c9 c7
Three factors that determine whether a particular nucleus will split
1) It's size 2) the numbers of protons and neutrons it contains 3) the energy of the neutrons that bombard the nucleus to initiate fission.
What is the annual dose of ionizing radiation you receive?
6200 uSv or .0062 Sn (.62 rem). If this were received all at one time you would have no immediate physiological effects.
How much energy does fission produce in 1.0 kg of U-235.
9.0 x 10¹³ J 33,000 tons of TNT 1kg of U-235, where only 0.1% mass is converted to energy here.
Nuclear reactor
A device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate.
Carbon-14
C-14 has a half-life of 5715 years and decays to nitrogen-14 through the process of beta decay. Is used to estimate when an organism died.
What are the two nuclear disasters caused by human error?
Chernobyl and 3 mile island
Decommissions a Nuclear Plant
Decommissioning (shutting down) a nuclear plant is a complex operation. All parts must be analyzed for radioactive contamination and removed according to strict criteria
Nuclear Fuel Cycle
Depleted uranium, enriched uranium, and plutonium all are components of the nuclear fuel cycle, a way of conceptualizing all the different processes that can happen when uranium ore is mined, processed, used to fuel a reactor, and the dealt with as waste
How long does nuclear waste from fuel rods last?
For lifetimes, nearly forever
How does a nuclear power plant operate?
Heat is used to boil water, converting it into high pressure steam that turns the blades of a turbine. The shaft of the spinning turbine is connected to large wire coils that rotate within a magnetic field, thus generating electric energy. This is the same as a fossil fuel power plant except the water is heated by energy released from the fission of nuclear fuel such as U-235.
What does the neutron break the U-238 into?
In U-238, the neutron goes in and breaks it up into barium and krypton and you get 3 neutrons 99.99% of the time.
How much of the electricity in the United States comes from Nuclear Power?
In the United States, 20% of commercial electrical power is produced from just over 100 nuclear reactors. All licensed by the Nuclear Regulatory Commission
Is nuclear power a case of cradle-to-cradle or cradle-to-grave?
In the case of nuclear power, cradle to grave is more appropriate because most nuclear waste is currently stored rather than becoming the "cradle" for something else.
Can ionizing radiation treat other diseases?
Ionizing radiation can treat other diseases as well. People with Graves' disease have an overactive thyroid gland that produces excess hormone which boosts their metabolism, causing many complications.
curie
Is a measure of the radioactivity of a sample, approximately equivalent to the activity of one gram of radium. 1 curie (Ci) = 3.7 x 10¹⁰ disintegrations/second = 3.7 x 10¹⁰ Bq one curie is a large amount of radiation. millicuries (mCi), microcuries (uCi), nanocuries (nCi) and picocuries (pCi) are usually used when referring to radioactivity levels.
What happens when ionizing radiation penetrates your skin?
It can set in motion a chain of events. The radiation can knock out an electron creating a free radical. Free radicals are highly reactive, it can react with another molecule to produce another free radical, the ∙OH, hydroxyl radical. This can then produce another. The hydroxyl radical continues to react with other molecules, including your DNA if it is nearby. Depending on how the DNA is damaged by the free radical, the cell that contains this DNA may die, may repair itself, or may contain a mutation. Rapidly dividing cells, are susceptible to damage by ionizing radiation including tumors so x-rays and nuclear radiation can treat certain types of caincer.
What is the problem with nuclear fusion?
It is too hard to control
What are some naturally occurring radioisotopes?
K-40 and C-14.
How is a power plant constrained?
Like any power plant, they are subject to the efficiency constraints imposed by the second law of thermodynamics. The theoretical efficiency for converting heat energy to work depends on the maximum and minimum temperatures between which the plant operates. This thermodynamic efficiency, typically 55-60%, is significantly reduced by other mechanical, thermal, and electric inefficiencies.
Who is the only person to win two unshared Nobel Prizes?
Linus Pauling, the American chemist won for his chemistry work and a noble peace prize for his objection to nuclear testing.
Where is mass most concentrated?
Mass is most concentrated in the atomic nucleus. One can view matter as a very concentrated form of energy.
Control rods
Metal rods interspersed among the fuel elements serve as the neutron "sponges". These control rods, composed primarily of an excellent neutron absorber such as cadmium or boron, can be positioned to absorb fewer or more neutrons. With the rods fully inserted, the fission reaction is not self-sustaining. As the rods are gradually withdrawn, the reactor can go critical and become self-sustaining, running at different rates depending on the exact position of the control rods. Over time, fission products that absorb neutrons build up in the fuel pellets. To compensate, the control rods can be withdrawn. Eventually, the reactor fuel bundles must be replaced.
Chain reaction
Refers to any reaction in which one of the products becomes a reactant and thus makes it possible for the reaction to become self-sustaining. The reaction of a u-235 being bombarded with a neutron is a chain reaction. Each neutron produced can strike another U-235 nucleus, cause it to split and release a few more neutrons. This rapidly branching nuclear chain reaction is self-sustaining and spreads in a fraction of a second. The first controlled nuclear fission took place at the University of Chicago in 1942.
Primary coolant
The fuel bundles and control rods are bathed in the primary coolant, a liquid that comes in direct contact with them and carries away heat. Aqueous Boric acid is a common primary coolant, H₃BO₃ The Boron atoms absorb neutrons and thus control the rate of fission and the temperature. The primary coolant serves as a moderator for the reactor, slowing the neutrons, thus making them more effective in producing fission. It absorbs the heat generated by the nuclear reaction. The pressure of the coolant solution is more than 150 times normal atmospheric pressure, it does not boil. It is heated far above its normal boiling point and circulates in a closed loop from the reaction vessel to the steam generators and back again. This closed loop forms the link between the nuclear reactor and the rest of the power plant.
secondary coolant
The heat from the primary coolant is transferred to as the secondary coolant, the water in the steam generators that do not come in contact with the reactor.
Becquerel (Bq)
The international unit of radioactivity equivalent to one disintegration (alpha, beta, or gamma) per second. This is a tiny unit so the curie is used.
What is the key to understanding fission?
The key to understanding fissions is the most famous equation in all the natural sciences E = mc² The equation is Albert Einstein's from the early 20th century.
Why don't the neutrons cancel in a nuclear equation?
The neutrons on both sides of the equation are important. The one on the left initiates the fission reaction; the ones on the right are produced by it.
Nuclear power station
The nuclear reactor is the heart of the power station. The reactor together with one or more steam generators and the primary cooling system are housed in a special steel vessel within a separate reinforced concrete dome-shaped containment building. The nonnuclear portion contains the turbines that run the electric generator. It also contains the secondary cooling system. The nonnuclear portion must be connected by some means of removing excess heat from the coolants. One or more cooling tower is located near a sizable body of water for this purpose.
Why is there a power increase over time in the Nuclear power generation in the United States?
The power increase over time stems from both improved reactor efficiencies and upgrades to reactor components.
moderator
The primary coolant serves as a moderator for the reactor, slowing the neutrons, thus making them more effective in producing fission.
Nuclear fission of U-235
The process of fission is initiated by neutrons and releases neutrons: 1) A neutron hits the nucleus of U-235. 2) The nucleus of U-235 captures the neutron, forming a heavier isotope U-236. (in the picture, U-236 is written in square brackets because it only exists momentarily) 3) U-235 immediately splits into small atoms, Ba-141 and Kr-92 with the release of three more neutrons. Each neutron produced can strike another U-235 nucleus, cause it to split and release a few more neutrons.
Do nuclear power plants give off radiation?
The radiation dose you receive from a nuclear power plant is negligible. It is less than that of your "internal dose", that is, the dose from radioisotopes that occur naturally in your own body.
Nuclear Fission
The splitting of a large nucleus into smaller ones with the release of energy. Energy is released because the the total mass of the products is slightly less than the total mass of the reactants. Matter disappears and an equivalent quantity of energy appears.
TNT
Trinitrotoluene (discovered in 1863 by Alfred Nobel) became the standard of explosive power as a result of the birth of nuclear weapons - they needed to be compared to some substance of known explosiveness. The TNT molecule is very unstable when it explodes, 2 moles of TNT rearrange to form 15 moles of hot gas (3 mol N₂, 7 mol CO, 5 mol H₂O) plus some carbon. ABout 1 g of TNT will produce about 1 L of hot gas - 1000 times increase in volume
Tritium
Tritium is hydrogen-3 or ³H, a radioactive isotope of the element hydrogen. The other two isotopes of hydrogen are not radioactive,
What is more radioactive U-238 or U-235?
U-238 is far more radioactive than U-235
What is the key difference in the nuclear properties of U-235 and U-238?
Under the conditions present in a nuclear reactor, U-238 does not undergo fission but U-235 does.
Uranium
Uranium atoms contain 92 protons. If it's electrically neutral, it will also have 92 electrons. There are two isotopes of U. 1) U-238 (99.3%) which has 146 neutrons and the 92 protons. 2) U-235 (0.7%) which has 143 neutrons and the 92 protons.
HF₆
Uranium hexafluoride, "hex", is a solid at room temperature but readily vaporizes when heated to 56 °C (135 °F). This compound is used in the gaseous diffusion process to create enriched U-238. To produce hex, uranium ore is converted to UF₄, which in turn is reacted with more fluorine gas. see picture. On average ²³⁵UF₆ travels 0.4% faster than a ²³⁸UF₆ molecule. through a long series of permeable membranes, the two elements can be separated.
How do you specify an isotope?
We specify an isotope with both its mass number and atomic number. Mass number = protons + neutrons Atomic number = number of protons
What happens when uranium emits an alpha particle?
When uranium emits an alpha particle, it becomes the element thorium.
Does Plutonium-239 pose a security problem?
Yes, Plutonium-239 poses an international security problem because the plutonium produced in nuclear power reactors could possibly be used in nuclear bombs.
Is mass lost in a nuclear reaction?
Yes, actual mass does decrease slightly. The mass of the products is less by about 0.1%, or 1/1000th. The energy of the products is less than that of the reactants. This difference corresponds to the energy released.
How much energy would be released if all the nuclei in 1.0kg (2.2 lb) of pure U-235 were to fission?
You use the equation: ΔE = Δmc² Δ means the change in, so now with a change in mass we can calculate a change in energy. Since 1/1000 of this mass is lost, the value for Δm, the change in mass, is 1/1000 of 1.0 kg, which is 1.0g or 1 x 10⁻³kg. Then substitute this value and c = 3.8 x 10⁸ m/s into Einstein's equation. ΔE = Δmc² = (1.0 x 10⁻³ kg) x (3.0 x 10⁸ m/s)² ΔE = (1.0 x 10⁻³ kg) x (9.0 x 10¹⁶ m²/s²) ΔE = (9.0 x 10¹³ kg∙m²/s²) the unit kg∙m²/s² is identical to a joule (J). the energy released from the fission of an entire kilogram of uranium-235 is 9.0 x 10¹³ J or 9.0 x 10¹⁰ kJ This is equal to the explosion of 22 metric kilotons of explosive TNT.
What is central storage area of high level nuclear waste?
Yucca Mountain, Nevada
Radioactive decay series
a characteristic pathway of radioactive decay that begins with a radioisotope and progresses through a series of steps t eventually produce a stable isotope. Radon, a radioactive gas, is produced midway in both U-238 and U-235 decay series. Whenever uranium is present, so is radon.
rem
a dose of radiation received. doses are usually than than this and are millirems (mrem)
How does a nuclear power plant differ from a nuclear weapon?
a nuclear power plant needs a slow, controlled energy release. A nuclear weapon requires one that is rapid and uncontrolled. The fission reaction is essentially the same though. Commercial power plants operate with 3-5% U-235 where weapons use fuels with 90% U-235.
Gaseous diffusion
a process in which gases with different molecular weights are forced through a series of permeable membranes. Lighter gas molecules diffuse more rapidly through the membranes than do heavier ones. U-235 and U-238 cannot be separated using chemical reactions so gaseous diffusion must be used. U-235 has lighter gas molecules than U-238 because it has 3 fewer neutrons.
Radioisotope
a radioactive isotope. The ratio of neutrons to protons in its nucleus makes it radioactive.
Depleted Uranium
aka DU, it is composed almost entirely of U-238 (~99.8%) because much of the U-235 that it once naturally contained has been removed. 1 billion metric tons of DU are stored in the United States.
sievert (Sv)
dose of radiation received, 1 sievert = 100 rem. It is a high dose doses are usually smaller than this and are microsieverts (uSv) 1 microsievert = .1 millirem.
What is the largest natural source of background radiation?
radon, a radioactive gas that is formed in the decay series of uranium. Exposure to it depends on the amount of uranium in the rocks and soil where you live and on whether your dwellings allows this radon accumulate in living spaces.
Background radiation
the level of radiation that on average is present at a particular location. It can arise from both natural and human-made sources. The largest source is radon, a radioactive gas that is formed int he decay series of uranium
Radioactivity
the spontaneous emission of radiation by certain elements. Two types, alpha and beta. Gamma rays frequently accompany the helium nucleus.
Radiation
the word radiation can mean electromagnetic radiation or nuclear radiation depending on the context
Enriched uranium
uranium that has a higher percent of U-235 than its natural abundance of about 0.7%. 90% U-235 can be called highly enriched or weapons-grade uranium. Most commercial reactors worldwide use enriched uranium as fuel.
How do you keep nuclear fission from becoming a bomb?
To control this from becoming a bomb, you slow it down with temperature change. You let it go by putting in the fuel rod and then remove it as it gets to the point that you want.
What does E = mc² mean?
E = mc² is the equivalence of energy, E, and matter, or mass, m. c is the speed of light, 3.8 x 10⁸ m/s, or c² = 9.0 x 10¹⁶ m²/s² The large value of c² means that it should be possible to obtain a tremendous amount of energy from a very small amount of matter.
Why is energy released in fission?
Energy is released because the sum of the masses of these fragments is less than the original mass The "missing" mass (about 0.1 percent of the original mass) has been converted into energy according to Einstein's E= mc² equation
What is the worldwide distribution of nuclear power plants in order or lowest to highest number of operational plants?
Africa Latin America Asia (Middle East and South) Europe (Central and Eastern) Asia (Far East) Europe (Western) Northern America
What elements are radioactive?
All isotopes and all elements with atomic number 84 (polonium) and higher are radioactive. All the isotopes of uranium, plutonium, radium, and radon are radioactive because these elements all have atomic numbers great than 83.
Radiation sickness
All rapidly dividing cells are susceptible to radiation like those in bone marrow, skin, hair follicles, stomach and intestine. The illness characterized by early symptoms of anemia, nausea, malaise, and susceptibility to infection are the result to a large dose of radiation.
Three main radioactive particles
Alpha is the worst because it is massive, it is a factor of four, 2 protons, 2 neutrons - usually helium Beta is an electron Gamma is in-between, it's just a photon of energy Alpha comes off with gammas too.
Types of Nuclear Radiation
Alpha, beta, gamma
Atomic mass unit
An atomic mass unit is 1/12 the mass of a C-12 atom, or 1.66 x 10⁻²⁷ kg. The unit is convenient for expressing the mass of individual atoms.
How does the explosion of an atomic bomb happen?
An explosive fission reaction occurs only if a critical mass of U-235, about 33 pounds, is quickly assembled all in one place.
How is a neutron a combination of a proton and an electron?
Beta emission can be thought of as breaking a neutron apart. During beta emission, the mass number (neutrons plus protons) in the nucleus remains constant because the loss of the neutron is balanced by the formation of a proton. For example, a neutron in thorium became a proton in protactinium. Because of this proton, the atomic number increases by 1.
Why is the calculating the dose of ionizing radiation more complicated?
Different types of radiation deliver different doses. Alpha particles are larger and deposit greater amount of energy in the tissue when they hit. It takes 20x more beta particles to do the same tissue damage as a given number of alpha particles. Another reason is that the same type of radiation may differ in the energy that it deposits in your tissue.
Chernobyl
During an electrical power safety test at Chernobyl Unit 4 reactor, operators interrupted the flow of cooling water to the core. The temperature of the reactor rose rapidly. In addition the operators had left an insufficient number of control rods in the reactor and other control rods couldn't be reinserted quickly enough. Furthermore, the steam pressure was too low to provide coolant, due to both operator error and faulty reactor design. The disaster was caused by rapid chemical reactions, the combustion involving hydrogen gas and the resulting fires fueled by the nuclear plant and its reactor materials. It was NOT a nuclear explosion. After the incident, cases of thyroid cancer went way up due to I-131
What is needed to induce the fission reaction?
Neutrons are needed to induce a fission reaction. In a nuclear plant, a way to generate neutrons is to use a combination of beryllium-9 and heavier element such as plutonium. The heavier element releases alpha particles, ⁴/²He. These alpha particles in turn strike the beryllium, releasing neutrons, carbon-12, and gamma rays. The neutrons produced in this way can initiate the nuclear fission of u-235 in the reactor core.
Is the concentration of fissionable U-235 in a nuclear reactor high?
No it is low, most of the neutrons given off during fission of U-235 are absorbed by U-238 nuclei in the fuel pellets and by other elements such as cadmium and boron in the control rods. Because of this, the neutron stream cannot build up sufficiently to cause a nuclear explosion.
Is a nuclear power station made of all nuclear parts?
No, a nuclear power station has parts that are both nuclear and nonnuclear.
Can you fission a kilogram of pure u-235?
No, the energy that is released blasts the fissionable fuel apart in fraction of a second, thus halting the chain reaction before all the nuclei undergo fission.
How many states have nuclear reactors?
Nuclear reactors operate at 65 sites in 31 states. The high for reactors was 112 in 1990 and that has fallen since then.
iodine-131
One of the hazardous radioisotopes released at Chernobyl, a beta emitter with an accompanying gamma ray. If ingested, it can cause thyroid cancer.
Strontium-90
One of the most harmful fissionable products released in Chernobyl. A radioactive fission product that entered the biosphere in the 1950s from atmospheric testing of nuclear weapons. Strontium ions are chemically similar to calcium ions; both elements are in Group 2A of the periodic table. Like Ca²⁺, Sr²⁺ accumulates in milk and in bones. Once ingested, it's half-life is 29 years so it poses a lifelong threat.
Like Effects of a Single Dose of Radiation
See picture.
Marie Sklodowska Curie
She won two Nobel Prizes, one in chemistry and the other in physics for her research on radioactive elements.
Are elements lighter than 83 radioactive?
Some elements are naturally radioactive like carbon-14, hydrogen-3 tritium, and potassium-40. Whether an isotope is radioactive (a radioisotope) or stable depends on the ratio of neutrons to protons in its nucleus.
What caused the Fukushima Daiichi disaster?
The 2011 Tohoku earthquake and accompanying tsunami damaged four nuclear reactors in Fukushima.
Who licensed the nuclear power used in the United States?
The Nuclear Regulatory Commission.
Critical Mass
The amount of fissionable fuel required to sustain a chain reaction. The critical mass of U-235 is about 15 kg or 33 lb. Were this mass of pure U-235 to be brought together in one place, fission would spontaneously occur. If the mass were held together, fission would continue. This is how a nuclear weapon works.
Nuclear explosion
The cahin reaction occurs in a split second.
Is coal and nuclear electricity the same?
The electricity generated by a nuclear power plant is identical to the electricity generated by a fossil fuel plant; the electricity is not radioactive, nor can it be.
Half life
The time required for the level of radioactivity to fall to one-half of its value. The half-life for each particular isotope is a constant and is independent of the physical or chemical form in which the element is found. The rate of radioactive decay is essentially unaltered by changes in temperature and pressure. Half-lives can range from milliseconds to millennia.
Why can't a nuclear power plant explode like a nuclear bomb?
The uranium fuel in a nuclear power plant is far from pure U-235 and is unable to explode like a nuclear bomb because there aren't enough neutrons around and enough fissionable nuclei for these neutrons to hit to produce an uncontrolled chain reaction characteristic of a nuclear explosion.
Nuclear fuel pellets
The uranium fuel in the reactor core is in the form of uranium dioxide (UO₂) pellets. These pellets are placed end-to-end in tubes made of an alloy of zirconium and other metals, which in turn are grouped into stainless-steel-clad bundles. Each tube contains 200 pellets.
Storage of Nuclear Waste
There is no good way to get rid of it. Canisters of spend nuclear fuel fods are submerged in water Encapsulating reporcessed HLW in glass canisters (vitrification) Dry cask storage system.
Do nuclear reactors cause pollution?
They are a natural thermal pollutant.
How do you balance a nuclear equation?
To balance a nuclear equation, you count the protons and neutrons rather than counting atoms as you would do in a chemical equation.
Beta particle
is a high speed electron emitted from the nucleus. It has a negative electric charge (1-) and only a tiny mass, about 1/2000 that of a proton or neutron.
Alpha particle
is a positively charged particle emitted from the nucleus. It consists of two protons and 2 neutrons, (the nucleus of a He atom) and has a 2+ charge since no electrons accompany the helium nucleus.
Gamma ray
is emitted from the nucleus and has no charge or mass. It is a high-energy, short wavelength photon. Gamma rays are apart of the electromagnetic spectrum and have energies similar to those of x-rays. also apart of nuclear radiation when emitted from the nucleus of a radioactive substance. From emitted from a galaxy, it's electromagnetic.
Ionizing radiation
refers collectively to X-rays and nuclear radiation that can remove electrons from the atoms and molecules they hit. Alpha particles, beta particles, and gamma rays that radioisotopes emit cause cell or tissue damage. All have enough energy to ionize the molecules they strike, they eject electrons from the bonds or non-bonded pairs in these molecules. This is true for x-rays. Cosmic rays from space are also ionizing radiation. When ionizing radiation penetrates your skin, it may set in motion a chain of events.
Electromagnetic radiation
refers to all the different types of light; radio to gamma rays
Nuclear radiation
refers to the radiation emitted by the nucleus such as alpha, beta, or gamma radiation.
rad
short for radiation absorbed dose. The rad is a measure of the energy deposited in tissue and is defined as the absorption of 0.01 joule of radiant energy per kilogram of tissue. If a 70-kg person were to aborb .70 J of energy, a dose of 1 rad would be received.
