Physicist Ian Hutcheon, of Lawrence Livermore National Laboratory, is what you might call a nuclear detective. Hutcheon’s job is to look for evidence of the production of highly enriched uranium or plutonium, the essential components of nuclear weapons.
Ian Hutcheon: Intercepted samples come in all sizes and shapes, very much in the same form as if you go down to your local police station and look at the types of evidence that are collected at crime scenes.
Hutcheon receives samples from nuclear facilities throughout the world. He then tests them for evidence of illegal materials like highly enriched uranium. It’s difficult to differentiate legal material from illegal material, Hutcheon said, because uranium is everywhere.
Ian Hutcheon: If you go out on the beach and pick up a handful of sand it contains about 4 parts per million of uranium.
Nuclear investigative testing is used by agencies such as the United Nations to monitor countries’ nuclear activities such as the production of enriched uranium and their compliance with international agreements on weapons of mass destruction.
Ian Hutcheon: Our charge is to measure the properties of the material and to demonstrate that we can do this with high precision, and that the data we can collect would stand up, for example, in a court of law.
Hutcheon and the scientific community refer to the nuclear investigations he undertakes as the field of nuclear forensics.
Ian Hutcheon: In a nutshell, nuclear forensics is much like criminal forensics. If you get a sample of unknown origin, the task would be for the nuclear forensic scientist to determine where it’s from. And so we perform physical measurements and chemical measurements of samples to characterize them.
One common material to test for is the presence of uranium isotopes. Isotopes are atoms with an unusual number of neutrons. The number of neutrons they have changes both their mass and their behavior.
Ian Hutcheon: There are basically four uranium isotopes of different mass: 234, 235, 236 and 238. So, naturally occurring Uranium has no 236. One of the things we try to do is to determine the abundance of Uranium 236 with very high sensitivity. If you find a few parts per million of Uranium 236, that tells you immediately that that sample has been in a reactor.