Iran wants nukes for one reason: to use them.
Iran is ruled by the Twelver sect of Shiite Islam. They believe that only by the deaths of millions upon millions will the scent of so much blood draw the 12th Imam out of the well he climbed into 600 years ago, who upon emerging will lead the way to bring all of humanity to Paradise - effective extinction.
The Twelvers give a rat’s patoot about nuclear energy, or runaway reactors; they only want millions to die so their religious vision will come to fruition. Their deaths and the deaths of their population is to be expected and welcomed as that will help lead the way to the 12th Imam.
And yes, they are effectively insane from a Western point of view, but not from an Islamic point of view.
“...only by the deaths of millions upon millions will the scent of so much blood draw the 12th Imam out of the well he climbed into 600 years ago...”
You are correct. That well is in back of a certain Mosque and they believe the Imam is down that well. He will only come out when there is great devastation so their religious leaders want to bring about that devastation to get the Imam out of that well. That is why they want nuclear bombs. The first one will be for Israel and the next one for us.