Neutron radiography (NR) technique was applied to analyze behaviors of thermal neutrons in slabs, which have a wide range of the ratio γ, of scattering to non-scattering cross sections. Transmittances were measured for various materials as basic data for NR study. Scattering components were estimated and subtracted from observed neutron intensities measured behind slabs. Effective total macroscopic cross sections were estimated and were found they agreed with given values of ASTM E748-80 within ±20%. Defects (voids and impurities) were also analyzed, and their detection limits for thickness t were estimated for materials of various γ as a function of t.

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The parallel and perpendicular velocity distributions of a gadolinium atomic beam produced with an axial electron beam gun have been measured by a Doppler-shift technique and a Doppler limited absorption spectroscopy, respectively. The atomic density of 10¹⁸10¹⁹ atoms/m³ at a laser irradiated zone was sufficient for the process, such as an atomic vapor laser isotope separation. The atomic beam velocity of 800 m/s was obtained by a free expansion near an evaporation surface. This velocity, however, was 100 m/s slower than that we had measured with a magnetic transverse electron beam gun in a previous experiment. The reasons for the slower velocity in this experiment than that in the previous one are discussed. In keeping with the deposition rate, the parallel translational temperature rapidly decreased to 200 K, while the perpendicular translational temperature gradually increased and approached to the parallel translational temperature. This result suggested that the collisional region where both translational temperatures are equal extended to the laser irradiated zone in high-rate evaporations.

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A benchmark calculation for a deep penetration problem of 14 MeV neutrons through a 3 m thick iron slab was carried out by using a vectorized continuous energy Monte Carlo code MVP with the JENDL-3 and ENDF/B-IV cross sections. Reference solutions for neutron spectra and averaged cross sections were obtained at various locations through the iron slab with good statistics owing to a high computation speed of the code. The accuracy of multigroup calculations with the JSSTDL/J3 library was investigated by comparison with the obtained reference solutions.
Both calculations with JENDL-3 and ENDF/B-IV showed a similar attenuation of total fluxes from thermal to 14 MeV through the slab, while differences of one order at the maximum were observed in the calculated fluxes in the resonance energy region. The multigroup calculations with the JSSTDL/J3 295- and 125-group libraries underestimate the streaming effect through the cross section minima above the well-known 24 keV window, which resulted in the underestimation of fluxes above this window by more than two decades at 3 m penetration compared with the continuous energy method. Taking into account the spatial dependence of averaged cross sections, the underestimation was reduced to about one decade. It was found, however, that an accurate prediction of streaming effect is fairly difficult by the multigroup method.

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With a view to practical application of the CO laser to underwater cutting of thick steel plates, a nozzle for creating a local dry zone on the workpiece has been developed and tested. The nozzle directed against the workpiece surface discharges a jet of air, which forms the local dry zone, bounded by a cone of high-speed water jet discharged from a concentric annular outlet. Preliminary tests were performed to optimize the nozzle shape and operating conditions. The resulting nozzle was used with a 5kW CO laser for actual underwater cutting tests on stainless steel plates : Entirely satisfactory cutting performance was confirmed on various workpiece geometries and working positions.

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Structural integrity evaluation of local wall thinning caused by erosion is important for maintaining the integrity of piping systems in power generating plants. The pipe of interest is a STS 42 carbon steel pipe loaded by an axial load and subjected to an internal pressure. Acceptable thinning length and width were determined from the allowable size of circumferencial and axial cracks in pipes, and the wall thickness is determined from the local membrane stress rule. Thus the acceptable extent and depth of wall thinning were proposed. Double-ended fracture can then be prevented if the local wall thinning is kept within this acceptable size.

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Displacement chromatographies of Gd adsorption band in cation exchange resin were performed to observe the isotope effects in the Gd ion exchange processes involving complex forming reagents. The heavy isotope of ¹⁶⁰Gd was found to be enriched at the front boundary of Gd adsorption band and the lighter isotopes of ¹⁵⁶Gd, ¹⁵⁷Gd and ¹⁵⁸Gd were enriched at the rear boundary in both cases of 20.1 m elution with EDTA and 14 m elution with malic acid, as predicted in the theoretical relations. Observed separation coefficients are 4.9×10^-5, 4.0×10^-5 and 2.5×10^-5 for isotopic pairs of ^156/160Gd, ^157/160Gd and ^158/160Gd, respectively, in the case of EDTA elution. In the case of malic acid elution, smaller separation coefficients were observed as 1.8×10^-5, 1.6×10^-5 and 0.92×10^-5 for isotopic pairs of ^156/160Gd, ^157/160Gd and ^158/160Gd, respectively.

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When using cement solidification for spent ion exchange resin, resin content in the waste form is typically controlled below 20vol%. This is because the waste forms crack and deteriorate in water at higher resin contents. The deterioration mechanism and its preventive measures were investigated in this study.
Swelling pressure of the resin was experimentally measured for various waste forms. The resin in the waste form tended to swell under a water immersion condition and tensile stress was exerted on the cement matrix. The stress value changed in the region of 1.55.5 MPa depending on such factors as resin content and its type. The waste form was deteriorated in water when the tensile stress was higher than the tensile strength of the cement. These results suggested that the deterioration could be prevented by increasing the tensile strength of cement. A fiber reinforced cement was developed for which tensile strength was almost doubled (7MPa) by adding 10wt% steel fiber to the cement. This prevented deterioration and allowed the resin content to be increased from 20 to 42vol%.

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The extraction of Np(V) in the presence of U(VI) or Nd(III) was studied with 0.2 _M CMPO-decalin and with 0.2 _M CMPO-1.4 _M TBP-n-dodecane. Distribution ratios of Np(V) decreased with increasing the concentration of Nd(III), which was considered to be explained by the decrease in the concentration of free CMPO. On the other hand, distribution ratios increased as the concentration of U(VI) increased. The absorption spectrum of Np(V) in organic solution showed a new absorption peak which was probably attributable to the formation of cation-cation complexes of Np(V) and U(VI). Assuming the formation of cation-cation complexes, the dependence of distribution ratio of Np(V) on the concentration of U(VI) was found to be semi-quantitatively explained.

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The CR-39 detectors were irradiated with three kinds of fast neutrons and etched in several alkaline solutions. Size distributions of etch-pits were obtained from analysis of microphotographs. An automatic image analyzer was used to obtain the density of etch-pits. When etching conditions were kept at 30% KOH, 90°C and 1h, the sensitivity was found to be 3.8×10^-4, 4.9×10^-4 and 2.4×10^-4 for fission, Am-Be and 14 MeV neutrons, respectively. From analysis of increasing rate of the sensitivity, it was found that the track density in CR-39 roughly corresponded to the density of elastic scattering with H, C and O in the case of Am-Be and 14 MeV neutrons, however, the track density was somewhat smaller than the elastic scattering density in the case of fission neutrons. The size of etch-pits increased with neutron energy. The etching time could be reduced to less than 1/10 as a result of a rising from 60 to 90°C. After due consideration of background counts, a dose equivalent of 0.2mSv could be measured with this system.

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The design process of a new reactor consists of broad technical areas. The work of each area may be carried out independently to achieve design target or to satisfy design criteria. The decisions made in one area will affect the design basis in most other area. The design process is thus iteratively performed. To satisfy all design criteria, many parametric survey calculations should be carried out in general. In any case it would be difficult to find an optimal set of design parameters. Such a situation in design problems would be fairly different from that in anomaly diagnosis problems with respect to an application of the AI technique. To reduce the number of iterations at the stage of the design study, it is useful to draw a design window in which the design is feasible. Any parameter set inside a design window area can satisfy design criteria or goals. Design windows obtained for various combinations of design parameters in each area help designers with the decision of design parameters. Even in this case, a considerable amount of calculations must be performed by varying parameter values.
At the present work, we intended to search automatically a design window with use of AI based techniques in order to save cost and time. One of the authors has proposed the design window search algorithm for a reactor structural problem and shown its validity⁽¹⁾. Since there are many design parameters, a design window is generally a sub-space of multi-dimensional one. As the first step, we investigated a procedure to search a window in two-dimensional space, that is, for two parameters. The search procedure and an example applied to the thermal hydraulic design are described below.

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The concept of an advanced water chemistry diagnosis system for detection of anomalies and preventive maintenance of system components is proposed and put into a concrete form. Using the analogy to a medical inspection system, analyses of water chemistry change will make it possible to detect symptoms of anomalies in system components.
Then, correlations between water chemistry change and anomaly occurrence in the components of the BWR primary cooling system are analyzed theoretically. These fragmentary correlations are organized and reduced to an algorithm for the on-line diagnosis system using on-line monitoring data, pH and conductivity. By using actual plant data, the on-line diagnosis model system is verified to be applicable for early and automatic finding of the anomaly cause and for timely supply of much diagnostic information to plant operators.

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