Chernobyl

Accident history

The accident occurred on April 26, 1986 *1[5]. On the night of April 26, tests of the turbogenerator in coastdown mode were being conducted at the fourth power unit of the Chernobyl Nuclear Power Plant (checking the possibility of using rotational inertia to power the pumps during an emergency power outage) 5.

• The causes of the accident *are often associated with a combination of factors:
• Design flaws in the RBMK-1000 reactor. *For example, a positive void coefficient of reactivity and the "end effect" (when the emergency protection rods, moving upward, initially increased power instead of braking) 6.
• Personnel errors. *The operators were unable to maintain the reactor power within the specified parameters, and the actions to remove the control rods worsened the situation 6.
• Low level of safety culture *at the facility [8].

At 1:23 am, an uncontrolled increase in power occurred, followed by explosions that completely destroyed the active zone of reactor 1 [5]. There was a powerful release of radioactive substances into the atmosphere 1. The active phase of the release lasted for about 10 days [8].

• Immediate consequences: *

• In the first seconds and hours, two people died (pump operator Valery Khodemchuk and commissioning engineer Vladimir Shashenok) [5].
  *In the following weeks, about 30 more people (mostly firefighters and station employees) died from acute radiation sickness [1].

• Another 134 people suffered from radiation sickness of varying severity [1].
  *The radiation cloud spread radioactive particles far beyond the borders of the USSR, affecting the territories of Ukraine, Belarus, and Russia [1].

• Evacuation and liquidation. *The evacuation of the city of Pripyat and other settlements within a 10 km radius of Station 1 began as early as April 27. Later, the zone was expanded to 30 km [1]. In total, over 115 thousand people were resettled in 1986 [1]. More than 500 thousand people were involved in the liquidation of the consequences - military personnel, firefighters, engineers, scientists ("liquidators") [1]. Their efforts prevented even more terrible scenarios (for example, a meltdown of the core and the melt entering the groundwater) [1].

In May 1986, decontamination work began: buildings and streets were treated, the contaminated soil layer was removed and buried [2]. At the same time, they began to build a concrete sarcophagus ("Shelter") over the fourth power unit - it was completed by November 1986 2. A significant portion of the fuel still remains inside the sarcophagus [2].

The state of the exclusion zone today

Currently, the exclusion zone is an area of ​​\u200b\u200bapproximately 2,600 km² in the north of Ukraine, which is officially closed to permanent residence 1. It includes the north of the Vyshgorod district of the Kiev region (including the station itself, the cities of Chernobyl and Pripyat, the urban-type settlements of Poleskoye and Vilcha) [11]. Entry is possible only with passes and after safety instructions [7].

• What is happening now: *

• Nature is actively recovering. *The absence of humans has given nature a chance to come back. Forests have grown where previously there were only concrete boxes and rusty equipment [10]. Large animals have returned to the zone: brown bears, elk, deer, and lynxes [10]. A well-known example is Przewalski's horses, which were brought in at the end of the 1990s [4].

• Background radiation has decreased *compared to 1986 due to the natural decay of radioisotopes [1]. However, in some places (especially in the forests and swamps adjacent to the station), contamination levels remain elevated [12].

• The infrastructure is deteriorating. *Wooden houses in abandoned villages are slowly deteriorating, and roads are becoming overgrown [1].

• There are exceptions. About 300 squatters live in 11 settlements inside the exclusion zone *—people who have returned without permission and are living in abandoned houses [2].

• The Shelter facility is gradually deteriorating. In 2016, the New Safe Confinement *(NSC) was erected over the old sarcophagus—a giant arch designed to isolate the destroyed reactor from the environment and create conditions for the future dismantling of unstable structures 4.

• An important detail: in Belarus, the Polesie State Radiation and Ecological Reserve 1 was created in 1988 on the most affected lands. It can also be visited on an organized tour [12]. And in Russia, the exclusion zone in certain areas of the Bryansk region ceased to exist on January 1, 2024 [12].

Thus, the exclusion zone is not a dead desert, but a place where nature takes its course, but where strict control is still required due to residual background radiation.