7/6/2023 0 Comments Reactor meltdown earthquakeThe remains of the damaged reactor lie buried under a concrete “sarcophagus,” which was built in the aftermath of the disaster and is now surrounded by the New Safe Containment facility, built in 2016. While it’s been 36 years since the Chernobyl disaster, the Russian seizure of the defunct facility still poses unique challenges and risks, Lyman says. Ukraine gets most of its nuclear fuel from Russia, but over the past few years, the country also made agreements to acquire fuel from Pittsburgh-based Westinghouse Electric, making it less dependent on Russian supplies. Nuclear plants never keep new fuel onsite they need to plan a brief shutdown for when the fuel arrives. Refueling Ukraine’s reactors could also be challenging. Older reactors, like most of those in Ukraine, need constant surveillance for that reason, Rosner says. That’s usually made of steel, but after many years of neutron bombardment, the steel becomes brittle and can crack. (In the US, plant operators can often get their license extended for another 20 years, following inspections and any necessary maintenance.) When considering a plant’s safety risks, the critical thing to pay attention to is a reactor’s containment vessel, which contains the nuclear fuel. In particular, the Rivne reactors northwest of Kyiv are close to or past the typical 40-year age limit. Most were built in the 1980s, dating back to the Soviet era the only reactors the country has closed are Chernobyl’s. It doesn’t help that Ukraine’s nuclear plants are getting old, Rosner says. With the reactors no longer able to run their coolant pumps, much of the uncovered nuclear fuel then melted. Some backup battery power remained, but eventually that ran out too. Then the subsequent tsunami knocked out emergency diesel generators. He recalls the 2011 Fukushima Daiichi disaster in Japan, when the reactors there were cut off from the electric grid by a 9.0-magnitude earthquake offshore. “If the cooling system doesn’t work, that is a prescription for disaster,” says Bob Rosner, a physicist at the University of Chicago and former chair of the Bulletin of the Atomic Scientists’ Science and Security Board. But while the newer water reactors are safer, risks remain if plant operators can’t keep the coolant system going, since water heated by the fuel rods needs to be replaced by cool water. Now, in the Ukraine and elsewhere, most nuclear plants have “pressurized water reactors,” which use water rather than graphite. After the catastrophe, that design was phased out worldwide. ![]() But graphite burns, and when the graphite began to smolder, it helped spread radioactive material into the air. The Chernobyl plant, known as a “first-generation” reactor, used graphite as a “moderator,” to slow neutrons down and facilitate fission chain reactions. The risk of such an incident remains very low, Acton wrote, but in war, “the unimaginable becomes entirely conceivable.” In wartime, the arrival of those things is not guaranteed. ![]() In peaceful times, that window should be enough time for the grid to come back online, or a fire crew to arrive, or at least for a resupply of diesel to run emergency generators. Ordinarily, if the power goes out and the reactors need to be powered down, there are backup systems to keep the power plant cool-the IAEA recommends 72 hours of fuel, Acton noted in an email to WIRED. In one scenario, a Russian attack on Ukraine’s power systems disconnects the nuclear plant from the grid, and then a safety incident, like a fire, occurs. On Twitter, Acton noted the increased risks of “common mode” failure, where both primary and backup systems simultaneously fail. While experts believe the Russian military would not deliberately target a nuclear plant, a potentially disastrous mistake-one that could harm millions of Ukranians and also neighboring Russians-is not impossible. They also risk being damaged by a stray missile or artillery shell, especially if the invasion drags on. Ukraine’s aging power plants, packed with reactors, cooling systems, turbines, and other key components, require careful maintenance and monitoring that can be disrupted during wartime. But as the fighting continues, there are perhaps bigger nuclear risks emanating from Ukraine: the many active reactors spread elsewhere across the country. Soil and water remain poisoned by radioactive contaminants, and nuclear material is still being cleaned up inside a containment structure built over the remains of a damaged reactor. The site of the infamous meltdown in the spring of 1986 is the scene of an ongoing environmental crisis. On Thursday, invading Russian forces seized the Chernobyl nuclear plant in northern Ukraine near the Belarus border.
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