Nuclear Flashcards by lei lopez

splitting of an atom into two or more smaller ones

Fission

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using of two or more smaller atoms into a larger one

Fusion

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actinide element and has the highest atomic mass of any naturally occurring element

Uranium

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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

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radioactive chemical element with the symbol Pu

Plutonium

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actinide metal of silvery-gray appearance that tarnishes when exposed to air and forms a dull coating when oxidized

Plutonium

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also called urania

Yellowcake

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is a type of uranium concentrate powder obtained from leach solutions, in an intermediate step in the processing of uranium ores

Yellowcake

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discovered radioactivity in 1898

Becquerel

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fission of the atom was demonstrated by

Fermi

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generates heat which can be used to produce steam to drive prime movers, thus generating electricity

Controlled fission

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first spontaneous decaying substances

Radium and polodium

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absorbs a thermal neutron, then fissions into fragments approx

U-235

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Neutrons released by fission are at high energy levels (fast neutrons) and can react in fast reactors

True

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Naturally occurring uranium contains only ______ 235U

0.71%

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isotopes that are not fissile but are convertible to fissile materials

fertile materials

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has a long half-life (24,000 years)

239 Pu

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has a high cross section (ability to absorb) for fast neutrons and a low critical mass for fast fission

239 Pu

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Uranium is more abundant in the earth’s crust than mercury and is present in about the same amount as tin and molybdenum

true

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less widely used than uranium, is a suitable nuclear fuel

thorium

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natural isotope of thorium

232 th

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it is obtained as a by-product of the processing of monazite, a complex phosphate, for the extraction of rare earth

232 th

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Process of separating pure uranium from uranium containing impurities

refining

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Conversion of crude yellow cake or uranium metal to metal pure enough for reactor use, free of other elements

purification

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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