Radioecological monitoring of atmospheric air in the vicinity of the rooppur NPP (People's Republic of Bangladesh)

Abstract

The paper presents the experience of conducting integrated radioecological monitoring of surface air in the region where the Ruppur NPP (People's Republic of Bangladesh) is located at the initial stages of the nuclear plant life cycle. The authors developed a monitoring program, a list of the studied parameters, an observation schedule, and instrumentation support. At different distances from the NPP, posts were selected for sampling surface air and atmospheric deposition. Among the controlled parameters, the following were considered: radionuclide composition, including natural (40K, 222Ra, 226Ra, 232Th) and technogenic (54Mn, 60Co, 90Sr, 137Cs) isotopes, dust level. Monitoring studies were conducted in 2014 - 2017: at the background level and the plant construction phase, taking into account the climatic characteristics of the region in different seasons of the year. The results of monitoring observations made it possible to determine the effect of the plant construction on the change in the concentration of dust in the surface air and the absence of a detectable increase in its radionuclide content. The volumetric activity of radioisotopes in air over the entire period of research was at the level of the detection threshold (40K < 3.3·10-2226Ra < 0.01·10-2232Th < 1.4·10-3, 90Sr < 1,3·10-5, 137Cs < 1.5·10-3Bq/m3) and was determined by global deposition. The climate effect on the dust content in the air during the year was also noted - from the minimum values (0.06 mg/m3) in the monsoon period (June- September) to the maximum (0.24 mg/m3) exceeding the established standards (0.15 mg/m3) in the dry period (December). The radon hazard studies of the Ruppur NPP construction site were also carried out. The results of measurements of the radon flux density indicate the safety of the plant's location area in terms of this radionuclide content. In almost all the air samples taken, the radon flux density was lower than 80 Bq/m3, while the permissible limit for residential and public buildings and structures to be commissioned after the plant construction, major repairs or reconstruction is at the level of 100 Bq/m3. The established network of radiation and environmental monitoring of surface atmospheric air will make it possible to register changes in the situation in the Ruppur NPP's location area and to identify the effect of the plant's work on the radioecological situation in this region.