X-energy

X-energy is a nuclear reactor and fuel design engineering company. X-energy is developing Generation IV high-temperature gas-cooled nuclear reactor designs. In January 2016 X-energy was awarded a five-year $53M United States Department of Energy Advanced Reactor Concept Cooperative Agreement award to advance elements of their reactor development.^[1][2][3] The company was founded in 2009 by Kam Ghaffarian.^[4]

Reactor design

The Xe-100 is a pebble bed high-temperature gas-cooled nuclear reactor design that is planned to be smaller, simpler and safer when compared to conventional nuclear designs. Pebble bed high temperature gas-cooled reactors were first proposed in 1944.

Each reactor is planned to generate 200 MWt and approximately 76 MWe. The standard Xe-100 "four-pack" plant would generate approximately 300 MWe and will fit on 13 acres. All of the components for the Xe-100 are planned to be road-transportable, and be installed, rather than constructed, at the project site to streamline construction. The company objective is to incorporate innovative design features with the goal of building a small-scale nuclear energy source that can be adapted to a variety of markets.

Fuel design

The fuel for the Xe-100 is a spherical fuel element, or pebble, that utilizes the TRISO particle nuclear fuel design. The fuel element begins with a kernel made up of a solid solution of UO₂ and UC, with an enrichment of 15.5% U-235. The TRistructural-ISOtropic (TRISO) coating is deposited onto uranium kernels using a chemical vapor deposition (CVD) process. The TRISO coating consists of four layers continuously deposited; a porous carbon layer referred to as buffer, an inner isotropic, dense pyrocarbon layer (IPyC), a silicon carbide layer (SiC), and an outer isotropic, dense pyrocarbon layer (OPyC). TRISO particles are overcoated with a graphite matrix material and pressed into a solid spherical shape, known as the fuel core. The graphite matrix surrounding the TRISO particles moderates the reaction. A spherical layer of graphite matrix is pressed on the outside of the fuel core. This layer is called the fuel free zone and acts as a barrier to protect the fuel core. The final pebble form is a 60 mm sphere with a homogenous distribution of TRISO particles in a graphite matrix in the center, surrounded by a layer of graphite containing no fuel. Each pebble contains approximately 18,000 TRISO particles. The Xe-100 will require 220,000 pebbles.

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