Radon/Thoron Monitor Developed at New York University Receives Patent


Scientists at the New York University (NYU) School of Medicine have patented a new passive measurement system for determining exposure to radon and thoron that is being implemented at the DOE Fernald, Ohio, site. The system is used for monitor­ing exposures of personnel to the two radioisotopes. The monitors are lightweight badge-sized alpha track detectors that integrate exposures over a period of weeks. They have separate detectors for radon and radon + thoron, allowing deter­mina­tion of exposure to each. This is important as radon is a much longer-lived iso­tope (3.8 days) and its decay products deliver a larger alpha radiation dose to the lungs than does the short-lived thoron (55 seconds). Conventional monitors only measure the total exposure. The inhaled particle size distribution is also measured with a newly developed instrument contained in a rugged 3cm high cylinder that attaches to a standard low flow rate pump. Eight filtration stages inside the particle size detector allow deter­mina­tion of the radon decay product activity and trace the air-borne particles of different sizes. Conventional monitors only measure the total exposure. The particle size technology is used alongside the radon thoron detector. Both systems have been successfully tested at the Fernald site where silos are used to store residual radium from the processing of uranium ores. Information about them was presented at the July 2004 meeting of the Health Physics Society in Washington by the Principal Investigator, Dr Naomi H. Harley of NYU. The research that resulted in the new technology was supported by the Environmental Management Science Program.