That facility was a nuclear research facility for civilian, military and medical use. Note that military doesn't mean weapons. Iran getting nuclear submarine would increase their threat level. In any case, Iran have a fatwa against developing nuclear bombs (a fatwa is a law edicted by a religious leader, and not respecting it would make you sinful and rebellious, and in a theocratic regime, often end in prison). The fatwa isn't reversed yet afaik, but the US killed the mufti who declared it, so I don't know how it applies.

But anybody saying Iran was working on a bomb is probably misinformed or lying imho.