Zaporizhzhia is a nuclear power plant of Ukraine. It has been a focus of concern since Russian forces took control over it. It is the largest power plant in Europe and among the largest in the world.
It is located in south east Ukraine in Enerhodar on the banks of Kakhovka Reservoir on the Dnieper River. It accounts for about 40% of the total electricity generated by all the Ukrainian power plants.
How Reactor design is different from Chernobyl nuclear power plant of Russia:
It has VVER -1000 (water energetic reactors) or (pressurised water reactors) reactors for total power generation capacity of 600 GW.
The reactor complex consist of the reactor vessels in which uranium dioxide fuel rods are immersed in water and control rods inserted at top.
The water is booth coolant and moderator.
Whereas in Chernobyl the coolant and moderators are different. (Light water and nuclear graphite respectively)
One reason why Chernobyl became disaster was because when the reactor was breached the superhot graphite caught the fire when it came in contact with air.
Unlike Chernobyl the VVER-1000 reactors and its power generation units at Zaporizhzhia are placed inside a large air tight container or chamber called containment.
What is risk of Zaporizhzhia?
The principal danger here is that primary circuit water could depressurise as ste. am and escape into the air along with radioactive material and other volatile material. This mixture will contain the isotope Iodine 31which is easily dispersed by winds and accumulates in and damage the Thyroid gland in humans.
When nuclear power plant becomes disconnected from the external power grid this is dangerous because when nuclear reactions are not happening on the reactor the nuclear fuel has to be cooled which means coolant pump needed to operate. If they do not operate then the fuel could become hot enough to melt through reactor bottom where it will contaminate soil, air and water.