When fighting against the Russian invasion of Ukraine led to power outages in the critical cooling system of the closed Chernobyl nuclear power plant, some feared that spent nuclear fuel would overheat. But nuclear experts say there is no immediate danger because time and physics are on the safe side.
Since the fuel rods have been cooling for more than 20 years, it’s not a situation like the 2011 Fukushima nuclear disaster, or even the original Chernobyl meltdown nearly 36 years ago, several nuclear power experts told The Associated Press.
The International Atomic Energy Agency also said it saw “no critical safety implications” at the site, which was the scene of the world’s worst nuclear accident in April 1986.
WHAT HAPPENED IN CHERNOBYL IN THE LAST DAYS?
Ukraine’s power grid operator Ukrenerho said that all Chernobyl plants have had their power cut and the diesel generators will be fueled for 48 hours. Without electricity, the “parameters of nuclear and radiation safety” could not be controlled, it said.
Ukraine’s Foreign Minister Dmytro Kuleba said the plant, which was occupied by Russian forces when the invasion began on February 24, “has lost all electricity,” and he called on the international community to “urge Russia to stop firing.” and to allow repair units to restore power.”
French government spokesman Gabriel Attal underlined in his phone call with French President Emmanuel Macron on Sunday that Russian leader Vladimir Putin “is committed to ensuring the safety of nuclear facilities in Ukraine”.
WHAT WAS THE BIGGEST FEAR OF THE LAST CRISIS?
The Chernobyl facility, which closed in 2000, has fuel rods containing 230 kilograms (500 pounds) of uranium and they are submerged at least 15 meters (49 feet) in water with an active cooling system, Frank von Hippel said. a Princeton University physicist, co-founder of the Science and Global Security program.
The general concern was that the power outage would cause the cooling system’s backup generators to stop, heating up the radioactive fuel rods and evaporating the water, which also helps with cooling, raising the temperature to 800 degrees Celsius (1,470 degrees Fahrenheit). , and cause a fire.
But that’s “pretty unlikely in the situation because the fuel is so cold,” said Edwin Lyman, director of nuclear energy safety at the Union of Concerned Scientists.
Even the unlikely worst-case scenario would take “weeks to months” for the 2,000 fuel assemblies in Chernobyl’s deep-water basin to cook off, von Hippel added.
Such warming would “progress very slowly, if it ever gets there,” he said, calculating it would take “about 40 days for the pool to dry up.”
Under normal circumstances, cooling fuel rods lose an enormous amount of energy and radioactivity every seven days – by a factor of 10 – said Patrick Regan, a professor of nuclear physics at the University of Surrey.
He said the current scenario is not like the 1986 Chernobyl meltdown or the Fukushima power plant disaster, with fuel rods so fresh and hot “you have to keep water flowing through them.”
Following the Fukushima disaster caused by an earthquake and tsunami, the Ukrainian government commissioned a study to examine the meltdown potential from power failure to rod cooling. The study found that the cooling water would not be able to reach boiling temperature and that the fuel rods would not be exposed to trigger a true meltdown, Lyman said.
THE PHYSICS OF COOLING THE FUEL RODS
When fuel rods are consumed after generating electricity, they still contain a lot of internal radioactivity and are still hot. Internal radioactive decay gives off heat and stays in the fuel rods for tens of thousands of years, so they can get hotter unless something is done to cool them, Regan said.
The sticks are placed in cooling pools or ponds where both water and an active electrically powered system cool them using a heat exchanger pump.
“Once you stop the coolant, once you stop the mechanism for dissipating the heat, it (temperature) will go up,” Regan said.
Eventually, in most plants, the radioactivity and heat drop sufficiently that they could eventually switch from water-cooling to air-cooling.
NO IMMEDIATE DANGER SEEN
The Swedish Radiation Protection Agency estimates that a power outage at Chernobyl will not lead to any radiological emissions in the next few weeks.
“Furthermore, the fuel storage ponds are very deep and it would likely take weeks for the water to boil off, even with the cooling pumps not running. Hopefully this should allow enough time for power to be restored to the cooling systems,” said Mark Wenman, nuclear energy expert at Imperial College London.
The IAEA, the Vienna-based UN nuclear regulatory agency, said it sees no critical safety implications at Chernobyl because there can be “effective heat removal without the need for power supply” from spent nuclear fuel.
Lyman and others said they were more concerned about possible damage to cooling systems and other problems at Ukraine’s four other operating nuclear power plants than at the decommissioned Chernobyl site. In 2017, Chernobyl got a new €2 billion containment system to go over the old sarcophagus.
The post-Fukushima study raised questions about the generation and accumulation of hydrogen gas from the cooling process, which is removed with an electronic system, Lyman said. The concern is that without the venting system, the explosive gas could accumulate more and cause hazards, including sparks, when power is turned back on if it ever goes out.
Another problem is that the lack of electricity means the IAEA’s safety and security surveillance system is blinded, Lyman said.
“It’s not just the cooling of the pools, all the external radiation monitoring systems have been lost,” Lyman said. “The IAEA no longer has cameras.”
He described the overall situation as not good but said it was not an immediate emergency. There are layers of security that help, but the lack of power peels some of those off.
“It limps along with a kind of lower resilience,” Lyman said. “So if something else happens, there’s less wiggle room.”
With experts saying a major radioactive release is weeks to months away, if ever, the biggest consequence of wartime power cuts or attacks on nuclear power plants is fear, said Emma Claire Foley, a policy researcher for the US-Russia nuclear policy .
“People hear ‘Chernobyl’ and think ‘nuclear disaster,'” Foley said. “It’s scary. And it creates a feeling of insecurity.”
Should something bad happen, Belarus, a Russian ally of Ukraine, “would have to be more concerned than anyone else” because of its proximity to the Chernobyl site, said Najmedin Meshkati, a professor of nuclear engineering at the University of Southern California. The Belarusian border is less than 10 miles from Chernobyl, while the Ukrainian capital of Kyiv is about 130 kilometers (80 miles) south of the power plant.
“Belarus took the brunt of the Chernobyl impact” from the radioactive cloud released in 1986, he said, adding that Belarusian President Alexander Lukashenko “should take the lead and ask Mr. Putin to halt military operations around Chernobyl.”
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https://www.local10.com/news/world/2022/03/09/explainer-whats-behind-latest-scare-at-chernobyl-plant/ What is behind the recent horror at the Chernobyl power plant?