This paper reports the results obtained during an intercomparison exercise for the determination of difficult to measure radionuclides in activated reactor pressure vessel (RPV) steel samples. In total, eight laboratories participated analysing 14C, 55Fe and 63Ni activity concentrations in RPV steel. In addition, some laboratories also analysed 60Co activity concentrations. Corresponding activity concentrations were also determined using activation calculations. Robust statistical techniques were utilised for the analysis of the results according to ISO 13528 standard. The results showed good agreement for 55Fe and 63Ni results whereas 14C results had significant differences. 60Co results were in quite good agreement.

Determination of 14 C, 55 Fe, 63 Ni and gamma emitters in two different types of activated reactor pressure vessel (RPV) steel samples were carried out. The gamma emitters were analysed using HPGe detectors with ISOCS and standard geometry calibrations. Two radioanalytical procedures for the 14 C, 55 Fe, 63 Ni analysis were developed using inactive samples and activated samples were analysed using modified procedures. A Monte Carlo code was used for the modelling of the activation results. The obtained measured and calculated results were comparable.

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The objective of the study has been to verify the calculated residual activity in the decommissioning waste of TRIGA Mark II type research reactor FiR 1 in Finland. The knowledge of radioactive inventory of irradiated materials is important in the planning of the decommissioning activities and is essential for predicting the radiological impact to personnel and environment. Measurements are performed for low active material samples from outer parts of the reactor. Methods include gamma spectrometric measurements, composition measurements with mass spectrometry, oxidation measurements of especially C-14 in graphite and full combustion measurements of lithium enriched shielding materials. Results are compared to estimates calculated with a combined Monte Carlo model of the reactor and a point-depletion code modelling the irradiation history. Decommissioning waste consists mainly of ordinary concrete, aluminium, steel and graphite parts. Only preliminary measurements of low active samples are reported so far, but the same methods will be used later for characterizing and classifying dismantling waste. Some discussion of characterization requirements and future sampling is also included.

The effects of simulant groundwater composition, pH and temperature on the dissolution and alteration of Na- and Ca-montmorillonite have been studied. Prior to the experiments, Wyoming type Na-montmorillonite, Swy-2, was purified to decrease the amount of accessory minerals. For Ca-montmorillonite experiments, the interlayer cation Na+ of purified Swy-2 was exchanged with Ca2+. The batch experiments were conducted with the purified montmorillonites in simulated fresh and saline waters at 25°C and 60°C under anaerobic conditions in an Ar atmosphere. The concentrations of Si, Al, Fe and Mg were analysed from ultra-filtered solution samples with High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS) as a function of dissolution time. The pH evolution was also measured. The solid smectite phases were analysed with X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD analyses indicated that the nature of the smectite mineral did not change over 140 days. However, the experimental conditions, more or less, modified the structure (e.g. the layer stacking of montmorilllonite; the partial dissolution of the smectite), which cannot be detected by XRD but was evidenced by chemical data, and can be considered as a possible contributor to the stacking faults of the montmorillonite. The log rates (mol g–1 s–1), based on the dissolved amount of Si, varied between –10.64 and –12.13 depending on the experimental conditions.