Nuclear power plant
- 1. Prof R.S.KOLHE ME ( Heat Power) S.R.E.S.COLLEGE OF ENGINEERING KOPARGAON Introduction To Nuclear Power Plant
- 2. Introduction The science of atomic radiation, atomic change and nuclear fission was developed from 1895 to 1945, much of it in the last six of those years Over 1939-45, most development was focused on the atomic bomb From 1945 attention was given to harnessing this energy in a controlled fashion for naval propulsion and for making electricity Since 1956 the prime focus has been on the technological evolution of reliable nuclear power plants.
- 3. Economic Advantages The energy in one pound of highly enriched Uranium is comparable to that of one million gallons of gasoline. One million times as much energy in one pound of Uranium as in one pound of coal. Nuclear energy annually prevents 5.1 million tons of sulfur 2.4 million tons of nitrogen oxide 164 metric tons of carbon First commercial power plant, England 1956 17% of world’s electricity is from nuclear power
- 4. Nuclear Reactions • Nuclear reactions deal with interactions between the nuclei of atoms including of nuclear fission and nuclear fusion • Both fission and fusion processes deal with matter and energy • Fission is the process of splitting of a nucleus into two "daughter" nuclei leading to energy being released • Fusion is the process of two "parent" nuclei fuse into one daughter nucleus leading to energy being released
- 5. Fission Reaction • A classic example of a fission reaction is that of U-235: • U-235 + 1 Neutron 2 Neutrons + Kr-92 + Ba-142 + E • In this example, a stray neutron strikes an atom of U235. It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission.
- 6. Fusion Reactions •A classic example of a fusion reaction is that of deuterium (heavy hydrogen) and tritium which is converted to Helium and release energy. p + p He + n + .42 MeV
- 7. Parts of A Nuclear Reactor A nuclear reactor is an apparatus in which heat is produced due to nuclear fission chain reaction 1. Nuclear Fuel 2. Moderator 3. Control Rods 4. Reflector 5. Reactors Vessel 6. Biological Shielding 7. Coolant.
- 9. Nuclear Fuel Fuel of a nuclear reactor should be fissionable material which can be defined as an element or isotope whose nuclei can be caused to undergo nuclear fission by nuclear bombardment and to produce a fission chain reaction. It can be one or all of the following U233, U235 and Pu239. Natural uranium found in earth crust contains three isotopes namely U234, U235 and U238 and their average percentage is as follows : U238 — 99.3% U235 — 0.7% U234 — Trace
- 10. Moderator In the chain reaction the neutrons produced are fast moving neutrons These fast moving neutrons are far less effective in causing the fission of U235 and try to escape from the reactor. To improve the utilization of these neutrons their speed is reduced. It is done by colliding them with the nuclei of other material which is lighter, does not capture the neutrons but scatters them. Each such collision causes loss of energy, and the speed of the fast moving neutrons is reduced. Such material is called Moderator. The slow neutrons (Thermal Neutrons) so produced are easily captured by the nuclear fuel and the chain reaction proceeds smoothly. Graphite, heavy water and beryllium are generally used as moderator.
- 11. A moderator should process the following properties : It should have high thermal conductivity. It should be available in large quantities in pure form. It should have high melting point in case of solid moderators and low melting point in case of liquid moderators. Solid moderators should also possess good strength and machinability It should provide good resistance to corrosion. It should be stable under heat and radiation. It should be able to slow down neutrons.
- 12. Control Rods. The energy produced in the reactor due to fission of nuclear fuel during chain reaction is so much that if it is not controlled properly the entire core and surrounding structure may melt and radioactive fission products may come out of the reactor thus making it uninhabitable. This implies that we should have some means to control the power of reactor. This is done by means of control rods. Control rods in the cylindrical or sheet form are made of boron or cadmium. These rods can be moved in and out of the holes in the reactor core assembly. Their insertion absorbs more neutrons and damps down the reaction and their withdrawal absorbs less neutrons. Thus power of reaction is controlled by shifting control rods which may be done manually or automatically.
- 13. Reflector The neutrons produced during the fission process will be partly absorbed by the fuel rods, moderator, coolant or structural material etc. Neutrons left unabsorbed will try to leave the reactor core never to return to it and will be lost. Such losses should be minimized. It is done by surrounding the reactor core by a material called reflector which will send the neutrons back into the core. The returned neutrons can then cause more fission and improve the neutrons economy of' the reactor. Generally the reflector is made up of graphite and beryllium.
- 14. Reactor Vessel It is a. strong walled container housing the cure of the power reactor. It contains moderator, reflector, thermal shielding and control rods.
- 15. Biological Shielding Shielding the radioactive zones in the reactor roan possible radiation hazard is essential to protect, the operating men from the harmful effects. During fission of nuclear fuel, alpha particles, beta particles, deadly gamma rays and neutrons are produced. Out oil these nc-1utroxrs and gamma rays are of main significance. A protection must be provided against them. Thick layers of lead or concrete are provided round the reactor for stopping the gamma rays. Thick layers of metals or plastics are sufficient to stop the alpha and beta particles.
- 16. Coolant Coolant flows through and around the reactor core. It is used to transfer the large amount of heat produced in the reactor due to fission of the nuclear fuel during chain reaction. The coolant either transfers its heat to another medium or if the coolant used is water it takes up the heat and gets converted into steam in the reactor which is directly sent to the turbine.
- 17. Coolant Coolant used should be stable under thermal condition. It should have a low melting point and high boiling point. It should not corrode the material with which it comes in contact. The coolant should have high heat transfer coefficient. The radioactivity induced in coolant by the neutrons bombardment should be nil. The various fluids used as coolant are water (light water or heavy water), gas (Air, CO2, Hydrogen, Helium) and liquid metals such as sodium or mixture of sodium and potassium and inorganic and organic fluids.
- 18. Classification of reactor Based on neutron energy A. Fast Reactor B. Slow or thermal reactor C. Intermediate reactor Based on fuel used A. Natural uranium fuel reactor B. Enriched uranium fuel reactor Based on coolant used A. Water cooled reactor B. Heavy Water cooled reactor C. Liquid metal cooled reactor D. Gas cooled reactor Based on moderator used A. Water and heavy water reactor B. Graphite reactor C. Beryllium reactor
- 22. Liquid metal fast breeder reactor
- 23. Nuclear Power Station In India (i) Tarapur Nuclear Power Station. It has two boiling water reactors each of 200 mW capacity and uses enriched uranium as its fuel. It supplies power to Gujarat and Maharashtra. (ii) Rana Pratap Sagar (Rajasthan) Nuclear Station. It has been built at 42 miles south west of Kota in Rajasthan with Canadian collaboration. It has two reactors each of 200 mW capacity and uses natural uranium in the form of oxide as fuel and heavy water as moderator.
- 24. Nuclear Power Station In India iii) Kalpakkam Nuclear Power Station. It is the third nuclear power station in India and is being built at about 40 miles from Madras City. It will be wholly designed and constructed by Indian scientists and engineers. It has two fast reactors each of 235 mW capacity and will use natural uranium as its fuel. The first unit of 235 mW capacity has started generating power from 1983 and the second 235 MW unit is commissioned in 1985. The pressurized heavy water reactors will use natural uranium available in plenty in India. The two turbines and steam generators at the Kalpakkam atomic power project are the largest capacity generating sets installed in our country. In this power station about 88% local machinery and equipment have been used.
- 25. Nuclear Power Station In India (iv) Narora Nuclear Power Station. It is India’s fourth nuclear power station and is being built at Narora in Uttar Pradesh. This plant will initially have two units of 235 mW each and provision has been made to expand its capacity of 500 mW. This plant will have two reactors of the CANDUPHW (Canadian Deutrium-Uranium-Pressurised Heavy Water) system and will use natural uranium as its fuel. This plant will be wholly designed and constructed by the Indian scientists and engineers. This plant supplies power to Delhi, Haryana, Panjab, J and K.
- 26. Nuclear Power Station In India v) Kakarpar Nuclear Power Plant. This fifth nuclear power plant of India is to be located at Kakarpar near Surat in Gujarat. This power station will have four reactors each of 235 mW capacity. The reactors proposed to be constructed at Kakarpar would be of the Candu type natural uranium fuelled and heavy water moderated reactors-incorporating the standardised basic design features of the Narora reactors suitably adapted to local conditions
- 27. NUCLEAR POWER STATION IN INDIA (vi) Kaiga Atomic Power Plant. The sixth atomic power plant will be located at Kaiga in Karnataka. Kaiga is located away from human habitation and is a well suited site for an atomic power plant. It will have two units of 235 mW each.
- 28. Nuclear waste disposal Waste disposal of nuclear power station is of prime importance since nuclear waste is likely to have radioactivity . Therefore these wastes are disposed off in such a manner that it does not cause harm to human or plant life. In case of greenhouse waste , it is passed through filters and discharged at high level through stacks. Moderate liquid waste can be discharged after filtration , preliminary treatment ( its PH value is adjusted) and by diluting and mixing with cooling water discharged in to deep pits or dry well. Highly radioactive liquid waste are kept in concrete tank and buried into ground till their decay of radioactivity. Solid waste arising from discarded control rods fuel can etc are stored in shielded concrete vaults.
- 29. Advantages of A Nuclear Power Plant Space requirement of a nuclear power plant is less as compared to other conventional power plants are of equal size. A nuclear power plant consumes very small quantity of fuel. Thus fuel transportation cost is less and large fuel storage facilities are not needed Further the nuclear power plants will conserve the fossil fuels (coal, oil, gas etc.) for other energy need. There is increased reliability of operation. Nuclear power plants are not effected by adverse weather conditions. Nuclear power plants are well suited to meet large power demands. They give better performance at higher load factors (80 to 90%). Materials expenditure on metal structures, piping, storage mechanisms are much lower for a nuclear power plant than a coal burning power plant.
- 30. Disadvantages Initial cost of nuclear power plant is higher as compared to hydro or steam power plant. Nuclear power plants are not well suited for varying load conditions. Radioactive wastes if not disposed carefully may have bad effect on the health of workers and other population. In a nuclear power plant the major problem faced is the disposal of highly radioactive waste in form of liquid, solid and gas without any injury to the atmosphere. The preservation of waste for a long time creates lot of difficulties and requires huge capital. Maintenance cost of the plant is high. It requires trained personnel to handle nuclear power plants.
- 31. References Power plant Engineering, P.K NAG