THE PERFORMANCE ASSESSMENT IMPACTS OF DISPOSAL OF HIGHMOISTURE, LOW-LEVEL RADIOACTIVE WASTE AT THE NEVADA TEST SITE

摘要

A panel of independent scientists was convened by the Department of Energy to assessthe performance impacts of disposal of low-level radioactive waste from the FernaldEnvironmental Management Project. This waste stream was involved in a transportationincident in December 1997. A resulting outgrowth of investigations of the transportationincident was the recognition that the waste was transported and disposed in stressfracturedmetal boxes and that some of the waste contained excess moisture (highvolumetric water contents). The panel was charged with determining whether disposal ofthis waste in the Area 5 radioactive waste management site on the Nevada Test Site hasimpacted the conclusions of the completed performance assessment. Three questionswere developed by the panel to assess performance impacts: 1) What are the performanceimpacts of reduced container integrity? 2) What is the impact of reduced containerintegrity on subsidence of waste in the disposal pits? and 3) What are the performanceimpacts of excess moisture? No performance or subsidence impacts were noted fromdisposal of the Fernald waste. The impacts of excess moisture were assessed by modelingthe movement of moisture in the vadose zone, assuming high water contents (“wetwaste”) for various percentages of the waste inventory. No performance impacts werenoted for either the base-case scenario (ambient conditions) or a scenario involvingsubsidence and flooding of the waste cells. The absence of performance impacts results