Nuclear Flashcards
splitting of an atom into two or more smaller ones
Fission
using of two or more smaller atoms into a larger one
Fusion
actinide element and has the highest atomic mass of any naturally occurring element
Uranium
In its refined state, it is a heavy, silvery-white metal that is malleable, ductile, slightly paramagnetic, and very dense, second only to tungsten
Uranium
radioactive chemical element with the symbol Pu
Plutonium
actinide metal of silvery-gray appearance that tarnishes when exposed to air and forms a dull coating when oxidized
Plutonium
also called urania
Yellowcake
is a type of uranium concentrate powder obtained from leach solutions, in an intermediate step in the processing of uranium ores
Yellowcake
discovered radioactivity in 1898
Becquerel
fission of the atom was demonstrated by
Fermi
generates heat which can be used to produce steam to drive prime movers, thus generating electricity
Controlled fission
first spontaneous decaying substances
Radium and polodium
absorbs a thermal neutron, then fissions into fragments approx
U-235
Neutrons released by fission are at high energy levels (fast neutrons) and can react in fast reactors
True
Naturally occurring uranium contains only ______ 235U
0.71%
isotopes that are not fissile but are convertible to fissile materials
fertile materials
has a long half-life (24,000 years)
239 Pu
has a high cross section (ability to absorb) for fast neutrons and a low critical mass for fast fission
239 Pu
Uranium is more abundant in the earth’s crust than mercury and is present in about the same amount as tin and molybdenum
true
less widely used than uranium, is a suitable nuclear fuel
thorium
natural isotope of thorium
232 th
it is obtained as a by-product of the processing of monazite, a complex phosphate, for the extraction of rare earth
232 th
Process of separating pure uranium from uranium containing impurities
refining
Conversion of crude yellow cake or uranium metal to metal pure enough for reactor use, free of other elements
purification
A process by which the relative abundance of the isotopes of a given element are altered, thus producing a form of the element that has been enriched in one particular isotope and depleted in its other isotopic forms.
isotope enrichment
Two major processes used to separate 235U and 238U:
gas diffusion process
gas centrifuge process
bases on differenced in the diffusion rate between 235UF6 and 238UF6 through porous barriers several mean free paths long
gas diffusion process
depends on the centrifugal force for the separation
gas centrifuge process
advance of isotope separation process
The plasma separation process (PSP)
The atomic vapor laser isotope separation (AVLIS) process
The molecular laser isotope separation (MLIS) process
3 fissionable isotopes
233U, 235U, and 239Pu
Type of uranium mine
Open pit
Underground mine
used where deposits are close to the surface
Open pi
used for deeper deposits
Underground mine
involves a large pit where stripping out and removal of much overburden
Open pit
have relatively small surface disturbance and the quantity of material that must be removed to access the ore is considerably less
Underground mine
Natural uranium oxide from mines and processing plants is chemically converted into ______________
uranium hexafluoride (UF6)
a compound that when heated forms a gas that can be fed into enrichment plants
uranium hexafluoride
process that separates gaseous uranium hexafluoride into two streams, one being enriched to the required level known as low-enriched uranium (LEU); the other stream is progressively depleted in 235U and is called “tails,” or simply depleted uranium
enrichment
two types of enrichment technologies:
gaseous diffusion
gas centrifuge
this technology or uranium enrichment has not been utilized at the commercial level as of today
laser enrichment
involves forcing uranium hexafluoride gas under pressure through a series of porous membranes or diaphragms
Gas diffusion process
series of diffusion stages
Cascade
uses laser technology to selectively excite 235U, the fissile isotope
Laser separation
in the form of ceramic pellets
Reactor fuel
formed from pressed uranium oxide (UO2), which is sintered (baked) at a high temperature (over 2550°F)
ceramic pellet
most common reactor contains 150-200 fuel assemblies
pressurized-water reactor (PWR)
containing fissionable material in sufficient quantity and so arranged to be capable of maintaining a controlled, self-sustaining nuclear fission chain (critical) reaction
Nuclear reactor
3 major type of reactor
Burner
Breeder
Converter
commonly use uranium enriched in 235U and some type of moderator to produce heat and slow down the neutrons to maintain the chain reaction
Burner
the fuel is held in rods so that the neutrons released will fly out and cause nuclear fission in other rods
Nuclear fuel
graphite slows the neutrons down
Graphite core
these are raised and lowered to stop neutrons from travelling between fuel rods and therefore change the speed of the chain reaction
Control rod
this is heated up by the energy released from the fission reactions and is used to boil water to drive turbines in the power station
Coolant
Type of burner reactor
Pressurizer water reactor
Boiling water reactor
Liquid-metal coolant reactor
“Breeders are designed to produce more fuel than they consume.”
True
run without moderators
Breeder
The liquid-metal fast-breeder reactor (LMFBR) keeps neutron energy high by using solid sodium as a coolant
False (liquid)
use 238U as a fertile material to produce 239Pu and are usually not designed to produce useful heat
Converter
Cores are smaller and have a longer life than power-producing units
Converter
designed to produce enormous amounts of energy in a very brief time
Atom bomb
Main steps in processing nuclear waste
Pre-treatment
Treatment processes
Conditioning
prepares the waste for processing and includes sorting and segregation to separate out contaminated items from non-contaminated ones
Pre-treatment
reduce the volume of waste requiring treatment
Decontamination technique
tend to reduce the volume or radioactive waste by separating out the radioactive component from the bulk waste
Treatment processes
2 common treatment techniques
Incineration of solid waste
Evaporation of liquid waste
brings the waste into a safe, stable and manageable form
Conditioning
designed to slow the release of radionuclides from the disposed waste package into the environment
Conditioning techniques
residues from the defense production cycle
Defense water
It is also made by distillation of liquid hydrogen
Tritium
experimental tools of excep tional diversity and application
Trace element
