Text

M210413: Presentation Materials - Lyman - Ucs Perspectives on NRC Licensing of Advanced Reactor and Fuels
	ML21097A031
Person / Time
Issue date:	04/13/2021
From:	; NRC/OCM
To:	;
Shared Package
ML21097A028	List: ML21097A031; ML21097A032;
References
	M210413
	Download: ML21097A031 (15)
	v • d • e

UCS Perspectives on NRC Licensing of Advanced Reactors and Fuels Dr. Edwin Lyman Director of Nuclear Power Safety Climate and Energy Program Union of Concerned Scientists April 13, 2021

Advanced Isnt Always Better (March 2021)

New UCS report documents serious safety and security issues with non-light-water reactor (NLWR) designs

Our research does not substantiate the notion that any NLWR we considered

- meets the Advanced Reactor Policy Statements expectation for enhanced safety margins

- warrants the broad weakening of regulatory standards that the NRC is considering 2

ARDP goal:

commercial reactors

The Congressionally mandated timeline for startup of NRC-licensed facilities under the Advanced Reactor Demonstration Program (ARDP) by 2027 is very aggressive

- ARDP calls for commercial demonstration plants

- Clear implication is that the purpose of these facilities will be to produce electrical power and serve as models for subsequent commercial units

Chris Levesque (TerraPower): A big piece of the private investment will be the revenue stream (NIC Summit, 3/23/21)

Clay Sell (X-Energy): We are demonstrating a full-scale commercial plant just like the plant we will sell (Senate testimony, 3/25/21) 3

NRC licensing of demonstration reactors But the NRC has not yet determined whether the criteria of 10 CFR 50.43(e) can be satisfied for a DC, COL, or OL without acceptable testing of prototype plants for either the Natrium SFR or Xe-100 HTGR designs During preapplication reviews in the 1990s, the NRC expected prototype testing for both SFRs and HTGRs If the NRC does decide prototype testing is necessary, it must soon determine what additional safety features the prototypes will need, and for how long The NRC must base its licensing timetable on its statutory obligation to protect public health, safety, and securityand should not compromise its standards to meet an arbitrary and unrealistic schedule imposed by Congress 4

Need for prototype testing

UCS does not believe that the ARDP designs are mature enough to be safely, securely, and reliably deployed as commercial power reactors on the current schedule

- Applies to basic designs as well as fuels and materials

Past demonstration reactors were not sufficiently representative of currently proposed designs to provide adequate support for NRC licensing decisions: thus prototype testing will be needed

Premature commercial deployment poses safety risks with regard to

- reluctance to carry out required testing that might affect revenue

- the impact of grid requirements on reactor operation (e.g. flexible power operations at Columbia Generating Station) 5

SFR design comparison EBR-II Natrium Power level 62.5 MWth 840 MWth Driver fuel HALEU (19% U-235)

HEU (50-80% U-235)

Blanket fuel Yes No Sodium void worth negative positive Primary coolant pumps centrifugal (+ 1 auxiliary electromagnetic) electromagnetic only Emergency shutdown cooling Direct Reactor Auxiliary Cooling System Reactor Vessel Auxiliary Cooling System 6

The myth of SFR passive safety

The positive sodium void worth is a concern in the passive safety argument. Because of it, one must qualify any characterization of the PRISM response as passively safe by pointing out that this is conditional on the sodium remaining below the boiling temperature.

Should sodium boiling begin on a core-wide basis under failure-to-scram conditions, the reactor would be likely to experience a severe power excursion. - NUREG-1368 7

NUREG-1368 on the need for a PRISM prototype The DOE/GE approach for the PRISM is to build a prototype reactor test facility given the uncertainties in the reactivity feedbacks and the degree to which these feedbacks are dependent on the design of the reactor, this is clearly the preferred approach.

Similarly, the review of a design without a conventional containment building was based on a mechanistic analysis of a range of probability events and on the potential for demonstrated capability of the design (via prototype testing) to perform as predicted.

8

HTGR design comparison THTR Fort St. Vrain Xe-100 Power level 750 MWth 840 MWth 200 MWth (x4)

Reactor type Pebble-bed Prismatic-block Pebble-bed Fuel type/

composition BISO (Th,U)O2 TRISO (Th,U)C2 TRISO UCO U enrichment HEU HEU HALEU (15.5% U-235)

Average burnup

< 6%

~ 13% (fissile)

> 17%

Emergency shutdown cooling Active Active Passive (Reactor Cavity Cooling System)

Pressure vessel prestressed concrete prestressed concrete steel 9

Xe-100 violates well-established safety limits

Peak fuel temperature following an HTGR depressurized loss-of-coolant accident must remain below 1600°C to ensure TRISO fuel integrity

However, this temperature limit is apparently exceeded for the 200 MWth Xe-100 10

11 Mulder, E.J., and W.A. Boyes. 2020. Neutronics Characteristics of a 165 MWth Xe-100 Reactor.

Nuclear Engineering and Design 357: 110415.

NUREG-1338 on the need for an MHTGR prototype

Based on judgments of the adequacy of existing operating experience, the novel design features proposed, and the status of the present technology base, the staff requires that testing and operation of a prototype test reactor, located at an isolated site, be mandatory before design certification.

Acceptance of a design without a containment building would require demonstration via a full-size prototype test at an isolated site of the fission product-retention capability of the design.

12

Regulatory engagement plans

A Regulatory Review Roadmap for Non-Light Water Reactors (December 2017):

- Prospective developers and applicants are encouraged to work as early as possible with the NRC to clearly define the testing to be performed in a prototype plant, including expected results and associated criteria, and to determine how to address the licensing of a prototype plant and prototype testing in the regulatory engagement plan.

If the NRC has not already done so, it should immediately begin this discussion with the ARDP participants to address the need for prototype testing 13

Recommendations

The NRC should define the additional design features that both ARDP demonstration plants must have to ensure public health and safety during the prototype testing phases