Editing Inertial confinement fusion (section)

=== Electricity generation ===
Inertial fusion energy (IFE) power plants have been studied since the late 1970s. These devices were to deliver multiple targets per second into the reaction chamber, using the resulting energy to drive a conventional [[steam turbine]].

==== Technical challenges ====
[[File:Electra Laser Generates 90K Shots.webm|thumb|alt=The Electra Laser at the Naval Research Laboratory demonstrated more than 90,000 shots over 10 hours at 700 joules. This kind of repetition rate would be needed for an IFC power plant. |The Electra Laser at the Naval Research Laboratory demonstrated more than 90,000 shots over 10 hours at 700 joules.<ref>Obenschain, Stephen, et al. "High-energy krypton fluoride lasers for inertial fusion." Applied optics 54.31 (2015): F103-F122.</ref>]]

Even if the many technical challenges in reaching ignition were all to be solved, practical problems abound. Given the 1 to 1.5% efficiency of the laser amplification process and that steam-driven turbine systems are typically about 35% efficient, fusion gains would have to be on the order of 125-fold just to energetically break even.{{sfn|Brueckner|1977|p=31}}

An order of magnitude improvement in laser efficiency may be possible through the use of designs that replace flash lamps with [[laser diode]]s that are tuned to produce most of their energy in a frequency range that is strongly absorbed. Initial experimental devices offer efficiencies of about 10%, and it is suggested that 20% is possible.{{Citation needed|date=February 2023}}

NIF uses about 330&nbsp;MJ to produce the driver beams, producing an expected yield of about 20&nbsp;MJ, with maximum credible yield of 45&nbsp;MJ.

==== Power extraction ====
ICF systems face some of the secondary power extraction problems as MCF systems. One of the primary concerns is how to successfully remove heat from the reaction chamber without interfering with the targets and driver beams. Another concern is that the released [[neutron]]s react with the reactor structure, mechanically weakening it, and turning it intensely radioactive. Conventional metals such as [[steel]] would have a short lifetime and require frequent replacement of the core containment walls. Another concern is fusion [[afterdamp]] (debris left in the reaction chamber), which could interfere with subsequent shots, including helium ash produced by fusion, along with unburned hydrogen and other elements used in the fuel pellet. This problem is most troublesome with indirect drive systems. If the driver energy misses the fuel pellet completely and strikes the containment chamber, material could foul the interaction region, or the lenses or focusing elements.

One concept, as shown in the HYLIFE-II design, is to use a "waterfall" of [[FLiBe]], a molten mix of [[fluoride]] salts of [[lithium]] and [[beryllium]], which both protect the chamber from neutrons and carry away heat. The FLiBe is passed into a [[heat exchanger]] where it heats water for the turbines.<ref>{{Citation |first1=Craig |last1=Olson |first2=Max |last2=Tabak |first3=Jill |last3=Dahlburg |first4=Rick |last4=Olson |first5=Steve |last5=Payne |first6=John |last6=Sethian |first7=John |last7=Barnard |first8=Rick |last8=Spielman |first9=Ken |last9=Schultz |first10=Robert |last10=Peterson |first11=Per |last11=Peterson |first12=Wayne |last12=Meier |first13=John |last13=Perkins |contribution=Inertial Fusion Concepts Working Group, Final Reports of the Subgroups |year=1999 |title=1999 Fusion Summer Study |publisher=Columbia University |url= http://sites.apam.columbia.edu/SMproceedings/6.InertialConcepts/6.IFE_Subgroups.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://sites.apam.columbia.edu/SMproceedings/6.InertialConcepts/6.IFE_Subgroups.pdf |archive-date=2022-10-09 |url-status=live |access-date=August 23, 2014}}</ref> The tritium produced by splitting lithium nuclei can be extracted in order to close the power plant's thermonuclear fuel cycle, a necessity for perpetual operation because tritium is rare and otherwise must be manufactured. Another concept, Sombrero, uses a reaction chamber built of [[carbon-fiber-reinforced polymer]] which has a low neutron cross section. Cooling is provided by a molten ceramic, chosen because of its ability to absorb the neutrons and its efficiency as a heat transfer agent.<ref>{{Citation |first1=I.N. |last1=Sviatoslavsky |first2=M.E. |last2=Sawan |first3=R.R. |last3=Peterson |first4=G.L. |last4=Kulcinski |first5=J.J. |last5=MacFarlane |first6=L.J. |last6=Wittenberg |first7=E.A. |last7=Mogahed |first8=S.C. |last8=Rutledge |first9=S. |last9=Ghose |first10=R. |last10=Bourque |contribution=SOMBRERO - A Solid Breeder Moving Bed KrF Laser Driven IFE Power Reactor |year=1991 |title=14th IEEE/NPSS Symposium on Fusion Engineering |publisher=Fusion Technology Institute, University of Wisconsin |url=http://fti.neep.wisc.edu/pdf/fdm862.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://fti.neep.wisc.edu/pdf/fdm862.pdf |archive-date=2022-10-09 |url-status=live |access-date=August 23, 2014}}</ref>

[[Image:Fusion target implosion on NOVA laser.jpg|thumb|right|upright|An inertial confinement fusion implosion in Nova, creating "micro sun" conditions of tremendously high density and temperature rivaling even those found at the core of the [[Sun]].]]

==== Economic viability ====
Another factor working against IFE is the cost of the fuel. Even as Nuckolls was developing his earliest calculations, co-workers pointed out that if an IFE machine produces 50&nbsp;MJ of fusion energy, a shot could produce perhaps 10&nbsp;MJ (2.8 kWh) of energy. Wholesale rates for electrical power on the grid were about 0.3 cents/kWh at the time, which meant the monetary value of the shot was perhaps one cent. In the intervening 50 years the real price of power has remained about even, and the rate in 2012 in [[Ontario, Canada]] was about 2.8 cents/kWh.<ref>{{cite web |url=http://www.ieso.ca/imoweb/marketdata/markettoday.asp |title=IESO Power Data |publisher=Ieso.ca |access-date=2014-08-23 |url-status=dead |archive-url=https://web.archive.org/web/20141002115248/http://www.ieso.ca/imoweb/marketdata/marketToday.asp |archive-date=2014-10-02 }}</ref> Thus, in order for an IFE plant to be economically viable, fuel shots would have to cost considerably less than ten cents in 2012 dollars.

Direct-drive systems avoid the use of a hohlraum and thereby may be less expensive in fuel terms. However, these systems still require an ablator, and the accuracy and geometrical considerations are critical. The direct-drive approach still may not be less expensive to operate.