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The UNGG (Uranium Naturel Graphite Gaz) is an obsolete nuclear power reactor design developed in France. It was graphite moderated, cooled by carbon dioxide, and fueled with natural uranium metal. The first generation of French nuclear power stations were UNGGs, as was Vandellos unit 1 in Spain. Of the ten units built, all were shut down by the end of 1994, most for economic reasons due to staffing costs. A UNGG reactor is often simply referred to as an GCR in English documents.

Design

The UNGG is along with the Magnox the main type of gas cooled reactor (GCR). It was developed independently of and parallel to the British Magnox design, both to meet similar requirements of simultaneous production of electric power and plutonium. Although the French and the British models both used natural uranium and the same moderator and coolant, there were differences in design. In France, each next built reactor had a different design. The first UNGG reactors at Marcoule used horizontal fuel channels and a concrete containment structure.^[1] Chinon A1 used vertical fuel channels and a steel pressure-vessel.

The fuel cladding material was a magnesium-zirconium alloy in the UNGG, as opposed to magnesium-aluminium in Magnox. As both claddings react with water, they can be stored in a spent fuel pool only for short periods of time, making short-term reprocessing of fuel essential, which requires heavily shielded facilities.

The programme was a succession of units, with changes to the design increasing power output. In the experimental phase they were built by the Commissariat à l'Énergie Atomique (CEA), and later by Électricité de France (EDF).^[1] The largest UNGG reactor built was Bugey 1 with a net electrical output of 540 MW.

Units

G1, G2 and G3 at Marcoule. G1 was the first UNGG; a prototype for military use. G1 had a net output of 2 MWe and became critical in 1956.^[2]
Chinon Nuclear Power Plant A1, A2, and A3 in Indre-et-Loire.
Saint-Laurent Nuclear Power Plant A1 and A2 in Loir-et-Cher, operated from 1969 and 1971 to April 1990 and June 1992.
Reactor 1 at Bugey Nuclear Power Plant in Ain, the last UNGG built in France, first criticality 1972, closed in May 1994.
Vandellòs Nuclear Power Plant Unit 1 in Spain, the only UNGG built outside France, closed in July 1990.

The earlier units, at Chinon and Marcoule, had heat exchangers outside the main pressure vessel; Later units (Saint-Laurent, Bugey and Vandellos) moved these heat exchangers to inside the pressure vessel.

References

^ ^a ^b Ten Years of Nuclear Power. IAEA bulletin Vol. 6, no. 3, 1964. Via
^ Marcoule G1. INSC

French activities on gas cooled reactors, D Bastien, IAEA-TECDOC—899, pp:51-53, 30 Oct - 2 Nov 1995
Twenty-nine years of French experience in operating gas-cooled reactors, D Bastien, IWGGCR—19, pp:113-119 21-23 Sep 1988 Better copy archived

[iaea-10years-1] Ten Years of Nuclear Power. IAEA bulletin Vol. 6, no. 3, 1964. Via

[2] Marcoule G1. INSC

[1]

[2]

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+{{Short description|Type of nuclear reactor}}
 [[File:A1 A2 saint laurent.JPG|thumb|right|Two UNGG reactors at [[Saint-Laurent Nuclear Power Plant]]]]
-The '''UNGG''' (''Uranium Naturel Graphite Gaz'') is an obsolete [[nuclear power reactor]] design developed by France. It was [[graphite]] [[neutron moderator|moderated]], cooled by [[carbon dioxide]], and fueled with [[enriched uranium|natural uranium]] metal.
+The '''UNGG''' (''Uranium Naturel Graphite Gaz'') is an obsolete [[nuclear power reactor]] design developed in France. It was [[graphite]] [[neutron moderator|moderated]], cooled by [[carbon dioxide]], and fueled with [[natural uranium]] metal. The first generation of French nuclear power stations were UNGGs, as was [[Vandellos]] unit 1 in Spain. Of the ten units built, all were shut down by the end of 1994, most for economic reasons due to staffing costs. A UNGG reactor is often simply referred to as an ''GCR'' in English documents.
-It was developed independently of and in parallel to the British [[Magnox]] design, and to meet similar requirements. The main difference between the two designs is that UNGG used a horizontal fuel rod orientation, rather than the vertical orientation used in the Magnox reactor. The fuel cladding material was [[magnesium]]-[[zirconium]] alloy in the UNGG, as opposed to [[Magnox (alloy)|magnesium-aluminium]] in Magnox. As both claddings react with water, they can be stored in a [[spent fuel pool]] for short times only, making short-term [[nuclear reprocessing|reprocessing]] of the fuel essential, and requiring heavily shielded facilities for this.
+== Design ==
-The programme was a succession of units, with changes to the design increasing power output. In the experimental phase they were built by the [[Commissariat à l'Énergie Atomique]] (CEA), and later by [[Électricité de France]] (EDF).<ref name=UKAEA-10years>{{cite report |url=http://www.iaea.org/Publications/Magazines/Bulletin/Bull063/06304701725.pdf |title=Ten Years of Nuclear Power |publisher=UKAEA |year=1966 |accessdate=25 October 2013}}</ref>
+[[File:HD.15.075 (11839817825).jpg|thumb|Schematic of a UNGG reactor]]
+[[File:Section cartouche combustible UNGG Bugey.png|thumb|right|Cross section of UNGG fuel, showing internal cooling path]]
+The UNGG is along with the [[Magnox]] the main type of [[gas cooled reactor]] (GCR). It was developed independently of and parallel to the British Magnox design, both to meet similar requirements of simultaneous production of electric power and plutonium. Although the French and the British models both used natural uranium and the same moderator and coolant, there were differences in design. In France, each next built reactor had a different design. The first UNGG reactors at [[Marcoule]] used horizontal fuel channels and a concrete containment structure.<ref name=iaea-10years/> [[Chinon Nuclear Power Plant|Chinon]] A1 used vertical fuel channels and a steel pressure-vessel.
-The UNGG and the Magnox are the two main types of [[gas cooled reactor|GCR]]. A UNGG reactor is often referred to simply as a ''GCR'' in English documents, or sometimes loosely as a ''Magnox''.
+The fuel cladding material was a [[magnesium]]-[[zirconium]] alloy in the UNGG, as opposed to [[Magnox (alloy)|magnesium-aluminium]] in Magnox. As both claddings react with water, they can be stored in a [[spent fuel pool]] only for short periods of time, making short-term [[nuclear reprocessing|reprocessing]] of fuel essential, which requires heavily shielded facilities.
-The first generation of French nuclear power stations were UNGGs, as was [[Vandellos]] unit 1 in [[Spain]]. Of ten units built, all were shut down by end 1994, most for economic reasons due to staffing costs.  The largest was Bugey 1 with a net electrical output of 540 MW.
+The programme was a succession of units, with changes to the design increasing power output. In the experimental phase they were built by the [[Commissariat à l'Énergie Atomique]] (CEA), and later by [[Électricité de France]] (EDF).<ref name=iaea-10years>[http://www.iaea.org/sites/default/files/publications/magazines/bulletin/bull6-3/06304701725.pdf ''Ten Years of Nuclear Power'']. IAEA bulletin Vol. 6, no. 3, 1964. [https://www.iaea.org/bulletin/6-3 Via]</ref> The largest UNGG reactor built was Bugey 1 with a net electrical output of 540 MW.
 ==Units==
+* G1, G2 and G3 at [[Marcoule]]. G1 was the first UNGG; a prototype for military use. G1 had a net output of 2 MWe and became critical in 1956.<ref>[https://web.archive.org/web/20090507015112/http://www.insc.anl.gov/cgi-bin/sql_interface?view=rx_com_matrix&qvar=unit&qval=607 ''Marcoule G1'']. INSC</ref>
-[[File:Section cartouche combustible UNGG Bugey.png|thumb|right|Cross section of UNGG fuel, showing internal cooling path]]
-* G1, G2 and G3 at [[Marcoule]]. G1 was the first UNGG to go critical, in 1956.
 * [[Chinon Nuclear Power Plant]] A1, A2, and A3 in [[Indre-et-Loire]].
 * [[Saint-Laurent Nuclear Power Plant]] A1 and A2 in [[Loir-et-Cher]], operated from 1969 and 1971 to April 1990 and June 1992.
-* Reactor 1 at [[Bugey Nuclear Power Plant]] in [[Ain]], the last UNGG built in France, first criticality 1972, closed May 1994.
+* Reactor 1 at [[Bugey Nuclear Power Plant]] in [[Ain]], the last UNGG built in France, first criticality 1972, closed in May 1994.
-* [[Vandellòs Nuclear Power Plant]] Unit 1 in [[Spain]], the only UNGG built outside France, closed July 1990.
+* [[Vandellòs Nuclear Power Plant]] Unit 1 in Spain, the only UNGG built outside France, closed in July 1990.
 The earlier units, at Chinon and Marcoule, had heat exchangers outside the main pressure vessel; Later units (Saint-Laurent, Bugey and Vandellos) moved these heat exchangers to inside the pressure vessel.
 ==See also==
-* [[Gas cooled reactor]]
 * [[Nuclear power in France]]
+* [[Vandellòs I Nuclear Accident]]
 == References ==
 {{reflist}}
+* [https://inis.iaea.org/search/search.aspx?orig_q=RN:28008789 French activities on gas cooled reactors], D Bastien, IAEA-TECDOC—899, pp:51-53, 30 Oct - 2 Nov 1995
-== Sources and external links ==
+* [https://inis.iaea.org/search/search.aspx?orig_q=RN:20085902 Twenty-nine years of French experience in operating gas-cooled reactors], D Bastien, IWGGCR—19, pp:113-119 21-23 Sep 1988 [https://web.archive.org/web/20110604224413if_/http://www.iaea.org/inisnkm/nkm/aws/htgr/fulltext/iwggcr19_16.pdf Better copy archived]
-* [http://www.iaea.org/inisnkm/nkm/aws/htgr/abstracts/abst_28008789.html French activities on gas cooled reactors], D Bastien, IAEA-TECDOC—899, pp:51-53, 30 Oct - 2 Nov 1995
-* [http://www.iaea.org/inisnkm/nkm/aws/htgr/abstracts/abst_iwggcr19_16.html Twenty-nine years of French experience in operating gas-cooled reactors], D Bastien, IWGGCR—19, pp:113-119 21-23 Sep 1988
 {{Nuclear fission reactors}}
+{{Nuclear power in France}}
 [[Category:Graphite moderated reactors]]
 [[Category:Nuclear power reactor types]]
-{{nuclear-power-stub}}