Warp core breach
A warp core breach, or warp drive containment breach, was a catastrophic failure of a starship's warp core.

Description
A breach could occur in a variety of ways, but was frequently characterized by a coolant leak from the main reaction chamber, resulting in a runaway reaction within the warp core. Antimatter containment was lost, and the resultant contact between antimatter and the normal matter of the ship destroyed the vessel.

Consequences and prevention
The breach was almost always irreversible, as most safety protocols and systems would have failed prior to the event. Warp core ejection was a common method of dealing with a breach, although this was considered a last ditch effort and often failed aboard. The evacuation of the crew to the primary hull and initiating separation was also used in cases where the vessel had that capability, such as on Galaxy-class vessels. In situations where a saucer separation could not be initiated, then evacuation of the ship via escape pods or shuttles would occur. Regardless, the aim was to get as much distance between the core and the crew as possible before detonation. In the case of saucer separation (or warp core ejection), the ship was left running on impulse power and batteries, as the warp core and warp nacelles were required for warp drive.

Occurrences
In 2259, La'an Noonien Singh tried to blow up the Starship Enterprise by shutting down the antimatter containment field in the warp cire while she was infected with an Illyrian virus. Una (Number One) was immune to the virus and was able to stop La'an and reactivate the containment field.

In 2267, Khan Noonien Singh tried to blow up the starship  by overloading the warp core when he failed to capture it. James T. Kirk stopped him and the overload in time. ()

In 2365, the  had been scanned by the Iconian probe orbiting the planet of Iconia in the Romulan Neutral Zone. After the Yamato rendezvous with her sister ship the , the energy build up in the engineering section by the Iconian scan overloaded the warp core. ()

In 2368, Commander Riker remembered a containment breach situation in main engineering due to a telepathic memory invasion by the Ullian Jev. Ensign Keller died during this event. ()

In 2368, the Enterprise-D collided with the  after encountering a space-time distortion in the Typhon Expanse, causing a warp core breach which destroyed the ship. The explosion led to the creation of a temporal causality loop, from which the Enterprise was able to avoid the collision before it happened. ()

In 2369, the Enterprise-D was destroyed by a warp core breach, generated by a massive energy feedback into the warp core from a power transfer to a Romulan vessel. The core breach was averted when time reset itself and Captain Picard remotely steered a runabout into the transfer beam. ()
 
In 2371, the engineering hull of the Enterprise-D was destroyed in a warp core breach caused by a coolant leak following rupture of the magnetic interlocks due to an attack by a D12-class Bird-of-Prey. The ion shock wave created by the explosion of the vessel's stardrive section caused the vessel's saucer section to be disabled and crash-land on Veridian III. All hands survived, but the vessel was a total loss. ()

In early 2372, as a result of a subspace inversion of the Bajoran wormhole, the  was under threat of a core breach, with the ejection system disabled. Benjamin Sisko was able to shunt the excess power over to the deflector array with the help of an interphasic compensator, averting the breach. ()

In 2374 during a test of the Borg transwarp drive aboard the , tachyons got into the warp core and almost caused a warp core breach. B'Elanna Torres was able to eject the warp core and evacuate engineering. ()

In circa 3069, much of the Milky Way Galaxy's dilithium suddenly went inert in an event known as the Burn, which resulted in any starship with an active warp core losing antimatter containment and exploding. Millions of people were killed in this event. ()

In 3189, the crew of the  implemented a purposeful overload of their warp core and then ejected it into the Viridian. While the Discovery escaped via its spore drive, the breach of the ejected warp core destroyed the Emerald Chain flagship. ()

Risk factors
Nucleonic particles from a polaric field flooded the intake manifolds of  in 2153, causing an injector flare that could have caused a warp core breach.  sustained life-threatening injuries during a manual shutdown of the reactor to prevent the breach. ()

Antineutrinos tended to have a neutralizing effect on warp core containment fields of Federation starships. A Sikarian spatial trajector field, utilizing antineutrinos, nearly caused a warp core breach on the . () One of the USS Voyagers shuttlecraft, the , was destroyed by a warp core breach in 2374. Its occupants, B'Elanna Torres and Tom Paris, had to don environmental suits and beam into open space to await rescue. ()

The reaction of veridium isotopes with warp plasma would cause a warp core breach. This led to the near destruction of the  in 2377, although the warp core was successfully ejected into a class J nebula before the explosion could destroy the vessel. ()

If a large number of tachyons leaked into a warp core, a warp core breach was almost certain to occur, as a result of the tachyons creating a resonance frequency causing the core pressure to increase out of control. ()

Deliberate initiations

Warp core breaches were occasionally performed deliberately; they were most often used as the primary means of fulfilling a starship's auto-destruct sequence. 

Q purposefully caused the core aboard the Enterprise-D to breach in 2369 (so that, if he was right and she was in fact a , Amanda Rogers could prevent it), and Geordi La Forge caused a breach of the 's warp core in 2375 to seal a subspace tear caused by an isolytic burst (the core having been ejected from the ship prior to detonation). (; )

In 2258 of Nero's alternate reality,  ejected and detonated the warp cores of that timeline's  and the resultant explosion pushed the ship free of the black hole consuming the Narada. ()

To demonstrate the damaging effects warp drive were having on subspace, Serova took her ship out into the Hekaras Corridor and intentionally overloaded her warp engines, causing a core breach that killed her and destroyed her ship. The resultant burst of warp energy proved her theory by creating a subspace rift. ()

Farrakk was killed by a warp core breach when Hagath had his ship sabotaged in 2373. ()

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