X-Energy submits SMR permit to build in Texas

Still Chasing Mirages

Reuters news reports on March 31, 2025 that the privately owned X-Energy nuclear startup company has submitted an application for a construction permit to the US Nuclear Regulatory Commission (NRC) for a proposed “first-of-its-kind” High Temperature Gas (helium) cooled Reactor (HTGR) nuclear power project in Texas. The Xe-100 Small Modular Reactor (SMR) would provide electricity and thermal heat (i.e. steam) for manufacturing purposes to Dow Inc.’s Seadrift Operations facility. Dow’s massive Seadrift site currently manufactures food packaging material, shoes and wire currently powered by natural gas. Key aspects of the application made to the NRC by X-energy and Dow focus on its purported safety profile of the Xe-100 advanced SMR with fuel design, passive safety features and analysis. Dow’s proposed Generation IV advanced SMR project is being developed by its wholly-owned subsidiary, Long Mott Energy.

Once fully approved by NRC according to sources, the construction and installation of the SMR could take several years, perhaps even a decade. The construction permitting itself could take up to 30 months, according to reports that Beyond Nuclear has reviewed. Commercial operation of the Xe-100 SMR in Texas is being projected for to the early 2030s.

As of April 3, 2025, X-Energy’s Xe-100 design, is still in the pre-application stage working its way through the NRC’s design approval process for reactor safety certification. The NRC is presently determining if the new application contains critical information that would need to be withheld from public review and redacted from the application as “Sensitive Unclassified Non-Safeguards Information (SUNSI).

X-energy’s plan is for four modular Xe-100 High Temperature Gas (helium) cooled Reactors (HTGR) capable of providing 80 megawatts of electricity or 200 megawatts of thermal power, totaling to 320 megawatts electric or 800 megawatts thermal. The individual units would be operated from a common control room.While the HTGR design is significantly different from the commercial “light water reactor” (LWR) that constitutes the entire US operational nuclear fleet, it’s not a completely new design either as design or operationally. It could be described as an innovated “blueprint” going back to the 1940s and prototype development through the 1950s and 1960s. One such HTGR prototype produced electricity at the Peach Bottom Unit 1 reactor (40 MWe) operated in Delta, Pennsylvania from 1966 to 1974. It was then deemed economically inviable and permanently shut down.

The Fort St. Vrain nuclear power station was an early commercial model HTGR (330 MWe) that operated in Colorado from 1979 to 1989 before it too was permanently closed due to recurring operational problems involving pressure fitted seal failures along the helium coolant lines that allowed the ingression of moisture and mix with the helium significantly reducing the reactor’s core cooling efficiency. More problems developed enlarging higher operational costs. This included control rod failure and the discovery of a cracked main steam header pipe. In total, the utility made a decision to permanently shut down the power facility because it was not financially viable and materially coming apart.

The Xe-100 HTGR significantly differs from these earlier HTGR starting with the development of its TRISO fuel pebbles. The TRISO fuel pebbles are multi-layered, ceramic coated, nuclear-grade graphite moderated spheres, each the size of a billiard ball impregnated with small kernels of “high-assay low-enriched uranium” (HALEU). Conventional light water reactor fuel rods rely on low enriched uranium (3% to 5% uranium-235) to sustain the fission reaction. HALEU fuel is much higher and closer to nuclear weapons grade. The US Department of Energy’s Oak Ridge National Laboratory has partnered with X-Energy to develop HALEU fuel for the Xe-100 that would commercially enrich uranium-235 to nearly 20%. HALEU fuel is still experimental in the United States and presently not commercially produced in the United States. Russia remains the worldwide state-owned oligarchy and source for HALEU. However, the commercial sale of HALEU is politically encumbered and energy security vulnerable by free floating mutual sanctions, on-again off-again embargoes and exemption reviews between the US and Russia. This trade war was the result of the  hot war with Russia’s controversial invasion and sustained war in Ukraine.

Each Xe-100 HTGR is designed to sustain a nuclear reaction by “online refueling” with 220, 000 nuclear fuel “pebbles” the size of a billiard ball. The pebbles feed into and drop through the reactor vessel and overtime recirculated. Imagine a very sophisticated gumball machine that can recirculate the nuclear fuel balls and allow them reach criticality to heat up helium gas to an outlet flow temperature of 750°C (1382°F) and an outflow temperature of super-heated steam at 565°C (1059°F) .  This energy is transferred to steam generators to spin a turbogenerator for electricity.

Each of these multi-layered ceramic-coated, highly radioactive, incredibly hot fuel pebble is individually credited to be an independent “containment” structure. This has been redefined as a “confinement” approach and significantly different from the conventional large steel and concrete “containment” structures  for  protection against highly explosive pressures and widespread, long term, deleterious radiation contamination potential within the nuclear power station. That means that in the Xe-100 HTGR unit, each fuel pebble is rated as a “functional containment,” and by design, cycle in and out of the reactor core for three years, circulating through the core up to six times before achieving full fuel burnup. Each fuel pebble is then transferred to an onsite high-level radioactive waste storage tank. The spent fuel spheres are then periodically replaced with fresh fuel to start the cycle over again. There is currently no scientific or societal to volunteer as a “national sacrifice area” for an indefinite series of deep geological burial sites for the long term management of irradiated nuclear fuel now rods and the added volume and curie count from mountains of deadly billiard balls.

A MAJOR SHIFT IN CONVENTIONAL DEFENSE-IN-DEPTH STRATEGY FOR NUCLEAR POWER

Beyond Nuclear notes that the NRC considers the most basic and fundamental safety function for any nuclear reactor, old, new, and in between, remains to “limit” the release of radioactive materials through a “defense-in-depth” concept that is suppose to reliably prevents and “reasonably assures” the prevention of accidental releases of radioactive material into the environment. For the LWR, this is performed by erecting pressure fitted barriers within barriers;  fuel cladding, the reactor coolant system pressure boundary and finally the ultimate barrier, a large steel and concrete containment system.

The NRC and the nuclear industry have traditionally defined “containment systems” as “leak-tight” structures. In reality, even during “normal” operations, there is some amount of radiation that routinely “leaks out” even “discharged” into the environment (both to the air and water) during routine operations. Then there are  malfunctions, aging and failing material barrier systems and eventually loss of margins in risk and consequences to safety following severe accidents. In conventional light water reactors that  first depends on  the costly maintenance of nuclear-grade material quality and assurance. Working against that, like rust never sleeps, there is also the uncertainty of the rate of degradation. This effects  all of the various barriers starting whether fuel rod or a fuel ball , the cladding degrades under a nuclear power’s harsh operating environment over time.

Non-LWR technologies, such as the Xe-100, are still developing their knowledge about operating conditions, coolants, and fuel forms that significantly differ from LWRs. This has led to description of a “functional containment” or “confinement” now being expanded to a credited “containment system” as  a set of barriers taken together, that are supposed to more effectively limit if not prevent the escape of radioactive material to the environment.  For example, the NRC  identifies that if the Xe-100 design is able to retain the highly radioactive materials by using multiple ceramic barriers for each fuel pebble, the building enclosing the reactor vessel may not need to be part of the functional containment for some or all accident event categories.

Beyond Nuclear notes that there has already been at least one significant radiological accident involving another HTGR prototype in Hamm-Uentrop, Germany. The experimental THTR-300 served as a prototype high-temperature helium cooled reactor using TRISO pebble fuel produced by the German company AVR, an experimental pebble bed operated by VEW (Vereinigte Elektrizitätswerke Westfalen). The THTR-300 Pebble Bed Modular Reactor (PBMR) was similar in design to the Fort St. Vrain HTGR in the United States. On May 4, 1986, the German reactor experienced an equipment failure due to human error in the control room. Mistakes were made with the manual override of the nuclear fuel loading mechanism. The human error  resulted in the nuclear fuel feed system jamming of the mechanism. An undisclosed  number of highly radioactive fuel balls were crushed and damage to the protective ceramic coatings  credited for radiation containment. The loss of the credited radiation confinement structure that encased the fuel pebble cores was a breach of some number of containments. Given the design not have a rated over the many reactor cores rolling through, the  accidentally radioactive aerosol release went straight up the chimney to the atmosphere and downwind.

Offsite, the THTR radioactive release to the atmosphere went unnoticed due to the overlap with the radioactive fallout passing over Germany from the Chernobyl disaster in Ukraine that occurred on April 26, 1986 and spread over Belarus, southern Russa, Europe, the British Isles, Scandinavia, Turkey  and beyond. However, an anonymous informant in the nuclear station’s workforce was among the first to report the accidental release. The worker further alleged there was a deliberate attempt to conceal the radioactive emissions from authorities and an already spooked public. The reactor operators further tried to conceal the radioactive release from regulatory authorities. Instead of declaring the THTR radiological emergency, the control room  attributed the radiation increase to the Chernobyl fallout. However, a subsequent report from scientists at the University of Freiburg also identified that the radioactive release signature from environmental monitoring stations also identified unusual levels of radioactive Protactinium-233 (²³³Pa) isotopes, inconsistent with fallout from the Chernobyl RBMK but a match for the THTR.

The reactor was ordered to immediately shutdown for an investigation. The power company’s deliberate effort to cover-up the THTR radioactive releases in the Chernobyl fallout destroyed the regulatory and public trust in the power company and further undermined the public trust and reliability in all of Germany’s nuclear power plants.

On September 1, 1989, the THTR facility was permanently shut down. The facility’s operational life spanned from 1985 to 1989, with only 423 full-load operating day equivalents. There was a total number of 80 incidents logged in over that same period.

NON-LIGHT WATER REACTOR RELIANCE ON HALEU REACTOR FUEL RAISES PROLIFERATION RISKS

The increased proliferation of the spread of nuclear weapons grade materials evolving out of  the development and global trafficking of HALEU fuel is now recognized even in small quantities of the higher enriched uranium (now up to 20% uranium-235). The spent fuel from the advanced reactors like the Xe-100 reactor would also contain fissile materials that can be used in the development of nuclear weapons.

Dr. Edwin Lyman, Union of Concerned Scientists, addressed the  reactor safety and proliferations risks  coming out of the Biden Administration and the United States participation in the COP 29 climate talks in Baku, Azerbaijan.

“The [COP29 climate talks] framework also endorses the development of new reactors that require large quantities of high-assay low-enriched uranium (HALEU), and the supply chain needed to produce and process HALEU, without acknowledging the increased nuclear proliferation and security risks posed by this material, which is likely directly usable in nuclear weapons.

“Without seriously addressing these and other safety and security risks, the framework’s promise to ‘safely and responsibly’ expand U.S. nuclear energy is nothing but false advertising.”