Thorium charges were high-explosives used for demolitions. A thorium charge was more powerful than a comparably-sized thermal detonator.
Akkere had some in his possession in 3951 BBY, and may have sold them to the Jedi Exile. Some were also carried by contractors who explored the Sith Academy on Korriban.
The player character in Star Wars: Knights of the Old Republic II: The Sith Lords can obtain thorium charges from Akkere through dialogue near the end of the Dantooine mission or by killing the merchant, and can find them on Korriban accompanied by a datapad highlighting their destructive nature. The charges are in a nearby footlocker, and if the player character chooses to "bash open" the footlocker instead of cracking its lock, the thorium charges detonate, causing damage to all party members nearby.
The player character in Star Wars: Knights of the Old Republic II: The Sith Lords can obtain thorium charges from Akkere through dialogue near the end of the Dantooine mission or by killing the merchant, and can find them on Korriban accompanied by a datapad highlighting their destructive nature. The charges are in a nearby footlocker, and if the player character chooses to "bash open" the footlocker instead of cracking its lock, the thorium charges detonate, causing damage to all party members nearby.