In order to clarify the behavior of radionuclides in an aerated sand layer, the column experiments with radioactive tracers (60Co, 85Sr and 137Cs) were carried out at different carrier concentrations (1.1×10-10-1×10-3mol/l). The effluent and migration of radionuclides were examined by measuring the radioactivity of effluent passed through the outlet of a column and sand collected from a column. The values of relative concentration of effluent (effluent ratio) were small in the low concentrations of stock solution below 10-6mol/l. At the high concentrations above 10-4mol/l, they became larger with increasing effluent volume. The relative concentrations of adsorption (adsorption ratio) decreased exponentially with depth of sand layer. Its values, however, indicated the smooth decrease with heightening the concentrations of stock solution. In addition, the observed values of 85Sr2+ and 137Cs+ at the depth d1/10 from sand surface corresponding to one-tenth of the relative concentration agreed relatively with the calculated values obtained from the dispersion equation. Hence, this value d1/10 under these experimental conditions may be one of the indicators for the prediction of migration of 85Sr2+ and 137Cs+ (cations) in an aerated sand layer.
The NaI (Tl) scintillation detector which was used for environmental radiation monitoring had to be concealed with a protection case so as to keep given functions under severe atmospheric conditions. In order to establish a correction method for gamma-ray energy spectra modified by the protection case, T-S (transmission-scattering) matrix whose elements were the transmission or scattering probabilities of incident photons in the protection case was constructed with the aid of the irradiation experiments using some mono-energetic gamma-ray sources and the calculation following the KLEINNISHINA formula. The correction method based on the T-S matrix was adopted for determination of the true energy spectra of gamma-rays when the NaI (Tl) scintillation detector, which was covered with the aluminum case of 4mm in thickness, was employed for the radiation monitoring in the natural environment, and it was found that the T-S matrix method was successful to correct the gamma-ray energy spectra modified by the aluminum protection case.
The translocation and absorption of 58Co (CoCl2) through a wound was investigated experimentally with mice. Physical and chemical skin damages became the objects of the investigation. Abrasion, puncture and incision were made for types of the physical damage. The chemical damage included both acid and alkaline burns. The absorptions of the radionuclide through the contaminated wounds were measured with both a 2 inches NaI (T1) scintillation detector and an auto well gamma counter at 15, 30 and 60min after the contamination. The radionuclide was hardly absorbed through an undamaged skin. After 30min, 20 to 40% of the radionuclide applied on the physically damaged skin was absorbed, but was not absorbed through the chemically damaged skin. The absorption rate through the physically damaged skin reached a maximum at 15 to 60min after the contamination. The velocity of the absorption through the physically damaged skin was 100 times as much as the chemically damaged skin. The absorption rates through the physically and the chemically damaged skins were expressed by the following formulas: A=a(1-e-bt) and A=a(ebt-1), where a and b is constant, respectively.
The evaluation method of neutron dose equivalent was studied on the basis of the albedo type neutron dosimetory to design the personnel dosimeter. The dosimeter was composed of three 6Li210B4O7(Cu) TL elements and one 7Li211B4O7(Cu) element. The equations for assessing thermal, epithermal and fast neutron dose equivalents were derived by 252Cf, 241Am-Be and PuO2 neutron sources. The minimum detectable amount of 6Li210B4O7(Cu) element to thermal neutron was 0.02 mrem. The neutron dose equivalent and the gamma one were evaluated separately within about 20% error in the mixed radiation field.
Investigation of radioactive fallout in Japan has started in 1955, being conducted at that time at various institutions such as relevant divisions of local governments, research establishments, and universities. The system of investigation and monitoring network have been organized and expanded since then, and large amounts of data are accumulated until now. This report describes the centralized management system of data on environmental radiations and radioactivities worked out at Japan Chemical Analysis Center, using YHP-3000II computer system in order to meet the increasing requirement of serviceable and readjusted data.