NUCLEAR REACTORS - EPSc 221epsc221.wustl.edu/Lectures/221L36.pdf · NUCLEAR REACTORS: ... (advanced...
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My use in U City= 200 kwh/mo/person => 0.3 kw continuous (= 3 *100-watt bulbs) per person
@38% efficiency, could be supplied by 0.3 g 235U/y or 1 ton of coal/y
http://www.chemincontext.com/CONFChem/FuelPellet.htm
Nuclear Fuel PelletCost $3 ~ 7 g total, with ~ 0.3 g 235UEnergy equivalent: 1 ton coal
NUCLEAR REACTORS
To supply a 1000 MWe power plant for a day, assuming a realistic 38% efficiency, need either:
2.7 kg 235U
or 10,000 tons = 107 kg of coal!
http:// .wsgs.uwyo.edu/coalweb/trains/unit.aspx
Unit Train:100 cars @ 100 tons ea
E = mc2 Einstein (1905) Annihilate 1 g => E = (0.001 kg)(3x108 m/sec)2 = 9 x 1013 joules
15,000 bbl of oil or 3300 tons of coal Annihilate 1 lb => E = 1010 kWh = USA electrical needs for 1.1 days = drive car 300,000 times around the Earth
Curve of Binding Energy/nucleon (= protons & neutrons) Release Energy by Fusion of light elements Fission of heavy elements
FUSION
Need ~ 107 K ! Very little radwaste- products not radioactive Some produced by neutron bombardment
of reactor parts Princeton Tokamac: 12/93 (Jan 94 Physics Today)
50:50 DT rxn: 2H + 3H => n (14 MeV) + 4He (3.5 MeV) 6.4 MW released, but 24 MW went in!
The deuterium in ~10 km3 of seawater would, if all fused, provide energy equal to the pre-industrial fossil fuel supply of the entire world. Deuterium in total ocean has an energy value of >100 million times that of the world's pre-industrial fossil fuel supply. Energy supplies practically unlimited if we could use 1H !
HYDROGEN BURNING (fusion): Thermonuclear reaction for Main Sequence stars.
CNO Cycle Net Reaction:
4 1H => 4He + 7 ϒ + 2 ν + 26.73 MeV E = 931.5 (4 * 1.007825 - 400260) = 26.73 MeV T ~ 107 K required Every second the Sun:
Consumes 609.6 million metric tons of H Produces 605.3 million metric tons of He
Difference 4.34 million metric tons of matter = 3.9 x 1026 J of energy!
=> Solar luminosity = 3.9* 1026 Watts
NUCLEAR FISSION
Discovered by German radiochemists Otto Hahn & Fritz Strasmann (1938) Bombarded Uranium with neutrons, produced Ba- had split atom!
Fission of a heavy atom produces: 2 neutron-rich product nuclei of unequal size with z=30 (Zn) to z=65 (Tb) 2.5 neutrons on average Alpha particles (α)
200 MeV (= 32 pJ /atom) => Neutron-rich product nuclei emit b- 's in complex decay series
FISSION produces ~200 MeV/atom => x (1.602 x 10-19 J/eV )(6.023x1023)(1 g/235) = 8.2 x 1010 J/g 235U (cf. mc2 = 9 x 1013 J/g)
Fission 1 g of 235U, 239Pu, or 233Th = 8.2 x 1010 J/g. = heat of combustion of 13.4 barrels of crude oil = heat of combustion of ~2.7 metric tons of coal (wt. ratio = 1 : 2.7 x 106 ).
235U only natural material fissionable with slow neutrons 239Pu made in breeder by neutron bombardment of non-fissionable 238U 233Th made in breeder by neutron bombardment of non-fissionable 232Th
http://www.science.uwaterloo.ca/~cchieh/cact/nucfig/fissionyield.gif
U-235ThermalNeutronFissionProducts
A=118
A =137A=95
TYPICAL FISSION REACTIONS & subsequent b- decay events of products 1n + 235U => 236U* => 144Ba + 89Kr + 3 1n 144Ba => 144La => 144Ce => 144Pr => 144Nd (long lived) 89Kr => 89Rb => 89Sr => 89Y (stable)
1n + 235U => 236U* => 140Xe + 94Sr + 2 1n 140Xe => 140Cs => 140Ba => 140La => 140Ce (stable) 94Sr => 94Y => 94Zr (stable)
NUCLEAR BOMB
Exceed critical mass
Get uncontrolled chain reaction = Explosion
ndep.nv.ogv
Flash Fireball Blast Fallout
NUCLEAR REACTORS
Enrico Fermi Concept of controlled chain reaction First nuclear reactor CP-1 (1942) Controlled Nuclear reaction: Achieve & maintain criticality
(cf. bomb)
StLPD 11/21/12
Controlled, Sustained Chain Reaction 235 U + n = fission products + absorbed n + 1.0 free n + 200 MeV
http://www.atomicarchive.com/Fission/Fission2.shtml
NUCLEAR REACTORS:
World 450 nuclear reactors in ~31 countries USA 99 France 58
Many different designs USES:
Power Generation Neutron sources Radioisotope production
FUELS: Unenriched U (natural ab: 99.27 238U 0.71% 235U) Enriched U (typically 4-6% 235U) Highly enriched (e.g., 47% 235U) Other (e.g., artificially produced, fissionable 239Pu; 233U)
REACTOR COMPONENTS Fuel Elements: ceramic coated 235U enriched pellets (< 1 cm dia) Fuel Rods 12' long, have metal cladding, packed into Fuel assemblies: ~ 15x15 = 225 rods
Reactor has ~200 assemblies/reactor (typically > 70 tons of U)
Self moderating fuel element - pellets have very hi thermal expansivity- EBR II research breeder (U-Pu-Zr alloy) MHTGR- hi T- U C SiC pellets (stable to 1800°C- can withstand total coolant loss)
Moderator (slows neutrons- thermal neutrons easily captured) e.g., graphite, Be, D2O, H2O
Control Rods (= neutron absorber; e.g. cadmium; boron steel)
Coolant LWR’s “light water reactor” Most in USA; two subtypes PWR's (pressurized) & BWR's (boiling) HWR’s Heavy water (more effective moderator) Candu reactors- can use natural U as fuel Liquid Na or K = Breeders He gas (unreactive !) AGR's (advanced gas-cooled) HTGR's (high T gas-cooled)
Nuclear Fuel PelletCost $3~ 7 gEnergy equivalent: 1 ton coal~107 pellets in power plant
http://www.chemincontext.com/CONFChem/FuelPellet.htm
http://www.uic.com.au/nfc.htm
PWR Fuel Assembly A 1000 MWe reactor has ~200 fuel assemblies that contain about ~75 tons U
BREEDER REACTORS: can produce more fuel than consume! Neutron bombardment produces either: Fissionable 239Pu from non-fissionable 238U
Fissionable 233U from non-fissionable 232Th Breeders have:
Small core Very highly enriched fuel Na coolant (molten; need hi T) No moderator: hi T so capture fast neutrons
France: Super Phenix 1200 MWe commercial breeder (Craig et al. p. 131)
FBR No moderator Hi T- Na cooled Pu core, 238U rods 1.2 Pu atoms are formed for each Pu atom consumed
http://www.cameco.com/uranium_101/fact.php
PROBLEMS Nuclear Accidents Lack of Standardization Reactors do not go up as nuclear explosions Reactors get hot, have chemical explosions 21 uncontrolled reactions since 1953 (US News 10/11/99 p. 44)
Chalk River, Ottawa, Canada (12/12/52) Accidental removal of 4 control rods Partial meltdown; no injuries
Windscale, England (10/7/57) Fire, radionuclide release Tokiamura nuclear processing plant, Japan 9/30/99. Mixed 7x too much in nitric acid (~35 lbs U) => blue flash 200 trains stopped, 241 schools closed, 10k people checked; >100 exposed; 2 fatalities
Kyshtym, South Urals, USSR (ca. 3/1958) Explosion Release of reprocessed fission wastes from weapons plant? Large evacuation >100 km2 contaminated; red dust & defoliation; Techa R water highly radioactive Trabalka et al. (1979) Oak Ridge Env.Sci. Pub. #1445
Three Mile Island, Harrisburg, PA (3/28/79) PWR Pump failure Valves on backup pumps improperly left closed Coolant loss Core Expose Partial meltdown 14-15 Ci (5.5 x1011 Bq) released (131I; 8 day half life)
Chernobyl, Ukraine (4/26/86) 95 tons of U @ avg. of 610 reactor days. Demand surge during a Test: No equipment failure Workers violated procedures, removed all but 8 control rods to inc. power Reactor went out of control in ~ 3 sec.
Zr in fuel elements reacted w/ water, released H2 gas that exploded Core housing ruptured, roof lifted, Fire Hot lumps of graphite & uranium oxide fuel thrown out; ~ 10% of core material dispersed into atmosphere. Core temp continued to increase for at least 9 days.
Plume with 131I (8 days), 134,137Cs, 89,90Sr, 141,144Ce, Pu moved northwest 50 MCi = 106 x TMI
Affected entire northern hemisphere. 31 fatalities; 237 cases acute radiation sickness; 1800 cases thyroid cancer 20,000 people received 250 mSv (25 rem) ; 200,000 got 100 mSv (10 rem) 200,000 relocated from 4,300 km2 exclusion zone No increase in leukemia seen to 2004 $15 billion in damage.
Partly as a consequence, much of Europe has halted new nuclear construction: Sweden, Spain, Netherlands, West Germany, Yugoslavia, UK, Switzerland
Fukushima Daiichi, Japan (3/11/2011) #2 M8.9 Earthquake, 15m Tsunami Emergency generators failed
Pump failures, Coolant Loss PWR Reactors 1-3 overheated, meltdown Explosions Radionuclide Release (24 MCi ~ 900PBq)
More explosions, Spent fuel (>1500 rods) in Unit 4 exposed Evacuation of >150,000 people
Permanent evacuation of 12-mile radius Planned phase out of Japan’s nuclear power industry
Financial Problems Delays, Regulations, Permits, Cost Overruns LILCO Long Island Lighting Co., Shoreham Plant- Controversy, Administrative delay $300 million est. cost in 1973 -> $5.5 billion when completed in 1984 Never produced power Sold to state for $1 in return for rate increase
WPPS Washington Public Power Supply System 115 utility consortium
Defaulted in 1983 on $2.25 billion in municipal bonds In USA:
~70 Utility lawsuits against fed for no waste removal; totaling several $B Maine Yankee won $82M settlement 10 plants need to be decommissioned, at $1 B each 12 failed nuclear projects have caused near financial ruin for the utilities
Many investors would now sell stock if nuclear construction plan were announced by utility
USA 104 => 99 reactors in 31 states19% of electricity, 6 states dominantly nuclear, 33 states dominantly coal
VT (80%) SC ME VA NY CT Reactors- numerous designs, run by > 50 different utilities Radwaste- spent fuel accumulating @ reactor sites- no reprocessingDOE has spent >$ 13 billion on plans for repository
No 4 construction permits
Number of operating reactors & nuclear generating capacity shrinking
France 58 reactors 76% of electrical powerMostly, single design (PWR); minimal siteing problemsElectricite de France (EDF) Government-owned utilityRecycling of spent fuel, separating U & Pu