Analysis of field test of nuclide migration in aerated loess layer

摘要

Field test of nuclide migration has been conducted as a cooperative research program between JAERI and CIRP. In the program, nuclide migration in aerated loess layer has been tested to evaluate conventional migration model demonstratively. Using the values determined from laboratory tests, concentration distribution of field test has been peaks. From the observation on water potential, adjustment was needed for water flow rate. Two values of water flow rate, 0 and 0.86 cm/d from supplemental tests, were used for the re-estimation of Sr-90 migration. Between these, 0 cm/d showed better agreement to the concentration distribution corrected with recovery atio and fitting analysis showed very low water flow rate of 0.135 cm/d. Dispersivities calculated using 0.135 cm/d of water flow rate for Sr-90 and Np-237 were almost a half as small as those obtained by fitting analysis because of difference of water saturation condition between estimation and the actual test. Though some care was needed to determine water flow rate and dispersivity, the conventional migration model was able to estimate nuclide migration in natural aerated loess layer as long as obtained an appropriate set of parameter values.