I don't know if anyone has posted this link before. I know there has been similar posts on this topic, but I don't think I;ve seen this link before... http://www.rickrichards.com/ufo/UFO3.htm (see about half way down, in the section about the reactor) - Is this a random X-COM fan publishing misinformation, or something else?
The computer is more advanced than that. Its basically, point, press and shoot. It uses a laser range finder to range it, plots a dot onto the sight, the soldier puts to dot onto the target, pulls the trigger, and bang, the grenade explodes over it, showering it with shrapnel, casing fragments, and any other payload they care to load it with.