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Natrium Energy Island Decoupling Strategy - 11-17-2021
	ML21319A245
Person / Time
Site:	Grand Gulf, Arkansas Nuclear, River Bend, Waterford
Issue date:	11/15/2021
From:	; TerraPower
To:	Mallecia Sutton; NRC/NRR/DANU/UARL
	Sutton L
References
	Download: ML21319A245 (18)
	v • d • e

Objectives

Natrium' reactor licensing overview

Natrium reactor safety and plant overview

Explain Decoupling Strategy within the Natrium design SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 2

Natrium Reactor Licensing Overview

Regulatory Engagement Plan submitted 6/8/2021

10 CFR 50 licensing process will be followed

- Construction Permit Application 8/2023

- Operating License Application 3/2026

Numerous pre-application interactions are planned to reduce regulatory uncertainty and facilitate the NRCs understanding of Natrium technology and its safety case

The LMP (NEI 18-04), as endorsed by RG 1.233, will support this application SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 3

Natrium Reactor Licensing Overview

Each pre-application interaction will build upon risk insights from prior interactions to demonstrate the Natrium reactors safety case.

Future Meetings and Presentations include:

- Principal Design Criteria

- Source Term Methodology

Advanced Reactor Demonstration Program

Demonstrate the ability to design, license, construct, startup and operate the Natrium reactor within the Congressionally mandated seven-year timeframe

Include improvements in safety, security, economics, and environmental impacts

Utilize a simple, robust, reliable, and proven safety profile

Lower emissions by initiating the deployment of a fleet of Natrium reactors - Demonstrate that the plants can be built economically and that they will be attractive for future owner/operators SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 5

Natrium Safety Features Control

Pool-type Metal Fuel SFR with Molten Salt Control Energy Island

- Metallic fuel and sodium have high compatibility - Motor-driven control rod runback

- No sodium-water reaction in steam generator - Gravity-driven control rod scram

- Large thermal inertia enables simplified response to - Inherently stable with increased power or abnormal events temperature

Simplified Response to Abnormal Events

- Reliable reactor shutdown Cool

- Transition to coolant natural circulation - In-vessel primary sodium heat transport

- Indefinite passive emergency decay heat removal (limited penetrations)

- Low pressure functional containment

- Intermediate air cooling natural draft flow

- No reliance on Energy Island for safety functions

- Reactor air cooling natural draft flow -

No Safety-Related Operator Actions or Cool always on AC power

Technology Based on U.S. SFR Experience Contain

- EBR-I, EBR-II, FFTF, TREAT - Low primary and secondary pressure

- SFR inherent safety characteristics demonstrated - Sodium affinity for radionuclides through testing in EBR-II and FFTF - Multiple radionuclides retention boundaries Contain SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 6

Demin Water Firewater Turbine Building Steam Generation Standby Diesels Warehouse

& Admin TI Power Distribution Salt Piping Center Rx Aux. Building Inert Gas Shutdown Cooling Rx Building Energy Storage Tanks Control Building Fuel Building NI Power Distribution Center & Controls Fuel Aux. Building SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved.

Plant Overview Reactor Building Reactor Aux. Building Fuel Handling Building Reactor Air Cooling Ducts Refueling Access Area Intermediate Salt Piping to/from Air Cooling Thermal Storage System Sodium Int. loop Ground Level Sodium/Salt HXs Spent Fuel Pool (water)

Head Access Intermediate Sodium Hot Leg Area Intermediate Sodium Cold Leg Reactor Reactor Air Cooling / Reactor Cavity and Core SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 8

Decoupling Strategy

Strategy documents in the Natrium design process

Plant designed with as much independence as practicable between Nuclear Island and Energy Island

Decoupling is used to describe this level of independence, which is enabled using molten salt thermal storage system

Decoupling enables:

- Operational flexibility

- Transient separation

Decoupling Strategy

Molten salt storage tanks eliminate direct coupling of reactor power and turbine output that are inherent in PWR and BWRs SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 11

Operational Flexibility

NI control manages reactor power and cold salt flow to the NI via ESS cold tank pumps

EI control manages turbine output based upon grid demand while maintaining salt tank levels within controlled bands

Alerts notify NI and EI operators when salt tank parameters are outside of control bands

Deviation of parameters outside of controlled band are considered AOOs and will be evaluated via safety analyses

Requirements related to salt tank levels, controlled bands, alert levels, and response times will be verified by initial modeling and reflected throughout design process SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 12

Operational Flexibility

Narrows the scope of NI command and control

- Allows NI operators to focus on safely operating the nuclear heat source

Reactor power independent of turbine output

- Reactor remains at full power while turbine output variations are accommodated via salt tank inventory management

Immediate reactor plant response to changes in EI heat rejection systems are not necessary SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 13

Transient Separation

With operational flexibility, most events on the EI that would affect the NI in a typical nuclear power plant have no immediate impact

EI events can lead to Postulated Initiating Events (PIEs) if resulting change to an interface parameter occurs

Plant design ensures that EI SSCs are not required to perform any defense line functions other than very few selected DL2 sensors on the EI

Transient Separation Defense-in-Depth

Plant safety analyses only model PIEs that directly impact the NI.

Regulatory Separation

Transient separation allows performance of defense line functions by NI SSCs, except for selected DL2 sensing functions, which are NSR

- Regulatory review of EI is significantly reduced

Ability to adapt non-nuclear commercial technologies to the EI

Opportunity to construct EI independently, under a non-nuclear QA program

Physical separation of NI and EI provide opportunity for limited security to EI facilities and SSCs SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 16

Questions?

Acronym List AOO - Anticipated Operating Occurrence LBE - Licensing Basis Event ARCAP - Advanced Reactor Content of Application LMP - Licensing Modernization Project Project NI - Nuclear Island ARDC - Advanced Reactor Design Criteria PDC - Principal Design Criteria ARDP - Advanced Reactor Demonstration Program PIE - Postulated Initiating Event CFR - Code of Federal Regulations PSAR - Preliminary Safety Analysis Report DID - Defense-in-Depth RIPB - Risk-Informed, Performance-Based DL - Defense Line SFR - Sodium Fast Reactor EBR - Experimental Breeder Reactor SSC - Structures, systems, and components EI - Energy Island TICAP - Technology Inclusive Content of Application ESS - Energy Storage System Project FFTF - Fast Flux Test Facility TREAT - Transient Reactor Test GDC - General Design Criteria SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright© 2021 TerraPower, LLC. All Rights Reserved. 18

ML21319A245

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