Nuclear Risks of the Ukraine Conflict and Why the U.S. MUST Sanction Russian Nuclear · NIRS

Nuclear reactor meltdowns: As the Fukushima disaster demonstrated, meltdowns of nuclear reactors can be caused by damage to power supplies, cooling systems, and other essential equipment that is located outside of the thick concrete-and-steel containment structures that typically enclose the reactor itself. The same is true of the VVER model reactors at Zaporizhzhia and Ukraine’s three other operational nuclear power plants. For operating reactors and those that have recently shut down, the massive amount of heat generated by the irradiated fuel in the reactor cores can quickly boil off the remaining water in the reactor vessel, and over-pressurize the reactor vessel and primary coolant system. The zirconium cladding on the fuel rods also causes steam to separate into hydrogen and oxygen, creating the risk of a large detonation, as happened at three of the Fukushima reactors. When fuel rods catch fire and melt, the molten mass can burn through the reactor vessel, and potentially cause water accumulating on the floor to flash into a steam explosion. The force of such detonations may be large enough to burst the containment structure, allowing large amounts of radiation to escape, uncontrolled and unfiltered. Even if the containment building does not crack, valves and seals on ventilation ducts, pipes, and entryways could break, allowing contamination to escape. 

Irradiated fuel: The operating reactor sites and spent fuel storage of Chornobyl Nuclear Power Plant contain thousands of tons of irradiated nuclear fuel. Most is stored in cooling pools, which depend on constant recirculation of water. If cooling is lost to a fuel pool, or water is drained out of it, the fuel can generate hydrogen, catch fire, and melt down. Once the water is drained and the fuel is uncovered, the radiation fields in the surrounding area are far too high for workers to enter the area and add water to the pools. Unlike at Chornobyl and at reactors in the US, fuel pools at most of Ukraine’s VVER reactors (those of the VVER-1000 design) are located inside the containment structure. While this could limit the amount of radiation released to the outside environment in a fuel fire, it creates what is referred to as a “common cause failure” scenario. If the reactor melts down, then the pool is likely to lose cooling, as well, virtually guaranteeing that a fuel pool fire will occur. The magnitude of radiation releases inside the containment would be far larger, thereby increasing the amount of radiation released to the outside environment. Subsequent hydrogen explosions from the fuel pool would increase the chance that containment would fail. 

Loss of offsite power: The nuclear power plants and the Chornobyl site require a constant supply of electricity to operate cooling, ventilation, and other safety systems. If transmission lines are damaged or power supply is lost for any reason, the sites must rely on backup diesel generators to provide power. Zaporizhzhia’s backup generators have a bad reliability record, and spare parts are not readily available because of the war. The supply of diesel fuel is limited: only about one-week’s worth was stockpiled on-site when Russia attacked. It has been nearly three weeks, and the transformers damaged in the initial assault have still not been repaired. 

Nuclear Risks of the Ukraine Conflict and Why the U.S. MUST Sanction Russian Nuclear · NIRS