Advantages of Nuclear Fission
- Small amount of U-235 can produce large amount of energy while burning of fossil fuels produces much less energy.
- Once a nuclear fuel is loaded into a nuclear reactor, it will go on liberating energy for two to three years at a stretch whereas fossil fuels have to be refilled at short intervals in thermal power plant.
Disadvantages of Nuclear Fission
- Nuclear fission emits very harmful radiations which causes serious like cancer and leukemia.
Safety Concerns associated with Nuclear Power
It is important to note that in a nuclear power plant, the uranium chain reaction is controlled. Therefore, a nuclear reactor cannot explode like an atomic bomb. This is because a nuclear bomb requires an uncontrolled chain reaction with highly-enriched uranium fuel. Uranium is a very heavy naturally-occurring element. Being an element, it can exist in different forms known as isotopes. Isotopes are different forms of the same element that contain different numbers of neutrons in their nucleus. The isotope U-235 is important because it can be used in the nuclear fission chain reaction to create a lot of energy.
Unlike the uranium used in a nuclear bomb, which is about 90% enriched with the isotope U-235, the uranium used in a nuclear reactor is only slightly enriched, to about four or five percent. This limits the amount of neutrons available for the fission chain reaction. Also, the chain reaction within the core of a nuclear reactor is controlled by control rods that absorb neutrons to control the rate of reaction. A nuclear bomb does not utilize control rods and, therefore, is an uncontrolled chain reaction.
A meltdown is an accident in which severe overheating of the nuclear reactor results in the melting of the reactor’s core. A meltdown could occur if there was a defect in the cooling system of the reactor that allowed one or more of the nuclear fuel elements to exceed its melting point. If a meltdown occurred, a nuclear power plant could release radiation into the environment.
The biggest concern associated with a nuclear power accident is the negative effects that exposure to radiation can have on the human body. It is interesting to note that we are exposed to radiation naturally just by living our lives. Natural background radiation comes from outer space, and even radiates up from the ground below us. You may also have been exposed to a medical procedure, such as a CT scan, X-ray or nuclear medicine, such as an MRI, that utilized different types of radiation to diagnose problems or treat a disease.
For most people, the low-level exposure to radiation that comes from the environment and medical procedures does not result in any detectable health problems. However, if a person were exposed to significant amounts of radiation over a period of time, this exposure could damage body cells and lead to cancer. If a person were to be exposed to an acute dose of high-levels of radiation, the result would be radiation sickness. Radiation sickness is defined as illness caused by exposure to a large dose of radiation over a short period of time. Symptoms may include skin burns, nausea, vomiting, diarrhea, hair loss, general weakness and possibly death.
In addition to personal health concerns, there are also environmental health concerns associated with nuclear power generation. Nuclear power plants use water from local lakes and rivers for cooling. Local water sources are used to dissipate this heat, and the excess water used to cool the reactor is often released back into the waterway at very hot temperatures. This water can also be polluted with salts and heavy metals, and these high temperatures, along with water pollutants, can disrupt the life of fish and plants within the waterway.
But perhaps the biggest challenge that comes with nuclear power is how to deal with the disposal of the radioactive waste that is generated during nuclear fission.
Reactor safety Systems
Nuclear rectors are constructed so that there are multiple barriers between the radioactive material in the core and the outside of the plant. This is the first level of many levels of safety system for reactors. The first barrier is the fuel itself. The ceramic fuel pellets are sealed into metal tubes, which are assembled into racks of tubes. The second barrier is the heavy steel reactor vessel, about 20 to 30 cm thick, and the primary cooling water system piping. The third barrier is a containment building inside which the reactor vessel rests.
The Nuclear Regulatory Commission (NRC—as the old Atomic Energy Commission, or AEC, is now named) demands three levels of safety: 1. Maximum safety in normal operations. 2. Backup safety systems to minimize the effects of possible accidents.
Additional safety systems in case the safety systems in the second level fail when an accident occurs. Second level backup includes, for example, the provision for onsite electric power systems to run pumps in case of loss of offsite power and systems to carry out a SCRAM (quick automatic shutdown of the reactor). Third level backups include an emergency core cooling system (ECCS) designed to deal with a loss-of-coolant accident (LOCA), also known as a core melt. The ECCS is a system of pumps, valves, and pipes independent of the normal reactor cooling system. The ECCS can pump high pressure water into the reactor during operation. There are also low pressure systems to pump water at lower pressures that could put water into the reactor safely if a cooling water pipe broke inside the reactor and allowed pressure inside the reactor to drop.