A Title 40 Code of Federal Regulations Part 191 Evaluation of Buried Transuranic Waste at the Nevada Test Site

摘要

In 1986, 21 m~3 of transuranic (TRU) waste was inadvertently buried in a shallow land burial trench at the Area 5 Radioactive Waste Management Site on the Nevada Test Site (NTS). The U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office is considered five options for management of the buried TRU waste. One option is to leave the waste in-place if the disposal can meet the requirements of Title 40 Code of Federal Regulations (CFR) Part 191, "Environmental Radiation Protection Standard for Management and Disposal of Spent Nuclear Fuel, High-Level, and Transuranic Radioactive Wastes." This paper describes analyses that assess the likelihood that TRU waste in shallow land burial can meet the 40 CFR 191 standards for a geologic repository. The simulated probability of the cumulative release exceeding 1 and 10 times the 40 CFR 191.13 containment requirements is estimated to be 0.009 and less than 0.0001, respectively. The cumulative release is most sensitive to the number of groundwater withdrawal wells drilled through the disposal trench. The mean total effective dose equivalent for a member of the public is estimated to reach a maximum of 0.014 milliSievert (mSv) at 10,000 years, or approximately 10 percent of the 0.15 mSv 40 CFR 191.15 individual protection requirement. The dose is predominantly from inhalation of short-lived Rn-222 progeny in air produced by low-level waste disposed in the same trench. The transuranic radionuclide released in greatest amounts, Pu-239, contributes only 0.4 percent of the dose. The member of public dose is most sensitive to the U-234 inventory and the radon emanation coefficient. Reasonable assurance of compliance with the Subpart C groundwater protection standard is provided by site characterization data and hydrologic processes modeling which support a conclusion of no groundwater pathway within 10,000 years. Limited quantities of transuranic waste in a shallow land burial trench at the NTS can meet the requirements of 40 CFR 191.