Development of the Remote-Handled Transuranic Waste Radioassay Data Quality Objectives


An Evaluation of RH-TRU Waste Inventories, Characteristics, Radioassay Methods and Capabilities


ORNL/TM-13362


A. M. Meeks

J. A. Chapman



EXECUTIVE SUMMARY


This report results from a task implemented in the fall of 1996 to assist the National Transuranic Program Office of the Department of Energy/ Carlsbad Area Office (DOE/CAO) in establishing data quality objectives (DQOs) for the radioassay of Remote-Handled Transuranic (RH-TRU) waste. As part of the task a draft report was submitted to DOE/CAO on Jan. 10, 1997. This report is being published as an ORNL Technical Memo to provide a referenceable document, to add information not included as part of the draft report previously submitted to DOE/CAO, and to incorporate comments from the RH-TRU sites throughout the complex.

The DQO process is a methodical, seven-step approach for balancing decision uncertainty with available resources [EPA-1, DOE-EM-1]. Consistent with the DQO process, this report identifies regulatory drivers and practical issues of RH-TRU management; consolidates site-specific information on current RH-TRU management practices and plans, particularly as they apply to the radioassay of transuranic radionuclides; discusses the use of process knowledge and its role in RH-TRU radioassay; identifies previous, existing, and near-existing capabilities for radioassay; and proposes development needs that will allow for the final development of DQOs and corresponding Quality Assurance Objectives. This report pertains to radioassay issues only.

This report is a compendium of information resulting from many sources, including discussions and visits with knowledgeable personnel at several DOE sites, the review of radioassay data submitted in the Baseline Inventory Report, rev. 3 [CAO-8]; and evaluation of radioanalytical methods used throughout the complex for measuring and reporting radionuclides.

The RH-TRU waste generator sites discussed in this report are: Argonne National Laboratory-West, Los Alamos National Laboratory, Idaho National Engineering and Environmental Laboratory and Oak Ridge National Laboratory. The DOE installations at Hanford and Battelle Columbus are not discussed because of the uncertainty into which their category waste will be managed. Additionally, expert elicitation was sought for regulatory-driven issues related to the WIPP performance assessment and the RH-TRU 72B shipping cask.

The required quality of RH-TRU radioanalytical measurements is driven by two regulatory issues: transportation, and the repository performance assessment (PA). The 72B shipping cask must be approved by the Nuclear Regulatory Commission. The Environmental Protection Agency must be assured that WIPP will be operated in compliance with 40CFR. Of the two drivers, the NRC will most likely play a larger role in the approval process for RH-TRU waste because the impact of RH-TRU waste on the performance assessment is negligible, as reported in the Compliance Certification Application (CCA) for 40CFR191. [CAO-7] DQOs and associated QAOs should be formulated to satisfy two requirements, in order of priority:

Transportation parameters, as delineated in the 72B-cask Safety Analysis Report, shall not be exceeded. In most cases, the most influential parameter is 239Pu fissile gram equivalent (fge); in fewer cases, the influential parameter may be thermal power. In yet other cases, operational constraints (e.g. high dose rates) may actually be the most limiting design parameter.

The relative abundance of radionuclides shall be reported at a sufficient quality level that enables WIPP to a) demonstrate that the PA-modeled, relative isotopic inventory used to originally demonstrate compliance with 40CFR191 [CAO-7] continues to be valid as actual RH-TRU waste is moved into the WIPP facility over time; or b) demonstrate compliance with 40CFR191 via mandatory 5-year re- executions of the PA model using actual reported data. [CAO-1]

Radioassay is accomplished by the resourceful combination of process knowledge, sampling and radiochemical analysis, and bulk measurement by nondestructive assay. For a considerable fraction of RH-TRU waste, process knowledge will play a larger role than for the CH-waste counterpart. For instance, special nuclear material accountability and control and computations of fuel burnup and reactor fission-product inventory will provide the backbone of process knowledge for RH-TRU waste originating from within hot cells. For sludge waste, process knowledge of the chemical and radionuclide content of the waste will provide an envelope for describing waste material composition. Radiochemistry and bulk radioassay must be combined more effectively for RH-waste. Proficiency of non-destructive assay (NDA) on real RH-TRU debris waste has been demonstrated in one case at LANL. NDA proficiency for other real RH waste streams has not been demonstrated and is not well known. On the other hand, proficiency of destructive assay (DA) on aged (8-10 years) RH-TRU waste is well known and not significantly different from CH waste. The primary limitation of RH-TRU waste characterization by DA is sampling, therefore applying rigorous quality assurance objectives to measurements adds little value. Development efforts for RH-TRU NDA are in early stages. Additional efforts are needed to make NDA techniques a useful application for RH-TRU radioassay. DA methods are fairly mature but are not standardized for RH-TRU waste characterization.

DQOs must be formulated with essentially one endpoint in mind: the use of radioassay needs to be performed at a quality level that assures compliance with transportation and waste acceptance criteria. This does not necessarily mean that a radioassay measurement must be made within a few percent, but rather, that when the uncertainty of the radioassay is added to the mean, the resulting value does not exceed an acceptable limit. Inherent in this logic is that the closer a generator packs a waste shipment to the limit, the better his measurement accuracy should be. Otherwise he can choose to manage his waste shipments in a way so as to optimize the process. There is no choice but to develop implementable DQOs that balance risk, cost, and available resources; this balance is termed "risk benefit". For RH- TRU waste, DQOs should be established in such a way as to provide latitude to generators in actually satisfying them. Within this document is a clear description of the regulatory drivers, waste generator inventories and descriptions of the waste and existing and near existing radioassay capabilities. Also included in the document (specifically section 5) are recommendations for continuing the DQO process for RH-TRU waste.

ORNL/TM-13362 in PDF Format