Context

Russia and Ukraine have each accused the other of launching kamikaze drones at the Zaporizhzhia nuclear power plant.

Background

• The nuclear plant was captured in the early stages of the two-year-long war, and despite occasional efforts to reconnect to the Russian energy grid its reactors have gradually been put into shutdown.
• Five out of six are in cold shutdown, where the reactors are running at a temperature below boiling point.

1: Dimension- Risks at Zaporizhzhia nuclear power plant after drone attack

• Constant threat: Fighting a war around a nuclear plant has put nuclear safety and security in constant jeopardy.
• Direct risk from crash: The model of containment structure used in Zaporizhzia "exhibits vulnerabilities to the effects of an aircraft crash" and a fighter jet crashing downwards into the dome, where the structure is thinner, could penetrate it, causing concrete chunks and aircraft engine parts to fall inside.
• Potential target: External power lines essential to cooling nuclear fuel in the reactors are a softer potential target. Cooling fuel even in reactors in cold shutdown is necessary to prevent a nuclear meltdown.
• Risk of explosion: Pressurised water is used to transfer heat away from the reactors even when they are shut down, and pumped water is also used to cool down removed spent nuclear fuel from the reactors. Without enough water, or power to pump the water, the fuel could melt down and the zirconium cladding could release hydrogen, which can explode.

2: Dimension- Threats to dry spent fuel storage facility

• Besides the reactors, there is also a dry spent fuel storage facility at the site for used nuclear fuel assemblies, and spent fuel pools at each reactor site that are used to cool down the used nuclear fuel.
• Release of radioactive isotopes: Without water supply to the pools, the water evaporates and the temperatures increase, risking a fire that could release a number of radioactive isotopes.
  • An emission of hydrogen from a spent fuel pool caused an explosion at reactor 4 in Japan's Fukushima nuclear disasterin 2011.
• Release of radionuclides: A meltdown of the fuel could trigger a fire or explosion that could release a plume of radionuclides into the air which could then spread over a large area.