Two-Phase Composite Moderators for Compact High-Temperature Nuclear Reactors

Background

A large majority of the commercial fission power reactors used around the world are known as Thermal‑neutron Reactors. These reactors involve the absorption of a thermal (low energy) neutron to trigger the fission process of Uranium‑235 and Plutonium‑239. The thermal neutron starts off having very high energy as it emanates directly from the fission reaction, and then steadily downgrades in energy as it collides with other particles in the reactor. Current power reactors are light‑water reactors in which the thermal neutrons collide with the Hydrogen atom in the water molecules. The most effective moderating materials that the thermal neutron can collide with are low atomic numbered constituent atoms such as H, Be, Li, C, O, Mg, Al, Si, etc. The current need for nuclear power research is revolved around reducing the physical size of the thermal reactors and the overall power output so that small modular reactors can be developed. A new technology is needed that can allow small modular reactors to be efficient and compact while using advanced moderating materials.

Technology

This technology revolves around an advanced composite moderator, which is a two‑phase mixture of a highly moderating phase that is entrained within a matrix phase. Both phases have superior neutronic moderation when compared to graphite, have adequate neutron absorption, and also have good long‑term operating stability. There are multiple examples of advanced moderators that involve different moderating materials but are all effective. Using two‑phase moderators has the potential to produce more power in a graphite‑moderated fission reactor core of a specific size and/or enable the reactor design to design more compact systems. The advanced moderator allows for smaller, cheaper, and safer reactors to provide reliable energy.

Advantages

Allows for a more compact reactor, where the overall physical size of the reactor is lowered and allows more control over the power output. - It is cheaper than conventional processes. - It is safer than conventional processes. - It also has good long‑term operating stability.

Application

This technology will be applied to thermal neutron nuclear reactors. It will allow for reactor designs to be more compact, safer, cheaper, and reliable.