Intercomparison exercise on difficult to measure radionuclides in activated steel: statistical analysis of radioanalytical results and activation calculations

Abstract

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.

Intercomparison exercise on difficult to measure radionuclides in activated concrete—statistical analysis and comparison with activation calculations

“…Therefore, the main reason for the deviating measured results from calculated may be the uncorrect yield correction in the measurement results as discussed before. Additionally, the 55 Fe results in the activated steel [2] were also significantly different to the calculated results and one of the reasons for deviation was proposed to be the short half life (2.7 years) and unknown cooling time.…”

“…One major drawback of the ISO 13,528 standard is the lack of uncertainty considerations of the submitted results. However, due to consistency, the ISO 13,528 standard was utilised similar to the first year [2]. As the studied activated concrete was not a reference material, the assigned values were calculated using the submitted results.…”

“…(3) u x pt = 1.25 × s * ∕p 0.5 the residue was dissolved into 0.5 M HNO 3 or 1 M/3 M H 3 PO 4 , the latter acid has been discussed to cause the least amount of color quenching in LSC measurements [2,27]. Ni fractions after the anion exchange resin treatment were further purified with Ni resin (Eichrom Technologies) once or twice.…”

“…The first critical step in the analysis of non-volatile DTMs is the quantitative release of the analytes of interest from the solid matrix. Solubility of RPV steel was not problematic as seen in the results of the first intercomparison exercise [1,2], whereas activated concrete required harsh acid digestion treatments in order to obtain complete destruction of the solid matrix. Measurement of the chemical composition of the acid digested solution is critical for appropriate addition of carriers and subsequently yield correction and also for the determination of possible interfering stable elements (e.g.…”

“…A three-year intercomparison exercise project within Nordic Nuclear Safety Research (NKS) community on radiochemical analysis of difficult to measure (DTM) radionuclides in decommissioning waste began in 2019. The first year intercomparison exercise results on DTM analyses in an activated steel were published by Leskinen et al [1,2]. This paper presents the results of the second year intercomparison exercise, which was carried out on analysis of DTMs in an activated concrete.…”