The Pentagon uses TRISO technology to design its mini nuclear reactors

In mid-March 2020, the Pentagon announced that it would entrust 3 American companies with studies for the design of a miniaturized nuclear reactor intended to be projected and, potentially, to supply electrical energy to the remote bases of the American armed forces. The fears of seeing a nuclear reactor set up within an American base, and on foreign soil, have obviously raised objections and questions, in particular concerning the security of the device in the face of an attack. The examples of the catastrophes of Three Miles Island, Chernobyl and Fukushima, naturally raise fears that a scenario of runaway of the reactor which would enter into uncontrolled fusion and end up melting its containment enclosure does occur. All the more so since it is impossible to design a containment enclosure comparable to those of civilian plants if the device had to be projectable.

In an interview given to the American site, Jeff Waksman, the director of Project Pele (named after the Hawaiian Goddess of Fire and Creation), details the architecture of the program, and in particular the use of TRISO technology, intended to prevent this type of disaster. In a synthetic way, TRISO nuclear fuel, for Tristructural-isotropic, consists of balls of 1mm in diameter composed of a uranium oxide core, surrounded by three layers of isotropic coatings including a layer of silicon carbide ceramic, a layer of pyrocarbon and a layer porous carbon. The objective of this composition is to allow each element to withstand very high temperatures without breaking, and therefore without allowing the uranium to spread. According to the data communicated, the TRISO fuel can withstand temperatures of 1.600 ° Celsius, well above the melting temperature of the steel generally used to contain nuclear fuel.

Close-up on a TRISO bead detailing the core (in yellow) and the 3 layers of protection. The ball actually only measures one millimeter in diameter.

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