Owning radioactive land probably isn't the goal.

Besides, it sounds like a dumb rumor. Russia has been aiming for (and some say achieved) control of the north pole for transport purposes. What would they need Alaska for?

Russia has plenty petroleum. In fact, it's about the only thing they have to export for significant income. Russia's "problem" has always been "how do we transport it to buyers?". There aren't a lot of shipping ports to send from.

This is why Ukraine has been significant to Russia since industrialization; it's the gateway to European customers with money. That is, as long as the pipelines remain entact.

Trying to take Alaska, without taking the entire US would be an immediate fail. If they have to fight the US, it would make more sense to take all 52 😜 states instead of just one.