Characterisation of FiR1 TRIGA Mark II Research Reactor – A Combination of Modelling and Experimental

Characterisation of FiR1 TRIGA Mark II research reactor in Finland relies on a combination of modelling and experimental results. Modelling is used in order to form an estimation of material specific activation levels. This information is used, for example, in planning of the dismantling process and waste management. Since some uncertainties are present in modelling results, experimental verification of activity levels are needed. Non-destructive analysis (NDA) using gamma spectrometry can be carried out for gamma emitting radionuclides, whereas analysis of alpha and beta emitting radionuclides, termed also difficult to measure (DTM) radionuclides, requires chemical separations and purification of the radionuclide of interest. Due to the lengthy and costly radiochemical analysis of DTM, a scaling factor is often determined to link the gamma emitting radionuclides with DTM. For FiR1, scaling factors are determined prior to the active dismantling phase and thus activity and nuclide vector calculations of waste packages can be carried out during, or even after, the active dismantling phase.