We assessed the repeatability and reproducibility of methods for determining low dissolved radiocesium concentrations in freshwater in Fukushima. Twenty-one laboratories pre-concentrated three of 10 L samples by five different pre-concentration methods (Prussian-blue-impregnated filter cartridges, coprecipitation with ammonium phosphomolybdate, evaporation, solid-phase extraction disks, and ion-exchange resin columns), and activity of radiocesium was measured. The z-scores for all of the 137 Cs results were within ± 2, indicating that the methods were a good degree of precision. The relative standard deviations (RSDs) indicating the reproducibility among different laboratories were larger than the RSDs indicating the repeatability in each separate laboratory.
A new method of evaluating the distribution coefficient (K d) of radioactive Sr was examined. The method is based on the measurement of the solid-liquid concentration distribution ratio (R d) of background stable Sr. To verify the method, the K d ' s of both the radioactive Sr and stable Sr were simultaneously measured by batch sorption experiments in which radioactive Sr with a constant concentration and stable Sr with various concentrations coexisted. The R d of background stable Sr was then measured by extraction with 0. 1 ~ CH3COONHd and 0. 1 ~ HC1 solutions to compare R d with K d. The results showed that the K d ' s of radioactive Sr agreed with those of stable Sr, and that the R d corresponded to the K d when the liquid-phase concentration of stable Sr approached the background level. This indicates that the new method of evaluating K d by using R d is applicable to Sr.
A new method of evaluating the distribution coefficient ( K d ) of radioactive Sr was examined. The method is based on the measurement of the solid-liquid concentration distribution ratio ( R d )
A simple method of evaluating the distribution coefficient (K d ) of radioactive Ni was examined. The method is based on the measurement of the solid-liquid concentration distribution ratio ( f d ) of background stable Ni. To verify the method, the K d 's of both the radioactive Ni and stable Ni were simultaneously measured by using three different samples through batch sorption experiments in which radioactive Ni with a constant concentration and stable Ni with various concentrations coexisted. The f d of background stable Ni was then measured by extraction with 0.1 N CH 3 COONH 4 and 0.1 N HCl solutions to compare f d with K d . The results showed that the K d 's of radioactive Ni agreed with those of stable Ni, and that the f d corresponded to the K d when the liquid-phase concentration of stable Ni approached the background level. This indicates that the method of evaluating K d by using f d is applicable to Ni within the experiment.
Low-level radioactive waste (LLRW) is disposed of by shallow land burial. Reinforced concrete is used as the radioactive waste repository. However, the concrete structure is in contact with water and will gradually degrade over an extended period of time due to leaching.It is important to investigate the interaction between radionuclides and degraded concrete in the safety assessment of nuclear waste disposal. The authors measured the distribution coefficients (Kd) of various radionuclides for calcium-leached mortars. The calcium-leached mortars were prepared by an accelerated leaching test for mortar based on the electrical potential gradient. These degraded conditions are similar to that of degraded concrete in contact with water for a long period of time. The degradation degree of calcium-leached mortar is evaluated by the CaO/SiO2 molarratio (Ca/Si ratio) of calcium silicate hydrate (C-S-H).As a result, the relationship between Kd and the Ca/Si ratio in C-S-H can be roughly grouped into the following three types:1.137Cs and 85Sr – Kd decreases with an increase in the Ca/Si ratio.2. 95mTc and 110mAg – There is no correlation between Kd and the Ca/Si ratio.3. 14C, 241Am and 125I – Kd increases with an increase in the Ca/Si ratio.
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