This is a non-story.Clay is radioactive. Some kitchen tiles from Mexico will peg your geiger counter.
Oil companies drill down through clay to reach oil.
They lay pipe through this clay to pump the oil through.
This pipe becomes tainted with radiation that would get regulators to close most American nuclear facilities (only because the radioactivity of a normal, healthy banana peel would likewise get a nuke plant closed).
Whoa. Oil company gets some old pipe stolen. Yeah, it's radioactive, but not dangerous to human health, and certainly not "weapons grade".
Unless some major details are missing from the report above, this is a non-issue.