ML20114E216

Summary of the April 1, 2020, Category 1 Public Teleconference with NuScale Power, LLC to Discuss the Emergency Core Cooling System Boron Distribution of the Design Certification Application

ML20114E216
Person / Time
Site:	NuScale
Issue date:	05/04/2020
From:	Mary Johnson NRC/NRR/DNRL/NRLB
To:	Michael Dudek NRC/NRR/DNRL/NRLB
Vera Amadiz M
References
Download: ML20114E216 (11)

Text

May 04, 2020 MEMORANDUM TO:

Michael I. Dudek, Chief New Reactor Licensing Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation FROM:

Marieliz Johnson, Project Manager /RA/

New Reactor Licensing Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation

SUMMARY

OF THE APRIL 1, 2020, CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC TO DISCUSS THE EMERGENCY CORE COOLING SYSTEM BORON DISTRIBUTION OF THE DESIGN CERTIFICATION APPLICATION On April 1, 2020, representatives from the U.S. Nuclear Regulatory Commission (NRC) and NuScale Power, LLC (NuScale), held a Category 1 public teleconference meeting to discuss Emergency Core Cooling System (ECCS) Boron Distribution of the NuScale Design Certification Application. Participants included personnel from the NRC, NuScale and members of the public.

The public meeting notice can be found in the Agencywide Documents Access and Management Systems (ADAMS) under Accession No. ML20091M018. This meeting notice was also posted on the NRC public website located at https://www.nrc.gov/reactors/new-reactors/design-cert/nuscale/documents.html.

The Meeting Agenda, List of Participants, and NuScales Public meeting presentation can be found in Enclosures 1,2, and 3 respectively.

During the April 1, 2020, teleconference meeting, NuScale discussed its presentation (Enclosure 3). NuScale determined that under certain conditions, ECCS actuated later than expected and resulted in a higher containment water level accumulation than is considered in the previous analysis. NuScales proposed resolution is implementing a design change to ECCS actuation, which will be modified to actuate earlier to eliminate potential concerns related to containment water level accumulation and downcomer dilution. More information on the background is discussed in the March 9, 2020, public teleconference meeting summary (ADAMS Accession No. ML20097C229).

CONTACT: Marieliz Johnson, NRR/DNRL 301-415-5861

Some technical questions requested by the NRC staff, that are expected to be addressed as part of the ongoing audit from NuScale are summarized as follows:

1.

Which model does NuScale plan on using, Loss of coolant accident (LOCA) or the long-term cooling (LTC) model? The NRC staff pointed out that the figure of merit (FOM) for the water level difference between containment and reactor coolant system (RCS) downcomer is different from the figure of merit of LOCA analysis (critical heat flux (CHF) and collapsed reactor pressure vessel (RPV) water level) and using the existing LOCA or LTC model adequacy must be addressed.

2.

The break spectrum is the same as Chapter 15.6.5. However, the NRC staff believes that the limiting case could be a steam space small break LOCA case or decay heat removal system (DHRS) extended operation with the riser uncover.

3.

NuScale will evaluate the 65 degrees Fahrenheit pool using the LOCA TR model (item

1) long enough to actuate the ECCS for small break LOCA cases without the code failing to execute.

4.

NuScale will use a range of different inputs, which are different from the LOCA minimum level FOM calculation, to evaluate the adequacy of the new setpoints (e.g., decay heat, break model, containment vessel (CNV) condensation model). The NRC staff needs to consider other modeling changes such as a bypass model (item 1).

5.

Nuscale will evaluate or justify the Request for Additional Information (RAI) 8930 response for conditions upon ECCS actuation at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> timer) for the extended DHRS operation.

6.

NuScale will also evaluate extended DHRS operation out to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, including diluted downcomer water entering the core at the boil-off rate (potential DHRS Pcrit evaluation).

NuScale indicated that no significant downcomer dilution occurs out to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

7.

NuScale will evaluate if the ECCS valves could close at different times causing a potential diluted slug entering the core. Nuscale believes that the new setpoint will not affect the Inadvertent Actuation Block (IAB) block function and that all valves will remain open. This does not answer the question of differences in the main valve opening times based on the CNV level or low RCS pressure setpoints.

8.

NuScale will evaluate the new ECCS setpoints on the CNV and RPV water level difference and the potential response for an inadvertent opening of an RPV valve (IORV) of a reactor vent vessel (RVV).

9.

Discussion of extended DHRS operation recovery actions FSAR markups will be discussed later.

NuScale discussed the different chapters, technical reports and topical reports that this design change will impact. Currently, the design change will impact a total of six chapters and even though Chapter 19 is not listed, it may also be updated. NuScales target date for having the

changes to the chapters for its audit review is from April 23, 2020 through May 6, 2020. Final DCA changes are planned to be submitted on the docket on May 20, 2020. This delay may impact our current review schedule.

Docket No.52-048

Enclosures:

As stated cc w/encls.: DC NuScale Power, LLC Listserv

ML20114E216

• via e-mail NRR-106 OFFICE NRR/DNRL/NRLB: PM NRR/DNRL/NRLB: LA NRR/DNRL/NRLB: PM NAME MJohnson CSmith MJohnson DATE 4/27/2020 5/04/2020 5/04/2020

U.S. NUCLEAR REGULATORY COMMISSION CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC TO DISCUSS THE EMERGENCY CORE COOLING SYSTEM BORON DISTRIBUTION OF THE DESIGN CERTIFICATION APPLICATION Meeting Agenda April 1, 2020 2:00 p.m. - 3:30 p.m.

Time Topic 2:00 p.m. - 2:15 p.m.

Welcome and Introductions 2:15 p.m. - 2:40 p.m.

Technical discussion 2:40 p.m. - 2:50 p.m.

Public - Questions and Comments 2:50 p.m. - 3:30 p.m.

Closed Portion 3:30 p.m.

Adjourn

U.S. NUCLEAR REGULATORY COMMISSION CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC TO DISCUSS THE EMERGENCY CORE COOLING SYSTEM BORON DISTRIBUTION OF THE DESIGN CERTIFICATION APPLICATION List of Attendees April 1, 2020 NAME AFFILIATION Marieliz Johnson U.S. Nuclear Regulatory Commission (NRC)

Rebecca Patton NRC Michael Dudek NRC Bruce Bavol NRC Joseph Donoghue NRC Dinesh Taneja NRC Jeffrey Schmidt NRC Ryan Nolan NRC Thomas Scarbrough NRC Shanlai Lu NRC Omid Tabatabai-Yazdi NRC Marie Pohida NRC Stacey Rosenberg NRC Gregory Cranston NRC Joseph Ashcraft NRC Tony Nakanishi NRC Alissa Neuhausen NRC Carl Thurston NRC Dawnmathews Kalathiveettil NRC Matthew Presson NuScale Power, LLC (NuScale)

Mike Melton NuScale Ben Bristol NuScale Meghan McCloskey NuScale Taylor Coddington NuScale Morris Byram NuScale Marty Bryan NuScale Andy Lingenfelter NuScale Paul Infanger NuScale Brian Arnholt NuScale Sarah Bristol NuScale Scott Patterson NuScale Vern Hull NuScale NAME AFFILIATION Karl Gross NuScale Jim Curry NuScale Rebecca Norris NuScale Zack Rad NuScale Tom Bergman NuScale Robert Gamble NuScale Pravin Sawant NuScale Gary Becker NuScale Cindy Williams NuScale Steve Pope NuScale Adam Brigantic NuScale Sarah Fields Public