| NEWS Antares criticality test


The Antares R1 Mark-0 is a full-scale, zero-power demonstration microreactor. Source: Antares


As part of the US Department of Energy (DOE) Reactor Pilot Program, Antares Nuclear’s Mark- 0 reactor design has completed a zero-power fuelled criticality demonstration at the DOE’s Idaho National Laboratory (INL). The demonstration was conducted in partnership with DOE, INL, and BWX Technologies (BWXT), with integration and observation support from the US Army. The Mark-0 is the first of several advanced


reactors racing to go critical by the 4 July deadline set by President Trump in his May 2025 Executive Order (EO) 14301. The EO mandated that the US Secretary of Energy approve a streamlined pathway to achieve criticality for at least three advanced test reactors by the US 250th Independence Day. The Antares R1 Mark-0 is a full-scale, zero- power demonstration reactor built to validate the physics and core performance of the company’s planned commercial R1 design. It is a high-temperature sodium heat-pipe reactor, utilising passive liquid metal heat pipes instead of high-pressure liquid pumps. The core uses graphite and boron carbide control drums turned by independent motors, a configuration heavily inspired by historical space reactor designs. The Mark-0 runs on high-assay low-enriched


uranium (HALEU), enriched to just under 20% U-235. It employs a tri-structural isotropic (TRISO) fuel


packed into a structural prismatic graphite core, which inherently prevents meltdown scenarios. The fuel was manufactured at BWXT’s speciality facility in Lynchburg, Virginia. The project transitioned from a design concept to a critical reactor in less than 12 months by using the fast-tracked regulatory and testing pathway. Since the Mark-0 was built strictly as a physics


validation platform, it has no power conversion loop or heat-sink systems installed. Achieving initial criticality means the reactor sustained a controlled, self-supporting nuclear chain reaction. As a zero-power test, it operated at essentially no measurable energy output. The operational data verified by the Mark-0 will


directly anchor the upcoming commercial Mark-1 microreactor, designed to scale output fluidly between 100kWe and 1MWe. It integrates a simple, recuperated nitrogen (N₂) closed ow pressure Brayton cycle to ensure high reliability with virtually zero corrosion risk. It is optimised to run uninterrupted on a single fuel core for four to six years without the need for on-site refuelling. Antares has already initiated design work on


the Mark-1 prototype. The company remains on an aggressive development track, aiming for electricity production by 2027 and initial power delivery to US military installations by late September 2028. ■


First for Uzbek SMR


First concrete has been poured for the first low- capacity nuclear unit of an integrated nuclear power plant (NPP) project in the Farish district of Uzbekistan’s Jizzakh region. In March 2026, a roadmap for nuclear


cooperation was signed by Rosatom and Uzatom, as well as an additional contract agreement for NPP construction. At the same time, preparatory concrete work for the construction of a low-power NPP (ASMM – Atomnoi Stantsii Maloi Moshnosti) with a RITM-200N reactor began at the NPP site. The additional agreement expanded scope of the contract signed in May 2024 for two 55MWe ASMMs to also include two VVER-1000 reactors on the same site. When the NPP is fully operational, it will generate 17.2TWh a year, providing up to 14% of Uzbekistan’s total energy needs.


Formally launching the start of construction,


specialists will pour 133 cubic metres of concrete. The total volume of concrete for the foundation will be 10,000 cubic metres. Prior to the launch, the Committee on Industrial, Radiation & Nuclear Safety under the Uzbek Cabinet of Ministers issued a licence to the state enterprise Directorate for Nuclear Power Plant Construction to build a nuclear unit with a Russian RITM-200N reactor. According to the Times of Central Asia, financing is now one of the key questions. Uzatom director Azim Akhmedkhadjaev put the project’s base price at $9.5bn and described that as the maximum contract amount. The estimate does not include planned localisation, which Uzbekistan wants to increase to 30%. Tashkent reportedly wants loans to cover 85%-90% of the project. ■


round up


NEW BUILD IRAN IS MOVING FORWARD with plans to build nuclear power plants (NPPs) at five locations along its coastline to increase the share of nuclear energy in the electricity mix. Mohammad Eslami, head of the Atomic Energy Organisation of Iran, said the projects are being implemented under the country’s comprehensive strategic document for the nuclear industry, unveiled in 2022.


A HIGH-LEVEL MEETING at Russia’s Beloyarsk NPP was held to assess plans for construction of the BN-1200M sodium-cooled fast reactor as unit five at the site. Preparatory work began in 2025 and the site has already been cleared of more than 1.4 million cubic metres of soil, as well as vegetation and tree stumps. Design documentation is being developed and, by the end of the summer, the site will be prepared for drilling and blasting operations.


THE BOTTOM PLATE, the last element of the melt localisation device (melt trap) has been installed in the reactor building of Leningrad NPP unit seven (also known as Leningrad-II unit three). The equipment, weighing 120 tonnes, was installed in a concrete reactor shaft supported on a console truss. General contractor Titan-2 specialists completed the complex operation in one work shift.


THE FIRST CONCRETE mixing unit is ready to start pouring concrete into the foundation of the reactor building for unit one of Russia’s Smolensk-II NPP, scheduled for March 2027, according to Smolensk BPP director Ivan Sidorov. Smolensk-II is being built 6km from the existing Smolensk NPP, which comprises three RBMK reactors nearing the end of their design life.


THE SIXTH TIER OF THE internal containment has been installed at unit two of the Akkuyu NPP under construction in Türkiye. Installation took around four hours. The builders used a heavy crawler crane and a special traverse with a hydraulic adjustment system, which ensured precise positioning of the structure during lifting and installation.


HOT FUNCTIONAL TESTS have been completed at unit three of China’s Xudabao NPP in Liaoning province in preparation for the launch of the VVER-1200 reactor, while the CAP-1000 reactor vessel has been installed at unit two. China National Nuclear Corporation (CNNC) said completion of the hot tests at Xudabao unit three laid a solid foundation for the subsequent loading of nuclear fuel, grid connection and power generation.


www.neimagazine.com | July 2026 | 7


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