Explainer-What are the dangers to Ukraine’s nuclear reactors in conflict By Reuters

By Man Faulconbridge

LONDON (Reuters) – Repeated shelling of the Zaporizhzhia nuclear energy plant in southern Ukraine has raised the potential for a grave accident simply 500 km (300 miles) from the location of the world’s worst nuclear accident, the 1986 Chernobyl catastrophe.

The Worldwide Atomic Vitality Company (IAEA), which has repeatedly expressed considerations over the shelling of the plant, has proposed the institution of a nuclear security and safety safety zone across the plant.

What nuclear materials is at Europe’s largest nuclear energy plant, what are the dangers and why are Russia and Ukraine preventing over it?

WHAT IS IT?

The Zaporizhzhia nuclear energy plant has six Soviet-designed VVER-1000 V-320 water-cooled and water-moderated reactors containing 235, which has a half-life of greater than 700 million years.

Development started in 1980 and its sixth reactor was linked to the grid in 1995. All six reactors are actually in chilly shutdown after reactor No. 6 was shut down on Sept. 12.

A chilly shutdown means the reactor’s temperature is under boiling level however electrical pumps shifting water via the reactor core should nonetheless maintain working to chill the gas.

The plant is not producing electrical energy.

WHAT ARE THE RISKS?

The most important danger is from overheating nuclear gas, which might occur if the ability that drives the cooling methods was minimize. Shelling has repeatedly minimize energy traces.

The plant misplaced its final remaining exterior energy on Oct. 8, leaving it reliant on diesel turbines for greater than a day, the Worldwide Atomic Vitality Company mentioned. The ability line was restored on Oct. 9.

Earlier than the conflict, the plant had 4 high-voltage energy traces giving it entry to the grid in addition to a number of backup traces.

COULD THE REACTOR MELT DOWN?

Pressurised water is used to switch warmth away from the reactors even when they’re shutdown, and pumped water can be used to chill down eliminated spent nuclear gas from the reactors.

If the ability was minimize and auxiliary methods comparable to 20 diesel turbines (which have sufficient diesel for 10 days) didn’t maintain the reactors cool, then the gas might meltdown and the zirconium cladding might launch hydrogen.

A meltdown of the gas, which stays extraordinarily sizzling for a while even after the reactor shutdown, might start a hearth or explosion that would launch a plume of radionuclides into the air the place they may very well be unfold over a big space.

The Chernobyl accident unfold Iodine-131, Caesium-134 and Caesium-137 throughout elements of northern Ukraine, Belarus, Russia, northern and central Europe.

WHAT ABOUT THE SPENT FUEL?

Apart from the reactors, there may be additionally a dry spent gas storage facility on the web site for used nuclear gas assemblies, and spent gas swimming pools at every reactor web site which can be used to chill down the used nuclear gas.

“The basins of spent gas are simply massive swimming pools with uranium gas rods in them – they’re actually sizzling relying on how lengthy they’ve been there,” Kate Brown, an environmental historian on the Massachusetts Institute of Expertise whose ebook “Handbook for Survival” paperwork the total scale of the Chernobyl catastrophe, mentioned in August.

“If contemporary water isn’t put in, then the water will evaporate. As soon as the water evaporates, then the zirconium cladding will warmth up and it could catch hearth after which we have now a foul state of affairs – a hearth of irradiated uranium which may be very just like the Chernobyl state of affairs releasing a complete complicated of radioactive isotopes.”

An emission of hydrogen from a spent gas pool triggered an explosion at reactor 4 in Japan’s Fukushima nuclear catastrophe in 2011.

In line with a 2017 Ukrainian submission to the IAEA, there’s a complete of greater than 2,200 tonnes of nuclear materials excluding the reactors, in keeping with the doc.

WHO CONTROLS IT?

After invading Ukraine on Feb. 24, Russian forces took management of the plant in early March.

Particular Russian army items guard the power and Russian nuclear specialists are on web site. Ukrainian workers proceed to assist function the plant.

After Russian President Vladimir Putin annexed as much as 18% of Ukraine, together with the world the place the nuclear plant is situated, he signed a decree on Oct. 5 to formalise Russian management over the plant.

Ukraine’s state nuclear firm Energoatom says Russian forces have elevated their presence on the plant and has known as on Ukrainian workers to not conform to signal new contracts.

IAEA Director Basic Rafael Grossi has proposed the institution of a nuclear security and safety safety zone across the plant.