Lets see: you have ten pounds of beef that measure at 1600 counts per minute (cpm) but allowable radiation level is 50 cpm, a little above background. So you grind up that ten pounds with 400 pounds of uncontaminated meat, and end up with 410 pounds of hamburger that measures below background.
From the radiation standpoint, this does not place anyone in danger. From the heavy metals standpoint, this may or may not be a problem; there is not enough evidence to make a determination. Regardless, it is highly unethical to take such action.
In any case, I would not expect Soviet officials would have been punished for doing such a thing. My impression was that the Soviet political class could get away with a lot.
Beef is not water to mix that well. Also as much as I understand your disdain towards the Soviets it is supposed that some regular people have to do it and on a mass scale, not some looters stealing contaminated stereos and automobiles. Why would they?
I wonder if by mixing the irradiated meat with normal uncontaminated meat the Russians inadvertently extended the shelf life of the meat by several weeks. Irradiation will extend the shelf life of meat and perishable products and I wonder if the same held for the Chernobyl products?