Neutron-absorbent control cluster for a nuclear reactor
AssigneesFramatome, Compagnie Generale des Matieres Nucleaires
InventorsDominique Hertz, Luc Pillet
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Abstract
A control cluster for a water cooled and moderated nuclear reactor, comprises a spider and rods suspended from the spider. Each rod contains neutron-absorbing material. In a lower portion of each rod, the material is a metal neutron absorber. In an upper portion, it is a stack of pellets of boron carbide B.sub.4 C. In a middle fraction occupying a height lying in the range 35% to 45% of the total height, it is zirconium diboride ZrB.sub.2 isotopically enriched in boron 10 or hafnium diboride HfB2.
Claims8
A control cluster for a water cooled and moderated nuclear reactor, comprising a spider and rods suspended from said spider, each of said rods containing neutron-absorbing material over a predetermined height, wherein said material is constituted:
- in a lower portion of each said rod, by a metal neutron absorber;
- in an upper portion of each said rod, by a stack of pellets of boron carbide B.sub.4 C;
- and
- in a middle fraction of each said rod, occupying a height lying in the range 35% to 45% of the predetermined height, a material selected from the group consisting of zirconium diboride ZrB.sub.2 isotopically enriched in boron 10 and hafnium diboride HfB2.
A water cooled and moderated nuclear reactor having a core, upper internals above the core and a plurality of control clusters each displaceable vertically between said core and said upper internals and each of said clusters having a spider and having rods suspended from said spider and each containing neutron absorbing material, wherein said control clusters comprise black clusters having a high degree of anti-reactivity and gray clusters having a degree of anti-reactivity lesser than that of black clusters, and
- wherein neutron absorbing material in the rods of only some of said black clusters is constituted:
- in a lower portion of each said rod, by a metal neutron absorber selected from the group consisting of hafnium and Ag--In--Cd alloy;
- in an upper portion of each said rod, by a stack of pellets of boron carbide B.sub.4 C;
- and
- in a middle portion of each said rod, occupying a length in the range 35% to 45% of a complete height of the neutron absorbing material, a material selected from the group consisting of zirconium diboride ZrB.sub.2 isotopically enriched in boron 10 and hafnium diboride HfB2.
Dependencies are inferred from the claim text.