TerraPower Goes Vertical at Kemmerer

Six days after Kairos broke ground in Oak Ridge, TerraPower broke ground in Wyoming — and the NRC shipped a second new licensing framework while the first was still warming up.

In context: Q1 electricity prices ran roughly 8–9% above last year, AI buildout keeps eating capacity, and the advanced-reactor stack added three more layers of execution in seven days — a sodium-cooled fast reactor going vertical, a microreactor licensing rule, and a working microreactor test bed at INL.

This week at a glance

TerraPower starts construction on Kemmerer Unit 1 — first US utility-scale advanced reactor going vertical

345 MW Natrium with molten-salt storage that lifts output to 500 MW. 1,600 workers mobilizing this spring. Operational target 2030–2031.
NRC proposes Part 57 — a microreactor-only licensing rule with a 6–12 month review target

Targets reactors at roughly 100 MWe and below. Allows fleet approval and limited construction before permit. Federal Register May 6.
INL's DOME test bed opens for privately built microreactors — Westinghouse and Radiant first

World's first dedicated facility for fueling, operating, and decommissioning private microreactor demos inside a DOE containment envelope.
First American Nuclear files engagement plan for EAGL-1 — only US lead-bismuth-cooled SMR design

240 MWe fast reactor. Atmospheric pressure, no intermediate loop. FANCO is also building a lead-bismuth test loop for the NRC.

In depth

Reference

Natrium — TerraPower's sodium-cooled fast reactor with integrated molten-salt heat storage; 345 MW base load, boostable to 500 MW for peak demand

Part 57 — proposed NRC rule for microreactors (commonly ~100 MWe and below; the rule itself uses consequence and fuel-mass thresholds rather than wattage); targets 6–12 month review timelines and allows fleet-of-identical-units approval

DOME — Demonstration of Microreactor Experiments at INL; the first DOE-sited test bed where private developers can fuel, operate, and decommission a reactor inside a federal containment envelope

Lead-bismuth — liquid-metal coolant alloy; runs at atmospheric pressure with no chemical reactivity to air or water, the safety case sodium designs have to engineer around

Construction

TerraPower Goes Vertical at Kemmerer — the Second Advanced Reactor Groundbreaking in a Week

Before: The Natrium project in Wyoming had everything but plant construction itself — NRC permit issued March 4, site prep underway since June 2024, sodium test loops running, but no nuclear-side build.

Now: On April 23 TerraPower formally started construction on the Kemmerer Unit 1 nuclear island — a 345 MW sodium-cooled fast reactor with molten-salt storage that lifts output to 500 MW for peak demand. The company is mobilizing roughly 1,600 workers this spring, with a permanent operations crew of about 250 once it's online. Target operational date is 2030–2031, which would make it the first utility-scale advanced reactor in the US. Comes six days after Kairos broke ground on Hermes 2 in Oak Ridge — two utility-scale Gen IV reactors moving from paper to dirt inside a single news cycle.

→ Sodium loop testing and the first reactor vessel arrival at site — the moments where supply-chain and welding pace become the gating factor instead of permitting

Regulatory

NRC Drops a Second New Licensing Rule a Week After Reorganizing Around the First

Before: Part 53 — the new technology-inclusive framework — became effective April 29, but its scope still maps to traditional reactor scale. Microreactors below 100 MWe were going to ride the same review queue as a 1,200 MW PWR.

Now: On April 24 the NRC proposed Part 57, a microreactor-only framework targeting 6–12 month construction permit and operating license reviews — roughly an order of magnitude faster than today's pace. The rule covers reactors at roughly 100 MWe and below, allows approval of fleets of identical reactors, streamlines environmental review for low-impact projects, and creates a pathway for limited construction ahead of permitting. NRC's own cost-savings estimate is $3.76B to $11.84B across all parties. Federal Register publication is scheduled for May 6, opening the formal comment window. Comes from the not-yet-live Office of Advanced Reactors set to go live midsummer — second visible move tied to Bowen's incoming office in two weeks.

→ Whether the 6–12 month figure survives the comment cycle, and which microreactor developer routes the first Part 57 application — Westinghouse, Radiant, BWXT, and Antares are the obvious candidates

Technology / Construction

DOE's Pilot Program Just Got Its Physical Home — DOME Opens for Private Microreactors

Before: The 11 reactor projects DOE picked under the pilot program had a July 4 criticality target but no shared physical infrastructure — every developer was on its own to find a containment envelope, fueling capability, and decommissioning path.

Now: INL's DOME — Demonstration of Microreactor Experiments — is complete and ready for occupancy, the world's first DOE-sited test bed where private developers can assemble, fuel, operate, and safely decommission a microreactor inside an existing federal containment envelope. DOE conditionally selected Westinghouse and Radiant as the first two tenants. Both designs are also pilot-program candidates for the July 4 criticality target. The long pole on demonstration just got shorter — and the pilot program now has a place where its operational data actually gets generated.

→ First fueled reactor experiment inside DOME — and whether operational data feeds back into the DOE/DOW leveraging pathway (comment deadlines May 4 and May 18, below) fast enough to compress commercial licensing on the back end

Technology

A Lead-Bismuth Reactor Joins the US Pre-Application Queue

Before: The advanced-reactor cast had sodium fast reactors (TerraPower), fluoride-salt designs (Kairos), gas-cooled (X-energy), and small light-water (NuScale, Holtec). Lead-bismuth — the coolant the Soviet Navy ran in Alfa-class subs — had no US commercial entry.

Now: First American Nuclear submitted its EAGL-1 regulatory engagement plan, a 240 MWe lead-bismuth-cooled fast SMR. The design runs at atmospheric pressure, doesn't need an intermediate heat loop, and isn't chemically reactive with air or water — the safety story sodium designs have to engineer around. FANCO is also building a lead-bismuth test loop to feed real performance data to the NRC, rather than relying on models alone. Pairs with the company's Indiana closed-fuel-cycle park announcement from late 2025, which positioned EAGL-1 inside an on-site reprocessing concept.

→ Whether Part 57 or Part 53 routes EAGL-1's eventual application — and whether the closed-fuel-cycle Indiana siting holds up under a real licensing review

Stat of the week

1,600

Workers TerraPower is mobilizing at Kemmerer this spring as nuclear-island construction starts on Unit 1 — roughly six and a half times the permanent operations crew the plant will employ once running.

— TerraPower, April 23, 2026

Global signal

Czech Republic — Rolls-Royce SMR signs Early Works contract for Temelín

ČEZ and Rolls-Royce SMR signed an Early Works Contract on April 24 for site-specific design at Temelín, the Czech Republic's first SMR. The strategic partnership targets up to 3 GW deployed; first unit is expected in the latter half of the 2030s. For US professionals: Rolls-Royce SMR is now the only SMR vendor with multiple firm European contractual commitments — UK, Czech Republic, and continued discussion with Sweden. The European order book matters because it sets the manufacturing volume that decides whether SMR factory economics actually clear. Every Czech, UK, or Swedish unit that ships also drops the cost curve for the eventual US buyer.

Forward look

May 4 Comment deadline on the NRC's DOE/DOW fast-track licensing rule (Docket NRC–2025–1503) — last week to weigh in on the rule that lets demonstration data shave years off commercial license reviews
May 6 Part 57 publishes in the Federal Register — formal comment window opens on the microreactor-only framework Bowen's OAR is shipping out of the gate
May 18 Comment deadline on the Draft Interim Staff Guidance for the DOE/DOW leveraging pathway — the operational how-to that will determine whether the rule actually moves reviews faster
Jul 4 DOE Reactor Pilot Program criticality target — 3 of 11 selected projects aim for first criticality, and DOME is now where at least two of them will run

Companion tool: fuel.jrand.net — live UF₆ conversion capacity, by facility.

Until next Thursday,

— Jace Arnold

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