Cesium-Strontium Capsule Dry Storage
Moving Hanford’s Radioactive Capsules Toward Dry Storage
At Hanford’s Waste Encapsulation and Storage Facility, known as WESF, the U.S. Department of Energy and its contractors are moving 1,936 highly radioactive cesium and strontium capsules from underwater storage to an interim dry storage pad. The project is a major step in reducing risk at one of Hanford’s aging facilities and preparing the site for the next phase of cleanup.
The capsules date back to Hanford’s plutonium production era. In the early 1970s, cesium and strontium were removed from Hanford’s underground tanks to help reduce the temperature of the waste inside. Those materials were placed into sturdy stainless-steel capsules so they could be safely stored and monitored.
Why Move the Capsules?
WESF has provided safe and compliant underwater storage for the capsules for more than 50 years. The water provides shielding from radiation and helps manage heat from the capsules. However, WESF is an aging facility, and moving the capsules to dry storage reduces the long-term risk associated with relying on water-filled storage pools.
In plain language, the project moves some of Hanford’s most radioactive material from an older water-based storage system into a more stable interim storage setup.
The Dry Storage Solution
In October 2025, workers began moving the capsules out of the water-filled basin and into engineered concrete casks for dry storage. The work is highly controlled and performed using remote equipment inside the facility. Each cask is designed to hold up to 132 capsules. Once a cask is filled, it is moved to a nearby concrete storage pad.
Dry storage allows the capsules to be stored in a more passive configuration, with engineered concrete casks providing shielding and cooling. Moving the capsules also supports the long-term goal of shrinking Hanford’s cleanup footprint and moving WESF closer to its future cleanup and deactivation path.
Project Timeline
The first batch of capsules was successfully transferred from underwater storage to dry storage in January 2026, marking a major project milestone. Workers will continue transferring capsules from WESF into engineered concrete casks and moving the filled casks to the interim dry storage pad near the facility. The full transfer is currently expected to be completed by September 2029.