Potential benefit of retrospective use of neutron monitors in improving ionising radiation exposure assessment on international flights: issues raised by neutron passive dosimeter measurements and EPCARD simulations during sudden changes in solar activity.

Since air transport became more accessible, more and more people have been exposed to ionising radiation of cosmic origin. Measuring the neutron dose equivalent is a good approximation of total ambient dose equivalent, as neutrons carry about 50 % of the dose at flight altitudes. The aim of our study was to compare our measurements of the neutron component of secondary cosmic radiation dose, taken with passive dosimeters, with the data obtained from a simulation generated by EPCARD software, which is common in assessing flight crew exposure to ionising radiation. We observed deviations (both above and below) from the expected proportion of the neutron component (between 40 and 80 %), which pointed to certain issues with actual passive dosimeter measurement and the EPCARD simulation. The main limitation of the dosimeter are large uncertainties in high energy neutron response, which may result in underestimation of neutron dose equivalent. The main drawback of the software simulation is monthly averaging of solar potential in calculations, which can neglect sporadic high energy events. Since airlines worldwide almost exclusively use software (due to costs and convenience) to estimate the dose received by their crew, it is advisable to retrospectively recalculate the dose taking into account neutron monitor readings when solar activity changes.

Assessing the radiological load on the environment in the middle Danube river basin on the basis of a study of the Kopacki Rit Nature Park, Croatia.

A study of the environmental radioactivity in the Kopacki Rit Nature Park, Croatia, is presented. This wildlife reserve is part of the Middle Danube River Basin, and it is exposed to various pollutants due to a number of human activities in the surroundings, where there is a nuclear power plant and also urban centres and areas of intense agricultural production. Results for the activity concentrations of soil and surface water samples do not indicate any elevated radioactivity level, which is confirmed by on-site measurements of ambient dose rate equivalent. An assessment of the radiological load on the local biota, carried out using the ERICA tool, implies an overall low radiological risk even if conservative values of the risk quotient are used. Therefore, human activities do not have a significant effect on the radiological load on the Kopacki Rit area. A similar conclusion might be made with regard to numerous similar environments in the Middle Danube River Basin.

Current radiological situation in Slavonski Brod, Croatia: is there a reason for concern?

For years, the town of Slavonski Brod in Croatia has been facing serious problems with air pollution, which is usually attributed to an oil refinery across the Sava River in Bosnia and Herzegovina. While the air quality is being monitored rigorously with regard to nonradioactive matter, no attention has been paid to the possibility of a coincidental radioactive pollution. This study is the first to have addressed this issue. We measured ambient dose rate equivalents at 150 sites and found that none exceeded 120 nSv h-1, while the average was 80 nSv h-1. Gamma-ray spectrometry of the collected river water and soil samples did not reveal any unusual radioactivity either. In other words, we have found no evidence of radioactive pollution that would endanger the health of the residents of Slavonski Brod.

Neutron radiation measurements on several international flights.

The earth is continually exposed to cosmic radiation of both solar and galactic origin. High-energy particles interact with the constituents in the atmosphere producing secondary particles that create radiation fields at aircraft altitudes. These secondary particles consist mainly of photons, protons, neutrons, charged and uncharged pions, and muons. The neutron component dominates the hadron cascade at lower altitudes as a result of its longer mean free path. Since air transportation has become more available to a greater number of people, this has led to an increase in the number of persons exposed to ionizing radiation of cosmic origin. This concerns pilots and cabin crews as well as frequent flyers. A neutron component of cosmic radiation was measured using an LR 115/CR-39 track detector associated with a 10B converter foil. The measurement of the neutron dose is a good approximation of the total dose since neutrons carry about 50% of the total ambient dose equivalent at aircraft altitudes. Also, the results of the measurements were compared with the data obtained by EPCARD software simulation. The measured neutron dose rate had a span from 0.36 to 8.83 µSv h(-1) (dose enhancement due to high solar activity in the flight period).

Identification and mapping of radon-prone areas in Croatia-preliminary results for Lika-Senj and the southern part of Karlovac counties.

Long-term indoor radon measurements performed by LR 115 track etched detectors in Croatian homes during 2003-04 showed that the arithmetic means of radon concentrations in Lika-Senj and the southern part of Karlovac counties were three times higher (198 Bq m(-3)) than in houses at national level (68 Bq m(-3)). Recently, indoor radon measurements in randomly selected houses were investigated. The obtained values in these new measurements have confirmed the values obtained 10 y ago (the average radon value in 225 investigated houses in this area is 223 Bq m(-3)). Radon concentrations in soil gas were measured in September and October 2012 and 2013 with the AlphaGUARD measuring system. Areas with both elevated indoor radon levels and radon in soil gas were identified (some micro locations in Korenica, Licko Lesce, Generalski Stol, Slunj and Ogulin) and visually presented in the form of maps using the inverse distance weighting approach.

A neutron track etch detector for electron linear accelerators in radiotherapy.

BACKGROUND: Electron linear accelerators in medical radiotherapy have replaced cobalt and caesium sources of radiation. However, medical accelerators with photon energies over 10 MeV generate undesired fast neutron contamination in a therapeutic X-ray photon beam. Photons with energies above 10 MeV can interact with the atomic nucleus of a high-Z material, of which the target and the head of an accelerator consist, and lead to the neutron ejection. RESULTS AND CONCLUSIONS: Our neutron dosimeter, composed of the LR-115 track etch detector and boron foil BN-1 converter, was calibrated on thermal neutrons generated in the nuclear reactor of the Josef Stefan Institute (Slovenia), and applied to dosimetry of undesirable neutrons in photon radiotherapy by the linear accelerator 15 MV Siemens Mevatron. Having considered a high dependence of a cross-section between neutron and boron on neutron energy, and broad neutron spectrum in a photon beam, as well as outside the entrance door to maze of the Mevatron, we developed a method for determining the effective neutron detector response. A neutron dose rate in the photon beam was measured to be 1.96 Sv/h. Outside the Mevatron room the neutron dose rate was 0.62 µSv/h. PACS: 87.52. Ga; 87.53.St; 29.40.Wk.

Indoor radon and lung cancer: a case-control study.

Lung-cancer risk to the general population from indoor radon remains controversial, although studies of radon exposure have established that radon decay products have been a cause of lung cancer among miners. For the case group of patients, suffering from lung cancer, and the control group distributions of the number of homes with high indoor levels of radon were compared with the log-normal distribution, the empirical frequency distribution of the control group obeyed the theoretical log-normal distribution. Using the ratio of frequencies of the case group to the control groups, or the relative frequencies, an association between the relative frequencies and indoor radon concentrations was found, and a positive correlation coefficient was obtained, thus enabling the rate of lung cancer to be estimated for certain indoor radon concentrations. The significant difference between the mean radon levels for the case sample and the control led to the conclusion that patients with lung cancer lived in homes with radon concentrations which were significantly higher than those of Osijek's inhabitants for the control sample.