NUCLEAR ENERGYPrepared by Engr. JP Timola

Reference: Nuclear Energy by Dr. Lana Aref

How is Nuclear Energy Produced?

• Nuclear energy is produced when an atom's nucleus is split into smaller nuclei by the process called fission.

• fission of large atoms, such as Uranium 235 and Plutonium 239, produces a great deal of energy.

• fission of 1 gram of Uranium 235 produces the same amount of energy as the combustion, or burning, of 3 tons of coal

• energy produced by the fission of uranium or plutonium can be harnessed to produce electricity, to propel space craft, and to power weapons like the Atomic Bomb.

Advantages Over Coal

• nuclear power plant uses the energy, or heat, produced by the fission of Uranium, rather than the burning of coal, to heat water into the steam required to turn the turbines that power electric generators.

• Uranium fission does not produce soot and potentially harmful gases such as Carbon Dioxide.

Disadvantages

• Uranium is mined and then processed before it can be used as an energy source.

• the different mining and processing steps, as well as the actual energy production, produce a great deal of waste.

• wastes are radioactive, and thus more difficult to handle.

What is radioactivity?

• A radioactive element is an element that is unstable

• Continually decays by releasing radiation

• Radiation is made up of high-energy particles or rays that can penetrate and damage the matter with which it comes into contact.

What is radioactivity?

• All elements that have an atomic number higher than 83are radioactive.

• Uranium has an atomic number of 92.

• Other radioactive elements, is located everywhere in nature and can be found in rock formations all over the world.

What is radioactivity?

• The length of time it takes for each element to decay depends on the type, as well as on the amount of the radioactive element present.

• The half-life of a radioactive material is the length of time it takes for half of that material to decay.

What is radioactivity?

• During the decay process, a radioactive element emits either an alpha or beta particle, which are sometimes accompanied by a gamma ray.

• In doing so, it changes from its original unstable form into other elements, called daughter elements, which can also be radioactive.

What is radioactivity?

• These radioactive daughter elements also undergo decay, until, ultimately, a stable element is formed.

• This chain of decay is called a radioactive decay series.

• There are three series: the uranium series, the thorium series, and the actinium series.

• Uranium series starts with Uranium 238, which changes into at least 14 different elements before it stabilizes as Lead 206.

What are the different types of radiation?

• There are three major types of radiation according to the forms of energy that are emitted by radioactive elements as they decay.

• Alpha

• Beta

• Gamma

Alpha Particles

• These particles are highly energized, but because they are so large, can not penetrate matter very deeply, and can be stopped by a single sheet of paper.

• However, if these particles do manage to come into contact with unprotected, internal cells, by ingestion for example, they can be extremely harmful.

Beta Particles

• These are not as highly energized as alpha particles but can penetrate skin.

• Also harmful when ingested, but since they are smaller they do not do as much internal damage.

Gamma Rays

• These electromagnetic waves, or photons, are similar to X-rays and can penetrate the body and organs easily.

• Gamma rays, though not as powerful as alpha particles, are dangerous because they are so invasive

Nuclear Radiation Health Trade Off

• Nuclear radiation can be used to kill cancer cells in humans.

• Can also be used to image the body, like in MRIs and X-rays, in order to diagnose disease and injury.

• Uncontrolled radiation exposure from sources such as radon in our basements, or from nuclear power plant accidents, or from poor nuclear waste disposal can do us a lot of harm.

Sievert (Sv).

• unit used in quantifying radiation

• ratio of the radiation energy (Joules) to the total mass exposed (kilograms)

Radiation from the environment

• Several radiation comes from natural background sources like the sun, rocks, and from concrete and brick

• Exposure varies with location.

• People living in the mountains are exposed to more solar radiation than those at low elevations.

• Also, when you fly in an airplane, your exposure increases by almost 50%.

• At high elevations, there is less atmosphere to protect you against the suns rays

The Nuclear Energy Debate

• The use of Nuclear Power has been controversial for a long time.

• Proponents of its use claim that it is a very 'clean' form of energy since very little fuel is needed to generate a lot of energy, and since no air pollution is produced, as in the burning of coal.

• However, because of accidents such as the one at Three Mile Island in the U.S., and the one at Chernobyl in the former Soviet Union, many people are opposed to Nuclear Power.

The Nuclear Energy Debate

• Also, environmentalists, as well as other citizen groups, are concerned about the disposal of the radioactive waste generated by the mining, processing and use of Nuclear fuel.

• Currently, there are no universally acceptable methods for the storage and disposal of these wastes.

• There is concern that buried wastes might leak into groundwater and eventually make it into surface waters or into drinking water supplies.

Nuclear Power Plant

Nuclear Fuel Steam Plant

• components are similar to those in a fossil-fueled plant,

• the steam boiler is replaced by a Nuclear Steam Supply System (NSSS).

• NSSS consists of a nuclear reactor and all of the components necessary to produce high pressure steam, which will be used to turn the turbine for the electrical generator.

Nuclear Fuel Steam Plant

• To operate properly, all steam plants, whether nuclear or fossil-fueled, need a circulating water system to remove excess heat from the steam system in order to condense the steam, and transfer that heat to the environment.

• The circulating water system pumps water from the environment (river, lake, ocean)through thousands of metal tubes in the plant’s condenser.

• Power plants located on the ocean will often discharge their circulating water directly back to the ocean under strict environmental protection regulations.

• Water is taken from the ocean, pumped through the thousands of small tubes in the condenser to remove the excess heat, and is then discharged back into the ocean.

• The expected temperature increase from circulating water inlet to outlet is about 5 to 10 degrees Fahrenheit.

• Most nuclear power plants not located on the ocean need cooling towers to remove the excess heat from the circulating water system.

• One type of cooling tower is the forced draft cooling tower. The circulating water is pumped into the tower, after passing through the condenser, and allowed to splash downward through the tower, transferring some of its heat to the air.

• Several large electrical fans, located at the top of the cooling tower, provide forced air circulation for more efficient cooling.

• The taller hourglass shaped, natural convection cooling towers do not require fans to transfer the excess heat from the circulating water system into the air.

• Rather, the natural tendency of hot air to rise removes the excess heat as the circulating water splashes down inside the cooling tower.

• These towers are typically several hundred feet tall.

Reactors

Boiling Water Reactor

Pressurized Water Reactor

Nuclear waste

• One of the main problems in the use of nuclear energy is the management of nuclear waste as it is very dangerous and difficult to eliminate.

Classification of Nuclear Wastes

• High-level nuclear wastes

• composed of elements of the fuel that has been made.

• Medium-activity nuclear wastes

• radionuclides produced in the nuclear fission process.

• Low-level nuclear waste

• basically the tools, clothes and miscellaneous material used for the maintenance of a nuclear power plant.

Nuclear Waste Treatment

• Medium Level

• With a treatment the radioactive elements contained in these by-products are separated and the

• resulting residues are deposited in steel drums solidifying them with tar, resins or cement.

Nuclear Waste Treatment

• Low Level

• pressed and mixed with concrete forming a solid block.

• also introduced into steel drums

Nuclear Waste Treatment

• High Level

• temporarily stored in a pool of water built of concrete and stainless steel walls inside the plant to create a radiation barrier and prevent leakage.

• One of the most accepted solutions among experts is Deep Geological Storage (AGP), usually in mines excavated in stable geological formations.

International Nuclear Event Scale

• Anomaly - Level 1

• Overexposure to an audience in excess of statutory annual limits.

• Minor problems in safety components with significant defense measures pending application in depth.

• Lost or stolen radioactive source, device or transport packaging of low activity.

• Incident - Level 2

• Exhibition of an audience above 10 mSv.• Exposure of a worker in excess of statutory annual limits.• Radiation levels exceeding 50 mSv / h in an area of operation.• Significant contamination inside a facility in an area not

expected by design.• Significant failures in safety provisions, but without real

consequences.• Finding of an orphaned sealed source of a device or packaging

for the transport of highly radioactive• Inadequate packaging of a highly radioactive sealed source.

• Major incident - Level 3

• Exposure ten times the annual limit for exposure of workers.• Effect non-lethal of radiation health (eg burns).• Rates above 1 Sv / h exposure in an operating area.• Severe contamination in an area not expected by design, with a low

probability of significant exposure the public.• Near accident at a nuclear power plant without provision of security

pending application.• Lost or stolen of highly radioactive sealed sources.• Wrong delivery of highly radioactive sealed source without adequate

procedures to manipulate

• Accident with local consequences - Level 4

• Minor release of radioactive material, with little likelihood of having to apply countermeasures under unless local food controls.

• At least one death from radiation.

• Fusion fuel or fuel damage, which causes liberation top 0.1% of the core inventory.

• Release of significant quantities of radioactive material within an installation with a high probability of significant public exposure.

• Accident with wider consequences - Level 5

• Limited release of radioactive material likely to require implementation of some planned countermeasures.

• Several deaths from radiation.

• Severe damage to the reactor core.

• Release of large quantities of radioactive material within an installation with a high probability of exposure to the public; possibly caused by a fire or severe criticality accident.

• Major accident - Level 6

• Significant release of radioactive material likely to require implementation of planned countermeasures.

• Serious accident - Level 7

• Major release of radioactive material with widespread effects on health and the environment, which requires the implementation and extension of planned countermeasures.

Nuclear accidents

• incidents that emit a certain level of radiation, which could harm public health.

• 1952 and 1958 - Chalk River, Canada

• December 12, 1952 --- first serious nuclear accident

• May 24, 1958 --- NRU reactor a rod of uranium fuel caught on fire and it split in two while trying to remove it from the reactor core.

• 1957 - Mayak, Russia

• one of the points of the planet with pollution by radioactive materials,

• nuclear leaks have been occurring for 30 years

• 1957 - Windscale Pile, United Kingdom

• In October 1957 --- worst nuclear accident in history of the United Kingdom

• Classified at Level 5 of the INES scale.

• The fire at the nuclear reactor led to the release of radioactive material into the surrounding area.

1979 - Three Mile Island, USA

• March 1979 --- Misinterpretation of data caused serious errors in certain decisions of plant personnel.

• Although the core of the nuclear reactor was badly damaged, it had limited radioactive products escape outwards.

• The accident was classified as Level 5

• 1980 - Saint Laurent des Eaux, France

• The worst nuclear accident in France

• March, 1980 --- A failure in the cooling system caused the melting of a fuel channel in the Saint Laurent A2 reactor.

• Classified as Level 4

• No radioactive material was released outside the plant.

• 1986 - Chernobyl, Ukraine

• The worst nuclear accident in history

• April, 1986 --- there was the largest nuclear accident in the history of nuclear power in Chernobyl by a several human errors in the course of a previously planned test.

• It was classified as level 7 ("major nuclear accident")

• 1987 - Goiânia, Brazil

• September 1987 --- the city of Goiânia in Brazil had a radioactive contamination accident.

• Two men robbed a teletherapy device and extracted a cesium capsule from his protective housing what made it a radioactive cesium-137 source.

• One of the worst radiological incidents worldwide

• Level 5 on the INES scale. Residences and public places are severely polluted.

• Four people died and 28 suffered radiation burns.

• As part of decontamination process, several buildings were demolished and farmland was removed.

• 1999 - Tokaimura Uranium Fuel Treatment plant, Japan

• In September 1999 --- due to human error.

• The accident was classified as level 4 according

• Amounts of radiation released to the outside were very small, and within the limits and within the site.

• The damage produced in the equipment and biological barriers was significant, addition to worker exposure fatal.

• 2011 - Fukushima, Japan

• March,11 2011 --- one of the worst nuclear accidents in history after the Chernobyl nuclear accident.

• An earthquake measuring 8.9 on the Richter scale near the northwest coast of Japan and a subsequent tsunami affected severely the Fukushima nuclear power plant in Fukushima.