Non-destructive Assay improves accountability and safety

Posted: February 11, 2013 - 3:01pm | Y-12 Report | Volume 9, Issue 2 | 2013

Collectively, Engineering's Non-Destructive Assay group has measured more than 10,000 process locations across Y-12 for radioactive material. The unique measurements, variety of NDA applications and scope of work are distinctive within the nuclear industry.

Over decades, radioactive particulate matter can accumulate in the exhaust ductwork systems, process piping and equipment of Y-12's production facilities. This collection, known as holdup material, remains in process equipment after other accessible materials have been removed. In general, holdup material is widely dispersed in minuscule quantities and poses no real safety threat.

Imagine, though, a minor fire breaks out in the production area, triggering the sprinkler system. Water rushes through the ducts to quell the blaze below. On its way, the water gathers those randomly scattered particles, concentrating them in smaller areas. The result? The fire becomes a nuclear criticality safety concern.

The NDA group mitigates such concerns by accounting for in-process holdup material. “We use specialized equipment and nondestructive measurement and analysis techniques to characterize radioactive materials,” explained the NDA acting manager. Technicians hold detectors up to predetermined locations to quantify residual holdup. Data are immediately collected in hand-held units (see inset photo) for analysis and reporting.

Y-12's different material forms and processes generate various holdup conditions and waste streams, the acting NDA manager explained. “The experienced members of this group have found ways to account for and nondestructively analyze just about all of it.” The NDA measurements, which can confirm the presence and estimated gram quantities of enriched uranium, also support Nuclear Material Control and Accountability requirements.

“There are many places where we know enriched uranium can collect and accumulate, but gaining access to inspect, remove and sample material is not practical,” said the chief nuclear criticality safety engineer. “NDA provides a practical way to assess the accumulation of enriched uranium and direct our resources where mitigation may be necessary.”

Sharing Best Practices

As a result of its varied work scope, Y-12 has become a recognized leader in the large-scale application of nondestructive assay techniques. For example, when a group from a Russian research institute traveled to the U.S. recently as part of the Department of Energy's Material Protection, Control and Accounting Program, Oak Ridge National Laboratory asked Y-12 to share its unique and diverse NDA expertise.

“Oak Ridge National Laboratory and the Russian institute both recognized that Y-12 runs one of the most successful and long-established NDA programs within the DOE enterprise,” said the NDA acting manager. “They were especially drawn to how our program is applied to a large-scale nuclear production and manufacturing site.

“Our portion of the training included explanations and examples of how NDA techniques are used at Y-12 to provide material confirmations and to support accountability measurements of radioactive materials.” The Y-12 trainers also discussed how a reputable NDA program can help resolve security issues and protect against any potential material theft or diversion.