Characterization of Remote-Handled Transuranic Waste for the Waste Isolation Pilot Plant: Final Report (2002)

The characterization program described here has been developed for contacthandled transuranic (TRU) waste and applied to date to TRU mixed waste. The methods, equipment, procedures, determination of uncertainty, and other protocols used at DOE sites to perform these characterizations have been approved by the Department of Energy (DOE) Carlsbad Field Office, New Mexico Environment Department (NMED) and EPA. The major procedures are described in the following sections:

Acceptable knowledge (AK) of the origin and composition of the waste must be documented to provide evidence that the waste has a defense origin (by the terms of the Land Withdrawal Act, only defense-related TRU waste may legally be sent to the Waste Isolation Pilot Plant (WIPP) and to provide characterization information on the waste constituents. The DOE Carlsbad Area Office and EPA use the AK documentation to certify each “waste stream” (i.e., waste-generating process), and TRU waste sent to WIPP must come from a certified waste stream.

Most of the TRU waste is heterogeneous in nature and requires no further characterization beyond AK to satisfy the regulatory requirements of Resource Conservation Recovery Act (RCRA). For homogeneous waste a fraction of the waste containers (e.g., 55-gallon drums or standard waste boxes) are cored to extract representative samples that are analyzed for constituents (e.g., volatile and semivolatile organic compounds, toxic metals other hazardous chemicals) regulated by RCRA. Both the AK procedure (for heterogeneous waste) and the sampling and analysis procedure (for homogeneous waste) were proposed by DOE for the terms of operation that would be specified in its RCRA permit. These terms have been accepted by New Mexico, which was delegated authority by EPA to regulate RCRA materials and mixed waste and to issue the RCRA Part B permit in October 1999.

A radiography procedure using X rays, also called real-time radiography, is performed on all waste containers to look for items such as pressurized cans or free-standing liquids that are prohibited from being transported under U.S. Department of Transportation regulations. If any of these items are present in a waste container, the prohibited materials are removed and the contents repackaged. This radiographic examination is also used to confirm the AK characterization information.

A visual examination is performed on a fraction of the waste containers by placing the waste contents into a glovebox to verify the AK and real-time radiography information. DOE proposed that 2 percent of the initial population of containers of each waste stream be visually examined, and if these evaluations resulted in few miscertifications, the percentage of subsequent waste containers to undergo visual examination would be reduced. In October 1999, New Mexico in its RCRA permit stipulated the initial fraction of containers to undergo visual examination to be 11 percent.

The number of curies of each transuranic isotope is determined by radioassay (e.g., gamma scans) to a specified precision and accuracy. The fissile isotope content is assessed using non-destructive assay methods, such as passive-active neutron systems. This information is used to meet the Nuclear Regulatory Commission requirement restricting the amount (several hundred grams) per container of each fissile species to ensure criticality safety.

Headspace gas sampling is carried out on all waste containers for flammable gases (specifically, volatile organic compounds, hydrogen, and methane). This procedure has been proposed as a means of checking on conformity with the U.S. Department of Transportation regulations, such as Title 40 Code of Federal Regulations (CFR) Part 173 and Title 40 CFR Part 177, and U.S. Nuclear Regulatory Commission regulations, such as Title 10 CFR Part 71, that address the transport of flammable and/or gas-generating substances with radioactive materials. DOE has proposed the headspace gas sampling procedure in its application to the U.S. Nuclear Regulatory Commission for a licensing certificate on the transportation package (named the TRansUranic PACkage Transporter, or TRUPACT-II) that is loaded with waste containers for transport by truck to WIPP.