Neptune: A system of finite element programs for three-dimensional nonlinear analysis

This paper describes the NEPTUNE system of finite element codes that is being developed to assist in the design, safety evaluation, and licensing of metal and concrete reactor structures subjected to static or transient mechanical loads. The implementations of (1) a quadrilateral plate element for concrete, (2) a family of interface elements to treat contact and/or impact between structures, and (3) a silent boundary element are highlighted. Terse descriptions of the remaining elements in the code are given. The solution of the static equilibrium equations are obtained with the dynamic relaxation algorithms, and the equations of motion are solved with the central difference algorithm. The wide range of applicability of the code system is demonstrated with four examples. The propagation of a wave through a silent boundary is first illustrated. Then the impact of a deformable cylindrical container against a rigid floor is simulated. The final two problems deal with structural safety evaluations. The transient response of a liquid metal reactor's head assembly is first described, and then, a numerical simulation of the response of a 16-scale reinforced concrete light water reactor, containment model to static overpressurization is presented.

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