Naquadria, a highly unstable radioactive variation of naquadah, has the potential to be an enormously powerful energy source. Even a very small amount emits a pulse of energy far greater than weapons grade naquadah, and when used as a weapon it has the potential to be as powerful as a naquadah-enhanced nuclear warhead.
Naquadria is a heavier, less stable isotope than naquadah, and it does not occur in nature. It was discovered on Kelowna, where ancient writings revealed that Thanos, the Goa'uld who had occupied the planet thousands of years ago, had been experimenting with the mineral. Thanos had managed to create a small amount of naquadria by developing a process to convert raw naquadah, but he had been killed in a cataclysmic event that nearly destroyed the planet 10,000 years ago. The resulting explosion released a massive bombardment of subatomic particles which triggered a chain reaction and catalyzed the conversion of a vein of naquadah near the planet's surface.
In 20,000 years, the converted naquadria would have decayed back into naquadah, however the Kelownans mined the mineral and began to research its use for weapons technology. When Dr. Kieran and his team of scientists successfully tested a naquadria bomb, its destructive power exceeded all expectations. However, subatomic particles from the explosion penetrated the planet's crust and triggered the conversion of a second, deeper vein of naquadah. As the conversion process traveled deeper underground, the heat and pressure increased until the highly unstable nature of the resulting naquadria threatened to explode and obliterate Kelowna. The process could not be reversed, however SG-1 cooperated with the Kelownans and used a deep underground excavation vehicle to deposit a small nuclear device near a minor fault line crossing the vein of naquadah in order to trigger a shift along the fault and isolate the advancing naquadria. The mission was successful, and Kelowna was spared.
Several hundred pounds of the mined naquadria had been acquired from Kelowna by the SGC for use in developmental hyperspace technology. The experimental X-302 craft was designed with naquadria-powered hyperspace generators, however, the instability of naquadria increases exponentially as more energy is extracted from it, and the X-302 was unable to maintain a stable hyperspace window. A more successful naquadria reactor module was designed for the X-303 Prometheus, enabling the ship to achieve hyperspace, however, the instability of the naquadria caused a power overload, and the reactor module had to be jettisoned, stranding the Prometheus near Tagrea until repairs could be made.
The SGC continues to pursue naquadria research for use in hyperspace, shield, and weapons technology. The Mark IX is a naquadria-enhanced nuclear warhead capable of a multi-gigaton detonation that could vaporize a stargate. It has been used by SG-1 on Kallana and to sever the wormhole connection between the Ori supergate and a black hole in the Pegasus Galaxy.
Long-term exposure to naquadria radiation can cause a unique form of brain damage with symptoms of paranoia, delusions, and hallucinations. The Kelownan scientists who worked on the Naquadria Project, including Tomis Leed and Jonas's mentor Dr. Kieran, all developed advanced schizophrenia due to improper shielding of naquadria during their research. It was also a lab accident involving the experimental naquadria weapon on Kelowna that exposed Daniel Jackson to lethal doses of radiation which took his life.
Cross Reference: Kianna Cyr, Deep Underground Excavation Vehicle, F-302, Hyperspace, Daniel Jackson, Kelowna, Dr. Kieran, Langara, Tomis Leed, Mark IX, Naquadah, P2S-4C3, Prometheus, Jonas Quinn, X-302