Nuclear Energy

Nuclear energy

Energy released by nuclear fission or fusion

Nuclear fission

Splitting of an atomic nucleus into two smaller fragments, accompanied by the release of a large amount of energy

Nuclear fusion

Joining of two lightweight atomic nuclei into a single, heavier nucleus, accompanied by the release of a large amount of energy

Nucleus

Comprised of protons (+) and neutrons (neutral)

Electrons (–) orbit around

nucleus

Neutral atoms

Same # of protons and electrons

Atomic mass

Sum of the protons and neutrons in an atom

Atomic number

Number of protons per atom. Each element has its own atomic number

Isotope

Atom where the number of neutrons is greater than the number of protons

Radioactive Isotope

Unstable isotope

Radioactive Decay

Emission of energetic particles or rays from unstable atomic nuclei

Example of Radioactive Isotope

Uranium (U-235) decays over time to lead (Pb-207)

Each isotope decays based on

its own half-life

Nuclear Fuel Cycle

processes involved in producing the fuel used in nuclear reactors and in disposing of radioactive (nuclear) wastes

5 steps of Nuclear Fuel Cycle

1. Neutron bombardment

2. Nucleus splits into atomic fragment

3. And free neutrons

4. Free neutrons bombard-235 nuclei

5. More free neutrons released

How Electricity is Produced

Nuclear fission → Heat → Steam → Turbine → Generator → Electricity → Cooling → Recycle

A type of nuclear fission in which non-fissionable U-238 is converted into

fissionable Pu-239

Promising for energy, but

safety concerns

Mixed Oxide Fuel

• Combination of uranium and plutonium oxides, can reprocess spent fuel from other reactors

• Common in Europe

Pros of Nuclear Energy

• Less of an immediate environmental impact compared to fossil fuels

• Carbon-free source of electricity

• May be able to generate H-fuel

Cons of Nuclear Energy

• No insurance that an accident will not happen

• Generates radioactive waste

• Many steps require fossil fuels (mining and disposal)

• Expensive

Cost of Electricity from Nuclear Energy

is very high

Electricity from Nuclear Energy

• Affordable due to government subsidies

• US: 20 %, France: 75 %, Taiwan: 8 %

Expensive to build nuclear power plants

Long cost-recovery time

Fixing technical and safety issues in existing plants

is expensive

Decommissioning old plants

is extremely expensive

Meltdown

At high temperatures the metal encasing the uranium fuel can melt, releasing radiation

Probability of meltdown

is low

Public perception

nuclear power is not safe

Sites of major accidents

• Three Mile Island (USA)

• Chernobyl (Ukraine)

• Fukushima Daiichi (Japan)

Three-Mile Island accident

1979: most serious reactor accident in US

50% meltdown of reactor core

• Containment building kept radiation from escaping

• No substantial environmental damage

• No human casualties

12 years and 1 billion dollars to repair

Elevated public apprehension of nuclear energy: Led to cancellation of many new plants in US

Chernobyl (1986) accident

• Worst accident in history

• 1 or 2 explosions destroyed the nuclear reactor => Large amounts of radiation escaped into atmosphere

• Spread across large portions of Europe

• Radiation spread was unpredictable and uneven

• 4,000 deaths attributed to plant explosion => Mostly due to cancer

• Death toll is 10,000 – 100,000

Fukushima Daiichi (2011) accident

• March 11, 2011 - caused by magnitude 9.0 earthquake and ensuing tsunami

• Disrupted power systems that pump cooling water to reactor cores and spent fuel rods

• Increased radiation in local water and food supplies => May limit seafood catches for decades

• 2^nd worst accident in history

• Earthquake & Tsunami combined with human negligence

• Poor management by TEPCO

• Several partial meltdowns

• Japan: 3^rd World rank

• 54 reactors in 17 plants

Interactions Nuclear Plants and Climate change

• Cooling requires huge quantity of water 

• Installation along large rivers and oceans

• Increase vulnerability of nuclear plants

Threatens electricity supply

• Droughts 

• Sea rise

• Jellyfish

31 countries use nuclear energy to

create electricity

These countries have access to spent fuel needed to

make nuclear weapons

Safe storage and handling of these weapons

is a concern

Low-level radioactive waste 

• Radioactive solids, liquids, or gases that give off small amounts of ionizing radiation

• Produced by power plants, research labs, hospitals and industry

• States responsible for all waste they generate

High-level radioactive waste

Radioactive solids, liquids, or gases that give off large amounts of ionizing radiation

Temporary storage solutions - In nuclear plant facility (require high security)

• Under water storage

• Above ground concrete and steel casks 

Radioactive Wastes

Low-level radioactive waste 

• Radioactive solids, liquids, or gases that give off small amounts of ionizing radiation

• Produced by power plants, research labs, hospitals and industry

• States responsible for all waste they generate

High-level radioactive waste: Radioactive solids, liquids, or gases that give off large amounts of ionizing radiation 

Temporary storage solutions - In nuclear plant facility (require high security)

• Under water storage

• Above ground concrete and steel casks  

Need approved permanent options soon.

Map of radioactive matters and wastes in France

• Old uranium mine

• Nuclear plant (electricity)

• Radioactive matter and waste storage

• 1.54 million tons of radioactive matters and wastes

Case-In-Point Yucca Mountain

• ​70,000 tons of high-level radioactive waste

• Tectonic issues have been identified

• Abandoned in 2012

Decommissioning Nuclear Power Plants

• ​Licensed to operate for 40 years: Several have received 20-year extensions

• Power plants cannot be abandoned when they are shut down

​Licensed to operate for 40 years

Several have received 20-year extensions

Power plants cannot be

abandoned when they are shut down

Three solutions of Decommissioning Nuclear Power Plants

• Storage

• Entombment

• Decommissioning (dismantling) costs billions, 10 years

Taiwan Nuclear power

• ​​Import 99 % of its energy

• 14 % of electricity comes from nuclear power

• 6 reactors

• 1 plant currently in construction

• 2 reactors in a 30 km radius from Taipei

• Nuclear Waste Storage on Orchid island

• High seismic activity

• Most dangerous nuclear plants in the world

Attitudes Towards Nuclear Power

• Generally a major case of mistrust on the part of the public towards pro-nuclear power scientists and politicians

• NIMBY - Not In My BackYard: Citizens to not want a nuclear facility or waste disposal site near their home

• Dad- Decide, Announce, Defend

• Pronuclear advocates

• Based on the science, not fears

NIMBY - Not In My BackYard

Citizens to not want a nuclear facility or waste disposal site near their home

Fuel

isotopes of hydrogen

Way of the Fusion future

• Produces no high-level waste

• Fuel is hydrogen

• Still in research phase

Problems of Fusion

• It takes very high temperatures (millions of degrees) to make atoms fuse

• Confining the plasma after it is formed

Scientists have yet to be able to

create energy from fusion