Simplify the following text for a Grade 11 native English-speaking person.
Original: The IAEA now operates a safeguards system as specified under Article III of the Nuclear Non-Proliferation Treaty ( NPT ) of 1968 , which aims to ensure that civil stocks of uranium , plutonium , as well as facilities and technologies associated with these nuclear materials , are used only for peaceful purposes and do not contribute in any way to proliferation or nuclear weapons programs . It is often argued that proliferation of nuclear weapons to many other states has been prevented by the extension of assurances and mutual defense treaties to these states by nuclear powers , but other factors , such as national prestige , or specific historical experiences , also play a part in hastening or stopping nuclear proliferation .
Simplified: Nuclear proliferation is when a country starts making nuclear objects .