ML18292A874

SMR DC Docs - Public-Closed Meeting on October 25, 2018, on NuScale EPZ Sizing Methodology TR - NRC Staff Talking Points

ML18292A874
Person / Time
Site:	NuScale
Issue date:	10/19/2018
From:	NRC
To:	NRC/NRO/DLSE/LB1
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Download: ML18292A874 (3)

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NuScaleDCDocsPEm Resource From: Chowdhury, Prosanta Sent: Friday, October 19, 2018 4:22 PM To: NuScaleDCDocsPEm Resource

Subject:

Public-Closed Meeting on October 25, 2018, on NuScale EPZ Sizing Methodology TR -

NRC Staff Talking Points Attachments: Public-Closed Meeting on October 25, 2018, on NuScale EPZ Sizing Methodology TR -

NRC Staff Talking Points.pdf 1

Hearing Identifier: NuScale_SMR_DC_Docs_Public Email Number: 22 Mail Envelope Properties (DM6PR09MB274893DEFA755DBE4D79ED509EF90)

Subject:

Public-Closed Meeting on October 25, 2018, on NuScale EPZ Sizing Methodology TR - NRC Staff Talking Points Sent Date: 10/19/2018 4:21:51 PM Received Date: 10/19/2018 4:21:54 PM From: Chowdhury, Prosanta Created By: Prosanta.Chowdhury@nrc.gov Recipients:

"NuScaleDCDocsPEm Resource" <NuScaleDCDocsPEm.Resource@nrc.gov>

Tracking Status: None Post Office: DM6PR09MB2748.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 3 10/19/2018 4:21:54 PM Public-Closed Meeting on October 25, 2018, on NuScale EPZ Sizing Methodology TR - NRC Staff Talking Points.pdf 154242 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

Licensing Topical Report TR-0915-17772-P, Rev. 1, Methodology for Establishing the Technical Basis for Plume Exposure Emergency Planning Zones at NuScale Small Modular Reactor Plant Sites Talking Points for public meeting with NuScale on October 25, 2018

1. Screening of Seismic Events. Staff does not support a seismic screening based on 1.67 times the ground motion acceleration of the design-basis safe-shutdown earthquake (SSE) because it was not demonstrated this value is consistent with the non-seismic screening criteria.

2. PRA Acceptability: Staff recognizes that this topical report (TR) describes a methodology for COL applicants to establish the design/site-specific plume exposure EPZ. As such, COL applicants will be responsible for demonstrating their PRA is acceptable for this intended use, as required by RG 1.200. However, staff believes it is important to note that should the COL applicant follow the existing guidance in SRP 19.0 and DC/COL ISG-028, this would not be sufficient to demonstrate acceptability because this would be a first of a kind use of a COL PRA and a first of a kind review for staff.

3. Severe Accident Phenomena. TR Sections 3.4.3 Final Classification of Accidents by Severity and 3.8.2 Severe Accident Phenomena include statements there is no physically credible containment failure mechanism other than bypass. These statements are still under review by NRC staff as part of the NuScale DCA review.

4. LRF Screening. The Commission goals for advanced light water reactors (ALWR) include two risk metrics, CDF and LRF. However, this methodology only screens for CDF. Staff would like to understand how the LRF risk metric is considered in this methodology considering RG 1.174 Rev 3 principles to maintain multiple fission product barriers. Staff also notes that the LRF risk profile has a risk peak where 93% of LRF results from a break of CVCS charging line outside of containment/failure of CIVs/failure of non- safety related CFDS. In the current methodology, this event would be screened out.

5. Defense in Depth Attribute Ranking (High, Medium, and Low) and Sequence Screening Rules.

a. Staff does not believe that the quantitative threshold definitions should be rigid dividers; rather, attributes close to thresholds should be subject to increased technical review, An SER Limitation and Condition could be added to state that rankings should be considered on a case-by-case basis.

b. Staff believes the definitions of Low for some of the defense in depth (DID) attributes are either not possible when evaluating sequences that screen into DID considerations (( )) or they are inconsistent with Commission expectations for advanced light water reactors

i. Criterion 1, Attribute on internal initiative event frequency defines Low as >1/module yr ii. Criterion 1, Attribute on external hazard initiating event frequency defines Low as

>1E-2/yr iii. Criterion 3, Attribute on Sequence CDF, considering only safety-related systems defines Low as > 1E-3/module yr iv. Criterion 4, Attribute on containment isolation response defines Low as only check valves

v. Criterion 5, Attribute on Sequence LRF defines Low as LRF >1E-6/yr Staff seeks to understand how these thresholds were set.