Derivation of V function for LR 115 SSNTD from its sensitivity to 220Rn in a diffusion chamber.

The sensitivity of the LR 115 detector inside a diffusion chamber to (220)Rn gas concentration is dependent on the removed active layer thickness during chemical etching. This dependence is related to the V function for the LR 115 detector (where V is the ratio between the track etch velocity V(t) and the bulk etch velocity V(b)) and the geometry of the diffusion chamber. The present paper presents the experimentally determined relationship between the sensitivity of the LR 115 detector inside a Karlsruhe diffusion chamber (determined from the number of etched tracks completely penetrating the active cellulose nitrate layer) and the removed active layer thickness. These data were used to derive the V function for the LR 115 detector, which took the functional form of the Durrani-Green's function, i.e., V=1+((a1e-)(a2R+a3e(-a)4R))(1(-e)(-a5R)), with the best-fitted constants as a(1)=14.50, a(2)=0.50, a(3)=3.9 and a(4)=0.066.

110mAg root and foliar uptake in vegetables and its migration in soil.

110mAg, as a radionuclide of corrosion products in water-cooled nuclear reactors, was detected in the liquid effluents of Guangdong Daya Bay Nuclear Power Station (GNPS) of Daya Bay under normal operation conditions. Experiments on a simulated terrestrial agricultural ecosystem were carried out using the pot experiment approach. The most common plants in Hong Kong and the South China vegetable gardens such as lettuce, Chinese spinach, kale, carrot, pepper, eggplant, bean, flowering cabbage, celery, European onion and cucumber were selected for (110m)Ag root and foliar uptake tests. The results show that carrot, kale and flowering cabbage have the greatest values of soil to plant transfer factor among the vegetables, while(110m)Ag can be transferred to Chinese spinach via foliar uptake. Flowering cabbage, the most popular leafy vegetable locally, could be used as a biomonitor for the radioisotope contamination in vegetables. Soil column and adsorption tests were also carried out to study the leaching ability and distribution coefficient (K(d)) of (110m)Ag in the soil. The results show that most of the radionuclide was adsorbed in the top 1 cm of soil regardless of the pH value. The K(d) was also determined.

Uptake of 137Cs and 90Sr in rice plants.

In order to study the transfer of water-borne 137Cs and 90Sr into rice plants, pot experiments were done by growing rice plants on soils taken from rice beds near two nuclear power plants: Qinshan Nuclear Power Plant and Daya Bay Nuclear Power Plant in China. The vertical migration of 137Cs and 90Sr in the soil samples was studied, and results show that almost all the contaminants were retained in the top 1 cm of soil with at most a few percent down to 3 cm of soil. The areal transfer factors of 137Cs and 90Sr were studied by adding various activity concentrations of the two radionuclides to the irrigation water and then measuring the activity concentration in the various rice tissues. The areal transfer factors were also analyzed for their dependence on soil characteristics, time and duration of the contamination. The areal transfer factors obtained in this study refer to the absorption of the fallout nuclides deposited in the irrigation water in a rice field as opposed to other studies that deal with uniform activity concentration in the soils.