Soil samples from Mojkovac, Montenegro, were analyzed by standard gamma-spectrometry for radioactivity due to 226Ra, 232Th, 40K, and 137Cs. Average activity concentrations have been found to be 28.6, 43.1, 620.8, and 55 Bq/kg, respectively. In order to evaluate the radiation hazard, radium equivalent activity, absorbed dose rate, annual effective dose, external and internal hazard indexes, and the annual gonadal dose equivalent were determined and found to be at an average of 133.79 Bq/kg, 65.18 nGy/h, 79.93 mSv/y, 0.37, 0.45, and 0.46 mSv/y, respectively. With life expectancy taken to be 70 years, a mean lifetime outdoor gamma radiation was calculated as 5.6 mSv, yielding a lifetime cancer risk of 2.8×10-4

Change of ra don con cen tra tions in dwell ings with floor level was stud ied in six multi-story build ings, in four towns of Montenegro with dif fer ent cli mate con di tions. The an nual av erage ra don ac tiv ity con cen tra tions in 35 dwell ings are found to be very low, mostly at a level of 20-30 Bqm-3. Ab sorbed gamma dose rates in these dwell ings are in the range of 14-58 nGyh-1. The low ra don con cen tra tions are a con se quence of a good tight ness of the struc tures in con tact with the ground and a small con tri bu tion of build ing ma te ri als to ra don in doors. A clear gen eral trend of changes in ra don con cen tra tions with floor level is not ob served. In most of the dwell ings on dif fer ent floors in the multi-story build ing ra don con cen tra tion varies very lit tle, mostly within mea sure ment er ror. A small de crease in ra don con cen tra tion is noted be tween the two or three floors clos est to the ground, but only in some of the build ings. There fore, a de crease of in door ra don con cen tra tion with floor level can not be con sid ered as a gen eral char ac ter is tic of multi-story build ings. Al though the sea sonal ra don vari a tions have not been in the fo cus of this study, it was found that the av er age ra don ac tiv ity con cen tra tions in dwell ings of the multi-story build ings are higher in warmer than in cooler half-year pe riod, what is con trary to the gen eral rule for homes in the world and in Montenegro as well.

Detection efficiencies of 226Ra and 232Th decay products, as well as corresponding minimum detectable activities in different modes of counting of the PRIPYAT-2M spectrometer (integral, when all pulses - coincident and non-coincident, are counted; non-coincident, when only non-coincident pulses are counted; coincident, when coincident pulses of multiplicity from 2 to 6 are counted), in energy ranges of 200 keV to 2000 keV and 300 keV to 3000 keV are presented here. It has been shown that the mode of double coincidences is the optimum one for measuring radium and thorium activity. In this mode of counting, the sensitivity of the spectrometer is the highest

After year-long measurements with CR-39 detectors, nationwide radon survey was performed in 953 homes - 0.5% of all permanently inhabited dwellings in Montenegro. Influence of 11 factors (area, climate, type of house, year of construction, basement, foundation slab, number of stories, building materials, window frames, heating and smoking) and 35 their categories on the radon concentrations in 732 ground-floor dwellings was analyzed using descriptive, univariate and multivariate methods. Univariate analysis dropped influence of the two factors - heating and smoking. It reveals that, on average, radon concentrations in ground-floor dwellings differ at 95% confidence level in urban and rural areas, in family houses and apartment buildings, in houses with and without basement, and in dwellings with window frames made of wood and PVC/Al. In Cf climate zone they differ from those in Cs and Df zones. Only two pairs of construction periods differ in mean radon concentrations in dwellings: 1980-1999 with 1900-1944, and with 1964-1979. Houses with one, two or three stories have almost equal average radon levels, which are higher than in buildings with more than three stories. Mean value of radon concentrations in houses made of stone are higher than in houses made of concrete, or bricks, or wood. Multivariate analysis revealed that six of the analyzed factors - area, climate, type of house, presence of basement, number of stories and building materials simultaneously have significant relationships (p < 0.05) with radon concentrations in dwellings on ground floor in Montenegro.