# TerraPower Natrium

**Type:** Advanced nuclear reactor design (sodium-cooled fast reactor with molten salt thermal storage)
**Founded:** TerraPower founded 2006; Natrium concept formalized 2019-2020
**Status:** Under construction (Kemmerer, Wyoming demonstration plant)
**Key Innovation:** Decoupling reactor power production from grid power demand via molten salt thermal energy storage

## Overview

TerraPower's Natrium reactor is a 345 MW sodium-cooled fast reactor paired with a molten salt thermal energy storage system that enables variable grid output from 100 MW to 500 MW without adjusting reactor power. The design explicitly borrows equipment and operational practices from the concentrated solar power (CSP) industry.

## Technical Architecture

- **Reactor:** 345 MW thermal, constant operation
- **Primary loop:** Liquid sodium heat transfer
- **Secondary loop:** Non-radioactive molten salt (thermal storage)
- **Grid output range:** 100 MW to 500 MW
- **Surge duration:** 5.5 hours at 500 MW peak
- **Storage technology:** Inherited from CSP industry solar thermal facilities

## Design Intent

The molten salt storage system was designed for renewable grid integration — to complement intermittent solar and wind generation by providing dispatchable firm power. The reactor runs at constant full power (optimal for sodium-cooled fast reactors) while the storage system buffers grid demand variability.

The AI datacenter commercial fit emerged retroactively (2022-2024) when AI operators discovered that the same thermal storage physics that buffers solar intermittency also accommodates AI training cycle surges.

## Timeline

- **2006** — TerraPower founded
- **2019-2020** — Natrium concept formalized
- **October 2020** — Selected for DOE Advanced Reactor Demonstration Program (ARDP); $80M initial funding, $2B authorized through 50/50 cost-sharing
- **2024** — NextEra partnership announced for AI datacenter deployment
- **2026** — Kemmerer, Wyoming demonstration plant under construction

## Commercial Partnerships

- NextEra Energy (AI datacenter deployment partnership)
- Meta, Google, Microsoft (AI datacenter power purchase interest)

## Sources

- TerraPower documentation: https://www.terrapower.com/exploring-the-natrium-energy-storage-system/
- DOE ARDP selection announcement, October 2020
- NRC filings and technical documentation