Gamma-ray exposure buildup factors up to 40mfp have been calculated using the Monte Carlo code EGS4 for water, iron and lead for point isotropic sources. The new algorithm which applies particle-splitting at each preset depth to simulate almost same number of particles from the preset depth is developed in order to obtain reasonable results with EGS4 at deep-penetrations. Comparisons of these results to the standard data calculated with the moments method or the discrete ordinates code PALLAS show good agreements if the same cross section data and energy absorption coefficients are used.
The EGS4 calculations with this new algorithm will be a useful tool for future studies of gamma-ray buildup factors including the review of the standard data.

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A unified theory of identification in a feedback system is presented from the viewpoint of inverse problem on reactor noise. A power reactor described by a 4 block feedback model is expressed in terms of equivalent correlation functions as a 5 block feedback model with an additional loop, if one of subsystems of the reactor becomes unstable, however, the total system is stable by negative feedback effects, and if noise sources are not independent. The addition of a loop in the feedback system leads errors in estimation of open loop transfer functions. In the case, modified open loop transfer functions are identified instead of original ones. From the viewpoint of reactor diagnosis, notes on system identification are discussed on an open loop transfer function in a low power reactor and on effects of diagonalization in covariance space of noise sources.

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Presenting important alarms selected from a large number of activated alarms provides useful operational support under a transient status in a nuclear power plant. We have developed an alarm processing method which selects and presents important alarms depending on plant status.
In this method, important alarms are selected, first, based on physical relationships between alarms and component status including alarms themselves and second, even more important alarms are selected from the previously selected alarms according to the identified initial event causing the transient. Identification of the initial event is implemented by a neural network. The identified initial event and selected important alarms are presented to show the cause and influence of the transient.
A prototype based on the above alarm processing method was validated during the start-up test at Kashiwazaki Kariwa Nuclear Power Plant Unit Number 4 of Tokyo Electric Power Co. The initial events, which were load rejection, turbine trip and main steam isolation valve closure, were correctly identified and about 30% of all activated alarms were selected as important. It was verified by an operating expert that the presentation of the identified initial event and the selected important alarms were effective to understand rapidly and correctly the transient status of the plant.

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Isotope effects in a liquid-liquid extraction of strontium with dicyclohexano-18-crown-6 (DC18C6) were investigated. Unit mass enrichment factors were observed to increase with concentrations of strontium salt in an aqueous phase. Isotope distinguishing ability of DC18C6 to strontium isotopes was calculated as an intrinsic separation factor to be K_c=1.00051±0.00004. An odd mass number isotope, ⁸⁷Sr, was recognized to behave differently from even mass number isotopes, ⁸⁴Sr, ⁸⁶Sr and ⁸⁸Sr. The enrichment factor induced by a nuclear property (odd or even mass number) other than the mass difference was ε_O/E=-8.0×10^-4 which was observed with 3.2M Sr aqueous solution. Isotope shift of energy state for 5s-orbital of strontium produces the isotope shift in vibrational energy between the strontium ion and the DC18C6.

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The thermal diffusion coefficients D^T(ν)_i in multi(ν)-component mixture are given as the ratio of two determinants by Hirschfelder et al. In order to express thermal diffusion coefficients as a linear function of binary thermal diffusion factor α⁽²⁾_Tij, we enumerate four candidates of the function extended from the relation between thermal diffusion coefficient and thermal diffusion factor in binary mixture. The four candidates were checked analytically by two points: (1) it must be equal to the relation for binary mixture when the system can be regarded nearly as binary mixture, and (2) summation of thermal diffusion coefficients must be zero, and only the following passed the check:
where ρ is the total density, c the total molar concentration, D⁽²⁾_ij the binary diffusion coefficient, Mk and xk are molar weight and mole fraction of the k-th component, respectively. For 3-component argon 36-38-40 isotope mixture and for 4-component xenon isotope 129-131-132-134 mixture, the temperature and composition dependences obtained from this linear relation were equal to those from the thermal diffusion coefficients given by Hirschfelder et al.

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The process variables of the co-decontamination processes, such as flow rates and feed concentrations of elements involved, were optimized by using Genetic Algorithms (GAs). The concentration profiles and the objective function for a given flowsheet were calculated with the SOLE code. Because the mass balance of elements involved in a contactor is expressed in nonlinear simultaneous equations, derivatives of the objective function cannot be calculated explicitly. On the other hand, GAs require no derivatives of objective function and can be well applied to such a problem of optimization.
In the present study, two types of spent fuel for the optimization were considered. One was the spent fuel of LWR, and the other was that of FBR. In the latter case, because the concern for criticality and third phase formation becomes more important, a penalty term, which was a function of the maximum Pu concentration in aqueous phase, was incorporated into the objective function. In both the cases, optimal values obtained were well within the range of practicability and the average fitness of a generation increased steadily as the generation proceeded, which means that GAs are appropriate methods for these problems of optimization.

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Polycrystalline analcime film was prepared from hydrogels under hydrothermal conditions. The analcime film of about 200μm thickness built up on a porous alumina support at temperatures above 160°C, and the size and crystallinity of analcime increased with temperature. The thickness of analcime film increased with incubation time, and the growth rate at 180°C was faster than that at 160°C. The analcime film obtained was thermally stable at temperatures up to 700°C, and no structural changes were observed after treatment in nitric acid solutions below 0.01M. Analcime had an ion-sieve ability to large sized Cs⁺ ion, and Ag⁺ and Rb⁺ ions of small sizes were incorporated in analcime.

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The revision work of JENDL-3 has been made by considering feedback information of various benchmark tests. The main revised quantities are the resonance parameters, capture and inelastic scattering cross sections, and fission spectra of main actinide nuclides, the total and inelastic scattering cross sections of structural materials, the resonance parameters the capture and inelastic scattering cross sections of fission products, and the γ-ray production data. The revised data were released as JENDL-3.2 in June 1994. The preliminary benchmark tests indicate that JENDL-3.2 predicts various reactor characteristics more successfully than the previous version of JENDL-3.1.

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Transfer models used for environmental impact assessments are briefly reviewed focusing on a soil-plant system. The transfer models are categorized into two types based on their structures: equilibrium and dynamic models. The chronological development of each model type and the features of selected models are summarized. Trends and future needs for improvement of transfer models are discussed.

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