Energy spectra and dose equivalents of neutrons which were produced by 35 MeV protons in an accelerator room and leaked through a labyrinth with three legs from it, were measured by a multi-moderator spectrometer and a dose-equivalent counter.
Two simple formulas developed by Tesch and Nakamura & Uwamino, were compared with the measured values in order to examine their adaptability.
Two new simple formulas were also developed to calculate the dose equivalent both in the source room and in the labyrinth.The first simple formula, ROLA-D, is based on Nakamura & Uwamino's formula and Goebel's universal attenuation curve.The second simple formula, ROLA-E, which is based on Shin's two analytical formulas, can calculate the neutron energy spectrum in addition to the dose equivalent.
Four simple formulas were intercompared with the measurements and the calculations by the three-dimensional Monte Carlo code, MORSE-CG.
Consequently, it was clarified that ROLA-D gave the best result for the dose equivalent of neutrons leaked through a labyrinth.

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Nodal kinetic equations for coupled reactors, namely multi-point reactor kinetics equations whose dependent variables are the fission sources of each reactor are derived rigorously, using kinetics parameters with the explicit dependence on a perturbation, from the time dependent multi-group diffusion equation.Exact expressions for the coupling coefficients, neutron life time and the change of the coupling coefficients due to the perturbation are given.Since the present equations are exact independent of the strength of the coupling, these equations can be used for any reactor by dividing a core into appropriate subregions.Some analytical expressions of the coupling coefficients, neutron life time and other kinetics parameters are given for some simple geometries.

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Heat transfer across a gas gap between a boron carbide pellet and a cladding in FBR control rod has been experimentally investigated.The main purpose of this investigation is to present a calculational method for the gap heat transfer in order to improve accuracy of thermal design for the control rod with 0.5mm gap width at a beginning of reactor operation.
Two types of tests have been carried out using simulated control rods.One is low temperature tests below 200°C.The test results indicated that the convective heat transfer has a negligible effect on the gap conductance when the Rayleigh number using the gap width as the characteristic length is below 0.1.The other is high temperature tests up to 600°C.
The results showed +10 to -5% variations in the gap conductance data due to eccentricity between the pellet and the cladding.The prediction based on conduction and radiation heat transfers considering a thermal expansion and an eccentricity gave better results of gap conductance having a maximum difference of only 17% from the measured ones.Calculation in the radiation heat transfer used thermal emissivities, 0.85 for the boron carbide and 0.15 for the cladding, measured by infrared thermography.

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Flow through diffusion method was used to determine the effective diffusion coefficient and the appropriate parameters for modeling iodide ion diffused through the compacted clay materials of kaolinite and bentonite which were supplied locally and from USA.The effects of clay structural characteristics on diffusion, the mechanism of iodide ion diffusion through the compacted bentonite were studied.
The effective diffusivity for kaolinite decreases with increasing bulk density and concentration of the diffusion species (I^-).The iodide ion was strongly repelled from the bentonite particle surface, the predominant diffusion path is in the interstitial water.The relationship between the iodide flux (J) and the formation factor (F) for the diffusion of iodide ion through the compacted clays can be described by the following empirical equation log(J^-1)=A+BF,
where A and B were constants.The inverse of iodide diffusion flux decreases with increasing formation factor.The types of clay and their structures have a significant effect on the diffusion of iodide ion through compacted clays.

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The precipitation behavior of the platinum group metals from a simulated high level liquid waste (HLLW) was experimentally examined in a sequential denitration process with formic acid.
The precipitation fractions of Ru, Rh and Pd were found to depend on pH of the denitrated solution.The precipitation fractions of Ru and Rh increased linearly with pH of the denitrated solution and became more than 98% over pH 7, and almost all Pd was precipitated at pH around 2.Results showed that more then 98% of Rh and Pd and about 80% of Ru could be recovered as precipitates from HLLW, by means of the sequential denitration process.

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Two-dimensional electromagnetic induction equations have been solved for liquid metal flows in a large scale electromagnetic flowmeter taking account of both effects of the velocity profile and the wall conductivity.Theoretical solutions for the scalar potential, the induced current and the induced magnetic field have been obtained by adopting a fixed velocity function which approximates the overall turbulent flow profile.The distribution of the induced current density shows the eddy current loops, and the return currents exist mostly in the fluid region.The distribution of the induced magnetic field is presented under a condition of a high magnetic Reynolds number.The maximum induced magnetic field is evaluated to be about one order less than the value estimated by a classical method.The vector distribution of the electro-magnetic force due to the current and the induced magnetic field is also presented and we found the cancelling effect which prevents this force from becoming a predominant one.Through the analysis of the experiment, it is found the interaction parameter of 0.12 can identify the timing at which the skin friction factor (C_f) begins to increase.Also a discussion is made how the MHD effect will appear.

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A boiling water reactor (BWR) has an excellent load following capability provided by a core flow control, which is used for changing a reactor power level and for compensating the subsequent Xe concentration change.
The core characteristics during load following operations are investigated in detail, using our reactor core simulator.Comparisons of changes of the Doppler reactivity, the void reactivity and the Xe reactivity during transients are performed.Also the features of Xe transient during load following operations are shown.
It has been shown that the core flow change required to compensate the Xe reactivity change produces much greater change of the void reactivity than that required for power level changes, and that the resulting local power change in the lower part of the core is greater than that in the upper part, because the Xe concentration change in the lower part is hardly compensated by the core flow control.Also the effects of power level changes, cycle patterns, and initial concentration of Xe and I on the Xe transient behavior have been investigated.

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