Exam 4
What defines a nuclear reaction?
One element is converted into another element, and mass is lost
Which is not a benefit associated with nuclear power plants?
inexpensive to operate
How much energy comes from a fission reaction? Where does the lost mass come from?
*1 kg undergoes fission - but, only 0.1% (0.001 kg) is transformed into energy according to Einstein's equation, and the missing matter is converted into energy
The half-life of carbon-14 is 5,730 years. If you started with 100.0g of carbon-14, how much will remain after 3 half-lives?
12.5 g
Approximately what percentage of the electrical energy generated in the United States is produced from nuclear energy? -20 % -50 % -10 % -5 %
20%
How much of the US's power comes from nuclear power?
20%
How much of the initial amount of remains after 2 half lives?
25%
What percentage of Pu-131 remains after 34 minutes (t(1/2)=8.5 minutes)?
6.25%
What is a chain reaction? Why does it occur? What is critical mass? What happens above critical mass? What happens below critical mass?
A chain reaction refers to a process in which neutrons released in fission produce an additional fission in at least one further nucleus. This nucleus in turn produces neutrons, and the process repeats. Critical mass is the minimum amount of fissile material needed to maintain a nuclear chain reaction. How it works: Small explosions of TNT bring subcritical masses of fissionable material together, initiates a chain reaction, which brings about the explosion The neutrons produced in fission can then bombard another U atom and create another nuclear reaction. Nuclear reactors use controlled fission to produce energy. Critical mass: amount of fuel required to sustain a chain reaction. For U-235 it is ~15 kg
What is fission? What results from nuclear fission?
A fission reaction is the splitting of a large nuclei into two smaller stable nuclei, the result of a fission reaction is two smaller stable nuclei and a small amount of mass lost
What is a breeder reactor?
A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate. A fast-breeder nuclear reactor produces more fuel than it consumes, while generating energy. Conventional reactors use uranium as fuel and produce some plutonium. Breeders produce much more plutonium, which can be separated and reused as fuel.
What is an ion?
An atom/molecule that has lost one or more electrons, an atom/molecule that has gained one or more electrons
How can an uncontrolled reaction be used? How is a controlled reaction used?
An atomic bomb is an uncontrolled fission chain reaction that has small explosions of TNT bring subcritical masses of fissionable material together, this then initiates a chain reaction, which brings about an explosion. A controlled reaction is used to make electricity in power plants because the the nucleus splits and and releases a neutron which produces a lot of energy, so power plants capture that energy and convert it into electricity. \
What are the benefits of nuclear power? What are the risks?
Benefits: Nuclear power generation does emit relatively low amounts of carbon dioxide (CO2). The emissions of green house gases and therefore the contribution of nuclear power plants to global warming is therefore relatively little. This technology is readily available, it does not have to be developed first. It is possible to generate a high amount of electrical energy in one single plant. Risks: Radioactive waste is still an unsolved one, high risks: despite a generally high security standard, accidents can still happen.referred targets for terrorist attacks, uranium is a scarce resource, its supply is estimated to last only for the next 30 to 60 years depending on the actual demand, and it is an illusion to build new nuclear power plants in a short time.
Can you name two other nuclear disasters? What were/are the effects?
Chernobyl and The Fukushima Accident. The effects are extreme long lasting radiation existence in the atmosphere, and harming the health and living of humans.
What is Einstein's famous energy equation? How does that relate nuclear power?
E = mc^2, proves that that an increased relativistic mass of a body comes from the energy of motion of the body- that is kinetic energy
True or False: Heating a radioisotope will speed its decay and therefore shorten it's half-life.
False...why?
How are nuclear fission and nuclear decay the same? How are they different?
Fission: • Radioactive nucleus is hit with a neutron and splits apart • Large amounts of energy are produced (E = mc2) • Only certain radioactive isotopes undergo fission • Critical mass is required for chain reaction • Process is instantaneous Nuclear Decay: • Spontaneous event • Energy is released • All nuclei, N = 84 and higher, undergo decay to become more stable • Decay time measured by half life
Which country gets the largest percentage of its power from nuclear plants? -Japan -Germany -United States -France
France
Which naturally occurring type of radiation has the greatest penetrating power?
Gamma
Which type of decay does not produce a different element?
Gamma
What is a half-life? How can we calculate % remaining, % decayed, mass remaining and half-life? How do we compare half-lives?
Half-life: the time required for the level of radioactivity to fall to one-half of its initial value. Multiply the initial concentration by 1/2 to the power corresponding to the number of half-lives to obtain the remaining concentrations after those half-lives. Subtract the remaining concentration from the initial concentration. Then divide by the initial concentration, multiplying the fraction by 100 to obtain the percent completion. We can use half-lives to predict how much time is needed for the reaction to reach a certain percent completion. • Half life depends on isotope • Does NOT depend on initial amount
How does I-131 treatment work?
I-131 destroys both healthy and over-reactive tissue
Explain Three Mile Island.
In 1979 at Three Mile Island nuclear power plant in USA a cooling malfunction caused part of the core to melt in the #2 reactor. The TMI-2 reactor was destroyed. Some radioactive gas was released a couple of days after the accident, but not enough to cause any dose above background levels to local residents. There were no injuries or adverse health effects from the Three Mile Island accident.
What happened at Chernobyl? Where was it located? What was the cause of the incident? What happened afterwards? How many people were affected? What is the aftermath?
In 1986, the Chernobyl Accident showed the world the potential dangers of nuclear reactions. The tragedy took place in a nuclear power plant in Chernobyl, Ukraine. Power plant workers were testing new routine shutdowns when the amount of hot fuel, cool air, and forceful pressure caused massive steam explosions. These explosions led more than thirty people to their deaths. The explosion itself was not the main source of fatalities. The radiation from the explosions made the land extremely toxic which led to the many deaths weeks after the incident.
Where do we encounter radiation in our daily lives? Which sources are the most intense? Which sources are the most surprising?
In the soil and from the sun and food and water, More radioactivity released from burning coal than from nuclear power plants! Smoking is surprising. Overall, dosages are so small they have no effects
How does an atomic bomb work? How was it developed and used?
Is an uncontrolled fission chain reaction. How it works: Small explosions of TNT bring subcritical masses of fissionable material together • Initiates a chain reaction, which brings about the explosion • August 1939: Einstein endorsed a letter addressed to President Roosevelt, advising him to fund research for use of fission as a weapon (since Nazi Germany was also conducting this research). This led to the Manhattan Project (scientific effort to build a bomb, Oppenheimer). August 1945: U.S. detonated two bombs over Japan
Depleted Uranium is...?
Is mostly, but not all U-238
Are Ba and Kr the only possible combination of products in the radioactive decay in Uranium?
No
How do nuclear power plants work? How do coal fired power plants work? What features do they share? How are they different? How to they compare with other forms of power generation? What do fuel rods do? What do control rods do? What waste is produced in each? Where is carbon dioxide produced in the different types of power plants? Why might one be preferable to the other?
Nuclear Power Plants: Control rods, inserted or withdrawn to varying degrees, slow or accelerate the reaction. Water separates fuel tubes in the reactor. The heat produced by fission turns this water into steam. The steam drives a turbine, which spins a generator to create electricity. Col-fired Power Plants: water is turned into steam, which in turn drives turbine generators to produce electricity. The combustion reactions that power a fossil fuel plant consume fuel and oxygen and produce water vapor, carbon dioxide and energy. The combustion of coal, natural gas and oil always yields CO2, a gas believed to be strongly connected to global warming. Because coal and oil have noncombustible impurities, these sources also produce nitrous oxides, sulfur dioxide and other pollutants. A nuclear power plant does not use chemical reactions to produce energy; during normal operations, it has no gaseous emissions.
To what does nuclear refer? How are nuclear reactions used?
Nuclear power is the use of nuclear reactions that release nuclear energy to generate heat, which most frequently is then used in steam turbines to produce electricity in a nuclear power plant. The term includes nuclear fission, nuclear decay and nuclear fusion. Nuclear reactions are used to produce electricity.
What is the difference between chemical and nuclear reactions? What remains constant in a chemical reaction? What remains constant between product and reactants of chemical reactions? What remains constant between products and reactants of nuclear reactions?
Nuclear reactions cause elements to change form, while chemical reactions just rearrange electrons in the nucleus. The mass remains constant in a chemical reaction between the reactants and the products. In nuclear reactions the number of elements remains the same*.
What is nuclear waste? Why does it remain radioactive? What is the difference between low level and high level waste? How is nuclear waste stored?
Nuclear waste is the material that nuclear fuel becomes after it is used in a reactor. It remains radioactive because of High-level radioactive waste (HLW): requires permanent isolation from biosphere • Spent nuclear fuel (SNF): 3% of waste; 95% of the radioactivity! • Each plant produces 27 tons per year • Threat to national security, why? • Low-level radioactive waste (LLW): waste with less radioactive materials (less hazardous) Excludes spent fuel Contaminated materials, tools, etc. Requires continual maintenance in deep water storage pools (water cools fuel and absorbs alpha/beta radiation.) or in dry cask storage (spent fuel stored in leak-tight steel cylinders.)
What are the components of the atom? What is the mass number? What is the atomic number? How do they relate to the atomic symbol? What is an isotope?
Protons, neutrons, and electrons. The mass number is the amount of protons and neutrons in a nucleus. The atomic number is the number of protons in the nucleus of an atom- determines position of the element on the periodic table. The atomic symbol is the number of positive charges or protons of an element. An isotope is when an element has the same number of protons as another element, making it the same type of element, but one elements has a different mass number because the number of neutrons in the nucleus is slightly different.
A breeder reactor produces which type of fuel?
Pu-239
What is radioactivity? What are the three types of nuclear radiation? What are the properties of the three types of nuclear radiation? What type of nuclear decay alters the elements present? Can you classify the type of decay? Can you predict missing components?
Radioactivity is the spontaneous disintegration/decay of an unstable nucleus; emits radiation. The three types of nuclear radiation are alpha decay, beta decay, and gamma decay. The type of nuclear decay that alters elements present are alpha and beta decay. Yes we can classify the type of decay by the missing component. We can predict the missing components by algebraic methods.
How does I-131 affect humans? How can it be used medically?
Radioiodine therapy is a nuclear medicine treatment for an overactive thyroid, a condition called hyperthyroidism, and also may be used to treat thyroid cancer. When a small dose of radioactive iodine I-131 (an isotope of iodine that emits radiation) is swallowed, it is absorbed into the bloodstream and concentrated by the thyroid gland, where it begins destroying the gland's cells.
What does nuclear radiation do when interacting with the human body? What is an ion?What is a free radical?
Radioisotopes act like other stable isotopes of the element. Potassium is found throughout the body (nerves) Carbon is found throughout the body (everything) An ion is an atom or molecule with a net electric charge due to the loss or gain of one or more electrons • Ionizing radiation can be used to treat diseases. • Rapidly dividing cells can be damaged/destroyed by ionizing radiation (healthy cells are damaged too) A free radical is an uncharged molecule (typically highly reactive and short-lived) having an unpaired valence electron.
Which is a common characteristic of both nuclear and conventional electric power plants?
Steam turbines
How much of the power consumed in the US comes from nuclear power? How many plants/reactors are in the US? How does that compare worldwide?
The Us consumes 20% of nuclear power each year. 100 nuclear reactors at 61 sites in 30 states, compared to the rest of the world the US uses a small amount of nuclear by 50%, for example France uses 76%
Suppose an earthquake occurred near a nuclear power plant. How should the reactor and core (fuel and control rods) be programmed?
The control rods should be fully inserted to slow the fission process
Which is a known risk associated with nuclear power plants? -The workers will have higher risks for cancer than the standard population. -The water used to cool the system will become radioactive. - The cooling water source can suffer thermal pollution. -The electricity produced will be radioactive.
The cooling water source can suffer thermal pollution.
How do the nuclear power plants and coal fired power plants compare to each other with respect to radiation exposure and with other exposures of our everyday life?
They both use heat to generate steam and drive turbines to produce electricity. They mainly differ in where their heat comes from; a nuclear reactor uses radioactive decay, and a fossil-fuel plant burns coal, oil or natural gas. In addition to the technical differences between the two approaches, they affect the environment differently: Fossil-fuel plants are notorious for greenhouse gas emissions, whereas nuclear reactors are known for radioactive waste. Nuclear power plants emit radiation which is bad because it causes cancer and burns our bodies while emitting radioactive waste into the atmosphere. Coal and other fossil fuels kill the ozone because they emit pollutants that kill the ozone.
Why is uranium enriched? What happens when it is enriched?
This process is extremely difficult • Need 5% U-235 for power • Need 85% U-235 for weapons • Depleted uranium (U-238) can be converted into Plutonium Enriched uranium is a type of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. When uranium is enriched it can be used to fuel nuclear power plants.
Do all nuclei undergo fission? Which isotope of Uranium will undergo fission? Which isotope of Uranium is most abundant? How are fission reactions initiated?
U-235
Is the nuclear power generation associated with producing greenhouse gases?
Yes, but from obtaining the fuel.
What are some of the BENEFITS of nuclear power? Select all that apply. -A large amount of energy is produced for a small amount of starting material. -HLW and LLW can easily be stored on reactor sites. -Minimal criteria air pollutants are released. -Less CO2 is released to the atmosphere than coal-burning power plants.
all apply
Although the nuclear reactors used to produce electricity do not release carbon dioxide, nuclear energy is still responsible for the release of this greenhouse gas. Which activity probably DOES NOT contribute largely to the carbon dioxide released by nuclear power generation. -cooling of the secondary coolant by a large reservoir of water -mining and production of uranium fuel rods -construction of the nuclear reactor facility -transportation of nuclear fuel and waste
cooling of the secondary coolant by a large reservoir of water
Radiation exposure -cannot come from drinking water -is not harmful -is cumulative over a lifetime -is not cumulative over a lifetime
is cumulative over a lifetime
Which of these is not a realistic risk associated with nuclear power plants? -thermal pollution of nearby body of water -a nuclear explosion. -release of radioactivity from spent fuel rods -a meltdown from loss of coolant.
likelihood of a nuclear explosion
Thermal pollution is possible at water sources near -both coal-burning and nuclear power plants -nuclear power plants -neither coal-burning nor nuclear power plants -coal-burning power plants
nuclear power plants
How is radiation measured? What are the units?
rad = "radiation absorbed dose" - absorption of 0.01 J of radiant energy/kg tissue rem = "roentgen equivalent man" = Q x (number of rads) where Q is a relative biological effectiveness factor 1 Sievert = 100 rem 1mSv = 1 x 10-3 Sv 1 µSv = 1 x 10-6 Sv
Most high-level nuclear waste in the United States is currently -encased in glass and buried near the surface -stored at breeder reactors waiting for reprocessing -sealed at the sites where it was produced -sealed deep within the Earth.
sealed in deep pools at the sites where it was produced
Which factor will support the growth of nuclear energy in the future? -smaller, more efficient reactor design -tax incentives for the oil and gas industry -high cost of new, safer technology -a ban on the use and development of breeder reactors
smaller, more efficient reactor design
Fission is the process of creating energy by...
splitting a larger nuclei into two smaller more stable nuclei
