[en] The enlarged beam bore hole is required, in the special RF cavity, for the purpose of the beam handling, to provide higher quality beams by using the KEK/JAERI joint project linac. To understand practical limits and cost on solution, at least consideration and comparison on structural parameters are necessary to be investigated. Therefore, parameters of coupled cell structures with enlarged bore hole radii were considered. They were not candidates with evident performance in RF parameters. All structures were close by RF effects, and possible difference of order in 10% looked like no reason for special development, especially taking into account that cavity was single on a case of linac. All of narrow band structures were based on deterioration of operating dispersion curve with increasing bore holes. This deterioration could be reduced by structures coupled with slots based on reasonable decreasing of the cavity efficiency. (G.K.)

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No abstract available

No abstract available

[en] The VG-400 reactor power distribution control and monitoring system uses neutron detector readings in the top axial and radial reflectors for reconstructing spatial energy distribution in the pebble bed core. The detector readings are processed by the methods realized in the MOD and SCURT codes. The spatial distribution of the ²³⁵U(n,f) reaction rates over the volume of the GROG critical assembly core, being a scale model of start charging of the VG-400 reactor, is experimentally studied. For two critical assembly states calculations are performed according to the MOD and SCURT codes, permitting to estimate the accuracy of energy release field reconstruction. The conclusion is made that neutron field distributions are more precisely reconstructed in the core centre than at the periphery. The calculation error is 3-9%

[en] The testing results of the NEKTAR, WIMS-D4 and VIANKA programs used in designing the VG-400 reactor for calculation of neutron-physical characteristics of the core are considered. The results of calculations performed for the VG-400 core and GROG critical assembly bench used for experimental study of the VG-400 reactor physics are given. The data obtained have demonstrated satisfactory coincidence of the measured and calculated results. They also permit to estimate the possibilities of VG-400 reactor scale modelling at the GROG bench

[en] For the puspose of increasing the fast response of measurement systems on the base of the CAMAC modUles an aU, xiliary controller intended for acquisition and storage of data formed in analog-to-digital converters situated in the CAMAC crate is designed. The use of the controller in the cyclotron on-line measurement and calculational system for nuclear-physical experiments ensured the system dead time decrease in 8-10 times and permitted to liberate the computer of routine operations

[en] This article describes the use of a multichannel scanning device for the study of the physical characteristics of power reactors on criticial assemblies. The device described incorporates a chain of small-sized neutron flux detectors, a mechanhCal device for the synchronous movement of the detectors, and measurement and recording equipment, including an MERA-60 computer with terminal facilities. A structural layout of the multichannel scanning device is given. The device is used in the current and pulsed regimes of operation of the detectors, and data recording is possible both by means of a computer and autonomously. Distributions of the reaction velocities are shown

[en] The comparison (in 2D approximation, without taking into account end plates) of RF parameters for four chamber RFQ cavities, differing in chamber shape, is done. Using lumped parameters expressions for RF characteristics estimations are given. It is shown that per unit length capacity between electrodes depends only on the shape of the electrode and don't depend on dimension. Dependence of cavity characteristics from working frequency is considered

[en] A change of HTGR reactor reactivity under three accidental situations including steam generator tube rupture and steam-helium mixture entry into the core, a change of fuel pebble bed porosity under siesmic effects, caving of a part of top and bottom reflectors, is analyzed taking the VG-400 and VGM reactors as examples. Classification of accidents to the rate of reactivity growth and the inserted reactivity value, is performed. A conclusion is made that an accident with water ingress, in which the rate of reactivity insertion is close to rapid efficiency of scram rods is the most severe one