Cadmium is a chemical element with an atomic number of 48 and the symbol Cd. Cadmium is a metal that has traditionally been used for various industrial purposes, including controlling nuclear fission reactions. Cadmium has been utilized against kaiju in various films.
To halt the rampage of the monster Gamera, the J.S.D.F. developed a plan to bombard the monster with large amounts of cadmium, believing it will freeze him. Although Gamera was slowed down by the cadmium, he managed to fly away and recover.
When the Japanese government constructed the Super X in secret, they armed it with cadmium shells for the purpose of cleaning up radioactive fallout left behind in the case of a nuclear accident or attack. When Godzilla returned after 30 years and came ashore in Tokyo, the government decided to launch the Super X against him. Since Godzilla was believed to be a biological nuclear reactor, it was hoped that cadmium might slow down the nuclear reactions in his body and kill him. The Super X flew towards Godzilla and distracted him with flares, then fired cadmium shells down his throat when he roared. Godzilla's heartbeat began to slow and he grew weak. Finally, Godzilla collapsed sideways against a building, apparently dead. Meanwhile, the Soviet Union had accidentally launched a nuclear missile at Godzilla, which was headed right to the heart of Tokyo. The United States launched their own nuclear missile at the Soviet missile, detonating it in the atmosphere above Tokyo. However, this caused a radiation storm that revived Godzilla, allowing him to overcome the cadmium in his system. Godzilla then reengaged the Super X in battle, then destroyed it by toppling a skyscraper onto it.
By the year 1996, the J.S.D.F. and G-Force had collaborated to construct a new Super X, the Super X3. This warship was designed with only freezer weapons, including an ultra-low temperature (ULT) maser beam and cadmium shells. After it was discovered that Godzilla's heart was overloading and that he would soon explode and destroy the world, it was decided to send the Super X3 against him when he appeared in the Bungo Channel, heading for the Ikata Nuclear Power Plant. The Super X3 attacked Godzilla in the channel, bombarding him with cadmium shells to reduce his nuclear power. The combination of the ULT lasers and cadmium shells reduced Godzilla's core temperature and caused him to be encased in ice. With the mission successful, the Super X3 returned to its base.
Meanwhile, the crustaceans that had been mutated by the Oxygen Destroyer were terrorizing Tokyo. Dr. Kensaku Ijuin concluded that extreme cold would liquefy the micro-oxygen in their bodies and kill them. G-Force deployed a platoon of DAG-MB96 Maser Cannons armed with ULT lasers as well as Type 90 Tanks armed with cadmium shells to engage the creatures. While the attack seemed effective at first, the creatures converged into a gigantic monster that Ijuin named "Destoroyah." Destoroyah fought back, destroying large amounts of the military forces before flying away.
Later, when the soon-to-meltdown Godzilla battled Destoroyah's final form at Haneda Airport, Ijuin developed a plan to use all of G-Force's capabilities to freeze Godzilla as he melted down, hoping it could minimize the damage and prevent the apocalypse. When Godzilla's temperature reached critical levels, Destoroyah tried to fly away but was brought down by G-Force's freezer weapons and destroyed when he collided with the super-heated ground. His enemy destroyed, Godzilla began to melt down, and G-Force opened fire with all of its ULT lasers and cadmium shells. These freezer weapons successfully froze Godzilla as he melted down, preventing him from burning down to the Earth's core. However, they did not prevent catastrophic levels of radiation from being released into the air. Thankfully, the previously dead Godzilla Junior absorbed the excess radiation and grew into a new Godzilla, saving the world.