Recycling of a Disused 137Cs Sealed source
Recycling of disused sealed radioactive sources (DSRS) is one of the milestones of radioactive waste management strategy that prompts the minimisation of the radiological hazard to human health and the environment. In this respect this study spotlights recovering and purification of 137Cs as a solution (with a radioactivity of 191.5 ± 3.9 MBq) from an old disused source. The method was designed to fulfil the regulations and legislations of radiation protection giving exposure doses of the operating staff within the international permissible limits. Separation of the chemical impurities was performed by hydroxide precipitation based on pH values and solubility constants. X-ray fluorescence analysis illustrated a removal efficiency of 99% for iron and chromium, whereas the concentration of nickel and manganese decreased to 80 and 7 mg L-1, respectively, in the purified 137Cs solution. The radiochemical recovery of the purification process was determined using gamma-spectroscopy and found to be 94.4%.
The purified 137Cs solution was then used to prepare a gel-source with 20 mL cylindrical geometry. Calibration was carried out at a secondary standard laboratory “National Radioactive Measurement Laboratory” (NRML) that is traceable to the primary standard “National Physics Laboratory” in the UK (NPL), giving an activity of 10.59 MBq with relative uncertainty of 0.4-0.5%. The preparation procedure could be considered as an original, facile, feasible and cost effective method that implies beneficial reuse of a DSRS in terms of volume minimization of radioactive wastes.