APES UNIT 6

Radioactive Half-Life

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

Control rods

are lowered into reactor core to absorb neutrons and slow down the reaction, preventing meltdown (explosion)

Water pump

brings in cool water to be turned into steam and also cools reactor down from overheating

Cooling tower

allows steam from turbine to condense back into liquid and cool down before being reused (this gives off H₂O vapor)

Nuclear energy is _____ because radioactive elements like Uranium are limited

NONRENEWABLE

Spent Fuel Rods

used fuel rods remain radioactive for millions of years & need to be stored in lead containers on site @ Nuclear PPs

Mine tailings

leftover rock & soil from mining may have radioactive elements that can contaminate water or soil nearby

Water use

Thermal Pollution

 hot water from PP released back into surface waters can cause thermal shock (decreased O₂ & suffocation)

Three Mile Island (US)

partial meltdown due to testing error; radiation released but no deaths or residual cancer cases

Biomass

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

Biofuels

liquid fuels (ethanol, biodiesel) created from biomass (corn, sugar cane, palm oil)

Biomass characteristics

• Utilized primarily in developing world for heating homes & cooking food

• Easy to harvest, available, cheap/free (subsistence fuel)

• Can also be burned in PPs to generate electricity (less common than FFs)

What are biofuels used for?

Used as replacement fuel sources for gasoline, primarily in vehicles

What does burning biomass do?

Burning biomass releases modern carbon (CO₂ that was recently sequestered, or taken out of the atmosphere) whereas FF burning releases fossil carbon that had been stored for millions of years

What does biomass burning release?

Biomass burning releases CO₂, but doesn’t increase atmospheric CO₂ levels like FF burning does

Biomass burning releases CO, NO_x, PM, and VOCs - all respiratory irritant

• Biomass burn. indoors for heat/cooking worsens effects (pollutants trapped & conc.)

  • Worsened asthma, bronchitis, COPD, emphysema, eye irritation 

What are the consequences of biomass?

• Lack of environmental protection laws & financial resources for other fuels lead to more biomass deforestation in developing nations

• Hab. loss, soil erosion, loss of CO₂ sequestration, air & H₂O filtration

Corn & sugar cane are fermented into ethanol which is mixed w/ gasoline

• Corn grain/sugar cane broken down & yeast ferment sugars → ethanol

Liquid fuels produced specifically from plant oils (soy, canola, palm)

• Palm oil biodiesel has been found to produce 98% MORE GHGs than FFs, due to clearing of forest for palm plantations

Passive solar

absorbing or blocking heat from the sun, w/out use of mechanical/electrical equip.

Active solar

use of mechanical/electrical equip. to capture sun’s heat (solar water heaters or CST - concentrated solar thermal), or convert light rays directly into electricity (PV cells)

what do solar water heaters do?

Solar water heaters capture sun’s heat in water or circulating fluid & transfer heat to warm water for home -  in place of electric/gas water heater

Photovoltaic Cells (PV)

Aka “solar panels”; contain semiconductor (usually silicon) that emits low voltage electrical current when exposed to sun

Renewable Energy Sources

Can be replenished naturally, at or near rate of consumption & reused.

Nonrenewable Energy Sources

Exist in fixed amounts on earth & can’t easily be replaced or regenerated

Fossil fuels will run out because___

they take far longer to regenerate than the rate we use them

Developed nations use more _____ on a per capita basis, but developed nations use more _____ in total (higher pop.)

energy