報告書番号

N05006

タイトル（和文）

ベントナイトグラウチングの放射性廃棄物処分への適用における成立条件の検討

タイトル（英文）

Approval condition in application of bentonite grouting to the radioactive waste disposal.

概要 （図表や脚注は「報告書全文」に掲載しております）

高レベル放射性廃棄物処分事業におけるグラウチングに関して，材料にベントナイト(Be)を用いた場合の懸濁液の流動特性と透水特性を室内実験によって把握し，グラウチングにおけるBe材適用条件について検討した．Be懸濁液の配合と透水係数との関係に基づき，健岩部と同程度の透水性となるBe懸濁液の配合を決定し，粘性を計測した．その結果、ダム基礎で対象とする程度の岩盤割れ目への注入は困難であるが，塩化ナトリウム（NaCl）を添加すると岩盤への注入が可能な粘性に下がることがわかった．また，Be:水：NaCl＝20：20：1の試料の透水試験の結果、初期透水係数1E-6(cm/sec)が1E-8～-9(cm/sec)に低下することがわかった．以上より，NaClを添加したBe懸濁液は岩盤への注入が可能で，地下水が浸入することによりBeが膨潤し，止水効果の持続性や流出に対する安定性が期待できる．

概要 （英文）

The purpose of this study is to understand the flow properties and the permeability of bentonite grout added NaCl by the laboratory tests, and to clarify the approval condition of bentonite as materials. The viscosity of the bentonite suspension was measured under the weight ratio of water and bentonite（W/B） is 6 to 20. The suspension of which W/B is smaller than 10 is difficult to inject into the rock joints, because the viscosity is higher than the thickest cement milk on dam grouting. When the necessary permeability of the clay grout is assumed to be 1E-7(cm/sec), the W/B becomes 10 or less. Then, when we add NaCl to the suspension of which W/B is 6, the viscosity decreases as the amount of NaCl increases. The injectable viscosity is achieved by adding NaCl as the proportion of water to NaCl is 1 to 40. Next, the permeability of the bentonite suspension that added NaCl was examined by the falling head permeability test. It was found that the initial permeability 1E-6（cm/sec) decreased to 1E-8～-9（cm/sec) by the test of the sample of "B:W:NaCl = 20:20:1" for 10 days . From these results, the suspension to inject into the rock joints can be made by adding NaCl. And it was clarified that the groundwater permeation to the suspension causes the decrease of the permeability. In addition, the bentonite is swelling according to the infiltration of underground water, the persistence in the suppression effect of diffusion and stability to erosion can be expected.

報告者

キーワード