On the right is a map showing who has nuclear reactors and weapons , and who could have them . When a country starts making nuclear weapons , they become a nuclear power . Proliferation has been opposed by many nations with and without nuclear weapons , the governments of which fear that more countries with nuclear weapons may increase the possibility of nuclear warfare ( up to and including the so-called `` countervalue '' targeting of civilians with nuclear weapons ) , de-stabilize international or regional relations , or infringe upon the national sovereignty of states .