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LLC - Submittal of Presentation Materials Entitled NRC Public Meeting: Revisions to Nuscale'S EPZ Sizing Methodology Topical Report, PM-0420-69598, Revision 0
	ML20099H080
Person / Time
Site:	NuScale
Issue date:	04/08/2020
From:	Rad Z; NuScale
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	LO-0420-69607
	Download: ML20099H080 (25)
	v • d • e

LO-0420-69607 April 8, 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 NRC Public Meeting: Revisions to NuScales EPZ Sizing Methodology Topical Report, PM-0420-69598, Revision 0 NuScale Power, LLC (NuScale) has requested a meeting with the NRC technical staff on April 15, 2020, to discuss revisions made to the Emergency Planning Zone (EPZ) topical report. NuScale had previously requested that the NRC suspend review of Revision 1 of the EPZ topical report in order to consider staff and public feedback from prior meetings and to review Commission votes on key EPZ-related activities.

The purpose of this submittal is to provide presentation materials to the NRC for use during this meeting. The enclosure to this letter is the nonproprietary presentation entitled NRC Public Meeting: Revisions to NuScales EPZ Sizing Methodology Topical Report, PM-0420-69598, Revision 0.

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

If you have any questions, please contact Deb Luchsinger at 541-452-7334 or at DLuchsinger@nuscalepower.com.

Sincerely, Zackary W. Rad Director, Regulatory Affairs NuScale Power, LLC Distribution: Gregory Cranston, NRC, OWFN-8H12 Michael Dudek, NRC, OWFN-8H12 Prosanta Chowdhury, NRC, OWFN-8H12 Getachew Tesfaye, NRC, OWFN-8H12

Enclosure:

NRC Public Meeting: Revisions to NuScales EPZ Sizing Methodology Topical Report, PM-0420-69598, 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-0420-69607

Enclosure:

NRC Public Meeting: Revisions to NuScales EPZ Sizing Methodology Topical Report, PM-0420-69598, 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 NRC Public Meeting Revisions to NuScales EPZ Sizing Methodology Topical Report Scott Weber EPZ Technical Lead April 15, 2020 1

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Outline

Background

Goals of Revision 2 of EPZ topical report

Significant modifications in Revision 2

Other modifications made for consistency

Open discussion 2

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Background and Goals 3

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Background

Rev. 0 EPZ topical report submitted Dec. 2015 and accepted for review in March 2016

Rev. 1 topical report submitted March 2018 (ML18071A354)

Since submittal of Rev. 1, three public meetings (Oct. 18, 2018, March 5, 2019, and Aug. 6, 2019 [meeting summary ML19233A165]) and one round of RAIs (RAI No. 9666, submitted by staff March 22, 2019)

- Primary areas of discussion: PRA technical adequacy, defense-in-depth, seismic event screening, severe accident phenomena, and dose criteria for most probable accidents

- Based on the Aug. 6 meeting summary, the topics of PRA technical adequacy and severe accident phenomena have been substantially resolved 4

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Background

NuScale requested in late 2019 that NRC suspend review of Revision 1 of the EPZ topical report in order to:

- Consider staff and public feedback from prior public meetings

- Review Commission decisions on key EPZ-related activities:

Ongoing NRC EP rulemaking, which signals a policy recognition of the need for alternative risk informed bases to determine the EPZ size for new nuclear technologies including SMRs

Approved TVA Clinch River Early Site Permit (ESP) that contains a methodology to determine plume-exposure EPZ sizing

- Interface with industry, including NEI, TVA, and other advanced nuclear reactor designers, to ensure alignment behind proposed methods

- Further review the existing EPZ basis in NUREG-0396, including replicating results based on WASH-1400, and other existing regulatory framework

Since the Aug. 2019 NRC public meeting, NuScale has spent over 1500 staff and management hours developing revisions to the EPZ methodology 5

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Goals of Revision 2

Align with most recent NRC emergency preparedness (EP) regulatory precedents and guidance

- NRC ongoing EP rulemaking (ML19351C731)

- TVAs approved ESP methodology (ML19351D663)

- EPZ exemptions at decommissioned nuclear reactor sites and associated ongoing rulemaking

The exemptions use similar technical basis, most recent example is Pilgrim nuclear power plant (ML18347A717)

Ensure consistency within the NuScale methodology

Clarify distinction between EPZ methodology and NuScales DCA

Develop methodology supported by nuclear industry, including NEI, TVA, and other advanced nuclear reactor designers 6

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Significant Modifications in Revision 2 7

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Defense-in-Depth Update

Revision 1 Methodology

- Quantitative methodology for sequence-based assessment of defense-in-depth (DID) (Section 3.5)

Revision 2 Methodology

- New topical report Section 3.9 - Qualitative, plant-level DID evaluation, independent from accident screening process

- Identify key SMR characteristics (unique design features and SSCs) that enhance protection of public health and safety by preventing and mitigating the consequences of postulated accidents

- Remove quantitative methodology, and associated screening criteria at 1E-3 x Total CDF 8

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Defense-in-Depth Update

Emphasizes need for balance between accident prevention and ability to mitigate postulated consequences

Consistent with RG 1.174 and INSAG-10

Consistent with ongoing NRC EP rulemaking

- The draft rules discussion of DID states that the rationale upon which EP for current reactor designs is based is consistent with the Commissions defense-in-depth safety philosophy. (ML19351C731)

Consistent with NRCs decision-making process for approving licensing amendments for operating fleet 9

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External Event Screening Update

Revision 1 Methodology (for seismic sequences)

- Based on the results of a seismic margins assessment, screen seismic sequences at an acceptance criteria of 1.67 x SSE (0.84g for the NuScale design)

Revision 2 Methodology

- Require a seismic PRA, similar to other external events

- Apply the same sequence CDF screening threshold (1E-7/module year, Slide 13) to external events as applied to internal events

- Apply an additional initiator screening threshold for all external events -

screening external initiators at a 1E-5/year exceedance frequency, unless alternate endorsed criteria exist

For example, only seismic core damage sequences resultant from a peak ground acceleration (pga) which occurs at frequency of 1E-5/year or greater would be retained for screened based on CDF at 1E-7/module year.

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External Event Screening Update

EPZ exemptions have been granted for decommissioning plants based on a maximum credible earthquake

- The underlying technical and regulatory basis is appropriate for all external events, not just seismic

Technical basis for approving these exemptions is found in NUREG-1738 and NUREG-2161

- NUREG-2161 cited an earthquake at frequency of 1.7E-5/y as stronger than the maximum earthquake reasonably expected to occur for the reference plant. Less likely earthquakes were not considered in the analysis

- NUREG-2161 demonstrates that a more severe, and lower likelihood, earthquake would produce greater consequences

- NUREG-1738 states that pre-planning for large (>0.5g) earthquakes would have marginal benefit due to extensive collateral damage offsite

All-hazards off-site plans will exist and will function to respond to an extreme external event

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CDF Screening Update

Revision 1 Methodology

- PRA sequence-level single module screening at 1E-08 per module year

Sequences < 1E-08 per year but > Total CDF x 1E-3 have sequence-level defense-in-depth evaluation

Sequences < Total CDF x 1E-03 screen out

Revision 2 Methodology

- PRA sequence-level single module screening at 1E-07 per module year

No conditional screening threshold; not required for qualitative DID evaluation

Sequences < 1E-07 per module year screen out 12 PM-0420-69598 Revision: 0 Copyright 2020 by NuScale Power, LLC.

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CDF Screening Update

The draft EP rulemaking requires use of a spectrum of credible accidents for the facility as the basis for EPZ size

TVAs ESP methodology uses screening thresholds of 1E-6/rx-yr for less severe accidents, and 1E-7/rx-yr for more severe accidents

- Screening all sequences in the NuScale methodology at 1E-7/module year is consistent with the TVA threshold approved to determine EPZ sizing

1E-7/module year is also consistent with NRC guidance and previous analysis, such as NUREG-1860 and NUREG-1935 (SOARCA)

1E-7/module year meets the NRCs quantitative health objectives to be less that 0.1 percent of non-nuclear fatality risks

- Prompt and cancer fatality rates for the general public are greater than 1E-4/year, and therefore greater than 1E-7 multiplied by 0.1 percent 13 PM-0420-69598 Revision: 0 Copyright 2020 by NuScale Power, LLC.

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Surrogate Less Severe Accidents

Revision 1 Methodology

- If all less severe accidents screen out based on CDF, requirement to include most probable less severe accident

Revision 2 Methodology

- Requirement for surrogate less severe accident removed, because design basis source term used for Ch. 15 off-site dose analysis is always required to be analyzed (Section 3.3)

This source term represents a conservative less-severe core damage sequence

Therefore, the required inclusion of an additional less-severe sequence is a redundant unnecessary step

Revision also serves as an incentive for a future applicant of this methodology to demonstrate that all accidents are low frequency 15 PM-0420-69598 Revision: 0 Copyright 2020 by NuScale Power, LLC.

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Aggregate of Screened Out Sequences

Revision 1 Methodology

- Summed the CDF of all screened out accidents, and if the sum exceeded 1E-8, require additional sequences to go into DID screening

Revision 2 Methodology

- No check on screened out accident sequences in aggregate

Previous method is inconsistent with revised DID evaluation

Aligned with the approved methodology in TVAs ESP, which does not require an additional check on screened-out sequences 16 PM-0420-69598 Revision: 0 Copyright 2020 by NuScale Power, LLC.

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Other Changes

Multi-module methodology frequency screening changed from 1E-3 x Total CDF to 1E-7/module year for multi-module sequences

- Aligned with single module screening

Clarifies distinction between the methodology and the DCA and DC PRA. For example:

- Updated definitions of the PRA used in the application of the methodology

- Revised sections on spent fuel pool and security which were previously based on DCA results; these are now presented as examples to be confirmed. No change to content.

Additional comparisons to NUREG-0396

Update to background to reflect ongoing NRC EP rulemaking and approved TVA ESPA

Removal of information in appendices which is no longer consistent with revised methodology.

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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 19 PM-0420-69598 Revision: 0 Copyright 2020 by NuScale Power, LLC.

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Overall EPZ Process Flowchart PRA Input DBA Input Note: Double-lined All Internal and Design Basis boxes represent a External Events Source Term method further defined Sequences (Section 3.3) in a separate diagram.

Single Module Determine severity Screening Source Term of screened in Dose Evaluation Process Evaluation sequences (Section 4.2)

(Sections 3.4 (Section 4.2)

(Section 3.4.3) and 3.5)

Uncertainty Multi-Module Analysis Screening (Section 4.3)

Process DBA and Less Severe (Section 3.6) Determine distance(s) where Dose Criteria a and b are exceeded (Section 3.2)

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Single Module Screening Flowchart Start Notes:

Compile Sequences (1) Curved boxes represent a transfer to (Section 3.4.1) or from the overall EPZ method.

Internal event sequence, or external No Screened out event sequence with initiator >1E-05?

Yes No End Is sequence Return to overall frequency process with screened

>1E-7?

in sequence(s)

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Multi-Module Screening Flowchart Start Single Module Sequence Initiators Note: Curved boxes represent a transfer to or from the overall EPZ method.

Does the initiator contain a site-wide or No Yes multi-module initiator?

(Section 3.6.1)

Potential initiator propagation to Treat initiator as Yes other modules? multi-module (Section 3.6.1)

No Does the initiator:

Limit analysis to

1) directly compromise independent single-module effects safe shutdown functions in multiple Screened out in accordance with No modules? (Section 3.6.2), or existing regulatory

2) fail a coupled safe shutdown framework function? (Section 3.6.3)

No Determine:

Is sequence 1) all multi-module sequences Yes frequency that result from initiating

>1E-07? events, and (Section 3.6.4) 2) sequence frequency (Section 3.6.4)

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