In Vivo Calibration Measurements for Mixed Oxide Nuclear Reactor Fuel
Abstract
The introduction of mixed oxide (MOX) nuclear fuel containing enriched uranium, isotopes of plutonium, and americium presents a challenge for monitoring occupational exposure using direct in vivo measurements because photons from (235)U and (241)Am will confound evaluation of plutonium in the lungs. MOX is a unique blend of enriched uranium and plutonium that can be used in place of traditional enriched uranium in commercial pressurized water reactors. The plutonium in MOX fuel may be derived from either surplus weapons-grade plutonium or reprocessed commercial nuclear fuel. Thus, the final isotopic composition of MOX depends upon the origin of the plutonium, how well chemical and radiological impurities are removed from the plutonium prior to fuel fabrication, the time between fuel fabrication and use, and (for spent fuel) the total time of irradiation in the reactor. These factors also will have a significant influence on the risk associated with occupational exposure to MOX and the optimum procedure for detecting MOX in vivo. Calibration of an array of high resolution detectors to perform in vivo measurements for MOX in the lungs was performed using the Lawrence Livermore thoracic phantom and a set of lungs containing a homogeneously distributed mixture of (238)U, (235)U, (241)Am, and (238)Pu to simulate conditions that might arise following inhalation of a typical MOX aerosol. Activity associated with photons from (235)U and (241)Am were easy to quantify. Low energy x-rays associated with plutonium decay were detected with reasonable certainty for a chest wall thickness below 3 cm after applying spectrum deconvolution to remove the interference from higher energy photons associated with (235)U and (241)Am. Analysis must depend upon low-abundant, higher energy plutonium photo peaks whenever chest wall thickness exceeds 3 cm because the low-energy uranium L x-rays are greatly attenuated by overlying muscle tissue in the anterior thorax. (7 tables, 7 fig, 11 re7
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 17, 2003
- Accession Number
- ADA416495
Entities
People
- Daniel A. Shaw
- David Hickman
- Henry Spitz
Organizations
- University of Cincinnati