THE SNAPKIN VI COMPUTER PROGRAM FOR SNAP REACTOR KINETICS CALCULATIONS

S>The computer program SNAPWN VI is described which solves the space- independent reactor kinetics equations with feedback equations representing the principal shutdown mechanisms in a SNAP reactor. Reflector delay effects are treated by a reflector group model. By using an alternate main program and two alternate subroutines, spatially dependert feedback effects may be considered. Printed, CRT, and punchcard output may be obtained optionally. Sample problems are demonstrated for both versions of the code. The equations and listings are included. (auth

Methodology to resolve the transport equation with the discrete ordinates code TORT into the IPEN/MB-01 reactor

This is an Accepted Manuscript of an article published by Taylor & Francis in International Journal of Computer Mathematics in 2014, available online: http://www.tandfonline.com/10.1080/00207160.2013.799668Resolution of the steady-state Neutron Transport Equation in a nuclear pool reactor is usually achieved by means of two different numerical methods: Monte Carlo (stochastic) and Discrete Ordinates (deterministic). The Discrete Ordinates method solves the Neutron Transport Equation for a set of selected directions, obtaining a set of directional equations and solutions for each equation which are the angular flux. In order to deal with the energy dependence, an energy multi-group approximation is commonly performed, obtaining a set of equations depending on the number of energy groups. In addition, spatial discretization is also required and the problem is solved by sweeping the geometry mesh. However, special cross-sections are required due to the energy and directional discretization, thus a methodology based on NJOY99 code capabilities has been used. Finally, in order to demonstrate the capability of this method, the 3D discrete ordinates code TORT has been applied to resolve the IPEN/MB-01 reactor.The authors wish to thank Departamento de Engenharia Nuclear da UFMG and Instituto de Pesquisas Energeticas e Nucleares for all data and support.Bernal García, Á.; Abarca Giménez, A.; Barrachina Celda, TM.; Miró Herrero, R. (2014). Methodology to resolve the transport equation with the discrete ordinates code TORT into the IPEN/MB-01 reactor. International Journal of Computer Mathematics. 91(1):113-123. doi:10.1080/00207160.2013.799668S113123911Rhoades, W. A., & Simpson, D. B. (1997). The TORT three-dimensional discrete ordinates neutron/photon transport code (TORT version 3). doi:10.2172/58226

Maximally incompressible neutron star matter

Relativistic kinetic theory, based on the Grad method of moments as developed by Israel and Stewart, is used to model viscous and thermal dissipation in neutron star matter and determine an upper limit on the maximum mass of neutron stars. In the context of kinetic theory, the equation of state must satisfy a set of constraints in order for the equilibrium states of the fluid to be thermodynamically stable and for perturbations from equilibrium to propagate causally via hyperbolic equations. Application of these constraints to neutron star matter restricts the stiffness of the most incompressible equation of state compatible with causality to be softer than the maximally incompressible equation of state that results from requiring the adiabatic sound speed to not exceed the speed of light. Using three equations of state based on experimental nucleon-nucleon scattering data and properties of light nuclei up to twice normal nuclear energy density, and the kinetic theory maximally incompressible equation of state at higher density, an upper limit on the maximum mass of neutron stars averaging 2.64 solar masses is derived.Comment: 8 pages, 2 figure

Updated version of the DOT 4 one- and two-dimensional neutron/photon transport code

DOT 4 is designed to allow very large transport problems to be solved on a wide range of computers and memory arrangements. Unusual flexibilty in both space-mesh and directional-quadrature specification is allowed. For example, the radial mesh in an R-Z problem can vary with axial position. The directional quadrature can vary with both space and energy group. Several features improve performance on both deep penetration and criticality problems. The program has been checked and used extensively

Effectiveness of three rebalance methods in deep penetration problems. [LMFBR]

The space-rebalance method brought important new capability to discrete-ordintes calculations by using an easily-solved procedure. Later, diffusion synthetic acceleration used the diffusion equation as the auxiliary equation. Application of this new approach has been slow, partially due to concomitant restrictions. Aull et al showed a reformulation which brought compatibility with weighted-difference and negative-fixup schemes. Miller showed that the differential forms of the conventionl space rebalance (CRB) pand the newer methods could be derived from a common framework. This paper will, similarly, cast the difference form of Aull's consistent diffusion acceleration (CDA) into the same form as CRB and will indicate a third approach suggested by this comparison. Variations of these methods will be tested on deep-penetration problems

New weighted-difference formulation for discrete-ordinates calculations

One of the shortcomings of the method of discrete ordinates has been a tendency to generate negative estimates of inherently positive fluxes due to over-extrapolation. A new formulation presented here shows a repair of the shortcomings of previous methods to solve this problem by the introduction of an arbitrary parameter, theta. The theta-weighted difference method is seen as giving results as accurate as any while possessing the desired smooth convergence. The exact choice of theta is unimportant. 4 figures, 2 tables. (RWR