Nuclear Shipping Casks Research Articles

Mechanical Property Evaluation of Polyurethane Foam under Quasi-static and Dynamic Strain Rates- An Experimental Study

Polyurethane foams are widely used as thermal insulators and also as energy absorbers in radioactive material shipping casks. In view of this, an experimental study to observe the change in impact response of rigid polyurethane foam at different strain rates was conducted. For this purpose, uni-axial compression experiments were performed at quasi-static and dynamic rates of loading. The results reveal a significant change in mechanical properties of foam under compression at different strain rates. The response of foam gets stiffer with increase in strain rate, and densification (lockup) occurs well below the strains at which lockup occurs for foam deformed at quasi-static strain rates. Consequently, the energy absorption characteristics of foam are altered with change in strain rate. It is envisioned that nuclear industries could use this information for application of polyurethane foam as an impact limiter in nuclear shipping casks, without causing un-acceptable stresses in the cask structure.

Effect of γ irradiation on the impact response of rigid polyurethane foam

Abstract An experimental study to observe the change in impact response of rigid polyurethane foam due to γ irradiation is presented. The foam samples were irradiated using a 60Co based γ irradiator, γ Chamber 5000. Dynamic tests were performed on unirradiated and irradiated cubical foam specimens in a drop weight testing machine to characterize the mechanical properties. Structural characterization was performed using phase-contrast X-ray imaging and scanning electron microscopy (SEM). The results reveal a significant change in the dynamic response of polyurethane foam after irradiation due to change in structure. The response of foam gets stiffer in the initial linear phase, and densification (lockup) occurs well below the strains at which lockup occurs for an unirradiated foam. The ramifications of this study towards the application of polyurethane foam as an impact limiter in nuclear shipping casks are discussed.

A comparison of recent results from HONDO III with the JSME nuclear shipping cask benchmark calculations

The results of two calculations related to the impact response of spent nuclear fuel shipping casks are compared to the benchmark results reported in a recent study by the Japan Society of Mechanical Engineers Subcommittee on Structural Analysis of Nuclear Shipping Casks. Two idealized impacts are considered. The first calculation utilizes a right circular cylinder of lead subjected to a 9.0 m free fall onto a rigid target, while the second calculation utilizes a stainless steel clad cylinder of lead subjected to the same impact conditions. For the first problem, four calculations from graphical results presented in the original study have been singled out for comparison with HONDO III. The results from DYNA3D, STEALTH, PISCES, and ABAQUS are reproduced. In the second problem, the results from four separate computer programs in the original study, ABAQUS, ANSYS, MARC, and PISCES, are used and compared with HONDO III. The current version of HONDO III contains a fully automated implementation of the explicit-explicit partitioning procedure for the central difference method time integration which results in a reduction of computational effort by a factor in excess of 5. The results reported here further support the conclusion of the original study that the explicit time integration schemes with automated time incrementation are effective and efficient techniques for computing the transient dynamic response of nuclear fuel shipping casks subject to impact loading.

核燃料輸送容器の熱・構造計算コードの比較

There are many computer codes which could be applied to the design and analysis of nuclear material shipping casks. One of problems which the designer of shipping cask faces is the decision regarding the choice of the computer codes to be used. For this situation, the thermal and structural benchmark tests for nuclear shipping casks are carried out to clarify adequacy of the calculation results. The calculation results are compared with the experimental ones. This report describes the results and discussion of the benchmark test.

Analytical Puncture Study of Circular Metal Plates

An existing closed-form solution for large-deflection static responses of centrally loaded, rigid, perfectly plastic circular metal plates (with emphasis on steel plate cases) that are clamped (built-in) or simply supported at the edges is first modified to take into account the effects of elastic deformation and material strainhardening in an approximate manner. The modified theoretical solution is first shown to correlate very well with experimental results. Then it is applied in solving the quasi-static plate puncture problem in which the punch bar penetrates slowly into the plate. An analytical/experimental correlation study on punch force-deflection relationship and incipient plate puncture energy is made on newly obtained experimental data. Effects of variation of strainhardening parameter, boundary conditions and shear deformation on incipient puncture energy are studied, and plate puncture design curves are developed in the form of nondimensional incipient plate puncture energy as a function of punch diameter/plate thickness ratio for various values of punch diameter/plate diameter ratio. Application of these analytical techniques/design curves to the design of nuclear shipping cask plate components subject to regulatory puncture drop loading is also discussed.

Global Bending Response Analysis of Elastic and Viscoplastic Nuclear Shipping Cask Structures Subjected to Impact Loading

Within the framework of lumped mass upgraded beam theory in which rotatory and elastic shear deformation effects are considered, the title analysis is made for the case of large realistic lead-shielded, cylindrical stainless steel shipping casks equipped with end impact limiters. A computerized study developed elsewhere for the dynamic response analysis of elastic and elastic/viscoplastic beams and frames is first extended to include shear deformation and rotatory inertia effects and subsequently used in the cask impact response analysis study. Three types of impact limiter reaction force pulses are considered and three simplified analysis techniques (i.e., quasi-static, dynamic amplification factor and elementary beam analysis techniques) used in shipping cask design are evaluated. In particular, effects of shear deformation and rotatory inertia on impact responses and strain rate sensitivity effects on inelastic dynamic cask response behavior are studied. Appropriate guidelines are formulated for: 1) general use of these techniques in impact design analysis, and 2) treating strain rate sensitivity effects on material strength properties in conjunction with use of elastic, limit and elastic-plastic design analysis methods.