1. Neutronic simulation of a European Pressurised Reactor O.E. Montwedi, V. Naicker School of Mechanical and Nuclear Engineering North-West University Energy Postgraduate Conference 2013 Cape Town, South Africa

2. Introduction Flow chart of the system analysis research

3. Introduction EPR AREVA NP design GEN III+. Finland (Olkiluoto ), France (Flamanville), China (2 Units Taishan). Licencing in USA and UK. Codes available for neutronic analysis Diffusion codes > Solve neutron diffusion equation to obtain the neutron flux. > DYN3D neutron kinetics code, NEM (Nodal Expansion Method). Deterministic codes > Solve the Boltzmann transport equation. > Based mostly on discrete ordinate methods. Stochastic codes > Uses stochastic methods to simulates particle transport. > Capability to model very complex geometries. > E.g. Monte Carlo N-Particle 5 (MCNP 5).

4. Introduction Flow chart of the MCNP code for power distribution calculation

5. Aim Develop a 3D MCNP EPR Neutronic Model. > Build MCNP input deck. > Establish convergence of the model. Calculate of the flux and fission powers.

6. Core model description  Core 17 X 17 core. 241 fuel assemblies. Heavy reflector: stainless steel sheets. Core barrel : stainless steel. Moderator : H 2 O. RPV : stainless steel.  Assembly 17x17 Fuel assembly. 23 Guide tubes. 1 Instrumentation tube. 265 Fuel rods.

7. Results and Discussions Figures on top 500 n/cycle and 100 000 n/cycle. Results above shows that the more source neutron per cycles and source point you have the quicker the convergence in both Keff and Source entropy. If you want reliable results we should discard at least 200 – 300 cycles. B. Brown Forrest, “A review of Monte Carlo criticality calculations–Convergence, Bias, Statistics” Los Alamos National Laboratory (2009).

8. Results Axial neutron flux distribution (0 0 0) Flux at the top and bottom of the core is low as expected because of the stainless steel structures present. Flux at the central region of the core is reduced by incorporation of burnable absorbers(Gd2O3), this increases burn-up.

9. Results and Discussions Axial power distribution (0 0 0) As expected the power is distributed similar to the flux distribution. Power at the central region of the core is reduced by incorporation of burnable absorbers(Gd 2 O 3 ), this increases burn-up reduce axial leakage.

10. Conclusion and further work  Model has converged and this allows for stable and reliable results  Multi group flux and fission power is obtained and the distributions follows expected trends.  The results resemble the EPR and PWR design differences and advancements.  Further work Identification of the hot channel of the core. Calculation of control rods worth. This work is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation.