New methods implemented in TRIPOLI-4. New methods implemented in TRIPOLI-4. J. Eduard Hoogenboom Delft University of Technology

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1 New methods implemented in TRIPOLI-4 New methods implemented in TRIPOLI-4 J. Eduard Hoogenboom Delft University of Technology on behalf of Cheikh Diop (WP1.1 leader) and all other contributors to WP1.1 1

2 WP1.1: Advanced Monte Carlo techniques General goal: Nurisp WP1.1: To optimise and implement essential extensions for MC calculations with TRIPOLI4 TRIPOLI4 is the basic Monte Carlo code on the Nuresim platform Partners: CEA, TUD, KIT Users Group: Demokritos 2

3 Advanced Monte Carlo techniques Essential extensions: Coupling with TH codes Time dependence Future final goal: Reactor core safety analysis by MC HPMC project 3

4 T1.1.4: Dynamic Monte Carlo Goal: Development of the basic Monte Carlo techniques for long-time kinetic and dynamic Monte Carlo Time dependence is intrinsic to Monte Carlo simulation, but time scales can vary from 10-5 s (neutron) to 10 2 s (precursor) 4

5 Dynamic Monte Carlo Prompt neutrons have a very short time scale: ~ 10-4 s A chain of successive fissions : ~ 10-2 s From < 1 % of fission neutrons a precursor of a delayed neutron is generated Decay times of precursors: s This slow behaviour allows a reactor to be controlled by control rods! 5

6 Dynamic Monte Carlo Very different time scales gives a problem in Monte Carlo simulation Power is generated continuously during a chain of prompt neutrons The prompt chain finally dies out For a critical reactor during such a chain one precursor is generated on the average 6

7 T1.1.4 Effects of different time scales 7

8 Results of Dynamic Tripoli4.7 Infinite lattice of PWR fuel assemblies with CRs complex geometry, continuous energy (near) critical system 8

9 Results of Dynamic Tripoli4.7 achieved by TUD 9

10 T1.1.2 Speedup of convergence Obtain (approximate) fission source distribution from CRONOS Convert to input for TRIPOLI4 to start MC iterations 10

11 flux Local flux convergence N J achieved by CEA number of cycles 11

12 T1.1.5: McCad Convert CAD model to TRIPOLI4 input CAD model with 129 solids achieved by KIT TRIPOLI-4 geometry generated by McCad 12

13 T1.1.4: MC-TH coupling Essential for realistic core calculations Various problems related to Monte Carlo Cross section data at various temperature needed Various techniques developed interpolation using pseudo nuclides direct interpolation generation of requested σ(t) 13

14 T1.1.1: TRIPOLI4+NJOY for temperature dependent calculations with different media at different temperatures cross sections at all requested temperatures need to be present If not: new option in TRIPOLI4 can call NJOY for generating necessary cross sections achieved by CEA 14

15 T1.1.4&6: Coupled MC-TH Benchmarking MC-TH No suitable benchmark available Own benchmark definition BWR pincell problem Axially varying enrichment 0.71 % 3.3 % 3.7 % 3.3 % 0.71 % Fuel pin top reflector 0.2 m Hauteur (cm) 0,2 m 370,80 fuel 3.8 m 3,8 m 355,37 309,02 154,51 15,44 0,00 0,71 2,05 0,71 bottom reflector 0,2 0.2 m C1 3,8 m 15

16 T1.1.6: Benchmarking MC-TH Axial power distribution achieved by TUD, KIT, CEA 16

17 WP1.1: Advanced Monte Carlo Conclusions on Monte Carlo developments All deliverables ready by January 2012 Major steps forward MC-TH time dependence various other improvements Further work or validation necessary Extension to full-core application in project 17

18 WP1.1: Advanced Monte Carlo Thank you for your attention 18