Every small modular reactor program in the country is betting on factory fabrication. Almost none of them have said out loud what has to change in the concrete codes before that bet pays. Oak Ridge just did.
Kairos Power announced NuCAMP, the Nuclear Center for Advanced Manufacturing and Precast, on Aug. 18 at its Advanced Reactor Demonstration Campus in Oak Ridge, Tennessee. The technical detail landed a week later, in statements NuCAMP participants gave ENR on Aug. 26.
Composite molds, printed in two weeks
ORNL and its partners replaced conventional steel molds for Kairos’ bioshield structures with reusable large-format 3D-printed composite molds. Designed, printed and delivered in about two weeks, against six to eight for steel. They held 1/16-in. tolerances on critical surfaces and survived four bioshield-column pours and three shielding-panel pours with no measurable quality loss, according to Ryan Dehoff, ORNL’s manufacturing science division director.
Bioshields are the geometry problem that makes reactor concrete expensive. They’re thick, heavily reinforced, full of penetrations, and every one is slightly different. Steel formwork for that shape is a long-lead custom fabrication, and if the design moves, the mold is scrap. ORNL composites innovation group leader Ahmed Hassen put the stakes plainly: “Construction has been a major bottleneck for advanced reactors.” The lab estimates radiation-shielding concrete can drive up to 60% of a nuclear project’s schedule risk.
The code is the actual obstacle
The MOU covers precast for safety-related nuclear structures, large-format additive manufacturing of casting forms, wire-arc additive manufacturing of large metal components, and electron-beam welding. Partners include ORNL, the University of Tennessee-Knoxville, the Institute for Advanced Composites Manufacturing Innovation, Barnard Construction, Roane State and Chattanooga State community colleges, and Oak Ridge Schools, with Samsung C&T and Cambridge Vacuum Engineering advising. The first phase runs 12 months.
Here’s the part that decides whether any of it matters. Participants told ENR that ASME Section III, Division 2 and ACI 349 assume monolithic cast-in-place structures. Neither contains explicit provisions for modular precast joints or 3D-printed concrete. So a precast assembly has to be demonstrated to perform like a monolithic one before it can carry safety-related scope, and that demonstration doesn’t exist yet. Participants say the qualification pathways are being written to be usable by other developers, not just Kairos.
Rehearsing on a non-nuclear unit first
Kairos built a full-scale test pier and installed 70 piers on a nonnuclear engineering test unit before Barnard drove Hermes 1’s 51 safety-related 6-ft-dia drilled piers about 40 ft to bedrock, hitting up to six piers a day. Barnard, which is GC on both Hermes 1 and Hermes 2, told ENR it sees an opening to move concrete work into a factory and turn the reactor site into an assembly operation.
That’s the same logic driving panelised construction on the commercial side, where Boston’s Bunker Hill Housing redevelopment is putting up a 266-unit mass timber building on prefabricated interior and exterior wall panels against an 18-month schedule. The difference is that nobody has to prove a residential wall panel performs like monolithic concrete first.
Kairos CTO Ed Blandford: “Delivering affordable advanced reactors at scale will require more than a strong design.” Kairos broke ground on Hermes 2 on April 17 and fabricates reactor equipment modules at its Albuquerque campus for shipment to Oak Ridge. The mold comparison, the tolerance figure and the reuse count are all ORNL’s numbers, and the pier rate is Kairos’. If the code pathway opens, the constraint on nuclear buildout stops being field craft availability and becomes shop capacity, which is a different capital plan for every heavy-civil contractor chasing this work.