It appears like a nightmare come true. Throughout a army offensive as a part of Russia’s invasion of Ukraine, hearth broke out at Europe’s largest nuclear energy station, the Zaporizhzhia energy plant within the southern metropolis of Enerhodar.
From what we perceive of the state of affairs, Russian troops have been shelling the world throughout a battle for management of the power, which provides 25% of Ukraine’s electrical energy.
The plant has six giant 950-megawatt reactors, constructed between 1980 and 1986 – crucially to a special design to the infamous and now decommissioned Chernobyl energy station.
The hearth evidently broke out in a multi-storey coaching constructing however has since been reportedly extinguished.
Was there an actual threat of nuclear contamination?
The incident understandably raised the spectre of the 1986 Chernobyl catastrophe. However it’s essential to recollect these are two various kinds of reactor. Chernobyl used RBMK-type reactors, a Soviet design from the Seventies that was by no means constructed within the West due to inherent security flaws.
The Zaporizhzhia energy station options Russian-designed VVER reactors, which use broadly the identical design because the Pressurised Water Reactor (PWR), the preferred reactor design used worldwide and in addition the sort utilized in nuclear-powered submarines.
A PWR has a self-contained main cooling water system to switch warmth from the reactor core to a steam generator. This method is saved pressurised so the water doesn’t boil – therefore its identify. A second, separate water loop transfers the steam produced within the steam generator to the turbine that produces the electrical energy.
One other essential distinction with Chernobyl is the truth that VVER and PWR reactors have an enormous concrete containment across the reactor to cease any radioactive launch. This fully surrounds the reactor and steam turbines, making certain any water that might probably be radioactive is inside the containment.
The containment is often constructed from pre-stressed concrete with a metal liner. In distinction, the Chernobyl-type reactor was bodily very giant, which means an analogous containment to surround that system would have been very costly.
Army motion in radioactive Chernobyl may very well be harmful for individuals and the setting
Moreover the traditional cooling programs, VVER reactors have emergency core cooling programs consisting of 4 “hydroaccumulators” – vessels pressurised with fuel and crammed with water that may be mechanically launched into the reactor to chill it. These are referred to as “passive” programs as a result of they rely solely on fuel strain to inject the water, reasonably than pumps that may require electrical energy.
In addition they have a number of programs that use pumps to inject water into the reactor to forestall a core meltdown if the traditional cooling programs aren’t accessible, as an illustration because of a lack of electrical energy.
If the connection to the grid is misplaced, standby diesel turbines can present electrical provides to important plant. This backup plant has a number of “trains” – similar and unbiased units of plant which can be bodily separated and carry out the identical security perform. For instance, this VVER has three trains of high-pressure water injection and three trains of low-pressure injection.
The 4 trains of passive hydroaccumulators don’t want diesel provides and can nonetheless present the required cooling.
In 1979, one of many PWRs at Three Mile Island within the US state of Pennsylvania suffered a core meltdown, however there was virtually no radioactive launch to the setting due to the concrete containment system.
After the 2011 Fukushima catastrophe in Japan, Ukraine’s nuclear regulator examined the potential of its nuclear energy vegetation to resist excessive occasions so all nuclear vegetation are higher ready to deal with these conditions. This led to the set up of cell diesel-driven pumps that may be linked to the reactor’s cooling system to offer water in an emergency.
Is Fukushima nonetheless protected after the most recent earthquake?
The Zaporizhzhia plant provides 25% of Ukraine’s electrical energy, and Russia presumably wished to realize management of it in order to regulate the electrical energy provide. Regardless of the self-evident recklessness of combating close to a nuclear energy plant, it might not be in Russia’s curiosity to trigger a radioactive launch as a result of this could instantly have an effect on its military personnel within the neighborhood, and in addition probably trigger a radioactive cloud to unfold over western Russia and notably the annexed area of Crimea, simply to the south of the plant.