The weapon was created by a child of atom that wanted a more devastating radiation weapon. upon finding flamer fuel that contained extremely high levels of radiation he modified a standard flamer to vaporize this new fuel and blast clouds of dangerous radiation.

To find this new weapon head to sentinel site then go west and search for the subway pictured above.

I have added the rad tanks to the flamerammo loot table so it should appear on people that have the flamer.
The mod also adds a small custom dungeon where the caster is found and it can also be used as a settlement with the added workbench.

This weapon has a few features
It does ONLY radiation damage so the children on atom have a resistance to the weapon but they are NOT immune.
Humans fall to this weapon with ease.
Ghouls are healed if you shoot them with this weapon.
NOW the fun one, if you kill a ghouls without taking off its head or legs you can shoot the corpse with this gun and it will revive as a temporary pet!.

CREDITS:

Sepherose (testing and configurations) http://www.nexusmods.com/fallout4/users/43182/?
Daonoijin (play testing)
Vaughn (play testing)