[en] Filtering of ground level air is performed weekly at seven different locations in Sweden: Kiruna, Umeaa, Gaevle, Ursvik, Grindsjoen, Visby and Ljungbyhed. The filters are compressed and the contents of different radionuclides are measured by gamma spectroscopy. Precipitation is also collected at four of the stations: Kiruna, Gaevle, Ursvik and Ljungbyhed, the samples are ashed and the contents of radionuclides measured. The levels of ⁷Be and ¹³⁷Cs in air and deposition are presented for the different stations. Other anthropogenic radionuclides detected, if any, are also presented

[en] Samples of the airborne radioactivity are regularly taken in three places in Sweden. 18 isotopes are studies. The results of mesurements on the weekly samples are published four times a year. (L.E.)

[en] Ge(Li)-detector measurements of radioactive nuclides in ground level air up to mid-year 1975 at three Swedish sampling stations, Ljungbyhed, Grindsjoen and Kiruna, are reported. Ljungbyhed values are given from April 1974, Grindsjoen values from August 1972 and Kiruna values from August 1973. The main source of particulate radioactivity during the period of interest was the Chinese nuclear explosions of March 1972, June 1973 and June 1974. Specific discussions are given for the ⁷Be-, ⁵⁴Mn-, ⁸⁸Y-, ⁹⁵Zr-, ¹⁰³Ru-, ¹⁰⁶Ru-, ¹²⁵Sb-, ¹³¹I-, ¹³⁷Cs-, ¹⁴⁰Ba-, ¹⁴¹Ce-, ¹⁴⁴Ce-and ¹⁵⁵Eu- activities. (author)

[en] The performance of large stationary air samplers at nine different laboratories was tested by employing two transportable high-volume air samplers, which were used in parallel with the stationary sampler at each laboratory for periods lasting between 2 and 6 months. Comparisons were made for ⁷Be at each laboratory and for ¹³⁷Cs and ²¹⁰Pb at some of the laboratories. The last nuclides proved difficult to use for this purpose whereas ⁷Be was very useful. (orig.)

[en] We present weekly ⁷Be (from 1972 to 1995), and weekly/seasonal ¹⁰Be (for 1994) data in surface air from ground level stations in Sweden with a coverage of most of the northern high latitudes (56 deg. - 68 deg. N). Our Be data are regionally representative and reveal seasonal variation and coupling with tropospheric air mass from middle-low latitudes. The Be data also suggests a few percent, and sometimes episodic, incursion of stratospheric air mass. Frequent precipitation depletes the Be isotopes in the air, but cyclone events contribute to enrichments. A strong coherence between the ⁷Be record and short-term (monthly-seasonal) change in solar activity is observed which introduces a new mechanism for driving the amplitude of seasonal variation

[en] The resuspension of radioactive particles has been measured at four different locations in Sweden during the second half year 1986. For Cs-134 and Cs-137, the resuspension was found to be in the order from 4x10^-9 to 3x10^-8 (m^-1) depending on the environment. The highest resuspension value was measured in the town of Stockholm and the lowest value measured in the country above a surface of grass and bare rock. The effect of resuspension is probably depending on local conditions in the order of a few tens of kilometers. Plants, such as coniferous woods, could probably give an essential contribution. Further measurements are required in order to draw more far-reaching conclusions about the mechanisms of resuspension. Measurements on very high volumes of ground level air at eight different locations in Sweden during the second half year 1986 has not revealed one single 'hot' particle. The maximum activity of Ru-106, which could have been present in a collected particle is estimated to 40 Bq and the maximum amount of Ce-144 to 300 Bq. This will not cause any radiation protection problems. Spring farming on dry soils, however, could give rise to high activity particles in the air. A separate investigation of resuspension during farm work has therefore been initiated. (authors)

[en] The fallout over Sweden from the Chernobyl accident was heavier than in most countries outside of the USSR. The contamination in Sweden is also very uneven. There are areas with more than 200 kBq/m² of ¹³⁷Cs while other parts of Sweden have less than 300 Bq/m². This has given a unique possibility to study the behaviour of radioactive material released from a nuclear power accident. This paper report four years of measurements of resuspended radioactive Caesium. It appear that the manner in which the radioactive material was deposited (by wet or dry deposition) is important for how much of the material will be available for resuspension. In areas with wet deposition the resuspension factor is smaller than in areas with dry deposition. But part of this difference is probably due to activity of non-local origin. There is a yearly cycle, with a peak in the spring preceding gradually decreasing resuspension values until a minimum is reached in the fall and winter. Overall, The resuspension factor, defined as the concentration in air (Bq/m³) divided by the totally deposited activity (Bq/m²), varies between 10^-8 and 10^-10m^-1 with the higher values for areas with dry deposition. It has also been possible to deduce the resuspension factor in 1985 for fallout Caesium from atmospheric nuclear weapons tests. It was found to be ≅ 3x10^-10m^-1. (au)

[en] The airborne radioactive material from the Chernobyl accident reached Sweden on 27 April 1986. In situ measurements were started by the Nuclear Detection Group of the National Defence Research Establishment (FOA 212) on 28 April 1986. Two high-resolution gamma-spectrometric systems were available for the project and it was decided to use one for mobile measurements in order to cove the affected part of Sweden whereas the other was used to follow the rate of change at one location in the Stockholm area. The radioactive deposition in Sweden mainly occurred in two periods, the first from 27th to 29th of April and the second from the 7th to 10th of May. In the first period the most affected regions were the eastern and central parts of Sweden, in particular the wet-deposition area along the coast of the Gulf of Bothnia and westwards to the mountain regions in Northern Sweden. During the second period, the deposition levels were much lower and mainly affecting the Southern and Southwestern parts of Sweden. Some results of the in situ and soil gamma measurements have been reported earlier (Edvarson 1989, 1991). In this report the results from measurement in the years 1986 to 1988 are reported. (au)

[en] The collective committed dose to the Swedish population from the Chernobyl accident has been estimated from a large number of measurements of radionuclides in air and on the ground. The calculation is, besides a number of theoretical assumptions, based on three types of measurements carried out during the first year after the accident : particulate air activity from six high volume air filter sampling stations; in situ high resolution gamma spectrometry at selected sites representing the different fallout compositions; gamma spectrometry of total Sweden by aircraft carried sodium-iodine spectrometer. The collective committed dose to the Swedish population has been estimated between 4000 and 6000 man Sv, foodstuffs excluded. Around 20% of the collective dose is received during the first year. The contribution to the collective dose commitment from inhalation and external cloud radiation is small. The collective dose commitment is dominated by the ground deposited cesium-134 and cesium-137 isotopes. In wet deposition areas up to 80% of the dose equivalent during the first year is due to cesium isotopes. In dry deposition areas the relative composition of radionuclides is different from the wet deposition areas and the cesium contribution is lower. The average dose commitment to the Swedish population is around 0.1 to 0.5 mSv during the first year and 0.7 to 4.0 mSv during the first 50 years. The dose commitment from Chernobyl can be compared with the dose commitment from ground deposited cesium fallout from nuclear atmospheric tests during the next 50 year period. The fallout dose is 0.26 mSv, which corresponds to a collective dose of 2170 man Sv in Sweden

[en] The National Defence Research Institute runs a network for continuous sampling of radioactivity in ground level air and in precipitation in Sweden and performs high altitude air sampling by means of aircraft from the Royal Swedish Air Force. The present report describes the revised surveillance program in effect since January 1 1976, discusses the preparation, measuring and analysis procedures and gives the results of most measurements made on samples collected between mid-year 1975 and mid-year 1977. This includes results and discussions on four-week samples of ground level air and deposition collected at seven locations in Sweden and weekly samples of ground level air collected at Kiruna, Grindsjoen (near Stockholm) and Ljungbyhed. All high-altitude samples collected during the two years have been analysed and reported on, even from times when no fresh activity was detected. The period covers three atmospheric nuclear explosion tests performed by The People's Republic of China, a low-yield test on January 23 1976, a medium range yield test on September 26 1976 and a high-yield test on November 17 1976. These three tests are discussed in terms of such factors as the atmospheric behaviour of the debris cloud, fractionation and particle properties of the debris and of neutron activation products detected. One strong sample collected nine days after the November 17 1976 thermonuclear explosion was measured extensively during more than a year and was used to construct a mass-yield curve which is compared with mass-yield curves for different monoenergetic neutrons incident on ²³⁸U. On some occasions activities were detected that did not derive from any known nuclear explosions test. This is discussed in the last chapter, parts of which have been published elsewhere but which is included here to give a full account of the two years covered by this report. (author)