HANFORD TANK WASTE ORGANIC COMPOUND STABILITY ASSESSMENT AND IN SITU SYNTHESIS EVALUATION IN SUPPORT OF THE PRIVATIZATION REGULATORY DQO

摘要

The 54 million gallons of high-level radioactive waste stored in 177 underground storage tanks atthe Hanford Site are designated under the Resource Conservation and Recovery Act of 1976 andthe Washington Hazardous Waste Management Act of 1976 as listed, characteristic, and criteriawaste. Characterization data are needed for the tank waste to ensure compliant treatment,storage, and disposal of the waste. The Department of Energy and Washington Department ofEcology through a Data Quality Objective (DQO) process have defined characterization needsfor the Hanford Site single-shell tank (SST) and double-shell tank (DST) waste. The DQOprocess included selection of regulated analytes to be measured in the Hanford waste. In theanalyte selection process, each of the regulated compounds was evaluated, in part, with respectto the plausibility of existing in the waste. One of the plausibility decisions addressed thecompound’s chemical stability in the waste environment and the potential for the generation ofregulated compounds through in situ synthesis during waste storage.The technical basis, assumptions, and results of the tank waste stability assessment are discussed.The tank waste properties considered in the stability evaluation are high alkalinity, an oxidizingenvironment, and high levels of radioactivity leading to the radiolysis of organics. The technicalapproach consists of documented reactions of organic compounds as a function of their structureand functionality. Most of the functional groups associated with the regulated compounds areknown to be unstable under tank waste conditions. The general exceptions are some simplesubstitutedaromatic and polycyclic aromatic compounds that resist oxidation and the multiplysubstituted aliphatic and aromatic halides that hydrolyze or dehydrohalogenate slowly under tankwaste conditions.The final list of 125 organic compounds provides initial target analytes for characterization of theHanford DST and SST waste and has been used in early permit preparation activities for the tankwaste treatment facility.