A muon is a subatomic particle that is similar to an electron but has two hundred times as much mass. It has an electrical charge of minus one and a spin of one half. It is categorized as a “lepton” which means that it does not have any substructure composed of simpler particles. Muons are unstable and only have a half life of about two millionths of a second. However, this is longer than the half life of many subatomic particles. When a muon decays, it produces an electron and two neutrinos. Because it is not affected as much by magnetic fields as an electron, it can penetrate much further into solid objects. Muons produced by cosmic rays can penetrate deep into the Earth. About 10,000 muons are hitting every square yard of the earth’s surface every minute.
The National Nuclear Laboratory (NNL) is a UK government owned and operated nuclear services technology provider covering the whole of the nuclear fuel cycle. Almost ten years ago, researchers at the (NNL) and Glasgow University in Scotland discovered that muons interacted differently when they encountered uranium as opposed to other elements. Because of the greater density of the uranium, instead of passing right through, the muons are scattered. Lynkeos, a commercial company, was formed to take advantage of this behavior by turning it into a commercial product for the nuclear industry. It has the potential to aid decommissioning, detection and storage of radioactive materials. This could save the nuclear industry millions of dollars.
The muon detection technology, called the Muon Imaging System (MIS) is already in use at Sellafield. The owners of the Cumbrian reprocessing plant have invested over six million dollars in the research. Innovate UK also supplied about two million dollars. Additional funding was supplied by the Engineering and Physical Sciences Research Council, the Science and Technology Facilities Council and the Royal Society of Edinburgh. The UK firm hopes to export the MIS to other countries across the globe to help with the cleanup of nuclear sites.
The CEO of Lynkeos said “The Muon Imaging System can be used for a variety of purposes, whether that’s inspecting old/spent material used in nuclear production to see if it’s safe to store, for imaging the products of thermal treatment processes or inspecting historic waste without needing to chip away its concrete encasing.”
“This form of detection is providing the nuclear industry with an inexpensive method for testing waste materials, to which there is currently no other technological option. This should help to significantly lower costs within the nuclear industry.”
I have already blogged about the use of a muon detection system to search for the nuclear fuel in the reactor cores in the ruins of the reactors in Fukushima, Japan. The muon detectors did not show that the uranium fuel was still in its original position in the core of the reactor. This indicated that the fuel had melted down through the bottom of the containment vessel.