NORM IN MINING INDUSTRY

Exposure to ionizing radiation is usually treated by members of the general public in Poland as a phenomenon related to nuclear power plants and/or disasters in nuclear installations. The best example was the Polish Atomic Law [1], focused until the early 1990s exclusively on nuclear safety, application of artificial sources of radiation, and nuclear accidents. Lately more and more attention is paid to radiation exposure caused by natural radioisotopes. In the last several years, broad investigations in this field are connected not only with radon exposure in dwellings but also with the radiation hazard at workplaces and contamination of the natural environment caused by non-nuclear industries. It has been reflected in the new Atomic Law [2], prepared by the Polish Parliament to harmonize Polish regulations with European Union standards [3]. Until now, specific information on levels of natural radioactivity in waste materials and by-products created by different branches of Polish industry was scarce. Therefore it is very difficult to assess the influence of natural radionuclides on exposures at workplaces and pollution of the environment. Only in the hard coal mining has the situation been more clearly and better recognized. In this paper we would like to describe the state of the knowledge concerning this problem in Poland. Results of investigations in the exploitation industry will be shown (hard coal mines, copper ore mines, lead and zinc mines and salt mines) as well as data from processing industries (dealing with fertilizers, power generation and production of construction materials). In the first part of the paper, results of measurements of the most important natural radionuclides (226Ra, 228Ra and 40K) in different materials are presented — raw materials, waste and by-products produced or dumped into the natural environment. In the second part, the assessment of the doses for workers exposed to sources of natural radiation in different branches of industry will be done.

NATURAL RADIOACTIVITY OF RAW MATERIALS AND INDUSTRIAL SPOILS

In Table I, the main branches of the minerals exploitation industry in Poland are shown. The annual production of raw materials is about 219 million t [4]. Moreover, roughly 82 million t of solid spoils are dumped onto the surface per year. Additionally, about 2.9 million m3 of wastewater is pumped out daily [5]. The production of phosphate fertilizers is based on imported phosphates (slightly more than 0.5 million t/a). Waste materials generated in the power industry must be also taken into account — about 13 million t/a.

Systematic obligatory measurements enabled the gathering of a broad database of results of concentrations of natural radionuclides in air, water and solid materials, not only in underground galleries but also in the natural environment in the vicinity of mines. The most complete database exists for the hard coal mining industry [7, 8]. Fewer data have been gathered for copper ore mines and lead and zinc mines. The data are shown in Table II, together with results from salt mines and data for waste materials from the oil and gas industry. According to the presented data, in almost all raw materials produced by the Polish mining industry (like metal ores and hard coal), typical concentrations of natural radionuclides are low. Nonetheless, in some cases we observe radium concentrations above 50 Bq/kg, quoted in UNSCEAR reports as the upper limit for the earth’s crust. Quite opposite is the situation of waste products, especially from the mining industry. The Upper Silesian Coal Basin has rather specific geological and mining conditions; therefore inflows of brines with high radium content into underground galleries are numerous. Dewatering of mines (removal of these brines from mines onto the surface and further to rivers) causes contamination of the natural environment in the vicinity of coal mines. Sometimes in these brines not only radium but barium ions are present and then radium co precipitates with barium in the form of highly radioactive scales. Such processes can be observed not only in the underground workings, but also sometimes on the surface, in settling ponds or rivers, mainly in cases when waste waters have been not treated before dumping into rivers. Such contamination of the environment is a potential source of radiation hazard not only for miners but also for the inhabitants of adjacent lands. Similar problems have been found in copper mines and in their vicinity.