Determination of the activity concentration of a 238Pu solution by the defined solid angle method utilizing a novel dual diaphragm-detector assembly

The activity concentration of a 238Pu solution was measured by the determined solid angle method employing a novel dual diaphragm-detector assembly, which has been previously described. Due to the special requirements of the detector, a new type of source holder was developed, which consisted of sandwiching the radioisotope between two organic films called VYNS. It was experimentally demonstrated that the VYNS films do not absorb α particles, but reduce their energy by an average of 22 keV.A mean activity concentration for 238Pu of 359.10±0.8 kBq/g was measured.