The Mixed Waste Focus Area (MWFA) in conjunction with the Characterization Monitoring and Sensor Technology (CMST) crosscut program identified the need to objectively evaluate the capability of nondestructive waste assay (NDA) technologies. This was done because of a general lack of NDA technology performance data with respect to a representative cross section of waste form configurations comprising the Department of Energy (DOE) contacthandled alpha contaminated [e.g., transuranic (TRU) waste]. The overall objective of the Capability Evaluation Project (CEP) was to establish a known and unbiased NDA data and information base that can be used to support end-user decisions with regards to technology system selection and to supporttechnology development organizations in identifying technology system deficiencies.
The CEP was conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) Radioactive Waste Management Complex (RWMC) from September 1997 through May 1998, which required that all participating technologies be on a mobile platform. The CEP evaluated assay system performance parameters on TRU material quantification contained in 55-gallon type waste containers for five waste NDA technologies. Program participants included Bio-Imaging Research, Inc., (BIR), Canberra Industries,Inc., and the Los Alamos National Laboratory (LANL). The NDA technologies provided by these participants represent those commonly employed at waste management characterization facilities with the exception of the active neutron assay technique. Despite the lack of participation of an active neutron based waste NDA technology, the CEP objective of establishing a capability baseline was not significantly compromised.
The evaluation was performed by presenting project participants a set of wellcharacterizedtest samples in a blind test format. The test samples consisted of surrogate and actual TRU waste containers. Test sample measurement data were acquired from each participant through a protocol that accounted for test sample quality assurance and confidentiality. Results were evaluated per criteria and performance assessment mechanisms founded in the Department of Energy Carlsbad Area Office (DOE-CAO), Quality Assurance Program Plan (QAPP) for the Waste Isolation Pilot Plant (WIPP).
The primary performance parameters evaluated in the CEP were measurement bias and relative precision. The performance of a given NDA technology is a direct function of the attributes represented by the waste matrix configuration. Such attributes include matrix density, matrix elemental composition, radionuclidic composition, radionuclide mass loading, and the spatial variation of these components. Analyzing the manner in which bias and precision vary as a function of test sample attribute and NDA technology provides a foundation for deriving performance capability and limitation statements and determines which waste matrix attributes, or combinations of attributes, are compatible or incompatible with existing technologies.
The data indicate that the NDA systems evaluated have a definite capability to perform assay of contact-handled TRU waste packaged in 55-gallon drums, which exhibit reasonable matrix densities and radionuclide loadings, within the acceptance bounds of the QAPP and Performance Demonstration Program (PDP) criteria. Technologies employed to account for matrix effects on quantitative assay processes appear sufficiently developed for waste matrices exhibiting reasonable densities, e.g., less than 0.6 g/cm3 . Additionally, radioactive material mass loadings comprised of nominal weapons grade plutonium sufficient to yield statistically significant data, within a reasonable measurement period, are within the current technology capability envelope. This indicates that in general, calibration, data acquisition and reduction techniques under such conditions, are adequate with respect to the bias and precision performance quality assurance objectives (QAOs).
Performance with respect to bias and precision parameters and minimum detectable concentration (MDC) criteria for test samples in the vicinity of the 100 nCi/g low-level waste (LLW)/TRU segregation point is questionable. To a certain extent this can be mitigated through the use of longer measurement times. In other instances, there does not appear to be adequate accounting of interferences affecting the MDC, such that increased measurement times leads to diminishing returns.
Finally, the ability to yield acceptable bias and precision performance is, under many circumstances, compromised by the number of complicating attributes inherent in the waste matrix configuration. For instance, when the radionuclidic distribution departs from that associated with nominal weapons grade plutonium, there is reasonable capability to correctly determine the mass of the various nuclides. If this configuration is compounded by a low mass of the primary plutonium isotope of quantitation, the ability to achieve acceptable performance deteriorates. If this configuration is again compounded with a high density matrix, the ability to perform in an acceptable manner is further reduced.
In summary, the CEP achieved the stated end-user objective. The data indicate that the nondestructive waste assay systems evaluated have a definite capability to perform assay of contact-handled TRU waste packaged in 55-gallon drums. There is, however, a performance envelope where this capability exists, an area near the envelope boundaries where it is questionable, and a realm outside the envelope where the technologies do not perform. Therefore, the end user must be aware of this envelope and ensure the appropriate technology is selected. This program provides the end user with waste type specific performance data to assist in the assessment and selection of a given waste NDA technology. Additionally, the CEP afforded the private sector participants the opportunity to evaluate system performance using National Institute of Standards and Technology (NIST) traceable radioactive standards and actual TRU waste. This enabled several participants to make significant enhancements to their respective systems and supported all participants in attaining DOE-CAO certification. Ultimately, the DOE end users will benefit from these enhancements.