초록

A fuel assembly mechanical flow restriction apparatus for detecting failure in situ of nuclear fuel rods in a fuel assembly during reactor shutdown.

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1. A fuel assembly mechanical flow restriction apparatus for detecting failure of a nuclear fuel rod in a nuclear fuel assembly situated in a reactor core of a boiling water reactor, the reactor core comprising a plurality of nuclear fuel assemblies comprising parallel fuel rods supported at an uppe

1. A fuel assembly mechanical flow restriction apparatus for detecting failure of a nuclear fuel rod in a nuclear fuel assembly situated in a reactor core of a boiling water reactor, the reactor core comprising a plurality of nuclear fuel assemblies comprising parallel fuel rods supported at an upper end by an upper tie plate and an outer channel surrounding the fuel rods for the passage of reactor coolant from a lower end to the upper end of the fuel assembly, the outer channel having upper edges, the upper end of the fuel assembly passing through and being supported by a reactor core top guide structure, the fuel assembly mechanical flow restriction apparatus comprising:a testing hood comprising a top plate and side plates to form a structure with an open bottom forming an internal volume for positioning over the tops of at least one of the nuclear fuel assemblies and for receiving gases escaping from a failed fuel rod within the fuel assembly, the side plates for resting on the reactor core top guide structure; a flow restrictor positioned within the testing hood and over at least one of the nuclear fuel assemblies, the flow restrictor comprising a sealing plate for positioning on the upper edges of the outer channel of the fuel assembly for mechanically blocking fuel assembly coolant flow exiting the upper end of the fuel assembly; a probe assembly having at least one probe head with at least one thermocouple for sampling the coolant water within the fuel assembly for detecting failure of a nuclear fuel rod in the nuclear fuel assembly; means for causing the sealing plate of the flow restrictor to be positioned on the upper edges of the outer channel of the fuel assembly for mechanically blocking fuel assembly coolant flow from exiting the upper end of the fuel assembly and for causing the probe head to be immersed in the fuel assembly reactor coolant water within the outer channel wherein the means for causing the sealing plate to be positioned on the outer channel of the fuel assembly is hydraulic.