[en] This invention refers to a fuel unit comprising a simple system for locking it in position near its lower end on to a nuclear reactor core support, in such a manner that the locking action can be selectively operated from the upper end of the unit. Under this invention, this device enables locking and unlocking to be effected without using any part of the supporting structure to an excessive extent. The lock can be released from a distance in the event of any failure of a locking component

[en] The upper internal structures which are located above the core and below the head cover may play a significant role in the hydrodynamic of an energy excursion such as a hypothetical core discruptive accident (HCDA) by mitigating the slug impact on the head. For purposes of studying these effects, a structural model was developed for the upper internals and the support columns which connect them to the head of the reactor vessel. This structural model can be used either by itself or in an interactive mode with one of the hydrodynamics codes developed at Argonne, such as ICECO or REXCO. (orig.)

No abstract available

[en] A nuclear fuel assembly is described, adapted to be locked into first mating surfaces on a core support stand, comprising a lower end fitting having posts for resting on the stand; elongated hook members pivotally connected at one end to the lower end fitting and having a second mating surface at the other end to engage the first mating surfaces; actuating means located between the posts on the lower end fitting and being vertically movable relative to the end fitting; and rigid links pivotally attached at one end to the hook members intermediate the connection of the hook members to the end fitting and the second mating surface and pivotally attached at the other end to the actuating means, the link having a length between the pivoted connections such that the second mating surface on the hook members locks into engagement with the first mating surfaces on the stand as the links approach the horizontal. (author)

[en] The object of this invention is to harness the force of the ascending coolant of the reactor to actuate a locking mechanism holding the fuel unit in position against the core support. The invention makes for easy unlocking of the unit so as to facilitate its removal. The fuel unit is held in position near its lower end by a compact device, of easy fabrication and use, that does not cause any significant drop in the pressure of the coolant in the reactor vessel. Under the invention, the fuel unit can be unlocked from a distance in the event of any failure of the normal locking components

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[en] A model testing has been performed to investigate the flow characteristics of a vortex chamber, which plays a role of a flow switch and passively controls the discharge flow rate. This method of passive flow control is a matter of concern in the design of advanced nuclear reactor systems as an alternative to the active flow control to provide emergency water to the reactor core in case of postulated accidents like LOCA (Loss-of-Coolant accident). By changing the flow direction in the vortex chamber and varying the flow resistance inside the chamber, the vortex chamber can control passively the injection flowrate. fundamental characteristics such as discharge flow rate and pressure drop of the vortex chamber are measured, and its parametric effects on the performance of the vortex chamber are also systematically investigated. (author)

[en] A nuclear reactor core stabilizing arrangement is described wherein a plurality of actuators, disposed in a pattern laterally surrounding a group of elongated fuel assemblies, press against respective contiguous fuel assemblies on the periphery of the group to reduce the clearance between adjacent fuel assemblies thereby forming a more compacted, vibration resistant core structure. 7 claims, 4 drawing figures