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Combustion Aerosols Formed During Burning of Radioactively Contaminated Materials, Experimental Results (NUREG/CR-4736)

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Publication Information
Abstract

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NUREG/CR-4736 (PDF - 1.91 MB)

Publication Information

Manuscript Completed: February 1987
Date Published: March 1987

Prepared by
M. A. Halverson, M. Y. Ballinger, G. W. Dennis

Pacific Northwest Laboratory
Richland, WA 99352

Prepared for
Division -of Fuel Cycle and Material Safety
Office of Nuclear Material Safety and Safeguards
U.S. Nuclear Regulatory Commission
Washington, DC 20555
NRC FIN B2481

Availability Notice

Abstract

Pacific Northwest Laboratory conducted two series of experiments to measure aerosols generated by burning contaminated combustibles. Data from these experiments will replace or expand models currently in FIRIN, a fire compartment computer code that predicts source term releases from fires in nuclear fuel cycle facilities.

Four materials were burned in the combustible solid experiments: polychloroprene (PC), polystyrene (PS), polymethylmethacrylate (PMMA), and cellulose. In two runs a combination of fuels was burned. Contaminant form, configuration, and concentration; heat flux; percent oxygen air flow; and type of ignition were varied in the experiments. The highest releases, up to 4.5 wt% uranium, came from PMMA with powder contaminant. Cellulose burns had the lowest fraction releases, approximately 0.01 wt%. Most of the uranium released from PMMA and PS burns came off during the melting and bubbling preignition, stage before the material burned. Uranium release rates from polychloroprene correlate well with smoke release rates. Cellulose seemed to give off uranium at a steady rate 'throughout the burn. Uranium release rates correlated well with mass loss rate for that material. One particle size distribution was measured for each of the fuels. For cellulosic material, more than 97% of the particles carrying uranium were less than 10 iim. However, only 16% of the particles less than 10 ýim carried uranium for PC. Sizes of radioactive particles from burning contaminated PS and PMMA were between the two extremes.

A mixture of 30% tributyl phosphate in kerosene was burned in the contaminated combustible liquid experiments. The fuel was combined with nitric acid in the following four configurations:

acid/fuel with uranium
acid with fission products/fuel with uranium
acid with fission products and uranium/fuel
acid with fission products and uranium/fuel with uranium.

Weight percent of uranium airborne ranged from 0.2 to 7.1, with the highest releases coming from a burn of pure organic fuel over acid with fission products and uranium. In all configurations, the mass rate of uranium airborne seemed to be proportional to the mass rate of smoke airborne. Fission product analysis failed to provi.de accurate data, so it is not included in this report. One particle size distribution was measured. An aerodynamic mass median diameter of 0.6 pm was calculated for airborne particles containing uranium from burning contaminated combustible liquids.