I feel bad for the Chinese. They are getting irradiated metal without knowing it. There is going to be a lot of pain sickness and suffering caused by this scavenging even thought it will probably never be traced back to Kazakhstan.
For example, suppose it captures a neutron. Copper has two natural isotopes, copper-63 and copper-65. Copper-64 has a half-life of hours, and decays into Nickel-64 or Zinc-64, both of which are stable and occur in nature. Copper-66 has a half-life of minutes, and decays into Zinc-66, which is stable and occurs in nature.
But maybe it didn't capture a neutron. And there might be impurities in the copper that are dangerous when irradiated. Or maybe it was physically contaminated with dangerous isotopes of another element.
Just saying that it was "irradiated" doesn't give us enough information to tell what actually happened.