Kairos Breaks Ground on First Gen IV

This past week, the first Gen IV power-producing reactor broke ground in Oak Ridge, the NRC restructured itself around advanced reactors, and Japan's biggest plant came back online.

In context: This week, shovels went in the ground at Oak Ridge, the NRC stood up a dedicated advanced-reactors office, Constellation pulled 158 MW out of Byron without a new permit, and X-energy filed to go public on a $4B-plus order book. Four separate signals, one direction — the industry is moving from paperwork to execution.

This week at a glance

Kairos breaks ground on Hermes 2 in Oak Ridge — first Gen IV power-producing reactor to break ground under an NRC construction permit

50 MW to the TVA grid under a Google offtake for Tennessee and Alabama data centers. Reactor modules built in Albuquerque.
NRC announces Office of Advanced Reactors — three-line restructure takes effect midsummer

Jeremy Bowen leads OAR. CNRI absorbs the four regional inspection offices. Biggest structural change at NRC in decades.
Constellation finishes Byron Unit 1 uprate — 158 MW coming online across Byron and Braidwood, no new permits

$800M program, turbines swapped during routine refueling outage. Full program completes in 2028.
Japan returns Kashiwazaki-Kariwa Unit 6 to commercial operation — first eastern-Japan restart since 2011

TEPCO's 1,356 MW ABWR. Japan now has 15 of 33 operable reactors running.

In depth

Reference

KP-FHR — Kairos Power fluoride-salt-cooled high-temperature reactor; uses TRISO fuel in FLiBe coolant; the first Gen IV design to break ground under an NRC construction permit

OAR — Office of Advanced Reactors; new NRC office consolidating licensing of SMRs and Gen IV designs under one roof, led by Jeremy Bowen

UPRISE — DOE's Utility Power Reactor Incremental Scaling Effort; launched March 2026, targeting 2.5 GW by 2027 and 5 GW by 2029 from the existing fleet

ABWR — Advanced Boiling Water Reactor; the GE-Hitachi design at Kashiwazaki-Kariwa Units 6 and 7 and the lineage feeding the modern BWRX-300 SMR

Construction / Technology

Kairos Breaks Ground on the First Gen IV Reactor Ever Permitted for Power

Before: Gen IV designs had regulatory wins on paper — Part 53 final, TerraPower's March construction permit for Natrium — but no commercial-scale build was actually underway.

Now: Kairos Power broke ground on Hermes 2 in Oak Ridge on April 17 — the first Gen IV power-producing reactor to move from NRC construction permit to physical build. 50 MW KP-FHR, fluoride-salt-cooled with TRISO fuel, sending power to the TVA grid under Kairos's offtake agreement with Google for Tennessee and Alabama data centers. Reactor modules are fabricated at Kairos's Manufacturing Development Campus in Albuquerque and shipped to Oak Ridge for assembly. Barnard Construction is general contractor. Sits on the same campus as Hermes 1, the low-power demonstration reactor already under construction.

→ First module shipment from Albuquerque to Oak Ridge — the moment factory-build cadence becomes visible and SMR economics get tested

Regulatory

NRC Restructures — and Advanced Reactors Finally Get Their Own Office

Before: NRC's org chart predated the current SMR and Gen IV wave. Advanced reactor applications ran through the same queue that handled operating-fleet inspections.

Now: On April 21 the NRC announced a reorganization plan around three business lines — new reactors, operating reactors, and nuclear materials and waste. Two new offices stand up inside it: the Office of Advanced Reactors, led by longtime NRC staffer Jeremy Bowen, and the Office of the Chief Nuclear Reactor Inspector, which absorbs the four regional inspection offices. Executive Director for Operations Mike King framed the goal as faster, more predictable licensing while maintaining safety. Implementation targets midsummer 2026 — which lines up with the first Part 53 applications hitting the queue.

→ Whether OAR has the staffing and authority to actually move reviews faster, or becomes a relabeled version of the same queue — the first Part 53 application routed through it will tell

Construction / Market

Byron Adds 158 MW the Same Week Kairos Breaks Ground. No Permits Required.

Before: Nuclear's capacity story gets told in new builds — and new builds still take 15 years and $17B+ per unit (Vogtle). The existing fleet's uprate potential gets less attention than it deserves.

Now: Constellation completed Phase 1 of its $800M Byron/Braidwood uprate during the spring refueling outage, swapping new low-pressure turbines into Byron Unit 1. The combined program now targets 158 MW of added capacity across both stations — roughly 100,000 homes — by 2028. Sits under DOE's UPRISE initiative, which launched March 12 and targets 2.5 GW of added capacity from the existing fleet by 2027 and 5 GW by 2029. Per NEI, 73% of US sites are carrying some level of active uprate interest.

→ Byron Unit 2's low-pressure turbine swap in the fall 2026 outage — the second visible chunk of capacity added with zero new-reactor review time

Market

X-energy Files to IPO — First Pure-Play Advanced Reactor Vendor with a Real Order Book

Before: Advanced reactor vendors were private. Order books were speculative — LOIs, MOUs, no offtake commitments at construction scale.

Now: X-energy filed an $814M IPO on April 16 at $16 to $19 per share. Amazon is anchor: $500M in a prior round, and up to 5 GW of Xe-100 offtake committed by 2039. Xe-100 sits in DOE's advanced-reactor pilot pipeline, and TRISO-X — X-energy's fuel subsidiary — holds one of the agency's fuel-fabrication pilot picks.

→ Pricing range, first-day float, and whether public markets benchmark advanced reactors on MW contracted rather than reactor count

Stat of the week

5 GW

DOE's 2029 target for added nuclear capacity from the existing fleet alone — roughly four AP1000s worth of generation, requiring zero new-reactor construction permits. 73% of US sites are already carrying active uprate interest.

— DOE UPRISE initiative / NEI, 2026

Global signal

Japan — Kashiwazaki-Kariwa Unit 6 enters commercial operation

TEPCO declared commercial operation for Kashiwazaki-Kariwa Unit 6 on April 16 — a 1,356 MW ABWR offline since Fukushima, and the first post-2011 commercial restart in eastern Japan. It brings Japan's operating fleet to 15 reactors out of 33 operable. For US professionals: Kashiwazaki-Kariwa is the world's largest plant by nameplate capacity — 8.2 GW across seven units — and the restart pace over there is the benchmark for what a mature regulatory environment can actually deliver once political will clears. That's the comparison worth watching as OAR stands up here.

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 pathway that lets demonstration data shave years off commercial license reviews
May 18 Comment deadline on the Draft Interim Staff Guidance for the same DOE/DOW leveraging pathway — the operational how-to that will actually determine whether the rule moves reviews faster
Jul 4 DOE Reactor Pilot Program criticality target — 3 of 11 selected projects aim for first criticality; the first operational data feeds the NRC leveraging pathway
Midsummer NRC Office of Advanced Reactors and Office of the Chief Nuclear Reactor Inspector go live — the first Part 53 applications will route through OAR from day one

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

Until next Thursday,

— Jace Arnold

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