RADIOISOTOPES

We have developed a simple method for the long-term monitoring of the seasonal variation of the radiocaesium radioactivity in trees using commercially available integrating dosimeters. Experiments and Monte Carlo simulations were performed to assess whether the proposed dosimeter-based method could measure the seasonal variation. From the experimental results, the performance variation among individual dosimeters was found to be 1.6%, which is sufficiently small compared with the expected seasonal variation. Moreover, the simulation results indicated that the measured value of the dosimeter increased owing to the photons passing through a stem, and a correction factor was necessary to compensate the influence of photon absorption and scattering in stem. We suggested that the simple and easy dosimeter-based method could be useful to measure the seasonal variations of radioactivity in trees.