nuclear-news

Ukrainian artillery cuts last backup power line to Zaporozhye Nuclear Power Plant

Steven Starr,  April 6, 2024

The fuel rods within the reactor core and in the spent fuel pools will continue to emit a large amount of heat (from the continuous decay of fission products within the fuel) even after the reactors are in a “cold shutdown”. Thus, electric power is required to run the cooling systems in the spent fuel ponds and the pumps that push cooling water through the reactors. If no offsite electricity is available, diesel generators are required to generate electricity to operate the pumps to cool the reactor and the cooling systems that cool the spent fuel pools. 

A prolonged failure of the cooling systems (from loss of electric power) to continuously remove heat from the spent fuels will eventually cause the water in the pools to boil off and expose the spent fuel rods to steam and/or air. Exposure of the fuel rods to steam and/or air will cause them to overheat to the point of rupture or ignition, leading to the massive release of radioactivity. (The Soviet-designed reactors have their spent fuel pools inside the primary containment, unlike US reactors that locate spent fuel pools outside primary containment).

The fuel inside the steel reactor containment vessels must also be cooled (by pumping cooling water through the containment vessel). Failure of the cooling pumps to circulate water through the core will lead to the water in the containment vessel to superheat and eventually lead to the damage of the fuel rods, which would release large amounts of highly radioactive fission products.

Offsite power to the Zaporozhye Nuclear Power Plant (ZNPP) has historically been provided by the Zaporozhye Thermal Power Station, which is located several kilometers away from the ZNPP. I think the damage to backup power line from Ukrainian artillery fire refers to the destruction of the power lines and power transformers that connect the Thermal Power Station to ZNPP.

April 8, 2024 - Posted by Christina Macpherson | safety, Ukraine