In my youth I had a student intern job at what was the Atomic Weapons Research Establishment at Aldermaston in the UK. The chambers they used for counting low-level radiation were made of battleship steel for the reason you describe - any background radiation would interfere with the count.
I was told at the time that steel blast chamber linings had a slightly radioactive layer in the lining to show when the lining was getting too thin and needed replacing, but you are correct that the atmosphere also had low radiation levels - after all in the sixties we were drinking radioactive milk from the strontium-90 from nuclear tests.
Radiation counting chambers is a pretty niche market, but it is there:)
In my youth I had a student intern job at what was the Atomic Weapons Research Establishment at Aldermaston in the UK. The chambers they used for counting low-level radiation were made of battleship steel for the reason you describe - any background radiation would interfere with the count.
I was told at the time that steel blast chamber linings had a slightly radioactive layer in the lining to show when the lining was getting too thin and needed replacing, but you are correct that the atmosphere also had low radiation levels - after all in the sixties we were drinking radioactive milk from the strontium-90 from nuclear tests.
Radiation counting chambers is a pretty niche market, but it is there:)