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All countries that have exploded nuclear devices have exploded their first devices. The USA was the first to detonate such a device and the only country to use nuclear warheads in combat. The most recent countries to test nuclear devices are India, Pakistan, and North Korea.
The United States was the first country to use nuclear power for electricity generation, with the first nuclear power plant going online in 1957 in Shippingport, Pennsylvania.
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Japan
The first use of plutonium was as nuclear weapon; United States was the first country to use these weapons against Japan.
Yes, China's first nuclear test took place in 1964, and they have roughly 200 warheads at this time; depending on who you ask. China also has a "no first use rule" meaning that they will only use nuclear weapons in retaliation.
During world war 2, the United States finished making them. They were first to have a nuclear bomb and the only ones to use it againts mankind.
The only actions of consequence would be the 2 Atomic Bombs dropped on Hiroshima and Nagasaki in 1945. The USA are also the only country ever to use a Nuclear device against an Enemy country.
A nuclear reactor will do what is asked here. Use the link below to the related question about what a nuclear reactor is.
The use of a nuclear weapon on a country would be considered devestating, dependant on the payload and method of delivery of the nuclear device. It can destroy cities, and make the land infertile for many years afterwards please look towards Nagasaki and Hiroshima for more information. The "effect" of nuclear weapons on a country would depend on what your perspective is: there is something called MAD (Mutually Assured Destruction) of which the cold war is an example, where the development of a nuclear arsenal by one country (USSR) was profilgate in the development of a nuclear arsenal in another country (USA) this happened in many countries. Currently the body which is responsible for monitoring nuclear arsenals is called the IAEA (Internationl Atomic Energy Agency)
Which President? US or UK. Since US is the first country to use nuclear weapons, then I assume that you are asking who was the US president during world war two while nuclear testing? Answer: Truman.
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