The Radionuclide Transport Analysis in the former Yotsugi open pit site

Nagara, Shuichi; Matsumura, Toshihiro; Sato, Kazuhiko ; Tokizawa, Takayuki

A one-dimensional numerical solute-transport analysis utilizing a simulation code named NESTOR, involving a literature survey on analytical parameters has been carried out for the purpose of an understanding radionuclide transport in groundwater in and around the former Yotsugi open pit site at the Ningyo-Toge Environmental Engineering Center, JNC. Prior to the analysis, data set was prepared referring to available documents on site characteristics and one on disposal of radwaste. A simplified model in which the site was divided into seven blocks according to its geographical-hydrological feature and has boreholes downward regarded as assessment points was applied on the analysis. As a result, The highest concentrations of radionuclide is 8.5710 Bq/m of Po-210 at assessment points. The highest concentration of U-238 is in the order of magnitude of 10 Bq/m. This figure is lower by 1 order than a standard value for mine- and waste-water on the safety rule of Ningyo-Toge mine and the same orders as surface-water on the agreement with Okayama prefecture. If the analysis result in this time and the present concentration in groundwater are measured, the former data became lower about 7 orders by U-238 concentrations and became lower about 6 orders by Ra-226 concentrations. It is thought that this cause is that U and Ra which exist around the former Yotsugi open pit sit before taking reclamation cannot be taking into consideration in analysis.