Inertial Confinement Fusion andThermonuclear Reactors MilanKalal FacultyofNuclearSciencesandPhysicalEngineering Czech Technical University in Prague 11519 Prague 1, Czech Republic ATHENS, November20,2013, Prague, CzechRepublic
Background Situation Analysis Under current estimates the oil reserves will run out after 40 years, natural gas after 60 years and coal could last for two more centuries. Although energy provided by various renewable sources, such as water power plants, solar power plants, wind, geothermal energy etc. will undoubtedly play important niche roles at the beginning of this century, they will not be able to sustain the central baseload demands of future society. Presently, there are only two key players which need to be dealt with and relied upon to solve the problem: fission and fusion.
Fission or Fusion ? Both fission and fusion are forms of nuclear energy. However, they can be differentiated by various attributes, including their: • capital costs • safety • environmental impact • proliferation problems • fuel availability
Fission Assessment If the presently known reserves of fission fuels were used to sustain the full electrical energy needs of future populations, these fuels would probably not last for more than about 100 yearsusing conventional thermal reactors with a once-through fuel cycle. However, such reserves could be made to last for thousands of years if they were efficiently used in breeder reactors with a reprocessed-fuel cycle. Uranium could also, in principle, be extracted from sea water, although we do not yet have the technology to achieve this.
Any Need for Fusion Energy? Electrical power generation in the 21st century will be an industry worth tens of trillions of dollars, and there will be an assured and significant growth in demand from the developing world. The question really is whether we will have a fusion-reactor product that will be sufficiently attractive to compete in this marketplace? If we do, then fusion will beneeded. Even more so should we take into account the climate change caused by heating of the planet due to an increase of the CO2in the atmosphere from burning fossile fuels.
This challenge must be resolved and solved today… Not 50 years from now
Fusion Assessment The First Generation Fusion Reaction
Lawson Criterion Ti ≈ 2 × 108 K n E ≥ 0.5 × 10 20 m -3s Example: - Reactor Chamber diameter 10 m - Typical energyreleased 340 MJ (equivalent of 75 kg TNT) - This is contained in 1 mg of D-T fuel - Energetic Amplification (gain) Q: For 17.6 MeV energy released and 30 keV (up to 60 million K) used for heating Q = 580. Notes: 1 eV = 1.6022×10 -19 joules; Average particle thermal kinetic energy is 1 eV per 11,600 K.
Fusion Assessment Lithium - the primary fuel for first-generationdeuterium-tritium fusion reactors is significantly more abundant in the Earth's crust than either of the primary fission fuels, uranium or thorium. Lithium is also about 50 times more abundant than uranium in sea water. And deuterium, which is arguably the ultimate fusion fuel for second-generationdeuterium-deuteriumfusion, comprises 0.015% of all of the hydrogen on Earth by atomic ratio. Thus, (deuterium) fusion is a fuel reserve that will be available to us for as long as the Earth exists.
Comparison of Safety of Fusion and Fission Power The stored energy in the fuel of a fission core is sufficient for about two yearsof operation. So although adequately safe fission reactors probably can be designed, this stored energy could, in principle,trigger severe accidents. In contrast, the amount of fuel in the core of a fusion reactor - of whatever class that we can conceive of today - is sufficient, at most, for only a few secondsof operation. The fuel would also be continually replenished.
The other disadvantage of fission is that spent fuel rods in a fission core contain gigaCuries of radioactivity in the form of fission products and actinides, some with half-lives of hundreds or even millions of years. Such radionuclides therefore have to be disposed of into securely guarded repositories deep underground. In contrast, the main potential for generating radioactive waste from fusion comes from neutron activation of the structural materials that surround the reactor. A judicious choice of these materials can reduce fusion's potential biological hazard by many orders of magnitude relative to spent fission fuel. Indeed, such materials would not need to be disposed of in a long-term waste repository.
Perhaps most importantly, we must recognize that the exploitation of breeder reactors to extend the fission fuel reserves of uranium and/or thoriumbeyond this century will result in significant reprocessing traffic of 239Pu and/or 233U. Although international safeguards and security could no doubt be implemented, the diversion and exploitation of even a few kilograms of these materials would be a severe test of the public's stamina for this energy source. Therefore: !!! Let’s go Fusion !!!
Fusion process as a source of energy Plasma self-heating Tritium replenishment Li Electricity, Hydrogen
Deuterium fuel Tritium fuel Conventional Turbine Conventional Generator Heat Exchanger Fusion Plasma Tritium Breeding Blanket Electric Power Grid Fusion power plant: Electricity generation Fusion Power Core
Which Way to Go? There are two major approaches: • Magnetic Fusion Energy (MFE)(Tokamaks, Stellarators etc.) • Inertial Fusion Energy (IFE)(High Power Lasers, Heavy-Ion Accelerators and Z-Pinch Drivers)
MFE (Tokamak) • Low density: ~1012 cm–3 , t >100s • Ultra high vacuum chamber necessary ~ 10-11 Torr • Whole in One System • Life time of the whole system ~ 1year…
ITER Ports for ECH&CD Central Solenoid Nb3Sn, 6 modules Blanket Module 421 modules Vacuum Vessel 9 sectors Outer Intercoil Structure Cryostat, 24 m high x 28 m dia. Toroidal Field Coil Nb3Sn, 18, wedged Port Plug (IC Heating) 6 heating 3 test blankets 2 limiters/RH diagnostics Poloidal Field Coil Nb-Ti, 6 Torus Cryopump 8 Machine Gravity Supports Divertor 54 cassettes
However !!! It is not clearthat the conventional tokamak approach will lead to a practicable commercial power plant that anyone will be interested in buying. This is a consequence of its projected: • low power density • high capital cost • high complexity • expensive development path
~1mm Direct drive target
Gold hohlraum X-ray laser laser 5mm Indirect drive target
Cone shell target Plastic shell Au Cone GEKKO XII PW laser for implosion for heating 9 beams 1.053µm 0.53µm 1.2 kJ / 1ns IFE targets Indirect drive target (Hohlraum ~5mm size) Direct drive target ~1mm size
LFE (Laser Fusion Energy) • High density: 1024 cm-3 (~100 atm) t >10-10s • Low vacuum ~10-5 Torr necessary • Modular system; laser and target chamber are SEPARATED • Small target size (~4 mm); negligible radioactivity • Long lifetime of the target chamber ~ 30 years
Overview of FIREX-II Implosion laser 50 kJ Heating laser 50 kJ Pulse width 10 ps FIREX (Fast Ignition Realization Experiment) Purpose: Establishment of fast ignition physics and ignition demonstration Starting Conditions : high denisity compression(already achieved), : heating by PW laser (1keV already achieved）
A 100 ton of coal hopper runs a 1 GW Power Plant for 10 minutes. Same filled with IFE targets runs a 1 GW Power Plant for 7 years.
Outlook into the IFE Future Alternative physics approaches are particularly important if we are ever to exploit the so-called advanced fusion fuels, such as D-D, D-3He and p-11B: D + D → T (1 MeV) + p (3 MeV) D + 3He → 4He + p + 18.3 MeV p + 11B → 3 4He + 8.7 MeV Such fuels suggest several advantages over conventionaldeuterium-tritium reactions. For example, they produce few or even no neutrons, and they could even directly convert charged fusion products into electricity without the need for a conventional thermal cycle. However, such fuels would require significantly higherplasma densities and temperaturesto realize the same fusion power density as deuterium-tritium plasmas.
Challenges to be resolved in IFE development