World's most successful non-proliferation programme disposed of 16,000 former Soviet nuclear warheads to generate 10% of US electricity for 10 years.

Will the expansion of nuclear power more countries have access to nuclear weapons?

It is true that the knowledge involved with making nuclear energy involves much of the same knowledge required in making nuclear weapons. Since the dawn of the nuclear age it has been tempting to think that we could put the genie back in the bottle and to rid humanity of this knowledge altogether.

But this knowledge is already out there around the world and is not likely to ever disappear. Thirty-eight countries now have the ability to develop a nuclear weapon within a decade or so if they chose to, and only 9 countries actually have nuclear weapons. That only two countries in the world are currently attempting to develop nuclear weapons, Iran and North Korea, is a testament to the effectiveness of the Nuclear Non-Proliferation Treaty. Both countries have civilian nuclear power plants, but neither are using their power plants to make a nuclear weapon. Iran is notoriously using thousands of centrifuges to refine pure uranium to a weaponized level of 90%, far above the 3% level used in nuclear power plants. Both countries are suffering crippling international sanctions for their illegal activities.
A little known fact is that civilian nuclear power is actually helping us to get rid of nuclear weapons. Thanks to international negotiations carried out by the Clinton Administration, 10% of American electricity (half of America’s nuclear power) currently comes from uranium derived from former Soviet nuclear warheads. Soon we’ll be turning America’s nuclear arsenal into electricity as well. With the advent of advanced reactors we will be able to forever rid the world of its stockpile of weapons grade plutonium by transmuting it in the process of generating electricity.
These are promising developments, but it does not completely obviate the fact that certain countries are not ready to be given access to nuclear technology for a variety of reasons. Fortunately, the vast majority of CO2 is emitted by the very same nations that already have nuclear weapons.
If they alone made a big push to decarbonize their energy sector using nuclear power we would be a long way towards solving the climate crisis. As other developing nations advance, they too could one day employ nuclear power under the same strict international controls that have so far proven remarkably effective at preventing weapons diversion. In short, we don’t need to employ nuclear energy everywhere in order to dramatically reduce CO2 emissions.