Very interesting, but there is only one way radiation can get outside the cask: it has a leak. Once a radioactive source gets sealed in a can, alpha and beta rediation cannot escape, gamma radiation can penetrate the metal, but the amount escaping must remain constant, i.e., it will neither increase or decrease. Just some percentage penetrates the metal and other than adding more metal, there's noting you can do to stop it.

The fact that they washed the container and temporarily reduced radiation levels indicates radioactive material (not "radiation") was leaking out, they removed it with the scrubdown. A while later radiation levels increased, which means more material leaked out.

There is a difference between radiation and radioactive material. Radioactive material emits radiation. You can contain radioactive material, and you can wash it off. You can also contain the alpha and beta particles it may be emitting because they cannot penetrate even the thinnest shielding. Gamma radiation can only be stopped by a lot of bulky shielding.

Without knowing the spectrum of the escaping radiation, it's difficult to know just what was going on, but it must have been a faulty container, the physics is very straightforward. There is no such thing as "generation of variable internal radiation" or "acting as a magnet for natural radiation in the environment" . Radiochemistry has been extremely well understood for decades, it forms the basis for a huge industry and is part of established routine lab technique. The principles are demonstrated easily in elementary science labs as part of the curriculum. In fact, I conducted experiments in shielding various types of radiation for my high school labs when I was doing my propaganda overseas.

Trust me on this, this science is very well understood.

BTW, I had Glasstone's "Sourcebook of Atomic Energy" as part of my classsroom materials. It is dull reading, but the chapters on spacecraft nuclear power sources and the NERVA atomic rocket engine were wonderful! You're right, reactor engineering has not progressed much since the 70s.

Come to think of it, except for improvements in digital circuitry and some advances in materials science and lasers, engineering really hasn't progressed much since the 70s. But that's material for another post.