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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

Decoupling Strategy a TerraPower & GE-Hitachi technology

Objectives

Natrium'reactor licensing overview

Natrium reactor safety and plant overview

Explain Decoupling Strategy within the Natrium design 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 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

- Testing Plan and Methodology 4

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 5

Natrium Safety Features 6

Control Contain Cool

Pool-type Metal Fuel SFR with Molten Salt Energy Island

- Metallic fuel and sodium have high compatibility

- No sodium-water reaction in steam generator

- Large thermal inertia enables simplified response to abnormal events

Simplified Response to Abnormal Events

- Reliable reactor shutdown

- Transition to coolant natural circulation

- Indefinite passive emergency decay heat removal

- Low pressure functional containment

- No reliance on Energy Island for safety functions

No Safety-Related Operator Actions or AC power

Technology Based on U.S. SFR Experience

- EBR-I, EBR-II, FFTF, TREAT

- SFR inherent safety characteristics demonstrated through testing in EBR-II and FFTF Control Motor-driven control rod runback Gravity-driven control rod scram Inherently stable with increased power or temperature Cool In-vessel primary sodium heat transport (limited penetrations)

Intermediate air cooling natural draft flow Reactor air cooling natural draft flow -

always on Contain Low primary and secondary pressure Sodium affinity for radionuclides Multiple radionuclides retention boundaries

Rx Building Fuel Building Fuel Aux. Building Rx Aux. Building NI Power Distribution Center & Controls Control Building Warehouse

& Admin Standby Diesels Firewater Shutdown Cooling Inert Gas Steam Generation Turbine Building TI Power Distribution Center Energy Storage Tanks Demin Water Salt Piping SUBJECT TO DOE COOPERATIVE AGREEMENT NO. DE-NE0009054 Copyright © 2021, TerraPower LLC. All Rights Reserved.

Plant Overview 8

Reactor Aux. Building Intermediate Sodium Hot Leg Intermediate Sodium Cold Leg Reactor and Core Intermediate Air Cooling Head Access Area Refueling Access Area Reactor Air Cooling / Reactor Cavity Reactor Building Fuel Handling Building Reactor Air Cooling Ducts Spent Fuel Pool (water)

Sodium Int. loop Sodium/Salt HXs Salt Piping to/from Thermal Storage System Ground Level

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

- Regulatory separation 10

Decoupling Strategy Molten salt storage tanks eliminate direct coupling of reactor power and turbine output that are inherent in PWR and BWRs 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 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 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

- Enables no safety related DL3 SSCs on the EI 14

Transient Separation 15 Defense-in-Depth

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

All defense line 2, 3, and 4 functions are performed by NI systems

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 16

Questions?

Acronym List AOO - Anticipated Operating Occurrence ARCAP - Advanced Reactor Content of Application Project ARDC - Advanced Reactor Design Criteria ARDP - Advanced Reactor Demonstration Program CFR - Code of Federal Regulations DID - Defense-in-Depth DL - Defense Line EBR - Experimental Breeder Reactor EI - Energy Island ESS - Energy Storage System FFTF - Fast Flux Test Facility GDC - General Design Criteria 18 LBE - Licensing Basis Event LMP - Licensing Modernization Project NI - Nuclear Island PDC - Principal Design Criteria PIE - Postulated Initiating Event PSAR - Preliminary Safety Analysis Report RIPB - Risk-Informed, Performance-Based SFR - Sodium Fast Reactor SSC - Structures, systems, and components TICAP - Technology Inclusive Content of Application Project TREAT - Transient Reactor Test

ML21319A245

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