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In 1961, the first network for monitoring radioactivity in the environment was established, in time to cover the period of the most intense nuclear tests conducted by the United States of America and the Soviet Union from 1961 to 1962.

Monitoring environmental contamination

In the 1960s and 1970s, the Slovenian monitoring programme was based mostly on indicator measurements (total beta activity in the samples of air, daily and monthly precipitation, rivers, and drinking water from harvested rainwater and from the water supply network). With regard to specific radionuclides, only Sr-90 in the food chain and Cs-137 in precipitation and food were analysed.

By implementing the high-resolution gamma spectrometry method in the radioactivity monitoring programme, the monitoring focused on specific measurements, i.e. determining the concentrations of particular radionuclides in the environment. This was a leap in data evaluation quality as it made it possible to estimate the exposure of representative persons of the public.

Monitoring the operation of nuclear and radiation facilities in the environment

  • The first nuclear facility in Slovenia was the TRIGA Mark II research reactor, built in 1966 in Brinje.
  • In 1981 the test operation of the Krško Nuclear Power Plant – NEK started, which transitioned to regular operation in 1983.
  • In 1985 the Žirovski vrh Uranium Mine – RUŽV started with the test production of uranium.
  • In 1986 the first facility designed specifically for the storage of radioactive waste from industry and medicine was built.

Each of these facilities requires its own monitoring programme. The programmes share the common features but the scope of monitoring varies considerably from facility to facility, depending on the radioactive emissions and type of emitted radionuclides and on the relevance of transmission routes for radionuclide dispersal in the environment.

The monitoring of environmental radioactivity caused by the Krško Nuclear Power Plant includes the real-time monitoring of gaseous and liquid effluents. The plant constantly releases activation and fission radionuclides (Co-58, Co-60, Mn-54, Fe-55 and Cs-134, Cs-137, Sr-90, Ag-110m respectively), noble gases (Ar-41, Xe-133, Xe-135), and isotopes of iodine (I-131), tritium (H-3) and carbon (C-14). NEK conducts its own monitoring of emitted radioactivity. In 2008, the Nuclear Safety Administration established independent effluent monitoring.

During its operation, the research reactor releases the noble gas Ar-41. Liquid radioactive effluents come from the associated laboratories of the Jožef Stefan Institute in Brinje.

Radioactive effluents from the Central Radioactive Waste Storage only contain the radioactive gas Rn-222 originating from waste containing Ra-226.

While still operational, the former uranium mine and ore processing plant released a lot of radioactivity in the form of natural radionuclides from the uranium decay chain, i.e. Rn-222 into the atmosphere, and U-238, Ra-226 and Pb-210 into surface waters. The environmental monitoring programme has included and still includes primarily the measurements of radon and liquid emision and the aforementioned radionuclides.

Types of monitoring

All measurements of radionuclides in the environment are carried out by authorised service providers with accredited laboratories (the Jožef Stefan Institute and the Institute of Occupational Safety). The nuclear and radiation facilities perform measurements of radioactive effluents in their own laboratories.

Real-time Monitoring of Environmental Radioactivity  

In Slovenia, the first real-time measurements with data transmission started in the beginning of 1990s. Later, the scheme was expanded to include more measurement sites and an improved version of meters, and supplemented with the comprehensive graphical representation of measurements and measurement statistics. A 24/7 preparedness (SNSA’s Duty Officer)  was also introduced at that time.

Following the Chernobyl disaster in 1986, a need arose for field measurements to be conducted in real time (without delay), where the results would immediately be transmitted to a central computer. If the pre-set values were exceeded, an alarm would be set off in the data centre at the Nuclear Safety Administration to alert the person on duty.

Measuring network of permanent sampling sites and laboratory measurements of radioactivity of environmental samples

In the event of an emergency situation, the permanent network must, together with laboratories, ensure the increased frequency of sampling and measurements.

Permanent sampling sites where samples are collected, captured or taken are determined in the monitoring programme. Measuring network locations depend on specific characteristics of the facility monitored (effluents, radionuclides, geographic characteristics of the site). Sampling methods, sample preparation and analytical methods are outlined in the applicable regulation. The required quality of measurements and presentation of results are also regulated. Measurement service providers are authorised by the Nuclear Safety Administration. Their laboratories use accredited measurement techniques.