福島第一発電所事故により発生した大量の汚染土壌は、30年間の中間貯蔵を

福島第一発電所事故により発生した大量の汚染土壌は、30年間の中間貯蔵を経て最終処分される。その際、減容化処理を適用することで低放射能濃度となった土壌については再資源化し、放射性Csが濃縮された高濃度生成物を最終処分する考え方が示されている。本研究では、減容化処理の選択肢の一つとして、酸洗浄による放射性Csの溶出と吸着回収を組み合わせた化学処理プロセスを提案する。このプロセスでは、無機酸で汚染土壌中の放射性Csを溶出させ、放射能濃度を低減させる。また、洗浄廃液中の放射性Csは、プルシアンブルーにより吸着回収する。本研究では、福島県内の3ヶ所から採取した汚染土壌(A,BとC)を用いて、プロセスの成立性を検討するための基礎データを取得した。
2M(M=mol/dm3) HCl、HNO3、H2SO4を用いて50℃における洗浄時間(1,3,5,7時間)の影響を検討した結果、土壌AとBはいずれの酸を用いても、除染率は時間と共に増加し、H2SO4を用いた場合5時間以上処理すると、除染率の増加は緩やかになった。土壌Cについては、50℃ではH2SO4のみ除染効果がみられたが、他の土壌と比べると、除染率は非常に低い値となった。ただし、7時間以上処理を継続すると、除染率は更に増加する可能性があると推察する。また、処理温度(25,50,80,95℃)の影響を検討した結果、いずれの酸を用いても除染率は温度と共に増加した。土壌A及びBは80℃までの処理温度では、H2SO4による除染効果が高く、95℃ではHClの方が除染効果は高くなった。土壌Cは、25℃で処理すると除染効果はほとんど見られず、50℃以上の処理温度では、H2SO4による除染効果が最も高かった。土壌AとBは95℃のHClを用いて5時間処理すると、除染率はそれぞれ72と88%となった。また、土壌Cは、95℃のH2SO4で5時間処理すると除染率は48%となった。この結果から、各土壌の残留放射能濃度(134Csと137Csの合計)はそれぞれ、33.4 kBq/kg (土壌A), 8.9 kBq/kg(土壌B)、17.1 kBq/kg(土壌C)と見積もられた。残留放射能濃度の高い土壌Aを用いて、繰り返し洗浄した結果、95℃のHClで2回洗浄すると、除染率は83%に到達し、残留放射能濃度は20.4 kBq/kgとなる。従って、中間貯蔵期間による減衰を考慮すると、30年後の放射能濃度は約8 kBq/kgになると考えられる。洗浄により発生した酸廃液中には土壌から溶出したFe(Ⅲ)が溶存する。そこに、K4[Fe(CN)6]を添加し、プルシアンブルーを生成させて、放射性Csを吸着回収した。その結果、いずれの酸廃液においても放射能濃度は排水濃度限度以下となり、放射性セシウムを高放射能濃度の沈殿物として回収できることが分かった。

結果 (英語) 1:

Large amounts of contaminated soil caused by the Fukushima Daiichi power plant will be landfilled through intermediate storage for 30 years. High concentration product and recycling soils became the low radioactivity concentrations by applying the reduction process, and the concentration of radioactive Cs final disposal concept has been shown. Chemical process combining the leaching of radioactive Cs by acid washing and adsorption recovery reduction processing options as in this study, we propose. In this process, elute radioactive Cs in soils polluted by inorganic acids, reduce the level of radioactivity. Also, the radioactive Cs of cleaning wastewater to recovery adsorption by Prussian blue. To investigate the feasibility of the process using the contaminated soil in this study were collected from three sites in Fukushima Prefecture (A, B and C), basic data obtained.2M(M=mol/dm3) HCl、HNO3、H2SO4を用いて50℃における洗浄時間(1,3,5,7時間)の影響を検討した結果、土壌AとBはいずれの酸を用いても、除染率は時間と共に増加し、H2SO4を用いた場合5時間以上処理すると、除染率の増加は緩やかになった。土壌Cについては、50℃ではH2SO4のみ除染効果がみられたが、他の土壌と比べると、除染率は非常に低い値となった。ただし、7時間以上処理を継続すると、除染率は更に増加する可能性があると推察する。また、処理温度(25,50,80,95℃)の影響を検討した結果、いずれの酸を用いても除染率は温度と共に増加した。土壌A及びBは80℃までの処理温度では、H2SO4による除染効果が高く、95℃ではHClの方が除染効果は高くなった。土壌Cは、25℃で処理すると除染効果はほとんど見られず、50℃以上の処理温度では、H2SO4による除染効果が最も高かった。土壌AとBは95℃のHClを用いて5時間処理すると、除染率はそれぞれ72と88%となった。また、土壌Cは、95℃のH2SO4で5時間処理すると除染率は48%となった。この結果から、各土壌の残留放射能濃度(134Csと137Csの合計)はそれぞれ、33.4 kBq/kg (土壌A), 8.9 kBq/kg(土壌B)、17.1 kBq/kg(土壌C)と見積もられた。残留放射能濃度の高い土壌Aを用いて、繰り返し洗浄した結果、95℃のHClで2回洗浄すると、除染率は83%に到達し、残留放射能濃度は20.4 kBq/kgとなる。従って、中間貯蔵期間による減衰を考慮すると、30年後の放射能濃度は約8 kBq/kgになると考えられる。洗浄により発生した酸廃液中には土壌から溶出したFe(Ⅲ)が溶存する。そこに、K4[Fe(CN)6]を添加し、プルシアンブルーを生成させて、放射性Csを吸着回収した。その結果、いずれの酸廃液においても放射能濃度は排水濃度限度以下となり、放射性セシウムを高放射能濃度の沈殿物として回収できることが分かった。

結果 (英語) 2:

A large amount of contaminated soil generated by first power plant accident in Fukushima is final disposal through an intermediate storage of 30 years. At that time, is recycled to the soil in the low radioactive concentration by applying a volume reduction process, are shown idea to final disposal a high concentration product radioactive Cs is concentrated. In this study, as one option for volume reduction process, we propose a chemical treatment process combining eluted with the adsorption recovery of radioactive Cs by acid washing. In this process, the eluted radioactive Cs in an inorganic acid contaminated soil, to reduce the radioactivity concentration. In addition, radioactive Cs of cleaning liquid waste, adsorbed recovered by Prussian blue. In this study, contaminated soil collected from three locations in Fukushima prefecture (A, B and C), was used to obtain the basic data to examine the feasibility of the process.
2M (M = mol / dm3) HCl, HNO3, the result of examining the effect of cleaning time at 50 ℃ (1,3,5,7 hours) using H2SO4, and the soil A and B using any acid decontamination rate is increased with time, can be treated for 5 hours or more when using H2SO4, an increase in the decontamination rate was moderate. For soil C, but decontamination effect only at 50 ℃ H2SO4 was observed, compared to other soil decontamination rate was very low. However, the process continues over 7 hours, and assumed the decontamination rate is likely to further increase. As a result of examining the effect of processing temperature (25,50,80,95 ℃), decontamination rate using any of the acid increased with temperature. In the processing temperature of up to soil A and B is 80 ℃, decontamination effect of H2SO4 is high, decontamination effect is more of at 95 ℃ HCl was higher. Soil C is, decontamination effect and treated with 25 ℃ was hardly seen, in 50 ℃ or more of the processing temperature, decontamination effect of H2SO4 was the highest. When soil A and B for 5 hours treated with HCl in 95 ℃, Josome-ritsu became 72 and 88%, respectively. In addition, soil C, the decontamination rate to 5 hours at H2SO4 of 95 ℃ was 48%. From this result, each residual radioactivity concentration of each soil (total of 134Cs and 137Cs) is, 33.4 kBq / kg (soil A), 8.9 kBq / kg (soil B), also 17.1 kBq / kg (soil C) and the estimate was. Using high soil A residual radioactivity, repeatedly washed result, and washed twice with HCl 95 ℃, Josome-ritsu reaches 83%, the residual activity concentration is 20.4 kBq / kg. Therefore, in consideration of the attenuation due to interim storage period, the activity concentration of 30 years is considered to be about 8 kBq / kg. The acid waste liquid which is generated by washing was eluted from the soil Fe (Ⅲ) is dissolved. There, K4 was added [Fe (CN) 6], is to produce Prussian blue and adsorbing radioactive Cs. As a result, the radioactive concentration in any of the acid waste liquid becomes less effluent concentration limit was found to be recovered radioactive cesium as a precipitate of high radioactivity concentration.

結果 (英語) 3:

The accident at the Fukushima Daiichi plant with a large amount of contaminated soil, 30 years after the interim storage and final disposal. At this time, the recycling of low concentration of radioactivity in soil can be applied to reduce the volume of the concept to final disposal of high concentration of radioactive products enriched with Cs. In the present study, as one of the options, and reduce the volume of the chemical treatment process is proposed by combining adsorption and elution of radioactive Cs by acid cleaning. In this process, theEluting Cs radioactive contaminated soil with inorganic acid to reduce the concentration of radioactivity. The radioactive waste water, washing in Cs collected by Prussian blue. In this study, the soil pollution from three locations in Fukushima Prefecture A, B and C, using the obtained basic data in order to examine the effectiveness of the process. M of 2 mol / dm3. M by HCl, washing time, HNO at 50 ℃ using H 1 2 3 4 SO,, 5, 7 hours. We investigated the effect of the use of acid soil and the A BThe decontamination rate increased with time, and using H 2 SO 4 for more than five hours and the increase of the decontamination rate gradually decreases. On the C soil decontamination effect only 50 ℃ H SO 2, 4, and compared with other soils, the decontamination rate is very low. However, more than seven hours to continue processing, and it is possible to further increase the decontamination rate. In addition, the processing temperature, and studied the effects of 25, 50, 80. Degree. C.,,, 95, by any one of the acid and the decontamination rate increases with the temperature.Soil and A B at the processing temperature of 80 ℃ and high decontamination effect of 2, 4 H SO 95 ℃ for HCl decontamination effect is increased. Soil C at 25 ℃ and almost no decontamination effect, the processing temperature of 50. Degree. C. or higher, the highest decontamination effect by H SO 2. Soil and A B using HCl 95 ℃ for 5 hours, 72, respectively, and the decontamination rate of 88. In addition, the C soil decontamination rate of 2 H C. for 5 hours and SO 4 to 48. From this result,Residual radioactivity concentration in the soil of a total of Cs 137 and Cs 134, respectively 33.4 kBq / kg soil A Ltd 8.9 kBq kg of B soil and soil C 17.1 kBq / kg) and estimated. Using a high concentration of residual soil A radioactivity, repeatedly washed twice in HCl 95 ℃, cleaning and decontamination rate reached 83%, and the residual radioactivity concentration 20.4 kBq / kg. Therefore, in consideration of the attenuation by the intermediate storage period, the concentration of radioactivity after 30 years is about 8 kBq / kg.Leached from soils by acid washing waste liquid generated in Fe III to be dissolved. There K Fe CN 4 in addition to 6, Prussian blue, adsorption of radioactive Cs. As a result, the concentration of acid waste water in the waste water and the concentration limit, it is found that the sediment concentration and high activity radioactive cesium can be recovered. At