TERMIUM Plus®

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FUEL PEBBLE [1 record]

Record 1 2017-04-13

English

Subject field(s)
  • Nuclear Fission Reactors
CONT

In the most common type of high temperature reactor (HTR) fuel, tiny particles of nuclear fuel are coated with three or four layers of coatings which are impenetrable to fission products up to a temperature of 2000 celsius. About 20,000 particles, bonded with graphite are massed together to form a spherical fuel element with a diameter of about 6 centimeters. The high temperature reactor ... might contain 100,000 or more of these fuel elements.

CONT

The pebbles are ... designed to passively limit the amount of heat unleashed by the nuclear fission reactions that drive the reactor. The fissionable material is divided into groups of 100 million billion uranium-235 atoms scattered within a 0.5 mm sphere of uranium dioxide. That core is coated with four containment layers. ... Some 15,000 carbon-coated uranium dioxide kernels, looking like nuclear poppy seeds, are embedded in a tennis ball-size graphite and resin matrix. Graphite acts to slow the fission neutrons and so acts as an embedded moderator. The matrix is then encased in a 5 mm pure carbon shell, sintered, annealed, and machined to a uniform diameter of 6 cm.

French

Domaine(s)
  • Réacteurs nucléaires de fission
CONT

Les particules [de combustible] sont agglomérées au moyen d'une matrice carbonée de manière à former des corps sphériques [...] aisément manipulables. [...] le combustible est sous forme de boulets de 60 mm de diamètre, ayant une écorce de 5 mm sans particule, chargés en vrac dans le cœur [du réacteur qui] est formé par un très grand nombre de boulets (675 000 pour [un réacteur] THTR [thorium high temperature reactor] de 300 MW de puissance électrique). L'ensemble de ces boulets est contenu dans une large trémie en graphite, faisant office de réflecteur, munie au sommet d'un couvercle de même matière, et d'un (ou plusieurs) trou d'évacuation des combustibles à la base.

CONT

Chaque boulet mesure environ 60 mm de diamètre et renferme environ 11 500 particules. L'extérieur du boulet, sur 5 mm, ne contient pas de particule, renforçant ainsi le confinement des matières radioactives dans la matrice de graphite. Le cœur du réacteur sera constitué par un empilement de plusieurs centaines de milliers de boulets.

Spanish

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