Just because a material has a everyday name, it doesn't mean that the original specification didn't have a chemical/mechanical/biological/radiological/whatever reason for specifying it.
If all the material property requirements were met with a commonly available product that didn't require an expensive supply chain, then that's great.
I suspect that originally somewhere in the nuclear disposal system, a group identified the need, a solution was found and a materiel was specified. Along the line or through the years, the REASON for that specification was lost to the end of the purchasing chain and the poor sod who orders the stuff was given a directive to "buy sustainably" and substituted the new material without being aware of the original intent.
That person probably wasn't even been aware of the use of the material - they may have though it was used in the kennels for the guard dogs. It's a nuclear material disposal site. Need to know is important. (1) The suppler wouldn't have known, either.
There's lots of complaints of expensive procedures and materials(2), but this is a perfect example of the need for a formal supply chain system with provable provenance. You may BUY a commonly available kitty litter to fulfill the order, but what arrives in the sacks will have to match the specification sheet.
1. Yes, this is irony. The accident may have been prevented if the purchasing officer knew what it was for. Then again, maybe not.
2. Ferrous hammers are a bad idea around strong magnetic fields. If you're in a lab with a MRI or similar and lots of delicate equipment, a hammer to undo the dog on a vacuum chamber had better be a very special hammer. The kind that you can buy today for less than a hundred bucks, but in the 60's had to be engineered from scratch. Thank someone else's R&D for the fact you can buy a (nearly) chemically inert, non-ferrous, non-sparking hammer for a pittance.