방사평형을 이용한 방사성동위원소(RI) 폐기물의 226Ra 핵종분석 방법에 관한 연구

Abstract

A procedure for the chemical separation and quantification of radioactivity concentration for 226Ra, adifficult-to-analyze nuclide present in radioisotope(RI) waste, was established. 226Ra is an alkaline earth metal withhigh reactivity, even reacting with nitrogen. It is commonly used in radioactive sources in the form of salts, whichare water-soluble and pose significant radiological concerns. In domestic sealed radioactive waste disposal, 226Rasources present high radiotoxicity. The daughter nuclide 222Rn contributes to approximately half of the average naturalradiation dose humans receive on Earth, making the analysis of 226Ra highly important. The chemical separationmethod used coprecipitation, and the precipitate generated through the Ba(Ra)SO4 step with the addition of H2SO4and the BaCO3 step with the addition of K2CO3, was dissolved in HNO3 to prepare a sample for measurement. Afterchemical separation, the measurement of 226Ra was performed using a gamma spectrometer. Since direct spectralevaluation overlaps with the energy of 235U, a method of measuring the energy emitted from the daughter nuclides214Pb or 214Bi was used. At this point, since Rn gas may escape during the radioactive equilibrium period between theparent nuclide and the intermediate nuclide, 222Rn, breaking the equilibrium, the sample was sealed in a polycarbonatecontainer with good sealing. The measurement was performed after about 4 weeks, which is the radioactiveequilibrium period, and the radioactivity concentration was calculated. In this way, the radionuclide analysis methodfor 226Ra was established and applied to actual RI waste media such as rubber, plastic, wipers, and stainless steel,yielding recovery rates of 79.63%, 74.49%, 75.18%, and 86.98%, respectively, resulting in good outcomes.