CNL-17-112, Revision to Reactor Vessel Surveillance Capsule Withdrawal Schedule

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Revision to Reactor Vessel Surveillance Capsule Withdrawal Schedule
ML17248A420
Person / Time
Site: Watts Bar Tennessee Valley Authority icon.png
Issue date: 09/05/2017
From: James Shea
Tennessee Valley Authority
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-17-112
Download: ML17248A420 (11)
v • d • e


Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-17-112 September 5, 2017 10 CFR 50.4 10 CFR 50 Appendix H ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391

Subject:

Revision to Watts Bar Nuclear Plant, Unit 2, Reactor Vessel Surveillance Capsule Withdrawal Schedule

Reference:

1. American Society for Testing and Materials (ASTM) E-185-82, "Standard Practice for Conducting Surveillance Tests for Light-Water Cooled Nuclear Power Reactor Vessels," dated July 1, 1982
2. Administrative Letter 97-04, "NRC Staff Approval for Changes to 10 CFR Part 50, Appendix H, Reactor Vessel Surveillance Specimen Withdrawal Schedules," dated September 30, 1997 Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Appendix H, "Reactor Vessel Material Surveillance Program Requirements," Paragraph III.B.3, Tennessee Valley Authority (TVA) is requesting Nuclear Regulatory Commission (NRC) approval of the enclosed revision to the reactor vessel surveillance capsule removal schedule for Watts Bar Nuclear Plant (WBN) Unit 2. As noted in Table 4.0-1 of the WBN Unit 2 Pressure Temperature Limits Report (PTLR) (Appendix B to TVA System Description Document SDD-N3-68-4001, Reactor Coolant System), reactor vessel surveillance capsule U was scheduled to be removed during the first WBN Unit 2 refueling outage (U2R1) scheduled for October 2017. This planned removal was based on the capsule fluence exceeding 0.50E19 n/cm2 in accordance with Table 1 of American Society for Testing and Materials (ASTM) E-185-82, "Standard Practice for Conducting Surveillance Tests for Light-Water Cooled Nuclear Power Reactor Vessels" (Reference 1).

However, due to the current WBN Unit 2 operating schedule, the recommended fluence value of at least 0.50E19 n/cm2 will not be achieved until the end of cycle 2 for WBN Unit 2.

Therefore, TVA requests NRC approval to revise the withdrawal schedule for capsule U from the U2R1 outage to the U2R2 outage (Spring 2019).

U. S. Nuclear Regulatory Commission CNL-17-112 Page 2 September 5, 2017 to this letter provides the technical justification for this proposed revision to the WBN Unit 2 reactor vessel surveillance capsule withdrawal schedule. Enclosure 2 provides a proposed revision to the WBN Unit 2 PTLR reflecting the proposed revised capsule withdrawal schedule. In accordance with WBN Unit 2 Technical Specification 5.9.6, "Reactor Coolant System (RCS) PRESSURE AND TEMPERATURE LIMITS REPORT (PTLR)," TVA will submit the actual revised WBN Unit 2 PTLR to NRC following NRC approval of the proposed revision to the WBN Unit 2 reactor vessel surveillance capsule withdrawal schedule.

NRC Administrative Letter (AL) 97-04 (Reference 2) clarified the submittal requirements of 10 CFR 50, Appendix H. As stated in AL 97-04, " ... as long as the plant's withdrawal schedule change meets the applicable ASTM standard, the plant will not be exceeding the operating authority already granted in its license. Therefore, a license amendment would not be required, although prior NRC approval to verify conformance with the ASTM standard is required by 10 CFR 50, Appendix H." ASTM E-185-82 is the applicable standard for WBN Unit 2 in accordance with Section 5.2.4.3 of the WBN dual-unit Updated Final Safety Analysis Report (UFSAR). Because the proposed change described in the enclosure to this letter satisfies the requirements of ASTM E-185-82, TVA has determined that a license amendment is not required, which is consistent with the guidance of AL 97-04. lists the new regulatory commitment associated with this submittal. TVA requests NRC approval of the proposed withdrawal schedule by November 17, 2017 (i.e., one week prior to the scheduled end of the WBN U2R1 outage), to allow reactor vessel surveillance capsule U to remain inserted in the core beyond the upcoming WBN Unit 2 refueling outage. Please address any questions regarding this request to Ed Schrull at 423-7 51-3850.

ctfull~

. Shea President, Nuclear Regulatory Affairs and Support Services cc (see Page 3)

Enclosures:

1. Proposed Revision to the Watts Bar Nuclear Plant (WBN) Unit 2, Reactor Vessel Surveillance Program
2. Proposed Revised WBN Unit 2 Pressure Temperature Limits Report
3. New Regulatory Commitment

U. S. Nuclear Regulatory Commission CNL-17-112 Page 3 September 5, 2017 cc (Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant

Enclosure 1

Subject:

Proposed Revision to the Watts Bar Nuclear Plant (WBN) Unit 2, Reactor Vessel Surveillance Program CONTENTS 1.0 Introduction ..................................................................................................................... 2 2.0 Current Program / Withdrawal Schedule.......................................................................... 2 3.0 Changes to Program / Withdrawal Schedule ................................................................... 3 4.0 Justification ..................................................................................................................... 3 5.0 Precedent ........................................................................................................................ 5 6.0 References ...................................................................................................................... 6 CNL-17-112 E1-1 of 6

Enclosure 1

1.0 INTRODUCTION

Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Appendix H, "Reactor Vessel Material Surveillance Program Requirements," describes reactor vessel material surveillance program requirements. Paragraph III.B.3 of 10 CFR 50, Appendix H states that a proposed material withdrawal schedule must be submitted with a technical justification per 10 CFR 50.4, and approved prior to implementation.

Accordingly, Tennessee Valley Authority (TVA) is requesting Nuclear Regulatory Commission (NRC) approval of the enclosed revision to the reactor vessel surveillance capsule removal schedule for Watts Bar Nuclear Plant (WBN) Unit 2. As noted in Table 4.0-1 of the WBN Unit 2 Pressure Temperature Limits Report (PTLR) (Appendix B to TVA System Description Document SDD-N3-68-4001, Reactor Coolant System),

reactor vessel surveillance capsule U was scheduled to be removed during the first WBN Unit 2 refueling outage (U2R1) scheduled for October 2017. However, due to the limited operation of WBN Unit 2, TVA requests NRC approval to revise the withdrawal schedule for capsule U from the U2R1 outage to the second WBN Unit 2 refueling outage (U2R2) scheduled for Spring 2019.

NRC Administrative Letter (AL) 97-04 (Reference 1) clarified the submittal requirements of 10 CFR 50, Appendix H, as follows:

"...as long as the plant's withdrawal schedule change meets the applicable American Society for Testing and Materials (ASTM) standard, the plant will not be exceeding the operating authority already granted in its license. Therefore, a license amendment would not be required, although prior NRC approval to verify conformance with the ASTM standard is required by 10 CFR 50, Appendix H."

ASTM E-185-82 (Reference 2) is the applicable standard for WBN Unit 2 in accordance with Section 5.2.4.3 of the WBN dual-unit Updated Final Safety Analysis Report (UFSAR). Because the proposed change described in this enclosure satisfies the requirements of ASTM E-185-82, TVA has determined that a license amendment is not required, which is consistent with the guidance of AL 97-04. Therefore, TVA requests NRC approval of the proposed withdrawal schedule.

2.0 CURRENT PROGRAM / WITHDRAWAL SCHEDULE The current withdrawal schedule for reactor vessel surveillance capsule U is shown in the below excerpt from Table 4.0-1 of the WBN Unit 2 PTLR. This withdrawal schedule was based on the capsule fluence exceeding 0.50E19 n/cm2 in accordance with Table 1 of ASTM E-185-82.

Table 4.0-1 Watts Bar Unit 2 Surveillance Capsule Removal Schedule Orientation of Lead Removal Expected Capsule Fluence Capsule Capsule Factor Time (n/cm2, E > 1.0 MeV) 1st Refuel U Dual 34° 5.13 0.50E19 Outage CNL-17-112 E1-2 of 6

Enclosure 1 3.0 CHANGES TO PROGRAM / WITHDRAWAL SCHEDULE In accordance with WBN Unit 2 Technical Specification (TS) 5.9.6, Reactor Coolant System (RCS) PRESSURE AND TEMPERATURE LIMITS REPORT (PTLR), Enclosure 2 provides a proposed revision to the WBN Unit 2 PTLR showing the revised reactor vessel surveillance capsule removal schedule and expected fluence for capsule U. Specifically, TVA proposes to revise the WBN Unit 2 reactor vessel surveillance capsule removal schedule as follows:

  • The removal schedule for capsule U is changed from U2R1 until the end of cycle 2 and will be removed during the U2R2 outage (Spring 2019).
  • The lead factor for capsule U is revised from 5.13 to 4.8. The lead factor is the proportional constant by which the capsule fluence leads the vessels maximum inner wall fluence. This coefficient is revised to reflect the plant-specific model.
  • The expected fluence for capsule U is revised from 0.50E19 n/cm2 to 0.77E19 n/cm2.

The proposed withdrawal schedule satisfies the requirements of ASTM E-185-82. Therefore, the withdrawal schedule satisfies the requirements of 10 CFR 50, Appendix H.

TVA will submit the actual revised WBN Unit 2 PTLR to NRC following NRC approval of the proposed revision to the WBN Unit 2 reactor vessel surveillance capsule withdrawal schedule.

4.0 JUSTIFICATION In accordance with Section 5.2.4.3 of the WBN dual-unit UFSAR, the WBN Unit 2 Reactor Vessel Irradiation Surveillance Program complies with ASTM E-185-82 and 10 CFR 50, Appendix H, with the exception that all of the reactor vessel irradiation surveillance capsules will receive a fluence that is at least four times the maximum reactor vessel fluence.

ASTM E-185-82 recommends a capsule to vessel maximum fluence between 1.0 and 3.0. At the time of the design of the surveillance program, all capsules were positioned as near to the vessel wall as possible and were limited to a fluence of less than 3.0 times the vessel fluence.

A more accurate method of calculating vessel and capsule fluence was subsequently developed that results in a lead factor of greater than 3.0 for the capsules. This difference is not considered to be of significant consequence because the test results from the encapsulated specimens will represent the actual behavior of the material in the vessel. Therefore, the evaluation of the effects of radiation on the actual vessel material is not influenced by the larger lead factor.

The current removal schedule for capsule U is based on WCAP-9455, Revision 3 (Reference 3) and ASTM E-185-82. Table 1 to ASTM E-185-82 lists the recommended number of surveillance capsules and their withdrawal schedule. ASTM E-185-82, Section 7.6.2, Withdrawal Schedule, states:

The first capsule is scheduled for withdrawal early in the vessel life to verify the initial predictions of the surveillance material response to the actual radiation environment.

Table 1 to ASTM E185-82 provides the recommended capsule withdrawal schedule based on the anticipated shift in the reference nil-ductility transition temperature (RTNDT) at the end of life (EOL). For WBN Unit 2, the RTNDT at EOL [i.e., 32 effective full power years (EFPY)] for all vessel forgings and welds will be less than 100°F. Therefore, only three surveillance capsules are required to be withdrawn.

CNL-17-112 E1-3 of 6

Enclosure 1 In accordance with Table 1 to ASTM E185-82, the first capsule should be removed when the first of the following criteria is satisfied as shown in Table 1. Based on the information in Table 1, the limiting criterion for WBN Unit 2 is when the fluence will exceed 5.0E18 n/cm2.

Table 2 shows the fluence projection for the WBN Unit 2 surveillance capsules.

Table 1 WBN Unit 2 Conformance to ASTM E185-82 Criterion ASTM E185-82 Criterion WBN Unit 2 Conformance Assuming 1.5 EFPY per cycle (i.e., 18-month cycles),

At 6 EFPY six EFPY will not be reached until cycle 4.

The fluence projection in Table 2 shows that after one cycle the maximum surveillance capsule fluence will be 4.370E18 n/cm2 (E > 1.0 MeV). After two cycles, the Fluence > 5.0E18 n/cm2 maximum fluence will be 7.826E18 n/cm2 (E > 1.0 MeV)

(Reference 4). Therefore, the WBN Unit 2 surveillance capsules will exceed 5.0E18 n/cm2 during cycle 2.

The highest predicted RTNDT, corresponding to the intermediate to lower shell forging circumferential weld, will RTNDT > 50°F not exceed 50°F before EOL equivalent fluence is reached per Regulatory Guide 1.99 Position 2.1.

Table 2 Fast Neutron Fluence Projections at the Geometric Center of the WBN Unit 2 Surveillance Capsules at Core Midplane(a)

Cumulative Neutron Fluence (E > 1.0 MeV) (n/cm2)

Operating Cycle 31.5 Degrees 34.0 Degrees Time (b) (c) 34.0 Degrees Single(d)

(EFPY) Dual Dual 1 1.27 3.636E18 4.307E18 4.370E18 2 2.61 6.590E18 7.714E18 7.826E18 Notes:

(a) Projected values taken from Table 2-3 of Reference 4, which provided the methodology and results of the generation of heatup and cooldown pressure temperature (P-T) limit curves for normal operation of the WBN Unit 2 reactor vessel. The analyses in Reference 4 considered the implementation of Tritium-Producing Burnable Absorber Rods (TPBARs) at the beginning of Cycle 4; no TPBARs were included in the model for Cycles 1, 2, and 3.

(b) Per Table 4-1 of Reference 3, this location corresponds to capsules V and Y.

(c) Per Table 4-1 of Reference 3, this location corresponds to capsules U and X.

(d) Per Table 4-1 of Reference 3, this location corresponds to capsules W and Z.

CNL-17-112 E1-4 of 6

Enclosure 1 The revised fluence projections in Table 2 show a reduction in surveillance capsule fluence values (i.e., from 5.0E18 n/cm2 to 4.307E18 n/cm2 for cycle 1) because the updated projections are based on core power distributions used in a plant-specific transport analysis for each of the first seven projected fuel cycles at WBN Unit 2. The projections also include cycle-dependent fuel assembly initial enrichments, burnups, and axial power distributions (Reference 4). The current withdrawal schedule is based on a conservative loading pattern that has been historically used for four-loop reactors, which resulted in the capsule exceeding 5.0E18 n/cm2 after the first cycle. Because each of the capsules contents are identical and the capsule fluence values are similar, Capsule U [with an end of cycle (EOC) 2 fluence of 7.714E18 n/cm2]

will be the first capsule to be pulled and tested for consistency with Reference 3.

Additionally, WBN Unit 2 has operated at lower than anticipated capacity during cycle 1.

Cycle 1 is currently anticipated to reach 0.69 EFPY at the end of cycle 1 compared to the analyzed burnup of 1.27 EFPY (Table 2-3 of Reference 3). Taking these lower operating conditions into account, an estimate of the fluence for Capsule U is 2.34E18 n/cm2

[i.e., (4.307E18 n/cm2)(0.69 EFPY)/(1.27 EFPY)] at the end of the first cycle. This further decreased the anticipated fluence and emphasizes the need to leave the capsule in the reactor longer in order to provide relevant surveillance data (i.e., data producing a shift in RTNDT).

Therefore, TVA proposes to revise the withdrawal schedule for capsule U to U2R2.

5.0 PRECEDENT The NRC has previously approved the following reactor vessel surveillance program capsule withdrawal schedule revisions:

  • WBN Unit 1 [Safety Evaluation dated March 27, 2014 (Reference 5)]
  • Shearon Harris Nuclear Plant [Safety Evaluation dated October 21, 2011 (Reference 6)]
  • H. B. Robinson Steam Electric Plant, Unit 2 [Safety Evaluation dated December 21, 2011 (Reference 7)]
  • Diablo Canyon Power Plant, Unit 1 [Safety Evaluation dated March 2, 2012 (Reference 8)]
  • Fort Calhoun Station, Unit 1 [Safety Evaluation dated January 31, 2013 (Reference 9)]
  • Seabrook Station, Unit 1 [Safety Evaluation dated June 13, 2013 (Reference 10)]
  • Turkey Point Nuclear Generating Unit Numbers 3 and 4 [Safety Evaluation dated September 4, 2013 (Reference 11)]

CNL-17-112 E1-5 of 6

Enclosure 1

6.0 REFERENCES

1. NRC Administrative Letter 97-04, "NRC Staff Approval for Changes to 10 CFR Part 50, Appendix H, Reactor Vessel Surveillance Specimen Withdrawal Schedules," dated September 30, 1997
2. ASTM E-185-82, "Standard Practice for Conducting Surveillance Tests for Light-Water Cooled Nuclear Power Reactor Vessels," dated July 1, 1982
3. WCAP-9455, Revision 3, Tennessee Valley Authority Watts Bar Unit No. 2 Reactor Vessel Radiation Surveillance Program, September 2009
4. Westinghouse WCAP-18191-NP, Revision 0, "Watts Bar Unit 2 Heatup and Cooldown Limit Curves for Normal Operation and Supplemental Reactor Vessel Integrity Evaluations," dated May 2017
5. NRC letter to TVA, Watts Bar Nuclear Plant, Unit 1 -Review of Reactor Vessel Materials Surveillance Program- Revised Surveillance Capsule Withdrawal Schedule (TAC No. MF3162), dated March 27, 2014 (ML14083A247)
6. NRC letter to Carolina Power and Light Company, Shearon Harris Nuclear Plant - Safety Evaluation for Revision to Reactor Vessel Surveillance Capsule Withdrawal Schedule (TAC No. ME6998)," dated October 21, 2011 (ML11293A076)
7. NRC letter to Carolina Power and Light Company, "H. B. Robinson Steam Electric Plant, Unit No. 2 - Request for Revision to Reactor Vessel Material Surveillance Capsule Withdrawal Schedule (TAC No. ME7533)," dated December 21, 2011 (ML11349A026)
8. NRC Letter to Pacific Gas and Electric Company, "Diablo Canyon Power Plant, Unit No. 1:

Safety Evaluation for Request to Revise the Reactor Vessel Material Surveillance Program Withdrawal Schedule (TAC ME7615)," dated March 2, 2012 (ML120330497)

9. NRC Letter to Omaha Public Power District, "Fort Calhoun Station, Unit 1 - Request for Approval of Proposed Changes to the Reactor Pressure Vessel Surveillance Capsule Withdrawal Schedules (TAC No. ME8219)," dated January 31, 2013 (ML13017A467)
10. NRC Letter to NextEra Energy Seabrook, LLC, "Seabrook Station, Unit 1 - Revision to Reactor Vessel Surveillance Capsule Withdrawal Schedule (TAC No. MF0669)," dated June 13, 2013 (ML13050A138)
11. NRC Letter to NextEra Energy, "Turkey Point Nuclear Generating Units Nos. 3 and 4 -

Review of Reactor Vessel Material Surveillance Program - Revised Surveillance Capsule Withdrawal Schedule (TAC Nos. ME9564 and ME9565)," dated September 4, 2013 (ML13191A090)

CNL-17-112 E1-6 of 6

Enclosure 2 Proposed Revised WBN Unit 2 Pressure Temperature Limits Report CNL-17-112 E2-1

Enclosure 3 New Regulatory Commitment Commitment Due Date/Event TVA will submit the revised WBN Unit 2 PTLR to NRC following Following NRC approval of NRC approval of the proposed revision to the WBN Unit 2 the proposed revision to the reactor vessel surveillance capsule withdrawal schedule. WBN Unit 2 reactor vessel surveillance capsule withdrawal schedule.

CNL-17-112 E3-1

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