the Chernobyl nuclear disaster, illustrated in fascinating cartographies of the disaster

On April 26, 1986, reactor number 4 of the Chernobyl nuclear power plant, in the former Ukrainian Soviet Socialist Republic, exploded during a low-power safety test. The accident released an estimated amount of radioactive material of 400 times greater than that of the Hiroshima atomic bomb, according to the International Atomic Energy Agency.

The RBMK-1000 reactor involved had no containment structure, so radioisotopes such as iodine-131, cesium-137 or strontium-90 were freely dispersed into the atmosphere for ten days in a row, until they extinguished the graphite fire on May 5. The management of the accident could clearly be improved: the authorities ordered the evacuation of the nearby city of Pripyat 36 hours later and the world found out when Sweden detected radiation at its Forsmark plant on April 28.

Ten years later, independent Ukraine published the Atlas of the Chernobyl Exclusion Zonea set of large-format graphic resources prepared by the state cartographic agency. As explains data journalist Attila Bátorfywas the first serious attempt to map the radioactive impact of the disaster on the soil, air and ecosystems and a large number of scientific professionals from entities such as the Ukrainian Academy of Sciences or other research institutes dependent on the Ministry of Ukraine for the Protection of the Population from the Consequences of the Chernobyl Nuclear Power Plant Accident participated in its preparation.

Now it is available to anyone thanks to the digitized version available on Ecogisstorage. The atlas contains different cartographic blocks. One of the first and essential to understand evolution are the weather maps of europe the days during the active phase of the accident and show what the atmospheric situation was like afterwards, with isobars, atmospheric fronts or wind direction for each day.

This is the basis of everything because without reconstructing how the air circulated those subsequent days it is not possible to interpret other pollution maps. The radioactive cloud followed erratic trajectories conditioned by the weather fronts, which explains why countries such as Sweden, Poland or Austria received significant deposits while closer areas were relatively less affected.

To analyze the meteorological influence on dispersion in Ukraine, different graph formats are used, such as bars, wind speed and direction diagrams, or this one that goes under these lines: the radiological wind rose, which shows the amount of material released in each direction of the mean wind in the atmospheric boundary layer.

Each line on the diagram represents the mean wind direction in the atmospheric boundary layer at a given time, with its date noted, the length indicating the magnitude of the radioactivity released. At first glance something can be seen: The dispersion was neither uniform nor radial.but tremendously asymmetrical. Thus, some fronts dragged pollution northwestward, towards Belarus and Scandinavia, while others diverted it to the south and west of Ukraine.

The effects of the Chernobyl disaster, on maps

Under these lines This is the most important map by far: that of Cesium – 137. Why is it important? Because due to its characteristics, Cs-137 is the radiological tracer par excellence, which allows directly showing the permanent chemical trace of the accident on the territory.

At a scale of 1:200,000, it shows the deposition density of Cesium – 137 in the soil on May 10, 1986, reconstructed in retrospect. The pollution isolines draw a tremendously asymmetrical patch, with an absolute maximum concentrated in the north and northwest. There is also a second important spot in the south, following the course of the Pripyat River. The rest show decreasing levels with distance in a radial manner.

The previous one may be the most striking and without a doubt it is the one that has been most widely disseminated, but the most disturbing in the long term is the map of transport routes in groundwater because it quantifies the long-term risk of water pollution. Cs-137 is easily seen and measured, but strontium-90 moving silently through the aquifers toward the Dnieper, which supplies water to millions of people, is an invisible problem.

This 1:200,000 scale map is the only one in the atlas that attempts to quantify this risk with real flow velocities, showing the probable migration trajectories of radionuclides through the aquifers. The arrows point predominantly to the south and southeast, in the direction of the Dnieper.

The map you see just above also has a scale of 1:200,000 and shows the gamma radiation dose power in μR/h (microroentgen per hour), measured 1 meter from the ground. Yes, the above maps are important to describe the severity of the problem, but the gamma dose rate map is essential for decision making: who can enter the area, for how long and what routes are passable. It was the work tool to access the area because it is the map for evaluate exposure dose of the population and the personnel who worked in the area.

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Cover | Atlas of the Chernobyl Exclusion Zone, Ecogisstorage