I worked for 21 years at the University of California, Davis campus as an accelerator operator on their 76" cyclotron. While setting up a new experimental area we found the need for a way to remove a radioactive beam dump so people could enter the area to change parts for the experiment. We came up with a pretty unique solution.
The experimental area is at the end of a beam line where a 67 MeV proton beam exited into the room. The parts were set up in its path but just past there we used a 2"X 11"X11" Carbon block to stop the beam. The block became highly radioactive during long experiments and would take hours to die down to a safe enough level for people to enter the room. Since we charged $500/hour for beam time we needed a way to shorten this waiting period.
We came up with the idea of using a G scale train that ran along the wall and curved out to the Carbon block. We mounted the block on a flat car at the end of the train. When an experimenter wanted to go in the room we would turn off the beam and initialize the safety system. A beam block would roll into place in the beam line, tripping a switch that initialized the train which pulled the block down the track around the curve and down the wall. About 5' from the target area we built a "coaling tower" where the flat car would be taken to. Inside the tower was lined with lead bricks to provide enough shielding to knock down the radiation to a safe level. The experimenter would come into the room, get their part and put a new one in place. When they left and closed the room up we would open the beam plug to start the next experiment. The movement of the beam plug initiated the train to reverse direction and back the Carbon block into position. We used sensors and cameras to make sure everything was properly in place.
To make the coaling tower we used the wood from old pallets and ran them through a table saw to make dimensional lumber. We made the roof from cardboard, stripping off one side to reveal the corrugations and then painting with a grey paint from a rattle can. We also built a wooden trestle on the curve where the track curved out from the wall. We eventually removed the trestle to get better access to the backside of the experiment area.
This project earned us quite a reputation in the industry and people from all over the world enjoyed working with our unique safety system.
Ater about ten years the train was replaced with a different system. We ran power through the rails so regular maintenance was required. If we had known about dead rail back then it probably would still be in operation. The picture below shows the control room for the cyclotron. In the upper left you can see the original switching engine we used before going with the more powerful diesel.
The only part of the train that got hot was the flatcar and that died down pretty quickly. The Carbon block stayed hot for quite a while.
The train idea was scrapped after I retired. We had a small crew and I was the only one into trains so they kindly waited until I was gone and then replaced it with the more expensive "scientific" looking system. Most experimenters got a kick out of the train but I suspect my crew thought it was unprofessional. Personally I think if ya can't have fun on your job then it's just another job.
____________________ Tom Ward
"When I die I want to go quietly in my sleep like my grandfather. Not screaming in terror like his passengers."