Environmental remediation for the upstream of Yotsugi Mill Tailings Pond, Ningyo-toge Uranium Mine

Saito, Hiroshi; Sato, Yasushi*; Sakamoto, Atsushi*; Torikai, Kazuyoshi; Fukushima, Shigeru; Sakao, Ryota; Taki, Tomihiro

JAEA-Technology 2015-063, 119 Pages, 2016/03

JAEA-Technology-2015-063.pdf:86.2MB

Ningyo-toge Environmental Engineering Center has been conducting environmental remediation of the Ningyo-toge Uranium Mine, after decades of mine-related activities were terminated. Its purposes are to take measures to ensure safety and radiation protection from the exposure pathways to humans in future, and to prevent the occurrence of mining pollution. As part of the remediation, upstream part of the Yotsugi Mill Tailings Pond, the highest prioritized facility, has been remediated to fiscal year 2012. Multi-layered capping has been constructed using natural material, after specifications and whole procedure being examined in terms of long-term stability, radiation protection, economics, etc. Monitoring has been carried out to confirm the effectiveness of the capping, in terms of settlement, dose and radon exhalation rates, etc. Monitoring of drainage volume of penetrated rainwater is planned. Accumulated data will be examined and used for remediation of downstream part of the Pond.

Numerical evaluation of a multiple soil barrier system preventing water infiltration

Takayama, Yusuke*; Ikuta, Yuki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Taki, Tomihiro; Sakao, Ryota; Ichikawa, Yasuaki*

Unsaturated Soils; Research & Applications, p.659 - 665, 2014/06

In this paper, a multiple unsaturated soil barrier consisting of gravel, sand and bentonite-mixed soil layers is considered as a hardly permeable covering to prevent rainwater from infiltrating into waste deposits. Not only the quite low permeability of bentonite-mixed soil layer but also a function of capillary barrier between granular layers having different water-retention capabilities is expected to prevent water infiltration. A series of numerical simulation is carried out to evaluate performance of the multiple soil barrier using saturated/unsaturated soil/water coupled FE computation technique. The multiple unsaturated soil barrier system considered here is 10m long and 1.5 m thick consisting of sandy soil surface, sand filter, gravel layer, sand filter and bentonite-mixed clayey layer. And the soil barrier system is assumed to be placed as a covering with a 5% inclination on the waste deposit. The performance of the multiple soil barrier system is shown as a management chart to maintain impermeable ability associated with possible rainfall intensity. Particularly, in this paper, actual rainfall record in Okayama area is employed to determine the rainfall intensity which is imposed as a boundary condition in the computation. According to the simulation results, it is found that the capillary barrier is a key issue in evaluating the long term performance of the barrier system. And, it is confirmed that the barrier system considered in this paper can work well against the maximum intensity of the rainfall in the past record.

Evalution of settlement at the upstream of the Mill Tailings Pond, Ningyo-toge Uranium Mine

Sasaki, Yosuke*; Takayama, Yusuke*; Ikuta, Yuki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Sakao, Ryota; Taki, Tomihiro

no journal, , 

As part of environmental remediation of Ningyo-toge Uranium Mine, multi-layered capping is constructed to reduce rainwater infiltration at the upstream of the Mill Tailings Pond. Settlement is expected due to consolidation characteristics of mill tailings and clayish sediments which exist below capping. Numerical simulation is carried out to expect the settlement amount during and after the capping construction. Settlement amount has been measured periodically, and the simulation result and measurement data are compared to evaluate the simulation method.

applied example MCNP5 on skyshine of nuclear facility

Zaima, Naoki; Naganuma, Masaki; Sakao, Ryota; Tokizawa, Takayuki

no journal, , 

In the field of safety analysis on nuclear fuel facility, conventional calculation code (QAD/G33 etc.) had been used. However some confines of codes had lead overestimation. At the chance of trial for shielding or skyshine calculation, Monte Carlo transport calculation code MCNP5 was applied. The comparison between both, error estimations, model designs, several artifices will be introduced.

Applied example MCNP5 on ambient dose evaluation from nuclear facility

Zaima, Naoki; Naganuma, Masaki; Sakao, Ryota

no journal, , 

no abstracts in English