Section 19.3

Using the Nucleus as a Source of Energy

1. To introduce fusion and fission as sources of energy

2. To learn about nuclear fission

3. To understand how a nuclear reactor works

4. To learn about nuclear fusion

5. To understand nuclear weapons

6. To see how radiation damages human tissue

Objectives

Section 19.3

Using the Nucleus as a Source of Energy

A. Nuclear Energy

• Two types of nuclear processes can produce energy – Combining 2 light nuclei to form a heavier nucleus -

fusion – Splitting a heavy nucleus into 2 nuclei with smaller

mass numbers - fission – Energy produced by conversion of mass, E = mc2

• Sun converts 4 million tonnes per second

Fusion and Fission POGIL

Section 19.3

Using the Nucleus as a Source of Energy

B. Nuclear Fission

• Each atomic fission produces 3 neutrons • Releases 2.1 1013 J/mol uranium-235 • (Burning methane produces 8.90 x 105 J/mol)

Section 19.3

Using the Nucleus as a Source of Energy

B. Nuclear Fission

• Chain reaction – self sustaining fission process caused by the production of neutrons that proceed to split other nuclei Chain Reaction Alternative CR

• Critical mass – mass of fissionable material required to produce a chain reaction

Section 19.3

Using the Nucleus as a Source of Energy

C. Nuclear Reactors

Section 19.3

Using the Nucleus as a Source of Energy

C. Nuclear Reactors

Reactor core

Nuclear Power Plants

Section 19.3

Using the Nucleus as a Source of Energy

B. Nuclear Fission

Nuclear Energy in the US?

Chernobyl 1

Chernobyl 2

Chernobyl 3

Section 19.3

Using the Nucleus as a Source of Energy

D. Nuclear Fusion

• Process of combining two light nuclei • Produces more energy per mole than fusion • Powers the stars and sun

Section 19.3

Using the Nucleus as a Source of Energy

D. Nuclear Fusion • Atoms lighter than Fe. Deuterium used• Requires extremely high temperatures ~ 1 billion K

• Currently not technically possible for use as a power source – issues with confinement

• Used as “Hydrogen bomb”• Sun’s energy captured for our use

Section 19.3

Using the Nucleus as a Source of Energy

Nuclear Binding Energy

Binding Energy

Section 19.3

Using the Nucleus as a Source of Energy

Nuclear Weapons

Fission Weapons (“Atomic Bombs”)− Enriched uranium or plutonium− Supercritical mass produced in bomb− Limited up to 500 kilotons of TNT− Twice used in warfare (Hiroshima and Nagasaki)

Section 19.3

Using the Nucleus as a Source of Energy

Nuclear Weapons

Radioactive fallout can be regulated – salted, neutron bomb

Fusion Weapons (“Thermonuclear / Hydrogen Bombs”)

− deuterium and tritium − fission bomb compresses and heats hydrogen fuel− further stages of fission reactions (depleted uranium)− largest so far is 57 megatons (“Tsar Bomba” - USSR)

Section 19.3

Using the Nucleus as a Source of Energy

Nuclear Weapons

Delivery− Gravity bombs− Missiles (land or submarine launch)− Multiple Independent Re-entry Vehicles − “Tactical” weapons: shells, torpedoes

Strategy− “Cold War, Arms Race”− “Mutually Assured Destruction”− Missile Defense− Terrorist ThreatWWII 1 2 3 4

“Now I am become Death, the destroyer of worlds”

Section 19.3

Using the Nucleus as a Source of Energy

Nuclear Weapons

Regulation− UN, International Atomic Energy Agency− Test Ban and Nuclear Non-Proliferation Treaties− SALT’s and START’s (limitation and reduction)− Still enough to destroy most human life on Earth (23,000 bombs equivalent to 150,000 Hiroshima bombs)− US, Russia, China, UK, France, India, Pakistan, North Korea, Israel (?), South Africa (X) − Obama (“World without nuclear weapons”)

Section 19.3

Using the Nucleus as a Source of Energy

E. Effects of Radiation

• Energy of the radiation • Penetrating ability of the radiation • Ionizing ability of the radiation• Cell repair, death (high dose / acute

damage), incorrect repair (low dose / cancer)

Factors Determining Biological Effects of Radiation

• Chemical properties of the radiation source− Strontium-90 and Radium-226 behave similarly to

calcium so tend to accumulate in bones. Radioactive Iodine concentrates in the thyroid

Section 19.3

Using the Nucleus as a Source of Energy

Penetrating Ability of Radiation

Alpha radiation consists of helium nuclei and is readily stopped by a sheet of paper. Beta radiation, consisting of electrons or positrons, is halted by an aluminum plate. Gamma radiation is dampened by lead

Section 19.3

Using the Nucleus as a Source of Energy

E. Effects of Radiation

Rem: the quantity of ionizing radiation whose biological effect is equal to that produced by one roentgen of x-rays. Roentgen is a defined amount of ionization of dry air

Section 19.3

Using the Nucleus as a Source of Energy

U.S.Nuclear Regulatory Commission limit of 5,000 mrem/year above background for nuclear industry workers

Section 19.3

Using the Nucleus as a Source of Energy