Intercomparison exercise on difficult to measure radionuclides in activated concrete\u2014statistical analysis and comparison with activation calculations

Anumaija Leskinen,Kristian Kurhela,Antti Räty,Pascal Fichet,Jacques Bubendorff,Margaux Giuliani,Susanna Salminen-Paatero,Celine Gautier,Elodie Laporte,Julia Laurila,Tommi Kekki

doi:10.1007/s10967-021-07824-7

Abstract

This paper reports the results obtained in a Nordic Nuclear Safety Research project during the second intercomparison exercise for the determination of difficult to measure radionuclides in decommissioning waste. Eight laboratories participated by carrying out radiochemical analysis of 3H, 14C, 36Cl, 41Ca, 55Fe and 63Ni in an activated concrete. In addition, gamma emitters, namely 152Eu and 60Co, were analysed. The assigned values were derived from the submitted results according to ISO 13,528 standard and the performance assessments were determined using z scores. The measured results were compared with activation calculation result showing varying degree of comparability.

Highlights

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
This paper presents the results of the second year intercomparison exercise, which was carried out on analysis of DTMs in an activated concrete
No major difficulty was observed for the 3H analysis as the analysis was carried out using thermal oxidation and the measured results were in good agreement

Summary

Introduction

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 calculation model assumed conservatively that the beam tube had been empty before the plugging, whereas in reality, several different types of research equipment with unknown time intervals had been placed inside the beam ports causing unknown amounts of neutron absorption and scattering This assumption overestimated the neutron fluxes around the beam tube, but was considered acceptable for conservative initial calculations in estimation of total waste volumes. The calculation results were used in this article by assuming that the concrete nuclide vector (relative nuclidewise activities) was correct and the results were scaled using the measured gamma-activities from the key nuclide 152Eu. the neutron flux was estimated conservatively, the chemical composition of the concrete used in the calculation model was determined from three inactive cores that had been drilled earlier from the inactive outer parts of the reactor structure as described earlier [7]. Point-depletion code ORIGEN-S uses built-in ENDF/B-VI formatted cross sections, but for illustration, Table 1 lists the activation reactions and reaction cross sections according to Ref. [12]

Methodology for statistical analysis

Findings

Conclusions