APES - Unit 8 - Nuclear & Renewable Energy

Radiation

the particles or energy (protons, neutrons, electrons, energy) that are released from an atom as the type/mass changes/decays

Types of Radiation

radio waves, microwaves, infrared light, visible light, ultraviolet, x-rays, gamma rays, particle radiation (alpha, beta, neutrons)

Alpha Particle

made of 2 protons and 2 neutrons, travels on 1-2 inches, shielded with paper/skin, little to no hazard

Beta Particle

made of high speed electrons and protons, travels 10ft, shielded by plastic/aluminum/clothing, moderate hazard (can penetrate skin/eye lens)

Gamma Ray

made of photons, travels 1000s of ft, shielded by lead/concrete/uranium(dense), high hazard (external and internal threat, ionization)

Neutron Particles

non natural from nuclear power plants or atomic bombs - uncharged, travels miles, shielded by water/wax/concrete, extreme hazard (internal and external)

sources of radiation

decay of radioactive elements (uranium), radon gas, sun/astronomical objects, smoke detectors - 82% natural sources

Half Life

length of time necessary for half of the atoms of that material to decay to some other material - after 7 there is less than 1% of the original radioactive material left and we can consider it basically gone

Ion

charged particle (±) - net electric charge due to the loss or gain of electrons

Ionization

Ionizing radiation - enough energy to knock electrons from their orbital paths - may interact with other atoms and cause chemical/electrostatic changes - creates positive ions which is what can actually cause harm (x-ray, gamma, alpha, beta)

Rems of Radiation

US annual whole body dose = 360 rems

0-100: possible damaged cells/cancer

100+: cells not replaced fast enough→ tissue failure→ radiation sickness

300+: immune system damage → cant fight infection/disease

400+: 50% of people die withing 60 days from infection

1000+: blood system/vascular damage (brain/nervous tissue) → 100% die

BEIR Radiation Cancer Risk

0.04-0.08% risk per rem of radiation - dependent on acute/long term exposure

More risky than average radiation exposure

2 days in NYC, 40 miles in a car, canoeing for 6 minutes, alcohol use, overweight

More dangerous jobs than nuclear

all industrial jobs, agriculture, construction, mining/quarrying, manufactoring

Nuclear Fission

the process where a heavy, unstable atomic nucleus (such as Uranium-235) splits into two or more smaller nuclei, releasing massive amounts of energy and additional neutrons. This reaction, often initiated by a neutron strike, creates a chain reaction used to generate electricity in power

Chain Reaction from Nuclear Fission

self amplifying - exponentially increasing on its own - more and more heat as time goes on - in a reactor, this process is controlled to create a steady energy release, whereas in an atomic bomb, it is uncontrolled - stopped by removing neutrons from the system (not for atomic bombs)

Uranium 235

few pellets equal amount of energy as 1800lbs of coal/150 gallons of oil - have to mine (open pit) - 0.7% usable - use centrifuge to spin and separate U-235 from U-238

Uranium Fuel

fuel pellets into rods that are put into assembles to makeup a reactor core - in pools for cooling and moderation

Uranium Spent Fuel Recycling Issue

creates plutonium that can be used for atomic bombs - countries stopped recycling in 1970s

Nuclear Power Plant Structure

• Containment building: there’s the reactor vessel, heat generator and steam generator - inside the reactor vessel there’s the reactor core with the uranium fuel assembly, control rods and 1st water current (liquid under high pressure)

• Turbine/Generator building: 2nd water current heated by the 1st into steam spinning turbine and generating electricity with magnets

• Cooling System: condenser collects steam after it spins the turbine and sends the water to the lake/cooling tower to be cooled and sent back

Reactor Core

the central part of a nuclear reactor where nuclear fission occurs, producing heat to generate electricity. It consists of fuel rods (usually uranium), control rods for regulating the chain reaction, a moderator (like water or graphite) to slow neutrons, and coolant (like water or gas) to remove heat

Control Rods

Materials such as boron, that absorb neutrons to manage or shut down the chain reaction.

water moderator

water that slows down neutrons produced by fission to sustain the reaction.

reactor vessel

A thick steel container holding the core, which also includes core support structures

Necessities of a Nuclear Power Plant

water and electricity (backup generators) to prevent over heating of the reactor core - meltdown

Reactor Types

PWR: Pressurized Water Reactor - use a two-circuit system with high pressure to prevent boiling in the core, more common/preferred for their stability and lower radiological exposure to the turbine/output side

BWR: Boiling Water Reactor - single-circuit system where water boils directly in the reactor, simpler, potentially cheaper design with higher thermal efficiency

Producers of Nuclear Power

• US

• China

• France

Countries with highest percentage of Nuclear electricity/power

• France

• Ukraine

• Slovakia

Nuclear Waste

radioactive byproduct material from nuclear power generation, undergoes beta decay (gamma rays and x-rays - ionizing for long time → remains dangerous and requires isolation for hundreds of thousands of years)

Spent Fuel

97% reusable material, 1% plutonium, 1% U-235 (considered "spent" not because all fissile material is gone), 3% highly radioactive fission byproducts (dangerous part)

Spent Fuel Pools

40ft deep pools (20ft of water above waste to shield) - made of reinforced concrete and steel - no drains - store, cool, and shield highly radioactive, newly removed fuel rods for at least 5 years

Dry Casks

After cooling in the pool, fuel is often transferred to dry cask storage — large, concrete-and-steel canisters that provide passive cooling and safer long-term on-site storage - made of protective covers that can withstand major damage, metallic seals, neutron shields, and steel all surrounding the spent fuel rods (redundancy of shields)

Nuclear Melt Down

Cooling Failure: The chain reaction becomes uncontrollable, leading to extreme heat buildup.

Fuel Rod Damage: The zirconium cladding of the fuel rods reacts with steam, producing hydrogen gas (often leading to explosions) and bursting at over 830*C

Core Melting (Meltdown): The fuel melts, forming molten corium that falls to the bottom of the reactor vessel.

Containment Breach: The molten mass can melt through the reactor vessel and the concrete containment structure.

Environmental Release: Radioactive material is released, causing severe long-term contamination.

Yucca Mountain

100 miles northwest of Las Vegas, Nevada, is a designated, yet stalled, federal repository designed for the long-term, deep-underground storage of high-level nuclear waste. Selected in 1987, the project has faced massive political, local, and environmental opposition due to concerns over seismic activity and potential groundwater contamination

characteristics of an ideal nuclear waste storage location

• remote (lack of people)

• underground (away from weather)

• desert/plains (away from animal habitats/biodiversity)

• far from plate boundaries (natural disaster zones)

• easy to transport waste too (train line)

Three Mile Island

worst US nuclear accident - 1979 PA - 0 ppl harmed - no environmental effect - ½ fuel meltdown that remained in reactor core) - very small radioactivity released - widespread panic bc of evac. - updated policies → better planning/regulations

Chernobyl

1986 USSR/Ukraine - open reactor core burning/on fire - releasing massive radiation - over 100000 ppl evac. - 31 immediate deaths (acute exposure) - 5000+ related deaths (thyroid cancer in kids) - 400x radiation than Hiroshima - engineer faults revealed during routine safety testing - different type of plant (never in US) sig. less containment - exposure to radiation across Europe through radiation rising to air currents - coal kills around the same number of people per year

Fukushima

Daiichi Plant Japan - 2011, Tōhoku magnitude 9.0 earthquake and subsequent 15-meter tsunami - flooded backup generators, causing a loss of power (station blackout) and failure of cooling systems in reactors 1, 2, and 3. This resulted in hydrogen explosions leading to partial nuclear meltdown in 3 of 4 reactor cores - large scale evac.- No immediate deaths or radiation-linked health issues have been directly attributed to the nuclear accident, though the incident caused profound social and economic disruption

Nuclear Power Pros

• much more energy efficient

• less CO2 than coal and natural gas

• uranium is relatively abundant

• zero CH4 compared to natural gas

• way fewer deaths than coal

• very cheap to run once built

• not contributing to climate change

• No mercury/sulfur/nitrogen → acid rain/smog/air pollution

Nuclear Power Cons

• nonrenewable

• risks of meltdown/radiation

• mine tailings from open pit uranium mining → habitat destruction and acid mine drainage

• limitations on where to put sites

• reputation issues

• plutonium released (atomic bombs)

• Nuclear waste storage issues

• High upfront cost

• potential contamination of water

Global Renewable Energy Use

1. Hydro 6.4% - top renewable source of electricity in the world

2. Nuclear 4%

3. Wind & Solar 3.5%

US Renewable Energy Use

renewables make up 9% of total US energy and 21% of electricity- fastest growing source - most for electricity, some for heating -

1. wind

2. hydro

3. solar (fastest growing)

US renewables for transportation

• directly: ethanol from corn

• indirectly: electric vehicles (electricity could come from nonrenewable)

Active Solar Power

• concentrating solar power (CSP plants)

• Photovoltaic PV cells (solar panels)

• Solar Water heaters

Solar Power Plants

Concentration solar power (CSP) - systems collect sunlight and concentrate it using mirrors/lens - sunlight is used to heat a liquid (water/molten salt) that them becomes steam and turns a turbine - hot liquid tanks mean energy storage over night (no solar)

• parabolic troughs/ dishes/ power towers

require a large area of land and cooling water - need backup at night or low light (batteries)

Solar Cookers

small CSP systems that could replace biomass fuels used for cooking inn developing areas (major source of indoor pollution) - would take longer but doesn’t pollute

Photovoltaic PV Cells

solar panels - convert sunlight directly into electricity - made of (abundant) silicon - sunlight excites electrons which are ejected from atoms and flow into PV cells into wire producing electricity

• free electricity after 6 years

• minimal maintenance

• scale & portability

• only 20% efficient

• low land efficiency

• more economical in remote locations

• leap frogging of developing nations

• cost competitive with fossil fuels

Solar Water Heating

about 8% of US energy goes to heating water

• collection device mounted on roof/field with tubes of water being heated by the sun in a black box (low albedo)

• heated liquid pumped into heat exchanger where surrounding water is heated and stored in hot water tank

Solar Energy Pros

• no fossil fuels

• create productivity in barren areas

• portable/versatile

• cost competitive with fossil fuels

• renewable/clean

• small payback time

Solar Energy Cons

• upfront cost

• low land efficiency

• low energy efficiency

• requires batteries/storage for night

Hydropower

as water flows from high elevation back to sea level, can harness its energy to make electricity in a water impoundment system/ hydroelectric dam

• potential energy of water held back by dam converted to kinetic energy as it flows through a penstock (spins turbine) making electricity

Global/US Hydropower Electricity

14% of worlds electricity (#1 renewable in the world) - 6% of US electricity

Top Producer Countries: 1. China - 2. Brazil - 3. US

Top Percentage of Energy: 1. Norway - 2. Iceland - 3. Switzerland

Grand Coulee Dam

largest hydroelectric dam in US - Washington State, Colombia River - 6800 MW (20 coal power plants - 2 million households)

Three Gorges Dam

Largest hydropower dam in the world - China - 1 million people evac. for 415 square miles of reservoir - 22500 MW equal to 45 coal power plants

Hydropower Pros

• renewable/clean

• more efficient than any other energy source for electricity (90%)

• inexpensive to operate

• cost competitive with fossil fuels

• reservoir provides recreation

• downstream flood control

• long lifespan

• energy storage

Hydropower Cons

• downstream destruction

• Eutrophication/dead zones - hypoxic water → (CH4 release)

• high upfront cost

• changes with precipitation

• large dams usually far from urban areas (long transmission lines)

• upstream flooding

• biodiversity loss and migratory fish harmed

Geothermal Energy

heat from within the earth - from radio active decay of elements in the center of the earth - more energy near plate boundaries as magma rises (convection) to surface → groundwater in these areas heated

1. Geothermal power plants (electricity)

2. Geothermal heat pumps (residential heat/AC)

Geothermal Power Plants

in areas where groundwater is heated - geothermal wells (1-2 miles deep) bring steam/ hot liquid to surface - steam turns turbine → electricity

• water needs to be circulated back into earth to be truly sustainable

• potential release of hazardous hydrogen sulfide (H2S) gas → scrubber to clean air

Geothermal Heat Pumps

ground source heating - heat/cool residential buildings by using the earths high thermal mass/ heat capacity→ 10ft undergrounf 55*F all year - underground pipes with circulating fluids absorb heat or transfer/cool off excess heat

• high installation costs - 7yr payback - low operating costs - very efficient - long lifespan - any location - very little emissions (NG to supplement) - reliability - small land demand

US Geothermal

world leader in geothermal energy - on west coast (california) and Hawaii - edge of plate

Wind Power

wind turbines convert the kinetic energy of moving air into electricity - made of the tower, nacelle (generator) and blades - blades spin and turn gears to increase revolutions/minute - yawing (turbine turns to face best direction using anemometer/ weathervane) - wind increases dramatically with altitude - larger turbines = more efficient → electricity cheaper - cost competitive with fossil fuels

Wind Power Locations

• turbines often grouped into large wind farms

• not ideal everywhere - want no windbreaks (buildings)

• most profitable in remote areas with continual winds or open ocean (coasts, grasslands, plains, mountain passes, offshore)

• US wind hotspots: TX, KS, ND

• Land turbine capacity: 2-5 MW

• Offshore turbine capacity: 12 MW

• each large turbine can support ± 500 homes

Global Wind Capacity

1. China (3x) - largest wind energy capacity in world

2. United States - powering 10% of electricity

3. Germany

• Denmark: generates 45% of electricity from wind (offshore wind farms)

Wind Energy Pros

• low maintenance

• creates jobs

• high efficiency

• land & offshore locations

• cost competitive with fossil fuels

• renewable/clean

• no emissions

Wind Energy Cons

• aesthetics

• intermittent (no wind - no power)

• maintenance

• difficult construction/ transportation

• require large area

• bird/bat loss

Modern vs Fossil Carbon

carbon recently in living organisms and is part of the current, fast-cycling atmosphere-biosphere system, making it generally carbon-neutral vs. carbon stored underground for millions of years in oil, gas, and coal deposits; when burned, it adds "new" carbon to the atmosphere, driving long-term climate change

Traditional Solid Biomass

wood, charcoal, animal manure - major energy source for developing countries - cheap cooking/heating fuel in rural areas

Municipal Solid Waste

MSW - trash - burned for electricity - results in pollution (plastics in trash)

Biofuels

can be made from dedicated crops, crop waste, algae, trees/grasses - most common form is corn ethanol (38% of corn grown for ethanol)

Ethanol

alcohol made by fermenting crops - used in gasoline substitutes - mostly from corn (grass, sugar cane, crop waste) - US = world leader in production (energy independence) - Brazil is #2 and makes from sugar cane

• mandate: renewable fuel standard (RFS) dictates amount of it in gas each year

Gasohol

90% gasoline - 10% ethanol - slightly lower gas mileage - Flex fuel vehicles can run on E-85 (15% ethanol) - may be easier to switch cars to biofuel than electric

Problem with corn based ethanol

• monocropping

• lots of Nitrogen fertilizers → eutrophication

• lots of pesticides → biodiversity decline

• large land & water use → carbon footprint

• farm machinery runs on fossil fuels

• takes corn away from human consumption

Biodiesel

made from oils from algae/plants - used in diesel alternative - mostly from soybeans, algae and oil palms - B-20: 80% diesel/ 20% biodiesel - diesel engines can run on straight vegetable oil with alterations

Biomass Pros

• renewable

• modern carbon

• inexpensive (corn subsidies)

• decreases ff in transportation

• decrease price of gas

• energy independence

• waste reduction

Biomass Cons

• corn monoculture problems (lots)

• carbon emissions from farming

• added to fossil fuels - no on its own

• deforestation/biodiversity loss

• low energy efficiency

• air pollution (PM, NOx, VOCs, CO2)

• competes with food production

• requires large land area

Energy Sustainability Changes for IND/Businesses

• cogeneration (power + heat production)

• more efficient motors

• more efficient computers - especially big data centers

• “smart grid” to improve electrical grid efficiency & capacity

• recycling

Energy Sustainability Changes for Consumers

• carpool / walk / bike

• turn off lights

• decrease vampire energy

• less heating/ cooling AC

• energy star appliances

• hybrid/electric cars

Energy Sustainability Changes for Buildings

• improve insulation

• double pane windows

• south facing windows

• sky lights

• use recycled materials

• overhanging roofs

• use materials with high thermal mass (retain heat)

Urban Heat island

several degrees hotter than non-urban receiving same amount of heat (sun) - more dark surfaces (low albedo) - more cars/ACs releasing heat - tall buildings slowing air movement

• high albedo roof colors or vegetation roofs - increase open areas & trees/plants