Russia to permanently seal leaking section of ISS

Russia seals off the leaking area

Roscosmos is preparing to close the tunnel that connects to Russia's Zvezda module on the ISS. The leak was first found in 2019 in a small tunnel called PrK. NASA and Roscosmos tried several patches, but none fully worked. Reports say the hatch between Zvezda and PrK will be shut for good, so the leak is cut off from the rest of the station.

What PrK is

PrK is a small space at the back of the Zvezda service module. It works as a passage that astronauts use to move around and to carry cargo between the station and cargo ships such as Progress and Soyuz, which dock at the rear port. Because it sits between two hatches, it can be sealed off and act as its own separate space if needed.

Key facts about the leak

• The leak was first found in 2019.
• The leak rate doubled from 0.5 kg per day to 1 kg per day in February 2024.
• It peaked at nearly 1.7 kg per day in April 2024.
• In June 2025, NASA saw pressure signals that suggested the leak might be sealed.
• Less than a year later, pressure in PrK was found to be dropping slowly again.

A dispute between the two agencies

NASA and Roscosmos have disagreed about the cause and how serious the leak is. Tension rose in early this year, when five ISS astronauts were told to shelter in place while Roscosmos prepared a risky repair. Russian cosmonauts were also told to use a saw to reach a suspected leak spot. NASA officials did not agree with this method, saying it could raise the risk to the structure.

Why it matters

The ISS needs a steady supply of air and cargo to keep crews safe. Closing PrK shows that the leak has not been fixed, and it changes how the station is supplied. The next Progress cargo mission will unload through another Russian module, Poisk, instead of Zvezda. This is the first supply mission to be affected.