A Russian cargo ship carrying what its own captain later admitted were components for two submarine nuclear reactors sank off the coast of Spain in December 2024, and a CNN investigation published Monday May 12, 2026 reveals the full picture of where those reactors were likely headed, what they were for and what may have caused the ship to go down.
The vessel, the Ursa Major, also known as Sparta 3, sank approximately 100 kilometers off the Spanish coast on December 23-24, 2024, after a series of explosions killed two crew members.
The Russian state-linked owner called it a terrorist attack. But a Spanish investigation obtained by CNN suggests the hull may have been pierced by a Barracuda supercavitating torpedo, a high-speed weapon possessed by only a handful of the world’s most elite militaries, including the United States.
The suspected destination was not Vladivostok, as the public shipping manifest claimed.
Russian captain Igor Anisimov, per sources familiar with the Spanish investigation, believed he was taking the reactors to the port of Rason in North Korea.
What Was Actually On The Ship
The Ursa Major’s official cargo manifest, filed with public shipping records, listed its load as two large “manhole covers,” 129 empty shipping containers and two large Liebherr cranes. The destination was listed as Vladivostok in Russia’s Far East.
Spanish investigators found that story implausible from the beginning. A ship does not sail from St. Petersburg through the Mediterranean and around to Vladivostok to deliver cranes and empty containers when Russia has an extensive rail network capable of handling exactly that kind of domestic cargo.
The cranes made more sense as equipment to assist in offloading sensitive cargo at a foreign port, specifically, the port of Rason on North Korea’s northeastern coast.
The Spanish government addressed the cargo question in a statement released February 23, 2025, under pressure from opposition members of parliament who had been asking pointed questions about what the ship was carrying and why it had sunk in their waters.
The government confirmed what its investigators had learned from the Russian captain. “He eventually admitted that they were components of two nuclear reactors, similar to those used by submarines,” the statement said. “According to his testimony, and without being able to confirm it, they did not contain nuclear fuel.”
The specific reactor type identified by researchers and investigators is the VM-4SG, a naval nuclear reactor used in Russian submarines.
The components, if successfully delivered and installed in North Korean vessels, would represent a significant upgrade to Kim Jong Un’s submarine program and to North Korea’s ability to deploy nuclear-armed submarines capable of striking targets across the Pacific.
The Timing That Explains Everything
The context of when the Ursa Major departed Russia explains why investigators believe the reactor transfer was happening and why the international community may have decided to stop it.
The ship departed Russia shortly after Kim Jong Un sent North Korean troops to support Russia’s war against Ukraine, a military exchange that brought approximately 10,000 or more North Korean soldiers to the front lines in eastern Ukraine.
Those troops were equipped with North Korean ballistic missiles that had already been used against Ukrainian cities.
The missiles had undergone what amounted to live combat testing in Ukraine, giving North Korea real performance data on how US-made and Western interceptor systems responded to their weapons.
North Korea, in other words, had provided Russia with something extremely valuable: military manpower and live-fire weapons testing that yielded intelligence about American defense systems.
The reactor transfer was likely the payment. Russia would upgrade North Korea’s submarine nuclear capabilities in exchange for troops and missiles.
Experts described the arrangement to CNN as a “quid pro quo,” Russia giving Kim Jong Un the submarine modernization his navy had been seeking, while Kim gave Putin soldiers to throw at Ukrainian positions and ballistic missiles whose performance data was now informing future North Korean weapons development.
The reactor transfer, if completed, would have represented one of the most significant nuclear proliferation events in recent decades, a state with advanced nuclear submarine technology passing it to a rogue nuclear state with a demonstrated willingness to use military force and a record of pursuing nuclear capabilities specifically to hold the United States at risk.
How The Ship Sank And What Spain Found
On December 23, 2024, the Ursa Major suffered three explosions. Two crew members died.
The Russian escort ship that was traveling with the Ursa Major, the Ivan Gren, a Russian landing ship, responded to the Spanish coast guard and rescue personnel in a way that investigators described as aggressive, ordering Spanish rescuers away from the sinking vessel.
The behavior of the Ivan Gren is one of the details that has attracted the most scrutiny from investigators.
A Russian military vessel ordering Spanish emergency services away from a civilian ship sinking in waters near Spain is not normal maritime behavior.
The most logical explanation is that the Russians were managing access to the sinking ship’s cargo, a cargo they had officially described as cranes and empty containers but which was actually submarine nuclear reactor components.
After the initial three explosions, four additional explosions were detected near the ship before it settled on the seabed.
The investigators’ assessment is that these four subsequent explosions were most likely triggered by the Russians to destroy or damage the sensitive cargo before it came to rest at 2,500 meters depth, preventing recovery of the reactors by anyone else.
The ship now sits at approximately 2,500 meters beneath the Mediterranean.
The Spanish government told opposition MPs that retrieving the flight data recorder from that depth would be “impossible without significant technical resources.”
The Torpedo Theory
The explanation for what caused the initial three explosions has not been officially confirmed by any government.
The Spanish investigation obtained by CNN assessed it as possible that a Barracuda supercavitating torpedo was used to pierce the hull, triggering the chain of events that sank the vessel.
A Barracuda torpedo is a supercavitating weapon, a torpedo that travels within a bubble of gas, dramatically reducing water resistance and allowing it to reach extreme speeds compared to conventional torpedoes.
The technology is possessed by a small number of the world’s most advanced militaries. The United States is among them.
The timing of the incident, the final weeks of the Biden administration, is the element that has generated the most speculation about who decided to act and why.
If a Western military or intelligence operation was responsible for sinking the Ursa Major, it would represent a covert intervention designed to halt one of the most dangerous nuclear proliferation transfers in modern history, carried out in the final days of a presidential administration that may have concluded direct military confrontation with Russia over the matter was not viable.
Some analysts have described the torpedo theory as “far-fetched.” What those skeptics have not provided, per the CNN investigation, is an alternative explanation for what caused three explosions to strike a cargo ship in the Mediterranean with no other obvious source.
Where This Leaves Things
The wreck sits at 2,500 meters. The reactor components, if not destroyed by the Russian-triggered follow-on explosions, are on the seabed.
The captain who admitted what he was carrying has provided the testimony that drives the Spanish investigation’s conclusions.
No government has officially claimed responsibility for sinking the Ursa Major.
The United States has not commented on the CNN investigation. Russia has maintained that the sinking was a terrorist attack and has not acknowledged that the ship was carrying anything other than what the manifest said.
What the CNN investigation has put into the public record is a specific sequence of events that began with a North Korean troop deployment to Ukraine, produced a bilateral arrangement to transfer submarine nuclear technology, and ended with a ship at 2,500 meters on the floor of the Mediterranean.
The question of who made that specific outcome happen, and whether it happened deliberately, is the one that no official is prepared to answer publicly.
