No abstract available

No abstract available

[en] The concept of a fuel fabrication system with Erbia bearing high burnup fuel has been proposed. The Erbia is added to all fuel with over 5% ²³⁵U enrichment to retain the neutronics characteristics to that within 5% ²³⁵U enrichment. There is a problem of the prediction accuracy of the neutronics characteristics with Erbia bearing fuel because of the short of experimental data of Erbia bearing fuel. The purpose of the present work is to reduce the uncertainty. A new method has been proposed by combining bias factor method and the cross section adjustment method. The cross section adjustment method is applied only to erbium (Er). And the neutronics characteristic except Er is improved by the bias factor method. The main contribution of Er is neutron capture. To evaluate the accuracy of k_eff, the Erbia worth is the suitable experimental data. Therefore, the prediction accuracy of neutronics characteristics of Er is improved through the cross section adjustment using the sample worth. In the case of the blending machine (H/U=0) for the fuel fabrication process, the uncertainty reduction, which shows the rate of reduction of uncertainty, of the k_eff is 0.604 by the present method and 0.555 by the conventional bias factor method. In the case of H/U=1.0, the uncertainty reduction by the present method was 0.760. Using the bias factor method, the uncertainty reduction was 0.593. The prediction uncertainty was significantly reduced by the present method. For the PWR core, the uncertainty reduction, which shows the rate of reduction of uncertainty, of the k_eff is 0.865 by the present method and 0.801 by the conventional bias factor method. Thus the prediction uncertainties are reduced by the present method compared to the bias factor method. (author)

[en] The decomposition temperature of CeN, Usub(0.5)Cesub(0.5)N and Usub(0.75)Cesub(0.25)N has been measured as a function of nitrogen pressure. Thermodynamic analysis based on the reaction, in which the solid solution, Usub(1-x)Cesub(x)N, decomposes into Usub(1-x)Cesub(x)(1) and 1/2 N₂(g), results in a very simple relation. The influence of solubility of nitrogen in Usub(1-x)Cesub(x)(1) has been also taken into consideration. The present experimental data are in good agreement with the equation derived from the present thermodynamic analysis. (Auth.)

[en] The optimization of laser-induced forward transfer (LIFT) process using laser ablation of thin film and the evaluation of the dependence in laser spot size on the resolution of deposited material are reported. Ni thin film of several hundred of nanometer thickness, which is deposited on fused silica substrate, was irradiated by single pulse of KrF excimer laser (wavelength: 248 nm, pulse width: 30 ns), and transferred to a Si acceptor substrate. Images of the plume, which were photographed using image intensified CCD camera, indicated the cause of transfer of particles. The deposited material with clear contour was obtained under the condition that thin film was in contact with an acceptor substrate to inhibit the transfer of particles which were generated by laser irradiation. The resolution of a deposited material tended to be improved as the size of laser spot became smaller

[en] In this work, a simple constitutive model simulating the dynamic behavior of elastomeric isolation devices is proposed. This work is part of research activities undertaken at ENEA (Italian National Commission for the Nuclear and Alternative Energies Sources) to analyze the behavior of isolation systems and isolated structures, in view of possible application to the industrial plants, including the innovative nuclear reactors. The research includes both experimental tests and theoretical studies. The activities in this latter field are the following: implementation of high damping elastomeric material constitutive law and its modeling with refined finite element computer codes; simple modeling (1-degree-of-freedom) of the single isolating element; and modeling of isolated structures. In this report, the first results of 2nd and 3rd activities are summarized

[en] A cold trap regeneration is very important because of the expected high hydrogen source from the steam generator. The replacement of cold trap, in case of plugging by accumulation of such hydrogen precipitates, is undesirable. The cold trap regeneration testing programs were performed. Presented cold trap regeneration method, by making use of hydrogen transfer from sodium surface to sweep argon gas, appears to be the simplest and least expensive. Experimental programs can be divided into the following groups. Test on hydrogen evolution to the cover gas method. Test on dissolution characteristics of cold trap. Test on development of high efficiency and long life sodium mist trap needed for the closed sweep gas system. The test results indicate that the regeneration system of cold trap is enough practical and available

[en] Decomposition pressure-temperature relations have been determined experimentally for YN and Usub(1-x)Ysub(x)N (x = 0.25, 0.5, 0.75). These results agree well with theoretical equation: log psub(N₂)[Usub(1-x)Ysub(x)N] = (1 - x) log psub(N₂)[UN] + x log psub(N₂)[YN], which may be derived from thermodynamic considerations of the decomposition reaction of Usub(1-x)Ysub(x)N based on the reaction: Usub(1-x)Ysub(x)N(s) = Usub(1-x)Ysub(x)(1) + 1/2 N₂(g). Statistical thermodynamic calculations based on the linearity of the isotherms in the log psub(N₂)[Usub(1-x)Ysub(x)N] vs. YN mole fraction show that the interaction between U and N and that between Y and N in Usub(1-x)Ysub(x)N may be attractive, having the same order of magnitude. (Auth.)

No abstract available

[en] In this report the experience gained in seismic re-evaluation of an old NPP (Trino Vercellese) is described. This PWR plant was not seismically designed. The main purpose of the upgrading, from the point of view of the Italian Directorate for Nuclear Safety - ENEA/DISP, was to have guaranteed the plant capability of achieving and maintaining a safe cold shutdown condition after a SSE seismic event. The main steps of the seismic review are discussed: definition of the new input motion; selection of structures, systems and components essential for a safe cold shutdown; definition of Codes and evaluation methods; seismic qualification of systems and components. Finally some modifications of a number of plant systems are described together with economical aspects. (author)