Radon Background Research Articles

A Calibration Range in South-Eastern Australia for Airborne Gamma-Ray Spectrometers

A calibration range is an easily navigable strip of land that is used to measure the response of an airborne spectrometer system to changes in aircraft altitude (height attenuation coefficients), and to sources of known concentration (sensitivity coefficients). This paper describes the selection and assessment of an airborne gamma-ray spectrometric calibration range for southeastern Australia. We review the selection criteria for establishing a calibration range, and present the calibration results for a new calibration range near Albury, New South Wales. Background measurements are made over Lake Hume, which is about 27 km away. The calibration range was flown during a period of particularly low atmospheric radon background and this reduced the errors associated with background estimation and removal. The calibration range has most of the desirable features expected of an ideal calibration range. We are hopeful that with the continued cooperation of the local landowners, this range will become a permanent calibration facility for southeastern Australia.

Multichannel models for the estimation of radon background in airborne gamma‐ray spectrometry

Adequate background correction is a crucial step in processing airborne gamma‐ray spectrometric data because any errors are amplified during subsequent processing procedures. Two multichannel models for the estimation of atmospheric radon background are proposed. The spectral‐ratio method uses the relative heights of uranium (U) series photopeaks to estimate the contribution of atmospheric radon to observed spectra. The full‐spectrum method estimates the atmospheric radon contribution through the weighted least‐squares fitting of potassium (K), U, thorium (Th), and radon component spectra to the observed spectra. Both the spectral‐ratio and full‐spectrum methods are adequately calibrated through the estimation of component spectra from calibration experiments on the ground using radioactive calibration sources and wood to simulate the attenuation of gamma rays by air. The simulated heights used in these calibrations must be mapped onto real heights through calibration flights over an airborne calibration range. The spectral‐ratio method is also adequately calibrated using a heuristic calibration procedure. An iterative minimization method is used to find the optimum values of the calibration constants such that the radon background over suitable calibration lines is best removed.

Radon variations and microearthquakes in Western Syria

Groundwater radon data were recorded at monthly intervals from two selected monitoring sites of the northern extension of the Dead Sea Fault System in western Syria during 1993 and 1994. This set of data was utilized to estimate the basic radon background content and the range of its normal variations in groundwater along the fault zone. The results suggest that the establishment of such range is important when attempting to separate the usual groundwater radon fluctuations from other anomalous or earthquake related values. In addition, the seismic activity in the study region was statistically analyzed, and the completeness of the earthquake catalogue during the given time-window was estimated to be at magnitude M ≥ 3.5.

A Personal Neutron Dosimetry System Based on Etched Track and Automatic Readout by Autoscan 60

An instrument for reading chemically etched CR-39 elements, the Autoscan 60, has become commercially available. Based on this readout system a new personal neutron dosemeter badge has been developed. PN3 detectors (NE Technology) are used with a two step etching process. The radiators are polyethylene (PE), polyethylene with 6 Li and aluminium. In a nuclear reaction of 6 Li with thermal neutrons alpha particles and tritons ( 3 H) are produced. While the range of alpha particles (9 μm) is too short to be detected with a two step etching procedure, tritons (range = 52 μm in CR-39) easily reach the sensitive layer of the detector and increase the response for thermal neutrons to a value determined by the 6 Li concentration in the PE radiator. Aluminium inhibits the production of recoil protons and hence, causes a lower response to fast neutrons as compared to PE. From the ratio of the readings behind PE and Al, spectral information can be derived, especially in accident situations when the track density is high and a radiation field analysis is required. For extremely high track densities a microscope is used for evaluation, since automatic counting by Autoscan 60 saturates at doses above 50 mSv. The system has been tested for reproducibility, linearity, energy dependence up to 66 MeV neutron energy, angular dependence, radon background response and multiple use of CR-39 detectors.

Cancer mortality in low radon spa area.

Recently lower mortality for cancers of all sites was reported among inhabitants in the Misasa spa area, where there is a high radon background. To clarify the effects of radon exposure on cancer mortality, the effects of a hot spring itself on cancer mortality was investigated in the Beppu spa area, which has only a low radon background, and adjacent control areas. For females, the mortalities for cancers of all sites, liver and lung were higher in Beppu than those for all Japan on the basis of the standardized mortality ratio (SMR), while the SMR for all cancers was lower in adjacent areas. For the male inhabitants in hoth areas the cancer mortalities of all sites were not significantly different from those of all Japan. When we directly compared the most typical spa areas in Beppu and an adjacent control area, a Poisson regression analysis did not show that the relative risk of dying from cancer of all sites was decreased in the spa areas. These results are thus consistent with the view that the lower cancer mortality in the Misasa spa area might be related to exposure to low levels of radon.

Cancer Mortality Survey in a Spa Area (Misasa, Japan) with a High Radon Background

The 1952–88 cancer mortality records for inhabitants of the Misasa spa area, Japan, which has a high radon background, and a neighboring control area without any radon spa were analyzed (average outdoor Rn concentration: 26 mBq‐liter−1 in Misasa vs. 11 mBq‐liter−1 in the control area). Standardized mortality ratios (SMRs) for cancers of all sites were significantly lower among the inhabitants of both Misasa (male 0.538; female 0.463) and the control area (male 0.850; female 0.770), than in the whole Japanese population. Poisson regression analysis showed that the relative risks among the inhabitants of Misasa were significantly lower than in the control area for deaths from cancers of all sites (0.67) and stomach cancer (0.59). The relative risk of lung cancer death was also lower (0.55 times) in Misasa than in the control area, although the difference was not statistically significant. These results suggest that the linear no‐threshold hypothesis for radiation risk may not be valid for exposure to low doses of radon.