A group of technicians ascend stairs in the neutron source’s main reactor hall. Months after Russian rockets last landed on the grounds of the Kharkiv Institute of Physics and Technology, staff were still conducting repairs on the facility. | All photos by KERN HENDRICKS for UNDARK

Keeping the Lights On at Ukraine’s Research Nuclear Reactor

In the pre-dawn hours of March 6, 2022, a Russian rocket struck a large, white-and-gray-sided building in the eastern Ukrainian city of Kharkiv. Although the building could easily be mistaken for a warehouse from the outside, inside it contained a nuclear research reactor known as a neutron source. Neutron sources are often used for medical research — in this case to create an isotope commonly used to diagnose certain forms of cancer — and this one helps train Ukraine’s nuclear scientists and technicians.

The neutron source is located at the Kharkiv Institute of Physics and Technology, the former home of one of the Soviet Union’s first nuclear weapons development laboratories. The neutron source was funded and constructed under a 2010 deal between Ukraine and the United States in which the former agreed to remove Soviet-era nuclear fuel stockpiles in return for support for domestic nuclear power and research programs.

Prior to the Russian invasion of Ukraine, around 2,000 people worked at the institute. Mykola Shulga, KIPT’s director, told Undark that more than 750 staff members have since fled, some to other parts of Ukraine, and some to Europe.

Although the reactor itself was not damaged in the 2022 attack, several key parts of the facility were, including a power transformer critical to its continued operation. When Undark was granted access to the facility in February 2023, technicians were also busy repairing an air filtration system that had been destroyed by the rocket’s shockwave.

The main office building of the Kharkiv Institute of Physics and Technology. KIPT is one of Ukraine’s oldest and largest physical science research institutions, and the former home of one of the Soviet Union’s first nuclear weapons development laboratories. More than a year after it was initially attacked, many of the windows are still boarded up after being destroyed by blasts from Russian rockets.

The neutron source uses a fraction of the nuclear fuel needed to power a standard nuclear reactor. But while most nuclear power plants use uranium containing between 3 and 5 percent of uranium-235, the isotope capable of sustaining a nuclear chain reaction, the neutron source’s fuel is enriched to 19.5 percent, putting it just under the threshold of being classified as highly enriched and close to weapons grade. Highly enriched uranium is considerably less stable, and therefore more dangerous from a nuclear security standpoint. Although the risk of an accident is low with such a small amount of fuel, a direct hit to the reactor or KIPT’s fuel storage could potentially release damaging amounts of radiation into the surrounding area, according to KIPT staff.

As the war in Ukraine continues into its second year, the challenges for scientists and staff at KIPT are not likely to abate soon. “Everything is now much more difficult than it was in normal life,” said Andrei Mytsykov, the neutron source’s head engineer, speaking through a translator. Despite their efforts, he added, staff at the facility don’t currently have the means to provide the levels of nuclear safety that international standards require.

Tamara Kuznetsova started working at KIPT in 1958 as a member of the heating and maintenance department, later working her way up to the head of physical security. At the urging of her daughter, Kuznetsova left Kharkiv when the Russian invasion began on February 24, 2022. But within two months, she returned to KIPT.
Kuznetsova displays an old photograph of herself, taken in the 1960s after she joined KIPT. She has acted as the institute’s head of physical security for more than 30 years.
A photograph in Kuznetsova’s office depicts KIPT members marching in a parade in Kharkiv during the days of the Soviet Union. Founded in 1928, the institute played a critical role in the Soviet Union’s science and research programs.
The core of KIPT’s neutron source now sits in darkness. On the first day of Russia’s invasion of Ukraine, technicians placed the reactor into a state of hibernation, to minimize the possibility that radiation would be released should the building be struck by Russian bombardment.
External view of the neutron source building, which houses a small nuclear research reactor, most of its critical support systems, controls, and a few staff offices. On March 6, 2022, a Russian rocket impacted the building.
External damage to the neutron source facility, caused by a Russian rocket. While no rockets reached inside of the facility, shrapnel and blown-out windows and vents caused interior damage. Blast waves from the attack traveled through the air ventilation system, damaging several internal components.
Further damage to the outside of the neutron source facility. The blast destroyed an electrical substation located on the north side of the reactor hall, which had not yet been replaced when Undark visited the site several times in January and February 2023.
A device used to load low-enriched uranium fuel rods into the core of the reactor. As of April 2023, fuel rods were still loaded in the core of the reactor, posing potential danger if the reactor were to suffer a direct hit from artillery or rocket fire. Although the neutron source is a subcritical reactor — meaning it cannot suffer a catastrophic meltdown — the low-enriched uranium in the fuel rods would still pose a significant contamination risk if the core of the reactor were to be ruptured.
Much of the neutron source facility’s ventilation system was destroyed by multiple instances of shelling in March, May, and June of 2022. When Undark visited the site in February 2023, many sections were still under repair.
Recently repaired sections of the neutron source facility’s ventilation and air filtration systems, which were damaged by pressure waves caused by the explosion of Russian rockets.
A KIPT staff member inspects shrapnel damage on the inside of a stairwell, less than 100 feet from the reactor. Although no rockets directly struck the reactor itself, many vents and windows were blown out, and deadly shrapnel was able to penetrate into the building.
Due to the destruction of Kharkiv’s electricity grid, technicians at the neutron source used store-bought commercial air heaters to prevent temperatures in the main reactor hall from falling below freezing, and thus possibly damaging the reactor core.
A technician inspects air ventilation pipes inside the neutron source’s building. Many members of the KIPT staff fled Ukraine in the early days of the war, and the neutron source facility is now overseen by a reduced staff. Manual inspections and repairs are a large part of each day’s work, and the volume of tasks to complete is huge, even with a sufficient amount of technicians. More than a year after the facility was hit by Russian rockets, staff are still conducting repairs.
View of the neutron source reactor hall. In the absence of a functioning electricity grid, technicians often rely on battery-operated LED lights to illuminate the hall when there’s work to be done.
A technician stands next to a sign indicating radioactivity, in a hallway near the reactor. Instead of power generation, this reactor is primarily used to train nuclear technicians and isolate medical isotopes.
A detector used to measure radiation levels in the neutron source’s main reactor hall. Damage to Kharkiv’s electricity grid meant that, for a period, the automated safety systems did not function correctly, and staff were forced to conduct manual safety checks.
Kuznetsova spends a moment with a dog that lives on the KIPT campus. Kuznetsova has worked at the institute for over six decades. Feeding the dog is sometimes a part of her daily routine.
Many of the buildings on the KIPT grounds now sit unused due to damage. The wall of this building was only recently repaired.
A crater on the KIPT grounds caused by a Russian rocket strike in early 2022. The grounds are scattered with dozens of such craters.
Remains of a Russian rocket that impacted the neutron source site on March 6, 2022, meters from the reactor’s main building.
Crater from the March 2022 attack. Several rockets impacted the areas near the neutron source facility between March and June 2022.
Mykola Shulga, 76, is the current director of KIPT. Shulga began work as a researcher at the institute in 1973, and was appointed director in 2015. He said that it’s been difficult to keep staff at KIPT in the wake of Russia’s invasion: When the war started, he said, about 250 of the staff fled Ukraine, and another 500 fled to other parts of Ukraine.

Note: Numerous interviews for this story were conducted with the help of Yulia Zubova, who aided with translation during conversations with Ukrainian speakers. She also provided on-the-ground logistical support and supplemental reporting.