ZAPORIZHZHIA NUCLEAR PLANT

Source: The Indian Express

Context

On Tuesday, a team of officials from the International Atomic Energy Agency (IAEA) arrived in Ukraine to assess the condition of the plant, after Russia agreed to their visit.

Key points

The global attention on the war in Ukraine has remained nervously focused on Zaporizhzhia, an important town in the country's southeast. It is the largest nuclear power plant in Europe.

The Zaporizhzhia nuclear power station has been under Russian control since early March, but an escalation of the conflict in the town this month, including shelling and mortar attacks some of which damaged parts of the nuclear station has raised the spectre of nuclear disaster.

Russia and Ukraine have been accusing each other of attempting to damage the nuclear plant in "false flag" operations.
The plant continues to be operated by its Ukrainian staff, with Russian soldiers standing guard.

Ukraine's nuclear power

Ukraine has four nuclear power stations comprising 15 reactors.
The plant at Zaporizhzhiahas six reactors, which can together produce about 5, 700 MW of electricity.
Nuclear energy caters to about half of Ukraine's power demand.
Russian forces attacked the plant on the night of March 3, early in the invasion and took control of it relatively easily.

Dangerous situation

The sporadic fighting continued over the following months, the situation escalated dangerously in August with increased shelling, which the Russians and Ukrainians blamed on each other.
Buildings inside the nuclear complex were hit, though no significant damage has been reported.
Radiation levels around the site have been stable, meaning there has been no leakage.
The situation is extremely volatile. This is the first time that a nuclear installation has been caught in a military conflict, that one is in operation.
In mid-August, the last remaining external power supply line to the complex was disrupted due to the fighting and the station had to fall back on emergency generators.

External needs of Nuclear plants

Nuclear plants have to depend on external electricity for a variety of needs, including the operation of water pumping systems to keep the reactors cool.
That line was restored but for a few hours, it brought the world to the brink of a major nuclear disaster.
As the fighting continues, the possibility of something going wrong remains open.

Design of reactors

Modern nuclear reactors are built to withstand considerable shock and impact.

They have several layers of reinforced steel and concrete and also elaborate fire security systems.
Most of these reactors can survive earthquakes of magnitude 8 or higher.
They are also designed to shut down automatically when they sense major natural hazards.

Zaporizhzhia reactors

The Zaporizhzhia reactors, built in the 1980s and 1990s are said to be quite safe.
Gunfire or even shelling is unlikely to cause much harm or result in a nuclear accident.
It is unclear how the reactors would face up to powerful bombs or missile attacks.
It is expected that neither of the parties would be so reckless to directly bomb the reactor to trigger a nuclear explosion.
But the possibility of a major accident is still very real.
Buildings and water pools used for storing used and unused nuclear fuel are not as sturdily built as their actors themselves and can suffer significant damage in heavy fighting.

Loss of electricity

A more realistic danger has already visited the Zaporizhzhia station briefly.

Cooling systems are extremely crucial to the safe operations of nuclear reactors, which have to handle temperatures in the range of thousands of degrees Celsius.
To keep water pumping through the reactors, an external power supply is needed.
Nuclear stations have elaborate backup generators as well in case of disruption of power.
But these generators can supply electricity only for a limited time and nuclear reactors, even if they are shut down, can take days, sometimes weeks to cool down.

Fukushima disaster

A non-functional cooling system can lead to the reactor melting or exploding under tremendous heat, resulting in an uncontrolled release of nuclear radiation. This is what happened in the Fukushima disaster of 2011.
The reactors were not damaged by the massive earthquake and tsunami. They automatically shut down their operations, as designed.
But the regular power supply, as well as the backup generators, had failed due to rain, storm and flooding, rendering the cooling system non-functional.

The Fukushima disaster prompted a discussion on installing passive systems that would not be dependent on power supply, not just for cooling but also for other crucial safety features.

An example, in the case of cooling systems, could be a water pumping facility relying on gravity.

The Zaporizhzhia station is reported to have some of these "passive" systems as well, but it is not clear how effective they might be in case of a prolonged power outage.

Human error; rogue action

There is also the possibility of inadvertent, potentially disastrous errors by overworked and stressed-out engineers.

The station is being operated by a skeletal staff, with the Russians having reportedly ordered all non-essential and non-operational employees to stay at home.
Nuclear stations usually allow for some redundancy in their staffing to account for the stressful nature of the job and to ensure very high safety standards.
The Chornobyl disaster of 1986, the worst nuclear accident till now, is understood to have been triggered by a human error.

Other threats

Rogue elements could try to utilise the war situation to steal nuclear material from the site.
Ukraine is a signatory to the Nuclear Non-Proliferation Treaty as a non-nuclear weapons state.
Each of its nuclear facilities is under IAEA safeguards.
Every bit of nuclear material and fuel, every kilogram of uranium and every gram of Plutonium, has to be accounted for and reported.
The region is in chaos and rogue elements can try to use nuclear material to make dirty bombs or to sell it in the illegal international nuclear market.

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