Reasearch On Buffer/backfill Material Comprehensive Properties Assessment Based On Fuzzy Analytic Hierarchy Process

Deep geological disposal is a way to make high-level radioactive waste to human and environment less harm that throughbuild multiple barrier system which combine natural barrier and engineering barrier.Buffer/backfill material as the last artificial barrier,it will be the most important barrier when other barriers in vain.Bentonite-sand mixtures have been choosen as the ideal buffer/backfill material by many countries.So it is meaningfull to study comprehensive properties of buffer/backfill material.This article based on our research group and predecessor's achievement,studied thermalperformance andpermeability performance of buffer/backfill materialas supplementary.Then introducing Fuzzy Analytic Hierarchy Process to this paper to calculate every factor's weight of buffer/backfill material.And the assessment formula of comprehensive properties is achieved.On this basis,choose several kinds of typical mixturebuffer / backfill materials to evaluate comprehensive performance.Excepting this paper can be useful to mixture buffer / backfill materials.Research achievements can be summarized as follows:(1)The thermal conductivity and thermal diffusivity of mixture buffer /backfill materials increase with the increase of dry density,sand ratios and water content.(2)Thepermeability performance test results show that with mixed sand mixingratio increase permeability coefficient showed a trend of fir st increase and then decrease,10% sanding rate permeabilitycoefficie-nt i s minimum,shows that the best sanding rate is 10%;permeabilitycoeffi cient decreases with the increase of dry density.When maintaindry dens ity between 1.6g/cm3 to 1.8g/cm3,the permeability coefficientcan be bette r meeting therequestabout buffer material in the reposito-ry of high-radioa ctive waste disposal.(3)Introducing Fuzzy Analytic Hierarchy Process to this paper to assess buffer/backfill material comprehensive properties.Achieved the totalsequence of weight: permeability coefficient > thermal conductivity > plastic index> diffusivity> maximum expansion force> compress coefficient>maximum expansion rate> thermal diffusivity.It can be learned that,the weight of permeability coefficient is maximum.So the permeability coefficient of mixtures is the key factor to prevent radionuclide migration.(4)Choose several kinds of typical mixturebuffer / backfill materials to evaluate comprehensive performance.We can learned that 30% sanding rate,B7 AP,B7ZPbuffer / backfill materials comprehensive performance is best,10% sanding rate,B9 AP,B9ZPbuffer / backfill materials comprehensive performance is ranking second,so addition ratio ought to choose between 10%and 30%.