11 through 13.

In Table 2.2-2, a comparison of the calculated neutron fluence at the end of Cycles 20 through Cycle 26 is given for both the prior analysis and the current re-evaluation. From Table 2.2-2, it is noted that, in both cases, the limiting weld fluence of 1.685e19 n/cm2 is reached during Cycle 26.

In Table 2.2-3, the accrued neutron fluence at the limiting Weld (W5214) is provided as a function of irradiation time through Cycle 26 for the updated irradiation conditions. In developing this exposure profile, Cycle 26 was assumed to initiate at 11:00 on November 15, 2016 and to run at 100% capacity during the cycle up to the point at which the limiting fluence is reached.

Based on these projections, the limiting fluence at Weld W5214 is calculated to be reached after 11.99 days of irradiation in August 2017.

WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 2-6 Table 2.2-1 Comparison of Fast Neutron Flux Values and Fuel Cycle Lengths used in the PTS Limit Analysis Weld W5214 Reference 10 Current Analysis Cycle Flux1 Cycle Time Cycle Flux1 Cycle Time Cycle [n/cm2-s] [EFPD] [n/cm2-s] [EFPD]

21 1.172e10 519 1.169e10 508 22 1.128e10 499 1.101e10 495 23 1.172e10 499 1.021e10 527 24 1.172e10 477 1.172e10 4202 25 1.172e10 504 1.172e10 504 26 1.172e10 504 1.172e10 504 1- Limiting RPV axial welds (Weld W5214) are exposed to the neutron flux characteristic of the 60° azimuthal location.

2 - Cycle 24 length is based upon a spring 2015 refueling outage. That outage might be changed to Fall 2015 and the subsequent refueling outages delayed to maintain 18-month refueling cycles. Three refueling outages are still planned before reaching the limiting fluence.

WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 2-7 Table 2.2-2 Comparison of Fast Neutron Fluence Accrued at the Conclusion of Cycles 21 Through 26 Weld W5214 Reference 10 Current Analysis Cumulative Cumulative Cycle Exposure EOC Exposure EOC Time Fluence1 Time Fluence1

[EFPY] [n/cm2] [EFPY] [n/cm2]

20 22.0 1.419e19 22.0 1.419e19 21 23.4 1.472e19 23.3 1.471e19 22 24.7 1.520e19 24.7 1.518e19 23 26.1 1.571e19 26.1 1.564e19 24 27.4 1.619e19 27.3 1.607e19 25 28.8 1.670e19 28.7 1.658e19 26 30.2 1.721e19 30.1 1.709e19 1- Limiting RPV axial welds (Weld W5214) are exposed to the neutron flux characteristic of the 60° azimuthal location.

WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 2-8 Table 2.2-3 Fast Neutron Fluence Accumulation as a Function of Irradiation Time During Cycle 26 Weld W5214 Current Analysis Monthly Month Exposure Accumulated Time Fluence

[EFPD] [n/cm2]

Nov. 2016 14.54 1.659e19 Dec. 2016 31 1.662e19 Jan. 2017 31 1.665e19 Feb. 2017 28 1.668e19 Mar. 2017 31 1.671e19 Apr. 2017 30 1.674e19 May 2017 31 1.678e19 Jun. 2017 30 1.681e19 Jul. 2017 31 1.684e19 Aug. 2017 11.99 1.685e19 Notes: 1 - Assumed Cycle Start Nov. 11/15/2016 at 11:00 2 - Cycle flux = 1.172e10 n/cm2-s (E > 1.0 MeV) 3 - Cycle 26 Capacity Factor is assumed to be 100% to the point at which the limiting fluence is reached.

WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013

Westinghouse Non-Proprietary Class 3 3-1 SECTION

3.0 REFERENCES

1. WCAP-15353, Revision 0, Palisades Reactor Pressure Vessel Neutron Fluence Evaluation, G. K. Roberts et al., January 2000.

2. LTR-REA-00-630, Transmittal of Responses to Requests for Additional Information on WCAP-15353 in Support of the Palisades Pressure Vessel Fluence Evaluation, G. K. Roberts, July 13, 2000.

3. NRC Safety Evaluation Report (SER), Darl S. Hood (NRC) to Nathan L. Haskell (Palisades), Palisades Plant - Reactor Vessel Neutron Fluence Evaluation and revised Schedule for Reaching Pressurized Thermal Shock Screening Criteria, November 14, 2000.

4. WCAP-14040-NP-A, Revision 4, Methodology Used to Develop Cold Overpressure Mitigating System Setpoints and RCS Heatup and Cooldown Limit Curves, May 2004.

5. WCAP-16083-NP-A, Revision 0, Benchmark Testing of the FERRET Code for Least Squares Evaluation of Light Water Reactor Dosimetry, S. L. Anderson, May 2006.

6. Regulatory Guide 1.190, Calculational and Dosimetry Methods for Determining Pressure Vessel Neutron Fluence, U. S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, March 2001.

7. Code of Federal Regulations Title 10 Part 50, Domestic Licensing of Production and Utilization Facilities, Appendix G, Fracture Toughness Requirements and Appendix H, Reactor Vessel Materials Surveillance Requirements, January 1992.

8. CCC-650, DOORS 3.2, One-, Two-, and Three-Dimensional Discrete Ordinates Neutron/Photon Transport Code System, April 1998. Available from the Radiation Safety Information Computational Center, Oak Ridge National Laboratory.

9. DLC-185, BUGLE-96, Coupled 47 Neutron, 20 Gamma-Ray Group Cross Section Library Derived from ENDF/B-VI for LWR Shielding and Pressure Vessel Dosimetry Applications, March 1996. Available from the Radiation Safety Information Computational Center, Oak Ridge National Laboratory.

10. WCAP-15353, Supplement 1 - NP, Palisades Reactor Pressure Vessel Fluence Evaluation, Stanwood L. Anderson, May 2010.

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Westinghouse Non-Proprietary Class 3 3-2

11. Palisades Design Input Record for Input to a Contingent Calculation, Thomas W. Allen, May 20, 2013.

12. Westinghouse Project Letter CPAL-11-20, Pressure Vessel Flux Update - Cycles 21 and 22, Edward P. Shields, July 29, 2011.

13. Westinghouse Project Letter CPAL-12-14, Pressure Vessel Inner Radius Fluence Following Cycle 23, Anthony L. Dietrich, August 21,2012.

14. NRC Safety Evaluation Report (SER), Mahesh Chawla (NRC) to Vice President Operations, Entergy Nuclear Operations Inc, Palisades Nuclear Plant, Updated Reactor Pressure Vessel Pressurized Thermal Shock Evaluation for Palisades Nuclear Plant (TAC NO. ME5263), December 7, 2011.

WCAP-15353 - Supplement 3 - NP, Revision 0 June 2013