Optimization and comparison of three different methods for the determination of Rn-222 in water.

Three different systems for the determination of radon in water have been examined: liquid scintillation counting (LSC), degassification followed by Lucas cell counting (LCC) and gamma counting (GC). Particular care has been devoted to the sampling methodologies of the water. Comparative results for several environmental samples are given. A critical evaluation is also given on the basis of the final aim of the measurements.

Measurements of 60Co in spoons activated by neutrons during the JCO criticality accident at Tokai-mura in 1999.

Neutron activated items from the vicinity of the place where the JCO criticality accident occurred have been used to determine the fluence of neutrons around the facility and in nearby residential areas. By using underground laboratories for measuring the activation products, it is possible to extend the study to also cover radionuclides with very low activities from long-lived radionuclides. The present study describes gamma-ray spectrometry measurements undertaken in a range of underground laboratories for the purpose of measuring (60)Co more than 2 years after the criticality event. The measurements show that neutron fluence determined from (60)Co activity is in agreement with previous measurements using the short-lived radionuclides (51)Cr and (59)Fe. Limits on contamination of the samples with (60)Co are evaluated and shown to not greatly affect the utility of neutron fluence determinations using (60)Co activation.