Indoor radon in rural dwellings of the South-Pannonian region.

The results of indoor radon survey in the South-Pannonian Province Vojvodina (Serbia and Montenegro) are presented. The sampling strategy was oriented towards suburban and urban regions in the Province. For the dwellings typical for such regions the geometric mean annual radon activity concentration of 76.1 Bq m(-3) is measured (1000 measurements). This result leads to the annual dose estimate of 4.3 mSv y(-1), which is above the recommended action limit of ICRP. For urban dwellings in Novi Sad (the Province capital), the annual mean value of 54 Bq m(-3) (220 measurements) is obtained. By comparison of these two results it is concluded that radon surveys based on measurements in urban environment may seriously underestimate the radon-related health risk. The elevated radon levels could not be explained by elevated uranium levels of surface soil.

[Importance of studying exposure of the population to radon and its daughters]. / Znacaj istrazivanja izlozenosti stanovnistva radonu i njegovim potomcima.

INTRODUCTION: Radon and thoron are naturally-occurring radioactive gases, which are products of uranium and thorium decay series, respectively. Uranium and thorium occur widely in the environment, in rocks, soil, air, water, building materials, humans, etc. Radon daughters in the air are predominantly attached to aerosols. A minor part, normally less than 10%, occurs as unattached atoms or ions. The relative distribution of attached daughters in indoor air and equilibrium factor depend on many variables, such as the decay constant, the concentration and size distribution of aerosols and ventilation rates. Increased ventilation decreases the concentration of radon and daughters in the air. OCCURRENCE: Concentration of radon, thoron and their decay products in the air indoors, in mines or houses, is higher than outdoors. In houses, the level of radon daughters may be enhanced by radon from radium rich building materials, landfill, soil and bedrock under the house, radon rich water and by poor ventilation. CONCLUSION: In recent years, several evaluations of human health risks and estimations have been made in regard to the dose-response relationship and lung cancer risk attributable to inhaled radon daughters. Inhalation of radon and thoron daughters leads to deposition in the human respiratory tract and consequent irradiation. Deposition depends on various factors, such as the size distribution of aerosols to which the daughter products of radon are attached, and fraction of unattached daughters. On average, the dose to the basal cell layer in the lung is about 5 to 8 times higher than the dose in the pulmonary region.

115In as a probe for the characterization of therapy bremsstrahlung beams and the detection of photoneutrons.

Variation of the photoactivation rate across radiation fields of three different bremsstrahlung beams of two medical accelerators has been measured, making use of the photonuclear reactions in natural indium probes: 115In(y,y')115mIn and 115In(y,n)114mIn. The third nuclear reaction, 115In(n,y)116mIn, was used to detect the presence of neutrons in the photon beam and to estimate the spatial distribution of thermal and fast neutrons in the patient plane as a function of collimator opening.

Evaluation of bremsstrahlung spectra generated by a 4-MeV linear accelerator.

A modified method for the evaluation of bremsstrahlung spectra on the basis of transmission measurements is presented. The method is tested for two 4 MeV therapy accelerators. The calculated spectra are compared with other experimental results and Monte Carlo simulation.