Editor's Note: The above video reporter is about a partial tunnel collapse at Hanford in 2017. 

Workers have finished stabilizing a second tunnel containing radioactive wastes on the Hanford Nuclear Reservation.

The U.S. Department of Energy announced Monday it had completed filling the tunnel with engineered grout, reducing the risk of a collapse and possible release of radioactive materials.

A federal contractor began grouting the tunnel next to the Plutonium Uranium Extraction Facility last October.

Crews placed the last truckload of grout on Friday.

The tunnel contains 28 railcars holding contaminated equipment and materials generated when Hanford made plutonium for nuclear weapons.

The decision to grout Tunnel 2 was made after the partial collapse of an adjacent waste storage tunnel, known as Tunnel 1, in 2017.

Hanford is located near Richland, Washington, and for decades made most of the plutonium in the nation's nuclear arsenal.