Gamma spectroscopic determination of 137Cs in milk, using simultaneous equations: collaborative study

Abstract A gamma spectroscopic method, using a sodium iodide (thallium-activated) crystal, was evaluated by 25 collaborators for the determination of cesium-137 in milk. Overall average recoveries of 295±18.1 and 53±5.3 pCi/L were obtained for samples containing 305 and 52 pCi/L, respectively. These samples also contained iodine-131 and barium-140, which did not interfere with the analyses. The slight bias on the low side and the greater dispersion of results for the low level sample were not considered serious. The method has been adopted as official first action.