ML20128J316

OEDO-20-00167 - Response to the ACRS Letter on Combustible Gas Monitoring

ML20128J316
Person / Time
Site:	NuScale
Issue date:	05/18/2020
From:	Renee Taylor Office of Nuclear Reactor Regulation
To:	Matthew Sunseri Advisory Committee on Reactor Safeguards
Tesfaye G, NRR.DNRL
Shared Package
ML20122A104	List: ML20128J316
References
OEDO-20-00167
Download: ML20128J316 (3)

Text

May 18, 2020 Mr. Matthew W. Sunseri, Chairman Advisory Committee on Reactor Safeguards U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

SUBJECT:

NUSCALE COMBUSTIBLE GAS MONITORING

Dear Mr. Sunseri:

Thank you for the letter, dated April 28, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20113F049), regarding the Advisory Committee on Reactor Safeguards (ACRS or the Committee) review of the proposed NuScale combustible gas monitoring system to detect hydrogen (H2) and oxygen (O2) concentrations in containment during severe accident events. The Committee has previously issued a recommendation on this matter in a letter dated December 20, 2019 (ADAMS Accession No. ML19354A031); however, the NRC staff appreciates the additional time and effort that the ACRS has devoted to this important subject, as reflected in the meetings held with the ACRS Subcommittee for NuScale on March 4, 2020, and the ACRS Full Committee between April 8 -

10, 2020.

The letter contained the following three conclusions:

1. We concur with the staff position that the combustible gas monitoring system design not receive finality in the NuScale design certification because the staff is unable to evaluate dose implications.

2. We are concerned that to obtain a sample representative of the containment atmosphere, the proposed combustible gas monitoring system design will require establishing a sizeable flow through non-safety-grade piping outside containment. This may have implications on worker and off-site doses.

3. We expect to have the opportunity to review the final design updates submitted by Combined License (COL) applicants to ensure that our concerns have been addressed and are supported by analyses.

The NRC staff appreciates the ACRSs review and understands the concerns regarding the dose implications for obtaining a representative sample of the containment atmosphere.

M. Sunseri The NRC staff further appreciates the Committees independent concurrence with the staffs position that the combustible gas monitoring system design not receive finality in the NuScale design certification because of a lack of sufficient design information needed to evaluate possible dose impacts. The staff expects more detailed design information will be provided as part of future application that will reference the NuScale small modular reactor design. Once that additional information is available, the staff plans to conduct a risk-informed review that considers the likelihood of the event sequences which would necessitate initiating this system, the dose consequences of its operation, and the risks for potentially forming a combustible gas mixture. The staff looks forward to working with the Committee on the review of that future application.

Sincerely,

/RA/

Robert M. Taylor Deputy Office Director of New Reactors Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Docket No.: 52-048 cc: Chairman Svinicki Commissioner Baran Commissioner Caputo Commissioner Wright SECY

PKG: ML20122A104 LTR: ML20128J316 *via e-mail NRR-106 OFFICE DNRL/NRLB:PM DNRL/NRLB:LA DNRL/NRLB: BC NRR/DNRL: D NRR/DDNR NAME GTesfaye CSmith* MDudek* ABradford* RTaylor DATE 05/07/2020 05/11/2020 05/07/2020 05/11/2020 05/18/2020