Simulating explosions helps determine maintenance for nuclear warheads?
I would bet they were more likely trying to make a "nuclear" weapon without radiation/fallout and failed.
I wonder what the world would be like with really cheap power though - I'd like to think a better place to live but more likely there would be a lot more war since the energy to do it would then be cheap.
Yes. Radioactive material is, by definition, slowly becoming non-radioactive by decaying into other atoms. You can think of those other atoms as 'contaminants' in your plutonium soup.
What this means is if you create a nuclear warhead, and put it on the shelf, if you did nothing you would have a very sophisticated box holding some lead. But long before that it stops working as a nuclear warhead.
So what you do is you take put one on the shelf in the lab and you sample it periodically to see how its content has changed, and run your simulations to see if plutonium or uranium with those makeups would still work within the boundaries of the device, and you try to test it periodically under conditions that simulate, as much as possible, an actual explosion.
They used to do this at the test site, basically explode one warhead from a batch every 2 - 3 years to insure they still worked. But they stopped when we banned such testing.
Additionally, radioactive decay releases Helium gas (alpha particles) over time which will lodge in the crystalline structure and cause disruptions over time.
Either of these factors can result in a change in the reliability and yield of nuclear warheads kept in storage for a long period of time.
The traditional and easiest way of doing that is to frequently build new warheads, and test explode the older ones. That is expensive and, nowadays, forbidden/frowned upon (I think the test ban treaty hasn't been ratified)
So, one stops building new ones and ends up with thirty+ year old warheads. The radioactive materials inside them have aged, steel may have become brittle, etc. To ascertain whether these devices still work, tests are needed. You could do them on the devices themselves, but it is easier and cheaper to do an experiment with a few grams of radioactive materials than to work with a kg or so from a warhead (all IIRC; corrections welcome)
It's not completely unreasonable: they need to validate the computational models that are used to check if an aged nuclear weapon will explode.