Nuclear Power Plant Safety System - Research Paper Example

Nuclear Power plant safety system Nuclear power plants have been and are still considered by the public as being extremely dangerous to use as sources of energy. This is due to the fact that they are associated with radioactive materials. These radioactive materials are too dangerous to be released into the environment due the fact their effect on humans and the land are usually dire, and may last for years thereby affecting generations. For example, radioactive materials (wastes) from nuclear power plants may cause cancer and radiation sickness to humans among others. Therefore, any leak or release of radioactive materials into the environment may render land that would have otherwise been useful useless. It is for this reason that extreme safety measures are normally adopted in nuclear power plants. The safety measures are normally taken to prevent any leak of the radioactive materials into the environment as a result of accident, breakdown and/or waste (INSAG). This paper therefore, aims at discussing the safety systems present in nuclear power plants’ reactors. The heart of a nuclear power plant is a nuclear reactor. It is in the reactor that those nuclear reactions (nuclear fusion or fission reaction) that produce heat energy (heat energy used to heat steam) take place. Therefore, all nuclear radiations are produced in the reactors as either leaks or wastes. It is for this reason that extreme systems are incorporated in these nuclear reactors. The objectives of nuclear reactor safety systems include: i. Shutting down a nuclear reactor. ii. Maintaining or carrying out repair works while reactor is shut down. iii. Preventing release of any radioactive materials or waste into the environment during accidents and/or events. (Nuclear Energy Agency) The above objectives of nuclear reactor safety systems are usually accomplished by use of a variety of equipment and machinery. These different equipment and machinery usually perform different specific roles in relation to nuclear power plant (reactor) safety (Nuclear Energy Agency). The safety systems and equipment that are usually available in all nuclear power plants include but not limited to following. Standby liquid control system or safety injection system In case nuclear reaction in the reactors is needed to be stopped urgently (as in the case of an accident) safety injection system can be used to bring the reaction to a halt. This is usually done by injecting a fluid (liquid) directly into the core of the reactor that usually absorbs the neutrons (INSAG). Basically, for boiling water nuclear reactors, the injecting liquid is usually a boron based solution, for instance boric acid. The boric acid (or any other boron associated liquid) is injected so as to displace water that is in the reactor core. It is, however, important to mention that this safety system is usually used in addition to the control rods. A combination of the safety system (safety injection system and control rod) increase concentration thereby stopping or slowing down the nuclear reaction (Amano and Sundén). The question that might be lingering in the mind of the reader is how control rod system works and how can it be used to control nuclear reaction. The next paragraph brief describes this control system. Nuclear reactor control rods Basically, control rods serve a variety of purposes in nuclear reaction such as controlling the rate of nuclear reaction as well as stopping nuclear reaction. As safety devices in nuclear power plants, they are inserted into the cores of nuclear power plants reactors to absorb neutrons, thereby bringing the nuclear reaction to a halt (INSAG). Control rods are usually made of elements (chemical elements) that have the capability of absorbing as many neutrons as possible without themselves being fissioned (disintegrated). These chemical elements include: cadmium, silver and indium among others. If control rods are either inserted into or removed from the core of reactor, they control (regulate) nuclear reactor’s neutron flux (Nuclear Energy Agency). Neutron flux can be defined as the decrease and or increase in the number of neutrons that split uranium atoms further. The consequent result of regulating neutron flux is the regulation of the nuclear reactor’s thermal power, amount of steam that is produced, and finally the amount of electric energy produced (Amano and Sundén). ECCS (Emergency core cooling system) Another essential safety system in nuclear power plant is ECCS (also known as the Emergency core cooling system). This safety system is designed or made to shut down nuclear reactor safely in case of accident. Heat is normally removed from nuclear power plant’s reactor through condensation of steam after the steam has passed through the turbine. In BWR (boiling water reactor) the steam that has been condensed (now water) is usually fed back into the nuclear reactor (INSAG). However in PWR (pressurized water reactor), the steam is fed back to the nuclear power plant reactor through a heat exchanger (Amano and Sundén). This process of condensing steam helps in maintaining the temperature of nuclear reactor core constant. In case of an accident, rapid cooling of the steam as well as that of the reactor is usually required, and condensers cannot cool the steam rapidly; therefore not used. Alternative cooling methods are usually required to rapidly enhance the cooling of the steam as well that of the nuclear reactor. Therefore emergency core cooling systems are employed. The emergency core cooling systems are designed to enable nuclear power plant respond to as many types of accidents and emergency conditions as possible (Nuclear Energy Agency). In order to increase safety of nuclear power plants in case of an accident or emergency, the emergency core cooling systems introduce redundancy in the plant such that reactor can be shut down with system failures. ADS (also known as depressurization system) Another important safety system which the nuclear power plants are equipped with is ADS (or depressurization system). The nuclear power plant’s depressurization system is equipped with several valves. In case of pressure build up beyond the recommended values, the valves open to release steam into large water pools that are usually located underground (these pools are usually known as torus or wetwell) (Amano and Sundén). The steam can also be directly released into the nuclear power plant’s primary containment structure. The release of steam through actuation of the valves reduces pressures in the nuclear reactors, thereby allowing the functionality of the reactor’s low pressure coolant injection systems (LPCIS) (INSAG). The low pressure coolant injection systems (LPCIS) normally have large capacities as compared to high pressure coolant injection systems. Most of the ADS (or depressurization systems) are usually automatic, however, some manual, and activation are usually carried out when it is necessary. What are low pressure coolant injection systems and high pressure coolant injection systems? This might the question that is lingering in the mind of the reader. The next paragraph briefly describes these safety control systems. Low pressure and High pressure cooling systems The low pressure coolant systems have pumps which serve the purpose of injecting coolant into the nuclear power plant’s reactor if the reactor is depressurized. High pressure coolant systems also have pumps; however, these pumps have enough pressure of injecting coolant into the nuclear power plant’s reactor if the reactor is pressurized (Amano and Sundén). These coolant injecting systems have been designed to monitor as well as examine coolant level in the reactor, and take the action of injecting more coolant if the level of the coolant in the reactor drops beyond certain level (level specified as minimum) (INSAG). The high pressure coolant injection systems are normally considered as first safety systems since they can be used while pressures in the nuclear reactors are still high. Accidents associated with nuclear power plant failure or due natural factors or due to any other factor may result in the release of radioactive materials into the environment. Therefore, safety procedures as well as nuclear power plants should be maintained, and should always be ready. The safety systems discussed above are just a few; there exist other safety measures well as systems that are not covered in this paper. Otherwise, owing to the risks associated with nuclear power plants, safety systems should always be operational and in good condition. References Amano, Ryoichi S. and Bengt Sundén. Thermal Engineering in Power Systems. New York: WIT Press. , 2008. INSAG. Basic Safety Principles for Nuclear Power Plants. Vienna: International Nuclear Safety Advisory Group, 2009. Nuclear Energy Agency. Nuclear Development Nuclear Power Plant Life Management and Longer-term operation. Paris: OECD, Nuclear Energy Agency, 2006. Read More