Masters Theses

Date of Award

5-1997

Degree Type

Thesis

Degree Name

Master of Science

Major

Nuclear Engineering

Major Professor

L. F. Miller

Committee Members

Darryl Downing, Peter Groer, Larry Townsend

Abstract

A number of regulatory-based drivers have imposed more rigorous methods to be employed in the characterization of radioactive waste. For Transuranic (TRU) waste, the Waste Isolation Pilot Plant (WIPP) requires, at a minimum, that the waste generator a) provide methods for sampling and analyzing waste streams to establish an acceptable-knowledge baseline, b) develop a recurring sampling plan that will assure that the data quality objectives can be met, and c) calibrate and use nondestructive assay instruments for certifying the waste, by bulk measurement, to the WIPP Waste Acceptance Criteria (WAC). Currently, the entire remote handled transuranic (RH-TRU) waste inventory for ORNL is being generated at the Radiochemical Engineering Development Center (REDC). In an effort to meet the WIPP WAC, Oak Ridge National Laboratory (ORNL) initiated a project in FY 1996 to develop a suitable characterization method for classifying the hot cell solid wastes being generated at REDC. Based on the waste characteristics, REDC wastes can be certified to meet the waste acceptance criteria specified by a designated permanent waste disposal location.

Combinations of acceptable process knowledge, radiochemical analyses, and nondestructive assays (NDA) were used to establish baseline RH-TRU waste characteristics for REDC hot cell wastes. A pilot study was initiated to collect random smear samples of the REDC "process waste" items to be analyzed by conventional radiochemistry methods. The Gamma Assay Segmented Passive (GASP) system was used to measure gamma activity in several typical 3-gallon melted polyethylene buckets collected at this facility. Nonparametric and parametric statistical methods were used to estimate the mean alpha to gamma activity ratios for a typical 3-gallon waste bucket assembled at REDC. The radiochemical results were used in conjunction with NDA data to effectively estimate the TRU and the lower bound (at the 95% confidence interval) activities of isotopes that cannot be easily measured by conventional passive/active neutron interrogation techniques. Additional statistical techniques were used to combine the TRU activities estimated from each of the "easy-to-measure" gamma-emitting radionuclides into a single TRU activity estimate for each waste bucket.

The methods evaluated for this study provide a best estimate for the activities of alpha-emitting radionuclide wastes contained in a typical REDC waste bucket. Completion of this project should result in the development of an improved waste reporting method to assist REDC in meeting the waste acceptance criteria at WIPP or at an alternate disposal site.

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