Characterization of the Radioactive Sludge from the ORNL MVST Waste Tanks

Abstract

Over the last several years most of the sludge and liquid from the Liquid Low-Level Waste (LLLW) tanks at ORNL has been transferred and consolidated in the Melton Valley Storage Tanks (MVST). The contents of the MVST tanks at the time the sludge samples were collected for this report included the original inventory in the MVSTs along with the sludge and liquid from the Bethel Valley Evaporator Service Tanks (BVEST), Old Hydrofracture (OHF) tanks, and the Gunite and Associated Tanks (GAAT). During the summer of 2001 full core samples of sludge were collected from the MVST tanks. The purpose of this sampling campaign was to characterize and validate that the current radiochemical and chemical contents of the MVST sludge, which was needed to meet the contract agreements prior to the transfer of the waste to another DOE contractor for processing. This report only discusses the analytical characterization of the sludge from the MVST waste tanks. The isotopic data presented in this report supports the position that fissile isotopes of uranium ({sup 233}U and {sup 235}U) and plutonium ({sup 239}Pu and {sup 241}Pu) were ''denatured'' as required by the administrative controls stated in the ORNL LLLW waste acceptance criteria (WAC). In general, the MVST sludge was found to be hazardous by RCRA characteristics based on total analysis of chromium, mercury, and lead. Also, the alpha activity due to transuranic isotopes was well above the 100 nCi/g limit for TRU waste. The characteristics of the MVST sludge relative to the WIPP WAC limits for fissile gram equivalent, plutonium equivalent activity, and thermal power from decay heat, were estimated from the data in previous reports and found to be far below the upper boundary for any of the remote-handled transuranic waste (RH-TRU) requirements for disposal of the waste in WIPP. Therefore, the WIPP WAC limits were not evaluated for this set of samples.