Spectral-Nodal Deterministic Methodology for Neutron Shielding Calculations using the X, Y - geometry Multigroup Transport Equation in the Discrete Ordinates Formulation

In this work, we present the most recent numerical results in a nodal approach, which resulted in the development of a new numerical spectral nodal method, based on the spectral analysis of the multigroup, isotropic scattering neutron transport equations in the discrete ordinates ($S_N$) formulation for fixed-source calculations in non-multiplying media (shielding problems). The numerical results refer to simulations of typical problems from the reactor physics field, in rectangular two-dimensional Cartesian geometry, $X, Y$ geometry, and are compared with the traditional Diamond Difference ($DD$) fine-mesh method results, used as a reference, and the spectral coarse-mesh method Green's function ($SGF$) results.

Calculation of the elasticplastic deformation of a solid body by multidimensional nodal method of characteristics

Описан многомерный узловой метод характеристик, предназначенный для численного расчета упругопластической деформации твердого тела в рамках модели Прандтля-Рейса с уравнением состояния небаротропного типа. В качестве критерия перехода из упругого в пластическое состояние применялось условие текучести Мизеса. Рассмотренный численный метод базируется на координатном расщеплении исходной системы уравнений на ряд одномерных подсистем с последующим их интегрированием с помощью одномерного узлового метода характеристик. Метод использован для расчета ряда одно- и двумерных модельных задач A multidimensional nodal method of characteristics is described. The method is designed to numerically calculate the elastoplastic deformation of a solid body within the Prandtl-Reis model with the non-barotropic state equation. The Mises flow condition was used as a criterion for the transition from an elastic to a plastic state. The considered numerical method is based on the coordinate splitting of the original system of equations into a number of one-dimensional subsystems. Then the resulting equations were integrated using a one-dimensional nodal method of characteristics. The proposed method allows calculating a number of one- and two-dimensional model problems. The results of calculations that employ the multidimensional node method of characteristics were compared with data calculated using the Godunov hybrid method in the framework of a model that did not take into account the contribution of potential elastic compression energy to the total energy of the medium. There are some discrepancies in the calculation results that occur at high speeds of interaction of the aluminum striker with the barrier, exceeding 500 m/s, which are associated with omission of the potential energy due to the elastic compression of the solid within the original Prandtl-Reis model

Numerical study of heat and mass transfer of a wall containing micro-encapsulated phase change concrete (PCC)

The aim of this work is to study the one-dimensional heat and mass transfer through a ceiling wall containing micro-encapsulated PCC (phase change concrete) under realistic climatic conditions based on meteorological data in Tunisia based on software EnergyPlus. This work deals with a numerical study based on the nodal method to predict the effect of integration of a layer of PCC on the thermal, mass behavior and on the thermal sensation of the occupant as well as on the reduction of the energy consumption for the summer and winter period associated with the composite envelope building.

Status on development and verification of reactivity initiated accident analysis code for PWR (NODAL3)

A coupled neutronics thermal-hydraulics code NODAL3 has been developed based on the nodal few-group neutron diffusion theory in 3-dimensional Cartesian geometry for a typical pressurized water reactor (PWR) static and transient analyses, especially for reactivity initiated accidents (RIA).The spatial variables are treated by using a polynomial nodal method (PNM) while for the neutron dynamic solver the adiabatic and improved quasi-static methods are adopted. A simple single channel thermal-hydraulics module and its steam table is implemented into the code. Verification works on static and transient benchmarks are being conducted to assess the accuracy of the code. For the static benchmark verification, the IAEA-2D, IAEA-3D, BIBLIS and KOEBERG light water reactor (LWR) benchmark problems were selected, while for the transient benchmark verification, the OECD NEACRP 3-D LWR Core Transient Benchmark and NEA-NSC 3-D/1-D PWR Core Transient Benchmark (Uncontrolled Withdrawal of Control Rods at Zero Power). Excellent agreement of the NODAL3 results with the reference solutions and other validated nodal codes was confirmed