All they had to say is "use this SKU kitty litter ONLY, nothing else. Here's the link. Do not buy anything else or you can cause a massive disaster. Here's a picture of the bag. Any deviation from this must be approved by a domain expert."

In other words, when failure is not an option you have to engineer out failure vectors. This was stupid simple to prevent. I don't see it as a failure of the workers, they don't know any better.

As an example, in aerospace you vet and qualify every single material through Material's Engineers. Only materials that have been approved for a particular use are designed into an assembly. It would be inconceivable for an assembly technician to order an alternative adhesive from a random catalog. This is proper engineering.

It sounds like the folks running the nuclear waste installation had no idea how to manage a mission critical process.