Environmental remediation activities at the Ningyo-toge Uranium Mine, Japan

Ningyo-toge Uranium Mine is subject to the environmental remediation. The main purposes are to take measures to ensure the radiation protection from the exposure pathways to humans in future, and to prevent the occurrence of mining pollution. The Mill Tailings Pond in the Ningyo-toge Uranium Mine has deposited mining waste and impounded water as a buffer reservoir before it is transferred to the Water Treatment Facility. It is located at the upstream of the water-source river, and therefore, for the environmental remediation, the highest priority has been put to it among many facilities in the Mine. So far, basic concept has been examined and planning has been carried out for the remediation. Also, a great number of data has been acquired, and using the data, some remediation activities have already begun, including designing for the upstream part of the Mill Tailings Pond. According to the current plan, the Mill Tailings Pond will be covered by capping following dewatering and compressing of mill tailings. The capping is composed of 'radon barrier' for lowering radon-gas dissipation and dose rate, and its protection layer. Natural materials are planned to be used for the capping to alleviate the future maintenance. After capping, data will be accumulated to verify the effectiveness of the capping, and if proved effective, it will be utilized for the capping of the downstream part. (author)