Absolute determination of small samples of Pu and Am by calorimetry

An extensive measurement campaign has been carried in order to recalibrate and assess the performance of the small sample calorimeter (SSCAL) that was recently upgraded. The measurements have been performed in the Performance Laboratory of the Joint Research Centreʹs (JRC) Nuclear Security Unit in Ispra (Italy) using calibrated electric heat sources and standard reference nuclear materials. The SSCAL is a heat flow calorimeter which works by measuring the voltage generated by a heat-emitting sample across a thermal gap based on a thermopile cup technology. Results of calorimetry measurements carried out, both inside and outside a well-controlled environment of a climatic chamber, on reference Pu–Ga samples and well-characterised 241Am samples are presented and discussed. The latter samples were produced at the JRC-ITU to be used by the JRC-IRMM for various cross-section measurements (total, neutron capture and 241Am(n,2n) 240Am).