The code EVENT (EVEn parity Neutral particle Transport) is the culmination of over 10 years of research at Imperial College, London in applying the finite element method to radiation transport problems.

EVENT solves the self-adjoint second order form of the transport equation using a variational finite-element formulation. EVENT is capable of solving multi-group steady-state and time-dependent problems in both forward and adjoint modes with anistropic scattering. Spherical harmonic basis functions are used to expand the angular variable in the transport equation allowing for both full PN or SPN solutions. A Hybrid ray-tracing algorithm has also been implemented in EVENT to allow the modelling of near transparent media. A parallel version of EVENT has also been developed over the past few years. A fast and economical moment-by-moment (MBM) algorithm has been developed and implemented in EVENT based on a preconditioned symmetric conjugate gradient (PCG) iterative procedure for the solution of large systems of linear equations. An extension of the MBM solution algorithm to parallel processing has been achieved via domain decomposition techniques.

EVENT is written in standard Fortran 77 and consists of approximately 50,000 lines of code. System dependent routines have been kept to a minimum which ensures easy portability to main computing systems. The PVM and MPI libraries are used for parallel processing. At present only a fully developed Unix based implementation exists. EVENT has run serially and in parallel on a variety of platforms including: Unicos, Digital Unix, Solaris, Irix and VMS.

A general purpose mesh generator and data preparation code called GEM has been developed to enable the automatic generation of the finite-element mesh and input data for EVENT. A graphical processing tool called PLOTTER has also been developed to aid in the visualisation of the finite element mesh and the plotting of results from EVENT.

Current research on EVENT centres on the development of multilevel or hierarchical preconditioners, refinement of the hybrid ray-tracing algorithm and the development of automatic locally adaptive meshing and angular schemes. The long-term of goal of the development work on EVENT is to make it fully self-adaptive in both space and angle with the numerical discretisations tailoring themselves to the physics of the problem. This would have the dual advantage of making the best use of the available computational resources whilst freeing the non-specialist user from the burden of having to decide the best spatial and angular discretisation for a given problem.

Current applications of EVENT include

  • The criticality assement of fissile solutions in which EVENT has been linked with our own in-house multi-phase CFD finite element code FLUIDITY to study non-linear reactivity feedbacks due to fluid heating, change of geometry and bubble formation.
  • Calculating the fuel rating of MAGNOX and AGR fuel assemblies.
  • General radiation shielding problems.
  • Providing fast forward transport solutions for the reconstruction of the optical properties of a biological medium with scattering (near infrared optical tomography). Modelling radiation exchange within and between cloud structures. Nuclear down-well logging.

Brief Summary of EVENT capablilites:

  • Arbitrary Geometries:
    • 1D slab/spherical/cylindrical
    • 2D x-y/r-z (using unstructed finite-element meshes)
    • 3D x-y-z (using unstructed finite-element meshes)
  • Isoparametric Elements (up to quintic):
    • 2d: Triangles, Quadrilaterals,
    • 3d: Tetrahedra, Wedges, Hexahedra.
  • Odd/Even PN and SPN solutions
  • Hybrid finite-element ray-tracing for void regions
  • Time dependence:
    • Source Driven
    • Self-adpative Time Step Size
    • Forward and/or Ajoint Solutions
    • Multigroup Anisotropic Scattering
    • Delayed Neutrons
    • Choice of Solution Methods:
      • Gaussian (Direct)
      • Moment-by-Moment PCG
      • Moment-by-moment Gaussian
      • Parallel Domain Decomposition