Editing Experimental Breeder Reactor I (section)

==History==
EBR-I's construction started in late 1949. The reactor was designed and built by a team led by [[Walter Zinn]] at the Idaho site of the [[Argonne National Laboratory]],<ref name=osti>{{cite journal |url=https://www.osti.gov/servlets/purl/4115425 |title=Nuclear Reactors Built, Being Built, or Planned in the United States as of June 30, 1970 |publisher=U.S. Department of Energy, Office of Scientific and Technical Information |date=October 31, 1970|doi=10.2172/4115425 |doi-access=free }}</ref> known as Argonne-West (since 2005 part of [[Idaho National Laboratory]]). In its early stages, the reactor plant was referred to as [[Chicago Pile]] 4 (CP-4) and Zinn's Infernal Pile .<ref>[http://www.ne.anl.gov/About/hn/news960320.shtml Argonne’s Nuclear Science and Technology Legacy: Chicago Pile reactors create enduring research legacy] part of the Argonne National Laboratory Highlights in the period 1942–1949</ref> Installation of the reactor at EBR-I took place in early 1951 (the first reactor in Idaho) and it began power operation on August 24, 1951. On December 20 of that year, EBR-I produced electricity for its first time. The following day, the reactor produced enough power to light the whole building. The EBR-I produced 200 [[kilowatt|kW]] of electricity out of 1.4 [[megawatt|MW]] of [[heat]] generated by the reactor.<ref>{{Cite web |url=http://www.straipsniai.lt/en/Energetics/page/5238 |title=Nuclear energy for peace: the birth of nuclear energetics |access-date=July 21, 2009 |archive-url=https://web.archive.org/web/20110726164126/http://www.straipsniai.lt/en/Energetics/page/5238 |archive-date=July 26, 2011 |url-status=dead }}</ref>

The production of electricity at EBR-I is the first time that a reactor created in-house available electricity, and it is sometimes misreferred to as the first time that a nuclear reactor has ever created electricity, or powered a light bulb. However, the world's first electricity produced by a nuclear reactor occurred during an experiment 3 years earlier in September 1948 at the [[X-10 Graphite Reactor#Peacetime use|X-10 Graphite Reactor]] at the Oak Ridge National Lab in Tennessee. A small steam turbine allowed that reactor to power a single light bulb.<ref>{{cite web |last1=Garceau |first1=Gil |title=World's First Nuclear Power Generated Electricity from Jensen #50 on the X 10 Graphite Reactor 1948 |url=https://www.youtube.com/watch?v=FzAjO5_SyTU |website=YouTube |date=January 25, 2015 |access-date=4 April 2022}}</ref> Later in 1955, another nuclear milestone was reached when an experimental boiling water reactor plant called {{nowrap|[[BORAX]]-III}} (also designed, built, and operated by Argonne National Laboratory) was connected to external loads, powering the nearby city of [[Arco, Idaho]], the first time a city had been powered solely by nuclear power.<ref>{{cite web |url=http://www.ne.anl.gov/About/reactors/borax3/index.shtml |title=AEC Press release for BORAX-III lighting Arco, Idaho |publisher=U.S. Department of Energy, Argonne National Laboratory |year=1999 |access-date=July 26, 2012}}</ref> 

[[File:EBR-I - Core after 1955 incident.jpg|thumb|left|upright|Part of the core after the 1955 partial meltdown]]
The design purpose of EBR-I was not to produce electricity but instead to validate [[nuclear physics|nuclear physics theory]] that suggested that a [[breeder reactor]] should be possible. The concept suggested using a reactor's neutron radiation to convert or "breed" a blanket of [[fertile material]] into new fissile material. The reaction used in EBR-I's design was the breeding of uranium-238 into plutonium via [[fast neutrons]]:

<chem>{}^{238}_{92}U + {}^{1}_{0}n -> {}^{239}_{92}U ->[\beta^-][23.5\ \ce{min}] {}^{239}_{93}Np ->[\beta^-][2.356\ \ce{d}] {}^{239}_{94}Pu</chem>

This reaction had already been used in the [[X-10 Graphite Reactor]] and [[Hanford Site]] B, D, F, and DR reactors to produce plutonium for the [[Trinity (nuclear test)|Gadget]], [[Fat Man]], and further [[Pit (nuclear weapon)|pits]]. However, the Hanford reactors would only yield about 0.025% of fissile <sup>239</sup>Pu, from the fissile <sup>235</sup>U content of 0.7% in the natural uranium fuel slugs. This corresponds to a "conversion ratio" of 1/30.<ref name="t190">{{cite web |date=1944-09-26 |title=Science of the B Reactor at Hanford, Washington |url=https://www.nps.gov/teachers/classrooms/science-of-the-b-reactor-at-hanford-wa.htm |access-date=2024-12-24 |website=Teachers (U.S. National Park Service)}}</ref> The EBR-I design aimed to increase this by limiting neutron loss and maintaining a [[Fast-neutron reactor|fast spectrum]], achieving a ratio above one. In EBR-I, the ratio was experimentally calculated as:

<math>\text{conversion ratio} = \frac{\text{fissile atoms created}}{\text{fissile atoms destroyed}} = \frac{^{239}\text{Pu production}}{^{235}\text{U fission} \ + \ ^{236}\text{U production}}</math>

In 1956, an AEC report concluded a radiochemically measured conversion ratio of 1.00 ± 0.04, and a physically measured ratio of 1.01 ± 0.05, tentatively making it the world's first breeder reactor.<ref>{{cite web |last=Kadak |first=Prof. Andrew C. |title=Lecture 4, Fuel Depletion & Related Effects |url=http://www.learningace.com/doc/3103775/a22b70ccd4d6c2b95d5cc687c2e09c06/mit22_091s08_lec04 |url-status=dead |archive-url=https://web.archive.org/web/20151017114605/http://www.learningace.com/doc/3103775/a22b70ccd4d6c2b95d5cc687c2e09c06/mit22_091s08_lec04 |archive-date=17 October 2015 |access-date=24 December 2012 |work=Operational Reactor Safety 22.091/22.903 |publisher=Hemisphere, as referenced by MIT |page=Table 6–1, "Average Conversion or Breeding Ratios for Reference Reactor Systems"}}</ref><ref name="d686">{{cite book |last=Zinn |first=W.H. |url=https://books.google.com/books?id=6ij17HOBm1EC |title=Papers Presented at the Technical Briefing Session on the Boiling Water Reactor Program and the Fast Reactor Program Held at Idaho Falls, Idaho, November 1-2, 1955: (Unclassified) |author2=Argonne National Laboratory |publisher=U. S. Atomic Energy Commission, Technical Information Service Extension |year=1956 |page= |access-date=2024-12-24}}</ref>

On November 29, 1955, the reactor at EBR-I suffered a partial [[nuclear meltdown|meltdown]] during a coolant flow test. The flow test was trying to determine the cause of unexpected reactor responses to changes in coolant flow. It was subsequently repaired for further experiments, which determined that thermal expansion of the fuel rods and the thick plates supporting the fuel rods was the cause of the unexpected reactor response.<ref>The Story of the Borax Nuclear Reactor and the EBR-I Meltdown&nbsp;— Ray Haroldsen {{ISBN|978-1-56684-706-3}}</ref>

Besides being one of the world's first to generate plant electricity from atomic energy, EBR-I was also the world's first breeder reactor and the first to use [[plutonium]] fuel to generate electricity (see also the [[Clementine (nuclear reactor)|Clementine]] nuclear reactor). EBR-I's initial purpose was to prove [[Enrico Fermi|Enrico Fermi's]] fuel breeding principle, a principle that a nuclear reactor can produce more fuel atoms than it consumes. EBR-I proved this principle.<ref>{{cite web | url=https://www.asme.org/about-asme/who-we-are/engineering-history/landmarks/39-experimental-breeder-reactor-i | title=Experimental Breeder Reactor I | publisher=[[ASME]] | access-date=December 18, 2017}}</ref>

===Design===
[[File:Experimental Breeder Reactor I Cutaway diagram by Walter Zinn.png|left|thumb|Cutaway diagram of EBR-I, showing the core, inner blanket rods, coolant tank, and outer blanket and control rods.]]
As a breeder reactor, EBR-I used a "[[seed-and-blanket design]]". The core "seed" was [[highly enriched uranium]] at 90% uranium-235. The inner blanket contained rods of [[natural uranium]] at 0.7% uranium-235 content. This structure was surrounded by the double-walled tank containing the [[NaK]] primary coolant. This tank was surrounded by the air-cooled outer blanket of natural uranium, used for its effective [[Neutron reflector|neutron reflecting]] properties, and which also contained the [[Control rod|control rods]]. The outer blanket was the movable component, as technique for moving parts within liquid metal were in early stages. However the air-cooling greatly limited the maximum operating power, which was reached at 1.4 MWth.<ref name="d686" /><ref>{{cite web | url=https://www.asme.org/wwwasmeorg/media/resourcefiles/aboutasme/who%20we%20are/engineering%20history/landmarks/39-experimental-breeder-reactor-i-1951.pdf | title=Experimental Breeder Reactor I | publisher=[[ASME]] | access-date=October 28, 2019}}</ref>

The primary liquid metal coolant flows by gravity from the supply tank through the reactor core, where it absorbs heat. Then, the coolant flows to heat the exchanger, where it gives up this heat to the secondary coolant, another liquid metal. The primary coolant is returned to the supply tank by an electromagnetic pump. The secondary coolant is pumped to the boiler, where it gives up its heat to water, generating steam. This steam passes to the turbine, which is how electricity is produced. This steam then condenses and returned to the boiler by a water pump.<ref>{{Cite web |title=EBR-1 in Photos |url=https://www.ans.org/news/article-2096/ebr-1-in-photos/ |access-date=2024-01-13 |website=www.ans.org |language=en}}</ref>  This coolant design was shared by the later [[Dounreay Fast Reactor]] which first went [[Criticality (status)|critical]] in 1959.

===Decommission and legacy===
EBR-I was deactivated by Argonne in 1964 and replaced with a new reactor, [[Experimental Breeder Reactor II]].

It was declared a [[National Historic Landmark]] in 1965<ref name="nhlsum">{{cite web|url=http://tps.cr.nps.gov/nhl/detail.cfm?ResourceId=198&ResourceType=Building|title=Experimental Breeder Reactor No. 1|access-date=February 6, 2008|work=National Historic Landmark summary listing|publisher=National Park Service|archive-url=https://web.archive.org/web/20080110085743/http://tps.cr.nps.gov/nhl/detail.cfm?ResourceId=198&ResourceType=Building|archive-date=January 10, 2008|url-status=dead}}</ref><ref name="nrhpinv2">{{cite web|url={{NHLS url|id=66000307}}|work=National Register of Historic Places Inventory Nomination Form |title=Experimental Breeder Reactor #1|date=June 12, 1976 |format=PDF |author=Blanche Higgins Schroer |publisher=National Park Service |access-date=June 22, 2009}} and {{NHLS url|id=66000307|title=''Accompanying 4 photos, from 1975.''|photos=y}}&nbsp;{{small|(1.43&nbsp;MB)}}</ref> with its dedication ceremony held on August 25, 1966, led by President [[Lyndon Johnson]] and [[Glenn T. Seaborg]].<ref>{{cite web | url=https://www.inl.gov/article/experimental-breeder-reactor-i-opens-memorial-day-weekend-for-summer-tours/ | title=EBR-I now open to the public for tours | publisher=Idaho National Laboratory | date=May 26, 2016 | access-date=December 18, 2017}}</ref> It was also declared an [[List of IEEE milestones|IEEE Milestone]] in 2004.<ref>{{cite web |url=http://www.ieeeghn.org/wiki/index.php/Milestones:Experimental_Breeder_Reactor_I,_1951 |title=Milestones:Experimental Breeder Reactor I, 1951 |work=IEEE Global History Network |publisher=IEEE |access-date=August 3, 2011}}</ref>