The Study On Purification And Treatment Of Radioactive Waste Water By Membrane Distillation Technology

With the rapid development of our country’s economy, energy problem is becoming more and more serious, so the development of nuclear energy has became an inevitable trend. While nuclear energy solving the energy shortage problem, the radioactive waste water was produced, that must be purified in a timely manner. The technology used to treat the radioactive waste water is "flocculation precipitation-evaporation- ion exchange" process, which has shortcoming of serious secondary pollution and bad purify effect. The "flocculation precipitation-evaporation- ion exchange “process can’t meet the increasing strict processing requirements of the radioactive waste water in nuclear industry, especially in the inland nuclear power station. So new technology used to treat radioactive waste water was needed.This paper studied membrane distillation treat and purify the radioactive waste water, which comes from running or retiring nuclear power plant, nuclear factory. Air gap membrane distillation was employed for the treatment of simulated radioactive wastewater contained only 1g/L Sr2+,and the complex ingredient that mixed Co2+、Sr2+、Na+、Ca2+ with the concentration of 10g/L, respectively. The research results showed that the desalination rates of Sr2+ in the simple ingredient of simulate radioactive wastewater achieved 99.999%, and the decontamination factor of that was more than 105. The desalination rates of Sr2+ and Co2+ in the complex ingredient, which mixed Co2+、Sr2+、Na+、Ca2+,were all nearly 100%, practically, and the decontamination factor of Sr2+ and Co2+ were reached to 1×106 and 1×107, separately. Enhancing the temperature and flow rate of feed can make contribution to increasing the membrane flux effectively. When the temperature of feed was 75℃ and flow rate of feed was 7L/min, the membrane flux of the simple ingredient simulated radioactive wastewater, which contained only 1g/L Sr2+, was 4.15kg/(m2·h). In the same case, the complex ingredient that mixed Co2+、Sr2+、Na+、Ca2+,with concentration of 10g/L, was 3.88 kg/(m2·h).The membrane distillation technology was used to treat and purify the spent fuel reprocessing plant radioactive waste water, which contains several radioactive ions and a mass of TDS. The membrane distillation device treats the radioactive waste water for 95 hours, continuously. As the feed, the α and β activity concentration were 868Bq/L and 5610Bq/L respectively.Theaactivity concentration of all distillate was below 0.2Bq/L, and the β activity concentration was below 22Bq/L,when the temperature of feed was 80℃ and flow rate of feed was 5 L/min, the membrane flux was 7.12Kg/(m2·h).The membrane distillation as a novel technology will play an important role in the treatment of radioactive waste water.