| Plenty of radioactive waste water was generated and need to be treated after the disaster of Fukushima Daiichi Nuclear Power Plant.Because of the long half-life?about 30 years?,strong radioactivity and high heat-generating,Cs-137 is one of the nuclides that need to be removed first.In circulating injection cooling system of Fukushima NPP-1,zeolites and ferrocyanides are chosed as the adsorbents to remove Cs.However,a number of secondary solid waste?waste adsorbents?is generated and no appropriate processing method is available.So,it is necessary to develop effective adsorbents to reduce the volumes of waste and study the method to deal with the it in order to realize the final stable disposal of Cs.Silica based ammonium molybdephophate was chosen as the Cs adsorbent in this paper.Then foucusing on the generated secondary waste-silica based cesium molybdephophate,allophane and natrual mordenite?NM?are respectively chosen as the base materials to synthesize the solidified products with the use of pressing-sintering method.Experiments about studying the optimal solidifying method?sintering temperature and duration?,leaching resistence and radiation resistence were conducted.The results implied that the optimal sintering temperature is 1200 oC,the optimal duration is 1 h.With the best solidifying method,Cs immobolizaiton ratio could be reached to 100%,values of hardness and modulus of allophane based solidified products were 0.42 and 9.61 GPa,respectively.As for NM based solidified products,values were 3.57 and38.42 GPa,respectively.Cs was immobilized in the forms of CsAlSi2O6 and Cs4Al4Si4O48 in the allphane based and mordenite based solidified products,respectively.In the study of leaching experiments,results showed that the longer leaching time is,the more leaching ammounts of elements could be obtained.Because of the more serious corrosion,solidified products soaked in HNO3and NaOH solutions gained higher leaching rates.After leaching in DW for16 days,the leaching rates of Cs were 1.2×10-5?0 g/?cm2·day?for allophane based and NM based solidified products,exhibiting a great leaching-resistence property.After radiation with 500 kGy and leaching in DW for 16days at 90 oC,the maximum leaching rates of Cs were 2.5×10-5 and 2.2×10-5 g/?cm2·day?for allophane based and NM based solidified products,respectively.All the results showed that both allophane based and NM based solidified products have good bilities of leaching resistence and radiation resistence.This study can offer a possible method to process the Cs contained secondary solid waste and useful datas. |
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