MSE Energy

exploit energy contained in nucleus

fission: neutron shot at very heavy atom, create two lighter elements and some neutrons and some energy released

neutron + U-235 => U-236 => Ba-144 + Kr 89 + Neutrons

collide two light elements to create a heavy element + release energy

deuterium + tritium => neutron + helium

fusion up to mass number of 56 (Fe), all above is fission

uranium 235 (atomic number 92, mass number 235)

comes from Torbernite (an uranium ore mineral)

natrual uranium is 99-3 % 238-U and 0.7 % 235 U, 238-U is not used commercially

nuclear fuel is produced by enriching natural Uranium by artificially increasing 235-U, if you increase more you'll get a nuke

E= mc^2

heavy nucleus + neutron => fission fragments + emitted neutrons, m*c^2 = 200MeV

1942, by E. Fermi

released neutrons themselves can trigger more fission. one neutron will cause the emission of 2 neutrons, so exponential if not controlled. The trick is to control that only one of the neutrons triggers another fission

CH has generation 2 reactors, not more

generation 1 and 2 work with water or gases as fluids, generation 3 works with liquid salt or metal as fluid

generation 4: fast neutron reactions, can burn waste from older plants (e.g. plutonium) so you will have nuclear products that have shorter radioactivity (100eds of years instead of millions); supposed to be safer, commercially ready in approx 10 years

slow neutron needed,

in nuclear reaction, fast neutrons aregenerated, so they will not induce a chain reaction. you need to slow down the neutrons gained from the first fission.

slow neutrons = thermal neutrons

slows down neutrons,

made of light atoms, because it needs to catch fast neutrons, if it were too big, then it would shatter or neutron would bounce off

used moderators: liquid water or solid graphite

modulate chain reaction by taking care of neutrons. number of neutrons must be reduced by neutron-absorbing substances (e.g. boron, cadmium, silver, hafnium or indium)

used to control fission and energy release.

you can shut down the fission by stopping the chain reaction but cooling still needed because the fuel is going to decay and this heat must be removed

control rods can be inserted between fuel rods.

submerged in heat transfer fluid/moderator (water)

core contains the nuclear fuel assembly, burn rods are placed in a specific pattern. in CH you refill the core every year with new rods, rods get re-organized and stay in there for total 5 years

uranium 233, Pu-239

high mechanical resistance, resistance to corrosion

desirable behaviour in nuclear irradiation

good thermald conductivity

dimensional stability

the fuel is in pellets which are inserted in tubes and assembled in a grid. There are also tubes that contain instruments instead of fuel pellets. Water can go between the tubes and the control rods can go inbetween

the control rods are solid bars that are made from elements that can capture adn absorb neutrons without inducing any fission. E.g. Boronm cadmium, silver, hafnium or indium.

pressurized water reactor PWR

boiling water reactor BWR

Canada Deuterium Uranium CANDU

High power channel reactor RBMK

gas cooled reactor GCR and advanced gas cooled reactors AGR

two water cirquits: primary cirquit for water circulating in a reactor (155 bar, max temp 300°C) => Pressurizer with constant pressure

secondary cirquit with Rankine cycle water loop, 55 bar, max 270°C; steam boiler, turbine coupled to generator, condenser, pump, no radioactive contamination of released water

moderator: Water

Fuel enrichment: 3.2 %

Overall efficiency: 32 %

one single cirquit: reactor vessel is directly the boiler in the Rankin cycle. Turbine + generator, condenser (closed to external cooling)

moderator: water, pressure 70 atm, 290°C max; water per se not radioactive but washes out radioactive elements

fuel enrichment 2.8 %

overall efficiency 30 %

lower pressure than other reactor

two cirquits: primary cirquit for heva water in reactor at 95 atm. secondary cirquit with light water for Rankine cycle water loop, no direct contact of water

moderator: heavy water (deuterium, very costly), temp 293°C

no enrichment needed

overall efficiency 30 %

one circuit: primary water circuit directly feeds Rankine cycle

moderator: grafite

fuel enrichment 2.4 %

water used to take out heat by flowing along fuel rods and moderator, steam goes to turbines and condensed

CO2 takes out heat from fuel rods and is then used as a boiler for high T steam; then water drives turbine

Moderator: grafite

coolant: CO2 at 650 °C

Overall efficiency 42 % because of high temperature

ressurized water reactors: light water

boiling water reactors: light water

pressurized heavy water reactor: heavy water

gas cooled reactors: CO2

light water graphite reactors RBMK: pressurized boiling water

pressurized water reactors: light water

boiling water reactors: light water

pressurized heavy water CANDA reactors: heavy water

gas cooled reactors: graphite

light water graphite reactors RBMK: graphite

pressurized water reactors: enriched uranium

boiling water reactors: enriched uranium

pressurized heavy water reactors: natural uranium

gas-cooled reactors: natural OR enriched uranium

light water graphite reactors: enriched uranium

the gas cooled reactors are by far the biggest, then the RBMK (high power channel reactors), smallers are the CANDU or the pressurized water reactors. Bigger structures that must be controlled for radioactivity, leakages, pressure, ... very costly

also compare it with the power delivered

nuclear changes where unstable isotopes emit particles and energy

decay continues until original isotope is changed in a stable isotope

natural sources: soil, rocks, contaminated air or water

alpha: particles, 2 neutrons and 2 protons, positive charge; a piece of paper

beta: particles, electrons, negatively charged; thin plates of wood or aluminum

gamma: electromagnetic irradiation; lead/iron/other thick metals

genetic damages: muatations from altered genes

genetic defects can become apparent in next generation

somatic damages to tiessues, such as burns; misscarriages; cancer

more energy and shorter wavelength than X-rays

=> deep penetration

low-level radiation (e.g. medical) with low amount of radiation => landfill

high level radiation: fuel rods from nuclear power plants => unsolved, see other card