Crews Employ Novel Strategies in Cleanup of High-Risk Structure at ORNL

Source: EM Update | Vol. 14, Issue 6; Contributor: Carol Hendrycks | February 15, 2022

EM crews at Oak Ridge recently devised innovative approaches to enable deactivation and demolition of the final portion of the former Radioisotope Development Laboratory.

That structure, known as the East Cell Bank, is on DOE’s list of high-risk excess contaminated facilities. It’s located in the heart of Oak Ridge National Laboratory (ORNL) near ongoing research missions.

Workers with EM cleanup contractor UCOR characterized the final cell to identify potential radiological and hazardous contamination. They conducted the work in stages under a six-story protective structure erected to ensure nearby facilities and ongoing research missions at ORNL aren’t impacted by the cleanup.

The crews began by taking surveys and readings from an opening at the front of the structure. They used long-reach tools and a specialized radiation detector. The detector overlays a radiation-intensity color map on a picture of the environment and identifies gamma-ray emitting nuclides and their locations.

Once data showed it was safe for personnel to enter the facility, the workers moved the equipment farther inside to perform more characterization and surveys. They continued this process safely and methodically, gathering data and processing the results from one area before moving forward to another area to characterize and survey.

Portions of the structure had contamination levels requiring remote entry to get readings. The team developed a plan to access those areas by removing a concrete plug in the roof and lowering equipment inside to complete the characterization. However, the plug could not be removed due to it being sealed in place more than a decade ago.

The employees used a system they designed to crack the seal. An 80-ton mobile crane lifted the 9,000-pound plug, allowing workers to access areas of the facility to capture remaining readings and complete characterization.

The tool they used to capture the readings detects sources of gamma-emitting radioisotopes and locates sources of detected gamma ray. The instrument identifies hot spots in large areas, eliminating the need for crews to take samples by hand, thereby reducing the time workers spend in a radiation environment.

With characterization complete, deactivation is underway. Workers are safely removing, packaging and shipping waste for disposal. Once deactivation and decontamination phases are complete, crews will tear down the structure. Demolition is expected to be completed next year.