US 4,059,483 AGranted

Nuclear fuel assembly seismic amplitude limiter

AssigneeCombustion Engineering, Inc.

InventorAndrew J. Anthony

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Abstract

The ability of a nuclear reactor to withstand high seismic loading is enhanced by including, on each fuel assembly, at least one seismic grid which reduces the magnitude of the possible lateral deflection of the individual fuel elements and the entire fuel assembly. The reduction in possible deflection minimizes the possibility of impact of the spacer grids of one fuel assembly on those of an adjacent fuel assembly and reduces the magnitude of forces associated with any such impact thereby minimizing the possibility of fuel assembly damage as a result of high seismic loading. The seismic grid is mounted from the fuel assembly guide tubes, has greater external dimensions when compared to the fuel assembly spacer grids and normally does not support or otherwise contact the fuel elements. The reduction in possible deflection is achieved through reduction of the clearance between adjacent fuel assemblies made possible by the use in the seismic grid of a high strength material characterized by favorable thermal expansion characteristics and minimal irradiation induced expansion.

Claims14

Dependent claims

In a nuclear reactor fuel assembly, the fuel assembly including a plurality of zircaloy spacer grids which locate and support elongated fuel elements which pass therethrough, said fuel assembly further including a plurality of guide tubes which extend through the fuel assembly parallelly of the fuel elements and which receive movable neutron absorber elements, the improvement comprising:

at least a first seismic grid positioned intermediate a pair of spacer grids, said seismic grid having a greater resistance to deformation when compared to the spacer grids and having larger external dimensions than said spacer grids, said seismic grid including:
a steel perimeter strip, said perimeter strip defining the exterior dimensions of said seismic grid, said perimeter strip being provided with a plurality of openings and a plurality of inwardly extending projections;
a plurality of divider members, said divider members being mechanically coupled to said perimeter strip and being arranged in a crossing pattern to define a plurality of grid sectors, said grid sectors being dimensioned so as to present fuel element motion limiting surfaces on said divider members and perimeter strip normally spaced from and out of contact with fuel elements passing through said seismic grid;
and
means attaching some of said divider members to the guide tubes to support said seismic grid on the fuel assembly.

2 more elements

Dependencies are inferred from the claim text.