| Popis: |
We propose that 132^Cs (E_γ = 668 keV and T_1/2 = 6.5 d) can replace 137^Cs (E_γ = 662 keV and T_1/2 = 30 y) as a new environmental tracer of cesium. The alternative tracer, 132^Cs, can potentially reveal the short-time dynamics in an environment, which are considered to dominate radioactive cesium absorption after nuclear accidents. We first investigate the production yield and radioactive purity of 132^Cs in a production experiment at the Cyclotron and Radioisotope Center of Tohoku University. The 132^Cs was produced via the 133^Cs(n,2n) reaction with neutrons generated by bombarding accelerated deuterons onto a 4 mm-thick neutron converter made of carbon. The generated neutrons were then irradiated onto a Cs_2CO_3 sample. The experiment yielded 102.2 kBq/g of 132^Cs, sufficient for tracing environmental cesium. The radioactive purity reached 98%, indicating negligible amounts of by-products. Next, a 132^Cs tracer experiment was performed on three different soil samples: an andosol soil, a haplic fluvisol soil, and a gleyic fluvisol soil. This feasibility study confirmed that the new tracer can measure soil cesium distributions as adequately as the 137^Cs tracer. Thus, we conclude that 132^Cs is a promising alternative environmental tracer of 137^Cs. |
