The Diablo Canyon NPPT produces CO 2 -free electricity at half the state s (CA) average cost

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1 ECE_Energy for High-Tech Society 1 The Diablo Canyon NPPT produces CO 2 -free electricity at half the state s (CA) average cost

2 Nuclear Energy: Power for a High-Tech Society ECE_Energy for High-Tech Society 2 I. Introduction: America s Energy Outlook II. Principles of Energy Generation from Nuclear Fission 1. Transforming mass to energy 2. Fission chain reaction 3. Reactor control III. Nuclear Energy Technologies IV. 1. Basic reactor types BWR, PWR, ADS 2. Advanced energy technologies: Breeding, incineration and transmutation 3. Fuel cycles Nuclear Power in a Sustainable Energy Future

3 Introduction: America s Energy Futures Predictions (IEA) 1: World demand increases by 50% (25y: $20T, U.S. >$5T) Now : 450 Quad Btu/a 2030: 680 Quad Btu/a 2: Redistribution Industrial World vs. Developing World 40 Bbloe/a (220 GJ/a) vs. 6 Bbloe/a (34 GJ/a)) ECE_Energy for High-Tech Society 3 Boundary conditions 1: Disappearing resources (IEA) Now: beyond peak oil < 2030: beyond peak gas Limited uranium ( 235 U) resources 2: Mitigate impending climate change (IPCC) Improve energy efficiency Reduce GHG emissions (fossil fuels) Alternative energy sources (renewables, nuclear) 3: US energy security/independence in global context!? How to manage significant Boundary conditions? (only moderate growth possible)

4 Present Energy Demand (U.S.) ECE_Energy for High-Tech Society 4 Natural Gas 26% IEA 2004 IEA 2004 Coal 25% Oil 44% Coal 49.7% Nuclear 19.3% Total Nuclear 2.4% Hydro 2.6% Renewables 0.2% Electricity Hydro 6.5% Renewables Oil 3% 2.3% Other 0.5% 450 Quad Btu/a = 220GJ/a U.S. uses 25% of total global energy demand, 65% imported (Canada, Mexico,.., Middle East) Oil & nat. Gas & Coal 95% Main Energy Uses: Industry Transportation (liquid fuels) Agriculture Commercial & public Residential Growth potential bound. cond s. Nuclear Energy for high-tech societies

5 Past and Future of Nuclear Energy Production Steady increase of nuclear power output over past 20 years. Now equivalent: 24 quads of oil World (US) 443 (103) reactors 365 (100) GW ECE_Energy for High-Tech Society 6 U use: 67 kt/a World reserves 5 (15 est.) Mt Once-through cycle:200 years Reprocessing: ~10 3 years US:174 t weapons grade U for fuel mix Th use: little so far World reserves 15 Mt ~10 3 a with reprocessing 2007/8:3-4 new US reactors > 18 planned Potential: several new US reactors/a (@ $(1-1.5 )B/GW, 3 /kwh)

6 ECE_Energy for High-Tech Society 7 1. Operational reactor safety. 2. Resource limits of nuclear fuel ( 235 U/Pu, Th, ) 3. Safe capture, storage and sequestration of radiotoxic nuclear waste. 4. Prevention of proliferation of nuclear materials that can be used for weapons 5. Economy of nuclear energy. 6. Public perception. ( ) ( ) ( )

7 Nuclear Energy: Power for a High-Tech Society ECE_Energy for High-Tech Society 8 I. Introduction: America s Energy Outlook II. Principles of Energy Generation from Nuclear Fission 1. Transforming mass to energy 2. Fission chain reaction 3. Reactor control III. Nuclear Energy Technologies IV. 1. Basic reactor types BWR, PWR, ADS 2. Advanced energy technologies: Breeding, incineration and transmutation 3. Fuel cycles Nuclear Power in a Sustainable Energy Future

8 Nuclear Rearrangement Energies M (N,Z) < N M n + Z M p M B(A=N+Z) In assembly of a nucleus B= Mc 2 is released to outside Einstein: equivalence mass = energy E = M c 2 Energy release in fission A 2A/2 ECE_Energy for High-Tech Society 9 ( ) M= M 2 9 = 47 = 47 µ 4 10 fission M U mg E g c J ( ) M TNT = 1t E 4 10 J Fe Ni M= M combustion 9

9 Energy Generation from n th -Induced Fission ECE_Energy for High-Tech Society * U + n U 2 FF + 2(3) n + 200MeV th 236 * * Example : U La + Br + 2n 236 U* fission fragment n fission fragment n n fast Converts 0.1% of the mass into energy 1g 235 U/day = 1MW 10 8 x chemical energies E ff = 168 MeV E n tot = 5 MeV E γ = 7 MeV FF β-decay = 27 MeV = 207 MeV Q total Neutrons per fission: k = 2.5±0.1 k=1 critical (chain rxn) Fission neutrons are fast: n-energies <E n > 2 MeV n s less likely to induce further 235 U fission Most fission neutrons are lost and/or not useful for further fission Fission fragments = reactor poison, stop chain reaction. k < 1!!!

10 The Fission Chain Reaction Nuclear Fission Power 11 Leo Szilard 1938 Neutron multiplication through fission k=2.4, minus losses (capture, leaking,..), effective k < 2.4. One n used in fission effective multiplication k-1: dnn 1 = ( k 1) Nn dt τ ( k 1 N ( t) = N (0) e ) n n t τ k >1: exponential avalanche of f-neutrons τ = time between gen s (τ ~ 40µs in reactors τ ~ ns in explosives) k = k + k eff prompt delayed Reactor Control τ Characteristic T = period: ( k 1) eff k eff 1 e.g.,k eff =1.03 W. Udo Schröder, 2004

11 Fission and n-capture Probabilities ECE_Energy for High-Tech Society 12 Neutron Capture and Fission Cross Section (b) Quantum Mech. resonance 235 U 0.7% 238 U 99.3% cross section Probability nat U: 99.3% 238 U, 0.7% 235 U Fission cross sections 238 U: σ f ~ 1 b for E n > 1 MeV 0 b for E n < 1 ev dominating: scattering (~8b) + capture 235 U: σ f ~ 1-2 b for E n > 1 MeV ~ 10 3 b for E n < 1 ev dominating: (n, f) fission Observed fission due to (0.7%) 235 U isotopically enrich 235 U (4% for lightwater reactors) How to induce a self-sustaining fission reaction? Recycle and slow down fission neutrons! Neutron Kinetic Energy (ev) Slowing-down (moderation) of fission neutrons by elastic scattering on moderator nuclei (H, C, )

12 β Delayed Neutrons 87% of fission energy ( 200 MeV) promptly in fission s 13% emitted in β-decays of fission fragments, range of life times delayed emission of β +, β, ν e, γ, n ECE_Energy for High-Tech Society % of neutrons from 236 U fission are delayed (occur after fission) essential for sustaining chain rxn + control function 87 Br (55.6 s) β (98%) β (2%) 87 Kr (76 m) Example β 86 Kr+n 87 Rb ( a) β 87 Sr β delayed neutron < τ> 80 s k<1 k eff 1 Effective neutron multiplication factor, but not all survive Most have wrong energy for 235 U chain rxn

13 Neutron Moderation Fast Neutrons from Fission Slow down Fission neutrons too energetic, thermalize to maximize σ f multiple elastic scattering ( moderation ) moderator: small σ capt! Nuclear Fission Power 14 A=12 A=65 A=238 Need:2 MeV ev/2mev= 10-8 Need to miss 238 U capture resonances (2eV< E n <10keV) H 2 O, D 2 O, Be, C(graphite), prevent leakage n-reflector moderator U U U moderator A=1 d<λ fast W. Udo Schröder, 2004 H, D are best moderators H can capture neutrons: H+n th D+2.2 MeV

14 Reactor Control and Safety Reactivity ρ = (k eff -1)/k eff Reduce by n absorbers Cd, B (control rods, moderator) Automatic: fission products= reactor poisons Temperature dependent reactivity coefficient dρ/dt<0 Negative reactivity desirable. Cd Control Rods U U U ECE_Energy for High-Tech Society 15 In BWR/PWR: Doppler Effect: broadening of resonance and n spectrum leads to increased n- capture by 238 U dρ/dt < 0 Density Effect: hot moderator expands, lower density longer mean free path, less moderating efficiency dρ/dt < 0 Dilatation Effect: hot moderator delays slowing down dρ/dt < 0 dρ/dt = -(0.5-1)x10-4 / 0 C PWR dρ/dt = - 1x10-3 / 0 C Breeder, EA

15 Nuclear Energy: Power for a High-Tech Society ECE_Energy for High-Tech Society 16 I. Introduction: America s Energy Outlook II. Principles of Energy Generation from Nuclear Fission 1. Transforming mass to energy 2. Fission chain reaction 3. Reactor control III. Nuclear Energy Technologies IV. 1. Basic reactor types and open fuel cycle BWR, PWR, HTR 2. Advanced energy technologies: Breeding, incineration and transmutation 3. Advanced fuel cycles Nuclear Power in a Sustainable Energy Future

16 Open Fuel Cycle Nuclear Fission Power 17 weapons Pu MOX fuels W. Udo Schröder, 2004

17 Pressurized-Water Thermal Power Reactor naval applications Light water as moderator and primary coolant p ~ 160 bar (at) secondary steam el. generators ECE_Energy for High-Tech Society %-enriched UO 2 pellets. core 3.5 m x 3.5 m Ø: 140 t fuel p=160 bar (2300psi), C cooling towers efficiency 30-40% pressurizer tower 13.5m 4.4m Ø

18 Nuclear Power Plant 1-2GW 2-3 B$/NPPt Fail-safe operation Negative Reactivity Negative feedback loops: Reaction subsides when ECE_Energy for High-Tech Society 19 coolant gets too hot or disappears (less dense, less moderation) fuel gets too hot (n capture increases) control rods are not moved out Passive safety: Pressure reactor vessel ~1 thick steel, pressure tubes, Reactor containment building with several 3-4 foot thick concrete walls, concrete+water shielding, pools for fuel elements

19 Advanced Reactors: Pebble-Bed HTR He (inert gas) cooled T C C- moderator/reflector ECE_Energy for High-Tech Society 20 Continuous throughput and replacement of pebble fuel elements Strongly negative reactivity. Core has high surface/volume ratio, low power density. Fail-safe operation. Modular reactor batteries (@250MW) Built in S-Africa, China

20 Modular Pebble Bed Reactor Fuel Pebbles Small UO 2 spheres embedded in graphite matrix, silicon carbide/graphite shells ECE_Energy for High-Tech Society 21

21 Radiotoxicity of Nuclear Waste ECE_Energy for High-Tech Society 22 Natural uranium Radio toxicity vs. time after shutdown, of spent fuel from pressurized water uranium reactor (PWR), U/Pu breeder, and Th/U fuel cycle. FP indicates the faster decay of fission products. Multiple reprocessing, less residuals. Reprocessing involves robotics because of Tl gamma radiation not for extremists garage! Most strategic issues solved (David, Nifenecker, 2007)

22 Nuclear Fuel Storage & Transport ECE_Energy for High-Tech Society 23 Progress Energy

23 Nuclear Energy: Power for a High-Tech Society ECE_Energy for High-Tech Society 24 I. Introduction: America s Energy Outlook II. Principles of Energy Generation from Nuclear Fission 1. Transforming mass to energy 2. Fission chain reaction 3. Reactor control III. Nuclear Energy Technologies IV. 1. Basic reactor types BWR, PWR, HTR 2. Advanced energy technologies: Breeding, incineration and transmutation 3. Fuel cycles Nuclear Power in a Sustainable Energy Future

24 Timeline of Advanced Reactors/Fuel Cycles ECE_Energy for High-Tech Society 25 GNEP framework (now includes U.S., U.K.) 2030: Gen IV designs studied, modelled, tested: Very high-temperature reactors (VHTR) Sodium-cooled fast reactors (SFR) Reactors cooled by supercritical water (SCWR) Lead-cooled fast reactors (LFR) Gas-cooled fast reactors (GFR) Molten-salt reactors (MSR) Already testing Gen IV: France, Japan, S-Africa, China, India Operational reactor safety; Resource limits of nuclear fuel ( 235 U/Pu); Safe capture, storage, sequestration of radiotoxic waste; Prevention of proliferation of nuclear materials for weapons; Economy of nuclear energy.

25 Fuel Breeding 239 Pu/ 233 U Breeding Technologically understood, several working research/test reactors Fast (neutron spectrum) U reactor: n-capture without fission ECE_Energy for High-Tech Society 26 U Pu Cycle + n + n β 239 β t 23min 93Np Pu 12= d ( ) U n U a Continued n capture/β decay Pu n β h 92U ( ) Th U Cycle Pa a + n + n Pu Pu + n Isotope mix: Not useful for nuclear fuel/weapons extensive isotope separation β 233 β t 22min d 92U = ( ) Th n Th Pa a Pu India pursues Th reactor large Th resources, small waste problem. (Mumbay test reactor)

26 Nuclear Transmutation Nuclear Fission Power β s Tc n Tc Ru β h I n I Xe stable isotopes Transmutation of actinides: n-induced fission of Pu, Np, Am, Cm radioactive and nonradioactive fission products (most with half-lives < 30 a ). Transmutation of fission products carried out by specific nuclear reactions induced by neutrons, protons, photons, light nuclei, e.g., resonant n- capture. Need high n flux Φ n ~10 16 /s cm 2 C.D. Bowman et a., NIM A320, 336 (1992) H. Nifenecker et al., Accelerator Driven Subcritical Reactors, IOP Bristol, 2003 W. Udo Schröder, 2004

27 Advanced Closed Fuel Cycle ECE_Energy for High-Tech Society 28 Aqueous nuclear fuel reprocessing scheme. Spent fuel rods are cut open and dissolved chemically. Isotopic separator provides different streams for uranium, actinides and fission products. U and Pu recast into fuel elements for another reactor cycle. Fission products and some transactinides are vitrified and stored in long-term repository.

28 Transmutation of Spent Nuclear Fuel Spallation for neutron multiplication incineration of waste Advanced reactor development under GNEP program ECE_Energy for High-Tech Society 29

29 Nuclear Power in a Sustainable Energy Future Most promising and potent: Advanced nuclear power, redirection of electricity generation mainly to nuclear. Develop synfuels from coal/nat. gas. Need massive renewal of energy infrastructure (Also required to admit renewable technologies). Adjust public policy accordingly. ECE_Energy for High-Tech Society 30 Develop and Employ Advanced Nuclear Power: Continue to improve the safety of nuclear reactors and processing plants. Test/construct advanced modular nuclear sites of existing plants. Test/construct advanced burner/transmuter reduce radiotoxic waste. Import/develop closed nuclear fuel cycle technologies. Develop/test proliferation-safe reprocessing methods (e.g., UREX+). Test/develop a closed Th/U breeder fuel cycle. Develop ADS systems, high current accelerator technology. Develop the chemistry of molten salt mixtures, molten salt test reactor. Expand the radio-chemistry of actinides, transactinides and fission products. Operating a semi-permanent nuclear waste depository, flexible strategy.