| 摘要 |
PURPOSE: To trap a metal broken piece caused during repairing of a vapor separator or a foreign substance which enters a furnace from outside by a method wherein a broken piece trapper of a small resistance for circulation of water is provided on a lower or upper side of a bottom part tie plate. CONSTITUTION: A fuel rod bundle 25 constitutes one unit of a fuel assembly together with a bottom part tie plate 11, a top part tie plate 12, a spacer 13 and a casing. At a distance of at least 0.5cm on a lower side of the bottom part tie plate 11, a broken piece trapper 35 of a filter plate type is provided. Each square hole of a lattice of this trapper 35 is formed top be about 3×3mm, and margin region of a water flow resistance smaller than that for water flow of the trapper 35 itself with a gap 38 is provided between the trapper 35 and a support plate 4 in the periphery of the trapper 35. Herein, water introduced from a water supply inlet 3 flows in a fuel rod space in a casing part 1 via the trapper 35 and the plate 11 and is sent via a plate 12, but it is possible to prevent arrival at a fuel rod bundle by trapping a metal broken piece etc., by the trapper 35.
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