Simplify the following text for a Grade 9 native English-speaking person.
Original: Several NPT signatories have given up nuclear weapons or nuclear weapons programs . South Africa undertook a nuclear weapons program , allegedly with the assistance of Israel in the 1970s , and may have conducted a nuclear test in the Indian Ocean in 1979 , but has since renounced its nuclear program and signed the treaty in 1991 after destroying its small nuclear arsenal .
Simplified: Nations who sign the treaty , but are not nuclear weapons states , promise to not use their nuclear power plants to make nuclear weapons .