Baseline measurements in the assessment of ESS-specific radionuclide uptake by crops cultivated in Southern Sweden

The European Spallation Source, ESS, is a neutron research facility under construction in Lund, Southern Sweden. The Facility will produce neutrons by spallation, using a powerful linear accelerator to deliver protons to a tungsten target. In addition to the desired neutron production, a long list of radionuclides will be created as by-products of the nuclear reaction inside the target. The Swedish Radiation Safety Authority has established a list of the most relevant radionuclides, in terms of contribution to the effective dose to ESS workers and the general public, should an accidental release of irradiated target material occur. This list includes radionuclides that are not produced by the nuclear energy industry, in particular 178m Hf, 182 Ta, 187 W, 148 Gd and 173 Lu. Ongoing research efforts aim to determine the best analytical methods to assess these exotic and often difficult-to-measure radionuclides in environmental samples. This work investigates the potential of X-ray fluorescence and time-of-flight elastic Recoil detection analysis for the assessment of soil samples, and the potential of particle induced X-ray emission for the assessment of crop samples. These techniques require only simple sample preparation steps and no chemical extraction, unlike the conventional environmental monitoring methods such as inductively-coupled plasma mass spectrometry, and show promise as complimentary methods enabling fast sample throughput. This study focuses on the analysis of uncontaminated soil and crops, to provide baseline data, whilst simultaneously assessing the available measurement capabilities. For the X-ray fluorescence system used in this study, the method detection limit for W in soil was determined to be 0.147 ppth, and Zr which can be correlated with the migration of Hf was clearly measurable.