X-Energy is currently constructing the world’s first commercial scale advanced nuclear reactor in the state of Washington. The new reactor is part of the U.S. Department of Energy’s (DoE’s) two and a half billion-dollar Advanced Reactor Demonstration Program (ARDP). The ARDP is supporting the construction of X-Energy’s first three hundred and twenty megawatt XE-100 power plant which will host four eighty megawatt Pebble Bed Modular Reactors (PBMRs).
The helium-cooled, high-temperature PBMRs are designed to provide small-scale power generation with faster deployment times and improved safety over large conventional reactors. The PBMR consists of a steel pressure vessel with a graphite core. The core is filled with enriched uranium dioxide fuel “pebbles”. Each pebble is about the size of a billiard ball.
The pebbles have a Tristructural Isotropic (Triso) coating that creates an airtight seal around the uranium kernel to retain fission products and gases produced during operations. This allows the plant to be constructed within about sixteen hundred feet of factories or urban areas.
The DoE explains that “The fresh pebbles are loaded in the reactor like a gumball machine, and helium is pumped down through the pebble bed to extract the heat into a steam generator that produces electricity. The reactor continuously refuels by adding fresh pebbles daily in at the top, as older ones are discharged from the bottom of the core. Each pebble remains in the core for a little more than three years and are circulated through the core up to six times to achieve full burnup.”
Through gravity feeding, the pebbles are continuously rotated to generate heat. The heat is used to convert water into steam that turns a turbine to generate electricity.
X-Energy has also signed a contract with the U.S. military to supply it with Xe-mobile micro reactors for use at remote locations.
The earliest types of PBMRs were developed by a team of South Africans as part of Eskom’s PBMR company. The South African utility planned to construct a new nuclear power station in Duynefontein near Koeberg that would use the PBMR technology.
However, after ten years of development and ballooning costs, the project was canceled due to a lack of investment. X-Energy recruited Eben Mulder who is one of the original team members. He now serves as the chief scientist for X-Energy. X-Energy’s lead reactor developer is Martin van Staden who is also from South Africa. He is a graduate of North-Western University and the University of Johannesburg.
Civil rights organization Afriforum is launching its own electricity generation company. They have plans to deploy South Africa’s first PBMR. Kallie Kriel is the CEO of AfriForum. He said that South Africa needs more reliable baseload capacity that fluctuates less than wind and solar. It can be dispatched on demand for peak consumption periods.
Afriforum hopes to attract the necessary investors and expertise for local development. Afriforum claims that nuclear power generation is emission-free. They say that radioactive waste disposal techniques have advanced significantly to ensure minimal environmental impact. In the case of X-Energy’s Triso-X fuel, the pebbles are placed into dry storage casks and stored on-site.