APES 6.6 & 6

6.6: NUCLEAR ENERGY

Nuclear fission: A neutron is fired into the nucleus of a radioactive (unstable) element, such as uranium. Then the nucleus breaks apart and releases a lot of energy (heat), then the neutrons released from the nucleus break more nuclei apart, releasing more energy (chain reaction)

Radioactivity: the energy given off by the nucleus of a Radioactive isotope (uranium-235) where Radioactive nuclei decay or breakdown and give off energy (radiation) even without fission

Radioactive half life: the amount of time it takes for 50% of a radioactive substance to decay (breakdown)

The process from Nuclear energy that heats water into steam: uranium fission

The components of a Nuclear energy machine producing electricity: control rods, water pump, cooling tower

The role of control rods: they are lowered into the reactor core to absorb neutrons and slow down the reaction, preventing meltdown (explosion)

The role of the water pump: brings in cool water to be turned into steam and also cools the reactor down from overheating

The role of the cooling tower: allows steam from the turbine to condense back into the liquid and cool down before being reused (gives of H2O vapor)

The aspect of Nuclear energy that releases greenhouse gasses: mining of uranium and plant construction

The gas released from Nuclear electricity generation: water vapor, which is technically a greenhouse gas, but is not critical since it is dependent on temperature

Drawbacks of Nuclear energy: spent fuel rods, mine tailings, water use, and thermal pollution

Spent fuel rods: used fuel rods remain active for millions of years and need to be stored in lead containers on site at Nuclear power plants

Mine tailings: leftover rock and soil from mining may have radioactive elements that can contaminate water or soil nearby

Water use in the context of Nuclear energy: Nuclear power plants require lots of water and can deplete local surface or groundwater sources

Thermal pollution in the context of Nuclear energy: hot water from power plants released back into surface waters can cause thermal shock (decreased O2 and suffocation)

The 3 significant Nuclear meltdowns: three mile island (US 1979), fukushima (Japan 2011), and chernobyl (Ukraine 1986)

Three mile island: partial meltdown due to testing error, radiation released but no deaths or residual cancer cases

Fukushima: an earthquake and tsunami triggered cooling pump failure that lead to meltdown (explosion of reactor core) and widespread radiation release

Chernobyl: stuck cooling valve during test lead to complete meltdown (explosion of reactor core), several deaths, and widespread radiation release

Environmental consequences of meltdowns: genetic mutations (contaminated soil) and cancer in surrounding people, animals, and plants due to radiation released from reactor core

6.7: BIOMASS ENERGY

Biomass: organic matter (wood/charcoal, dried animal waste, dead leaves/brush) burned to release heat, which is primarily for heating homes/cooking

Biofuels: liquid fuels (ethanol and biodiesel) created from biomass (corn, sugar cane, palm oil) and used as replacement fuel sources for gasoline, primarily in vehicles

Difference between biomass and fossil fuels in terms of carbon: biomass burning releases CO2 but does not increase atmospheric CO2 levels because it releases modern carbon. FFs release fossil carbon

Human health consequences of biomass burning: releases all respiratory irritants (CO, NOx, PM, and VOCs) leading to asthma, bronchitis, COPD, emphysema, eye irritation

Environmental consequences of biomass burning: deforestation (hab. Loss, soil erosion) and air pollutants, leading to smog formation

How the biofuel ethanol is formed: corn grain/sugar cane broken down and yeast ferments sugars

E85/Flex-fuel: 51-83% ethanol + gasoline mix; used in flex fuel vehicles, which decreases oil consumption for transport, but is less efficient than pure gasoline

Environmental consequences of ethanol production: all the negative consequences of monocropping (soil erosion, habitat loss, GHG release, H2O use) and lots of corn needed, competing with humans consumption of corn

How ethanol can be produced more sustainably: through algae, where it can be grown and fermented into ethanol, or it’s oils can be extracted to produce biofuels/biodiesel

Biodiesel: liquid fuels produced specifically from plant oils (soy, canola, palm); found to produce 98% more GHGs than Fossil fuels due to clearing of forest for farm plantations

How biodiesel can be more sustainable: if already cleared land is used or if plantations are continually replanted (however, this also has impacts from monocropping)