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Undergrad. Certificate in Renewable Energy. Deadline Monday, March 1 Five $1000 scholarships Raesi.colorado.edu/undergradcert
Too cheap to meter! Power from nuclear fusion.
Nuclear Fusion 21H1 + 21H132He1 +10n1 31H2 + 11H0 Using 21H1=Deuterium (D), 0.015% of all the hydrogen in the oceans. Each reaction3.65 MeV (each fission200 MeV) (carbon atom combustion3 eV)
But-- • Two positives repel, and can come near enough to react only at high temperatures and pressure. “Thermonuclear” • Plasma– confined only by magnetic fields. • ITER=International Thermonuclear Experimental Reactor
ITER • International Thermonuclear Experimental Reactor • D+D at 150 million deg C • 10 billion euros and counting • Maybe to operate in 2025 • Sustain 500 MW for 1000 sec
Points +: no CO2, lots of deuterium, no fission waste, no runaway -: How to couple energy to the grid? Not heat. Keeping the reaction going- 24/7 Cost Activation- the neutrons hit the walls.
Right sized fission reactors Do we have to build only giant plants? Capital cost, large components, large markets, not modular. Interest in smaller systems, same principles.
Review of Monday, Wednesday Nuclear reactions such as fission must balance, in Z and N (and A=N+Z) Fissions per second= Joules/sec (Watts) / (Joules/fission) And each fission releases 200 MeV=200x106 x “eV/Joule” =?????
Weights • You must balance grams in your equation, with 12 for carbon, 235 for 235U, etc, just like chemical reactions. • BUT-here we also use the information (200MeV) per atom, and we did not use the energy to burn one carbon atoms. • New concept-the mole. Use ratios: 12 grams of carbon hold 6.02x1023 atoms of carbon. 235 grams of 235U hold 6.02x1023 atoms of 235U. etc
So- • Fissions per year, per second of 235U from power. • Weight from the ratio of that many atoms to 235 grams, which hold the 6.02x1023 atoms.
Half life. By what factor is the 235U present at the forming of the earth, 4.5 billion years ago, decayed away? T1/2=0.7 billion years Count half lives=4.5/0.7=6.4 half lives. At six half lives, (1/2)6=1/64=0.0156 At seven half lives (1/2)7=1/128=0.0078 So we have about 1% of the original 235U. (found at 0.7% in ore)
Homework #7 due Monday March 1 • A typical fission reaction for uranium is • 1on1 +23592U 14313153I78 +AZ XX N +3 10n1, • where I is the element iodine. • (2) What are the atomic weight A, the atomic • number Z and the neutron number N for the • element XX in the specific fission reaction above, • one of many possible. • (7) If we fission I kg of 235U completely in one year, • at a plant efficiency of 30%, how many electrical GW • can we sell? • Each fission yields 200 x106 eV (200 MeV). 235 grams of • 235U hold 6.02x1023 atoms.
(4) The above specific process occurs with 2% probability. If we fission one kg of 235U completely, how many grams of 131I are produced? • (5) 131I has a half life of 8 days. If I start with one gram of it, how much is left after 32 days? • (2) Why is 131I a special concern?
Next week Monday- Comparison of electricity costs and suitability- fossil, solar, wind, nuclear…. Wednesday-Efficiency (chapter 7), CU steps Friday-Insulation