An experiment was undertaken on the θ-pinch collapse of a solid potassium liner in a temperature range of 1057°C. The liner was 47mm long and 34mm thick with an outside diameter of 66mm. The radial motion of the collapsing liner was analyzed by visco-plastic model. In the above range of temperature, assuming the potassium to behave as a Bingham fluid, the kinematic elongational viscosity and the yield stress of solid potas-sium were found to be roughly 24m²/s and bar, respectively, based on the experi-mental data obtained from the collapsed liner. The perturbed motion due to the Rayleigh-Taylor instability was also analyzed with account taken of the effect of viscosity. The kinematic shear viscosity obtained from the elongational viscosity is known to be of the order of 1m²/s. The evidence would indicate that this shear viscosity is so large as to exert an inhibitive effect on the perturbations of higher mode (m ?? 10) under the present experimental conditions.

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The neutron capture cross sections of ⁹³Nb, ¹²⁷I, ¹⁶⁵Ho, ¹⁸¹Ta and ²³⁸U were measured from 3.2 to 80keV using the time-of-flight method. The neutron beam was produced by the KURRI 46-MeV linear accelerator and capture γ-rays were detected by a C₆F₆ or C₆D₆ liquid scintillation detector. As the result of the use of a direct-coupled operational pre-amplifier, the detector recovered rapidly from the γ-flash such that data for higher energy neutrons can be obtained in spite of the short flight path of 11.7m. The neutron sensi-tivities of both detectors are compared and the superiority of the C₆D₆ detector is shown.
The experimental results of capture cross sections, corrected for resonance self-shield-ing and multiple scattering and normalized to the 24-keV absolute values, are shown numerically and graphically, and compared with other data. The agreement between the data is fairly good for ¹⁶⁵Ho and ²³⁸U, but not for ⁹³Nb, ¹²⁷I and ¹⁸¹Ta. The discrepancy between the data may be caused by the difference of the reference cross sections used for each experiment.

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The large negative reactivity is measured in Semi-Homogeneous Experimental facility (SHE). Experimental methods are Sjostrand's pulsed neutron, source multiplication and rod drop methods beside revised King-Simmons' pulsed neutron methods. Neutron detectors are placed at various points in the core region for multi-points measurement.
Usual one-point reactor model analysis resulted in the reactivity values, strongly de-pendent on the detector position with the increase of subcriticality. In addition, disagree-ments between the used experimental methods are also pointed out.
In order to overcome these difficulties due to the spatial higher harmonics and the kinetic distortion in the neutron flux distribution, an integral version analysis is applied, in which use is made of multi-points reactor model. In the analysis, space integration of the neutron counts obtained throughout the core region is made with weights of the ad-joint function of fast neutrons, calculated using the two- or three-dimensional diffusion code. The negative reactivity values determined by the integral version analysis agreed well with each other within the uncertainty of 5% in the reactivity range down to -50 dollars.
It is concluded that all the experimental methods are adequate for precise determination of the large negative reactivity of reactor provided that the integral version analysis is utilized or that correction is made for the change of the neutron generation time using precise calculation.

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A code "ACTFCI" has been developed for analyses of Fuel Coolant Thermal Interac-tion in a coolant channel. The code can deal with the dynamic behavior of coolant in r-z geometry, but does not take into account the dynamics of fuel particle two-dimensional movement, the fuel being considered only as heat source for the coolant. The ICED-ALE method was used for the numerical analyses of the three conservation equations and two equations of state for single and two-phase sodium. A sample calculation is given concern-ing the period up to initiation of sodium boiling, for a geometry representing a wrapper tube of reduced size. Despite this difference of the model from actual size, the calculated results suffice for demonstrating the utility of this method in obtaining stable solutions on single-phase pressure wave propagation in both r and z directions, and on sodium boiling initiation triggered by the rarefaction wave returning to the interaction region from channel extremity.

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For the solvent extraction of reprocessing plant, mixer-settler, pulsed column are op-erated and centrifugal extractor is expected to be used. Mixer-settler has the defect of long contact time. It comes out to cause the solvent damage by radiation in FBR fuel re-processing. In order to escape from the damage, pulse column and centrifugal extractor should be used for FBR spent fuel. However, the characteristics in centrifugal extractor have not yet been fully analyzed, while those of mixer-settler are advanced much. There-fore, the agitation experiment was made to find out the difference of drop formation be-tween mixer-settler and centrifugal extractor. From the results, the average drop diameter is proportional to Weber number to the power of -0.58, when the contact time is long. However, the agitation velocity did not affect the average drop size, when the contact time is less than 11.3 s.

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Composite hydrous titanium(IV)-iron(II) oxides prepared by precipitation from homo-geneous solutions were studied with a view to developing magnetic adsorbents for uranium extraction from sea water.
Higher uranium adsorption capacity was registered with homogeneous than with het-erogeneous solution used for preparing the oxide. The adsorbents for uranium prepared from homogeneous solution moreover were found to require the copresence of urea and a suitable anion such as SO^2-₄, in order to provide strongly active adsorption of uranium.
The value of saturated magnetization of the composite hydrous oxides decreased with increasing titanium mole fraction up to 0.75, increase of the titanium mole fraction had, on the other hand, the effect of enhancing uranium adsorption capacity, which however sat-urated beyond 0.75 titanium mole fraction.
The change of enthalpy brought by the uranium adsorption on the composite hydrous titanium(IV)-iron(II) oxides was 10kcal/mol, and the amount of change independent of the conditions of precipitation.

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