Is there an option so no one uses nukes?
Is there an option so no one uses nukes?

well... in theory you can do the following
go to the mods folder for DH full, go to DB and to building something txt file. open that file and find the nuclear reactor. you could simply ramp up the buildtime of that to 5000 so that noone can build it.
or better yet make an event that enables the nuke command and make the AI Chance = 0 and hey presto! no more nuking. You should remove the command nuke from the tech file else it won't work.
Darkest Hour Helpful Links:
How to modify the Darkest Hour Technology Tree:
http://forum.paradoxplaza.com/forum/...-the-tech-tree.
A collection of Blank Graphic files for Darkest Hour.
http://forum.paradoxplaza.com/forum/...lank-Gfx-files

my way is easier XD!
What I do to turn off nukes if I want to, is edit the save game to have the USA's max reactor = 0. No reactors, no nukes. This way it only affects that specific save game.
Mod:
Byzantium - Imperial Restoration for Darkest Hour
Latest version: 1.4, Patch 1.3 RC2 compatible, released 28.10.2012
AAR:
The Nazi Time Machine - A Strange Story of the First Reich (CK2) Dead due to save game corruption. Will restart eventually.

then reduce the IC cost to 1 then. besides, you use the one example where horrendous amounts of IC for no gain is what the US does best.

to be honest, i think nukes should be an event or a decision until/unless the devs can make it so that nuke equipped countries don't just use them like crazy. i mean, am i the only one who doesn't like to see the us nuking places in iran? africa? paris(when german controlled), or just random tiny cities?? should be some sort of event IMO.
Modern Day Scenario used Nuclear Option events for nuclear powers that were losing a war. If, say, USA had occupied a certain portion (I think 80%) of China, the latter would get event to use nukes. If I recall correctly enabling nukes also enabled them for everyone else.
Mod:
Byzantium - Imperial Restoration for Darkest Hour
Latest version: 1.4, Patch 1.3 RC2 compatible, released 28.10.2012
AAR:
The Nazi Time Machine - A Strange Story of the First Reich (CK2) Dead due to save game corruption. Will restart eventually.
What i always do, is deleting the nuke techs in the technology folderthat is easy, and then you are sure that the ai don't waste ic on reactors.
edit: It is not at all game breaking.
"Man is condemned to be free" Jean-Paul Sartre
Why remove nukes? They are the most fun part of the game. Boom, BOOM!
Mod:
Byzantium - Imperial Restoration for Darkest Hour
Latest version: 1.4, Patch 1.3 RC2 compatible, released 28.10.2012
AAR:
The Nazi Time Machine - A Strange Story of the First Reich (CK2) Dead due to save game corruption. Will restart eventually.

@Lord Finnish, I remember that too and thought it was a great idea. Keeps the world from becoming radioactive too quickly.
"Was your court at the trial of Visser constituted in any way like this, what rule did you shoot him under?"
"Like this?? ... oh no sir, it was not quite like this... no no sir, it wasn't quite so handsome...and as for rules... we didn't carry military manuals around with us... we were out on the veldt fighting the Boer the way he fought us.... I'll tell you what rule we applied sir, we applied Rule Three-OH-Three .... we caught them and we shot them under Rule Three-OH-Three!!!!"

hahaha! in my latest game in NWO, the US allied with Iran and nuked the kurish capital...