What We Know About Ukraine’s Shelled Nuclear Plant

(Bloomberg) -- News of what Ukrainian officials said was an unprecedented attack by Russia on a nuclear power plant, the largest in Europe, sent shudders around the world. But a fire that broke out at the Zaporizhzhia site in the early hours of March 4 was eventually contained and the damage was unlikely to result in the kind of devastation seen in the last nuclear disaster on Ukrainian soil, the 1986 meltdown at Chernobyl. 

1. How did the episode start?

Ukraine’s Foreign Minister Dmytro Kuleba wrote on Twitter early Friday that a fire had broken out at the plant in southeastern Ukraine after Russian shelling overnight. One shell hit the plant’s first production unit, which was under maintenance, according to the head of Ukraine’s Energoatom nuclear power utility, Petro Kotin. The facility, near the city of Enerhodar, has six reactors and a total capacity of 5.7 gigawatts, enough to power more than 4 million homes.

2. What was the result?

Kuleba had initially warned that an explosion would be 10 times larger than Chernobyl. Emergency services said later they had extinguished the blaze and there were no casualties. No radiation escaped and the integrity of the reactors wasn’t compromised, said Rafael Mariano Grossi, director general of the International Atomic Energy Agency, the world’s nuclear watchdog. The plant’s second and third units were put into safe “cold mode” and the fourth remained in operation as it was the most distant from the shelling zone, said Kotin. The reactors are “being protected by robust containment structures,” U.S. Energy Secretary Jennifer Granholm said in a statement. 

3. What was the response? 

Grossi said he was gravely concerned by the situation in Ukraine and had offered to meet Russian and Ukrainian representatives to try to reduce nuclear safety risks. The incident drew condemnation from NATO foreign ministers. Lithuanian President Gitanas Nauseda said it was “a crime, nuclear terrorism,” and called for further European Union sanctions against Moscow. Russia’s Defense Ministry said its forces have held the nuclear plant since Feb. 28 and accused Ukraine of a “provocation.”

4. How does the plant compare to Chernobyl?

Unlike Chernobyl, the six reactors at Zaporizhzhia are pressurized water reactors (950 MW VVER-320), built in the early 1980s. They have containment structures around the reactor to stop any release of radiation. “Chernobyl did not have a containment,” said Dale Klein, a former chairman of the U.S. Nuclear Regulatory Commission and a professor at the University of Texas at Austin. Unlike the damaged Fukushima plant in Japan, these VVER reactors have separate water circuits to cool the reactor and to produce steam, according to Tony Irwin, a nuclear power expert and honorary associate professor at Australian National University. They also have emergency core cooling systems and multiple injection systems to prevent a core melt, he said.

5. How strong are the containment structures?

The reactors are protected with thick metal and cement shells -- the head of Ukraine’s nuclear operator has said they are designed to withstand an aircraft crash. “Depending on what type of artillery shells they are firing, it is not likely they will break out the containment buildings,” Klein said. Nuclear plants are equipped with emergency response systems that should shut the reactors once they sense the vibrations from the attack, according to Mark Nelson, managing director of Radiant Energy Fund, which advises non-profits and industry about nuclear energy. Even if those systems were damaged, the meltdown would likely be contained within the facility.

6. What about a meltdown?

If a nuclear fuel rod isn’t properly cooled and is exposed to air, then it can quickly heat up, begin to melt and release radioactive gases, which is the phenomenon known as a meltdown. But as long as there is power -- and backup diesel generators -- to keep the fuel rods cool, then it won’t spiral into a meltdown like the one that occurred in 2011 at Fukushima, which didn’t have electricity for a prolonged period of time following an earthquake and tsunami. “Multiple backup cooling systems are available and operators have been trained to be able to withstand plausible situations that could occur under any abnormal situation,” said Lake Barrett, a former official at the U.S. NRC who was involved with the cleanup after a partial meltdown at the Three Mile Island nuclear power plant in the U.S. in 1979. “If there is no significant military damage to their multiple redundant safety systems, the reactors should remain in a safe stable state.”

7. What are the risks?

If Russian forces knocked out power at any of Ukraine’s 15 active nuclear reactors, and destroyed backup diesel generators, the plant operator may struggle to keep the fuel rods cooled. “My concern is that they hit the diesel storage for the diesel generators, and that will take out one of their backup power systems,” said Klein. If spent nuclear fuel is stored in pools on site, an attack might drain the cooling fluid and cause the fuel to melt, releasing large amounts of radioactivity, James Acton, co-director of the nuclear policy program at the Carnegie Endowment for International Peace, wrote in a note in February. And should fires breach containment structures surrounding pressurized water reactors, there could be a risk of radiation releasing out into the air, said Chris Gadomski, an analyst for BloombergNEF in New York. “If you damage the reactor’s core, you’ll have something that would be very unpleasant and similar in scope to Fukushima.” 

Read More: There are Bigger Atomic Worries Than Chernobyl in Ukraine

8. Why such fear?

There’s never been a military attack on an operating nuclear plant, according to analysts. Nuclear plants house incredibly dangerous radioactive material — even after 10 years of cooling, spent fuel can release 20 times the fatal dose of radiation in one hour. In the Chernobyl accident in Ukraine, then part of the former Soviet Union, 350,000 people had to be evacuated and dozens of workers died of radiation poisoning within weeks. It’s the only accident in the history of commercial nuclear power to cause fatalities from direct radiation exposure, and was the product of a severely flawed Soviet-era reactor design, combined with human error, Gadomski said. More than 30 years later, there are still reports of dangerously high levels of radiation in locally produced milk, mushrooms and wild game. 

The Reference Shelf

• QuickTakes on nuclear power, small reactors, and what’s happening at Fukushima.
• Bloomberg Opinion’s Andreas Kluth writes about two nuclear nightmares from Russia and Tyler Cowen explores why Russia would attack a reactor.
• Updates from the IAEA on the situation in Ukraine.
• BNEF’s Gadomski writes on: “Nuclear Power Assets in the Fog of War.”

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