Develop viable replacements for potentially dangerous industrial and medical radiological sources.
Challenges of CNEC Thrust Areas
– Dr. Bill Dunn
RDRS addresses the problem of replacement of dangerous radiological sources. Early in the project, we identified the first challenge problem as follows. Oil well logging tools are used around the world and, typically, contain curie-level Am-Be and Cs-137 sources. Our challenge problem is to find a suitable replacement for these radioisotope sources. The replacement of currently used radioisotope sources in oil well logging tools was chosen as a first objective because the sources are fairly long-lived, exist in thousands of tools used around the world with minimal security, and typically have multi-curie activities. These sources were identified by a National Academy of Sciences report as being “Category 1” dangerous radiological sources. Our approach has been to develop a version of the Monte Carlo Library Least Squares (MCLLS) method that can be used to invert the data from multiple neutron and photon detectors due to a single machine source of neutrons. We chose a D-T generator as the neutron source because its neutrons have high energy and can thus generate high-energy inelastic scatter gamma rays from a number of elements, providing useful information on soil composition. In order to validate the MCLLS model, it was deemed necessary to design and construct a benchmark tool and a test facility. The benchmark tool should be similar to well logging tool designs but as simple as possible, for easy simulation modeling. The test facility is a large enclosure through which an 8-in. pipe is inserted, which acts as a bore-hole. We have completed the design and construction of both the benchmarking tool and the test facility and are beginning the collection of data. As a separate source replacement task, we have identified replacing the hundreds to thousands of curies of Co-60 and Cs-137 radioisotope sources in transportable blood irradiation units with machine sources. Large X-ray tubes and LIINAC-driven sources are possible replacements.