Combustion of 1 atom of C => 4 eV; Fission of 1 atom of U => 200 MeV
In thermal reactors, the fission is caused by thermal neutrons having energy less than 0.025 eV. This type of reactor uses natural uranium as fuel. The neutrons generated during fission posses very high energy which are slowed down with the help of a moderators to reduce the energy of neutrons less than 0.025 eV. In fast reactors, fission is basically caused by neutron possessing energy more than 1 MeV. Another important process that is taking place in the fast reactor is breeding of fissile material.
In the first stage of our programme we have 12 PHWRs and 2 boiling water reactors operating with high capacity ratio. 8 more reactors are under construction and several other are planned to have potential od generating 10 GWe. A fast breeder test reactor (FBTR) of 40 MW thermal capacity is operating and has given us experience in fast breeder reactor technology. In this category, a 500 Mwe Prototype Fast Breeder Reactor (PFBR) is under construction. We have now initiated the third stage also with a 30 MW thermal reactor named KAMINI which uses thorium fuel. As a futher development in this stage an Advance Heavy Water Reactor (AHWR) and Compact Heavy Water Reactor (CHTR) are being developed. The development of ADS I.e Accelerated Driven Systems can enable early introduction of Thorium on a large scale.
WELCOME TO OUR SYMPOSIUM PRESENTATION
BARC roadmap of R & D for the thermo-chemical process based hydrogen production Demonstration using 600 MW Th HTR : ~ 80,000 m 3 H 2 /hr Demonstration with metallic chemical reactors :~ 13 m 3 H 2 /hr Lab scale demonstration : ~ 50 L H 2 /hr Early R&D -Studies on reactions & separations Experimental studies for improving specific processing methods Evaluation & Development of materials System design : Process, chemical reactors FLOWSHEETING Process simulation using chemical process simulator
High temperature electrolysis is more efficient and needs less electricity. For this process, nuclear reactors can supply both - high temperature heat & electricity.
High Temperature Steam Electrolysis (HTSE)
A high temperature nuclear reactor coupled with a steam electrolyser would be extremely efficient with a thermal –to-hydrogen conversion efficiency of –55%
Part of the energy needed to split the water is added as heat instead of electricity, thus reducing the overall energy required and improving process efficiency
Super heated steam (at 850 ° C) is introduced at the cathode where hydrogen is separated and oxygen ion passes through a conducting ceramic membrane (usually Yttria Stabilized Zirconia, YSZ) and liberated at anode
HTSE cell and components are similar to SOFC
BARC is developing a 5 kW SOFC system
SOFC development will ease switch over to steam electrolysis system
High Temperature Steam Electrolysis (Tubular Geometry)
Nuclear hydrogen production system being developed in BARC is to satisfy total energy needs of a region in the form of hydrogen, electricity and potable water
Several innovations in the areas of fuel, materials, passive reactor safety, efficient heat removal systems & liquid heavy metal coolant technology mark CHTR configuration.
Nuclear Power is the greatest facilitator of energy security in countries with inadequate domestic energy resources REACTOR Requirement of natural uranium for a 1000 MWe Nuclear Power Plant: ~ 160 t /Year. Requirement of coal for a 1000 MWe Coal fired plant ~ 2.6 million t / Year (i.e. 5 trains of 1400 t /Day)
'The ice is melting much faster than we thought' “ Even if they (opponents of nuclear energy) were right about its dangers, and they are not, its worldwide use as our main source of energy would pose an insignificant threat compared with the dangers of intolerable and lethal heat waves and sea levels rising to drown every coastal city of the world. We have no time to experiment with visionary energy sources; civilisation is in imminent danger and has to use nuclear - the one safe, available, energy source - now or suffer the pain soon to be inflicted by our outraged planet.” - Eminent Environmental Scientist, James Lovelock, The Independent, May 24, 2004
First commercial nuclear power stations started operation in 1950s.
440 commercial nuclear reactors operating in 31 countries
360,000 MWe is the total capacity.
Supply of 16% of the world's electricity
56 countries operate a total of 284 research reactors.
Development of Nuclear Power - Chronology 1970's – Oil Shock 1979 - TMI Accident 1986 - Chernobyl Accident Major Events Affecting Growth of Nuclear Power 1990's – Liberalisation of electricity market and availability of cheap gas
Natural uranium that is mined from the ground is 0.7% U-235 and 99.3% U-238.
Slow Neutrons can initiate a fission of uranium 235 (U-235), an isotope of uranium that occurs in nature.
The result of the fission is
Fission products that are radioactive,
Fast neutrons (~ 2.5 neutrons per fission)
The fission reaction Fission of 1 gm of U-235 per day generates ~1 MW Power 92 U 235 + 0 n 1 36 Kr 92 + 56 Ba 141 + 3( 0 n 1 ) + Energy 92 U 235 + 0 n 1 42 Mo 95 + 57 La 139 + 7( -1 e 0 ) + 2( 0 n 1 ) + Energy Mass 'm1'= 236.0526 g Mass 'm2'= 235.8332 g Difference in mass Δm = 0.2194 gm E = Δm * c 2 c, velocity of light = 3 x10 8 m/s Neutron Nucleus n Radiation Fission Fragments ~200 MeV of Energy Compound Nucleus in an excited state of high internal energy Fast-n
The fast neutrons have a low probability of inducing further fissions (but used as such in fast reactors), and hence generating more neutrons thus sustaining a chain reaction.
So in thermal reactors, we need to slow down the neutrons (i.e., thermalise or moderate them), which we do by using a moderator such as water (Heavy Water or Light water).
Slowing down (thermalisation or moderation) of fission neutrons facilitates lower critical mass, but leads to some loss of neutrons through absorption in the moderator Energy distribution of fission neutrons peaks at ~ 0.7 MeV with average energy at ~ 1.9 MeV. Variation of fission cross-section (barns) of U-235 with neutron energy (eV) Thermal Reactors Fast Reactors Cross-section : The effective target presented by a nucleus for collisions leading to nuclear reactions . 1 barn = 10 -24 cm 2
Uranium-235 is the only naturally occurring fissile isotope.
Plutonium-239 and Uranium-233 are man-made fissile isotopes which can be produced in a reactor.
Uranium 238 (99.3% of natural uranium) on absorbing neutrons in a nuclear reactor, gets converted to Plutonium-239.
Thorium-232, another naturally occurring element, on absorbing neutrons in a nuclear reactor, gets converted to Uranium-233.
The converted fissile materials (Pu-239 and U-233) can be recovered by reprocessing the spent fuel coming out of a reactor .- Closed Nuclear Fuel Cycle
In breeder reactors (practically, Fast Breeder Reactors) it is possible to produce more fissile material than that gets consumed.
Conversion of fertile material to fissile material is made possible by neutron capture reactions 92 U 238 + 0 n 1 92 U 239 + (Fertile) 93 Np 239 + (Fissile) 94 Pu 239 + (n, ) 90 Th 232 + 0 n 1 90 Th 233 + (Fertile) 91 Pa 233 + (Fissile) 92 U 233 + (n, )
Nuclear reactors operating on fission are broadly classified into two types Classification of Reactor Systems
Fission is sustained primarily by thermal neutrons ( E ~ 0.025 eV).
Moderator (Ordinary water, heavy water, graphite, beryllium) is required to slow down the high energy fission neutrons. Large core.
Very high fission cross-section for thermal neutrons, less fuel inventory .
Fission is sustained primarily by fast neutrons (E ~ 1 MeV)
No moderator used. Compact core. High core power density – liquid metal or helium gas as coolant.
Higher number of neutrons available for capture in fertile material. Breeding possible.
There are two options for a “Nuclear Fuel Cycle” : “Open”, and “Closed” FRESH FUEL RECYCLED FUEL FABRICATION REPROCESSING REFINING (U & Th CONCT.) 235 U ENRICHMENT NUCLEAR POWER PLANT SPENT FUEL WASTE CONDITIONING MINING U & Th ORES CLOSED CYCLE OPEN CYCLE WASTE DISPOSAL Th 232, U 238 U 233, Pu 239 FISSION PRODUCTS ENERGY
Main attributes of nuclear energy relevant for electricity and hydrogen generation
Very large resource
Suitable for large unit sizes for meeting urban and concentrated industrial demands
No CO 2 emissions
Relatively insensitive to fuel price increase
Capability to produce very high temperature process heat
India has adopted a closed nuclear fuel cycle for its indigenous programme
To facilitate wide-spread and long term use of nuclear power a sustainable nuclear fuel strategy, based on closed nuclear fuel cycle and thorium utilisation is essential.
Taking cognisance of its resource position, the Indian priority for adopting this strategy has been high.
The Indian nuclear power programme, therefore, has three major stages:
Nat. U in PHWRs
Pu in FBRs
U-233, Th in advanced reactors [a possibility of synergy with Accelerator Driven Systems (ADS)].
The three stage Indian Nuclear Power Programme aims to achieve long-term energy security through self-reliance. 3 rd Stage: Thorium- 233 U based reactors 2 nd Stage: Fast Breeder Reactors using Pu as fuel and breeding Pu and 233 U. 1 st Stage: Pressurised Heavy Water Reactors using Natural Uranium as fuel and producing Plutonium which is recovered in reprocessing plants for initiating the 2 nd Stage
The current Indian nuclear power reactors belong to six different configurations DIFFERENT POWER REACTOR CONFIGURATIONS ORDINARY WATER MODERATED REACTORS PRESSURISED WATER Cooled HEAVY WATER MODERATED REACTORS FAST BREEDER REACTORS BOILING WATER Cooled PRESSURISEDHEAVY WATER Cooled Tarapur 1&2 Rajasthan Kalpakkam Narora Kaiga Kakarapar, Tarapur Kalpakkam GAS COOLED REACTORS OTHER REACTORS Kundankulam BOILING WATER Cooled AHWR CHTR
Current status of the Indian nuclear power programme
Stage - III
Thorium Based Reactors
30 kWth KAMINI- Oper.
300 MWe AHWR- Under development
CHTR – Under design.
POWER POTENTIAL Very Large. Availability of ADS can enable early introduction of Thorium on a large scale.
Stage - I
5 - Under construction
Several others planned
POTENTIAL 10 GWe
2 BWRs- Operating
2 VVERs- Under
Stage – II
40 MWth FBTR- Oper.
500 MWe PFBR- Under construction
POTENTIAL 350 GWe
Among the best performing in the world Largest number of reactors under construction in any country in the world today
Indian Nuclear Power Programme till 2020 21,080 13,900 Projects planned till 2020 PHWRs(8x700 MWe), FBRs(4x500 MWe), LWRs(6x1000 MWe), AHWR(1x300 MWe) 7,180 500 PFBR at Kalpakkam under construction ( 1 X 500 MWe) 6,680 2,000 2 LWRs under construction at Kudankulam(2x1000 MWe) 4,680 1,420 5 PHWRs under construction at Tarapur (1x540 MWe),Kaiga (2x220 MWe), RAPS-5&6(2x220 MWe) 3,260 3,260 13 reactors at 6 sites under operation Tarapur, Rawatbhata, Kalpakkam, Narora, Kakrapar and Kaiga CUMULATIVE CAPACITY (MWe) CAPACITY (MWe) REACTOR TYPE AND CAPACITIES
Deployment of passive safety features – 3 days grace period.
No need for planning off-site emergency measures.
Power output – 300 MWe with 500 m 3 /d of desalinated water.
Design life of 100 years.
AHWR is a vertical pressure tube type, boiling light water cooled and heavy water moderated reactor using 233 U-Th MOX (Mixed Oxide) and Pu-Th MOX fuel.
The 3.5 m long AHWR fuel clusters have a design which is unique in the world.
Thorium bearing fuel [(Th + Pu)O 2 MOX, (Th + 233 U)O 2 MOX]; Enrichment 2.5% (top half) & 4% (bottom half) in the former
Central (ZrO 2 -Dy 2 O 3 ) displacer rod
Emergency core cooling water injected into the cluster through the holes in displacer rod
Low pressure drop design
Fuel Cluster Cross-Section Bottom Tie Plate Top Tie Plate Water Tube Fuel Pin Displacer Rod
These fuel clusters reside in 452 out of 505 lattice positions in a vertical core having Heavy Water moderator Typical incore detector (36 positions) 452 Fuel Channels 4 4 4 41 Shim Rod SR Regulating Rod RR Absorber Rod AR Shut off Rod N 20,000 MWd/Te 23,500 MWd/Te 30,000 MWd/Te
The reactor is located in the basement with four steam drums located at the top GDWP Header Moderator System Tail Pipe Tower Down comers Advanced Accumulators Isolation Condensers Feeder pipes MHT Purification system PW Header ECC Pipes Tail pipes Steam drums Vertical Sectional View
Boiling water under natural circulation (i.e., no pumps are used in the main coolant circuit) cools the fuel clusters Heat removal from core under both normal full power operating condition as well as shutdown condition is by natural circulation of coolant.
Even if the largest size pipe suddenly breaks, the Emergency Core Cooling System (ECCS) will flood the core with cold water, without any operator or control action Passive injection of cooling water, initially from accumulator and later from the overhead GDWP, directly into fuel cluster. (Th + Pu)O 2 24 pins (Th + U 233 )O 2 30 pins Water Tube Displacer Rod
The reactor has unique advanced safety features to reliably cool it and shut it down even with human failure, power failure, and failure of all wired controls. Pressure 70 bar Pressure 71 bar Pressure 76.5 bar Pressure 82 bar Steam overpressure can passively shut down reactor
“ There is no power as costly as no-power” – Homi Bhabha
This presentation focuses on the entire nuclear fuel cycle. It is designed to explain the negative effects caused by the use of and production of nuclear energy. It takes you through the cradle to grave lifecycle of nuclear energy, paying particular attention to the social, environmental, and public health impacts of the processes associated with nuclear energy.
Nuclear energy was first discovered in 1934 by Enrico Fermi. The first nuclear bombs were built in 1945 as a result of the infamous Manhattan Project. The first plutonium bomb, code-named Trinity, was detonated on July 16, 1945 in New Mexico. On August 6 th 1945 the first uranium bomb was detonated over Hiroshima. Three days later a plutonium bomb was dropped on Nagasaki. There is over 200,000 deaths associated with these detonations. Electricity wasn’t produced with nuclear energy until 1951.
Radiation is the result of an unstable atom decaying to reach a stable state. Half-life is the average amount of time it takes for a sample of a particular element to decay half way. Natural radiation is everywhere—our bodies, rocks, water, sunshine. However, manmade radiation is much stronger. There are currently 37 radioactive elements in the periodic table—26 of them are manmade and include plutonium and americium (used in household smoke detectors).
There are several different kinds of radiation: alpha radiation, beta radiation, gamma rays, and neutron emission. Alpha radiation is the release of two protons and two neutrons, and normally occurs in fission of heavier elements. Alpha particles are heavy and cannot penetrate human skin, but are hazardous if ingested. Beta radiation is when a neutron is changed to a proton or visa versa, beta radiation is what is released from this change. Beta particles can penetrate the skin, but not light metals. Gamma rays is a type of electromagnetic radiation which is left over after alpha and beta are released and include X-rays, light, radio waves, and microwaves.
Penetration of Radioactive particles Source: http://www.ratical.org/radiation/NRBE/NRBE3.html
Radiation is sometimes called ionizing radiation because ions are created with the passage of the alpha, beta, and gamma rays. The effect of radiation is on a cellular level—changing its functionality (causing cancer or inherited birth defects) or killing it. Depending on the information source, radiation doses are measured in rems or sievert, in any case 100 rem = one sievert. An exposure of 100 Sv will cause death within days, 10-50 Sv will cause death from gastrointestinal failure in one to two weeks, and with an exposure of 3-5 Sv will cause red bone marrow damage half of the time. Severe affects consist of burns, vomiting, hemorrhage, blood changes, hair loss, increased susceptibility to infection, and death. With lower levels of exposure symptoms are cancer (namely thyroid, leukemia, breast, and skin cancers), but also include eye cataracts. The radiation can also affect DNA causing mutations that change individuals’ genes and can be passed on to future generations. The current occupational dose recommended by the International Commission for Radiological Protection is 50 mSv per year. The average radiation dose per year for non-nuclear workers is about one mSv.
Uranium is usually mined similarly to other heavy metals—under ground or in open pits—but other methods can also be used. After the uranium is mined it is milled near the excavation site using leaching processes. The mining process explained here is a combination of two of major mines in Australia. Then we will look at the Navajo uranium miners who were some of the first uranium miners. Next I will explain some of the other community and environmental impacts associated with the mining processes.
Uranium ore is usually located aerially; core samples are then drilled and analyzed by geologists. The uranium ore is extracted by means of drilling and blasting. Mines can be in either open pits or underground. Uranium concentrations are a small percentage of the rock that is mined, so tons of tailings waste are generated by the mining process.
The ore is first crushed into smaller bits, then it is sent through a ball mill where it is crushed into a fine powder. The fine ore is mixed with water, thickened, and then put into leaching tanks where 90% of the uranium ore is leached out with sulfuric acid. Next the uranium ore is separated from the depleted ore in a multistage washing system. The depleted ore is then neutralized with lime and put into a tailings repository.
Meanwhile, the uranium solution is filtered, and then goes through a solvent extraction process that includes kerosene and ammonia to purify the uranium solution. After purification the uranium is put into precipitation tanks—the result is a product commonly called yellowcake.
In the final processes the yellow cake is heated to 800˚Celcius which makes a dark green powder which is 98% U 3 O 8 . The dark green powder is put into 200 liter drums and loaded into shipping containers and are shipped overseas to fuel nuclear power plants.
Australia and Canada are currently the biggest Uranium miners. The aforementioned process that takes place in Australia is exported because Australia does not have a nuclear energy program. The mining in Australian is primarily open pit, while the mining in Canada is mostly underground. Following is two charts—one is the major uranium producing countries, the other is of the major corporations that actually do the mining.
Production in 2000 34,746 Total world 422 others 319 France 200 India (est) 500 Czech Republic 500 Ukraine (est) 500 China (est) 878 South Africa 1,456 USA 1,752 Kazakhstan 2,000 Russia (est) 2,350 Uzbekistan 2,714 Namibia 2,895 Niger 7,578 Australia 10,682 Canada 2000 Priargunsky 2018 KazAtomProm 2239 Rossing 2400 Navoi 3564 ERA 3693 WMC 6643 Cogema 7218 Cameco tonnes U company
Another method of uranium mining is in-situ leaching. This method is used because there is reduced hazards to the employees of the mines, it is less expensive, and there are no large tailings deposits. However, there are also several significant disadvantages including ground water contamination, unknown risks involving the leaching liquid reacting to the other minerals in the deposit, and an inability to restore the leaching site back to natural conditions after the leaching process is done.
15% by-product 16% in situ leach (ISL) 40% underground 29% open pit
Communities located near the mines and the workers in the mines are most heavily impacted by the uranium mining industry. The Navajo Indians in Arizona were the first uranium miners back in the 1940’s to the 1970’s. Early on, little was understood about the dangers of uranium exposure, and as a result there have been many illnesses related to the mining. Despite safety efforts, uranium miners are still at risk. In addition, tailings dams have broken and contaminated drinking water in the communities near the mines.
Some of the first uranium miners were Navajo Indians in New Mexico and Arizona. In the article by Timothy Benally “Navajo Uranium Miners Fight for Compensation,” Benally explains how the Navajo people came to know the dangers of uranium exposure and how they are getting compensated. Vanadium mining started there around 1918, but uranium mining did not start until after the Second World War. Before uranium was discovered there, it was not clear what this element was, and as a result the tailings from the Vanadium (that contained high levels of uranium) were not stored properly—leading to excessive human exposure and environmental impacts on the water supply and food production. To make things worse, once the element was discovered, there was a large prospecting movement throughout the reservation. In addition, the major corporations that ran these mines, the Vanadium Corporation of America and the Kerr-McGee, companies paid unfairly low wages and did not warn the workers of the dangers of the uranium. It was not until people got ill and were dieing that the workers and their families found out. In 1960 the workers and their families started the Uranium Radiation Victims Committee, which sought to warn other workers and families of the danger of exposure to uranium, but because there was little alternative employment, many kept their jobs in the mines anyway. In 1990, a bill was passed in congress to compensate radiation exposure victims, and since then the Office of Navajo Uranium Workers has sought to identify exposed workers and to provide medical care. There are currently 2,450 registered workers, and 412 recorded deaths of workers.
Floyd lost several brothers and other relatives to uranium related illnesses. He witnessed calves that had been born defected and sheep that have had lung problems. His view is that the US government wanted to see what happens to people exposed in these conditions. The water has been contaminated and, through the tributaries, so has the land. He says that the US government will only compensate someone if they have lung cancer, but he says that his brothers had sores all over their bodies .
“ Uranium threatens the health of mine workers and the communities surrounding the mines. According to the International Physicians for the Prevention of Nuclear War, uranium mining has been responsible for the largest collective exposure of workers to radiation. One estimate puts the number of workers who have died of lung cancer and silicosis due to mining and milling alone at 20,000. Mine workers are principally exposed to ionizing radiation from radioactive uranium and the accompanying radium and radon gases emitted from the ore. Ionizing radiation is the part of the electromagnetic spectrum that extends from ultraviolet radiation to cosmic rays. This type of radiation releases high energy particles that damage cells and DNA structure, producing mutations, impairing the immune system and causing cancers.”
According to a Planet Ark article online, “Australia Uranium Mines Come Under Spotlight,” Australia currently has four uranium mines—Ranger, Beverley, Honeymoon, and Olympic Dam—and they have plans for six more. The article is about an inquiry that the Australian government is making into the mining business at the request of the Aborigines and environmental groups. In 2002 there were two incidents involving the Ranger mine in which the stockpile with low-grade ore got downstream, and was not immediately reported. In May of 2002 the Beverley mine spilled uranium-contaminated water for the fourth time. The Beverley mine is owned by a subsidiary of a US company called General Atomics. Even worse than the Beverly mine record is that of Olympic Dam in which hundreds of thousands of liters of uranium mining slurry was leaked from a storage tank—for the seventh time.
On July 16, 1979 the largest spill of radioactive isotopes in the United States, other than weapons testing was in the form of uranium tailings erupted from the Church Rock Dam. The broken dam released eleven hundred tons of mill waste and ninety million gallons of contaminated liquid in the Rio Puerco area immediately effecting over 350 Navajo ranching families, and endangering the water supply of New Mexico, Arizona, Las Vegas, and Los Angeles—including Lake Mead. The cause of the breach was a dam that was not built to code—an accident that could have been prevented if the proper authorities had done their jobs. The United Nuclear Corporation, a corporation with a history of leaks, owned the dam. They have acknowledged fifteen tailing spills between 1959 and 1977—seven of those were dam breaks—and at least ten of the spills got into major water systems.
“… uranium mining, a polluting activity that devastates large areas. Uranium ore sometimes contains as little as 500 grams recoverable uranium per 1000 kilograms of earth. So, enormous amounts of rock have to be dug up, crushed and chemically processed to extract the uranium. The remaining wastes, which still contain large amounts of radioactivity, remain at the mines. These "tailings" are often stored in a very poor condition, resulting in the contamination of surface- and groundwater.”
We will start the nuclear fuel cycle with a brief explanation of how nuclear energy works, the enrichment process, and then power reactors. Following will be information on Three Mile Island and Chernobyl, the risk of reactor leaks, and the impacts on the communities and the environment. Then we will discuss the nuclear weapons program, including the use of depleted uranium, Hiroshima and Nagasaki, weapons testing, and the effects on soldiers, victims, communities, and the environment.
Nuclear energy —synonymous with atomic energy, is the energy produced by fission or fusion of atomic nuclei.
Atoms —are made of three main parts: protons, neutrons, and electrons . The protons and neutrons make up the center of the atom while the electrons orbit around the center .
Atomic number —the number of protons in an element that identifies it.
Isotope —if an atom has a different number of neutrons from protons. Isotopes, measured by their total weight called “mass number” are the sum of neutrons and protons. Some isotopes are unstable and will decay to reach a stable state—these elements are considered radioactive.
Ion —if an atom has a different number of electron from protons.
Fission — occurs when an atoms nucleus splits apart to form two or more different atoms. The most easily fissionable elements are the isotopes are uranium 235 and plutonium 239. Fissionable elements are flooded with neutrons causing the elements to split. When these radioactive isotopes split, they form new radioactive chemicals and release extra neutrons that create a chain reaction if other fissionable material is present. While Uranium, atomic number 92, is the heaviest naturally occurring element, many other elements can be made by adding protons and neutrons with particle accelerators or nuclear reactors. In general, the fission process uses higher numbered elements.
Fusion —is the combining of one or more atoms—usually isotopes of hydrogen, which are deuterium and tritium. Atoms naturally repel each other so fusion is easiest with these lightest atoms. To force the atoms together it takes extreme pressure and temperature, this can be produced by a fission reaction.
To enrich uranium it must be in the gas form of UF6. This is called conversion. The conversion diagram shown here is from Honeywell. First the yellow cake is converted to uranium dioxide through a heating process (this step was also mentioned in the mining process). Then anhydrous hydrofluoric acid is used to make UF4. Next the UF4 is mixed with fluorine gas to make uranium hexafluoride. This liquid is stored in steel drums and crystallizes.
Uranium enrichment increases the amount of U235 in comparison to U238. Domestic power plants use a mixture that is 3-5% U235, while “highly enriched uranium” is generally used for weapons, some research facilities, and naval reactors. Domestic reactors usually require fuel in the form of uranium dioxide and weapons use the enriched mix in the form of a metal. The conversion and enrichment process is very dangerous because not only is the uranium hexafluoride radioactive, it is also chemically toxic. In addition, if the uranium hexafluoride comes in contact with moisture it will release another very toxic chemical called hydrofluoric acid. There have been numerous accidents during the conversion and enrichment process. Depleted uranium is the waste that is generated from the enrichment process.
After being enriched, the UF6 is taken to a fuel fabrication facility that presses the powder into small pellets. The pellets are put into long tubes. These tubes are called fuel rods. A fuel assembly is a cluster of these sealed rods. Fuel assemblies go in the core of the nuclear reactor. It takes approximately 25 tonnes of fuel to power one 1000 MWe reactor per year. The picture on the right is a fuel assembly.
Radioactive materials are transported from the milling location to the conversion location, then from the conversion location to the enrichment location, then from the enrichment location to the to the fuel fabrication facility, and finally to the power plant. These materials are transported in special containers by specialized transport companies. People involved in the transport process are trained to respond to emergencies. In the US, Asia, and Western Europe transport is mainly by truck, and in Russia mainly by train. Intercontinental transport is usually by ship, and sometimes by air. Since 1971 there has been over 20,000 shipments with no incidents and limited operator exposure.
There are usually several hundred fuel assemblies in a reactor core. There are several types of reactors, but they all use a controlled fission process with a moderator like water or graphite. During the fission process, plutonium is created and half of the plutonium also fissions accounting for a third of the energy. The fission process makes heat that is converted to energy (see following diagrams). Pictured above is the Diablo Canyon reactor in California.
1-3) power is generated or imported. 4) high voltage power lines make up the “grid” that connects power generators and neighborhood substations. 5) substation steps down the power and connects to the distribution system. 6) the distribution systems link to most customers.
PRW —Pressurized Water Reactor—does not boil, but uses the pressure of the water to heat a secondary source of water that generates electricity. Most popular (accounts for 65% of reactors world wide). Considered a light water reactor.
BRW —Boiling Water Reactor—boils water (coolant) that makes steam to turn turbines. Conducive to internal contamination. Also considered a light water reactor.
RBMK —Graphite-moderated pressure tube boiling-water reactor similar to BWR but uses graphite and oxygen. Complex and difficult to examine.
CANDU —Canadian Deuterium Uranium—Doesn’t use enriched fuel. Has lots of tubes and internal contamination issues.
Magnox —Gas cooled reactor. Cooled with carbon dioxide or helium, and uses natural uranium. (UK and France).
AGR —Advanced Gas-cooled—also cooled with carbon dioxide or helium. Uses enriched uranium. (UK).
Fast Breeder —high temperature gas reactor. Uses U235, U238, and Plutonium 239. Very dangerous because it uses liquid sodium in the primary circuit and in inflammable with air and explosive with water.
Reactor pose a serious threat radiation threat—especially to the employees and surrounding communities. Recently the New York times featured an article “Extraordinary Reactor Leak Get’s the Industries Attention.” The implication is that if this reactor can leak, so can others. Typically, the reactors develop boric acid under their lids—which eats away at the steel encasement (fixable), but this leak is in at the bottom of a reactor.* In an article featured on CorpWatch, “Bechtel’s Nuclear Nightmares” talks about a reactor that the Bechtel corporation built in San Onofre—that’s been shut down since 1992 for lack of safety upgrades. The problem is that there is no place to permanently send the reactor to and is a risk because it was built on a fault line.** Three Mile Island and Chernobyl are two of the worst incidences of reactor breaches and are explained in the following slides.
Three Mile Island is a pair of PRW’s. The second one was built in a hurry for tax purposes (started operation on December 30, 1798 to meet deadline). On March 28, 1979, the Pilot Operated Relief Valve was stuck open and caused pressure to be released from the primary cooling system. The fuel rods came apart and radioactive material discharged into the sky. Two days later 3,500 pregnant women and children were evacuated. Although there were no official instructions to do so, many others left as well. Numerous residents in the aftermath developed various cancers and thyroid diseases.
Chernobyl had the RBMK design. In an experiment, technicians let the power of reactor 4 fall, and on April 26, 1986 the result was rapid power levels rising inside the core— melting fuel and causing a reactor containment breach—in addition to an internal hydrogen explosion. The top of the reactor blew off and spewed radioactive material into the atmosphere for 10 days.
Thirty people died in direct relation to the accident. They were the workers in the plant and the people who assisted in the cleanup. Approximately 2,500 additional deaths were related to the accident. Since the accident rates of Thyroid cancer has risen significantly. The rate of thyroid cancer in children 15 years and younger increase from 4 to 6 per million to 45 per million in the Ukraine region between 1986 to 1997 (compared to 1981 to 1985). 64% of these cases were in the most contaminated regions.
116,000 people were evacuated from 1990 to 1995 and 210,000 were resettled. Major infrastructure had to be rebuilt. There was also a shortage of electricity. Agricultural activities had to be reduced, which lead to a reduction in income.
Radioactive fall out spread throughout the Ukraine and Europe, and eventually the whole northern hemisphere. In the local ecosystem (10 km radius) coniferous tress and small mammals died. The natural environment is recovering but there may be long-term genetic effects.
Nuclear weapons fall under two categories—fission weapons and fusion weapons. Fission is splitting the nucleus of an atom into two or more elements, which causes a huge amount of energy to be released. In addition if there is left over neutrons they will cause fission in other elements—sustaining a chain reaction. Fusion is almost the reverse because it requires the putting together of two nuclei. The Hydrogen bomb is a fusion weapon, while weapons that use U235 and Pu239 are fission weapons. A thermonuclear weapon detonates in three steps: fission chain reaction, fusion reaction, and then fission again. When a thermonuclear weapon explodes, there is an explosion of neutrons and gamma rays that causes a silent flash of heat and light, followed by the extreme pressure of a mushroom cloud that raises millions of tons of earth resulting in nuclear fallout.
Production plants involved in the manufacturing of weapons have also done significant harm to the environment and surrounding communities. Because the US was in such a hurry to make as many nuclear weapons as possible, there are many severely contaminated environments surrounding these sites. Of special note are Hanover Washington (evacuated in 1943)*, Rocky Flats Colorado (plutonium spontaneously igniting cause two major fires)*, and Fernald Ohio (contaminated ground water)**. All three of these sites are currently in the process of being cleaned up.
In New Mexico on July 16, 1945 was Trinity test, the first atomic explosion. The Trinity test spread radioactive material over a 300 square mile area, including Santa Fe, Las Vegas, and Trinidad (Colorado). Later two bodies were discovered 20 miles from the detonation location—the couple had been living in a nearby canyon in an adobe house.
The Hiroshima bomb was nicknamed “little boy” (on the left) and was detonated on August 6, 1945 killing approximately 140,000 by the end of that year—and an estimated total of 200,000 altogether. “Fat Man” (on the right) was dropped three days later on Nagasaki killing approximately 70,000 people. Entire families were wiped out. The effects of the radiation caused birth defects in some of the survivors’ children, while others could no longer have babies. The physical, psychological, and environmental impacts of these atrocities can hardly be put into words.
Since 1945 there has been 2,050 nuclear weapons tests world wide.* This picture is of “Dog Shot” in the Nevada desert in 1951. The second series of tests, the first series with large scale troops present. **
“ The morbidity study for Crossroads contains data received from 1,572 veterans of the 42,000 participating veterans. This represents a sample size of 3.74 %. The average death age of the 380 deceased veterans is 57 years. The incident of all types of cancers in deceased Crossroads Veterans is 59%.
The Incidence of all types of cancer in the 1572 reporting Veterans is 35%.
The leading cancer types, ranging from 23% down to 6%, are skin, prostate, lymphoma, lung, urinary, colon, and esophagus.
These percentages for the most part are seen in data on Ranger, Greenhouse, Buster-Jangle, Trinity, Tumbler-Snapper, Upshot-Knothole, Castle, and Redwing. Information from veterans from other tests is needed before an analysis can be performed.
Further study and data is needed to isolate target area, ie, tests, units, ships.”
Nuclear weapons devastate large areas of land with a forceful blast and intense heat. The land around the blast zones are contaminated with radioactive debris. The mushroom clouds break up slowly, and travel with weather patterns which distributes fallout across the globe. Many of the tests focus in rural, mainly uninhabited areas, and as a result disproportionately affect indigenous and other peoples living in these rural areas. Other important test sites that have drastically impacted indigenous peoples include the Marshall Islands (US) and Mururoa (France).
Another significant threat is planes armed with these weapons can (and have) crashed; and submarines have also sunk into the ocean. In addition there have been incidents in which material has just been dumped as well. May estimates that there are 60 nuclear weapons and 10 reactors on the ocean floor from submarines, plane crashes, and dumping. Although very strong casings likely guard them, the casings will eventually corrode resulting in radioactive contamination of our ocean and marine life.
Depleted uranium is what’s left over from the enrichment process and is radioactive. Uranium is a heavy metal that can easily penetrate amour. Depleted uranium is currently being used in Iraq, and was used in Kosovo, the Gulf War, and Bosnia. When a depleted uranium burns, radioactive particles are release into the air. Depleted uranium is also a toxic hazard.
There four different kinds of waste: High-level (spent fuel and plutonium waste), transuranic (contaminated tools and clothes), low and mixed low-level (hazardous waste from hospitals), and uranium mill tailings. In the US there is approximately 91 million gallons of high-level waste, 11.3 million cubic feet of transuranic waste, 472 million cubic feet of low and mixed low level waste, and 265 million tons of uranium tailings.
Many facilities store their own waste on site, but they are quickly running out of space. Other sites are in the process of being cleaned, but there is no place to store the waste. Part of the problem is the half-life. Half-life is how long it takes for an unstable element to decay half way. Uranium 238 takes 4.5 billion years. Typically, after ten “half-lives” the element is considered safe. Nuclear waste lacks permanent safe storage. Temporary storage is being proposed for the Skull Valley Goshute Indian reservation, and permanent storage may be in Yucca mountain. Mean while waste and tailings are pilling up.
According to the Skull Valley Goshute Indian website the Goshute Indians in Utah recently made an agreement with a private utility to temporarily store 40,000 metric tons of spent nuclear fuel. The Goshute reservation is 18,000 acres, and already surrounded by other polluting industries. To the south of the reservation is the Dougway Proving Grounds—a government chemical and biological weapons testing site. Also to the south is the Intermountain Power Project, which mainly makes coal-fired electricity for California. To the east is a government depository of nerve gas, and to the northeast is a low-level radioactive disposal site and toxic waste incinerator. Finally, in the north is a magnesium production plant. On the Skull Valley Goshute website it is stated that since the reservation is already surrounded by hazardous facilities, and after careful consideration and consultation with the government, scientists, and corporations, they have entered into this agreement.
This is a picture of a ten-million ton pile of uranium tailings. The pile is right next to the Colorado River, and leaks ammonia into it threatening the fish. The owners of the pile when bankrupt, so no the citizens of Moab are waiting for the Department of Energy to clean it up. The clean up will cost an estimated 64 million dollars.
Yucca Mountain located in southern Nevada. Although this location has not been built yet, the plan is to have the waste buried deep in the mountain. Waste would be transported from all over the country in specially design railroad cars and truck trailers. The waste would then be repackaged for final burial. This plan is highly controversial.
Overall, nuclear energy disproportionately effects rural communities and the communities near nuclear facilities. Uranium mining and bombing are particularly detrimental to the environment. Further, the effects of radiation (cancer, illness, and death) are significant. If you find yourself in a situation where you are being exposed to radiation, shield yourself from the blast, and then move as far away from the detonation area as possible (otherwise remain indoors).