If you are referring to the ROSA arm, sir your 80 lb estimate is low and if you are referring to the UAB found in ROSA III suffice to say we took it apart to get it into the building . Tube diameters were between 3/4 and one inch but the wall thickness was no where near that.
The reason plants had radiation monitoring equipment going into the plant was related to a Westinghouse engineer becoming contaminated in the north test cell at Waltz Mill and dragging that from Waltz Mill all the way to a site where it was discovered on the way out not in. So, the monitors where there to protect the plant from having to explain "unexplainable" contaminations.
The "day labor" comment was essentially true however the lifetime part of that is dead wrong. back then (until 1992) exposure limits were 3 R per quarter and 5 R per year (Federal limits, wholebody, form 4) with a lifetime limit of 1(N-18)R or one rem per your age minus 18. So assuming that you were grabbed off of a bar stool a few days before a change in quarter at the ripe old age of 23 (1(23-18)=5) and jumped into the steam generator for the typical 3-5 minutes it would take to accumulate 3 rem. A few days later when the quarter changed they threw you back in for a little less than 2 rem more. You have worked a week and hit 5 rem total committed dose. Next year you could get another rem according to the law. In 1992 the law was changed (10cfr20) and the quarterly limit went away along with the lifetime limit.
However, what utility in its right mind is going to change its story from "it isn't safe for you to be exposed to more than 1 rem for every year you have been over 18" to "sure come get all you like up to 5 rem per year. No worries." That is a lawsuit waiting to happen. I am sure even now people with high lifetime exposures are either refused access to the RCA or maybe even refused unescorted access to avoid being the cause of the person receiving more than the old 1N-18 rule.