During the nuclear fission process, Gamma rays are produced. In conjunction with the many extra neutrons in the core, this is the radiation of public concern. Neutrons lack charge, allowing them to penetrate matter very deeply. Additionally, because of its electromagnetic properties, the high energy Gamma rays penetrate matter just as well. Both are best stopped by extremely thick layers of concrete or liquids like water. Gamma rays and neutrons, because of their penetrating depth, can have severe effects on human cells. Safety Today’s safety at our nuclear power plants is considered our number one priority. Efficient training is conducted on plant operations and radiation awareness because of the intrinsic nature nuclear fission encompasses. Clean, environment friendly power is what we generate and our safety regulations are second to none. Welcome again to Exelon!  Copyright: June 9, 2008 Jason Fisher Safety, Integrity, Diversity, Respect, Accountability, Continuous Improvement Exelon operates the largest nuclear fleet in the nation and the third largest fleet in the world, which represents approximately 20 percent of the U.S. nuclear industry’s power capacity. Referred as “Top Utility in the World” by Platts and “Best in Breed” by Forbes, we manage 17 nuclear reactors in the United States, outputting an astounding 17,500 megawatts. Having joined Exelon, you’re building a more sustainable future and creating a brighter tomorrow by planning better energy generation today. Safety, Integrity, Diversity, Respect, Accountability, Continuous Improvement Welcome to Exelon In today’s world of high energy demands in combination with projections of diminishing oil reserves, alternative sources of energy are needed. Not only are they needed to reduce energy costs, but to save our environment from the massive air pollutants of fossil fuels and coal. As a fairly simple idea, nuclear power is an answer. Here at Exelon, we thrive on producing clean energy via our nuclear facilities. Types of Reactors At Exelon, our nuclear power plants are designed to operate based on one of two general design types, the PWR [pressurized water reactor], or BWR [boiling water reactor]. As the more commonly used design, the PWR has two main water cycles. The first is inside the core, which is highly radioactive. This waters heat is transferred via a heat exchanger to non- radioactive clean water in the second cycle. It is this clean water that is used to power the turbine in the form of steam. The BWR has only one water cycle. It is the radioactive water that powers the turbine. Over time, this makes the turbine radioactive which demands more complicated procedures when dismantling the reactor. However, an advantage the BWR has over the PWR is that the core can be kept at a lower pressure, making it more efficient. Nuclear Fission Inside the core, heat is generated from the fission, or splitting, of atoms. The principle element used in nuclear reactors is Uranium. When a stray neutron strikes the Uranium atom and is absorbed, Uranium 235 becomes Uranium 236. Uranium 236 is highly unstable and thus causes the atom to split. After splitting, two additional neutrons are released, which starts a chain reaction of splitting other atoms. The chain reaction is controlled by lead rods located within the reactor. The lead rods are inserted and retracted inside the core to absorb the amount of neutrons causing the numerous reactions taking place. The heat generated from the nuclear fission is removed via a circulating coolant. The hot coolant is used to boil water which generates steam. The steam is then used to power a turbine generator, thus producing electricity. What is Radiation? Radioactive decay is a natural process. An atom of a radioactive isotope (same atoms of an element, each a different atomic weight) will spontaneously decay into another element through one of three common processes:  Alpha decay  Beta decay  Spontaneous fission In the process, four different kinds of radioactive rays (Radiation) are produced:  Alpha rays  Beta rays  Gamma rays  Neutron rays Alpha particles comprise of 2 protons and 2 neutrons. Because of their large size, they don’t penetrate matter very well. Beta particles are essentially electrons and can penetrate matter a bit further than Alpha particles. Both are not dangerous to humans unless ingested.