Time dependence of the removal ratio of reagents for the purification of radioactive wastewater was investigated at the Radioisotope Center of Hiroshima University.Comparison of the radioactive isotope (RI) concentration before and after purification showed that the removal ratio for¹⁴C decreased gradually by repeating the drainage, while the ratio for³H was relatively constant. Results for time dependence revealed that the removal efficiency reached a limit at treatment of300, 000liters of water, suggesting this volume is an upper limit for the disposal of effluent at our facility.

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A radiation source was developed by compressing potassium chloride powder containing naturally occurring potassium-40 radioisotopes into disks. To examine the performance of the method of compressing and forming potassium chloride powder into disks, thirteen disk-shaped radiation sources were fabricated from potassium chloride and then examined with regard to their weight, mass density, thickness, and radioactivity. The obtained results show that multiple uniform radiation sources can be simultaneously fabricated by means of the method with sufficiently low production dependences and without the requirement of special skills or techniques.
Next, the dependences of the count rate of the potassium chloride radiation source on distance, shielding thickness, and shielding materials were examined, the count rate being measured using a conventional GM survey meter. The obtained results show that the potassium chloride radiation source can be used to enable better comprehension of the characteristics of radiation, particularly, those related to the distance dependence of radiation and radiation shielding.

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