Editing Tritium (section)

== Production ==

=== Lithium ===
Tritium is most often produced in [[nuclear reactor]]s by [[neutron activation]] of [[lithium-6]]. The release and diffusion of tritium and helium produced by the fission of lithium can take place within ceramics known as [[Breeding blanket|breeder ceramics]]. Production of tritium from lithium-6 in such breeder ceramics is possible with neutrons of any energy, though the cross section is higher when the incident neutrons have lower energy, reaching more than 900 [[barn (unit)|barn]]s for [[thermal neutron]]s. This is an [[exothermic]] reaction, yielding 4.8&nbsp;[[MeV]].<ref name="t-breeding">{{cite journal |last=Rubel |first=M. |title=Fusion neutrons: tritium breeding and impact on wall materials and components of diagnostic systems |date=2019 |journal= Journal of Fusion Energy |volume=38 |issue=3–4 |pages=315–329 |doi=10.1007/s10894-018-0182-1|s2cid=125723024 |doi-access=free |bibcode=2019JFuE...38..315R }}</ref> In comparison, [[Deuterium–tritium fusion|fusion of deuterium with tritium]] releases about 17.6&nbsp;MeV. For applications in proposed fusion energy reactors, such as [[ITER]], pebbles consisting of lithium bearing ceramics including Li{{sub|2}}TiO{{sub|3}} and Li{{sub|4}}SiO{{sub|4}}, are being developed for tritium breeding within a helium-cooled pebble bed, also known as a breeder blanket.<ref>
{{cite journal
 | last1 = Hanaor   | first1 = Dorian A.H.
 | last2 = Kolb     | first2 = Matthias H.H.
 | last3 = Gan      | first3 = Yixiang
 | last4 = Kamlah   | first4 = Marc
 | last5 = Knitter  | first5 = Regina
 | year = 2015
 | title = Solution based synthesis of mixed-phase materials in the Li{{sub|2}}TiO{{sub|3}}–Li{{sub|4}}SiO{{sub|4}} system
 | journal = Journal of Nuclear Materials
 | volume = 456  | pages = 151–161
 | doi = 10.1016/j.jnucmat.2014.09.028
 | arxiv = 1410.7128  | bibcode = 2015JNuM..456..151H
 | s2cid = 94426898
}}
</ref>

: {{nuclide|link=yes|lithium|6}} + [[Neutron|n]] → {{nuclide|link=yes|helium|4}} (2.05 MeV) + {{nuclide|hydrogen|3}} (2.75 MeV)

High-energy neutrons can also produce tritium from [[lithium-7]] in an [[endothermic]] reaction, consuming 2.466&nbsp;MeV. This was discovered when the 1954 [[Castle Bravo#High yield|Castle Bravo]] nuclear test produced an unexpectedly high yield.<ref name=ieer>
{{cite report
 |last=Zerriffi |first=Hisham
 |date=January 1996
 |title=Tritium: The environmental, health, budgetary, and strategic effects of the Department of Energy's decision to produce tritium
 |publisher=[[Institute for Energy and Environmental Research]]
 |url=http://www.ieer.org/reports/tritium.html#(11)
 |access-date=15 September 2010
}}
</ref> Prior to this test, it was incorrectly assumed that {{nuclide|lithium|7}} would absorb a neutron to become {{nuclide|lithium|8}}, which would beta-decay to {{nuclide|link=yes|beryllium|8}}, which in turn would decay to two {{nuclide|helium|4}} nuclei on a total timeframe much longer than the duration of the explosion.

: {{nuclide|link=yes|lithium|7}} + [[Neutron|n]] → {{nuclide|link=yes|helium|4}} + {{nuclide|hydrogen|3}} + [[Neutron|n]]

=== Boron ===
High-energy neutrons irradiating [[Boron#Enriched boron (boron-10)|boron-10]], also occasionally produce tritium:<ref>
{{cite journal
 | last = Jones  | first = Greg 
 | year = 2008
 | title = Tritium Issues in Commercial Pressurized Water Reactors
 | journal = Fusion Science and Technology
 | volume = 54  | issue = 2  | pages = 329–332
 | doi = 10.13182/FST08-A1824
 | bibcode = 2008FuST...54..329J 
 | s2cid = 117472371 
}}</ref>

: {{nuclide|link=yes|boron|10}} + n → 2 {{nuclide|helium|4}} + {{nuclide|hydrogen|3}}

A more common result of boron-10 neutron capture is {{sup|7}}Li and a single [[alpha particle]].<ref>
{{cite web
 | last = Sublette  | first = Carey 
 | date = 17 May 2006
 | title = Nuclear Weapons FAQ Section 12.0 Useful Tables
 | publisher = Nuclear Weapons Archive
 | url = http://nuclearweaponarchive.org/Nwfaq/Nfaq12.html
 | access-date = 19 September 2010
}}
</ref>

Especially in [[pressurized water reactor]]s which only partially [[thermal neutron|thermalize]] neutrons, the interaction between relatively fast neutrons and the [[boric acid]] added as a [[chemical shim]] produces small but non-negligible quantities of tritium.

=== Deuterium ===
{{See also|Heavy water#Tritium production}}
Tritium is also produced in [[Pressurized heavy-water reactor|heavy water-moderated reactor]]s whenever a [[deuterium]] nucleus captures a neutron. This reaction has a small absorption [[cross section (physics)|cross section]], making [[heavy water]] a good [[neutron moderator]], and relatively little tritium is produced. Even so, cleaning tritium from the moderator may be desirable after several years to reduce the risk of its escaping to the environment. [[Ontario Power Generation]]'s "Tritium Removal Facility" is capable of processing up to {{convert|2500|t}} of heavy water a year, and it separates out about {{convert|2.5|kg|abbr=on}} of tritium, making it available for other uses.<ref>
{{cite web
 | last = Whitlock  | first= Jeremy 
 | title = Section D: Safety and Liability – How does Ontario Power Generation manage tritium production in its CANDU moderators? 
 | publisher = Canadian Nuclear FAQ
 | url = http://www.nuclearfaq.ca/cnf_sectionD.htm#x5
 | access-date = 19 September 2010
}}
</ref>
[[CANDU reactor]]s typically produce {{convert|130|g}} of tritium per year, which is recovered at the Darlington Tritium Recovery Facility (DTRF) attached to the 3,512 MW{{sub|electric}} [[Darlington Nuclear Generating Station]] in Ontario. The total production at DTRF between 1989 and 2011 was {{convert|42.5|kg}} – with an activity of {{convert|409|MCi}}: an average of about {{convert|2|kg}} per year.<ref>{{cite journal |title=Tritium supply and use: a key issue for the development of nuclear fusion energy |first1= Richard J. |last1=Pearson |first2=Armando B. |last2=Antoniazzi |first3=William J. |last3=Nuttall |doi=10.1016/j.fusengdes.2018.04.090 |doi-access=free |journal=[[Fusion Engineering and Design]] |volume=136 |date=November 2018 |pages=1140–1148 |publisher=Elsevier|bibcode= 2018FusED.136.1140P }}</ref>

Deuterium's absorption cross section for [[thermal neutron]]s is about 0.52 [[barn (unit)|millibarn]], whereas that of [[oxygen-16]] ({{sup|16}}O) is about 0.19 millibarn and that of [[oxygen-17]] ({{sup|17}}O) is about 240 millibarns. While {{sup|16}}O is by far the most common [[isotope of oxygen]] in both natural oxygen and heavy water; depending on the method of [[isotope separation]], heavy water may be slightly richer in {{sup|17}}O and [[oxygen-18|{{sup|18}}O]]. Due to both [[neutron capture]] and (n,[[alpha particle|α]]) reactions (the latter of which produce [[carbon-14|{{sup|14}}C]], an undesirable long-lived beta emitter, from {{sup|17}}O) they are net "neutron consumers" and are thus undesirable in a moderator of a natural uranium reactor which needs to keep neutron absorption outside the fuel as low as feasible. Some facilities that remove tritium also remove (or at least reduce the content of) {{sup|17}}O and {{sup|18}}O, which can – at least in principle – be used for [[isotope labeling]].

India, which also has a large fleet of [[pressurized heavy water reactor]]s (initially CANDU technology but since indigenized and further developed [[IPHWR]] technology), also removes at least some of the tritium produced in the moderator/coolant of its reactors but due to the dual use nature of tritium and the Indian nuclear bomb program, less information about this is publicly available than for Canada.

=== Fission ===
Tritium is an uncommon product of the [[nuclear fission]] of [[uranium-235]], [[plutonium-239]], and [[uranium-233]], with a production of about one atom per 10{{sup|4}} fissions.<ref name=anl>
{{cite web
 |url         = http://www.ead.anl.gov/pub/doc/tritium.pdf
 |title       = Tritium (Hydrogen-3) – Human Health Fact sheet
 |date        = August 2005
 |access-date = 19 September 2010
 |publisher   = [[Argonne National Laboratory]]
 |archive-url = https://web.archive.org/web/20100208152633/http://www.ead.anl.gov/pub/doc/tritium.pdf
 |archive-date = 8 February 2010
 }}
</ref><ref>
{{cite conference
 | last1 = Serot    | first1 = O.
 | last2 = Wagemans | first2 = C.
 | last3 = Heyse    | first3 = J.
 | title = AIP Conference Proceedings
 | year = 2005
 | chapter = New results on helium and tritium gas production from ternary fission
 | conference = International Conference on Nuclear Data for Science and Technology
 | series = AIP Conference Proceedings
 | publisher = [[American Institute of Physics]]
 | volume = 769  | pages = 857–860
 | doi = 10.1063/1.1945141  | bibcode = 2005AIPC..769..857S
}}</ref> The main pathways of tritium production include [[ternary fission]]. The release or recovery of tritium needs to be considered in the operation of [[nuclear reactor]]s, especially in the [[nuclear reprocessing|reprocessing of nuclear fuel]] and storage of [[spent nuclear fuel]]. The production of tritium is not a goal, but a side-effect. It is discharged to the atmosphere in small quantities by some nuclear power plants.<ref name="National Academies Press">
{{cite book
 |title=Effluent Releases from Nuclear Power Plants and Fuel-Cycle Facilities
 |date=29 March 2012
 |publisher=National Academies Press (US)
 |language=en
 |url=https://www.ncbi.nlm.nih.gov/books/NBK201991/
}}
</ref> [[Nuclear reprocessing#Voloxidation|Voloxidation]] is an optional additional step in nuclear reprocessing that removes volatile fission products (such as all isotopes of hydrogen) before an aqueous process begins. This would in principle enable economic recovery of the produced tritium but even if the tritium is only disposed and not used, it has the potential to reduce tritium contamination in the water used, reducing radioactivity released when the water is discharged since [[tritiated water]] cannot be removed from "ordinary" water except by isotope separation.
{{Annual discharge of tritium from nuclear facilities}}
Given the [[specific activity]] of tritium at {{convert|9650|Ci/g|TBq/g}}, one [[Becquerel|TBq]] is equivalent to roughly {{convert|2.8|mg}}.

==== Fukushima Daiichi ====
{{main|Fukushima disaster cleanup}}
In June 2016 the Tritiated Water Task Force released a report<ref name=TWTFR>
{{cite report 
 |title=Tritiated Water Task Force Report
 |website=www.meti.go.jp/english  |lang=en
 |publisher=Ministry of Economy, Trade and Industry
 |place=Tokyo, Japan
 |url=http://www.meti.go.jp/english/earthquake/nuclear/decommissioning/pdf/20160915_01a.pdf
}}
</ref> on the status of tritium in tritiated water at [[Fukushima Daiichi nuclear disaster|Fukushima Daiichi nuclear plant]], as part of considering options for final disposal of the stored contaminated cooling water. This identified that the March 2016 holding of tritium on-site was 760&nbsp;[[Becquerel|TBq]] (equivalent to 2.1&nbsp;g of tritium or 14&nbsp;mL of pure tritiated water) in a total of 860,000&nbsp;m{{sup|3}} of stored water. This report also identified the reducing concentration of tritium in the water extracted from the buildings etc. for storage, seeing a factor of ten decrease over the five years considered (2011–2016), 3.3&nbsp;MBq/L to 0.3&nbsp;MBq/L (after correction for the 5% annual decay of tritium).

According to a report by an expert panel considering the best approach to dealing with this issue, "[[Heavy water#Production|Tritium could be separated theoretically]], but there is no practical separation technology on an industrial scale. Accordingly, a controlled environmental release is said to be the best way to treat low-tritium-concentration water."<ref>
{{cite web
 |title=JP Gov "No drastic technology to remove Tritium was found in internationally collected knowledge"
 |date=December 2013
 |website=Fukushima Diary
 |url=http://fukushima-diary.com/2013/12/jp-gov-no-drastic-technology-to-remove-tritium-was-found-in-internationally-collected-knowledge/
}}
</ref> After a public information campaign sponsored by the Japanese government, the gradual release into the sea of the tritiated water began on 24 August 2023 and is the first of four releases through March 2024.<ref>{{Cite news |date=2023-08-26 |title=The science behind the Fukushima waste water release |language=en-GB |url=https://www.bbc.com/news/world-asia-66610977 |access-date=2023-12-19}}</ref> The entire process will take "decades" to complete.<ref>{{cite news |last1=McCurry |first1=Justin |title=Rosy-cheeked face of tritium dropped from Fukushima's publicity drive |work=[[the Guardian]] |date=16 April 2021 |page=29}}</ref> China reacted with protest.<ref>{{cite news| url = https://www.washingtonpost.com/world/2021/04/14/china-japan-fukushima-water-drink/| title = China to Japanese official: If treated radioactive water from Fukushima is safe, 'please drink it' - The Washington Post| newspaper = [[The Washington Post]]}}</ref><ref>{{Cite web|url=https://thediplomat.com/2021/04/japan-faces-growing-pressure-to-rethink-releasing-fukushimas-wastewater-into-ocean/|title = Japan Faces Growing Pressure to Rethink Releasing Fukushima's Wastewater into Ocean}}</ref>
The IAEA has endorsed the plan. The water released is diluted to reduce the tritium concentration to less than 1500 Bq/L, far below the limit recommended in drinking water by the WHO.<ref>{{Cite web|url=https://www.scmp.com/news/china/diplomacy/article/3129412/why-japan-going-dump-radioactive-water-fukushima-nuclear-plant|title=Why is Japan dumping radioactive water at sea?|date=13 April 2021}}</ref>

=== Helium-3 ===
Tritium's [[decay product]] [[helium-3]] has a very large cross section (5330 barns) for reacting with [[Neutron temperature#Thermal|thermal neutrons]], expelling a proton; hence, it is rapidly converted back to tritium in [[nuclear reactor]]s.<ref>
{{cite web
 |title=Helium-3 neutron proportional counters
 |website=mit.edu
 |publisher=Massachusetts Institute of Technology
 |place=Cambridge, MA
 |url=http://web.mit.edu/8.13/www/tgm-neutron-detectors.pdf
 |archive-url=https://web.archive.org/web/20041121073851/http://web.mit.edu/8.13/www/tgm-neutron-detectors.pdf
 |archive-date=21 November 2004
}}
</ref>
: {{nuclide|link=yes|helium|3}} + n → {{nuclide|hydrogen|1}} + {{nuclide|hydrogen|3}}

=== Cosmic rays ===
Tritium occurs naturally due to [[cosmic ray]]s interacting with atmospheric gases. In the most important reaction for natural production, a [[Neutron temperature#Fast|fast neutron]] (which must have energy greater than 4.0&nbsp;[[Electronvolt|MeV]]<ref>
{{cite web
 | last1 = Young  | first1 = P.G.
 | last2 = Foster | first2 = D.G. Jr.
 | date = September 1972
 | name-list-style = amp
 | title = An evaluation of the neutron and gamma-ray production cross-sections for nitrogen
 | publisher = [[Los Alamos Scientific Laboratory]]
 | place =  [[Los Alamos, NM]]
 | url = https://fas.org/sgp/othergov/doe/lanl/lib-www/la-pubs/00320217.pdf
 | access-date= 19 September 2010
}}
</ref>) interacts with atmospheric [[nitrogen]]:
: {{nuclide|link=yes|nitrogen|14}} + n → {{nuclide|link=yes|carbon|12}} + {{nuclide|hydrogen|3}}

Worldwide, the production of tritium from natural sources is 148&nbsp;peta[[becquerel]]s per year. The global equilibrium inventory of tritium created by natural sources remains approximately constant at 2,590&nbsp;petabecquerels. This is due to a fixed production rate, and losses proportional to the inventory.<ref name=physics.isu.edu-RIN-Tritium>
{{cite web
 |title=Tritium information section
 |series=Radiation Information Network 
 |department=Physics Department
 |publisher=Idaho State University
 |url=http://www.physics.isu.edu/radinf/tritium.htm
 |archive-url=https://web.archive.org/web/20160303184224/http://www.physics.isu.edu/radinf/tritium.htm
 |archive-date=3 March 2016
}}</ref>

===Production history===
==== USA ====
Tritium for American [[nuclear weapon]]s was produced in special [[heavy water reactor]]s at the [[Savannah River Site]] until their closures in 1988. With the [[START I|Strategic Arms Reduction Treaty]] (START) after the end of the [[Cold War]], the existing supplies were sufficient for the new, smaller number of nuclear weapons for some time.

{{convert|225|kg|abbr=on}} of tritium was produced in the United States from 1955 to 1996.{{efn|Total U.S. tritium production since 1955 has been about 225&nbsp;kilograms, an estimated 150&nbsp;kilograms of which have decayed into helium-3, leaving a current inventory of about 75&nbsp;kg of tritium. — Zerriffi & Scoville (1996)<ref name="IEER Production">
{{cite web
 |last1=Zerriffi |first1=Hisham
 |last2=Scoville |first2=Herbert Jr.
 |date=January 1996
 |title=Tritium: The environmental, health, budgetary, and strategic effects of the Department of Energy's decision to produce tritium
 |page=5  |language=en
 |publisher=[[Institute for Energy and Environmental Research]]
 |url=http://www.ieer.org/wp/wp-content/uploads/downloads/2012/05/Tritium_1996_Zerriffi.pdf
 |access-date=6 September 2018
 |archive-url=https://web.archive.org/web/20141016031739/http://www.ieer.org/wp/wp-content/uploads/downloads/2012/05/Tritium_1996_Zerriffi.pdf
 |archive-date=16 October 2014
}}
</ref>}} Since it continually decays into helium-3, the total amount remaining was about {{convert|75|kg|abbr=on}} at the time of the report,<ref name="IEER Production" /><ref name=ieer/>
and about {{convert|16|kg|abbr=on}} as of 2023.<ref>27 years have passed since 1996, i.e. 2.25 half-lives, which reduce the 75kg of 1996 to 75/2^(2.25) ≈15.8 kg.</ref>

Tritium production was resumed with [[irradiation]] of rods containing [[lithium]] (replacing the usual [[control rod]]s containing [[boron]], [[cadmium]], or [[hafnium]]), at the reactors of the commercial [[Watts Bar Nuclear Plant]] from 2003 to 2005 followed by extraction of tritium from the rods at the Tritium Extraction Facility at the [[Savannah River Site]] beginning in November 2006.<ref>
{{cite web
 | title=Defense Programs
 | department = [[Savannah River Site]]
 | publisher = U.S. Department of Energy
 | url=http://www.srs.gov/general/programs/dp/index.htm
 | access-date=20 March 2013
}}
</ref><ref>
{{cite web
 | title = Tritium Extraction Facility
 | series = Factsheets
 | date = December 2007
 | department = [[Savannah River Site]]
 | publisher = U.S. Department of Energy
 | url = http://www.srs.gov/general/news/factsheets/tef.pdf
 | access-date = 19 September 2010
}}
</ref> Tritium leakage from the rods during reactor operations limits the number that can be used in any reactor without exceeding the maximum allowed tritium levels in the coolant.<ref>
{{cite press release
 |last=Horner |first=Daniel
 |date=November 2010
 |title=GAO finds problems in tritium production
 |website=Arms Control Today
 |url=http://www.armscontrol.org/act/2010_11/GAOTritium 
}}
</ref>