TBP추출제에 의한 Np의 추출률은 산화제의 첨가 여부에 관계없이 질산 농도 증가에 따라 증가하였다. 산화제가 첨가되지 않은 경우 2M 질산에서 약 12%가 추출되었으며 4M 질산에서는 불균등화 반응에 의거 약 56%가 추출되었다. 그러나 1g/L 의 NH₄VO₃ 산화제가 첨가된 경우는 Np(V)가 Np(VI)로 산화되어 2M 질산에서도 약 75%가 추출되었다. 그리고 Np에 U이 단독으로 첨가된 경우 Np의 추출률은 U농도 증가에 따라 감소하며, 10g/L의 U 경우 약 66.3%가 추출되었다. 반면에 Zr의 경우 Zr의 농도 증가에 따라 88±2%가 추출되어 Zr의 농도에는 거의 영향이 없었으며, Np이 단독으로 존재할 추출률인 75%보다 약 13-15% 정도 증가되는 상승 효과를 보이고 있다. U과 Zr이 함께 공존하고 있는 경우 또한 Zr의 농도에는 거의 영향이 없었으나 U의 농도 증가에 따라 추출률이 감소하였다. U농도가 5g/L 이하에서는 Zr에 의한 상승 효과로 88±2%가 추출된 반면에, U의 농도가 10g/L에서는 Zr에 의한 상승 효과와 U농도 증가에 따른 감소 효과에 의해 82±1%가 추출되었다. 마지막으로 9성분계에서의 Np 및 U의 추출률은 각각 89%, 93%였고 기타 Zr, Fe, Mo, Nd, Y, Cs 및 Sr 등은 약 5% 미만이 추출되었다.

The extraction yields of Np(E_Np) by solvent extraction with tribuyl phospate in n-dodecane(TBP/NDD) increased with concentration of HNO₃ regardless of oxidant. Without oxidant, E_Np was about 12% at 2 M HNO₃ and increased to 56% at 4 M HNO₃ due to the disproportionation of Np(V) to Np(VI) and Np(VI). Adding the NH₄VO₃ of 1 g/L, as a oxidant, E_Np was about 75% at 2M HNO₃. This was attributable to the oxidation of Np(V) to Np(VI). In the presence of U or Zr, E_Np decreased with concentration of U and was about 66.3% at U of 10 g/L. On the other hand, E_Np had no effect with concentration of Zr and was in the range of 88±2%. It was found that E_Np adding Zr was more enhanced about 13-15% than that of Np only. In the presence of both U and Zr, E_Np also had no effect with concentration of Zr and slightly decreased with concentration of U. When U was less than 5 g/L, E_Np was in the range of 88±2% by the synergetic effect of Zr only. At U of 10g/L, however, E_Np was 82±1% by the synergetic effect of Zr and decreasing effect of U. In the 9 components system containing the NH₄VO₃ of 1g/L, the extraction yields of Np and U were about 89% and 93%, respectively, and those of Fe, Mo, Zr, Y, Cs and Sr were below 5%. Therefore, Np and U could be effectively co-separated from the simulated HLW solution by controlling the oxidation state of Np.

Neptunium Oxieation/Reduction Tributyl Phosphate Solvent Extraction

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