The design of the demountable CA503-260 High Sensitivity In-Line (Glove Box) Calorimeter is based around a sample well that maintains glove box integrity. The thermal element is positioned from below and fixed to the underside of the glove box floor. The sample well becomes part of the calorimeter inner cylinder or measurement chamber. The design has application to a wide range of measurement requirements including international safeguards measurements, shipper-receiver difference measurements, in-plant accountancy measurements and anomaly resolution in passive neutron coincidence counting or segmented gamma-ray scanning. The instrument also has a role in replacing a portion of Destructive Assay (DA).