Development of high-efficiency passive counters (HEPC) for the verification of large LEU samples

A paper describing the conceptual idea of using passive neutron assay for the verification of large size uranium samples in fuel fabrication plants was first presented at the 2001 ESARDA conference. The advantages of this technique, as a replacement of active interrogation using the PHOto-Neutron Interrogation Device (PHONID) device, were evident provided that a suitable detector with higher efficiency than those commercially available would be realised. The previous paper also included a feasibility study based on the experimental data. To implement this technique, a high-efficiency passive counter (HEPC) has been designed by the JRC, Ispra. JRC has also built a first smaller-scale prototype. This paper will describe the tests made in the PERLA laboratory and report the performance of the prototype. In parallel, the design of the large HEPC has been finalised for Euratom safeguards. Two units for the fuel fabrication plants in Dessel (B) and Juzbado (E) have been produced by a commercial manufacturer under JRC specifications. The two detectors have been installed in the two sites in summer 2004 after an extensive test campaign in PERLA. Since then they are in use and some feedback on the experience gained is reported at the end of this paper.