Industrial commercial respirator filter as indoor radon monitor

This paper presents a method for measuring indoor radon concentrations using a commercially available air-purifying respirator filter as a component of the radon monitor. The filter used was Survivair’s NIOSH (National Institute for Occupational Health and Safety)-approved 100800 model. The method is based on the diffusion of radon gas into the activated carbon of the filter and the measurement of the radioactive daughters resulting from the radon decay. The photopeaks of the ²¹⁴Bi daughter gamma rays (0.609 MeV) were analyzed with a Hyper-Pure Germanium (HPGe) detector and a multichannel system. A monotonically increasing and very close to linear response relation between the integrated area under the ²¹⁴Bi photopeak and the radon concentration of the activated carbon was found. A well-defined relation held for radon levels ranging from 15 to 4,700 Bq/m³. This procedure results in highly reproducible and reliable measurements of indoor radon levels. Interesting applications include the investigation of radiological accidents involving radon and the retrospective measuring of indoor radon concentrations by analyzing the filters of the respirators worn by personnel working during the relevant period.     

Simplified evaluation of214Bi/238U activity ratios in fossil bones using non-destructive activation analysis

A simple and reliable method has been developed for the evaluation of radioactive disequilibrium state in fossil bones. The fossil bone samples were irradiated with an extremely low neutron fluence, together with a standard pitchblende prevailing the secular equilibrium among the uranium series. The²³⁹Np activity induced from²³⁸U in both samples were adjusted to be gamma-ray spectrometrically nearly equivalent to the naturally occurring radioactivities by controlling the neutron flux and cooling time. Using single gamma-ray spectrometry of the irradiated samples, the determination of²¹⁴Bi/²³⁸U in a fossil bone was carried out by comparing the photopeak ratios of²¹⁴Bi /609 keV/ and²³⁹Np /278 keV/ instead of²³⁸U with the same ratios from the pitchblende standard sample.