The purpose of the Environmental Board is to ensure the functioning of the early warning system of radiation risk.
In the case of serious nuclear and radiological accidents, if radioactive contamination crosses the state borders in the atmosphere, it is important to quickly obtain information of the seriousness of such risk and the characteristics of the spreading of the contamination so that operative decisions can be made, if necessary, to protect the population.
The monitoring network of the early warning system of radiation risk includes 15 automatic radiation monitoring stations which measure the level of gamma radiation in the air in real time across Estonia. As measurement detectors, all monitoring stations use the Geiger-Müller detector which measures the dose rate of total gamma radiation (nSv/h) and the detector based on NaI(Tl) crystal which measures gamma radiation spectrally, allowing to identify radionuclides and differentiate between the dose rates caused by different radionuclides. The most important one of the latter is a component caused by artificial radionuclides which is compared with prescribed alert level. If the radiation level exceeds the alert level, the stations automatically send a notice to the 24/7 on-call team of the Radiation Department who analyse the obtained information and notify other relevant institutions and the population, if necessary.
Everyone can monitor the data of the air radiation level of Estonia and other European countries via the web map of EURDEP (European Radiological Data Exchange Platform).
Until March 2014, the monitoring network included 10 automatic stations of PMS and ALNOR type from Denmark. In April 2014, the existing monitoring network was replaced with 15 new monitoring stations in the frames of the cooperation programme between Estonia and Switzerland (manufacturer: Envinet GmbH).
Automatic radiation monitoring station in Kunda in North Estonia. Photo: Uko Rand
The monitoring network of early warning includes the monitoring of the radioactivity of the atmosphere particles and aerosols which is conducted in three monitoring stations: in Harku, Narva-Jõesuu and Tõravere. In the first two stations, high-power filtering devices with a pumping rate of 900 m3/h are used. Laboratory analysis of the filters allows to discover very low activity concentrations of radionuclides in the air (in the order of µBq/m3). The most important indicator isotope of radioactive contamination of the atmosphere is Cs-137 which is found in the air in a very small amount even now. There is always natural radioisotope Be-7 in the atmosphere. Estonian data on the activity concentrations of Cs-137 and Be-7 in the air can be monitored at the homepage of the Environmental Board.
Air filtering device Snow White JL-900 in Harku (manufacturer: Senya OÜ). Photo: Uko Rand
Warning information on a possible radiation risk may also be obtained via international information exchange systems (for example, International Atomic Energy Agency or the Health Emergency Operations Facility of the European Commission). In order to receive and analyse such information, the Radiation Department of the Environmental Board functions as an international contact point.
In the case of possible accidents in the nuclear power station located in the nearby areas of Estonia, the prognosis model of the atmospheric spread of radioactive contamination ARGOS is implemented which uses real time weather information and allows to model the movement and spread of radioactive contamination in time and assess the radiation doses incurred by people. Based on the results of the modelling, measures can be developed and implemented on time to protect the health of the people.