21. Nuclear Waste Disposal
Nov. 18 TEXT: Chapter 16 pages 424-432.
Waste Management in the World
Radwaste . org
RADIOACTIVE WASTE
- By the year 2000, 8000 metric tons
High-Level Nuclear Waste
- Currently, Hanford, WA, Savannah River, GA, Idaho Falls, ID
Radioactive decay: the spontanious disintegration atoms to form other atoms and radiation
Half Life: (t½) time required for 1/2 of the radionuclides in a sample to decay
RADIOACTIVE WASTE: Materials which are radioactive and for which there is no further use
| 242Pu |
t½ = 2.44 x 105 year |
| 239Pu |
t½ = 3.79 x 105 year |
| 238U |
t½ = 4.51 x 109 year |
RADIATION UNITS
- Curie (Ci): 37,000,000,000 disintegrations per second (1 gram pure radium)
- Rad: radiation absorbed dose: 0.01 joul / kg body tissue
- Rem:
roentgen equivalent man
The dose equivalent in rems is numerically equal to the absorbed
dose in rads multiplied by modifying factors for each radiation type.
- 1/10: alpha
- 1: beta
- 1: gamma
- 500 rem dose fatal to 1/2 of population
- 100 - 200 rem: vomiting, temporary stirility, hair loss, spontaneous abortion,
cancer
- 5 rem maximum allowable sustained exposure
THREE CATEGORIES OF RADIOACTIVE WASTE
Low Level Radioactive Waste
- Clothing used by workers
- Gasses and liquid emitted by reactor
- Disposed of in metal containers on site
Intermediate Level Radioactive Waste
- Physically or Chemically produced to form Low or High-Level waste
High Level Radioactive Waste
- Spent fuel
- Neutron bombardment of daughter products produces many nuclides
- Re-processing captures fissionable material -- remainder too hot to handle
Nuclear Waste Argonne
Nuclear Energy Institute Nuclear Energy Story
DISPOSAL OF HIGH LEVEL NUCLEAR WASTE
- Currently
- In steel tanks
- Under water
- In concrete tanks
- Vitrification: annealing in borosilicate glass
- Alternatives Geological Settings for Disposal of High-Level Nuclear Waste
- Subduction zones
- Outer Space
- Ice Caps
- Deep Geological Isolation
Criteria for Deep Geological Isolation
- Storage for 10,000 years, (minimum)
- Isolation from the Water Table
- Arid Climate
- Storage Site far from Water Table
- Rock of Low Porosity and Permeability
- Future Climate Change unlikely to raise water table
- Rock Absorbent of spills and Dissipative of heat
- Storage Canisters at 160 oC
- Very Low Rate of Surface Erosion
- Low Probability of Earthquakes and Volcanoes
- Potentially Suitable Geological Substrates
- Shale
- Salt Domes
- Far from aquifer (wouldn't exist if water present)
- Few faults (plastic)
- Dissipates Heat
- Proven: operating high-level waste site in Germany
- Volcanic Tuff
- Impermeable
- Zeolite minerals absorb radioactive particles
- Crystaline Continental Shield
Yucca Mountain
Are you ready?
Answer these two short questions.
Write the answer on a piece of paper, then compare it with the "textbook" answer.
What is nuclear radiation? Answer
What are the primary considerations for burial of high-level radioactive waste? Answer