The Nuclear Non-Proliferation Treaty was signed by 43 members between 1 July 1968 and 5 March 1970.
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Today eight countries are in possessionn of nuclear weapons. The five nuclear weapons states United States, Russia (former Soviet Union), United Kingdom, France and China, are the only countries allowed to have nuclear weapons according to the Non-Proliferation Treaty (NPT) from 1970. All members of the United Nations except Israel, India and Pakistan have signed the NPT.
The last U.S. above-ground (atmospheric) test was in 1963. The last U.S. underground test was in 1992. The Comprehensive Test Ban Treaty (signed by many major powers) ended testeing of all kinds, atmospheric or underground, in 1992. The U.S. models (with supercomputers) characteristics of nuclear weapons 'explosions' in order to 'test' its weapons designs.
Indonesia hasn't signed or ratified the Nuclear Nonproliferation Treaty. Even though they use nuclear power they don't have any nuclear weapons that we know of.
The Treaty on the Non-Proliferation of Nuclear Weapons, also know as the Nuclear Non-Proliferation Treaty or NPT.
SALT Strategic Arms Limitation Treaty
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South Korea is a party to the Nuclear Non-Proliferation Treaty (NPT) as a non-nuclear weapons state. Its safeguards agreement under the NPT came into force in 1975 and it has signed the Additional Protocol in relation to this. (source: http://www.world-nuclear.org/info/Country-Profiles/Countries-O-S/South-Korea/#.UUh09hzHF2A)
There is a number of countries that signed the treaty but nobody knows how safe we are against nuclear weapons.
Israel, as they refuse to acknowledge they have the weapons; and North Korea.
The Communist government of China was outraged when the USSR and the USA signed the famous test ban treaty regarding nuclear weapons. One main charge of China was that the USSR signed this treaty with the USA in order to prevent China from obtaining nuclear weapons.
i put how nuclear weapons are spreading,
no (at least not that we know of). However their uranium resources have been utilized in the manufacturing nuclear weapons (though the mine that supplied uranium has been closed since 1960). There are some concerns of illegal mining activity, but they do not pose a major threat in the issue of nuclear programs. Democratic Republic of the Congo signed the Comprehensive Nuclear Test Ban Treaty, the Nuclear Non-Proliferation Treaty and also has signed but not yet ratified the African Nuclear Weapons Free Zone (Treaty of Pelindaba). just google it (: