No injuries or contamination reported in Hanford tunnel collapse

The 9 May collapse of a tunnel containing decades-old contaminated equipment at the Hanford site in Washington State prompted the Department of Energy to order employees in nearby areas to take shelter indoors. No one was injured, all employees were accounted for, and no detectable release of radioactive materials occurred, according to DOE’s Richland Operations Office.

The approximately 100-meter-long tunnel contains eight contaminated railroad cars. The hole, which is roughly 6 meters in diameter, opened up where the tunnel intersects with a longer tunnel that contains 28 rail cars. The cars were used to transport irradiated nuclear fuel rods. The wood and concrete tunnels were constructed in the 1950s and 1960s; they were sealed in the mid 1990s and have undergone periodic checks. They are covered by about 2.5 meters of soil.

Hanford site spokesperson Destry Henderson said that as of the morning of 10 May, air monitoring hadn’t detected any release of radiological material. He said workers had begun to “slowly, safely, and methodically” prepare to fill the hole with soil. All nonessential Hanford employees were told to remain home. On the day of the collapse, nonessential employees in the vicinity and those at the nearby LIGO Hanford Observatory were sent home early as technicians surveyed the area for contamination.

In a statement, a DOE spokesperson said Energy Secretary Rick Perry “has every confidence in the dedicated experts on the ground at the Hanford site.”

Originally, DOE officials had planned to decontaminate and remove the rail cars and permanently bury them. But according to a DOE fact sheet , that process “would entail extreme worker safety hazards.” Instead, officials are considering a less expensive plan to encase the cars in place in a grout material.

The affected tunnel is adjacent to the PUREX (plutonium–uranium extraction) plant, which was built in the early 1950s and is awaiting decontamination and demolition. The PUREX facility was the largest of five reprocessing “canyons” at Hanford where plutonium for nuclear weapons was chemically separated from highly radioactive nuclear fuel rods irradiated in multiple production reactors. The last of those reactors was permanently shut down in 1987, and PUREX operations ceased a year later.

Beyond the collapse, the primary environmental concern at Hanford is the 200 million liters of high-level liquid waste that are stored in 177 underground tanks. Some of the tanks have leaked, and the waste is slowly migrating in groundwater toward the Columbia River. In the past, radionuclides were released into the river through water used to cool the production reactors. Airborne releases of radioactive materials, mainly iodine-131, occurred during plutonium production operations.

The LIGO gravitational-wave detector was not in operation when the tunnel collapsed because engineers were performing previously scheduled maintenance of the detector’s optics. Officials at the observatory said a small crew would continue that work.