The Galaxy Serpent Exercise: Methodology, Experience, and Findings of the Institute for Transuranium Elements

In the framework of the Galaxy Serpent exercise, a data set ofan unknown spent fuel material (code name Terpsichore) wascompared against three data sets associated with three distinctreactors. The data of the known materials were compiledin a model national nuclear forensics library. The comparativeevaluation aimed at (i) assessing whether the hypothetical seizureis or is not consistent with material contained in the library,and, (ii) identifying the reactor the unknown material may be associatedwith. Two different evaluation methods were applied.The first one is based on the isotope correlation techniqueand concluded that one of the three known reactors (codename Siarnaq) as potential origin of the unknown material. Thesecond method uses multivariate analysis for clustering andclassification of the data, identifying the same known reactor(Siarnaq) as the likely origin of the Terpsichore material. Thus,the evaluation resulted in a consistent answer provided by twoindependent methods. In addition to demonstrating the usefulnessof having a national nuclear forensics library, the exerciseshowed that selected statistical techniques, such as principalcomponent analysis or factor analysis, may serve to optimizethe content of a national nuclear forensics library by eliminatingredundant (correlating) variables.