Neutron nuclear data in the energy range between 10^-5 eV and 20 MeV have been evaluated for 172 nuclides from ⁷⁵As to ¹⁵⁹Tb in the fission product mass region to provide data for the JENDL-3 fission product nuclear data library. Evaluation was made on the basis of recent experimental data reported up to 1988 and the nuclear model calculations. Resonance parameters have been evaluated on the basis of measured data set and a REPSTOR system developed in JAERI. The spherical optical model and statistical theory were applied to calculation of the total, capture, elastic and inelastic scattering cross sections, and the multistep evaporation model and pre-equilibrium theory were used for threshold reaction cross section calculations. For the even-even nuclides around fission yield peaks, direct inelastic scattering cross sections were calculated with the distorted wave Born approximation. Nuclear model parameters, such as optical model parameters, level density parameters, r-ray strength functions and Kalbach constant of the pre-equilibrium model were determined so as to give a good agreement between the calculated and measured cross sections. The parameter systematics were obtained as a function of nuclear mass or atomic number. For thermal capture cross sections, a simple relation between measured and calculated cross sections was found as a function of level spacing. The evaluated results were compiled in the ENDF-5 format.

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A method of knowledge generation and utilization using design information is described. This method is used to generate rules concerned with propagation of state change in a plant due to equipment manipulation or anomaly. The rules describe macroscopic behavior of plant subsystems consisting of many devices, and are used for high speed information processing in expert systems for plant diagnosis, maintenance, etc. Knowledge generation is comprised of two steps. In the first step, the changes of state values are propagated according to connectivity between devices and the input-output relationships of the devices. In the second step, the input change, output change of plant subsystems, and other information are edited according to the results of state change propagation, and rules for state change propagation are generated. By using these rules, the simulation of state change propagation can be accelerated about 10 times compared with the case of device level propagation. The method of knowledge generation has been applied to the inference system in a maintenance work scheduling system and a new-type expert system was realized, It grows by generating rules for problem solving and by expanding its knowledge base by itself.

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An interfacial friction model for two-fluid model code has been developed for the countercurrent gas-liquid flow limitation at hot leg in a pressurized water reactor. Firstly, using a typical two-fluid model code TRAC-PF1/MOD1, we analyzed whether the interfacial friction model under countercurrent stratified flow by Ohnuki et al., which has been verified with an envelope model at steady state, functions well for the dynamic calculation with the two-fluid model code or not. It was found from the analyses that the model by Ohnuki et al. should be combined with a suitable interfacial friction model for the slug flow regime in hot leg. Based on flow observation in a small scale air-water experiment, models at the bend of hot leg and in the roll wave regime in the horizontal flow path of hot leg were newly developed as the model in the slug flow regime and the slug flow model was combined with the model by Ohnuki et al.. The validity of the present model was confirmed with the data under various conditions of scales, pressures and fluid combinations (inner diameter : 0.0250.75 m, pressure : O.17.1 MPa and air-water or steam-water).

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This paper describes the result of transient experiments using low enriched uranium silicide plate-type fuel for research reactors. The pulse irradiation was carried out at Nuclear Safety Research Reactor (NSRR) in Japan Atomic Energy Research Institute. The results obtained were :
(1) At fuel plate temperature of below 400°C, a good dimensional stability of the tested fuel was kept. No fuel failure occurred.
(2) At a plate temperature of about 540°C, a local crack was initiated on the Al-3% Mg alloy cladding. Once the cladding temperature exceeded the melting point of 640°C, the fuel plate was degraded much by increased bowing and cracking of the denuded fuel meat occurred after relocation of molten Al cladding. Despite of these degradation, neither fragmentation of the fuel plate nor mechanical energy generation occurred up to the cladding temperature of 971°C.
(3) At the temperatures of around 925°C, the reaction of silicide particles with molten Al in the matrix and that of cladding occurred, forming Al riched U (Al, Si) compounds and Si riched (U, Si) compounds at the outermost surface of the silicide particles.

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An analytical model has been developed to describe hydraulic characteristics of a hollow fiber membrane filter (HFF) for condensate purification in BWR power plants. Using this model, a module structure was proposed to minimize pressure drop at the beginning of HFF operation. That is, given flow rate of a module, both dimensions of the inner diameter and the length of a single fiber membrane were designed to have optimal values, giving minimum volume for the module. The mechanism of Fe ion crystallization on HFF surface which determines operation life time was clarified and a countermeasure against it was developed. Precoating of amorphous iron crud effectively inhibited crystallization. Taking account of the crystallization, a simulation code was developed to predict pressure drop trend in the course of HFF operation.

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Laser-induced thermal lensing effect was studied to analyze solute concentration in organic solutions. A new method for concentration measurement was proposed based on the thermal lens oscillation, and demonstrated for uranyl nitrate in 30%tri-n-butyl phosphate solution. A pulsed dye laser system was used to excite uranyl ions so as to create a local temperature gradient in the sample solutions. This thermal effect led to a change of refractive index which could be detected by the divergence of the probe beam, for which a He-Ne laser was used. When the laser beams propagated horizontally below the free surface of the liquid and the depth of the beam position was increased, the signal electronically obtained by the probe beam departed from steadiness and exhibited periodic behavior (thermal oscillation). The boundary of the thermal lens oscillation was clearly determined by fast Fourier transform spectral analysis of the obtained signal, and related with absorbance of the sample solution. The concentration difference of 1×10^-4M uranyl ion was detected by applying this procedure. This method is expected to be useful for verifying concentration of nuclear materials below the concentration limit.

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Solvent extraction of Np(V) from nitric acid solution by n-octyl(phenyl)-N, N-diisobutyl-carbamoylmethylphosphine oxide (CMPO) in the presence and absence of tri-n-butyl phosphate (TBP) has been studied using decalin and n-dodecane as diluents. Without the TBP, Np( V ) can be extracted using CMPO in decalin with extraction equation :
NpO₂⁺_(a)+NO₃^-_(a)+2CMPO_(o)=NpO₂(NO₃)2CMPO(_o)
The maximum Np(V) distribution ratio using 0.65 M CMPO in decalin from 2 M nitric acid is 4. The net effect of TBP to CMPO at 2M nitric acid is slight suppression of Np(V) distribution ratio. However, at low CMPO concentration (0.2 M ?? ) after the Np(V) distribution ratio reaches the minimum value, the distribution ratio gradually increases as the TBP concentration increases. No synergistic interaction of CMPO and TBP has been observed.

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It is found that the heavy-water Fricke solution showed lower sensitivity to fission neutrons (G-value of 3.7) but higher sensitivity to r-rays (G=16.3) than the light-water Fricke solution (G=5.6 for neutrons ; G=15.4 for r-rays). Using these differential G-values of the paired solutions and the basic principles of Fricke dosimeter, the following paired equations were derived for the heavy-water and the light-water solutions that were exposed to neutron-gamma mixed radiation ; D_N=1, 400A-1, 200A' and D_G=460A'-270A, where D_N and D_G are the absorbed doses of neutrons and r-rays in the light-water solution, respectively, and A and A' are absorbance increases in the light-water and the heavy-water solution, respectively. The validity of the paired equations was tested by exposure of the paired solutions to the mixed fields of nuclear reactors at Kinki University and Musashi Institute of Technology. Obtained pairs of DN and D_G values agreed reasonably well with those measured by paired ionization chambers.

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The feasibility of fast fission system confining long-lived nuclides without other supporting system as synergetics for fuel sustainment and waste incineration was studied from the aspects of nuclear material balance and neutron economy. The continuous utilization of fast fission system which confines all actinides in the reactor but discharges all FP will lead to huge accumulation of radioactive wastes such as ¹²⁹I, ¹³⁵Cs, ¹⁰⁷Pd, ⁹³Zr, ⁹⁹Tc, ¹²⁶Sn and ⁷⁹Se in the far future. Then we studied the feasibility of the system that these long-lived seven FP are also confined in the reactor with actinides. In this scheme, all the long-lived nuclides to be disposed of were exposed with neutrons in the reactor and removed as different nuclides after nuclear transmutation. As the wastes stored in the repository was composed of only shorter-lived nuclides, total amount of radioactive wastes in the repository was suppressed to be less than a few tons per 3 GWt reactor.

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An evaluation method with uncollimated r-rays has been proposed for the dead zone of gas counters without entrance windows. The obtained dead zone characteristics for the proportional, SQS and GM modes are almost consistent with those obtained with β-rays. Some difference in the dead zones obtained with r-rays and β-rays has been discussed. This new method is effective to confirm and improve the operation mode of counters.

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Gaseous C₂ hydrocarbons, which would be the major impurities after methane in plasma exhaust gases, were analyzed by laser Raman spectrometry. Deuterated C₂ hydrocarbons, which were prepared by mixing acetylene, ethylene or ethane with D₂ gas were experimentally measured. Suitable bands for quantitative analyses can be selected as the _ν2 vibrations at 1, 7641, 973 cm^-1, _ν2 vibrations at 1, 5181, 627 cm-1 and some _ν3 vibrations at 9851, 344cm^-1, and _ν3 vibrations at 842994 cm^-1, for deuterated acetylenes, ethylenes and ethanes respectively. Those bands are based on the CC stretching vibrations, except for the deformation vibration _ν3 of the ethylenes. Isotopic C₂ hydrocarbons in fusion fuel gas processing will be analyzed by using the same bands in laser Raman spectroscopy.

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