---
type: source
title: "TerraPower breaks ground on Natrium reactor at Kemmerer, Wyoming — first US utility-scale advanced nuclear plant under construction"
author: "Multiple (kotatv.com, powermag.com, terrapower.com, nucnet.org)"
url: https://www.kotatv.com/2026/04/23/terrapower-breaks-ground-natrium-nuclear-plant-wyoming-first-us/
date: 2026-04-23
domain: energy
secondary_domains: [manufacturing]
format: news
status: null-result
priority: high
tags: [nuclear, Natrium, TerraPower, NRC, advanced-reactor, Kemmerer, Wyoming, SMR, molten-salt-storage]
extraction_model: "anthropic/claude-sonnet-4.5"
---

## Content

TerraPower officially broke ground on April 23, 2026 on the Natrium nuclear plant at Kemmerer, Wyoming — the first utility-scale advanced nuclear power plant to begin construction in the United States. This followed the NRC's issuance of a construction permit on March 4, 2026, the first ever issued for a commercial-scale advanced nuclear plant.

**NRC Permit (March 4, 2026):** NRC Commissioners voted to award the construction permit for Kemmerer Power Station Unit 1. The NRC completed its safety review in December 2025, ahead of schedule and 11% under budget. This is the first commercial-scale advanced nuclear plant to ever receive this permit.

**Ground Breaking (April 23, 2026):** Construction officially began. Bechtel is the engineering, procurement, and construction (EPC) contractor.

**Technology:** 345 MW electric sodium-cooled fast reactor coupled to a 1 GWh molten salt energy storage system. The reactor runs at constant 345 MW while the plant can supply up to 500 MW for 5.5 hours using stored heat. The molten salt storage architecture is borrowed from concentrated solar power (CSP) industry practice — the same technology used in solar thermal plants, adapted for nuclear heat input instead of a solar receiver tower.

**Design history:** TerraPower was founded 2006. DOE ARDP funding selection: 2020, providing up to $2B through 50/50 cost-sharing. The design predates the AI demand wave by 2-3 years. Load-following capability was designed to complement intermittent renewables (solar/wind), not specifically for AI training cycles.

**Timeline:** First power target: 2030. Total cost: ~$4B (DOE + TerraPower cost share).

**Related AI demand context:** The plant's 345 MW → 500 MW surge capability makes it uniquely compatible with AI training cycle variability. Meta signed an agreement for 8 Natrium units (January 9, 2026); NextEra-TerraPower signed for 2.5-3 GW for Google/Microsoft AI data centers (April 8, 2026). But these commercial applications are retrofitted onto an existing design, not the original design intent.

## Agent Notes

**Why this matters:** The NRC construction permit and groundbreaking are the first real proof that the nuclear renaissance has cleared regulatory gates. This is no longer speculative — Natrium is under construction. First power by 2030 means this is a 4-year construction timeline, which will establish the baseline for subsequent unit costs (the critical unknown in advanced reactor economics).

**What surprised me:** The molten salt storage was explicitly borrowed from CSP (concentrated solar power) — the nuclear and solar industries are converging on the same thermal storage technology. This is not how nuclear and solar are usually framed (as competitors). The convergence is structural, not coincidental. Also surprised that groundbreaking happened on the same date as this research session (April 23, 2026).

**What I expected but didn't find:** An explicit AI-native design motivation. The Natrium technical documentation makes clear the design is for renewable grid integration, not AI. The AI commercial fit is real but retroactive.

**KB connections:**
- [[AI datacenter demand is catalyzing a nuclear renaissance]] — Natrium groundbreaking is the most concrete evidence yet; but the mechanism is "pre-existing advanced reactor found new market" not "AI demand catalyzed new reactor design"
- [[the gap between scientific breakeven and engineering breakeven is the central deception in fusion hype]] — same category issue applies here: the gap between NRC permit and first commercial power is the real test
- Energy threshold model: Natrium at $4B / 345 MW = ~$11.6B/GW. Is this below the threshold for data center economics?

**Extraction hints:**
- KB should have a claim specifically on the Natrium NRC construction permit as a regulatory milestone for advanced reactors
- The CSP-heritage-to-nuclear thermal storage convergence is a claim candidate about solar-nuclear technology transfer
- The 2030 timeline for first advanced reactor power is a KB reference point for the nuclear renaissance timeline

## Curator Notes (structured handoff for extractor)

PRIMARY CONNECTION: The nuclear renaissance belief (Belief 12) and the energy threshold model (Belief 8)
WHY ARCHIVED: First construction-stage evidence for the advanced reactor mechanism. Groundbreaking and NRC permit are the most concrete signals that the nuclear renaissance has crossed from announcement to physical commitment.
EXTRACTION HINT: Focus on (1) what the NRC permit means for subsequent advanced reactor licensing, (2) the CSP heritage of molten salt storage as a structural convergence finding, (3) 2030 first power as a timeline peg for KB reference
