This statement is true. Among all the other sources of energy, nuclear energy from radioactive elements are the ones that create a very massive energy. Radioactive elements are unstable because they have high neutron-proton ratio. That's why they undergo nuclear reactions to reduce this ratio. As a result, they give off sub-atomic particles called alpha, beta, gamma and positron molecules. Because these particles have to be pulled out of the nucleus, it release great energy in the from of heat. This heat then turns the turbine so it could activate the generator to make electricity.
Use the equation I=V/R where I is current and V is the voltage plus R is the resistance so when voltage is the highest and resistance is lowest the current is the highest