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The '''Energy Multiplier Module''' ('''EM2EM²''' or '''EM squared''') is a [[nuclear fission]] power [[Nuclear reactor technology|reactor]] under development by [[General Atomics]].<ref>{{cite news |title=JENKINS: Hot young prospect to replace old San Onofre reactors |author=Logan Jenkins |url=http://www.sandiegouniontribune.com/sdut-jenkins-hot-young-prospect-to-replace-old-san-2013jan10-story.html |newspaper=San Diego Union Tribune |date=10 January 2013 |accessdateaccess-date=19 January 2013}}</ref> It is a fast-neutron version of the [[Gas Turbine Modular Helium Reactor]] (GT-MHR) and is capable of converting [[spent nuclear fuel]] into electricity and industrial process heat.<ref>{{cite news|url=http://www.signonsandiego.com/news/2010/feb/24/company-has-plan-for-small-reactors/|title=Company has plan for small reactors|last=Freeman|first=Mike|date=Feb 24, 2010|work=[[San Diego Union Tribune]]}}</ref>

[[File:Reactor - Isometric Cut-Away View.jpg|thumb|Cut-away view of the EM2 core.]]

==Design specifications==

EM2 is an advanced modular reactor expected to produce 265 MW_e (500 MW_th) of power with evaporative cooling (240 MW_e with dry cooling) at a core outlet temperature of {{convert|850|°C|-2}}. The reactor will be fully enclosed in an underground containment structure for 30 years without requiring refueling.<ref>{{cite web|url=http://www.ga.com/advanced-reactors |title=Advanced Reactors |publisher=General Atomics |accessdateaccess-date = Feb 19, 2018}}</ref> EM2 differs from current reactors in that it does not use water coolant but is instead a [[gas-cooled fast reactor]], which uses [[helium]] as a coolant for an additional level of safety. The reactor uses a composite of [[silicon carbide]] as a fuel cladding material, and [[zirconium]] siliciidesilicide as [[neutron reflector]] material. The reactor unit is coupled to a direct-drive helium [[closed-cycle gas turbine]] which in turn drives a generator forto the production ofproduce electricity.

The nuclear core design is based upon a new conversion technique in which an initial “starter”"starter" section of the core provides the [[neutrons]] to convert fertile material (used nuclear fuel, thorium, or [[depleted uranium]]) into burnable [[fissile]] fuel.<ref>“With"With Disposal Uncertain, Waste Burning Reactors Gain Traction – EM2 to Burn LWR Fuel,”" Nuclear New Build Monitor, March 15, 2010</ref> First generation EM2 units use enriched uranium starters (approximately 15 percent [[U235]]) to initiate the conversion process.<ref>{{Cite webjournal |last = Choi |first = H. |title = A Compact Gas-Cooled Fast Reactor with an Ultra-Long Fuel Cycle |urljournal = https://dx.Science and Technology of Nuclear Installations |volume = 2013 |pages = 1–10 |doi.org/ = 10.1155/2013/618707 |accessdate year = 192013 |doi-access = Februaryfree 2018}}</ref> The starter U235 is consumed as the fertile material is converted to fissile fuel. The core life expectancy is approximately 30 years without refueling or reshuffling the fuel.

[[File:EM2-cross-section.jpg|thumb|Cross-section of the EM2 reactor vessel and power conversion unit.]]

Substantial amounts of useableusable fissile material remain in the EM2 core at the end of life. This material can be reused as the starter for athe second generation of EM2s, without conventional [[nuclear reprocessing]].<ref>{{cite web|url=http://www.ga.com/advanced-reactors |title=Advanced Reactors |publisher=General Atomics |accessdateaccess-date = Feb 19, 2018}}</ref> There is no separation of individual heavy metals required and no additional [[enriched uranium]] needed. Only [[fission products]] would be removed, which would decay to near-background radiation levels in about 500 years compared to conventional spent fuel, which requires about 10,000 years.<ref>{{Cite webjournal |last = Choi |first = H. |title = A Compact Gas-Cooled Fast Reactor with an Ultra-Long Fuel Cycle |urljournal = https://dx.Science and Technology of Nuclear Installations |volume = 2013 |pages = 1–10 |doi.org/ = 10.1155/2013/618707 |accessdate year = 192013 February|doi-access = free 2018}}</ref>

The nuclear core design is based upon a new conversion technique in which an initial “starter” section of the core provides the [[neutrons]] to convert fertile material (used nuclear fuel, thorium or [[depleted uranium]]) into burnable [[fissile]] fuel.<ref>“With Disposal Uncertain, Waste Burning Reactors Gain Traction – EM2 to Burn LWR Fuel,” Nuclear New Build Monitor, March 15, 2010</ref> First generation EM2 units use enriched uranium starters (approximately 15 percent [[U235]]) to initiate the conversion process.<ref>{{Cite web |last = Choi |first = H. |title = A Compact Gas-Cooled Fast Reactor with an Ultra-Long Fuel Cycle |url = https://dx.doi.org/10.1155/2013/618707 |accessdate = 19 February 2018}}</ref> The starter U235 is consumed as the fertile material is converted to fissile fuel. The core life expectancy is approximately 30 years without refueling or reshuffling the fuel.

Substantial amounts of useable fissile material remain in the EM2 core at the end of life. This material can be reused as the starter for a second generation of EM2s, without conventional reprocessing.<ref>{{cite web|url=http://www.ga.com/advanced-reactors |title=Advanced Reactors |publisher=General Atomics |accessdate = Feb 19, 2018}}</ref> There is no separation of individual heavy metals required and no additional [[enriched uranium]] needed. Only [[fission products]] would be removed, which would decay to near-background radiation levels in about 500 years compared to conventional spent fuel, which requires about 10,000 years.<ref>{{Cite web |last = Choi |first = H. |title = A Compact Gas-Cooled Fast Reactor with an Ultra-Long Fuel Cycle |url = https://dx.doi.org/10.1155/2013/618707 |accessdate = 19 February 2018}}</ref>

All EM2 heavy metal discharges could be recycled into new EM2 units, effectively closing the [[nuclear fuel cycle]], which minimizes [[nuclear proliferation]] risks and the need for long-term repositories to secure nuclear materials.

==Economics and workforce capacity==

EM2 power costs are expected to be lower due to high power conversion (from thermal input to electric output) efficiency, a reduced number of components, and long core life. EM2 is expected to achieve a conversion[[thermal efficiency]] of above 50% due to its high core outlet temperature and closed Brayton power cycle. The Brayton cycle eliminates many expensive components, including [[steam generatorsgenerator]]s, pressurizers, condensers[[Condenser (heat transfer)|condenser]]s, and feedwater pumps. The design would utilize only 1/6th of the nuclear concrete of a conventional light water reactor. <ref>{{cite news|url=https://www.wsj.com/articles/SB10001424052748703791504575079370538466574 | title=General Atomics Proposes a Plant That Runs on Nuclear Waste|last=Smith|first=Rebecca|date=Feb 22, 2010|work=[[The Wall Street Journal]]}}</ref>

Each module can be manufactured in either U.S. domestic or foreign facilities using replacement parts manufacturing and supply chain management with large components shipped by commercial truck or rail to a site for final assembly, where it will be fully enclosed in an underground containment structure. Dry cooling capability allows siting in locations without a source of cooling water.

If the reactor is to become part of a [[hydrogen economy]], the coolant outlet temperature of 850&nbsp;°C would allow the [[sulfur iodine cycle]] to be used which directly converts thermal energy into hydrogen (without electric or other intermediate steps) with an overall thermal efficiency around 50%.

==Nuclear waste==

EM2 can burn used [[nuclear fuel]], also referred to as “"[[spent fuel]]”" from current [[light water reactors]]. It can utilize an estimated 97% of unused fuel that current reactors leave behind as waste.

Spent fuel rods from conventional nuclear reactors are put into storage and considered to be [[nuclear waste]], by the nuclear industry and the general public.<ref>{{cite news|url=httphttps://articleswww.latimes.com/2010archives/la-xpm-2010-mar/-11/opinion/-la-le-thursday11-2010mar11/-story.html|title=Letter to the Editor in Response to "Nuclear power – not a green option – it generates radioactive waste; it requires uranium that's dangerous to mine; it's hugely expensive,"|last=Parmentola|first=John|date=March 11, 2010|work=[[Los Angeles Times]]}}</ref> Nuclear waste from light water reactors retains more than 95% of its original energy because such reactors cannot burn fertile U238, while fast reactors can. The current U.S. inventory of spent fuel is equivalent to nine trillion barrels of oil - four times more than the known reserves.

==Non-proliferation==

By using spent nuclear waste and depleted uranium stockpiles as its fuel source, a large-scale deployment of the EM2 could reduce the long-term need for uranium enrichment and eliminate conventional nuclear reprocessing, which requires plutonium separation.<ref>{{cite news|url=httphttps://spectrum.ieee.org/energy/nuclear/downsizing-nuclear-power-plants/|title=7. "Downsizing Nuclear Power Plants – Modular designs rely on ‘economies'economies of multiples’multiples' to make small reactors pay off big," |last=Fairley |first=Peter |date=May 11, 2010 |work=[[IEEE Spectrum]]}}</ref>

Conventional light water reactors require refueling every 18 months. EM2’s 30-year fuel cycle minimizes the need for fuel handling and reduces access to fuel material, thus reducing proliferation concerns.

Conventional light water reactors require refueling every 18 months. EM2’sEM2's 30-year fuel cycle minimizes the need for fuel handling and reduces access to fuel material, thus reducing proliferation concerns.

[[File:EM2-plant cross section.jpg|thumb|Cross-section of a two-unit EM2-based power plant.]]

==Nuclear safety and security==

EM2 utilizes passive safety systems designed to safely shutdown the reactor in emergency conditions using only gravity and natural convection.<ref>{{cite web|url=http://www.ga.com/advanced-reactors |title=Advanced Reactors |publisher=General Atomics |accessdateaccess-date = Feb 19, 2018}}</ref> Control rods are automatically inserted during a loss-of-power incident via gravity. Natural convection flow is used to cool the core during whole site loss of power incidents. No external water supply is necessary for emergency cooling. The use of silicon carbide as fuel cladding in the core ensures no hydrogen production during accident scenarios and allows an extended period of response when compared to Zircaloy metal cladding used in current reactors.

Underground siting improves safety and security of the plant against terrorism and other threats.

EM2’sEM2's high [[operating temperature]] can provide process heat for [[petrochemical]] fuel products and [[alternative fuels]], such as [[biofuels]] and [[hydrogen]].<ref>{{Cite web | title = Small Nuclear Power Reactors | url=http://www.world-nuclear.org/info/inf33.html | publisher=World Nuclear Association | date = August 2010 | access-date=2010-09-09 | archive-date=2013-02-12 | archive-url=https://web.archive.org/web/20130212224137/http://www.world-nuclear.org/info/inf33.html | url-status=dead }}</ref>

==See also==

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== External links ==

* {{official website|http://www.ga.com/nuclearadvanced-energy/energy-multiplier-modulereactors}}

* 2011-11-28: [https://web.archive.org/web/20130530133706/http://www.nuc.berkeley.edu/Colloquiums/2011-11-28 Presentation about the EM2 reactor at the Department of Nuclear Engineering, University of California-Berkeley], [https://web.archive.org/web/20150714102414/http://www.ustream.tv/recorded/18810437 ustream video] [https://web.archive.org/web/20130530143549/http://www.nuc.berkeley.edu/Colloquiums/2010-5-3 Previous presentation]

* 2015-05: [[Testimony]] of the Sr. Vice President of [[General Atomics]] before the [[Committee on Science, Space and Technology]]: [http://docs.house.gov/meetings/SY/SY20/20150513/103447/HHRG-114-SY20-Wstate-ParmentolaJ-20150513.pdf]