Interception, loss and translocation of ⁸⁵Sr, ¹⁰³Ru and ¹³⁴Cs in the rice plants sprayed with a mixed Rl solution

Korea Atomic Energy Research Institute, Nuclear Environment Research Team, P.O. Box 105, 305-600 Yusong, Taejon, Korea

Abstract

Interception, loss and translocation of ⁸⁵Sr, ¹⁰³Ru and ¹³⁴Cs in rice plants were investigated through a greenhouse experiment in which the whole aboveground plant parts were exposed to radioactive spray at 6 different growth stages. Showing little difference among radionuclides, the interception factor tended to increase as the plant grew to maturity. The highest observed factor was 0.94. The fractions of the intercepted activity that remained in rice plants at harvest were 0.19~0.42 for ⁸⁵Sr, 0.23~0.62 for ¹⁰³Ru and 0.11~0.69 for ¹³⁴Cs, depending on application times. The translocation factors for hulled seeds were in the range of 5.8x10^-4~3.2x10^-2 for ⁸⁵Sr, 1.6x10^-4~7.6x10^-3 for ¹⁰³Ru and 3.2x10^-2~2.0x10^-1 for ¹³⁴Cs indicating the highest mobility of ¹³⁴Cs. The greatest translocation factor of every radionuclide came when plants were contaminated at the active seed growth stage. It was indicated that weathering loss and translocation would not greatly depend on the rain frequency if it differs by a factor of less than 2. Based on the experimental results, the concentrations of ⁸⁵Sr, ⁹⁰Sr, ¹⁰³Ru, ¹⁰⁶Ru, ¹³⁴Cs and, ¹³⁷Cs in hulled rice seeds at harvest were estimated for their deposition at different growth stages.