The following was received via e-mail:
Between 2200 EST on January 23, 2019 and 0000 EST on January 24, 2019 a Ronan RLL1 [Density Scale Source] was unbolted from the frame on which it was mounted and placed on the floor. (Source was a Cs-137 0.54 milliCurie decayed to 0.45 milliCurie, Serial #212785A)
No permit was pulled to remove the scale source, and the shutter wasn't closed and locked out.
After it was unbolted, and was placed on the floor with the beam pointed towards a conveyor belt and the ceiling.
Balling line 10, Conveyor 21 was approximately 6 feet above the placed source, and the ceiling is at 60 feet.
No employees worked in front of the beam once placed on the floor.
No one noticed the scale sitting on the floor unlocked until January 24, 2019 around 1500 EST.
Once the source was found, trained personnel put the shutter block in place and locked out the source.
The RSO then authorized a permit.
Once the source was secured, and permit posted, the RSO did a full investigation.
Basic cause - The maintenance employee that unbolted the source entered the area from a direction that could only be accessed during a maintenance down. There was a radiation label on the scale itself, but no sign from his access point."