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Tanks being unloaded from a C-130
Here we see the aforementioned tanks--and the overall MAFF (Modular Airborne Firefighting System) setup they're part of--being unloaded from a C-130.
The tanks are placed on a robotic platform
"You can't get inside the tanks to inspect them, and a camera only gives a surface view," says U.C. Davis Radiography Supervisor Hal Egbert, who conducts the safety tests. At the McClellan Nuclear Radiation Center, the tanks are placed on a robotic platform in a special scanning bay and turned through a neutron beam (which comes out of the block to the left).
A neutron radiograph pinpoints problemsThe neutron radiograph is recorded on film similar to that used for X-rays. Unlike an X-ray, however, which can see through water but is stopped by metal, a neutron scan penetrates metal but is stopped by water and corrosion. That's enabled Egbert to find flaws that are invisible to the eye and to other systems. And, in some cases, it's allowed him to show that apparent weaknesses are, in fact, stronger than they look.
This image shows a neutron radiograph of an outlet tube from one of the retardant tanks. Pits of corrosion that have reduced the thickness of the metal are marked.