ML22083A237

NRR E-mail Capture - Request for Additional Information and Confirmation of Information Related to Tva'S Request for Changes to Watts Bar Nuclear Plant, Units 1 and 2, Technical Specification 3.7.8

ML22083A237
Person / Time
Site:	Watts Bar
Issue date:	03/24/2022
From:	Kimberly Green Plant Licensing Branch II
To:	Wells R Tennessee Valley Authority
References
L-2021-LLA-0174
Download: ML22083A237 (5)

Text

From: Green, Kimberly Sent: Thursday, March 24, 2022 11:22 AM To: Wells, Russell Douglas

Subject:

Request for Additional Information and Confirmation of Information Related to TVA's Request for Changes to Watts Bar Nuclear Plant, Units 1 and 2, Technical Specification 3.7.8 (EPID L-2021-LLA-0174)

Attachments: Final RAI 03-24-22.pdf

Dear Mr. Wells,

By letter dated September 29, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21273A046), the Tennessee Valley Authority (TVA) requested changes to the Watts Bar Nuclear Plant (Watts Bar), Units 1 and 2, Technical Specifications (TS). The proposed changes would revise TS 3.7.8, Essential Raw Cooling Water (ERCW)

System, by adding a new Condition A to Watts Bar, Unit 1, TS 3.7.8, to permanently extend the allowed Completion Time to restore one ERCW system train to operable status from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days. The proposed changes also include revising the bounding temperature for the ultimate heat sink in Condition A to less than or equal to 78 degrees Fahrenheit, and adding and/or revising the Note, numbering, and wording of the Conditions to specify when the Conditions apply.

The U.S. Nuclear Regulatory Commission (NRC) staff is reviewing your submittal and has identified areas where additional information or clarification is needed to complete its review.

A draft request for additional information (RAI) and confirmation of information (RCI) was previously transmitted to you by email dated March 10, 2022. At your request, a clarification call was held on March 24, 2022, to clarify the NRC staffs draft RAI and RCI. As a result of the clarification call, no changes were made to the requests.

As agreed during the call, a response to the attached RAI and RCI is requested by May 2, 2022.

The NRC staff considers that timely responses to RAIs help ensure sufficient time is available for staff review and contribute toward the NRCs goal of efficient and effective use of staff resources. If circumstances result in the need to revise the requested response date, please contact me at (301) 415-1627 or via email at Kimberly.Green@nrc.gov.

Sincerely, Kimberly J. Green, Senior Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Hearing Identifier: NRR_DRMA Email Number: 1570 Mail Envelope Properties (DM6PR09MB54627A0533E30EE15A34949E8F199)

Subject:

Request for Additional Information and Confirmation of Information Related to TVA's Request for Changes to Watts Bar Nuclear Plant, Units 1 and 2, Technical Specification 3.7.8 (EPID L-2021-LLA-0174)

Sent Date: 3/24/2022 11:22:28 AM Received Date: 3/24/2022 11:22:00 AM From: Green, Kimberly Created By: Kimberly.Green@nrc.gov Recipients:

"Wells, Russell Douglas" <rdwells0@tva.gov>

Tracking Status: None Post Office: DM6PR09MB5462.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 2027 3/24/2022 11:22:00 AM Final RAI 03-24-22.pdf 91913 Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

REQUEST FOR ADDITIONAL INFORMATION AND REQUEST FOR CONFIRMATION OF INFOMRATION WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-390 AND 50-391 EXTEND COMPLETION TIME TO RESTORE ONE ESSENTIAL RAW COOLING WATER SYSTEM TRAIN TO OPERABLE By letter dated September 29, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21273A046), the Tennessee Valley Authority (TVA) submitted a license amendment request (LAR) to the U.S. Nuclear Regulatory Commission (NRC) for the Watts Bar Nuclear Plant (Watts Bar), Units 1 and 2. The proposed amendments would revise Watts Bar, Unit 1 and 2, Technical Specification (TS) 3.7.8, Essential Raw Cooling Water (ERCW) System, by adding a new Condition A to Watts Bar, Unit 1, TS 3.7.8, to permanently extend the allowed Completion Time to restore one ERCW system train to operable status from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days, to support maintenance on the Watts Bar, Unit 2, 6.9 kilovolt shutdown boards. The proposed amendments would also revise the bounding temperature for the ultimate heat sink (UHS) in Condition A to less than or equal to 78 degrees Fahrenheit.

Additionally, the proposed amendments would add and/or revise the Note, numbering, and wording of the Conditions to specify when the Conditions apply.

Regulatory Bases:

General Design Criterion (GDC) 44, Cooling Water, requires, in part, that the system safety function shall be to transfer heat loads to the ultimate heat sink under normal and accident conditions, and that suitable redundancy in components shall be provided to assure that the system safety function can be accomplished, assuming a single failure.

Section 4.1 of the Enclosure to the LAR indicates that the ERCW system is designed to comply with GDC 44. Sections 3.2.4, 3.2.5, and 3.2.6 of the Enclosure to the LAR provide TVAs thermal and hydraulic analyses to demonstrate that the operation of the ERCW system under the proposed LAR conditions (e.g., revised UHS temperature limit, reduced number of operable ERCW pumps and EDGs, and one unit defueled) will be able to maintain its GDC 44 capabilities to perform its safety function of adequate component cooling capability for a design basis accident under the most limiting single failure.

SCPB RAI-1 In TVAs thermal analyses, Table 8 and Table 9 of the Enclosure to the LAR listed the following design parameters to compare against calculated values to show the margin of the heat removal capability (left column).

Parameter Design Minimum Design Maximum (Current LAR) (Previous LAR)

Btu/hr Btu/hr A/B Train - Component Cooling System 88,764,506 106,183,506 (CCS) Heat Exchanger (HX) Duty Residual Heat Removal HX Duty 54,800,000 54,800,000 Spent Fuel Pool HX Duty 32,420,000 32,420,000 Core Spray System (CSS) HX Duty 87,323,731 81,294,921 The design of the ERCW in the proposed LAR has not been changed since the previous LAR for a similar analysis (ADAMS Accession No. ML19038A483). However, the NRC staff noted that the design values for the CCS HX Duty and CSS HX Duty in the proposed LAR are inconsistent with those data used in the previous LAR (right column, see Table 5 of ). For example, the design value (minimum) for the CSS HX duty for the current LAR is higher than the design value (maximum) for the CSS HX duty for the previous LAR.

Also, the design values (minimum and maximum) for the RHR HX duty and spent fuel pool HX duty are the same.

Provide the following:

a. Explain the above apparent inconsistences

b. Clarify which values (minimum or maximum) should be used for the determination of the margin of the heat removal capability and revise accordingly, if needed, and

c. Identify the source of the design data used for the current LAR.

SCPB RAI-2 Section 3.2.4 of the Enclosure to the LAR describes the thermal hydraulic evaluation method developed by TVA to support its request to extend the completion time for restoring one train of ERCW to operable status and to increase the UHS temperature. The methodology of the current analysis is similar to the one developed for the previous LAR (ADAMS Accession No. ML19038A483). Section 3.2.7 of both LARs (current and previous) list the analysis assumptions and conservatisms used in the respective analysis. In addition to the differences as identified in SCPB RAI-1 above, the NRC staff noted some differences in the assumptions and conservatisms. For example, in the current LAR, the flow values determined in the ERCW hydraulic analysis are reduced by 5 percent, whereas in the previous analysis, the flow values were reduced by 10 percent. Also, for the CSS HX model (LAR Section 3.2.6.1), the benchmarked PROTO-HX model for the LOCA analysis assumed 10 percent of the tubes were plugged, whereas in the previous LAR model, 5 percent of the tubes were assumed to be plugged (LAR Section 3.2.5.1).

a. Confirm or clarify whether the methodology developed for the proposed LAR is the same as, or different from, the methodology developed for the previous LAR.

b. Identify all the differences (including, but not limited to the above examples) in the assumptions, methodology, and acceptance criteria.

c. Provide the reasons for any differences.

STSB RCI-1 Regulatory Basis:

Pursuant to 10 CFR 50.36, TSs for operating reactors are required, in part, to include items in the following five specific categories: (1) safety limits, limiting safety system settings, and limiting control settings; (2) limiting conditions for operation; (3) surveillance requirements; (4) design features; and (5) administrative controls.

Issue:

The proposed Condition C states: Required Action and associated Completion Time of Condition A not met.

Proposed Required Action A.2 states Verify UHS temperature is 78° F with a Completion Time of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

Required Action A.1 and A.2 are joined by the logical connector AND. As the proposed TS is currently constructed, if while in Condition A the temperature were to exceed 78° F, Required Action A.2 would not be met, and Condition C would be entered. Therefore, the purpose of the second part of the Completion Time for Required Action A.1 it is not clear to the NRC staff .

Request:

Confirm that this is the intent of the proposed TS.