An estimated 160 TBq (about 250 kg) of technetium-99 was released into the environment up to 1994 by atmospheric nuclear tests. The amount of technetium-99 from civilian nuclear power released into the environment up to 1986 is estimated to be on the order of 1000 TBq (about 1600 kg), primarily by outdated methods of nuclear fuel reprocessing; most of this was discharged into the sea. In recent years, reprocessing methods have improved to reduce emissions, but  the primary release of technetium-99 into the environment is by the Sellafield plant, which released an estimated 550 TBq (about 900 kg) from 1995&ndash;1999 into the Irish Sea. From 2000 onwards the amount has been limited by regulation to 90 TBq (about 140 kg) per year.