International Journal of Nuclear Energy Science and Engineering (IJNESE) Volume 5, 2015 www.ijnese.org doi: 10.14355/ijnese.2015.05.003
Analysis of the 2‐D C5G7 MOX Benchmark with VISWAM Code Arvind Mathur*1, Suneet Singh1, Suhail Ahmad Khan2, V. Jagannathan3 Department of Energy Science and Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, INDIA 1
Reactor Projects Division, Bhabha Atomic Research Centre, Mumbai‐400085, INDIA
2
Reactor Physics Design Division, Bhabha Atomic Research Centre, Mumbai‐400085, INDIA (Retired)
3
*1akmathur@iitb.ac.in Abstract The Indian nuclear power programme is being augmented with a variety of imported light water reactors (LWRs). Close interaction between the national labs, plant operators and educational institutions is required to meet the human resource requirements of this program. A neutronics code VISWAM for physics analysis of current and future power reactors is being developed as a part of the above long term goal. The overall plan is to develop a lattice code for generating few group cross sections and a diffusion theory based few group core solver for steady state and transient core calculations. As a first step towards this goal, we have taken up the development of a lattice burnup code. Initially, we used a combination of 1‐D multigroup transport for pincell and supercell calculations and 2‐D few‐group diffusion theory for assembly calculations. Although this method was fast and reasonably accurate for simple fuel assembly designs, we found that the power distribution errors were large in the vicinity of strong absorbers like burnable poison and control rod pins. We improved the solution method by using the 2‐D collision probability (CP) method for calculating the fluxes in each region and currents at each surface of a cell. Adjacent cells are coupled using interface currents at cell boundaries with double P2 (DP2) expansion of angular flux. The advantage of this method is that it can been extended for 2‐D full core solution of the neutron transport equation without spatial homogenization. We tested this code using the OECD/NEA 2‐D C5G7 MOX fuel assembly benchmark. The eigenvalue for the core calculation lies within 0.05% of the reference result. The average power distribution error is less than 1.0%. Keywords Integral Transport Theory; 2‐D Collision Probability; Interface Current; C5G7 MOX Benchmark
Introduction A neutronics code system VISWAM for physics analysis of current and future power reactors is being developed as a research and teaching tool. The overall plan is to develop a lattice code for generating few group cross sections and a diffusion theory based few group core solver for steady state and transient core calculations. We have started with the development of a lattice burnup code. In the first version of the code, the solution method used a combination of 1‐D multigroup transport and 2‐D few‐group diffusion theory for assembly calculations. This method was fast and reasonably accurate for simple fuel assembly designs. We tested the code using the LEU and MOX benchmark problems proposed by Yamamoto et.al. [1‐3] and noted that the power distribution errors were large in the vicinity of strong absorbers like burnable poison and control rod pins [4]. We therefore improved the lattice solution method by adopting a 2‐D collision probability (CP) method for calculating the fluxes in each region and currents at each surface of the cell. Adjacent cells were coupled using interface currents at cell boundaries with double P2 (DP2) expansion of angular flux. The DRAGON code has an option for using this method with double P1 (DP1) expansion [5]. In the COHINT code [6] the transport equation is solved by interface current method in X‐Y geometry with a four term expansion of angular flux. The circular fuel rod is modeled as square. In the VISWAM model, the geometry is treated exactly and six term expansion of angular flux is considered. In Section 2, we will briefly cover the equations and methods implemented in this code. With improvements in storage and computing capabilities, it is now feasible to attempt a direct solution of the transport solution for a core problem. We validated the VISWAM code using the OECD/NEA 2‐D C5G7 MOX fuel assembly benchmark [7].
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