nuc power plant handbook

8/12/2019 Nuc Power Plant Handbook

1/38

REPORTERS:RYAN V. FERRER

KURT IAN ROLDAN ABEL HIPOL

MICHAEL CABADINGCIPRIANO PETATE


2/38

WHAT IS A NUCLEAR POWER

PLANT A nuclear power plant (NPP ) is a thermal powerstation in which the heat source is one or more nuclearreactors. As in a conventional thermal power stationthe heat is used to generate steam which drives a steamturbine connected to a generator whichproduces electricity.

Nuclear power plants are usually considered to be baseload stations, which are best suited to constant poweroutput.


3/38

WHAT ARE THE USES OF A

NUCLEAR POWER PLANT As of 2005, nuclear power provided 6.3% of the world's energy and 15%of the world's electricity, with the U.S., France, and Japan togetheraccounting for 56.5% of nuclear generated electricity. In 2007, the IAEAreported there were 439 nuclear power reactors in operation in the

world, operating in 31 countries. As of December 2009, the world had436 reactors. Since commercial nuclear energy began in the mid 1950s,2008 was the first year that no new nuclear power plant was connectedto the grid, although two were connected in 2009.

Annual generation of nuclear power has been on a slight downwardtrend since 2007, decreasing 1.8% in 2009 to 2558 TWh with nuclearpower meeting 13 14% of the world's electricity demand. One factor inthe nuclear power percentage decrease since 2007 has been theprolonged shutdown of large reactors at the Kashiwazaki-KariwaNuclear Power Plant in Japan following the Niigata-Chuetsu-Okiearthquake..


4/38

WHAT ARE THE USES OF A

NUCLEAR POWER PLANTThe United States produces the most nuclear energy, with nuclear power providing 19% of the electricity it consumes, while France produces the highest percentage of itselectrical energy from nuclear reactors 80% as of 2006. In the European Union as a whole, nuclear energy provides 30% of the electricity. Nuclear energy policy differsamong European Union countries, and some, such as Austria, Estonia, Ireland and Italy,have no active nuclear power stations. In comparison, France has a large number of theseplants, with 16 multi-unit stations in current use.In the US, while the coal and gas electricity industry is projected to be worth $85 billionby 2013, nuclear power generators are forecast to be worth $18 billion.Many military and some civilian (such as some icebreaker) ships use nuclear marinepropulsion, a form of nuclear propulsion. A few space vehicles have been launched usingfull-fledged nuclear reactors: the Soviet RORSAT series and the American SNAP-10A.International research is continuing into safety improvements such as passively safe

plants, the use of nuclear fusion, and additional uses of process heat such as hydrogenproduction (in support of a hydrogen economy), for desalinating sea water, and for use indistrict heating systems


5/38

HISTORY OF NUCLEAR POWER

PLANTOriginThe pursuit of nuclear energy for electricity generation began soon after thediscovery in the early 20th century that radioactive elements, such as radium,released immense amounts of energy, according to the principle of mass energy equivalence. However, means of harnessing such energy wasimpractical, because intensely radioactive elements were, by their very nature,short-lived (high energy release is correlated with short half-lives). However,the dream of harnessing "atomic energy" was quite strong, even it wasdismissed by such fathers of nuclear physics like Ernest Rutherford as"moonshine." This situation, however, changed in the late 1930s, with thediscovery of nuclear fission.In 1932, James Chadwick discovered the neutron, which was immediatelyrecognized as a potential tool for nuclear experimentation because of its lack ofan electric charge. Experimentation with bombardment of materials withneutrons led Frdric and Irne Joliot-Curie to discover induced radioactivityin 1934, which allowed the creation of radium-like elements at much less theprice of natural radium. Further work by Enrico Fermi in the 1930s focused onusing slow neutrons to increase the effectiveness of induced radioactivity.


6/38


PLANTExperiments bombarding uranium with neutrons led Fermi to believe he had created anew, transuranic element, which he dubbed hesperium.But in 1938, German chemists Otto Hahn and Fritz Strassmann, along with Austrianphysicist Lise Meitner and Meitner's nephew, Otto Robert Frisch, conducted experiments with the products of neutron-bombarded uranium, as a means of further investigatingFermi's claims. They determined that the relatively tiny neutron split the nucleus of themassive uranium atoms into two roughly equal pieces, contradicting Fermi. This was anextremely surprising result: all other forms of nuclear decay involved only small changesto the mass of the nucleus, whereas this process dubbed "fission" as a reference tobiology involved a complete rupture of the nucleus. Numerous scientists, including LeSzilrd, who was one of the first, recognized that if fission reactions released additionalneutrons, a self-sustaining nuclear chain reaction could result. Once this wasexperimentally confirmed and announced by Frdric Joliot-Curie in 1939, scientists inmany countries (including the United States, the United Kingdom, France, Germany, andthe Soviet Union) petitioned their governments for support of nuclear fission research, just on the cusp of World War II.In the United States, where Fermi and Szilrd had both emigrated, this led to thecreation of the first man-made reactor, known as Chicago Pile-1, which achievedcriticality on December 2, 1942. This work became part of the Manhattan Project, whichmade enriched uranium and built large reactors to breed plutonium for use in the firstnuclear weapons, which were used on the cities of Hiroshima and Nagasaki.


7/38


PLANT After World War II, the prospects of using "atomic energy" for good, rather than simplyfor war, were greatly advocated as a reason not to keep all nuclear research controlled bymilitary organizations. However, most scientists agreed that civilian nuclear power wouldtake at least a decade to master, and the fact that nuclear reactors also produced weapons-usable plutonium created a situation in which most national governments(such as those in the United States, the United Kingdom, Canada, and the USSR)attempted to keep reactor research under strict government control and classification. Inthe United States, reactor research was conducted by the U.S. Atomic EnergyCommission, primarily at Oak Ridge, Tennessee, Hanford Site, and Argonne NationalLaboratory.Work in the United States, United Kingdom, Canada, and USSR proceededover the course of the late 1940s and early 1950s. Electricity was generated for the firsttime by a nuclear reactor on December 20, 1951, at the EBR-I experimental station near Arco, Idaho, which initially produced about 100 kW. Work was also strongly researchedin the US on nuclear marine propulsion, with a test reactor being developed by 1953(eventually, the USS Nautilus, the first nuclear-powered submarine, would launch in1955). In 1953, US President Dwight Eisenhower gave his "Atoms for Peace" speech at theUnited Nations, emphasizing the need to develop "peaceful" uses of nuclear powerquickly. This was followed by the 1954 Amendments to the Atomic Energy Act whichallowed rapid declassification of U.S. reactor technology and encouraged development bythe private sector.


8/38


PLANTDevelopment Installed nuclear capacity initially rose relatively quickly, rising fromless than 1 gigawatt (GW) in 1960 to 100 GW in the late 1970s, and 300GW in the late 1980s. Since the late 1980s worldwide capacity has risen

much more slowly, reaching 366 GW in 2005. Between around 1970and 1990, more than 50 GW of capacity was under construction(peaking at over 150 GW in the late 70s and early 80s) in 2005,around 25 GW of new capacity was planned. More than two-thirds ofall nuclear plants ordered after January 1970 were eventually cancelled.

A total of 63 nuclear units were canceled in the USA between 1975 and1980. During the 1970s and 1980s rising economic costs (related toextended construction times largely due to regulatory changes andpressure-group litigation) and falling fossil fuel prices made nuclearpower plants then under construction less attractive. In the 1980s (U.S.)and 1990s (Europe), flat load growth and electricity liberalization alsomade the addition of large new baseload capacity unattractive.


9/38

The 1973 oil crisis had a significant effect on countries, such as France and Japan, which had relied more heavily on oilfor electric generation (39% [verification needed ] and 73% respectively) to invest in nuclear power. Today, nuclear powersupplies about 80% and 30% of the electricity in those countries, respectively.Some local opposition to nuclear power emerged in the early 1960s, and in the late 1960s some members of thescientific community began to express their concerns. These concerns related to nuclear accidents, nuclearproliferation, high cost of nuclear power plants, nuclear terrorism and radioactive waste disposal. In the early 1970s,there were large protests about a proposed nuclear power plant in Wyhl Germany. The project was cancelled in 1975and anti-nuclear success at Wyhl inspired opposition to nuclear power in other parts of Europe and North America. [ Bythe mid-1970s anti-nuclear activism had moved beyond local protests and politics to gain a wider appeal and influence,and nuclear power became an issue of major public protest. Although it lacked a single co-ordinating organization,and did not have uniform goals, the movement's efforts gained a great deal of attention. In some countries, the nuclearpower conflict "reached an intensity unprecedented in the history of technology controversies". In France, between1975 and 1977, some 175,000 people protested against nuclear power in ten demonstrations. In West Germany, betweenFebruary 1975 and April 1979, some 280,000 people were involved in seven demonstrations at nuclear sites. Several siteoccupations were also attempted. In the aftermath of the Three Mile Island accident in 1979, some 120,000 peopleattended a demonstration against nuclear power in Bonn. In May 1979, an estimated 70,000 people, including thengovernor of California Jerry Brown, attended a march and rally against nuclear power in Washington, D.C. Anti-nuclearpower groups emerged in every country that has had a nuclear power programme. Some of these anti-nuclear powerorganisations are reported to have developed considerable expertise on nuclear power and energy issues.Health and safety concerns, the 1979 accident at Three Mile Island, and the 1986 Chernobyl disaster played a part instopping new plant construction in many countries, although the public policy organization Brookings Institutionsuggests that new nuclear units have not been ordered in the U.S. because of soft demand for electricity, and costoverruns on nuclear plants due to regulatory issues and construction delays.Unlike the Three Mile Island accident, the much more serious Chernobyl accident did not increase regulationsaffecting Western reactors since the Chernobyl reactors were of the problematic RBMK design only used in the SovietUnion, for example lacking "robust" containment buildings. Many of these reactors are still in use today. However,changes were made in both the reactors themselves (use of low enriched uranium) and in the control system(prevention of disabling safety systems) to reduce the possibility of a duplicate accident.

An international organization to promote safety awareness and professional development on operators in nuclearfacilities was created: WANO; World Association of Nuclear Operators.Opposition in Ireland and Poland prevented nuclear programs there, while Austria (1978), Sweden (1980) and Italy(1987) (influenced by Chernobyl) voted in referendums to oppose or phase out nuclear power. In July 2009, the ItalianParliament passed a law that canceled the results of an earlier referendum and allowed the immediate start of theItalian nuclear program. One Italian minister even called the nuclear phase-out a "terrible mistake".


10/38

SYSTEM OF NUCLEAR POWER

PLANTThe conversion to electrical energy takes place indirectly, asin conventional thermal power plants: The heat isproduced by fission in a nuclear reactor (inlight waterreactor). Directly or indirectly water vapor-steam isproduced. The pressurized steam is then usually fed to amulti-stage steam turbine. Steam turbines in Westernnuclear power plants are among the largest steam turbinesever. After the steam turbine has expanded and partiallycondensed the steam, the remaining vapor is condensed in

a condenser. The condenser is a heat exchanger which isconnected to secondary side such as a river or a coolingtower. The water then pumped back into the nuclearreactor and the cycle begins again. The water-steam cyclecorresponds to the Rankine cycle


11/38


PLANT1. NUCLEAR REACTOR A nuclear reactor is a device to initiate and control a sustained nuclear

chain reaction. The most common use of nuclear reactors is for the generationof electric energy and for the propulsion of ships.

The nuclear reactor is the heart of the plant. In its central part, thereactor core's heat is generated by controlled nuclear fission. With this heat, acoolant is heated as it is pumped through the reactor and thereby removes theenergy from the reactor. Heat from nuclear fission is used to raise steam, whichruns through turbines, which in turn powers either ship's propellers orelectrical generators.

Since nuclear fission creates radioactivity, the reactor core is surroundedby a protective shield. This containment absorbs radiation and preventsradioactive material from being released into the environment. In addition,many reactors are equipped with a dome of concrete to protect the reactoragainst external impacts.

In nuclear power plants, different types of reactors, nuclear fuels, andcooling circuits and moderators are sometimes used


12/38


PLANTHOW NUCLEAR REACTOR WORKS?
http://en.wikipedia.org/wiki/File:Nuclear_fission.svg


13/38

When a large fissile atomic nucleus such as uranium-235 or plutonium-239 absorbs a neutron, it may undergo nuclear fission. The heavynucleus splits into two or more lighter nuclei, releasing kineticenergy, gamma radiation and free neutrons; collectively knownas fission products. A portion of these neutrons may later be absorbedby other fissile atoms and trigger further fission events, which releasemore neutrons, and so on. This is known as anuclear chain reaction.This nuclear chain reaction can be controlled by using neutronpoisons and neutron moderators to change the portion of neutronsthat will go on to cause more fissions. Nuclear reactors generally haveautomatic and manual systems to shut the fission reaction down ifunsafe conditions are detected.Commonly used moderators include regular (light) water (75% of the

world's reactors), solid graphite (20% of reactors) and heavy water (5%of reactors).Beryllium has also been used in some experimental types,and hydrocarbons have been suggested as another possibility.


14/38


15/38

Reactivity control The power output of the reactor is adjusted by

controlling how many neutrons are able to create morefissions.Control rods that are made of a neutron poison areused to absorb neutrons. Absorbing more neutrons in

a control rod means that there are fewer neutronsavailable to cause fission, so pushing the control roddeeper into the reactor will reduce its power output,and extracting the control rod will increase it.


16/38

Components of nuclear reactor1. FUELUranium is the basic fuel. Usually pellets of uranium oxide(UO 2) are arranged in tubes to form fuel rods. The rods are

arranged into fuel assemblies in the reactor core.*In a new reactor with new fuel a neutron source is neededto get the reaction going. Usually this is beryllium mixed with polonium, radium or other alpha-emitter. Alphaparticles from the decay cause a release of neutrons fromthe beryllium as it turns to carbon-12. Restarting a reactor with some used fuel may not require this, as there may beenough neutrons to achieve criticality when control rodsare removed.


17/38

Components of nuclear reactor2. MODERATOR

This is material in the core which slows down the

neutrons released from fission so that they cause morefission. It is usually water, but may be heavy water orgraphite.


18/38

Components of nuclear reactor3. Control rods

These are made with neutron-absorbing material such

as cadmium, hafnium or boron, and are inserted or withdrawn from the core to control the rate ofreaction, or to halt it.* In some PWR reactors, specialcontrol rods are used to enable the core to sustain alow level of power efficiently. (Secondary shutdownsystems involve adding other neutron absorbers,usually as a fluid, to the system.)


19/38


20/38

Components of nuclear reactor5. Pressure vessel or pressure tubes

Usually a robust steel vessel containing the reactorcore and moderator/coolant, but it may be a series oftubes holding the fuel and conveying the coolantthrough the moderator.


21/38

Components of nuclear reactor6. Steam generator

Part of the cooling system where the primary coolantbringing heat from the reactor is used to make steamfor the turbine. Reactors may have up to four "loops",each with a steam generator.


22/38

Components of nuclear reactor7. ContainmentThe structure around the reactor core which isdesigned to protect it from outside intrusion and toprotect those outside from the effects of radiation incase of any malfunction inside. It is typically a metre-thick concrete and steel structure.


23/38

2.) STEAM TURBINEThe objective of the steam turbine is to convert the heatcontained in steam into mechanical energy. The engine house

with the steam turbine is usually structurally separated from themain reactor building. It is aligned to prevent debris from thedestruction of a turbine in operation from flying towards thereactor.In the case of a pressurized water reactor, the steam turbinehermetically separated from the nuclear system. To detect a leakin the steam generator and thus the passage of radioactive waterat an early stage is the outlet steam of the steam generatormounted an activity meter. In contrast, boiling water reactorsand the steam turbine with radioactive water applied andtherefore part of the control area of the nuclear power plant.


24/38

STEAM TURBINE SPEED REGULATION When warming up a steam turbine for use, the main steam stop valves have a bypass lineto allow superheated steam to slowly bypass the valve and proceed to heat up the lines inthe system along with the steam turbine. Also, a turning gear is engaged when there is nosteam to the turbine to slowly rotate the turbine to ensure even heating to preventuneven expansion. After first rotating the turbine by the turning gear, allowing time forthe rotor to assume a straight plane (no bowing), then the turning gear is disengaged andsteam is admitted to the turbine, first to the astern blades then to the ahead blades slowlyrotating the turbine at 10 15 RPM (0.170.25 Hz) to slowly warm the turbine. Any imbalance of the rotor can lead to vibration, which in extreme cases can lead to ablade breaking away from the rotor at high velocity and being ejected directly throughthe casing. To minimize risk it is essential that the turbine be very well balanced andturned with dry steam - that is, superheated steam with a minimal liquid water content.If water gets into the steam and is blasted onto the blades (moisture carry over), rapidimpingement and erosion of the blades can occur leading to imbalance and catastrophicfailure. Also, water entering the blades will result in the destruction of the thrust bearingfor the turbine shaft. To prevent this, along with controls and baffles in the boilers toensure high quality steam, condensate drains are installed in the steam piping leading tothe turbine. Modern designs are sufficiently refined that problems with turbines are rareand maintenance requirements are relatively small.


25/38

STEAM TURBINE OPERTION MAINTENANCE When warming up a steam turbine for use, the main steam stop valves have a bypass line toallow superheated steam to slowly bypass the valve and proceed to heat up the lines in thesystem along with the steam turbine. Also, a turning gear is engaged when there is no steam tothe turbine to slowly rotate the turbine to ensure even heating to prevent uneven expansion.

After first rotating the turbine by the turning gear, allowing time for the rotor to assume a

straight plane (no bowing), then the turning gear is disengaged and steam is admitted to theturbine, first to the astern blades then to the ahead blades slowly rotating the turbine at 10 15 RPM (0.170.25 Hz) to slowly warm the turbine.

Any imbalance of the rotor can lead to vibration, which in extreme cases can lead to a bladebreaking away from the rotor at high velocity and being ejected directly through the casing. Tominimize risk it is essential that the turbine be very well balanced and turned with dry steam -that is, superheated steam with a minimal liquid water content. If water gets into the steamand is blasted onto the blades (moisture carry over), rapid impingement and erosion of theblades can occur leading to imbalance and catastrophic failure. Also, water entering the blades

will result in the destruction of the thrust bearing for the turbine shaft. To prevent this, along with controls and baffles in the boilers to ensure high quality steam, condensate drains areinstalled in the steam piping leading to the turbine. Modern designs are sufficiently refinedthat problems with turbines are rare and maintenance requirements are relatively small.


26/38

3. ELECTRIC GENERATOR When a turbine is attached to the electrical generator,the kinetic energy of steam pushes against the fan-type blades of the turbine, causing the turbine, andtherefore, the attached rotor of the electricalgenerator, to spin and produce electricity.


27/38


28/38

5. COOLING TOWERcooling towers are heat removal devices used totransfer process waste heat to the atmosphere.


29/38


30/38

5. SAFETY VALVES In the event of an emergency, two independent safety valves can be used to prevent pipes from bursting orthe reactor from exploding. The valves are designed sothat they can derive all of the supplied flow rates withlittle increase in pressure. In the case of the BWR, thesteam is directed into the condensate chamber andcondenses there. The chambers on a heat exchangerare connected to the intermediate cooling circuit.


31/38

6. FEED WATER PUMP The water level in the steam generator and nuclearreactor is controlled using the feedwater system. Thefeedwater pump has the task of taking the water fromthe feedwater tank up to the vapor pressure in thereactor and steam generator at rates of 2200 kg/s. Thepower required is about 20 MW per pump.


32/38

7. EMERGENCY POWER SUPPLY The emergency power supplies of a nuclear power plant arebuilt up by several layers of redundancy, such as diesel

generators, gas turbine generators and battery buffers. Thebattery backup provides uninterrupted coupling of thediesel/gas turbine units to the power supply network. Ifnecessary, the emergency power supply allows the safe shutdown of the nuclear reactor. Less important auxiliary

systems such as, for example, heat tracing of pipelines arenot supplied by these back ups. The majority of therequired power is used to supply the feed pumps in ordercool reactor and remove the decay heat after shut down.


33/38

MAINTENANCE OF NUCLEAR

PLANTExtensive preventive maintenance and testing (surveillance)programs exist to ensure that nuclear safety significantequipment will function when it is supposed to. Dieselgenerators, pumps, motor operated valves and air operated

control valves are typically operated every one to three months. When you drive a car, you depend a lot on the sounds, the feel ofthe steering wheel and the gauges to determine if the car isrunning correctly. Similarly with operating equipment at a powerplant - if sounds or vibration of the equipment or the gauges andtest equipment indicate a problem or degradation, actions are

taken to correct the deficiency. If the equipment fails to start orrun, more immediate actions are taken. In some cases,regulations called technical specifications may require the plantto be shutdown if the equipment is not corrected within acertain period of time. The length of time depends on the safetysignificance of the equipment.


34/38


35/38


36/38

ADVANTAGES OF NUCLEAR POWER

PLANT1. The amount of electricity produced in a nuclear power station is equivalent to that produced by afossil fuelled power station.

2. Nuclear power stations do not burn fossil fuels to produce electricity and consequently they donot produce damaging, polluting gases.

3. Many supporters of nuclear power production say that this type of power is environmentallyfriendly and clean. In a world that faces global warming they suggest that increasing the use ofnuclear power is the only way of protecting the environment and preventing catastrophic climatechange.

4. Many developed countries such as the USA and the UK no longer want to rely on oil and gasimported from the Middle East, a politically unstable part of the world.

5. Countries such as France produce approximately 90 percent of their electricity from nuclear power

and lead the world in nuclear power generating technology - proving that nuclear power is aneconomic alternative to fossil fuel power stations.

6. Nuclear reactors can be manufactured small enough to power ships and submarines. If this wasextended beyond military vessels, the number of oil burning vessels would be reduced andconsequently pollution.


37/38

DISADVANTAGES OF NUCLEAR

POWER PLANT1. Nuclear power is a controversial method of producing electricity. Many people and environmental organisations are very concerned about the radioactive fuel it needs.

2. There have been serious accidents with a small number of nuclear power stations. The accident at Chernobyl(Ukraine) in 1986, led to 30 people being killed and over 100,000 people being evacuated. In the preceding yearsanother 200,00 people were resettled away from the radioactive area. Radiation was even detected over a thousandmiles away in the UK as a result of the Chernobyl accident. It has been suggested that over time 2500 people died as aresult of the accident.

3. There are serious questions to be answered regarding the storage of radioactive waste produced through the use ofnuclear power. Some of the waste remains radioactive (dangerous) for thousands of years and is currently stored inplaces such as deep caves and mines.

4. Storing and monitoring the radioactive waste material for thousands of years has a high cost.

5. Nuclear powered ships and submarines pose a danger to marine life and the environment. Old vessels can leakradiation if they are not maintained properly or if they are dismantled carelessly at the end of their working lives.

6. Many people living near to nuclear power stations or waste storage depots are concerned about nuclear accidentsand radioactive leaks. Some fear that living in these areas can damage their health, especially the health of youngchildren.

7. Many Governments fear that unstable countries that develop nuclear power may also develop nuclear weapons andeven use them.


38/38

nuc power plant handbook

Documents