Radioactive materials and radiation pgs. Ch 4 80-85
Radon: what it is and your home pgs. Ch 17 476-480
Fission reactors and Nuclear Waste pgs. Ch 15 443-450
Continued and Related Issues
Geological and Natural Processes and Connections
Continuation and Augmentation
Outline
Nuclear Processes
General Radioactive Decay
Fission - used today and developed this century.
Fusion - experimented with today and used in the future?
Natural radioactive decay
Natural products and origins
Two Focus Case Studies of related environmental problems chosen for this example
Radon
Natural Fission of Uranium
Geology and Radon's origin
How we have only recently made it significant in our lives.
1984 - the wake-up call
Nuclear Waste
How we use Geology as the primary environmental barrier to isolation of nuclear waste
WIPP (Waste Isolation Pilot Plant - Carlsbad NM)
What it is
How it works
How it was built
What geology it depends on
Personal experience
Nuclear change is the third type of change
1. physical,
2. chemical,
3. nuclear
Three types of nuclear events:
1. Natural radioactive decay
2. Nuclear fission
3. Nuclear fusion
In nuclear reactions, the total matter + energy is conserved.
Some nuclear matter is converted into energy and this is what we use as we react nuclear fuel.
Uranium
Example of an environmental complex situation caused by radioactive decay
Radon (Rn) is one of the natural decay products of Uranium and Rn 222 has a half-life of 3.4 days (Rn 240, 54.5 sec. half-life)
Radon
(alpha -particle)
Isotopes of hydrogen and uranium
Various particles emitted in radioactive processes
Three (common or primary) particles or energies emitted in nuclear reactions
electromagnetic radiation
very short l, high energy
Helium nucleus (2 protons, 2 neutrons)
conversion of neutron to proton in nucleus
Other particles or energies emitted in nuclear reactions
positive electron from the nucleus with p to n result -1 atomic #, same atomic weight
Table of examples of each type of decay. Figure (4-1) energy of radiation or particle
Examples:
How do you get an electron from the nucleus when there are no electrons in the nucleus (Beta particle)?
Note: Nuclear events transform sub-atomic particles and elements but the sum of the matter and energy remains constant.
Neutron is converted to a proton within the nucleus and an electron is emitted.
Positron is analogous to a positive electron.
A positron emission can be viewed as a result of a conversion of a proton to a neutron in the nucleus.
Penetration power and ionizing radiation
What is the energy of gamma ray frequency?
Compared to 200-500 J/mol for a covalent bond what kind of energy is this?
Is this ionizing radiation?
Like what other radiation?
What do all ionizing radiation's have in common?
Reference: Recall the bond energy of some molecules.
| Molecule | Bond | Bond Energy in kJ/mol |
| Methane | H-CH3 | 438.4 ± 1 |
| CH3-C6H5 | 317.1 ± 6.3 | |
| CH3-CH2CCH3 | 308.4 ± 6.3 | |
| Ethyl alcohol | H-OC2H5 | 436.0 ± 4.2 |
| F-CF2Cl | 490.0 ± 25 |
U-238, U-235, Th-232, C-14, K-40 others . . .
Uranium is highly concentrated in Seawater
U-238, 99.275% abundance with a 4.51 x 109 y half life (alpha and gamma decay)
U-235, 0.7% abundance with a 7.0 x 108 y half life (alpha and gamma decay)
Examples: Seawater
Thorium there is no stable isotopic form
Th-232 100% abundance with a 1.41 x1010 y half life (alpha and gamma decay)
Example: Thorium is used in lantern mantels
Biologically active K-40, C-14, Others
K-40 0.0117% abundance with a 1.28 x 109 y half life
(beta and gamma decay)
If you are alive you have some in you
Example:
Essential for nerves in all mammals
Carbon -12 98.9% abundant stable
Carbon -13 1.1% abundant stable
Carbon -14 trace% 5730 year half life (Beta decay)
If you are alive you have some in you
Example:
This is how you can carbon date a mummy
Map of the Chesapeake Bay showing dissolved concentration of uranium in ng/mL
A chain reaction of large mass isotopes such as U-235 requires:
High purity of U-235
Critical mass
Example of Uranium fission:
Uranium
How much energy?
2 x 1013 J / mol
(20,000,000,000,000 J/mol; or 20 trillion)
Figure 3-11, 3-12, 3-13 demonstrate fission of U-235
Nuclear fission chain reaction
Fusion: "Sun power"
Scientific copy is:
(Unfortunately, we need a couple million degrees just to get it going)
Fusion is more efficient than Fission
Radon (read pg. 573-74, Miller)
Attention to the presence of Radon gas in US homes was brought sharply to the front page news in 1984 - An engineer at the Limerock Nuclear power Plant in Pennsylvania repeatedly triggered the plant's radioactivity detectors. The source of the radiation was his home (Mr. Watrus). At the time EPAês budget for evaluating radon was $0.
Watrus Home in 1984 --> 2.7 x 103 pCi/L (equated to 455,000 chest x-rays/yr.)
EPA action level 4 pCi/L
Out door reference level approximately 0.2 pCi/L
Why?
Uranium ore - to - Radium - 226 to Radon - 219, 220, 222 U - 238
Radon - 219, 220 1/2 life ~ seconds
Radon - 222, 3.8 days 1/2 life
Radon - 222 to Polonium - 218 and Polonium - 214
alpha- emitters 1/2 life 3.1 min. 2 x 10-4 s
Associated with deposits of Uranium
Granite
Phosphate Rock
Water that flows through granite or uranium deposits
Collecting in low cavities in the earth, caves, mines, basements
Radon is continuously renewed by the constant decay of Uranium.
Why does it enter your basement?
Why does it not react with something in the ground first?
What is radon?
Data you may need to make reach a conclusion:
Atomic wt of Radon is 222 g/mole
Wt. of air is approximately 14.4 g/mole
Problem:
Radon - inert Po is a reactive positive ion and clings to lungs (bronchial tissue)
alpha- penetration approx. 70µm, approx 2x the cell membrane thickness of lung tissue thus access to DNA is the proposed cause of lung cancer.
Enough energy to break both sides of a DNA chain simultaneously.
Why is this a problem?
Specific location of carcinoma in lung, yes (bronchial tissue)
5,000 to 20,000 deaths per year attributed to Radon.
Detection - Yes
Epidemiology - Yes (dose response of Uranium miners)
Engineered barriers - Yes (Radon pumps and sealing cracks)
Sources of indoor radon-222 gases
Energy Consumption
84% of commercial energy used in the US is wasted.
41% is wasted due to the second law of thermodynamics and inefficient transfer mechanisms. (resistance losses, waste heat loss, etc.)
43% is wasted unscientifically and could be recovered.
Examples: Figure (29) energy losses.
What is the number one (#1) anthropogenic source of air borne radiation?
Science is simply common sense at its best – that is, rigidly accurate in observation, and merciless to fallacy in logic.
– Thomas Huxley
Nuclear Waste Storage
Kinds of Nuclear Waste
1. High Level - fuel rods, bomb fuel
2. Transuranic "TRU" -
Nuclear Waste Isolation
Dangerous for 10,000 years
Isolate from human contact - How?
Geology and Time
High level waste not finalized yet.
TRU waste - WIPP facility in NM
Geology is the key
How is the facility constructed? In a salt geological layer 2190 ft. below the surface of the earth
A picture is worth a thousand words.
WIPP site for disposal of TRU waste
What is it?
What is doing the protecting?
How long must it be there?
What guarantees the safety?
What is the most likely scenario of it getting out?
Why has it taken 25 years to get this far?
Some examples:
Some data:
a. Unique geological site in a salt dome over 1500 feet thick
b. Relatively stable geological formation
c. 500 feet above sea level
d. Location over 2,190 feet down
e. Relatively dry and impervious to water
f. Relatively little valuable geology for future interest
g. Dry climate
h. No local rivers or water sources
Pictorial examples and diagrams of the site provide an appreciation for the scale and complexity this task.
Examples
Most likely scenario of WIPP release:
Human intervention:
1. Drilling or mining in the distant future
2. Accidental damage to transport vehicle
3. Terrorist or sabotage to transport or site
Observations
Suggestions
"Science is built up with facts, as a house is with stones. But a collection of facts is no more a science than a heap of stones is a house".
Jules Henri Poincare'
Matching energy use to quality of energy
Example:
Space heating requires the lowest quality of energy
Use of high quality energy to perform this task is wasteful
Figures (30), (31), (32) energy efficiency
"We cannot recycle waste heat, we can only conserve energy"
Discussion of energy use in the US
Figures (32-35)
Waste heat
Conservation of energy
Efficiency of devices
Why is solar heating (passive) so efficient?
Where does the energy come from?
In what form of energy, does the Sun deliver energy to Earth?
Why is a fluorescent light 22% efficient and an incandescent 5%?
What energy form is given off?
What energy form is wasted?
Why?
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