CSULA - Geology 357: Energy, Part 3

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Topic #10 - Energy, Part 3: Nuclear Energy
Geol 357: Urban Geology

I. The Energy Of Atomic Fission

A. Definitions
- 1. Proton - a positively charged subatomic particle
- 2. Neutron - a negatively charged subatomic particle
- 3. Isotope - atom that exhibits variation in its mass number
- 4. Mass number - sum of the neutrons plus the protons in an atom
- 5. Atomic number - # of protons found in the nucleus
- 6. Atomic weight - average of the atomic masses of all the element's isotopes
- 7. Fission - the act or process of splitting into parts
  - a. A nuclear reaction in which an atomic nucleus, especially a heavy nucleus such as an isotope of uranium, splits into fragments, usually two fragments of comparable mass, releasing from 100 million to several hundred million electron volts of energy.
- 8. Fusion - a nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy
B. Fuels for Nuclear Reactors
- 1. Natural fuels
  - a. U²³⁵ is the only natural isotope of any element that is spontaneously fissionable
    - 1) ₉₂U²³⁸ - 99.283% of all U
    - 2) ₉₂U²³⁵ - 0.711%
    - 3) ₉₂U²³⁴ - 0.006%
  - b. U²³⁵ is the initial fuel for all fission reactors
  - c. 1 gram of U²³⁵ equals 2.7 metric tons coal or 13.7 bbls oil
- 2. Man made fuels
C. The Nuclear Fuel Cycle
- 1. U²³⁵ must be enriched from 0.711% to 3.0%
  - a. This is done with UF₆ gas
- 2. After enrichment the U is made into UO₂ ceramic pellets
  - a. These pellets become fuel rods which last 3 years
    - 1) They are then stored in water at the reactor site
D. Types of Reactors
- 1. The Light Water Reactor LWR
  - a. This is a burner type reactor which simply consumes U²³⁵ and produces neutrons, heat, and waste
    - 1) This type reactor is ultimately limited by the U²³⁵ supply
  - b. Reactor ultimately produces steam to drive the turbine
  - c. A typical LWR has 100 tons of enriched U fuel - 40,000 rods
    - 1) Reactor is opened once a year and one third of the fuel is replaced
    - 2) 3 tons of fuel disappear each year
      - a) 150 grams Pu appears
      - b) rest is fission fragment waste
      - c) 2.2 pounds of mass is converted to energy
  - d. Control rods are neutron absorbing B or Cd
- 2. Breeder Reactors
  - a. These reactors convert U²³⁸ and Th²³² into fuel
    - 1) These reactors make more fuel than they use
  - b. France, Japan, the United Kingdom, Germany and the USSR are developing breeders
    - 1) The French have the Phoenix 250 MW and the Super Phoenix 1200 MW
  - c. The United States started research in 1948 on the LMFBR
    - 1) Billions have been spent with no results
    - 2) Clinch River project was abandoned in 1983
  - d. Low U costs will probably delay breeders in the U.S. until after 2000

II. Problems Of Uranium Mining

A. Lung Cancer among the Miners
- 1. NRC and the U.S. Public Health Service found a higher incidence of lung cancer among miners
  - a. caused by radon gas, a product of Uranium
B. Waste from Uranium Milling
- 1. 865 gallons of toxic chemical waste form per ton of ore treated
- 2. This waste was discharged into rivers or seeped into the Earth in the 1960's
  - a. Durango, CO water has 3X the maximum permitted radium
C. The Problem of Tailings
- 1. 100 million tons of radioactive sand exists at 30 mills in the western U.S.
  - a. blown by wind, leached by water, used by man
- 2. 5000 homes in Grand Junction, CO were built with this sand
  - a. occupants get equivalent of 553 chest X-ray per year
  - b. radon accumulates and causes lung cancer
- 3. Tailings have washed into Lake Powell and Lake Meade
  - a. They have twice the radon they should have

III. Problems At The Reactor Site

A. Geological Problems
- 1. Extremely extensive geological investigations are made
  - a. Reactors still end up too close to fault zones
    - 1) Diablo Canyon - PG&E
    - 2) Bodega Bay
B. Human and Mechanical Error
- 1. Three Mile Island - March 28, 1979
  - a. The feed water pump to the reactor core was accidentally closed
    - 1) rods immediately went in and the reactor partly stopped
  - b. Human error resulted in the emergency cooling system being shut off for 2 hours
    - 1) Core overheated to 1500ºC
  - c. one billion dollars damage
- 2. Chernobyl - April 26, 1986
  - a. Human errors resulted in a explosion and radiation release
  - b. 100,000 people may be contaminated

IV. The Disposal Of Nuclear Waste

A. What the Waste Products are
- 1. Fission products
  - a. Over 30 elements form
    - 1) most have half lives of <100 years
    - 2) emit beta and gamma radiation
  - b. Some are water soluble and biologically active
- 2. Transuranium products
  - a. heavier than U and form by neutron capture
  - b. have half lives >1000 years
  - c. act as heavy metal poisons
- 3. Waste must be stored for 250,000 years
B. How Much Spent Nuclear Fuel is there in the U.S.A.
- 1. Remember that there is also military and medical waste
- 2. By the year 2000 there will be 40,000 metric tons stored at 70 locations
  - a. By 2035 the total will be 85,000 metric tons
- 3. The Nuclear Waste Policy Act of 1982 selected Yucca Mountain, NV as the only depository site in the U.S.
C. Criteria for a Storage Method
- 1. isolation from the biosphere for 250,000 years
- 2. sabotage and accident free for 250,000 years
- 3. safe from natural disasters for 250,000 years
- 4. must not involve large land areas or resources
- 5. must be resistant to erosion, Earthquakes, and volcanism
- 6. handling and transport must be fail safe
- 7. economically and technically possible
D. Possible Storage Methods
- 1. Rocket transport of the waste
  - a. dangerous and costly

2. Continue present tank storage indefinitely
- a. leakage of dangerous waste has already occurred
3. Placement in deep chambers of granite
- a. waste would boil, dehydrate, melt the surrounding rock and seal itself
- b. leakage along fractures is possible
4. Injection in Deep Wells
- a. Waste would be mixed with cement or injected directly under high pressure into impermeable layers
- b. Many dangers
  - 1) high pressure injection is dangerous
  - 2) high temperature could drive the waste out into other layers
  - 3) could lubricate faults
5. Deposition in Trenches
- a. technically difficult to assure no leaks
6. Deposition under polar ice caps
- a. Waste containers melt to the bottom of the glacier and remain stationary
- b. Violates international treaties
7. Salt Mine Waste Storage
- a. salt indicates a dry environment
- b. salt flows and seals fractures
- c. salt dissipates heat
8. Element Transmutation
- a. Eventually gamma ray lasers will convert dangerous elements into safe ones

E. What is to be done?
- 1. Find a public repository for nuclear waste
  - a. Because of public fear this is probably a doomed and costly effort
- 2. Reprocess spent fuel to reduce the volume of waste
  - a. This raises more fear because Pu may be diverted to nuclear weapons
  - b. A permanent repository will still be needed
- 3. Continue on-site, dry-tank storage
  - a. This is the only reasonable political solution
  - b. This can be done for a 100 years and will allow time for:
    - 1) improved technology
    - 2) decline of public fear

I. The Energy Of Atomic Fission

II. Problems Of Uranium Mining

III. Problems At The Reactor Site

IV. The Disposal Of Nuclear Waste

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