Cutting lethal radioactive leak risks in Eastern WA takes major step

The first highly radioactive capsules of cesium stored underwater in an aging pool at the Hanford nuclear site in Eastern Washington were transferred this week to safer dry storage.

“This is a significant step forward for safety at Hanford,” said Washington Gov. Bob Ferguson. “… Transferring these capsules of waste to safer, long-term storage will help protect workers, communities and the environment for generations to come.”

Preparations have been underway for a decade to get 1,936 capsules of radioactive cesium and strontium out of a stainless-steel-lined pool in the center of the Hanford site that is at risk in the event of a severe earthquake.

The waste is so radioactive that the work to package the waste into large, specially designed concrete casks and move the casks to outdoor concrete pads for storage has to be done with remotely operated equipment.

Moving the capsules into dry storage is a “huge risk reduction for the site,” said Ray Geimer, the Department of Energy manager at Hanford, speaking at a recent Hanford Advisory Board subcommittee.

The capsules, most of them about 22 inches long, contain about 30% of all the radioactivity at the Hanford site.

A loss of power to the building containing the pool or a loss of water could cause the capsule to overheat and break, releasing what Geimer said would be a lethal radiation dose.

The pool holding the capsules in the Waste Encapsulation and Storage Facility (WESF) on the end of B Plant was designed to be used only until about 2004. Severe earthquake risk raised

The cesium and strontium were removed from Hanford’s underground waste storage tanks and packed in capsules from 1967 to 1983 to reduce the rate at which heat was generated in the tanks and improve the stability of the tanks.

The Hanford site was used from World War II through the Cold War to produce nearly two-thirds of the plutonium for the nation’s nuclear weapons program.

Uranium fuel irradiated in Hanford reactors was chemically processed to remove the plutonium, leaving a stew of 56 million gallons of radioactive and hazardous chemical waste in underground tanks.

Hundreds of the cesium capsules were leased for commercial use and government research in the 1980s, with moving them in and out of water storage potentially damaging the metal of the capsule.

In 1988, a leak of cesium was detected in a capsule being commercially used by a radiation sterilization company in Georgia, and DOE’s leasing program ended.

After that all 1,335 cesium capsules and 601 strontium capsules were stored in the WESF pool under 13 feet of water to protect workers from their radiation and to help cool the capsules. They can be as hot as 1,000 degrees Fahrenheit.

In 2013, the Oregon Department of Energy raised concerns that the concrete walls of the WESF pool had lost structural integrity due to high radiation exposure over four decades.

The next year the Department of Energy Office of Inspector General found that the pool, built in 1973, could be at risk in a severe earthquake.

The 2014 inspector general memo said that WESF was the DOE facility at the greatest risk in the case of a natural disaster beyond what it was designed to sustain. 10 years to prepare for capsule transfer

DOE expects to continue filling and moving a total of 18 casks to the new fenced, concrete pads near WESF for several years. It has a legally binding deadline under the Tri-Party Agreement to have all the capsules in dry storage before October 2029.

The first step toward moving the casks to safer storage was modifying WESF’s aged ventilation system and filling six of its aged ventilation system and filling six of its contaminated hot cells with grout. The remaining hot cell, G Cell, is being used to help prepare the capsules for dry storage.

In 2020, a full-scale mock-up of G Cell was built in an unused Hanford building to test equipment and allow workers to practice tasks, including using manipulators like those that are operated outside the hot cell during capsule packaging.

Additional construction was done in recent years not only to modify WESF for packaging the capsules, but also to build the outdoor storage area for the capsules.

The project required a heavy-haul road to the new reinforced concrete pads for dry storage of the capsules a half mile from WESF.

The pads are similar to the one Energy Northwest uses about 10 miles north of Richland to store used fuel from the Columbia Generating Station – the Northwest’s only commercial nuclear power plant – until the nation has an underground repository for used commercial reactor fuel and high-level radioactive waste from weapons sites such as Hanford. Cesium capsules repackaged remotely

As work has started to remove the cesium capsules, workers for DOE contractor Central Plateau Cleanup Co. stand above the WESF pool and used long-handled tools to move the highly radioactive capsules into chutes to transfer them to G Cell.

In G Cell, the capsules are inspected for damage by workers looking through a leaded glass window into the cell, and then workers outside the cell use manipulators to place the capsules in a stainless steel container that can hold six of them.

The air in the container is replaced with helium to help dissipate the heat from the capsules.

The filled containers are transferred out of the top of G Cell and moved by crane in a shielded transfer system to the WESF truck port, where the containers are lowered into shielded transfer casks.

The 11-foot tall, 10-foot diameter casks are shielded with reinforced concrete and can hold up to 132 capsules.

A robotic welder seals the lid of the cask’s inner storage container and helium is used again to replace air. Then an outer lid is welded into placed.

The cask is loaded onto a transporter repurposed from DOE’s West Valley, N.Y., nuclear remediation project, saving taxpayers nearly $2.5 million, to be hauled to the new storage pads. Each cask weighs 163,000 pounds. Safe storage saves money

The new pads include a temperature monitoring system, and the dry cask storage system allows airflow for passive cooling.

After workers removed the first capsules from the WESF pool in November, CPCCo President Bob Wilkinson said the project would eventually reduce the need for extensive monitoring and maintenance of the capsules underwater.

Deactivating WESF can save as much as $6 million a year, by some estimates.

When DOE began considering dry storage in 2014, it was spending $7.2 million annually on constant monitoring and maintenance for underwater storage.

“We’re continuing to make historic progress at Hanford,” said Stephanie Schleif, the nuclear waste program manager for the Washington Department of Ecology, which regulates environmental cleanup work at Hanford.

“Transferring these capsules to safe dry storage is a top priority for the state and is integral to the goal of cleaning up Hanford and protecting the environment and surrounding communities,” she said.