Abstract
Located in the vessel, the reactor core is the seat of nuclear fission reactions and, as such, the essential component of a nuclear reactor. The heat produced, due to the high power levels encountered (of the order of 3000–4000 MWth), leads to heat fluxes of the order of 60 W/cm2 which heat water thanks to exchange coefficients of the order of 20,000 W/m2/K. The water flows significantly into the core (approx. 70,000 m3/h, hence 13,000 kg/s) for a Courant number of about 13, and a ratio between heat exchange and convection of about 0.15. The water flows at about 4 m/s in the core. The temperature of the rods reaches more than 1000 °C in the center of the fuel rods and the water pressure is about 155 bars. These few figures show that the core is subject to very strong thermal, mechanical and chemical constraints (additives in the water, corrosion, etc.).
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Notes
- 1.
Westinghouse reports that between 2000 and 2006, 38% of their fuel leakage causes were debris, 29% were fretting, 8% were Pellet Cladding Interaction problems, 10% were manufacturing problems, and the rest were not inspected (source: Marie Blanc: Les aspects industriels, matériaux, méthode de conception, qualité de fabrication, Revue Générale Nucléaire no. 2, Mars 2008, pp. 38–43). It should also be noted that about 20% of the fuel loaded in France is of Westinghouse origin, the rest being produced by Framatome.
- 2.
Laurent Stricker: Le combustible usé à EDF, Contrôle no. 117, Juin 1997.
- 3.
Density of fuel 10,412, or 95% of the theoretical density of 10.96.
- 4.
Density of cladding: 6.55, zirconium alloyed with 1.5% tin, 0.2% iron and 0.1% chromium.
- 5.
Density of Inconel: 8,2.
- 6.
Density of 304 steel: 7,9.
- 7.
On the properties of uranium oxide: [Samsonov, 1982], on uranium mining: [Blazy, 1979].
- 8.
Jean-Louis Nigon, Michel Ponticq, Michel Watteau: L’acquisition des connaissances sur le combustible REP en France, Revue Générale Nucléaire no. 2 mars 2008, pp. 21–26.
- 9.
A very complete description of the Romans unit can be found in the October 1979 issue of Delta Information, in particular the article by A. Elkouby, Director of the Framatome Fuel Division, and G. Moneyron, General Manager of FBFC.
Delta information, October 1979.
- 10.
The initial capital of FBFC was 60% for Eurofuel, 24% for the Compagnie Belge Métallurgie et Mécaniques (MMN) and 16% for Westinghouse. Eurofuel was a European PWRs fuel manufacturing company created in December 1972, with 51% for Péchiney-Ugine-Kuhlmann, 35% for Westinghouse, 11% for Framatome and 3% for Creusot-Loire.
- 11.
51% for Péchiney-Ugine-Kuhlmann and 49% for Framatome.
- 12.
L’industrie nucléaire française, Commissariat à l’énergie atomique, 1980. This 208-page booklet contains an important source of information on all stages of the fuel cycle from mine to waste.
- 13.
Zirconium was discovered in 1789 by the chemist Martin Heinrich Klaproth (1743–1817) from zircon, and isolated by the Swedish chemist Jöns Jacob Berzelius (1779–1848). The general properties of zirconium are as follows: atomic mass: 91.22 g/mol; phase change α (hexagonal compact) -> β (cubic centered): 865 °C; melting 1850 °C; boiling: 3577 °C; density: 6.53 g/cm3; thermal conductivity: 0.049 cal/cm/s/°C; heat capacity: 0.066 cal/g/°C; breaking load at 25 °C: 200 MPa; yield strength 100 MPa; capture cross section at 2200 m/s: 0.185 barn. In 1952, it was accidentally discovered that the addition of a small quantity of stainless steel considerably improved the resistance of zirconium to corrosion by water: the mixture was called zircaloy. Successive improvements lead to the creation of zircaloy-4, then M5 alloy (addition of tin and niobium to improve mechanical and corrosion properties). The mechanical properties of zirconium are highly anisotropic, and the properties of the alloy will therefore depend on its thermomechanical history (from melting to the finished product), thus marking a strong heredity.
- 14.
For more details on 2G: Philippe Clergue, Jacques Dodelier, Joël Jouan: L’AFA 2G, un assemblage pour une plus grande souplesse d’exploitation, Revue Générale Nucléaire no. 4, Juillet-Août 1992, pp. 324–331, in French and in English.
- 15.
On the physics of deformation of assemblies, see [Olander, 1976], p. 566, which deals (already!) with the problem in a whole chapter.
- 16.
On niobium, lire [Quarrell, 1961], in particular on oxidation p. 181.
- 17.
P. Blanpain, G. Masuy, J.C. Peyran, G. Ravier: The Framatome PWR fuel, Revue Générale Nucléaire International edition, Vol. B, December 1997, pp. 18–21.
- 18.
On the properties of plutonium oxide: [Samsonov, 1982].
- 19.
On the properties of zirconium, read especially [Elinson and Petrov, 1969] and [Cailletaud and Lemoine, 1982].
- 20.
Martin Heinrich Klaproth (1743–1817): Born in Wernigerode and died in Berlin, Klaproth was the second of three brothers. His father lost all his money in a fire in 1751 and he had to provide for his education at an early age, which he always considered incomplete. At the age of 16, he decided to become an apothecary, a profession that he learned in Quedlinburg. From 1766 to 1768, he worked in the public laboratory in Hanover, then became an assistant in Wendland’s laboratory. In 1770, he became an assistant in Danzig, and then returned the following year to Berlin where he became the assistant of Valentin Rose, a well-known German chemist. When Rose died in 1771, Klaproth took over the management of his laboratory. He also became a father to Rose’s two sons, one of whom studied medicine. Klaproth defended a thesis “On phosphorus and distilled water” printed in Berlin in 1782, then bought the Flemming laboratory in Spandau Street. He married Sophia Chritiana Lehman and had three daughters and a son. He published a multitude of essays in the scientific journals of his time: Köhler’s journal, Selle’s contributions to natural sciences and medicine, which made him one of the first analytical chemists. He is credited with works on ammonia, tungsten, but he also discovered zirconium, which is highly used in the nuclear industry, chromium and cerium. In 1788, he became an ordinary member of the Berlin Academy of Sciences. In 1795, he published all of his work under the title “Contribution à la connaissance chimique des minéraux”, of which 6 volumes were published by 1815. Then a seventh volume including scattered essays and an index of the previous works. He supervised a new edition corrected by him of the manual of chemistry of Gren. Klaproth introduced into the analysis of hard minerals the use of caustic alkali attack in silver crucibles. He also introduced the use of barytes for the analysis of minerals that already contained alkalis and were therefore not detectable by alkaline etching. These two methods allowed very precise compositional measurements of less than one hundredth. He selected precisely the instruments (vessels, basins, coils…) used to contain the mixtures, noting their induced effects on the measurements. Klaproth was a follower of the principles of the French chemist Claude-Louis Berthollet (1748–1822). He became a corresponding member of many Academies of Sciences, such as Paris, London, St. Petersburg, Stockholm, Copenhagen and Munich, and received from the King of Prussia the order of the Red Eagle of third class in 1811 to distinguish his work. He taught chemistry to the officers of the Royal Artillery Corps, as a professor at the Tempelhof Artillery Academy, then at the Royal War School. Finally, he was professor of chemistry at the University of Berlin. Klaproth worked to enlighten the Freemasonry movement of which he was a member, in order to avoid the alchemical errors and other affabulations that had crept into the movement. According to M. Ficher’s memoir of the life of Klaproth, the Edinburgh philosophical journal, Volume 5, Part 2, no. 10, pp. 319–334, October 1821.
- 21.
Jöns Jacob Berzelius (1779–1848) is a Swedish chemist who studied both medicine and chemistry. He carried out numerous analytical experiments in chemistry. He discovered cerium in 1807 with Hisinger, selenium in 1817 with Johan Gottlieb Gahn, and thorium in 1829. He isolated zirconium in 1824.
Jöns Jacob Berzelius painted by Johan Sandberg.
- 22.
Clifford Frondel: Zirconium: Mineralogy and Geochemistry, 2nd Nuclear Engineering and science Conference, March 11–14, 1957, Philadelphia, USA, published by the American Society of Mechanical Engineers, New York, 1957.
- 23.
Frederick Forscher: Effect of cold work on the mechanical properties of Zircaloy-2, 2nd Nuclear Engineering and science Conference, March 11–14, 1957, Philadelphia, USA, published by the American Society of Mechanical Engineers, New-York, 1957.
- 24.
Jean-Louis Nigon, Michel Ponticq, Michel Watteau, J.P. Robin: Les produits combustibles dans les REP EDF: origines, évolutions et progrès apportés, Revue Générale Nucléaire no. 2, mars 2008, pp. 27–31.
- 25.
Jacques Decours: Le zirconium, vertus et défauts, Clefs no. 17, Revue scientifique du CEA, Automne 1989, pp. 17–27.
- 26.
J. Thomazet: Prévention de la corrosion des gaines de zircaloy, Corrosion et métallurgie des matériaux nucléaires, INSTN, session de formation, 1996.
- 27.
J. Thomazet: Amélioration de la résistance à la corrosion du gainage Zircaloy 4: de l’AFA à l’AFA 2G, Corrosion et métallurgie des matériaux nucléaires, INSTN, session de formation, 1996.
- 28.
J. Joseph, D. Magnin, F. Obadia, V. Rebeyrolle: Le zirconium au cœur de la conception de l’assemblage nucléaire, Revue Générale Nucléaire no. 3, Mai-Juin 1992, La filière française du zirconium.
- 29.
From a Pechiney Ugine Kulhmann chemical plant that produced ammonia in Paimboeuf, Pechiney (51% of the shares) and Framatome (49%) joined forces in 1978 to create Zircotube, a zirconium tube plant, and bought the patent in the USA. They went to see the Westinghouse plant that existed in Blairsville, Pennsylvania (USA), and decided to improve it in Paimboeuf. The first director was Paul Quinton, who had built steel mills in Fos-sur-Mer, and Jean-Yves Gasnier supervised the construction of the new plant on site. Once the personnel had been trained by the original American manufacturer, the plant produced its first tube after one year, a record that astounded the Americans. The plant became Cezus, then Areva and finally Framatome, and today produces more than 8200 km of zircaloy tube per year. (Adapted from the newspaper Ouest-France).
- 30.
On aluminum and its alloys, read [Vargel, 1979]. Aluminum is a light metal (density 2.7), which resists well to atmospheric corrosion.
- 31.
Jean-Dominique Barbat: Le concepteur et le producteur d’alliages, Revue Générale Nucléaire no. 3, Mai-Juin 1992, La filière française du zirconium.
- 32.
G.L. Graner, J.P. Mardon, I.G. Mensah: Performance of Alloy M5 cladding and structure at burnups beyond the current licensing limit in U.S. reactors, Revue Générale Nucléaire no. 6, novembre 2007, pp. 80–83.
- 33.
On the properties of zirconium oxide: [Samsonov, 1982].
- 34.
In nucleate boiling, the cladding/fluid wall exchange coefficient increases considerably and improves the cladding-fluid exchange. Of course, it is necessary to keep a significant margin with respect to the critical flux.
- 35.
J.M. Shallenberg, J.F. Wilson, R.P. Knotte: PWR fuel features to preclude externally induced damage, Transactions for the American Nuclear Society, Supplement no.1 to volume 54, 1987, pp. 160–161.
- 36.
Miguel Aullo, David Charpin, Philippe Bellanger; European Fuel Group—Combustible pour réacteur à eau pressurisée. Expérience et évolution du produit, Revue Générale Nucléaire no. 4, Juillet-Août 2006, pp. 55–58.
- 37.
An Inter-Regional Storage Facility (MIR for Magasin Inter-Régional) for new fuel for the French fleet reactors is located at the Bugey nuclear site, and another at the Chinon site. The MIR at the Bugey site was authorized by the decree of June 15, 1978. This installation includes a storage area with a capacity of 320 fuel assemblies, a handling hall, and all the related premises and equipment. It can store fresh fuel assemblies enriched in uranium 235 to 3.5%. This enrichment rate was raised to 5.0% by the decree of 4 June 1998. This decree also specifies that this MIR cannot store fuel assemblies enriched in plutonium oxide (MOX) or in reprocessed uranium (URT), as well as incomplete fuel assemblies. The main problem with the MIR is the risk of untimely criticality if the assemblies are too close together. This risk is eliminated by a geometrical storage on patterns with a very wide dry air lattice gap.
MIR of Bugey.
- 38.
M. Le Bars, J.C. Barral, J.L. Provost: Trente ans de combustible REP à EDF: fiabilité et retour d’expérience, évolution des performances et gestions au service du parc nucléaire, Revue Générale Nucléaire no. 2, Mars 2008, pp. 44–51.
- 39.
One has the urge to say “l’hafnium” in French, but you have to say “le hafnium” and mark the aspirated h.
- 40.
Silver is a relatively rare metal and has been known since ancient times (manufacture of jewelry and coins thanks to its strong ductility and a certain resistance to oxidation). With a density of 10.5, it has two stable isotopes, silver 107 (51.84%) and silver 109 (48.16%), both showing strong neutron resonances from about 10 eV. Its price is about 400 Euros per kilogram.
- 41.
Indium is a rare and therefore expensive metal with two natural isotopes, indium 113 (4.3%) and indium 115 (95.7%), the main neutron absorber. It was discovered in 1863 by Reich and Richter in sphalerite. The indigo blue color of its characteristic line gave it its name. With a density of 7.31, indium melts at a relatively low temperature of 156 °C and boils at 2046 °C. Pure indium cannot therefore be used unalloyed at the nominal temperature of PWRs (306 °C), in addition to the fact that it is a very expensive product. Indium is also used in lubrication, in the manufacture of gaskets and has a high cross-section to thermal neutrons, hence its role in control rods. The two isotopes of indium show strong resonances from 2 eV. Its price is about 800 Euros per kilogram, due to an increased demand in the flat screen industry.
- 42.
Cadmium is a relatively abundant metal, discovered by the Swedish chemist Magnus Martin Pontin in 1809, although it has been used since antiquity. With a density of 8.69, it has 6 stable isotopes 106 (1.25%), 108 (0.89%), 110 (12.49%), 111 (12.80%), 112 (24.13%), 114 (28.73). The 113 isotope is radioactive (12.26% of natural cadmium), as is the 116 (7.49%), but with a period greater than the age of the Universe! Cadmium 113 is by far the most absorbing isotope of cadmium with a single giant resonance at 0.17 eV (62,913 barns) and a capture cross-section of 20,718 barns at 0.0253 eV. Natural cadmium melts at 321 °C and boils at 767 °C. Its price is about 8 Euros per kilogram. Cadmium has been used in the nuclear industry as a thermal neutron absorber since Enrico Fermi.
- 43.
Kazuto Sawaragi, Masaru Tanigushi, Yoshihisa Tada, Masaki Kurokawa, Yasuo Araki: Development of inspection technique for CDRM housing Canopy seals, Proceedings of the first international conference on NDE in relation to structural integrity for nuclear and pressurized components, 20–22 October 1998, Amsterdam, volume 1, EUR 18,674 EN, pp. 396–405, Woodhead Publishing Ltd.
- 44.
From the EPR onwards, the pitch of a spline decreases to 1 cm and abandons the Anglo-Saxon units.
- 45.
Marc Zbinden, Agnès Lina: L’usure dans les réacteurs à eau pressurisée : le cas des grappes de commande, EPURE no. 63, Juillet 1999, pp. 15–29.
- 46.
The removal of a control rod drive mechanism is a relatively high dosing procedure, with an estimated dose of 100 mSv at contact for disassembly.
- 47.
The company Böhler, which produces this V721 grade, states on its website Ultra-high-strength steel, suitable for martensitic hardening (“marageing”), which achieves its high-strength properties compared to harden steels not by a hardening structure with a relatively high carbon content, but by precipitation of intermetallic phases from a virtually carbon-free nickel martensitic base mass. This results in the following advantages: High tensile strength and yield strength, good toughness (even at low temperatures), high resistance to notch tensile strength and heatup cracking, virtually no dimensional change during heat treatment, no decarburization or risk of cracking, core hardening even with large dimensions, good chip removal in the hardened state, good cold forming ability due to low hardening tendency, good weldability, simple heat treatment at low temperatures. The tubes are hyper-quenched to a yield strength of 50–100%. 70 kg/mm2.
- 48.
On 11 March 1999, when the Tricastin-1 plant was in shutdown condition for a ten-yearly inspection and the fuel was unloaded, a technician wrongly thought to do the right thing by removing two spotlights placed in the vessel pit, even though it was in the red zone. This intervention cost him an exposure of 340 mSv, whereas the annual dose is limited to 50 mSv (event classified level 2 by the Safety Authority).
- 49.
These sensors are normally intended for monitoring migrating bodies and vibrations of internals (KIR system). Provisional Metravib sensors were also mounted upstream of the KIR sensors at identical positions (on the bent part of the teleflex guide) to those mounted on the CPY for inter-comparison. These measurement cycles showed that finger tube shocks their guide tubes (shocks of the order of 1 g of acceleration (i.e. 9.81 m/s2) for shocks up to 11 g) from the RIC room using the accelerometers, but even with a stethoscope whose bell is directly applied to the tube.
- 50.
COCCINELLE at EDF.
- 51.
G. Mitelhan, R. S. Erofeev, N. D. Rozenblyum: Transformation of the Energy of short-lived radioactive isotopes, Soviet Journal of Atomic Energy 10, no. 1 (1961).
- 52.
J. W. Hilborn: “Self-Powered Neutron Detectors for flux monitoring”, Nucleonics 22, 2, 69 (1964).
- 53.
J. W. Hilborn, “Self-Powered Neutron Detector”, U.S. Patent 3, 375, 370 (March 26, 1968).
- 54.
M. Grin: Collectrons, Self-powered neuron flux detectors, Part 1: Theoretical considerations, Rapport EUR 4775 e, Commission of the European Communities, 37 p. (1972).
- 55.
On the subject of the Golfech 2 test, Gilles Sardier’s paper is worth reading: « Unité de surveillance 3D en ligne et instrumentation interne fixe, étude des performances des collectrons au rhodium», mémoire de CNAM, 27 octobre 2000.
- 56.
On thermocouple technology, read with interest [Asch and al, 2006], p. 231.
- 57.
The thermoelectric couple used is the Chromel–Alumel couple (Nickel Chrome/Nickel alloy type K) cladded with stainless steel (Z2 CND 17 12/ 316L, diameter 3.17 mm, thickness 0.4 mm) and insulated with alumina, whose accuracy is ± 1.5 °C between 0 and 375 °C and ±0.4% from 375 to 1200 °C, where they undergo irremediable degradation. Resistance thermometers are used for cold junction corrections. Thermocouple cladding is manufactured by THERMOCOAX or Câbles de Lyon. The connectors are THERMOELECTRIC and then LEMO for the CP0/CPY, and Deutsch for the 1300 MWe standardized plant.
- 58.
Patrick Erhard, personal communication, 2009.
- 59.
The introduction of MOX required the addition of 4 control rod clusters and an increase in the boron concentration of the REA tank and PTR tank.
- 60.
In simplified terms, the ant colony method is based on the idea of ants searching for food and facing several paths. On the way to and from their search, the ants leave a certain amount of scent pheromone on the path. If the path is longer, this pheromone evaporates more, and the following ants preferentially choose the path with the most powerful pheromone (but not systematically as to leave themselves the possibility to explore new and faster paths). In this case, the evaporation rate of the pheromone is a major parameter to set to be efficient.
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Marguet, S. (2022). The Core, the Fuel and the Instrumentation. In: The Technology of Pressurized Water Reactors. Springer, Cham. https://doi.org/10.1007/978-3-030-86638-9_5
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