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This paper presents some results of experiments which simulate the structural dynamic response of a LMFBR primary coolant boundary to a hypothetical core disruptive accident (HCDA) based on scale models and high explosives. It was noted that high explosives are no longer a good simulant of the HCDA. However, the main purpose of the program, which included this experiment, is not to experimentally predict the dynamic response of the reactor structure at the HCDA, but to validate computer codes, which describe the pressure wave propagation and damage process in the reactor structures, using data obtained from these model experiments. The experiments were undertaken using many 1/15 scale simple models of the reactor vessels and internal structures, as well as 1/15 and 1/7.5 scale complex models of the interim design of prototype LMFBR ‘MONJU’. Simple model experiments involved a series of shock tests using pentolite to investigate the configuration effects of the vessel restraining section, the dipped-plate effect and the core barrel effect, respectively.

This paper presents a discussion on the model experiments results for reactor structure dynamic response on FBR hypothetical core disruptive accident (HCDA) and the results of analysis using the dynamic response analysis code under experimental conditions. The purpose of this study is to clarify experimentally the dynamic response by use of scale models, as well as to attempt to confirm and improve the dynamic response analysis code on the basis of experimental data. The experimental results have clarified the inner barrel effects on reactor vessel deformation and its behavior due to a impact load. On the other hand, dynamic analysis was made of the 1/7.5 scale complex model by a dynamic response analysis code “PISCES-2DL”, using the explosive combustion characteristics as inputs. Obtained values were compared with experimental values. Results showed that this method was fairly capable of evaluating radial deformation behavior in lower cylindrical parts of the vessel.

This paper presents an experimental and analytical study on pressure pulse propagation phenomena in a plastically deforming pipe filled with water. The simple and well-defined experiments have been performed in order to provide the fundamental data to verify a two-dimensional fluid-structure interaction code. The experimental facility consists of a test pipe and a pulse gun filled with water at room temperature. The pressure pulse was generated in the pulse gun by low velocity SK explosive, high velocity pentolite or a low energy detonator. Experiments have been performed on 3 m long, 16 cm OD and 0.287 cm thick stainless steel-316 pipe both with and without elbow section. Transient pressure, transient strain and plastic deformation are measured when the pressure pulse propagates along the test pipe which is jointed rigidly to the pulse gun. On entering the test pipe, the pulse attenuates rapidly to the yield pressure of the pipe (14 MPa) in about 40 cm. Large plastic deformation occurs over wider range in low velocity explosive experiments than high velocity explosive experiments. Peak pressure reduces in the elbow section more in the high velocity explosive experiments than the low velocity explosive experiments. The experimental results have been analyzed by using a two-dimensional code. The comparison between experiment and prediction for the pressure pulse propagation behavior shows fairly good results. However, the strains are 30–100% over-estimated by the code. This discrepancy is attributable to the influence of the strain rate on stress and the limitation of the calculational model for simulating the detailed structure of the test facility.

This paper presents a parametric analysis of the creep buckling of a shallow spherical shell subjected to uniform external pressure using the finite-element incremental method. Axisymmetric creep deformation analysis is first performed to obtain pre-buckling behavior by the time incremental method. The buckling modes considered are both bifurcation and axisymmetric snap-through types. Fourier expansion technique is conveniently employed to construct the stiffness matrices corresponding to asymmetric bifurcation as well as axisymmetric snap-through modes of deformation. The critical time for creep buckling is defined by the time at which either stiffness matrices corresponding to the axisymmetric or asymmetric modes lose their positive definiteness. The critical times and the buckling modes are obtained over a fairly wide range of the geometric parameters pertaining to shallow spherical shell subjected to uniform external pressure.

A summary is given of topics appearing in papers and discussions presented at the 2nd International Conference on Structural Mechanics in Reactor Technology (SMiRT) held in Berlin, at the Post-Conference Meeting on Computational Aspects of the Finite Element Method held in Stuttgart, and at the 2nd International Conference on Pressure Vessel Technology (PVT) held in San Antonio.The review also covers a discussion meeting on containment design aimed at resistance against air craft crashes and explosions held at the Institut Reaktorsicherheit (IRS) and other pertinert information from several organizations.

A finite element method is presented, which deals with structures subjected to both high temperatures and neutron irradiation. The material effects discussed in this paper include the usual thermo-elastoplastic effects, thermal and irradiation-induced creep and swelling due to the fast neutron fluence. Heat conduction equations and equilibrium equations are derived by assuming a specific form of free energy together with the thermodynamic laws, von Mises yield criteria and the associated flow rule. To demonstrate the effectiveness of the present formulation, the transient creep analysis of a three-dimensional solid subjected to creep effect is presented.

This paper concerns the method of calculation and solution using the superposition technique of analytic and finite element solutions, which is applied to elastic-plastic plane problems. The incremental form of the principle of virtual work is employed to derive the equations, from which the nodal displacements of the finite elements together with the generalized displacements of the analytic solution are calculated simultaneously. Several example problems are solved for elastic-plastic material with the use of the von Mises yield criteria and the associated flow rule. It is concluded that the present method is so effective as to give enough accuracy in strain concentration problems with small numbers of elements.

This paper is a review of the recent researches performed and planned in Japan relevant to the structural integrity of the pressure boundary in light water reactor designs. Various aspects of relevant work on materials, pressure vessel and piping models are described.

Nuclear power generation has been spotlighted as a substitute for petroleum. Efforts are being exerted for the development of more reliable nuclear power plants. This paper describes the present status of such development activities in Japan, especially to enhance reliability of non-destructive flaw detection and to improve component integrity through the cooperative efforts of experts in materials, structural design, fracture mechanics, fabrication and non-destructive examination.

As a recently results of the irradiation test, it has been found that the brittleductile transition temperature shifts to higher temperature for the structural steels when these are irradiated. Therefore, the problem of the brittle fracture of the reactor pressure vessel is now emphasized from the standpoint of the safety of reactor operation.This paper describes the theoretical and experimental studies on the neutron irradiation brittleness both in Japan and other countries. The paper also points out the some problems encountered in the irradiation tests.

The stress concentration problem of thin elastic plates is one of the classical problems in the theory of elasticity, and since E. Goursat's work on the complex variable representation of stress functions in plane elasticity problems, much work has been done all over the world, and Muskhelishvili and others have established the unified theory on the two-dimensional elasticity problems. Unfortunately, however, the existing theoretical solutions obtained along this line are quite limited for the practical purpose and the development of a more practical method of analysis is definitely required. It seems that the energy methods will provide the alternative procedure powerful enough to treat the more practical problems although actually not attempt along this line has been made. In this paper, a first effort is made in the application of energy methods to the stress analysis of a perforated rectangular plate, the result of which is found consistent with the famous Howland's solution on the perforated plate strip problem and some test results.

From the viewpoint of the three-dimensional theory of elasticity, a direct method of solution for the natural vibration of a circular cylindrical shell is formulated based on the principle of virtual work. In the present method of solution, all the assumptions, on which the majority of existing theories are based are abandoned, and the vibration characteristics of a circular cylindrical shell with arbitrary thickness to curvature ratio will be studied in the unified way. In a numerical analysis influences of the length-curvature as well as thickness-curvature ratios are extensively studied for various cases of geometrical boundary conditions.

The convergence of a mixed finite element scheme for plate bending, previously proposed by the present authors, is discussed on the basis of functional analysis. First, the outline of the formulation is presented with some mathematical preliminaries. Then, several kinds of energy inequalities are established to assure the stability of the approximate solution. Thus, the rate of convergence may be obtained by the evaluation of the degrees of the completeness and consistency of the employed shape functions. Some remarks are also given with respect to the extension of the method to initial value problems.

The First International Conference on Structural Mechanics in Reactor Technology was held in Berlin, Germany, 20-24 September 1971. The purpose of the Conference was to bring together engineers and scientists actively engaged in structural mechanics problems in the field of reactor technology to meet with fundamentalists in the general field of engieering mechanics and to present and discuss applied and fundamental papers on structural mechanics problems in reactor technalogy.The Conference was organized by the Bundesanstalt fOr MaterialprOfung (BAM), Berlin and Commission of the European Communities, Brussel, in collaboration with cooperating establishments and sponsoring societies. About 800 participants attended and some 340 papers were presented. These were classified into twelve divisions.A: Opening Session, B: Power Reactor Development and Structural Mechanics, C: Fuel and Cladding, D: Fuel Elements, E: Shock and Vibration Analysis of Reactor Components, F: Structural Analysis of Core Support and Coolant Circuit Structures, G: Steel Pressure Vessels, H: Prestressed Concrete Pressure Vessels, J: Analysis of Shell Structures, Containment, K: Seismic Response Analysis of Nuclear Power Plant Systems, L: Thermal and Mechanical Analysis, M: Design, Reliability Methods.

Based on Hellinger-Reissner's variational principle, a rectangular finite element for plate bending is derived with bilinearly varying deflection and incompletely linear moments. This method is an example of the mixed method first proposed by Herrmann, where both displacement and stress are adopted simultaneously as fundamental variables. Because continuity conditions required on the fundamental variables are much relaxed compared with compatible models, suitable shape functions can be easily derived and calculation of the element matrix can be performed by hand. The explicit expression of the element matrix for general orthotropic plates is presented in this paper. A few simple test problems are computed in order to demonstrate the accuracy of the present model, and it is shown that it gives improved results compared with Herrmann's triangular element. Convergence is also assured when suitably small mesh sizes are adopted, and this element can be utilized in general practical problems.

The formulation of the simplified hybrid displacement method for plate bending is given systematically with some extension made to allow for the discontinuity of deflection field. Eight types of finite elements are developed utilizing this principle. They are tested numerically with static, vibration and stability problems of thin elastic plates. The results obtained are in general satisfactory, thus ensuring the feasibility of the method.

During construction of a reactor steel pressure sessel, the material may be subjected to thermal treatments which have serious effects on the quality of the material. This paper describes the results of studies carried out to investigate the effect of various fabrication thermal histories on brittle, ductile and fatigue fracture properties of A302B steel and its welds. Generally speaking, through a proper thermal history consisting of treatment for hot forming, quench and tempering, stress relief annealing at 625°C, deterioration of materials in the final state of thermal treatment can be practically prevented.

The finite element method is applied to the axisymmetric buckling of shallow spherical shells under uniform external pressure. In order to analyze the nonlinear behavior of shells with sufficient accuracy and efficiency, the simple load incremental method is modified by introducing the mid-increment stiffness matrix and residual load correction. The analysis is performed on a fairly wide range of the geometric parameter α to obtain pressure-deflection curves in both pre-and post-buckling states. The results appear generally satisfactory, at least up to the early stage of post-buckling. In particular, the upper and lower buckling pressures are obtained in excellent agreement with known analytical solutions.

This paper describes the main results of the examination carried out by the Advisory Committee on Reactor Safeguards (ACRS) to evaluate the safety of the First Nuclear Ship in Japan. After analyzing the hazards in various cases of ship and reactor accidents, the ACRS agreed that the safety of the ship could be secured. The results of a safety analysis on NS Savannah analyzed in accordance with the guide of Japan AEC is also presented.