Sometimes other signs and symptoms precede sudden cardiac arrest. These may include fatigue, fainting, blackouts, dizziness, chest pain, shortness of breath, weakness, palpitations or vomiting. But sudden cardiac arrest often occurs with no warning.
In the core of nuclear reactors, the fission of uranium atoms releases energy that heats water to about 520 degrees Farenheit. This hot water is then used to spin turbines that are connected to generators, producing electricity.
Nuclear fission (division) of certain large unstable atomic nuclei results in usable energy. Nuclear fission also occurs in a nuclear bomb, but for nuclear energy the fission process is controlled and takes place in a nuclear fission reactor (Cattenom is pictured). There are various types of nuclear fission reactors. See references for details.