| 摘要 |
PURPOSE:To maintain the soundness of a core without largely affecting a core output even when a control rod withdrawal accident would be generated by uniformly distributing and arranging a plurality of core fuel assemblies wherein a plurality of fuel pins are arranged in an outer cylinder and special assemblies. CONSTITUTION:An outer cylinder 104 has a hexagonal section and an entrance nozzle 105 is formed on the lower end of the cylinder 104. The upper end of the cylinder 104 is formed with an opening 106. A plurality of coolant flow inlets are formed in the entrance nozzle 105. A support plate 108 is mounted to a lower portion in the outer cylinder 104. A guide pipe 109 is mounted to the support plate 108 as the lower end of the guide pipe 109 is supported by the support plate 108. A plurality of coolant passages 110 are formed in the support plate 108. A plurality of fuel pins 111 are accommodated in a space between the guide pipe 109 and the outer cylinder 104. The fuel pins 111 each are filled with a fuel material 114. On the other hand, neutron absorbers 112 are accommodated in the guide pipe 109 and each filled with a neutron absorbing material 115. When, for example, a control rod withdrawal accident would be generated, since the absorbers 112 for the whole special assemblies 103 are inserted all together and a nuclear reactor is stopped, its safety can be maintained.
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