Nuclear Forensic Lab Interoperability and Criminal Investigation

Abstract : The elemental and isotopic composition of radiological or nuclear material, along with itsmacroscopic and microscopic appearance, is often unique to its mode of production. In this way,such data may be used as a nuclear fingerprint for source attribution should such material beinterdicted. A key component of the nuclear fingerprint for source attribution is thedetermination of the elapsed time (age) since the last chemical purification. During production,the nuclear material is purified from radioactive decay products (progeny). After separation, thedecay products begin to accumulate. Measuring the parent-progeny ratio therefore provides theage of the nuclear material. An isotope ratio that may be used for dating nuclear material isreferred to as a radiochronometer. Currently, there is a global need for certified referencematerials for nuclear forensics work, including those for radiochronometry. This project aimed tovalidate reference materials and procedures for Nuclear Forensics Laboratories that will ensurelaboratory interoperability for the measurement of radiochronometers. Most of the focus of thisproject was on the development of the cobalt-60/nickel-60 radiochronometer, for which areference material and standard operating procedure were developed and validated through aseries of inter-comparison exercises, the latter of which involved five Canadian and oneAmerican laboratory. Two other radiochronometers, cesium-137/barium-137 and strontium-90/zirconium-90, were of interest to this project. To this end, the participating U.S. laboratorywas able to provide their work instruction describing age dating of various sources, including thecesium-137/barium-137 and strontium-90/zirconium-90 radiochronometers.