The Fifth Nuclear Forensics International Collaborative Materials Exercise – The Israeli Experience

The fifth Nuclear Forensics International Technical Working Group (ITWG) Collaborative Materials Exercise (CMX-5) is an international “paired comparison” exercise that included 21 laboratories worldwide. This is the first collaborative material exercise that the Israeli nuclear forensics laboratory has participated in. It was carried out from January to March 2017. The exercise involved two enriched uranium oxide nuclear fuel pellets that were distributed to each participating laboratory for analyses and characterization, including measurements such as isotopic abundance, chemical form, trace element content, morphological characteristics and other measurable features. During the exercise three analytical reports were submitted to the exercise coordinators with timelines that adhere to the timelines for reporting in the IAEA guidance document on nuclear forensics of 24 hours, one week, and two months.

Each laboratory was asked to support legal investigations by identifying similarities and differences between the two pellets, implementing nuclear forensics analyses. Subsequently, the following methods were used by the Israeli laboratory: physical dimensions measurements, radiography, and trace elements measurement by ICP-MS, isotopic ratio measurement by ICP-MS-MC, gamma spectroscopy, morphology by HR-SEM, radio-chronometry by isotopic dilution ICP-MS (ID-ICP-MS).

In addition, traditional evidence collection such as fingerprints was practiced together with the Israeli police. During the "investigation", a sample C was found and the participating laboratories had to answer questions regarding the connection between sample C to samples A and B.

The Israeli laboratory has recognized that pellet B was inhomogeneous by measuring the isotopic uranium ratio several times using different sampling methods and receiving different results in each measurement. The same conclusion was reached by some of the other laboratories by performing particle analysis using a Secondary Ion Mass Spectrometer (SIMS), which is a significantly more complicated method for detection of inhomogeneity.

The morphologic results suggested that that pellet A and pellet B were prepared by different processes. Trace element analysis by ICP-MS has supported this conclusion. Sample C was compared to sample A and B by comparing the trace elements in each sample.

Finally, most of our results obtained by the aforementioned methods were compatible to the results of the pellet`s manufacturer, presented at the end of the exercise. This exercise was conducted as a collaboration of several laboratories and included for the first time such nuclear forensics analysis in Israel and it helped in developing advanced nuclear forensic capabilities.