Cold fusion device
A cold fusion device was a type of technology that initiates a cold fusion detonation.

In 2259,  activated a cold fusion device in an erupting volcano on the planet Nibiru. Use of the device successfully caused a detonation which rendered the volcano inert, causing lava to congeal into enormous pinnacles of rock. ()

Background information 
The cold fusion device in Star Trek Into Darkness turned out to be the most difficult prop in the entire film to design. Many concept drawings were done during this process and plenty of discussion revolved around the appearance and functionality of the volcano-terminating device. "The challenge was to find something that looked like it could do that, make it in a suitcase size, and make it look like it was part of the Star Trek world. We went round and round," recalled Prop Master Andrew Siegel, who began work on the film after some initial illustrations of the mechanism were already created.

One central issue was how to make the imaginary cold fusion device relatable on-screen. "To start with, you have to find a case, or make a case, that looks like Spock could have grabbed it off the shelf of the Enterprise," Siegel continued. "Is it something that he put together? Obviously, Starfleet probably doesn't give you a volcano deactivation device." The next design consideration was likewise trying to make it instantly clear to the viewer what the device actually was, by the way the machine looked. Siegel further commented, "We have the added attraction of, 'Okay, now it's going to break on impact, and Spock has to do something to fix it.' Again, the audience has to be able to relate to that and go, 'Oh, it's like when my refrigerator broke, and I stuck a wedge in the door.' As a nod to the diehard fans, one of the ways that he fixes it is by plugging his tricorder into it, which I thought was super cool." This method of repairing the cold fusion device added an additional degree of functionality to the tricorder. ()

The cold fusion device was referred to as a "Rankine nullifier" in the ization of .

See also
Fusion bomb
Alternate reality
Explosive weapons