本文選題：鋯鉿分離 + 氟氯混合鹽體系��； 參考：《安徽工業(yè)大學(xué)》2017年碩士論文

【摘要】：鋯熱中子俘獲面小,是核反應(yīng)堆的重要堆芯結(jié)構(gòu)材料、核燃料包覆材料,與鉿相反。鋯鉿在自然界中一般共生,且鉿在鋯中含量為2%左右,而核級(jí)鋯要求鉿的含量小于0.01%,因此鋯鉿分離十分重要,但兩者化學(xué)性質(zhì)很相似、分離困難。目前鋯鉿分離方法主要分為濕法和火法兩種,工業(yè)上主要采用溶劑萃取法,但流程復(fù)雜,環(huán)境負(fù)擔(dān)重。本文采用熔鹽萃取法分離鋯鉿,具有流程短、效率高的優(yōu)點(diǎn)。主要工作包括母合金的制備、母熔鹽的制備以及鋯與鉿的分離實(shí)驗(yàn)。母合金體系為72.8%Cu-18.2%Sn-8%Zr-1%Hf,母熔鹽體系為5%CuF_2-32%NaCl-63%CaCl2。分離實(shí)驗(yàn)考察了CuF_2/Hf的摩爾比、反應(yīng)溫度、反應(yīng)時(shí)間和鹽中CuF_2含量對(duì)鋯鉿分離效果的影響,探討了較為合適的分離條件,并且與純氯鹽體系的分離結(jié)果進(jìn)行了比較。實(shí)驗(yàn)結(jié)果表明:(1)CuF_2/Hf摩爾比對(duì)分離過(guò)程的影響較為復(fù)雜,總體上Zr損失率γ、Hf去除率α均隨著摩爾比的增大而增大,特別在溫度較低時(shí),但是摩爾比太大會(huì)導(dǎo)致Zr損失率過(guò)大,較合適的摩爾比為4/1;(2)溫度對(duì)分離過(guò)程有較大影響,在905~970℃的范圍內(nèi),隨著溫度的升高,Zr的損失率γ下降,此時(shí)熱力學(xué)因素占主導(dǎo),在1010℃的高溫條件下,Zr的損失率γ有所提高,此時(shí)動(dòng)力學(xué)因素——離子擴(kuò)散占主導(dǎo);Hf去除率α在905~1010℃均維持在一個(gè)較高的水平(97~99.6%);分離系數(shù)β總體上隨溫度升高而增大;(3)時(shí)間的影響:4h是比較合適的反應(yīng)時(shí)間,既能保證高的Hf去除率,也能將Zr的損失控制在較低水平;(4)鹽中CuF_2含量下降,對(duì)Zr-Hf分離效果略有提高,但效果不明顯。(5)總體來(lái)說(shuō),同樣條件下,氟氯混合鹽體系的分離效果要優(yōu)于純氯鹽體系,分離系數(shù)最高可達(dá)79.353和85.200。氟氯混合熔鹽分離鋯鉿的最佳條件為:反應(yīng)溫度1010℃、CuF_2/Hf摩爾比4/1、反應(yīng)時(shí)間4h,此條件下得到的鋯中鉿含量最低,為0.107%。通過(guò)實(shí)驗(yàn)條件的進(jìn)一步優(yōu)化,有望獲得符合要求的核級(jí)鋯。
[Abstract]:Zirconium thermal neutron capture surface is small, and it is an important core structure material of nuclear reactor, nuclear fuel coating material, contrary to hafnium. Zirconium and hafnium are generally symbiotic in nature, and the content of hafnium in zirconium is about 2%, while the nuclear level of zirconium requires that the content of hafnium is less than 0.01. Therefore, the separation of zirconium and hafnium is very important. At present, the separation methods of zirconium and hafnium are mainly wet and pyrotechnic. Solvent extraction is mainly used in industry, but the process is complicated and the environment is heavy. The separation of zirconium and hafnium by molten salt extraction has the advantages of short flow and high efficiency. The main work includes preparation of master alloy, preparation of master molten salt and separation of zirconium and hafnium. The master alloy system is 72.8Cu-18.2and Sn-8Zr-1Hf. the master molten salt system is 5%CuF_2-32%NaCl-63Cl2. The effects of molar ratio of CuF_2/Hf, reaction temperature, reaction time and CuF_2 content in salt on the separation of zirconium and hafnium were investigated. The experimental results show that the effect of 2 / HF molar ratio on the separation process is more complex. In general, the removal rate of Zr, 緯, HF, increases with the increase of molar ratio, especially when the temperature is low, but the molar ratio too large leads to the loss rate of Zr. The suitable molar ratio is 4 / 1 / 2) temperature has a great influence on the separation process. In the range of 905 ~ 970 鈩，

本文編號(hào)：1924500