On April 26, 1986, one of the reactors at Ukraine’s Chernobyl nuclear power plant exploded during a safety test. The blast blew the reactor’s 1,000-ton lid, ignited fires in the building and caused a spillover of radioactive fuel.

The aftermath is considered the worst nuclear disaster in history: about a million people were exposed to radiation and over 350,000 were displaced from their homes. Thankfully, only about 50 people died due to direct exposure, but thousands of children are believed to have developed thyroid cancer due to the accident.

Experts in nuclear energy fear a similar disaster may occur at the Zaporizhzhia nuclear power plant in Crimea, a peninsula occupied by Russia since March. In recent weeks, shelling near the plant — the largest in Europe — has damaged buildings and equipment and killed a worker. Reports also indicate Russia has staged attacks from and stored military supplies in the plant’s grounds.

“Any potential damage to Zaporizhzhia is suicide,” United Nations Secretary-General Antonio Guterres said earlier this month. Volodymyr Zelenskyy, president of Ukraine, also warned the world is on the “verge of nuclear disaster.” If it comes to it, how bad could a nuclear disaster in Crimea be?

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A tale of two nukes

In some ways, Zaporizhzhia is better prepared than Chernobyl was in 1986. The Chernobyl disaster was caused by a series of reactions triggered by human error, poor safety planning and structural deficiencies.

Consequences may have been mitigated if those overseeing the test and local government officials had reported the spillage quickly. Firefighters arrived swiftly at the scene, but the efforts that helped contain the spill — such as dumping a mixture of sand, clay, boron and other minerals from helicopters — didn’t start until 10 a.m. the next day, nearly 34 hours after the blast. Local officials also waited nearly a day and a half to evacuate residents in the vicinity, which prolonged exposure to radiation. 

The Soviet Union, which Ukraine was part of at the time, was not prepared for a disaster of that magnitude. Containing it required guesswork, experimentation and an exorbitant amount of money and manpower. Six months after the explosion, engineers finished building a massive concrete sarcophagus to contain 200 tons of irradiated and fresh nuclear fuel. In 2019, a new structure was installed to reinforce the aging one. It cost about $2.3 billion and took a decade to build, according to Newsweek.

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Since then, countries have adopted better safety and monitoring standards for nuclear plants. The International Atomic Energy Agency, the U.N.’s watchdog for nuclear energy cooperation, coordinates with member countries to notify in case of a spillage. IAEA also has developed an international response plan for disasters. This plan was part of the reason why, 25 years after the Chernobyl disaster, only a tenth of the radioactive material was released when an earthquake-tsunami combo caused a spillage at the Fukushima Daiichi nuclear power plant in Japan.

Known variable

The situation on the ground in Crimea, however, is vastly different. Zaporizhzhia sits on the Dnieper River, which marks the boundary between Ukrainian and Russian forces. A direct strike on the plant would be disastrous but seems unlikely. A more likely scenario is damage that cuts off power supply — including back-up generators — to the reactors’ cooling systems, which could lead to radiation exposure.

Were a nuclear spillover to happen, Russia and Ukraine will have to cooperate to contain it. So far, however, the two have traded blame over the crisis in Zaporizhzhia. Russia has rejected calls to establish a demilitarized zone around the plant, but it recently approved a visit by a team from IAEA to assess conditions at Zaporizhzhia after weeks of pleading from the U.N. nuclear watchdog, The Associated Press reported.

Ukraine says Russia is playing nuclear blackmail with Zaporizhzhia. Last week, the plant was briefly disconnected from the power grid for the first time since it opened in the mid 1980s. It is not the first time Russia has weaponized natural resources to the detriment of millions of people. Europe, for example, is facing an energy shortage due to rationing of Russian natural gas. In the early weeks of the conflict, a Russian naval blockade prevented tons of grains from reaching hungry people in Africa and the Middle East. 

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But Zaporizhzhia is a much riskier gamble. Ukraine’s Hydrometeorological Institute published a simulation showing that radiation from the power plant could spread to Kyiv — about 270 miles away — and neighboring countries. According to the simulation, radiation would spread west, toward inner Ukraine, which would disrupt Ukraine’s efforts to defend itself and to retake Russian-occupied territory. Fighting also could delay an international response to contain the radiation, prolonging exposure to the environment and people. In a twist of irony, however, the war may help in this regard: the fighting has already displaced most residents of the region.