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LLC Submittal of Presentation Materials Entitled ACRS Full Committee Presentation: NuScale Topic - Boron Redistribution and General Design Criterion 33, PM-0720-70785, Revision 0
	ML20184A287
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Site:	NuScale
Issue date:	07/01/2020
From:	Rad Z; NuScale
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	LO-0720-70826 PM-0720-70785, Rev 0
	Download: ML20184A287 (15)
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LO-0720-70826 July 1, 2020 Docket No.52-048 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738

SUBJECT:

NuScale Power, LLC Submittal of Presentation Materials Entitled ACRS Full Committee Presentation: NuScale Topic - Boron Redistribution and General Design Criterion 33, PM-0720-70785, Revision 0 The purpose of this submittal is to provide presentation materials to the NRC for use during the upcoming Advisory Committee on Reactor Safeguards (ACRS) NuScale Full Committee Meeting on July 8, 2020. The materials support NuScales presentation of boron redistribution and General Design Criterion 33.

The enclosure to this letter is the nonproprietary presentation entitled ACRS Full Committee Presentation: NuScale Topic - Boron Redistribution and General Design Criterion 33, PM-0720-70785, Revision 0.

This letter makes no regulatory commitments and no revisions to any existing regulatory commitments.

If you have any questions, please contact John Fields at 541-452-7425 or at JFields@nuscalepower.com.

Sincerely, y,

Zackary W. Rad

Director, Di t R Regulatory l t Affairs Aff i NuScale Power, LLC Distribution: Robert Taylor, NRC

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Michael Snodderly, NRC Christopher Brown, NRC Gregory Cranston,NRC

Michael Dudek, NRC

Enclosure:

ACRS Full Committee Presentation: NuScale Topic - Boron Redistribution and General Design Criterion 33, PM-0720-70785, Revision 0 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360-0500 Fax 541.207.3928 www.nuscalepower.com

LO-0720-70826

Enclosure:

ACRS Full Committee Presentation: NuScale Topic - Boron Redistribution and General Design Criterion 33, PM-0720-70785, Revision 0 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360-0500 Fax 541.207.3928 www.nuscalepower.com

NuScale Nonproprietary ACRS Full Committee Presentation NuScale Topic Boron Redistribution and General Design Criterion 33 July 8, 2020 1

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Presenters Rebecca Norris Licensing Supervisor Paul Infanger Licensing Specialist 2

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Agenda

Boron Redistribution Update

Boron Redistribution Audit

Summary of Final Design Changes

DCA Revision 4.1 Boron Redistribution Changes

LOCA Topical Report Boron Redistribution Changes

General Design Criterion 33 DCA Changes

Conclusions 3

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Boron Redistribution Update

During ACRS Full Committee meeting June 3 and 4, 2020, scenarios were discussed that could lead to dilution of fluid in reactor pressure vessel (RPV) downcomer

- under certain conditions, ECCS actuation or restoration of natural circulation flow could transport diluted coolant to the reactor core

- presented design solutions to prevent or mitigate boron redistribution

The purpose of this presentation is to inform the ACRS of additional work, since the June 3 and 4, 2020 meeting, required to complete design changes, changes to associated Topical Reports, and FSAR changes 4

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Boron Redistribution Audit

Audit initiated March 9, 2020

Daily update meetings between NuScale and NRC staff

Numerous technical calls

Docketed twenty-one submittals with design change information, analyses and DCA changes

DCA Revision 4.1 (complete submittal all Parts) June 19, 2020

Public Audit Exit Meeting on Boron Redistribution held June 26, 2020 5

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Summary of Final Design Changes

Design changes to prevent postulated boron dilution sequences New ECS

Addition of four 3/4-inch holes Actuation on RCS in riser at midpoint of steam Pressure generator (SG)

Addition of ECCS actuation on Low RCS pressure

Lowered ECCS actuation ECCS Actuation on CNV Level setpoint on containment vessel (CNV) level 6

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DCA Revision 4.1 Boron Redistribution Changes

DCA Revision 4.1 included boron redistribution FSAR changes made since June 4

- Table 6.3-1 ECCS Actuation and Table 15.0-7 Analytical Limits

Added reference to ECCS actuation signal interlocks in Table 7.1-5

- Section 15.0.5 Long Term Cooling

Added description of riser hole flow path evaluation

Downcomer boron concentration remains above critical boron concentration during DHRS Cooldown for beginning of cycle (BOC) and middle of cycle (MOC)

Minimal impact at end of cycle (EOC) due to low boron concentration 7

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LOCA Topical Report Boron Redistribution Changes

LOCA Topical Report changes (submitted June 19, 2020)

- Added description of ECCS actuation on low RCS pressure

Steam space LOCAs and inadvertent RVV opening and some liquid space LOCAs actuate ECCS on low RCS pressure

Most liquid space breaks and inadvertent RRV actuate ECCS on CNV Level

Earlier ECCS actuation on RCS pressure less limiting for MCHFR and collapsed liquid level above the top of active fuel (TAF)

Existing results remain conservative and bounding

- Added descriptions of ECCS actuation signal interlocks

Low RCS pressure interlocked with RCS hot temperature and CNV pressure

CNV level ECCS actuation interlocked with RCS hot temperature and pressurizer level

Interlocks prevent ECCS actuation for non-LOCA events and expected operational conditions

- Discussed function and impact of riser holes

Minimum and maximum RCS flow unchanged 8

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General Design Criterion 33

General Design Criterion (GDC) 33 requires that a reactor coolant makeup system be available to mitigate small RCS breaks with or without power available

NuScale DCA includes an exemption to GDC 33

- NPM design does not require additional coolant to maintain adequate core cooling for duration of design basis events (DBEs)

- chemical and volume control system (CVCS) makeup system and backup power are not safety-related

- ECCS and containment isolation systems credited to meet intent of GDC 33

ECCS actuates automatically for LOCA spectrum (greater than makeup system capacity and most smaller leaks)

Analysis demonstrates that specified acceptable fuel design limits (SAFDLs) met for small RCS leaks 9

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GDC 33 - DCA Changes

Basis for GDC 33 Exemption enhanced

- DCA Revision 4 only included statement in Section 9.3.4 that GDC 33 was not applicable to NPM design and that makeup from CVCS is not credited

Added basis to FSAR Section 4.3 to support GDC 33 exemption

- Small leaks with no ECCS, boron mixing maintained by riser holes until holes uncovered

- Core concentration remains above initial concentration for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />

Added Basis to FSAR Section 6.3 that intent of GDC 33 is met

- ECCS actuation on setpoints (or by 24-hour timer for events with a loss of AC) mitigates most leaks

- Evaluation shows smaller leaks with cold pool temperature do not challenge SAFDLs

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Summary and Conclusions

Design changes preclude boron redistribution for postulated design basis and beyond design basis events

- ECCS actuation on low RCS pressure or high CNV level

assures initial flow out of RPV to preclude influx of unborated water from CNV or downcomer

- Riser holes assure boron mixing in downcomer and core region

when DHRS cools and shrinks RCS level below the riser

For smaller LOCAs/RCS leaks while RCS level is above holes

To assure core concentration remains above initial concentration

- Basis for GDC 33 added to Chapter 4 and Chapter 6

Function of ECCS and riser holes support exemption to GDC 33

No reliance on CVCS makeup or operator action

SAFDLs met for all RCS leaks 11 PM-0720-70785 Revision: 0 Copyright 2020 by NuScale Power, LLC.

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Acronyms AC - alternating current RRV - reactor recirculation valve ACRS - Advisory Committee on Reactor RVV - reactor vent valve Safeguards SAFDL - specified acceptable fuel design limits BOC - beginning of cycle SG - steam generator CNV - containment vessel TAF - top of active fuel CVCS - chemical and volume control system DCA - Design Certification Application DHRS - decay heat removal system ECCS - emergency core cooling system EOC - end of cycle FSAR - Final Safety Analysis Report GDC - General Design Criteria LOCA - loss-of-coolant accident MCHFR - minimum critical heat flux ratio MOC - middle of cycle NPM - NuScale Power Module RCS - reactor coolant system RPV - reactor pressure vessel 12 PM-0720-70785 Revision: 0 Copyright 2020 by NuScale Power, LLC.

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Portland Office Richland Office 6650 SW Redwood Lane, 1933 Jadwin Ave., Suite 130 Suite 210 Richland, WA 99354 Portland, OR 97224 541.360.0500 971.371.1592 Charlotte Office Corvallis Office 2815 Coliseum Centre Drive, 1100 NE Circle Blvd., Suite 200 Suite 230 Corvallis, OR 97330 Charlotte, NC 28217 541.360.0500 980.349.4804 Rockville Office 11333 Woodglen Ave., Suite 205 Rockville, MD 20852 301.770.0472 http://www.nuscalepower.com Twitter: @NuScale_Power 13 PM-0720-70785 Revision: 0 Copyright 2020 by NuScale Power, LLC.

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