Technical Report NTB 86-28

Preliminary Study on the Use of Correlations for Controlling Important Radionuclide Concentrations in Waste Packages

Studies concerning correlations between "key" nuclides easily detected by high resolution gamma spectrometry and safety relevant radionuclides defined for a reference type B repository are reviewed. This survey allows an evaluation of the control of radionuclide concentrations in the waste from nuclear power plant operation by defining the detection limits of the relevant nuclides. These limits are a function of the "key" nuclide detection limits, which are themselves dependent on waste package, canister and detection characteristics: that is, isotopic and waste package compositions, shielding, distance between canister and detector, acquisition time and counting efficiency. On the basis of calculations carried out for typical packaged operational wastes from various nuclear power plants, recommendations for the use of correlations and high resolution gamma spectrometry are suggested. In all cases, the determination of the relevant nuclides is possible by correlation because the indirect detection limits of these nuclides are always lower than the concentration limits defined for the Swiss repository for low- and intermediate-level activity waste considered in "Project Gewähr 1985".