A dozen countries are expected to start producing electricity from nuclear power sources within the next few years, the director general of the International Atomic Energy Association (IAEA) Rafael Mariano Grossi said on Tuesday.According to IAEA calculations, it is necessary to double the number of nuclear reactors in the world - currently at about 400 units - to achieve the objectives of the Paris climate agreement, Grossi said at the World Nuclear Exhibition in Paris."We already have 10 countries which have entered the decision phase (to build nuclear power plants) and 17 others which are in the evaluation process," he said."There will be a dozen or 13 (new) nuclear countries within a few years," he added.Ghana, Kenya, Morocco, Nigeria, Namibia, the Philippines, Kazakhstan and Uzbekistan were cited by Grossi as potential new nuclear countries.