INSIGHTi
Russian Military Actions at Ukraine Nuclear
Power Plants
March 10, 2022
Russian military forces have seized two of Ukraine’s nuclear power plants as part of the invasion that
began on February 24, 2022. The four-unit Chernobyl nuclear plant, whose last operating reactor
permanently closed in 2000, was occupied shortly after the start of the invasion. Russian forces then
attacked and captured the Zaporizhzhia nuclear plant, with six operational reactors, on March 4, 2022.
The nuclear plant attacks have caused widespread concern about the potential for radioactive releases and
potential war crimes. Congress may wish to consider what actions the U.S. government could take to
support the safety and security of nuclear facilities in Ukraine.
Nuclear Power Plants Operating in Ukraine
Ukraine has four operating nuclear power plant sites with a total of 15 reactors, which in recent years
have provided about half of Ukraine’s total electricity generation. All the operating Ukrainian reactors are
light water reactors (cooled by ordinary water), using designs developed in the Soviet Union similar in
concept to most of the world’s commercial power reactors. Ukraine’s operating nuclear plants are located
throughout the country, as shown by the following map by the International Atomic Energy Agency
(IAEA):
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The 15 operable Ukrainian reactors are of a fundamentally different design than those at Ukraine’s closed
Chernobyl plant, where the Unit 4 reactor experienced an uncontrolled power surge in 1986, causing an
explosion that released large amounts of radioactivity into the environment.
Reactor Safety Systems
The core of a light water reactor, such as those currently operating in Ukraine, consists of about 100 tons
of highly radioactive nuclear fuel producing tremendous heat through a nuclear chain reaction.
To slow or shut down the chain reaction, control rods are inserted into the reactor core. Shutdown
happens very quickly in an emergency. However, even after the chain reaction stops, substantial amounts
of heat continue to be produced from the radioactive decay of the nuclear materials in the reactor core. If
water does not continue to circulate through the core, decay heat can build up enough to melt the nuclear
fuel and breach the steel pressure vessel that holds the core. The heat and pressure could also eventually
escape the concrete containment structure that surrounds the pressure vessel and associated pumps and
piping. This occurred during the Fukushima Daiichi accident in Japan at reactors built with a different
type of containment from those in Ukraine.
Highly radioactive and thermally hot spent nuclear fuel is regularly removed from the reactor core to be
replaced with fresh fuel. The spent fuel is stored in large pools of water adjacent to each reactor. The
water must be constantly cooled to carry away decay heat from the spent fuel.
Reactor Safety Risks from Russian Attacks
The Russian military attack on the Zaporizhzhia nuclear power plant in southeastern Ukraine began on
March 4, 2022, reportedly with “heavy fighting and artillery shelling.” The shelling started fires on the
site that severely damaged a training building, but were extinguished without causing radiation releases.
Russian forces seized control of the plant and its management, but the plant’s operational personnel have
remained on duty. As of March 10, 2022, two reactors were operating and four were shut down.
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The Chernobyl plant, located north of Kyiv and occupied during the first day of the invasion, does not
have any operating reactors, but the site includes large amounts of spent nuclear fuel and radioactive
debris in a huge confinement structure that is guarded and maintained. The plant is reported to have lost
power from the electric grid and is relying on backup diesel generators to power cooling and other
systems. IAEA stated March 9, 2022, that the Chernobyl power loss “does not have any critical impact on
safety.”
The ongoing Russian military action poses a range of potential threats to Ukrainian nuclear plant safety:
Direct military damage to one or more reactors. Nuclear power plants are not designed to
withstand military munitions, which could directly penetrate the concrete reactor
containment and steel pressure vessel, allowing widespread release of highly radioactive
material from the reactor core.
Military damage to reactor safety systems. Even if a military attack did not damage the
reactor containment, explosions and fires could disable the safety systems necessary to
prevent the core from overheating.
Station blackout: loss of electric power. Nuclear plants rely on electricity to run cooling
pumps and control systems. If power from the electric grid is lost, diesel generators
produce backup power, and are intended to operate long enough for grid power to be
restored. Loss of power from both the grid and the diesel generators results in station
blackout, the condition that caused the radioactive releases at Fukushima.
Disruption of plant personnel. Plant safety could be at risk if military action hindered or
blocked the hundreds of workers needed to operate, maintain, and manage a nuclear
power plant.
Damage to spent fuel pool or cooling systems. If damage to a spent fuel pool allowed its
water to drain, or if its cooling systems were disabled, the spent fuel could overheat and
release large amounts of radioactive material to the environment.
International Response
The State Nuclear Regulatory Inspectorate of Ukraine reports on facility conditions to the IAEA. At
Zaporizhzhia, the Ukrainian regulator reported that internal communications “have been disrupted or cut
off.” IAEA Director General Rafael Grossi is negotiating anagreement on safe practices with the
Ukrainian and Russian foreign ministers. IAEA daily reports summarize reactor operations.
During an emergency U.N. Security Council meeting, U.S. Ambassador Linda Thomas Greenfield called
on Russia “to withdraw its troops from the plant, to permit medical treatment for injured personnel, to
ensure operators have full access to the site and are able to communicate with nuclear regulators, and to
allow the operators to conduct shift changes to ensure the continued safe operation of the plant.” Some
analysts argue that the attack could be considered a “war crime” under international law.
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Author Information
Mark Holt
Mary Beth D. Nikitin
Specialist in Energy Policy
Specialist in Nonproliferation
Disclaimer
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