ML17100A107

NRR E-mail Capture - Watts Bar, Unit 2 - Final Request for Additional Information Concerning Request to Amend Ice Mass Surveillance Requirements

ML17100A107
Person / Time
Site:	Watts Bar
Issue date:	04/07/2017
From:	Robert Schaaf Plant Licensing Branch II
To:	Arent G, Wells R Tennessee Valley Authority
References
CNL-16-192, MF8993, WBN-TS-16-026
Download: ML17100A107 (5)

Text

NRR-PMDAPEm Resource From: Schaaf, Robert Sent: Friday, April 07, 2017 1:53 PM To: Wells, Russell Douglas; Gordon Arent Cc: Sallman, Ahsan; Beasley, Benjamin; Hon, Andrew

Subject:

Watts Bar, Unit 2 - Final Request for Additional Information Concerning Request to Amend Ice Mass Surveillance Requirements (CAC No. MF8993)

Attachments: FINAL RAIs - Watts Bar 2 Ice Mass Change - MF8993.pdf On March 23, 2017, the U.S. Nuclear Regulatory Commission (NRC) staff sent the Tennessee Valley Authority draft Requests for Additional Information (RAIs) via e-mail. These RAIs relate to TVAs license amendment request (LAR) dated December 21, 2016 (ADAMS Accession No. ML16356A673), that would revise the containment ice mass limits in Watts Bar Nuclear Plant (WBN), Unit 2, Technical Specification (TS)

Surveillance Requirements (SRs) 3.6.11.2 and 3.6.11.3 to be identical to the ice mass limits in the WBN, Unit 1, TS SRs 3.6.11.2 and 3.6.11.3.

An RAI clarification call was held on April 6, 2017. The final RAIs, modified from the March 23, 2017, draft to remove proprietary information identified by TVA, are attached to this e-mail.

During the April 6, 2017, clarification call the licensee agreed to provide a response to the final RAIs within 45 days, which is May 22, 2017.

If you have any questions, please contact me at 301-415-6020 or Robert.Schaaf@nrc.gov.

Regards, Robert G. Schaaf Robert G. Schaaf Senior Project Manager, Watts Bar/Bellefonte

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Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop O-8G9A Washington, DC 20555

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301-415-6020 (o)

Robert.Schaaf@nrc.gov 1

Hearing Identifier: NRR_PMDA Email Number: 3431 Mail Envelope Properties (Robert.Schaaf@nrc.gov20170407135200)

Subject:

Watts Bar, Unit 2 - Final Request for Additional Information Concerning Request to Amend Ice Mass Surveillance Requirements (CAC No. MF8993)

Sent Date: 4/7/2017 1:52:33 PM Received Date: 4/7/2017 1:52:00 PM From: Schaaf, Robert Created By: Robert.Schaaf@nrc.gov Recipients:

"Sallman, Ahsan" <Ahsan.Sallman@nrc.gov>

Tracking Status: None "Beasley, Benjamin" <Benjamin.Beasley@nrc.gov>

Tracking Status: None "Hon, Andrew" <Andrew.Hon@nrc.gov>

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

Tracking Status: None "Gordon Arent" <garent@tva.gov>

Tracking Status: None Post Office:

Files Size Date & Time MESSAGE 1516 4/7/2017 1:52:00 PM FINAL RAIs - Watts Bar 2 Ice Mass Change - MF8993.pdf 47489 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

REQUESTS FOR ADDITIONAL INFORMATION OFFICE OF NUCLEAR REACTOR REGULATION LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATIONS REGARDING ICE CONDENSER CONTAINMENT ICE MASS REQUIREMENTS TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-391 (CAC NO. MF8993)

By letter dated December 21, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML16356A673), Tennessee Valley Authority (TVA), the licensee, submitted a License Amendment Request (LAR) for Watts Bar Nuclear Plant (WBN), Unit 2.

The proposed change would revise the ice mass limits in Technical Specification (TS)

Surveillance Requirements (SRs) as follows:

x Revise SR 3.6.11.2 to change the total weight of stored ice from greater than or equal to

() 2,750,700 pounds (lb) to 2,404,500 lb.

x Revise SR 3.6.11.2 to change the ice limit of each basket from 1,415 lb to 1,237 lb.

x Revise SR 3.6.11.3 to change the average ice weight of the sample baskets from 1,415 lb to 1,237 lb.

After reviewing the LAR, the Reactor Systems Branch (SRXB) staff is requesting responses to the following Requests for Additional Information (RAIs) to complete its review:

SRXB-RAI 1 WCAP-17721-P-A, Table 4-1, item 7, regarding reactor internals heat transfer, under the heading Sources of Energy, 10 CFR 50, Appendix K, I.A states:

Reactor Internals Heat Transfer - Heat transfer from piping, vessel walls, and non-fuel internal hardware shall be taken into account.

The hot metal in the reactor coolant system consists of the reactor vessel, reactor internals, reactor coolant system piping and all other non-fuel metal hardware. Tables 1 and 2 of the LAR do not provide a comparison of the mass and the material properties of the following parameters for WBN Units 1 and 2 which would affect the mass and energy (M&E) release to the containment: (a) reactor internals, (b) reactor vessel, (c) reactor coolant system (RCS) piping, and (d) RCS fluid. Provide a quantitative comparison of mass and material properties (density, specific heat, and thermal conductivity) of items (a) through (c), and mass of item (d) for WBN Units 1 and 2, and justify that the WBN Unit 1 loss-of-coolant accident (LOCA) containment M&E release from these items is bounding for WBN Unit 2.

SRXB-RAI 2 Describe the modelling of the main steam isolation valves (MSIVs) for WBN Unit 1 with respect to: (a) the starting time to close after event initiation, and (b) valve-specific time to fully close. In the event that items (a) and (b) differ between WBN Units 1 and 2 due to differences in valve characteristics, different valve manufacturers, or both, provide a comparison of items (a) and (b) for WBN Units 1 and 2, and justify that the WBN Unit 1 M&E release based on these items would be bounding for Unit 2.

SRXB-RAI 3 In its letter to NRC dated September 11, 2015, Notification of Revised Westinghouse Containment Integrity Analysis, (ADAMS Accession No. ML15254A564), Enclosure 1, Section 1, TVA stated that the LOTIC1 ice condenser containment code, documented in WCAP-8354-P-A, was used to calculate the LOCA containment response for WBN Unit 1. NRC has received the following information in a letter from Westinghouse regarding WCAP-8354-P-A (proprietary) and WCAP-8355-A (non-proprietary), Long Term Ice Condenser Containment Code - LOTIC Code:

A source code inspection revealed that the lower compartment conditions are not included until the end of the depressurization period. It has been determined that the affected portion of the transient is very short, and including the lower compartment conditions in the calculation would have a negligible impact on calculated containment conditions. Code updates regarding this issue would provide no improved transient behavior or influence on the limiting time of the event nor increase in nuclear safety.

The above Westinghouse letter provides the following change in Section 5.2, page 5.2-6 of WCAP-8354-P-A and WCAP-8355-A for the calculation of the containment pressure profile during the phase between the end of blowdown and the establishment of recirculation:

FROM

[1] If the expanding volume is smaller than the lower compartment volume, the system pressure calculation is based on the upper compartment and the ice-filled part of the ice compartment.

[2] If the expanding volume occupies the lower compartment, the pressure calculation then includes the lower compartment conditions.

[3] If the expanding volume fills the lower compartment and the ice-empty part of the ice compartment, this calculation period is terminated.

TO

[1] If the expanding volume is smaller than the lower compartment volume and ice-empty part of the ice compartment, the system pressure calculation is based on the upper compartment and the ice-filled part of the ice compartment.

[2] If the expanding volume occupies the lower compartment, the pressure calculation then includes the lower compartment conditions.

[3] If the expanding volume fills the lower compartment and the ice-empty part of the ice compartment, this calculation period is terminated.

Westinghouse did not provide a quantitative basis for its determination that the changes to correct the discrepancy between the description of the methodology and its implementation in the LOTIC code would have a negligible impact on the calculated containment response.

Therefore, the NRC staff requests the following for Watts Bar Units 1 and 2:

(a) The addition of ice-empty part of the ice compartment in item [1] above appears to be a significant change in the total volume (lower compartment volume + ice-empty volume) which is compared with the expanding volume, because the ice-empty volume varies from zero (or a small volume) to the full volume of the ice-compartment during the depressurization phase. Provide a quantitative impact of this change on the entire pressure response, including the peak pressure, by performing a sensitivity analysis for WBN Unit 1, and provide justification that the results apply to Unit 2.

(b) Describe the impact on the WBN, Units 1 and 2, containment pressure, containment temperature, and sump temperature responses and their peak values due to the deletion of item [2] If the expanding volume occupies the lower compartment, the pressure calculation then includes the lower compartment conditions, and provide quantitative results.