Neutron Shielding
“Spent nuclear fuels are cooled to a radioactivity level that makes the fuels suitable for transportation, and then placed in a cask as a nuclear shielding container and transported. Even at this stage, the spent nuclear fuels still emit radiation such as neutrons. Thus the casks must be fail-safe neutron absorbers. Neutrons are known to be absorbed by boron. To make boron absorb neutrons, it is necessary to slow down the neutrons. Hydrogen is known to be most suitable as a substance for slowing down neutrons. Accordingly, a neutron shielding material composition must contain a large amount of boron and hydrogen atoms. A nuclear shielding material for use preferably endures under such high-temperature conditions for about 60 years as a reference storage period for spent nuclear fuels.”
(Hayashi, US Patent 7,811,475, 10/12/2010)
Recent US Patents
10/12/2010
7,811,475
Neutron shielding material composition, shielding material and container
Hayashi of Mitsubishi Heavy Industries, Japan have developed an epoxy neutron shielding material with improved heat resistance and ensured neutron shielding performance due to the absence of an amine curing agent. The neutron shielding material consists of a polymerization initiator, a polymerization component, a density increasing agent and a boron compound. Does not contain a curing agent and the hydrogen content is increased by hydrogenating the cyclic rings in the epoxy resin. (RDC 1/7/2011)