Large volume and sensitive calorimeter for nuclear applications: latest developments for greater accuracy and shorter measurement times.

Among non-intrusive and non-destructive assay techniques for the characterization of nuclear materials, calorimetry is the most accurate, particularly for large volume items. The radioactive decay of special nuclear materials produces heat. By quantifying the rate of heat generation in a calorimeter, the quantity of material can be determined non-destructively. The calorimetric technique has many advantages. It provides an accurate measurement, generally not subject to matrix effects. No initial sample preparation is needed for this non-destructive technique. The size of the calorimeters is such that they are directly suitable 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 technology can be applied for the assay of foodstuffs, products and waste where high accuracy is required. For more than 30 years, flexible differential heat flow calorimeters using Peltier thermal elements have been used for nuclear applications including the assay of tritium and plutonium. This document presents some recent new developments.