Assessment of radiation exposure outside the radiotherapeutic room during medical accelerator beam emission with the use of TL detectors (radiation exposure outside a LINAC room).

Photon and neutron soft tissue absorbed doses near the entrance door to the medical LINAC treatment room were measured with the use of thermoluminescent detectors LiF:Mg,Cu,P in the anthropomorphic phantom. Two different therapeutic beams (6 and 15 MV) and four treatment techniques were involved in the present study. This allowed one to investigate the contribution of scattered X rays, secondary neutrons and gamma rays to the radiation field. Photon absorbed dose rates 50 cm away from the LINAC room door during emission of 15-MV X rays varied between 4.1×10(-4) and 5.6×10(-4) Gy h(-1), depending on the gantry position and the irradiation field size, whereas in the case of 6-MV therapeutic irradiation these doses are ∼1.5 times lower. In the case of 15-MV beam emission, a mixed radiation field near the bunker door is observed with the photon radiation as the main component, which includes a 33.1 % contribution of the induced gamma radioactivity and ∼2.1 % contribution of the neutron radiation.

Mean annual (222)Rn concentration in homes located in different geological regions of Poland: first approach to whole country area.

The paper presents the results of year-long measurements of radon ((222)Rn) concentration inside 129 buildings in Poland in relation to the geological conditions of their foundation. The authors took into account the division of the country into tectonic units, as well as the lithology of the rocks forming the bedrock of these buildings. As expected, the highest value of mean annual (222)Rn concentration (845 Bq/m(3)) was recorded in a building situated in the area of the Sudetes, while the highest geometric mean (characteristic of the expected log-normal data distribution) was calculated based on measurements from buildings located within the East-European craton, in the area of Mazury-Podlasie monocline, where it reached 231 Bq/m(3). Such results reflect geological conditions - the occurrence of crystalline rocks (especially U- and Ra-enriched granites and orthogneisses) on the surface in the Sudetes, and of young post-glacial sediments containing fragments of Scandinavian crystalline rocks, also enriched with U and Ra, in the area of Mazury-Podlasie monocline. However, the least expected result of the investigations was finding out that, contrary to the hitherto widespread belief, none of the major tectonic units of Poland can be excluded from the list of those containing buildings with mean annual (222)Rn concentration exceeding 200 Bq/m(3). The mean annual concentration of radon for all the buildings were much higher than the mean concentration value (49.1 Bq/m(3)) of indoor radon in Poland quoted so far. These results cast a completely new light on the necessity to perform measurements of radon concentration in residential buildings in Poland, no more with reference to small areas with outcrops of crystalline rocks (especially the Sudetes, being the Polish fragment of the European Variscan belt), but for all the major tectonic units within Poland.

Radon concentrations in groundwaters of the Polish part of the Sudety Mountains (SW Poland).

In the course of researches into radon occurrence in the groundwaters of the Polish part of the Sudety Mountains, conducted in various research centres in Poland, almost 1000 radon concentration determinations have been collected. These results have given the basis for an attempt to characterise the groundwaters of this region with respect to radon content. Radon concentrations oscillated within the range of 0.2-1645 Bq/dm3, with the arithmetic mean at 240.0 Bq/dm3 and the geometric mean at 106.7 Bq/dm3. The largest number of radon concentrations found in the Sudetic groundwaters ranged between ca. 3-6 and 1000 Bq/dm3. The values over 1000 Bq/dm3 can be considered anomalously high. They constitute 3.9% of all the results and occur around six localities within different geological units of the Sudety Mountains. These are shallow circulation, low mineralised groundwaters, which outflow from gneisses and granites. In the face of the fact that from 12.8% to 72.7% (depending on the adopted norm of maximum radon concentration for drinking waters) of the examined waters cannot be drunk directly without removing at least part of the radon, and in the face of the possibility of recognizing as many as 63.5% of the waters as potentially medicinal, extensive research of radon geochemistry in the Sudety Mountains area should be urgently undertaken.