It will take at least “the next several months” to clean up a cesium-137 spill from May at a University of Washington medical research building in Seattle, a spokesperson for the U.S. National Nuclear Security Administration (NNSA) said Thursday.
The public has been barred from the seven-floor Research and Training Building near the Harborview Medical Center since May, following the breach of the cesium-137 source that was part of an irradiator the university was getting rid of under an NNSA-funded program that aims to secure potentially dangerous radionuclides.
The contractor on that job was International Isotopes, of Idaho Falls, Idaho. The nuclear medicine and source removal specialist is now in charge of cleaning up the spill it caused and has “just about finished up characterization” of the accident site, the NNSA spokesperson said in the email.
“The remediation process is expected to last the next several months,” the spokesperson wrote. “When that is completed, the state of Washington’s Department of Health has the authority to release the building for occupancy of laboratory personnel, building maintenance staff and other building occupants, as well as the general public.
Details of the amount of cesium that spilled and the remediation process have not been made public. The work in the building poses no public-health threat, the spokesperson added.
The NNSA trucked the damaged irradiator, manufactured by J.L. Shepherd & Associates, out of the Research and Training Building in July. It had been guarded in a sealed lead container at the building’s loading dock after the accident. The accident spread contamination throughout all seven floors of the Research and Training Building, the Washington state Department of Health has said.
Energy Department personnel at the Pacific Northwest National Laboratory are now studying the damaged irradiator some 200 miles away from Seattle in a hot cell near the agency’s Hanford Site: the hub of plutonium production during the Cold War nuclear-arms race, and now the agency’s largest environmental cleanup project.
The NNSA has said it plans to dispose of the damaged irradiator outside of Washington state.
In the May 2 accident, 13 people in the Research and Training Building were exposed to finely powdered cesium chloride powder from the broken irradiator. Cesium-137 emits highly penetrative gamma-rays, which can destroy human cells.
The University of Washington was getting rid of the irradiator with a grant from NNSA’s Cesium Irradiator Replacement Project: an effort that helps organizations replace medical devices that use potentially dangerous radionuclides with analogous devices that use X-rays instead. Cesium could be used to craft a population-sickening “dirty bomb” radiation dispersal device.
