Year
2008
Abstract
Among non intrusive and non destructive assay techniques for the characterization of nuclear materials, calorimetry is considered to be the most accurate method in particular for certain large volume items. The radioactive decay of special nuclear materials is a source of heat. By quantifying the rate of heat generation in a calorimeter the quantity of material can be determined non-destructively if the relative isotopic composition is also known. The calorimetric technique has many advantages. It provides an accurate measurement, generally not subject to matrix effects as it is the case with emission or absorption methods. No initial sample preparation is needed for this non destructive technique. The size of the calorimeters is such that they are directly adapted for use with standard containers used in the nuclear industry. The assay is independent of the sample geometry and the nuclear material distribution within the item. The resurgence in nuclear power once more calls on this technology which can be applied for the assay of feed, product, scrap and waste where high accuracy is needed. For more than 30 years, flexible differential heat flow calorimeters based on the Calvet’s principle using Peltier thermal elements operated as Seebeck sensors have been used for nuclear applications including the assay of tritium and plutonium and the creation of secondary standards for other less accurate non-destructive methods. A new generation of calorimeter developed by SETARAM Instrumentation has been installed in different nuclear centers and a set of tests of performance for a batch of 15 liters units is presented to demonstrate the accuracy of this kind of equipment.