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Everybody Needs a Little STEAM
Science, Technology, Engineering, Arts, Math (S.T.E.A.M.)
We need to catch up on biology, chemistry and physics that belong to S.T.E.A.M.6-1 and make the effort to evaluate energy. We need to be certain about what kind of decisions can make a difference in the remaining time left to do so.
What about learning complex science? Is Nuclear Physics so hard to learn? How much do we need? It is complex at the deeper levels but what you need to know is not so far away or hard to find. Between truth and fear lies a lot of fact finding to clear up the misconceptions about nuclear. Once the truth comes out then we can see how the big fossil fuel energy players care more about profits than about the environment. Getting a grasp on the science will also help to lighten your view of what is possible and what is not. Common myths like “all radiation is dangerous” can easily be seen to be false by looking at data that compares exposure levels and knowing that radiation is everywhere. (see radiation Chapter)
The documentary film Pandora’s Promise6-2 uses a powerful analogy right in the title. What “promise?” Robert Stone did a good job of finding a title that represented a journey of discovery. In a Greek myth, Pandora, the first woman, is endowed with seductive charms and when given a gift box labeled “do not open”, she opens it anyway. Out comes all sorts of evil. She manages to close the box before the last item escapes. That last item is “hope.”
The film shows how five environmentalists with an antinuclear outlook discover “hope” in the form of nuclear energy. All the previous myths they held started to disappear after inquiring into the real nature of atomic science. The myths were debunked one by one and the future outlook appeared less bleak in the face of climate change.
Nuclear power was a path they never considered until they understood the more immediate danger posed to the planet by climate change and ocean acidification. The fact that China will have double the carbon emissions that the US is projected to have in 30 years and that wind and solar are totally inadequate to bring poor countries out of poverty it is imperative, if there is any “hope”, that it is going to be nuclear energy that will replace coal.
The unwillingness of so many protesters to actually try to understand the science and relative value both economically and environmentally is another example of the human failure. Several nuclear reactors in the US have recently been shut down due to market driven factors. Kewaunee6-3 in Wisconsin6-4 and Vermont Yankee6-5 were forced out of business partly because of the existence of cheap natural gas. But the other factor is lack of public awareness. Too many people see the closing of a nuclear power plant as a victory. I am one that feels both angry and sad that fear of radiation, and I mean any radiation is very much part of the North American psyche. There is a huge difference between the reality and the perception. We need to close this gap.
But the need for the general public to be informed and educated about nuclear energy has never been acknowledged by those who could make a difference. The need for public awareness is still not a phenomenon discussed or explored. Hence the purpose of this book.
Now it makes sense to bring the public, including the gamers, up to speed on the subject of atomic science and how it led to nuclear energy because nobody should be left in the dark worried and confused. At this level governments fail. They don’t properly mandate what is being taught. This chapter will try to be your orientation. Let the politicians catch up later.
What About the Science?
Let’s start by observing our planet. Have you ever wondered how the center of the earth stays hot and keeps molten lava flowing? The planet is billions of years old. Why has it not cooled in that time? It is the presence of uranium, thorium changing from one state to another perpetually releasing energy and heat from radioactive decay 6-6 that causes the rocks to melt. This was only discovered in the last 60 years or so.
The age of planet Earth was first calculated in 1956 using nuclear science by an American geologist Clair Patterson to be 4.5 billion years old6-7 and it was using a method known as radiometric dating based on comparing different isotopes of lead. Another trick discovered in the 1940s was carbon dating. It takes the ratio of two different isotopes of carbon (carbon 12 is constant and carbon 14 decays at 50% every 5,730 years) and is used to accurately measure the age of things up to a maximum of 50,000 years. These techniques would not be possible without the advances in nuclear science.
The story of energy can’t be told without understanding the role the chemists and physicists. In fact the two types of reactors that dominates current research and development could be described as requiring a marriage of the two disciplines.
Background and the Role of the Early Chemists
When Marie Curie decided to do experiments in the late 1800s with a strangely behaving unknown substance, it’s high incidence of activity was brand new territory. Little did she know that she was carrying around radium6-8 in her pockets. The handling of the materials without protection would lead to her eventual death 30 years later of aplastic anemia at age 66. But her accomplishments give women a reason to be proud. She was the first person and only woman to win the Nobel prize twice6-9. She did the world a great service by dedicating her life to understanding radioactive elements, specifically discovering, naming and adding radium (origin of the words “radioactive” and “radiation”) and polonium. (named after her Polish heritage) to the table of elements.
Her relatively long life and the long lives of other nuclear scientists show that radiation is not as bad as people imagine. Marie Curie handled the substances of varying purity and quantity daily without protection yet she lived to be a senior. Radium is only found at trace levels (produced by decaying uranium) because natural radium has largely vanished due to natural decay. What are called the primordial elements are still found if their half lives happen to be older than 2 billion years or so. The longer the half life the lower the radioactivity. The real damage is done if you eat it or breathe it but otherwise our skin is a reasonable block to the radiation that is emitted through the air. The overwhelming majority of nuclear scientists live to an old age without cancer incidence. No matter where a person lives, it would be extremely rare to ever encounter high dose radiation. But even if you work with it or near it daily it is manageable and safe when the right procedures for handling it are made. You may recall the safety gear that visitors were asked to wear in news features about Fukushima. The measures being practiced reflect the attitude of public officials exercising caution that is an over-reaction in an over-regulated safety culture. Those safety suits were completely unnecessary.
Historically, the elusive invisible and atomic universe had been viewed as composed of individual elements that existed alone and unable to bind and create compounds. Discovering properties of natural elements had been a French tradition going back to 1789 when Antoine Lavoisier catalogued 33 of the atomic tables elements6-10. His insights led to the understanding of compounds that had specific molecular structures.
Swedish chemist Jöns Jacob Berzelius would further expand that in 1818 calculating the atomic weights of 45 of the known 49 elements including his personal discovery of Thorium6-11, element 90. Dmitri Mendeleev of Russia in 1869 had developed what became known as a periodic table of 66 elements6-12 ordered according to their chemical properties. This was developed without the knowledge of electron shells or orbitals which did not arrive until 1919.
French chemist Marcellin Berthelot published an important thesis on compounds in 1860 when most chemists believed compounds from organic substances could not be recreated in the lab. Berthelot proved them wrong thus ending the notion of vitalism6-13. He is considered the greatest chemist ever. He was also able to observe something frightening about the power of the atom when he said “Within a hundred years of physical and chemical science, men will know what the atom is. It is my belief when science reaches this stage, God will come down to earth with His big ring of keys and will say to humanity, ‘Gentlemen, it is closing time 6-14.’”
The Early Physicists
The breakthroughs regarding atomic structure made real progress after Albert Einstein’s several discoveries and the proposed models of mathematical modeling based on Brownian motion discovered 28 years earlier by Robert Brown6-15 who observed the motion of dust grains in water. Theories formed by John Dalton 100 years earlier6-16 would be proven true by Jean Baptiste Perrin who used Einstein’s equations to help prove Dalton was correct. Perrin later was awarded a Nobel prize6-17 in 1926. Einstein got his Nobel prize in 1921.
Such a web of discoveries and interconnected thoughts led to advancements that would allow us to send pictures back to the earth from Pluto in 2015 and Mars for the past several years. The space travel technology depends on RTG6-18 devices that are a type of nuclear battery.
Einstein’s Famous Equation
Nuclear energy was not new it was just new to humans. Although we discovered it about 100 years ago nuclear energy was around when the first stars were born and the big bang occurred. But this knowledge is relatively new. Einstein lived in a time when nobody understood this yet. That’s why his insights are all the more incredible.
E=mc2 means “Energy” is equal to some specific mass at rest6-19 multiplied times the speed of light squared. The speed of light is so fast that it is typically a given distance per second. That is 186,000 miles per second. That speed could be expressed as 671,000,000 miles per hour.
What could the mass of an object and the speed of light have in common?
This incredible formula was discovered by Einstein before it was even possible to prove. It does follow that since c is already a very big number, based on the speed of light, that being squared makes it an extra huge amount. Therefore the change in mass must be a small amount but still very significant. So this formula is an equation that demonstrates that it is possible to get a huge amount of energy from a small change in mass. That small change in mass is in fact measurable at the atomic level.
Somehow Einstein also figured out that nothing could go faster than light. He calculated that any mass to reach the speed of light would require a certain number of joules of energy. So when the big less-stable atoms split and change their atomic weight there is a measurable amount of energy released. That energy is expressed as E=mc2 When Einstein produced his equation atoms were not known to be splitting so his anticipation of what was coming was prophetic, to say the least.
Scratching the Surface of Nuclear Physics
The study of nuclear physics is not everybody’s idea of fun. But some basics are essential to getting a grasp of why nuclear energy is not only a dense energy source but it can be and has been made safe to give nuclear plants the best safety records of all power plants6-20.
One of the polarizing factors in the nuclear industry is the variety of nuclear plants that have been created and the numerous schools of thought that accompanies each design. The versatility of the technology is both a blessing and a curse. But they all have common factors we can summarize here.
Reactors require what is called a fissile element from the periodic table. If an element is fissile it is fissionable. Basically, fission is essential to creating nuclear energy.
Many of the heavier elements in the periodic table no longer exist naturally but have been recreated in the laboratory. The elements in existence are the lighter more stable elements. That means most of them are not decaying. If they are decaying it is at a very slow pace.
The only naturally occurring source of nuclear fuel is Uranium and most of the uranium we find is in trace amounts that have been transmuted from plutonium (the uranium we dig up is a low purity daughter element from decaying plutonium – now essentially gone). Thorium has a unique advantage as a power source but it is not a fuel, technically, but later I’ll explain the Thorium Cycle6-21 which produces fissile fuel6-22. We’ll come back to this.
Uranium is found in trace amounts and needs processing to be as pure as needed. The ability to create man made isotopes6-23 of radioactive elements is partly what is keeping the nuclear industry alive. And although expensive to build, Nuclear Reactors are still the cleanest, most efficient electricity producers ever by a long shot and the availability of uranium is not at risk. The economics of nuclear plants needs demystifying. They don’t need to be expensive. For the most part they are expensive as a direct result of pressure from lobbyists and peer groups who fight for greater safety measures for the already very safe reactors. Any pronuclear advocates worth their salt will tell you that nuclear reactors are over-engineered and currently lack a standardized design.
Out of all the different types of reactors available there are three kinds of reactors we need to consider. For the sake of keeping the investigation into the science within our grasp let’s simplify our effort and look at the most popular reactors, the Canadian designs, American designs and next generation Molten Salt Reactors6-24. The first two represent the majority of existing reactors that are now in 31 countries: France, Slovakia, Hungary, Ukraine, Belgium, Sweden, Switzerland, Slovenia, Czech Republic, Finland, Bulgaria, Armenia, South Korea, Spain, United States, Russia, Romania, United Kingdom, Canada, Germany, South Africa, Mexico, Pakistan, Argentina, Netherlands, India, Brazil, China, Iran, Japan and Taiwan and very recently the Arab Emirates. Egypt is serious about getting them while having a test reactor for years.
The Canadian Reactors are located in Ontario and New Brunswick. These commercial designs are CANDU reactors6-25. They require a much lower concentration of pure Uranium than American Light Water Reactors (LWR)6-26. Bruce Nuclear Generating Station, west of Toronto, is the biggest nuclear power plant (NPP) worldwide employing 3800 workers. It consists of 8 CANDU reactors all in the 730 MW to 813 MW range totalling over 6,000 MW. There is a thriving nuclear industry of CANDU reactors abroad in six countries: Argentina, China, India, Pakistan, Romania and South Korea.
The biggest difference between the CANDU and varieties of LWR reactors is the kind of fuel required for their operation. CANDUs do not need to enrich the fuel to high purity whereas LWRs need slightly higher purity. CANDUs use pressurized heavy water to control the reactivity rate. LWRs are a simpler design which are actually a slightly newer innovation that started around 1950 after Alvin Weinberg’s design6-27 allowing untreated water as a moderator. The uranium needs to be 3% to 5% pure U-235 for LWRs6-28 and less than 1% U-235 for CANDUs6-29. By the way, nuclear weapons require 90% pure U-2356-30.
When we discuss the actinide elements (numbered 89-103) that are naturally radioactive we are referring to the heavy elements in the periodic table where we get the fuel for nuclear power plants. Let’s look at some of the actinide properties. We discussed Marie Curie’s experiments with radium and radioactive decay that cause elements to transmute. Radium-236 is one of several radium (element 88) isotopes. It decays to radon gas. Thorium (element 90) and Uranium (element 92) are less radioactive, in fact you can hold thorium and uranium 238 without any risk of harm6-31. Our bodies can easily handle the low radiation levels much to the shock of many antinuclear folks.
Transuranic elements are also actinides but heavier than Uranium (elements 93 and higher) and more unstable than the lighter elements but they no longer exist naturally. They must be created in the lab. Over Earth’s history they all decayed or converted to other substances and gradually vanished. An unstable element is typically “radioactive.” The elements that decay faster and have a significant level of decay are more “radioactive” and their decay rate is measured by the amount of time it takes to decay by half. Thus its called the half life and the elements with short half-lives are usually the most toxic elements6-32.
More on the Physics
Uranium was thought to be getting scarce in the early years of the nuclear industry. That view has changed as the methods for extraction and reprocessing has been successfully performed. The industry has come up with some creative ways to collect fissile Uranium including breeder reactors and the dismantling of nuclear bombs6-33to use the Uranium for fuel. There are even methods proposed to extract uranium from seawater6-34. This method has inspired some people to reclassify nuclear energy as renewable because the oceans have an inexhaustible supply of dissolved uranium.
We’ve all heard of Plutonium6-35.
The word is very familiar to us. It is generally man made by using nuclear fission. Because these elements are unstable they will convert to stable or unstable isotopes meaning they will have an atomic weight more or less near the natural weight plus or minus a few neutrons. For instance U-238 is the normal atomic weight of Uranium but they have some U-235 and U-234 mixed with it. Just trace amounts can weaken Uranium’s fissile ability therefore Uranium is processed by chemical means either into its useful concentrated U-235 or into Depleted Uranium (U-238) which is not fissile but used in weapons ammunition. (note: U-238 can be used as a fertile fuel just like Thorium in Molten Salt Reactors6-36, Plutonium240 is also fertile but not fissile.) The important thing is that a fissile element is able to convert to a new element and in the process releases energy. Note: E=mc2 explains where the energy comes from in a nuclear reaction.
One of the challenges to learning about the science behind nuclear energy is the surprisingly unintuitive realities of how fission works6-37.
All nuclear reactors need fission. Typically they use U-235, Plutonium 239 or U-233 as fuel. They are all radioactive. These elements are called fissile because they can be used for fission. They can respond to neutron particles converting to daughter products. Thorium and U238 are not fissile but are called fertile since they respond well to neutron bombardment creating daughter products that are fissile. Thorium undergoes two transformations. Th232 that undergoes neutron bombardment, in the presence of fissile elements, converts to Protactinium and Protactinium decays naturally to U233. Similarly fertile U238, also in the presence of fissile elements converts to plutonium-239? The main reason to be excited about these two commonly found elements and because of the fact that they are both very mildly radioactive Th232 and U238 promise to be the fuels of the future. The Molten Salt Reactor with all of its advantages will perform well with both and once this proven 1960s technology is scaled up to commercial nuclear reactor sizes and modernized to withstand high temperatures they will catch on quickly.
To understand what is meant by energy density and why nuclear power is so important you need to take a look at the abundant energy acquired from coal plants. When a Uranium atom splits it releases 100 million times more energy than a carbon atom that combusts6-38. This explains why Einstein’s equation is such a big deal and what is meant by density and why the oil industry feels threatened. It also explains why wind and solar could never do it alone. It is clear that the support given to renewable energy by fossil fuel companies is a diversion to make themselves appear green knowing fully that renewable energy is not a threat to their dominance of the market share.
Brush up on your STEAM and when you are ready you can start making a difference.
“A single fission event can yield over 200 million times the energy of the neutron which triggered it
The word fission is derived from the Latin word findere which means to split apart. The components of an atom are made up of a nucleus and electrons. All nuclei (plural for nucleus) consist of protons and neutrons. The largest atoms, consisting of many protons, neutrons and electrons can reach a size that makes them less stable and more vulnerable to collisions with neutrons from other atoms. The best conditions for a controlled series of collisions have been discovered from experiments that have been well established for over 40 years. Pioneers like Enrico Fermi and Glenn Seabourg did much to develop the techniques needed for controlled fission. The collisions cause a split in the atom which releases heat. That heat is captured and directed to a water supply that converts to steam and creates electricity by spinning a turbine.
The nucleus of an atom is about 10-13 cm. That means if you could line up 10 trillion nuclei beside each other it would equal one centimeter. But the electron’s orbits are at quite a distance relatively speaking. The entire size of an atom would equal approximately 10-8 cm. Fissile 6-40 Uranium has the natural ability to release neutrons which are needed for fission. Uranium is inserted into a fuel assembly inside the reactor core. Fission is dependent upon the certain elements being struck by a neutron that eventually, when struck at the right angle and velocity, produces, after splitting, new atom isotopes. This splitting or breaking apart is due to the nuclear fuel, usually Uranium, being able to absorb the uncharged neutrons. Uranium fuel is set up under ideal conditions in order to maintain a continuous rate of fission called a chain reaction. There is a moderator added that stops the chain reaction from going out of control. The cycle produces more neutrons which in turn are captured by other uranium atoms. The controls in place allow fission to produce a steady source of heat that heats up water and converts it to steam.
Natural uranium comes out of the ground as a mix of 99.3% uranium 238 (U-238) and 0.7 % uranium 235 (U-235) and is mined in places like Cameco Mines6-41 in Saskatchewan and the actual uranium content in the ore is between 2% and 20%6-42. For CANDU reactors uranium does not need enrichment. It does need to go through a milling6-43 process and gets delivered to a uranium refinery. Processing takes place at one of the two known facilities in Ontario. These are designated facilities that convert either to uranium dioxide6-44, for the CANDU, or uranium hydroxide (Uranyl Hydroxide)6-45 for LWR fuel.
What happens when observing the binding forces in order of the smallest atomic weights to the largest?
There is an inverse relationship to an atoms stability to its size. The atoms actually reverse their ability to bind and these atoms are described as too large to remain stable. The ideal binding elements are, no surprise, iron and nickel. But really the study of the elements properties are the key. The elements instability are caused by their size. It’s actually the opposite relationship in gravitational forces of large bodies where we observe the larger the object the greater the attractions. Gravity is ignored at the atomic level. The size of the particles are immune individually. Collectively of course they are indeed influenced by gravity.
Warning! You can skip this section if you are not interested in the details.
Isotopes6-46 are regular atoms plus or minus a neutron or two and for the most part retains the original properties. Depending on the balance of neutrons, protons and electrons an isotope can be radioactive or non-radioactive. Isotopes of Uranium and, much less commonly, Plutonium are the most used in Nuclear Power plants. The atomic number like the 233 in U233 indicates the number of protons in an element. Every proton in an atom is matched by at least as many neutrons. The order starts at a lower atomic weight – elements 89-103 plus the heavier elements 104-118. The transuranics 93-118 are unique because of the fact that they no longer occur naturally on Earth.
Neutrons are uncharged and very useful. Here’s where the clever idea came from to manipulate6-47 the isotopes. Being uncharged they have the ability to penetrate an atom more deeply. The neutrons released by the radioactive elements U235 or Pu239 are typically too fast to be absorbed efficiently by U235 (U235 is uniquely configured to absorb slow neutrons) but if moderators such as water, heavy water or graphite are added then a chain reaction can be sustained6-48.
Theoretically, when we fission a heavy nucleus, we are really just taking energy that was stored as mass in a proverbial tiny ball under immense gravity and pressure before the Big Bang. When it exploded billions6-49 of years ago all kinds of elements were created. Stars eventually formed, aged and subsequently exploded again in super novas. These kinds of activities produced many of the heavy elements that still exist. Many of them transmuted to other elements and those with shorter half lives disappeared. Since the short range nuclear force can only hold such a big atom together for so long, all we ever find naturally that can be fissioned and that has not already decayed is Uranium.
Nobody really knows what causes that short range nuclear force but if the big bang really did happen then that bang of the universe changing from a condensed tiny area then massively exploding would retain some of its original properties. Hence the strong binding force by definition is likely related to that unique primordial moment of unmatched extreme density.
The Closest We Can Get to Alchemy – the Thorium Cycle.
When discussing alternative reactor designs it is the Molten Salt Reactor (MSR) that has been making a return from obscurity. Now it’s gained a cult status around the world. One of the MSR designs provides a means to breed fissile fuel from fertile elements such as U238 and Th232. The thorium cycle takes advantage of Glenn Seaborg’s discovery that Thorium can produce the isotope U-233. Seaborg with the help of his lab assistant observed that Thorium, when in the presence of U235 or U233, converts to Protactinium-233 and then decays after 27 days to become Uranium 233 which is not found naturally in significant concentrations.
Thorium has 90 protons and is element 90. In it’s natural state it has an equal number of protons and electrons. Since Thorium is not fissile it must offer other benefits to gain this cult status. Through neutron capture in the presence of other fissile material it will convert to Protactinium. Protactinium consequently naturally decays to Uranium-233 which is certainly capable of fissioning .
Thorium fuel has favorable properties that improve performance in a MSR. Compared to the uranium dioxide(UO2), thorium dioxide (ThO2) has a higher melting point, higher thermal conductivity, and lower coefficient of thermal expansion. ThO2 also exhibits greater chemical stability and, unlike UO2, does not further oxidize. Aqueous Molten salts melt at a higher temperature at normal atmospheric pressure unlike the high pressures that Light Water Reactors and CANDU reactors need just to keep the cooling water in a liquid state that would otherwise become steam.
Fluoride salt has some very stable qualities. Fluoride is the salt of choice for Thorium LFTR’s. For those interested in chemistry Fluoride is chemically stable but Fluorine is not.
One benefit from using the Thorium cycle is that there is an inevitable quantity of 232U that gets produced during fission. This quantity is sufficient to make it impractical to create weapons grade fuel. It essentially poisons the 233U nuclear fuel therefore it is inherently proliferation resistant. 232U cannot be chemically separated from 233U and has several decay products that emit high-energy gamma radiation making it easy to detect.
These high-energy photons are a radiological hazard that necessitate the use of remote handling of separated uranium and aid in the passive detection of such materials. 233U can be denatured by mixing it with natural or depleted uranium, requiring isotope separation before it could be used in nuclear weapons.
Chapter Six Footnotes
6-3 “Electricity market” from Wikipedia.org
Closing of Kewaunee explained
Kewaunee Power Station – Wikipedia
6-5Meredith Angwin’s Yes Vermont Yankee Blog – Jan/2011
6-6Using neutrinos to probe Earth’s hot core
6-8Encyclopedia Britannica: Marie Curie: Biography
6-9Wikipedia: List of Nobel Laureates
Superfuel by Richard Martin pg. 34 on Google Books
6-12Wikipedia Biography of Dmitri Mendeleev
A Well-Ordered Thing: Dmitrii Mendeleev and the Shadow of the Periodic Table …
By Michael D. Gordin – Google Books p. 180
6-13The discreet charm of eighteenth-century vitalism and its avatars – http://philsci-archive.pitt.edu/11546/ (see download)
6-14A Philatelic Ramble Through Chemistry
6-15Chemistry – By John S. Holman, Phil Stone – Google Books
6-16Jean Baptiste Perrin Biography
6-17Jean Baptiste Perrin (Extended Biography)
6-18“The Martian’s” RTG science includes jarring errors – Atomic Insights – Rod Adams – July 6, 2016
Curiosity Rover – Wikipedia
6-20What is the Safest Form of Energy?
6-21ThoriumMSR.com About Page (Inactive Website Created by Rick Maltese)
6-23Synthetic Elements – Wikipedia
- Terrestrial Energy’s Integrated Molten Salt Reactor
- Thorcon molten salt fission reactor
- Elysium’s Molten Chloride Fast Reactor
6-25Canadian Nuclear FAQ by Jeremy Whitlock – www.NuclearFAQ.ca
6-26Nuclear Power Reactors – www.world-nuclear.org
6-27The Second Fifty Years of Nuclear Fission by Alvin Weinberg – www.cns-snc.ca/media/history/fifty_years/weinberg.html
Uranium found in nature consists largely of two isotopes, U-235 and U-238. The production of energy in nuclear reactors is from the ‘fission’ or splitting of the U-235 atoms, a process which releases energy in the form of heat. U-235 is the main fissile isotope of uranium.
Most reactors are light water reactors (of two types – PWR and BWR) and require uranium to be enriched from 0.7% to 3-5% U-235 in their fuel. This is normal low-enriched uranium (LEU). There is some interest in taking enrichment levels to about 7%, and even close to 20% for certain special power reactor fuels, as high-assay LEU (HALEU).
Uranium-235 and U-238 are chemically identical, but differ in their physical properties, notably their mass. The nucleus of the U-235 atom contains 92 protons and 143 neutrons, giving an atomic mass of 235 units. The U-238 nucleus also has 92 protons but has 146 neutrons – three more than U-235 – and therefore has a mass of 238 units.
The difference in mass between U-235 and U-238 allows the isotopes to be separated and makes it possible to increase or “enrich” the percentage of U-235. All present and historic enrichment processes, directly or indirectly, make use of this small mass difference.
“Natural uranium contains 0.7% of the U-235 isotope. The remaining 99.3% is mostly the U-238 isotope which does not contribute directly to the fission process (though it does so indirectly by the formation of fissile isotopes of plutonium). Isotope separation is a physical process to concentrate (‘enrich’) one isotope relative to others. Some reactors, for example the Canadian-designed Candu and the British Magnox reactors, use natural uranium as their fuel.”
6-30(For comparison, uranium used for nuclear weapons would have to be enriched in plants specially designed to produce at least 90% U-235.)
6-31Thorium-232 is safe if you don’t eat or inhale it – Dr Looi Hoong Wah
6-32Half Life and Activity
6-33Megatons to Megawatts
6-34Why nuclear power can be considered renewable energy
6-35Wikipedia on Plutonium
6-36Wikipedia on Fertile Material
6-37The 10 weirdest physics facts from relativity to quantum physics
6-38Fission releases 100 million times more energy per atom than the chemical energy that’s released in a combustion reaction.
6-39Quote from hyperphysics.phy-astr.gsu.edu/hbase/NucEne/fission.html
6-40“U-235 is naturally occurring. It is possible to breed U-233 and Pu-239 from more common naturally occurring isotopes (Th-232 and U-238 respectively) by single neutron capture. The others are typically produced in smaller quantities through further neutron absorption.”
6-41Cameco Mines – Wikipedia
6-42What is Enriched Uranium – Smithsonian
Milling explained on Cameco Website
6-44Conversion explained from Cameco Website
Uranium Processing – Encyclopedia Brittanica
6-45Uranyl Hydroxide – Wikipedia
6-46BBC Bitesize Guide – “Atoms, isotopes and ions – AQA”
6-47Enrico Fermi’s discovery of Fission
6-48Fueling Our Future: An Introduction to Sustainable Energy by By Robert L. Evans – Page 116 – Google Books
6-49“The famous astronomer and astrobiologist Carl Sagan popularized the concept of a cosmic calendar about three decades ago. In his 1977 book The Dragons of Eden: Speculations on the evolution of human intelligence, Sagan wrote a timeline for the Universe, starting with the Big Bang about 15 billion years ago. Today, we think that it all started about 13.7 Billion years back.”
Sagan used the twelve months of the year to span all of time since the Big Bang. Using this scale life did not emerge until the last month.