The evaluation of data from the MACRO tracer experiment

Watari, Shingo

On understanding the radionuclide transport in Natural Barrier in radioactive waste isolation research, the macroscopic dispersion in heterogeneous permeability field in the underground rock is regarded as an important process. Therefore, Japan Nuclear Cycle Development Institute (JNC) developed the MACRO experiment with an artificial heterogeneous permeability field and has been conducted lots of tracer experiments. To estimate the effect of characteristics of field on the macroscopic dispersion using data from those tracer experiments, the evaluation of dispersion coefficient is required. In this report, the macroscopic dispersion coefficients were evaluated for the results of the tracer experiments using the MACRO facility with a single well. The coefficients for the experiments of 18 cases were evaluated by the fitting of analytical solution to the breakthrough curve measured in the Well. In the evaluations, the correction of data measured in the experiments and of the accuracy in the evaluation were considered. The conclusions are as follows. (1)The macroscopic dispersion coefficients for 18 cases were evaluated using Least Square Method by fitting the analytical evaluation to the result of experiment. Consequently, the coefficients for 7 cases were evaluated with not enough accurate fitting results. Therefore, another evaluations for those 7 cases were required to be with more accuracy. Then, those coefficients were evaluated with enough accuracy. (2)It was verified that the macroscopic dispersion coefficient tend to be increased with increase of the average radius of tracer front. In some cases, however, the trend was not verified because of the limit of accuracy for data measured in the experiment and for the evaluation method of the coefficient. (3)It was found that the macroscopic dispersion coefficients evaluated for the cases with heterogeneous permeability field type B tend to be higher than those with heterogeneous permeability field type A.