ML20322A441

NRR E-mail Capture - Request for Additional Information Regarding Tva'S Request to Revise TS 3.7.11 Related to the MCR Chiller Replacement

ML20322A441
Person / Time
Site:	Watts Bar
Issue date:	11/17/2020
From:	Kimberly Green NRC/NRR/DORL/LPL2-2
To:	Wells R Tennessee Valley Authority
References
L-2020-LLA-0114
Download: ML20322A441 (6)

Text

From: Green, Kimberly Sent: Tuesday, November 17, 2020 12:34 PM To: Wells, Russell Douglas Cc: Shoop, Undine

Subject:

Request for Additional Information Regarding TVA's Request to Revise TS 3.7.11 Related to the MCR Chiller Replacement (EPID L-2020-LLA-0114)

Attachments: Final RAI 11-17-20.pdf

Dear Mr. Wells,

By letter dated May 19, 2020 (Agencywide Documents Access and Management System Accession No. ML20140A342), Tennessee Valley Authority (TVA) submitted a license amendment request for Watts Bar Nuclear Plant, Units 1 and 2. The proposed amendments revise Technical Specification 3.7.11, Control Room Emergency Air Temperature Control System (CREATCS), to add a one-time change of a footnote to the Completion Time for Required Action A.1 to allow one CREATCS train to be inoperable for up to 60 days while performing modifications to the CREATCS chillers. The proposed amendments also add a one-time change of a footnote to the Completion Time for Required Action E.1 to allow delayed entry into TS Limiting Condition for Operation (LCO) 3.0.3 for up to four days in the event that both CREATCS trains are inoperable during the modifications to the CREATCS chillers.

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

A draft request for additional information (RAI) was previously transmitted to you by email dated November 5, 2020. At your request, a clarification call was held on November 17th to clarify the NRC staffs requests. Based on the discussion during that call, the NRC has revised SCPB-RAI-1 slightly (changes shown in red) to request that TVA Provide a discussion and justification of the measures, mitigation, or procedures that TVA will implement to assure a safe shutdown of both WBN units after the loss of both trains of CREATCS when the MCR temperature starts at 90 °F. The other two requests remain the same.

As agreed during the call, a response to the attached RAI is requested within 30 days from the date of this email.

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, Kim Green (301) 415-1627 kimberly.green@nrc.gov

Hearing Identifier: NRR_DRMA Email Number: 895 Mail Envelope Properties (MN2PR09MB5388B926CEB77CA5336B1BCF8FE20)

Subject:

Request for Additional Information Regarding TVA's Request to Revise TS 3.7.11 Related to the MCR Chiller Replacement (EPID L-2020-LLA-0114)

Sent Date: 11/17/2020 12:34:00 PM Received Date: 11/17/2020 12:34:00 PM From: Green, Kimberly Created By: Kimberly.Green@nrc.gov Recipients:

"Shoop, Undine" <Undine.Shoop@nrc.gov>

Tracking Status: None "Wells, Russell Douglas" <rdwells0@tva.gov>

Tracking Status: None Post Office: MN2PR09MB5388.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 2288 11/17/2020 12:34:00 PM Final RAI 11-17-20.pdf 80255 Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

REQUEST FOR ADDITIONAL INFORMATION TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-390 AND 50-391 MAIN CONTROL ROOM CHILLER COMPLETION TIME EXTENSION By letter dated May 19, 2020, Tennessee Valley Authority (TVA) submitted a license amendment request (LAR) to revise the technical specifications for the Watts Bar Nuclear Plant (WBN), Units 1 and 2 (Agencywide Documents and Access Management System Accession No. ML20140A342). The requested changes would revise WBN, Units 1 and 2, Technical Specification (TS) 3.7.11 "Control Room Emergency Air Temperature Control System (CREATCS)," to add a one-time change of a footnote to the Completion Time for Required Action A.1 to allow one CREATCS train to be inoperable for up to 60 days while performing modifications to the CREATCS chillers. Additionally, a one-time change of a footnote to the Completion Time for Required Action E.1 to allow delayed entry into TS Limiting Condition for Operation (LCO) 3.0.3 for up to four days in the event that both CREATCS trains are inoperable during the modifications to the CREATCS chillers would be added. The one-time TS changes are limited to the time that the CREATCS modifications are being performed between the timeframe of May 1, 2021, and October 1, 2022.

The U.S. Nuclear Regulatory Commission (NRC) staff is reviewing the request and has identified areas for which additional information is needed prior to completing its review. The staffs requests for additional information (RAI) are below.

SCPB-RAI-1 Regulatory Basis Appendix A to Part 50 of Title 10 of the Code of Federal Regulations (10 CFR) contains the principal design criteria for a proposed facility that must be included in an application for a design certification, combined license, design approval, or manufacturing license, respectively.

These General Design Criteria (GDC) establish the minimum requirements for the principal design criteria for water-cooled nuclear power plants similar in design and location to plants for which construction permits have been issued by the Commission.

GDC 19, Control room, states, in part:

A control room shall be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe condition under accident conditions, including loss-of-coolant accidentsEquipment at appropriate locations outside the control room shall be provided (1) with a design capability for prompt hot shutdown of the reactor, including necessary instrumentation and controls to maintain the unit in a safe condition during hot shutdown, and (2) with a potential capability for subsequent cold shutdown of the reactor through the use of suitable procedures.

Issue TVA has proposed a one-time change to the footnote for the TS 3.7.11, Condition E, completion time to allow a four-day delayed entry into LCO 3.0.3. The proposed change states that main control room (MCR) temperature will be monitored every hour to verify that it is less than or equal to 90 degrees Fahrenheit (°F), and that if the temperature goes above 90 °F, or the duration without a train of CREATCS being operable exceeds four days, immediate entry into LCO 3.0.3 is required.

As stated in LAR Section 3.4.2:

The proposed footnote to WBN Units 1 and 2 TS 3.7.11, Condition E, is also based on verifying that the MCR temperature is less than or equal to 90°F. The temperature limit for MCR equipment operability is 104°F. The 90°F temperature limit provides adequate margin between the normal MCR operating temperature of 75°F and a limit that ensures that the equipment operability limit of 104°F is not exceeded. By maintaining the MCR temperature at or below 90°F, the operability requirements for safety-related functions provided by equipment and instrumentation in the MCR, as well as habitability needs for operating personnel, is satisfied.

The LAR further states:

To support the one-hour frequency for temperature monitoring TVA evaluated the effect of a loss of cooling on the MCR temperature by performing an analysis of the heatup of the MCR and surrounding areas. The analysis assumed normal operating heat loads, normal average initial room temperatures, summertime maximum outdoor temperatures, one [air handling unit] AHU operating, and no chillers in operation. The calculation demonstrates that the temperature increase from 75°F (normal MCR operating temperature) to 104°F takes approximately 5.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. This temperature response does not credit the temporary chiller system cooling.

During the regulatory audit, the staff audited the evaluation referenced above. Calculation MDQ00003120090157, Revision 7, Main Control Room Floor (EL. 755.0) Transient Temperature Analysis, contains Figure H.4, Cases H1 through H3 Main Control Room Temperatures, which shows the calculated MCR transient temperatures. Figure H.4 supports the passage above and indicates that with normal heat loads (i.e., non-LOCA), the time to heat up the MCR to 104 °F from approximately 75 °F for the worst case (i.e., Case H1) is 5.28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />.

This figure also indicates that the MCR would reach 106°F after 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> and 118°F after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, absent a cooling water supply.

The proposed one-time change to the footnote for the TS 3.7.11, Condition E, completion time would allow the MCR temperature to reach 90°F before LCO 3.0.3 is entered. LCO 3.0.3 requires that the reactor shall be placed in MODE 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />; MODE 4 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />; and MODE 5 within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />.

The staff notes that the MCR could reach the 104°F limit for MCR operability and the safety-related equipment operability/integrity could be challenged well before reaching MODE 3 within

7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />; therefore, the staff requires additional information to find that the proposed TS change is acceptable.

Request Provide a discussion and justification of the measures, mitigation, or procedures that TVA will implement to assure a safe shutdown of both WBN units after the loss of both trains of CREATCS when the MCR temperature starts at 90 °F.

EMIB-RAI-1 Regulatory Basis GDC 4, Environmental and dynamic effects design bases, states, in part, that [t]hese structures, systems, and components shall be appropriately protected against dynamic effects, including the effects of missiles, pipe whipping, and discharging fluids, that may result from equipment failures and from events and conditions outside the nuclear power unit.

Issue In Section 3.2, MCR Temporary Chilled Water Equipment Description, of the Enclosure to the LAR, TVA stated that a temporary nonsafety-related chiller system will be installed and used to support MCR cooling during the CREATCS chiller replacements, and that the temporary system is capable of providing adequate cooling to maintain the MCR within its normal temperature band.

In addition, in Section 3.2.1, MCR Temporary Air Conditioning Equipment Description, TVA stated that the temporary chiller equipment is nonsafety-related, but appropriate measures will be taken to minimize the potential for failure of the temporary chiller system and the control room envelope (CRE) boundary. In particular, TVA stated that the temporary hoses, pipe, and fittings are qualified for adequate pressure to protect against rupture and pipe whip, and that the valves at the penetrations are qualified for seismic retention to maintain the integrity of the control room envelope boundary. However, the TVA did not provide sufficient information to substantiate the above two statements.

The NRC staff notes that the temporary chiller equipment installation, though nonsafety-related, supports the safety function of MCR cooling during the CREATCS chiller replacements.

Request

a. Provide details on the qualification of the temporary hoses, pipe, and fittings for adequate pressure and any other applicable loads to protect against rupture and pipe whip.

b. Describe the rupture and pipe whip effects that have been considered.

c. Describe how the valves at the penetrations will be qualified for seismic retention to maintain the integrity of the CRE boundary including a description of the seismic effects that would be considered.

STSB-RAI-1 Regulatory Basis In 10 CFR 50.36, Technical specifications, the NRC established its regulatory requirements related to the content of TSs. Pursuant to 10 CFR 50.36, TSs are required to include items in the following categories: (1) safety limits, limiting safety system settings, and limiting control settings; (2) LCOs; (3) surveillance requirements; (4) design features; and (5) administrative controls. The regulation does not specify the particular requirements to be included in a plants TSs.

The regulation at 10 CFR 50.36(a)(1) states, in part, A summary statement of the bases or reasons for such specifications shall also be included in the application, but shall not become part of the technical specifications.

As required in 10 CFR 50.36(b), the technical specifications will be derived from the analyses and evaluation included in the safety analysis report, and amendments thereto.

As required in 10 CFR 50.36(c)(2), LCOs are the lowest functional capability or performance level of equipment required for safe operation of the facility. When LCOs are not met, the licensee shall shut down the reactor or follow any remedial action permitted by the TSs until the LCOs can be met.

Issue In Section 3.7 of the Enclosure to the LAR, TVA concluded that a one-time change of the TS 3.7.11 Completion Times is acceptable and stated:

The proposed one-time LAR in support of the modifications to the CREATCS trains is acceptable based on the compensatory measures and the low probability of an event requiring MCR isolation, the consideration that the remaining train can provide the required protection, and that alternate non-safety related cooling means are available.

The proposed footnote for Condition A Completion Time stipulates that the allowance for a 60 day inoperability for one CREATCS train is contingent on implementation of compensatory measures as described in TVA letter CNL-20-012. The proposed footnote for Condition E Completion Time allows monitoring temperatures in lieu of immediate entry into LCO 3.0.3 but does not contain a similar contingency requiring implementation of compensatory measures as described in TVA letter CNL-20-012.

Request Explain why requiring implementation of compensatory measures such as those described in TVA letter CNL-20-012 is not necessary for the footnote for Condition E Completion Time.