CNL-18-058, Supplement to Application to Revise Watts Bar Nuclear Plant Unit 2 - License Condition 2.C(4) PAD4TCD (391-WBN-TS-18-03)

Supplement to Application to Revise Watts Bar Nuclear Plant Unit 2 - License Condition 2.C(4) PAD4TCD (391-WBN-TS-18-03)

ML18137A193
Person / Time
Site:	Watts Bar
Issue date:	04/27/2018
From:	James Shea Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
391-WBN-TS-18-03, CNL-18-058, EPID L-2018-LLA-0051
Download: ML18137A193 (6)

Text

1101 Market Street, Chattanooga, Tennessee 37402 CNL-18-058 April 27, 2018 10 CFR 50.90 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:

Supplement to Application to Revise Watts Bar Nuclear Plant Unit 2 -

License Condition 2.C(4) PAD4TCD (391-WBN-TS-18-03)

(EPID L-2018-LLA-0051)

References:

1. TVA Letter to NRC, CNL-18-016, Watts Bar Nuclear Plant Unit 2 -

Application to Revise License Condition 2.C(4) PAD4TCD (391-WBN-TS-18-03), dated March 5, 2018 (ML18064A192)

2. NRC letter to TVA, Watts Bar Nuclear Plant, Unit 2-Supplemental Information Needed for Acceptance of Requested Licensing Action Re: Amendment to Facility Operating License Condition Related to Use of the PAD4TCD Code (EPID L-2018-LLA-0051), dated April 12, 2018 (ML18095A191)

In Reference 1, Tennessee Valley Authority (TVA) submitted a request for an amendment to Facility Operating License No. NPF-96 for the Watts Bar Nuclear Plant (WBN), Unit 2.

The proposed change revises WBN Unit 2 OL condition 2.C(4) to permit the use of the PAD4TCD computer program to continue to establish core operating limits until the WBN Unit 2 steam generators (SGs) are replaced with SGs equivalent to those in WBN Unit 1.

During the acceptance review of Reference 1, the Nuclear Regulatory Commission (NRC) determined that supplemental information was needed (Reference 2) and requested that TVA respond by April 27, 2018.

U.S. Nuclear Regulatory Commission CNL-18-058 Page 2 April 27, 2018 to this letter responds to Reference 2. Enclosure 2 to this letter provides new Sections 4.3.1 and revised Section 7.0 to Reference 1. The new Section 4.3.1 includes the information provided in Enclosure 1. Revised Section 7.0 of Enclosure 2 provides an updated list of references that supersedes the one provided in Reference 1.

The supplement in Enclosure 2 does not change the no significant hazards consideration or the environmental considerations contained in the referenced letter. Additionally, in accordance with 10 CFR 50.91 (b)(1 ), TVA is sending a copy of this letter and the enclosures to the Tennessee Department of Environment and Conservation.

There are no new regulatory commitments made in this letter. Please address any questions regarding this request to Edward D. Schrull at (423) 751-3850.

I declare under penalty of perjury that the foregoing is true and correct. Executed on this 27th day o April 2018 .

. Shea President, Nuclear Regulatory Affairs and Support Services

Enclosures:

1. Response to the NRC Request for Supplemental Information

2. Supplement to Application to Revise Watts Bar Nuclear Plant Unit 2 -

License Condition 2.C(4) PAD4TCD (391-WBN-TS-18-03)

(EPID L-2018-LLA-0051) cc (Enclosures):

NRC Regional Administrator - Region II NRC Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant Director, Division of Radiological Health - Tennessee State Department of Environment and Conservation

Enclosure 1 Tennessee Valley Authority Response to the NRC Request for Supplemental Information NRC Request for Supplemental Information By letter dated March 5, 2018 (Agencywide Documents Access and Management System Accession No. ML18064A192), Tennessee Valley Authority (TVA, the licensee) submitted a license amendment request for the Watts Bar Nuclear Plant, Unit 2. The proposed amendment would revise the Watts Bar Unit 2, Facility Operating License, NPF-96, to permit continued use of the Fuel Rod Performance and Design 4 Thermal Conductivity Degradation (PAD4TCD) computer code to establish core operating limits for Watts Bar Unit 2 until the replacement of the Unit 2 steam generators.

The Watts Bar dual-unit UFSAR, Section 3.1.1, states, in part:

The Watts Bar Nuclear Plant was designed to meet the intent of the "Proposed General Design Criteria for Nuclear Power Plant Construction Permits" published in July 1967. The Watts Bar construction permit was issued in January 1973. This UFSAR, however, addresses the NRC General Design Criteria (GDC) published as Appendix A to [Title 10 Code of Federal Regulations] 10 CFR [Part 50) in July 1971, including Criterion 4 as amended October 27, 1987.

The Watts Bar UFSAR provides a discussion of the design features and procedures which meet the intent of the design criteria, including a discussion of any exceptions to the GDC.

The GDC that are relevant to this amendment request include GDC 10, 15, 20, 25, 26 and

28. These criteria specifically require the reactor fuel, coolant, and protection systems to be designed and operated with sufficient margins of safety to limit the postulated consequences of anticipated operational occurrences and infrequent events.

The technical justification provided in the license amendment request indicates that, using input generated with PAD4TCD, the results of the Watts Bar Unit 2 emergency core cooling system (ECCS) evaluation remain within the acceptance criteria codified at 10 CFR 50.46(b). The licensee did not provide analyses or evaluations demonstrating how the remaining Updated Final Safety Analysis Report (UFSAR) Chapter 15 design basis accident and anticipated operational occurrence safety analyses account for the effects of nuclear fuel thermal conductivity degradation (TCD). Therefore, significant analyses or evaluations are missing from the amendment request, which are needed for the staff to determine whether facility operation on an indefinite basis would remain within the licensing basis acceptance criteria when accounting for the effects of TCD.

The license amendment request cites, as precedent, a similar license condition applied to the facility operating licenses for Turkey Point, Units 3 and 4 (PTN [sic TPN] 3 and 4, respectively).

This PTN 3 and 4 license condition is similarly not restricted to a number of calendar years or operating cycles; however, the condition (and associated license amendment request) were approved based on analyses that dispositioned the effects of thermal conductivity degradation for both postulated LOCAs and other design basis accidents and anticipated operational occurrences.

Refer to FPL letter L-2011-561 dated December 31, 2011 (Agencywide Document Access and Management System Accession No. ML12009A113), for further detail.

CNL-18-058 Page E1-1 of 2

Enclosure 1 NRC Sufficiency Item:

Provide (a) information to demonstrate how existing, non-LOCA accident and transient analyses described in UFSAR Chapter 15 account for the effects of degradation of nuclear fuel thermal conductivity as a function of burnup, or (b) evaluations or analyses to show that Watts Bar Unit 2 facility operation remains in compliance with licensing basis acceptance criteria applicable to UFSAR Chapter 15 safety analyses (identified above), accounting for the effects of TCD.

TVA Response As discussed with the Nuclear Regulatory Commission (NRC) at a pre-submittal meeting on January 25, 2018, regarding the to-be-submitted license amendment request (now Reference 1),

and during a conference call with the NRC on April 3, 2018, regarding the above request for supplemental information, TVA plans to update the non-LOCA Watts Bar Nuclear Plant (WBN) dual-unit UFSAR Chapter 15 analyses as part of an overall program for accounting for TCD in Westinghouse-performed safety analyses (References 2, 3, and 4). During the conference call on April 3, 2018, NRC acknowledged its awareness of this Westinghouse program and noted that updating the non-LOCA WBN dual-unit Chapter 15 analyses and transients to account for TCD is not necessary to address the sufficiency item. Rather, the NRC recommended that TVA qualitatively address the effects of TCD on the non-LOCA WBN dual-unit UFSAR Chapter 15 accidents in order to demonstrate that WBN Unit 2 facility operation remains in compliance with licensing basis acceptance criteria applicable to the WBN dual-unit UFSAR Chapter 15 safety analyses when accounting for the effects of TCD.

Accordingly, Enclosure 2 provides a new Section 4.3.1 to the Reference 1 application that addresses both items (a) and (b) of the NRC request for supplemental information. Section 7.0 of provides an updated list of references that supersedes the one provided in the Reference 1 application.

References

1. TVA letter to NRC, CNL-18-016, Watts Bar Nuclear Plant Unit 2 - Application to Revise License Condition 2.C(4) PAD4TCD (391-WBN-TS-18-03), dated March 5, 2018 (ML18064A192)

2. Westinghouse letter to NRC, LTR-NRC-13-72, Submittal of WCAP-17642-P, Revision 0 and WCAP-17642-NP, Revision 0, Westinghouse Performance Analysis and Design Model (PAD5), (Proprietary/Non-Proprietary), dated October 29, 2013 (ML13308A425)

3. NRC memorandum, Summary of Closed Meeting to Discuss Implementation Plan for the Westinghouse Electric Company Topical Report WCAP-17642-P-A/WCAP-17642-NP-A, Revision 1, Westinghouse Performance Analysis and Design Model (PAD5)

(EPID No.: L2018-LRO-0002), dated March 19, 2018 (ML18057A038)

4. Westinghouse letter to NRC, LTR-NRC-18-7, Submittal of Presentation PAD5 Implementation Considerations for a Closed Meeting with the NRC on January 29, 2018 (Proprietary), dated January 23, 2018 (ML18023B555)

CNL-18-058 Page E1-2 of 2

Enclosure 2 Supplement to Application to Revise Watts Bar Nuclear Plant Unit 2 - License Condition 2.C(4)

PAD4TCD (391-WBN-TS-18-03) (EPID L-2018-LLA-0051) 4.3.1 Effects of Thermal Conductivity Degradation on non-LOCA Analyses In Reference 10, Westinghouse evaluated the effect of thermal conductivity degradation (TCD) on non-loss of coolant accident (Non-LOCA) safety analyses for Westinghouse nuclear steam supply system (W-NSSS) plant designs. Reference 10 concluded that the existing Westinghouse safety analysis methodologies ensure that the non-LOCA transients are within the applicable safety analysis acceptance criteria, even when the effects of TCD are explicitly included. Further information with respect to WBN Unit 2 is provided below.

TCD is a phenomenon that causes the thermal conductivity of uranium dioxide (UO2) to decrease with burnup. The decrease in fuel pellet thermal conductivity increases fuel temperatures, which are used in non-LOCA UFSAR Chapter 15 safety analyses.

Westinghouse has previously provided the NRC with a safety assessment of TCD in Reference 10 discussing all impacted areas. Table 1 of Reference 10 lists the methods that are applicable to each plant. WBN Unit 2 is not listed in Reference 10 because it was not operating at the time Reference 10 was issued. However, WBN Unit 2 uses the same Westinghouse methods as evaluated in Reference 10 for all the non-LOCA UFSAR Chapter 15 analyses.

Appendix B of Reference 10 includes an evaluation of the effect of TCD on each non-LOCA UFSAR Chapter 15 analysis. In Appendix B of Reference 10, the following three categories of events were established relative to the potential impacts of TCD:

• Events that had either no impact or negligible impacts.

• Events that were affected, but for which acceptable results could ultimately be obtained by relying on conservatisms and margins in existing analyses.

• Events that were significantly affected and would require additional constraints to be imposed on reloads.

In Reference 10, the non-LOCA UFSAR Chapter 15 events were categorized as either unaffected or had sufficient conservatisms and margins to offset the impact of TCD. As discussed above, WBN Unit 2 uses the same Westinghouse analysis methods, so the discussions and conclusions in Reference 10 are applicable to WBN Unit 2. Therefore, Reference 10 provides the justification that WBN Unit 2 remains in compliance with the licensing basis acceptance criteria applicable to UFSAR Chapter 15 safety analyses when accounting for the effects of thermal conductivity degradation using the initial conditions derived from the safety analyses on which the TS are based.

CNL-18-058 Page E2-1 of 2

Enclosure 2

7.0 REFERENCES

1. TVA letter to NRC, CNL-15-239, Watts Bar Nuclear Plant Unit 2 - Application to Revise License Condition 2.C(4) PAD4TCD, dated December 31, 2015 (ML15365A595)

2. NRC letter to TVA, Watts Bar Nuclear Plant Unit 2 - Issuance of Amendment Regarding use of PAD4TCD for the Second Operating Cycle (CAC No. MF7219), dated July 25, 2016 (ML16174A354)

3. TVA letter to NRC, Watts Bar Nuclear Plant, Unit 2, Final Safety Analysis Report (FSAR),

Amendment 97, dated January 11, 2010 (ML100191421)

4. Westinghouse Report WCAP-16009-P-A, Realistic Large-Break LOCA Evaluation Methodology Using the Automated Statistical Treatment Of Uncertainty Method (ASTRUM), January 2005 (Westinghouse Proprietary Class 2) (ML050910157)

5. Westinghouse Report WCAP-15063-P-A, Revision 1 with Errata, Westinghouse Improved Performance Analysis and Design Model (PAD 4.0), July 2000 (Westinghouse Proprietary Class 2) (ML003735304)

6. NRC Information Notice 2009-23, Nuclear Fuel Thermal Conductivity Degradation, dated October 8, 2009 (ML091550527)

7. NRC Information Notice 2011-21, Realistic Emergency Core Cooling System Evaluation Model Effects Resulting from Nuclear Fuel Thermal Conductivity Degradation, dated December 13, 2011 (ML113430785)

8. NRC Information Notice 2009-23, Supplement 1, Nuclear Fuel Thermal Conductivity Degradation, dated October 26, 2012 (ML121730336)

9. NRC letter to Florida Power and Light Company, Turkey Point Units 3 and 4 - Issuance of Amendments Regarding Extended Power Uprate (TAC Nos. ME4907 and ME4908), dated June 15, 2012 (ML11293A365)

10. Westinghouse letter to NRC, LTR-NRC-12-18 Westinghouse Response to December 16, 2011 NRC Letter Regarding Nuclear Fuel Thermal Conductivity Degradation (TAC No. ME5186) (Proprietary), dated February 17, 2012 (ML12053A105)

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