The Role of Laboratory Analog Experiments in Assessing the Performance of Waste Package Materials

Abstract

DE91 006503There is an immediateneed to begin to validate models that car_'_2_/Iiggl used for assessing the performanceof waste package materials in an unsaturatedrepositoryenvironment. This paper examines available testing informationand testing approachesthat could supportvalidationof models for engineering:barriersystem (EBS) radionucliderelease. The content is presented in the contextof the general methodologythat has been proposed for validatingperformance assessmentmodels [I]. Available experimental observationsare used to test some of the EBS release rate modeling premises. These observationsinclude evidence of fluid film formation on waste glass surfaces in isothermalhumid environments,acceleratedwaste glass reaction rates under repositoryservice conditionsof large glass surfacearea 'towater volume ratio, and mobilizationof radionuclidesas solutesand colloids, lt is concludedthat some importantmodeling premisesmay not be consistentwith availableexperimentalinformation. However, it is also concluded that future laboratorytesting, which simulatesthe integratedwaste package system (i.e., laboratoryanalog testing),is needed to evaluate the significanceof these inconsistencies and to test the system level models. A small-scaleapparatuswhich was developed and tested to examine the feasibilityof laboratoryanalog testing for the unsaturatedYucca Mountain repositoryenvironment is described.