Suhail Ahmad Khan

IAEA CRP Benchmark of Kalinin VVER-1000 NPP: An Analysis Using EXCEL-TRIHEX-FA Code System

Two units of VVER-1000Mwe reactors are in an advanced stage of construction at Kudankulam, Tamilnadu, India. With a view to assess the capability of analyzing the physics characteristics of VVER cores, the IAEA CRP benchmark problem of Kalinin VVER-1000 MWe NPP [1] is studied using the indigenous code system EXCEL-TRIHEX-FA [2,3]. The lattice burnup code EXCEL is based on a combination of 1-D multigroup transport theory and 2-D few group diffusion theory. Nuclear data in 172 group WIMS-D format based on JEFF-3.1 [4] has been used in the present analysis. The core level calculations are performed using the code TRIHEX-FA which solves the 3-D multigroup diffusion equation using the finite difference method with fine triangular meshes. Power dependent feedback models for xenon, Doppler, coolant temperature and density values have been incorporated in TRIHEX-FA. Keff for the critical soluble boron concentration, assembly power distribution and axial power distribution are calculated as a function of fuel cycle burnup. In the present paper, lattice level results are compared with the results of other participants reported in Ref. [1]. The results of core level calculations have been compared with the experimental data provided [1].Copyright

Rotational Symmetry Boundary Condition in Current Coupled Whole Core Pin by Pin Transport Theory Code

The advances in computer processing power have made it possible to perform a detailed pin by pin calculation of the whole core. The methods based on response matrix are being used to perform whole core transport calculations. This includes the current coupled methods based on 2D collision probability (CP) and method of characteristic (MOC). The basic approach in the whole core transport theory methods is not to homogenize the lattice cells and subdivide each cell location in the fuel assembly (FA) into finer regions. The coupling of lattice cells within the assembly and assembly to assembly coupling can be achieved using interface currents. Due to very fine discretisation of the lattice structure and large core size, the physical memory requirements for the whole core simulations are huge. This requirement is compounded if ultra-fine discretisation of energy domain is also considered. When there is an inherent symmetry one can solve for the symmetric portion of the core, thereby save both memory and computational time. Rotational symmetry boundary condition in the whole core is normally considered. Application of this boundary condition gets very complicated when the whole core is modeled by a pin by pin approach. The present paper describes the methodology to apply the rotational symmetry boundary condition in the core discretized with complex microstructures of various heterogeneous cells of the problem.

Application of high performance computing in lattice physics code VISWAM

We have developed a reactor physics lattice burnup code, VISWAM, for generating five group parametric database of LWR fuel assemblies. This database is used by core solvers that determine the neutronic characteristics of a nuclear power reactor. The sequential version of the VISWAM code used to take about ten days for generating the parametric database of all the fuel types of a particular reactor design. Subsequently, we developed a parallel version of the code using OpenMPI that reduced the time required for parametric database generation to a few hours. In this paper we give a brief description of the VISWAM code and the way parallel processing was used to speedup the code on a cluster.