Direct Quantitation of ¹³⁵Cs in Spent Cs Adsorbent Used for the Decontamination of Radiocesium-Containing Water by Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Abstract

The long-term safety assessment of spent Cs adsorbents produced during the decontamination of radiocesium-containing water at the Fukushima Daiichi nuclear power plant requires one to estimate their 135Cs content prior to final disposal. 135Cs is usually quantified by inductively coupled plasma mass spectrometry (ICP-MS), which necessitates the elution of Cs from Cs adsorbents. However, this approach suffers from the high radiation dose from 137Cs that is present in the contaminated water and Cs adsorption irreversibility. To address these challenges, we herein employed laser ablation ICP-MS for direct quantitation of 135Cs in Cs adsorbents and used a model Cs adsorbent prepared by immersion of a commercially available Cs adsorbent into radiocesium-containing liquid waste to verify the developed technique. Crushing and subsequent coating with a nitrocellulose-based curing agent provided a thin flat surface and thus allowed for stable solid sampling during laser ablation. The use of the 135Cs/137Cs ratio and 137Cs radioactivity obtained by gamma spectrometry achieved simple and precise quantitation of 135Cs. The obtained 135Cs/137Cs ratio of 0.41 ± 0.02 well agreed with that obtained for the original liquid waste sample by solution nebulization measurements, and the proposed method was concluded to be suitable for large-scale 135Cs quantitation, requiring only very small (<10 mg) samples with total 137Cs radioactivity.

Determination of Ultratrace Level 135Cs and 135Cs/137Cs Ratio in Small Volume Seawater by Chemical Separation and Thermal Ionization Mass Spectrometry

“…The 135 Cs/ 137 Cs atomic ratio in the global fallout of nuclear weapons tests was reported to be 0.92 ± 0.5 (refer to year 1962), while much lower 135 Cs/ 137 Cs ratios of 0.29 ± 0.04 (refer to April 1986) in the Chernobyl accident release and 0.333–0.375 (refer to March 11, 2011) in the Fukushima accident release were reported. After the Fukushima Diichi nuclear power plant accident, the 135 Cs/ 137 Cs ratios in various environmental samples such as soil, lichen, moss, rice, mushroom, soybean, bark, and sediment − and waste such as spent Cs adsorbents were determined to assess the contamination level and identify the sources of 137 Cs (the damaged reactors or the spent fuel pools). However, less work has been dedicated to the determination of 135 Cs/ 137 Cs in seawater samples, especially in seawater without direct contamination.…”

Atomic spectrometry update: review of advances in the analysis of metals, chemicals and materials

“…The optimized setup was validated through testing of two radioactive Cs samples. Asai et al measured 135 Cs directly in spent adsorbent used for water decontamination using LA-ICP-MS. 197 The aim was to address the challenges of irreversible sorption and the relatively high 137 Cs radiation dose. A crushed sample was coated with a nitrocellulose based curing agent to provide a at surface for stable sampling using laser ablation.…”

“…One way of improving the ion transmission is to increase the mass bandwidth of the quadrupole mass lter and this approach has been described and used by Meyer et al for Au and composite REE NPs. 273 Aer optimization the sensitivity for 197 Au increased by a factor of 8.4 with a decrease in the LOD size from 7.0 to 4.9 nm. Increasing the quadrupole bandwidth decreases the mass resolution, allowing spectral overlap from adjacent m/z ratios and this factor allowed the sensitivity for the REES under study to increase by differing factors e.g.…”

“…A general factorial design, with nebuliser gas ow, plasma RFpower and sampling depth as the independent variables and the intensity of 197 Au as the response variable, was used by Kinnunen et al to improve the sensitivity of sNP-ICP-MS for Au NPs. 276 The optimization was performed using both Au NPs and solutions of ionic Au and the instrumental parameter values aer optimization were found to be in a good agreement for both analyte types, indicating a similar behaviour of the NPs in the plasma when compared with the dissolved analyte.…”

Atomic spectrometry update: review of advances in the analysis of metals, chemicals and materials

“…An increasingly popular technique for measurement of longlived radionuclides relevant to nuclear decommissioning is ICP-MS. Asai et al employed LA-ICP-MS for the direct measurement of 135 Cs in adsorbents, which had been used for decontamination of water at the Fukushima power plant. 216 A model Cs adsorbent was prepared, crushed and coated with a nitrocellulose-based curing agent to provide a thin, at surface to facilitate stable LA sampling. A 135 Cs/ 137 Cs isotopic ratio of 0.41 AE 0.02 agreed with solution based ICP-MS, but only required <10 mg of sample.…”