Spatial dose distribution curves based on the measurement of clinical cases, theoretical and experimental analyses were studied around the patients treated with 131I for thyroid carcinoma. When the maximum activity in a patient was 15mCi, external exposure at 50cm from a side of the subject's was 7.64mR/hr for theoretical value, 6.5mR/hr for experimental value, and 3.2mR/hr for clinical case. The total exposure at 1m from the side of the breast in clinical cases 1, 2 and 3 were obtained 0.775, 0.197 and 0.079R, respectively. The result of case 1 suggested that special restriction need be placed on the patient's proximity to other individual.
The migration of 60Co, 85Sr and 137Cs in saturated sandy soil layer has been investigated by using saturated zone model apparatus (saturated zone: 40cmW×70cmL×25cmH). Tendencies of mobility among these radionuclides are 85Sr>60Co>137Cs at the plume of high concentration and 60Co>137Cs>85Sr at the plume of low concentration. Mobilities of 60Co and 137Cs at the plume of low concentration seem to be due to form of insoluble hydroxide 60Co(OH)2 and adsorption of 137Cs on silt. Therefore, it is important to consider both insoluble hydroxide and particulate transports for safety assessment of LLW shallow land disposal.
The literature on plutonium aerosols was surveyed for information (1) particle size distributions of plutonium aerosols from nuclear facilities, (2) collection efficiencies for plutonium aerosol particles of multi-stage HEPA filter systems used as exhaust air cleaning systems in these facilities, and (3) particle size distributions of plutonium aerosols discharged through the air cleaning systems. Following are the results. 1. Mean particle sizes of plutonium aerosols from chemical plants are about 0.5μm AMAD and from fuel fabrication plants about 3μcm AMAD. 2. Average collection efficiencies for plutonium aerosols of the first and second stage HEPA filters in the multi-stage HEPA filter systems exceed 99.99%. 3. Mean particle sizes of plutonium aerosols discharged through the air cleaning systems are 0.2μm-0.4μm AMAD for chemical plants and 0.5μm-1.2μm AMAD for fuel fabrication plants.