Multiactinide Analysis with Accelerator Mass Spectrometry for Ultratrace Determination in Small Samples: Application to an in Situ Radionuclide Tracer Test within the Colloid Formation and Migration Experiment at the Grimsel Test Site (Switzerland)

Abstract

The multiactinide analysis with accelerator mass spectrometry (AMS) was applied to samples collected from the run 13-05 of the Colloid Formation and Migration (CFM) experiment at the Grimsel Test Site (GTS). In this in situ radionuclide tracer test, the environmental behavior of U,Np, Pu, andAm was investigated in a water conductive shear zone under conditions relevant for a nuclear waste repository in crystalline rock. The concentration of the actinides in the GTS groundwater was determined with AMS over 6 orders of magnitude from ∼15 pg/g down to ∼25 ag/g. Levels above 10 fg/g were investigated with both sector field inductively coupled plasma mass spectrometry (SF-ICPMS) and AMS. Agreement within a relative uncertainty of 50% was found for Np,Pu, and Am concentrations determined with the two analytical methods. With the extreme sensitivity of AMS, the long-term release and retention of the actinides was investigated over 8 months in the tailing of the breakthrough curve of run 13-05 as well as in samples collected up to 22 months after. Furthermore, the evidence of masses 241 and 244 u in the CFM samples most probably representingAm and Pu employed in a previous tracer test demonstrated the analytical capability of AMS for in situ studies lasting more than a decade.

GGR Biennial Critical Review: Analytical Developments Since 2014

“…After validation of the method using the CRM IAEA 443, they analysed groundwater samples from an in situ radionuclide tracer test (Quinto et al . ) in a deep underground laboratory in Switzerland and natural water samples affected solely by global fallout. They demonstrated a detection limit of ∼ 10 5 atoms per sample and potential of the method for soil and sediment samples.…”

“…From a maximum test portion size of 250 g of groundwater or seawater, they concentrated actinides by iron hydroxide coprecipitation and measured them sequentially without any chemical separation (e.g., cost-and labour-intensive ion exchange) of the actinides from each other. After validation of the method using the CRM IAEA 443, they analysed groundwater samples from an in situ radionuclide tracer test (Quinto et al 2017) in a deep underground laboratory in Switzerland and natural water samples affected solely by global fallout. They demonstrated a detection limit of $ 10 5 atoms per sample and potential of the method for soil and sediment samples.…”

Bentonite Nanoparticle Stability and the Effect of Fulvic Acids: Experiments and Modelling

“…In the successive colloid formation and migration experiment (CFM), huge geotechnical effort was undertaken to hydraulically isolate the MI shear zone from the artificial hydraulic gradient due to the GTS tunnel construction. After several conservative and "homologue" tracer tests, radioactive tracer tests were performed [14][15][16].…”

Background analysis of actinide and 99Tc tracers in the frame of an in-situ bentonite diffusion experiment at the Grimsel Test Site

“…The expected ultra-trace radionuclide concentrations could only be addressed via the high analytical sensitivity of Accelerator Mass Spectrometry. Actinide tracers were analyzed at the 3 MV tandem accelerator of VERA, while 99 Tc at the 14 MV tandem accelerator of TUM, enabling quantification at the level of 25 at/g and 0.5 fg/g, respectively [2,3]. In order to identify radionuclides originating from the LIT, an extensive analysis of the background originating from previous in-situ radionuclide tracer tests [2] was undertaken.…”

“…Actinide tracers were analyzed at the 3 MV tandem accelerator of VERA, while 99 Tc at the 14 MV tandem accelerator of TUM, enabling quantification at the level of 25 at/g and 0.5 fg/g, respectively [2,3]. In order to identify radionuclides originating from the LIT, an extensive analysis of the background originating from previous in-situ radionuclide tracer tests [2] was undertaken. First results suggest, that 242 Pu release from the bentonite could not be detected.…”