Cracked rods can release radioactive iodine into the water that surrounds and cools the fuel rods. There, it circulates with the cooling water throughout the system, ending up in the airborne, liquid, and solid wastes from the reactor. From time to time, reactor gas capture systems release gases, including iodine, to the environment under applicable regulations. Anywhere spent nuclear fuel is handled, there is a chance that iodine-129 and iodine-131 will escape into the environment. Nuclear fuel reprocessing plants dissolve the spent fuel rods in strong acids to recover plutonium and other valuable materials. In the process, they also release iodine-129 and -131 into the airborne, liquid, and solid waste processing systems. In the U.S., spent nuclear fuel is no longer reprocessed, because of concerns about nuclear weapons proliferation. Currently, spent nuclear fuel remains in temporary storage at nuclear power plants around the country. Wherever spent nuclear fuel is stored, the short-lived iodine-131 it contains will decay away quickly and completely. However, the long-lived iodine-129 will remain for millions of years.