[John Rogers]

Those are similar to the ones the US Navy uses in their pressurized water reactor systems. The radioactive water flows through the tubes and the ones I have worked on were about the same but the overall bundle was shorter. I was part of a crew that plugged 6 tubes in one of the tube bundles on the USS Enterprise while off the coast of Vietnam in 1971 or there abouts. The real worry was getting radiated when you stuck the upper half of your body in the hole so you could work!

Oh yeah, we continued flight ops and bombing the VC while we did the plugging job too!