The Study On Treatment Of Simulated Low-level Radioactive Waste Water By Air-Gap Membrane Distillation Technology

According to the?Eleventh Five-Year Plan of Electricity Developmen?issued by the State in early November 2016,the nuclear power as a representative of clean and efficient energy has been listed as a key development project for the implementation of energy conservation and emission reduction commitments.In addition to the completion of coastal projects,will continue to deepen the provinces of inland nuclear power research and preparatory work.With the development of nuclear power will produce more and more radioactive waste,especially the largest proportion of the largest proportion of low-level radioactive waste,low-level radioactive waste water treatment will make a small contribution to save water resources.The traditional waste treatment process energy consumption,treatment effect is medium,there are secondary pollution and other issues,and gradually can not meet the needs of the development of nuclear industry.Membrane distillation technology with atmospheric pressure,low temperature,clean effect close to 100%and can deal with reverse osmosis concentrated water,etc.,not only to reduce the volume of waste to a smaller volume,save resources,but also for the harsh emission standards of inland nuclear power plant of the better choice,it is necessary to carry out membrane distillation treatment of low-level waste liquid research.The simulated low-level waste liquid was processed by the air-gap membrane distillation unit designed by the research group,and the trace radionuclides in the low-level waste liquid were characterized by stable strontium and cesium ions.The mass concentration of strontium and cesium ions in the waste liquid Level at 100,0.1?g/L,it's the conductivity is 285?s/cm and the pH is 7.The results show that the retention rate of strontium and cesium ions in the mass concentration is above 99.99%and the decontamination factor is above 10⁴,which indicates that the membrane distillation device has a good effect on the micro radionuclide in the low-level waste liquid.It is applied to the treatment of low-level waste liquid in inland nuclear power plants with relatively severe emission standards.The results show that the flow rate and temperature difference will not affect the purification effect of membrane distillation.The intermittent operation is due to the temperature of the temperature of the liquid temperature decline,will lead to salt precipitation on the membrane pollution,it should use the continuous operation of the model.The same membrane distillation apparatus was used to treat the simulated high salinity low-level waste liquid?which contained 0.13 g/L of calcium chloride,0.24 g/L of magnesium chloride hexahydrate,0.42g/L of sodium sulfate,Sodium bicarbonate 0.58 g/L,strontium,cesium ion concentration order is 100?g/L?,the initial conductivity of the waste is 2440?s/cm.The results show that the conductivity of the distillate is kept at about 4?s/cm,the desalination rate is above 99.9%and the desalting coefficient is more than 10³ when the effluent conductivity is condensed to 16534?s/cm.,but with salt continues to increase,the amount of treatment has been in a downward trend,after the final effluent conductivity exceeds 20000?s/cm,the desalination rate drops to 99.7%,the decontamination coefficient decreases to 10²,and the amount of treatment decreases by 55%compared to the initial treatment,indicating that the membrane distillation can concentrate the high salt solution to the supersaturated state,which has a good effect on the supersaturated high salt solution.The increase of the concentration of the solution has little effect on the purification effect of the membrane distillation,but the treatment capacity decreases with the increase of the liquid concentration.Used the MLA test system to analyze morphology and contaminants of the positive and negative surface morphology of the new film and the contaminated membrane,it was found that a large amount of calcium and magnesium sodium salt was covered on the membrane surface,and the membrane hole was blocked and on the opposite side of the contaminated film also found a small amount of salt crystals,the film appears hydrophilic leakage phenomenon;by pickling method decontamination,the amount of treatment has been greatly restored,but the purification effect has not been effectively restored and found for the adhesive membrane components silicone gel in the strength of acidic or alkaline environment will be hydrolyzed,the resulting hydrolyzate on the waste liquid and membrane pollution.