The measurement of I for the cement and the paraffin solidified low and intermediate level wastes (LILWs), spent resin or evaporated bottom from the pressurized water reactor (PWR) nuclear power plants

In this paper a relatively simple and low cost analysis procedure to apply to a routine analysis of ¹²⁹I in low and intermediate level radioactive wastes (LILWs), cement and paraffin solidified evaporated bottom and spent resin, which are produced from nuclear power plants (NPPs), pressurized water reactors (PWR), is presented. The ¹²⁹I is separated from other nuclides in LILWs using an anion exchange adsorption and solvent extraction by controlling the oxidation and reduction state and is then precipitated as silver iodide for counting the beta activity with a low background gas proportional counter (GPC). The counting efficiency of GPC was varied from 4% to 8% and it was reversely proportional to the weight of AgI by a self absorption of the beta activity. Compared to a higher pH, the chemical recovery of iodide as AgI was lowered at pH 4. It was found that the chemical recovery of iodide for the cement powder showed a lower trend by increasing the cement powder weight, but it was not affected for the paraffin sample. In this experiment, the overall chemical recovery yield of the cement and paraffin solidified LILW samples and the average weight of them were 67±3% and 5.43±0.53 g, 70±7% and 10.40±1.60 g, respectively. And the minimum detectable activity (MDA) of ¹²⁹I for the cement and paraffin solidified LILW samples was calculated as 0.070 and 0.036 Bq/g, respectively. Among the analyzed cement solidified LILW samples, ¹²⁹I activity concentration of four samples was slightly higher than the MDA and their ranges were 0.076–0.114 Bq/g. Also of the analyzed paraffin solidified LILW samples, five samples contained a little higher ¹²⁹I activity concentration than the MDA and their ranges were 0.036–0.107 Bq/g.