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Modélisation neutronique des réacteurs à lit de boulets dans le code APOLLO2

Maurice Grimod 1
1 LPEC - Laboratoire de Protection d'Etudes et de Conception
SERMA - Service des Réacteurs et de Mathématiques Appliquées : DEN/DM2S/SERMA
Abstract : IN THIS THESIS, WE DEVELOP A NEW ITERATIVE HOMOGENIZATION TECHNIQUE FOR PEBBLE BED REACTORS, BASED ON A "MACRO-STOCHASTIC" TRANSPORT APPROXIMATION IN THE COLLISION PROBABILITY METHOD. A MODEL HAS BEEN DEVELOPED TO DEAL WITH THE STOCHASTIC DISTRIBUTION OF PEBBLES WITH DIFFERENT BURNUP IN THE CORE, CONSIDERING SPECTRAL DIFFERENCES IN HOMOGENIZATION AND DEPLETION CALCULATIONS. THE DEVELOPED METHOD HAS BEEN VERIFIED USING REFERENCE MONTE CARLO SIMULATIONS OF A SIMPLIFIED PBMR-400 MODEL. THE PEBBLES IN THIS MODEL ARE INDIVIDUALLY POSITIONED AND HAVE DIFFERENT RANDOMLY ASSIGNED BURNUP VALUES. THE APOLLO2 DEVELOPED METHOD MATCHES THE REFERENCE CORE KEFF WITHIN ±I100 PCM, WITH RELATIVE DIFFERENCES ON THE PRODUCTION SHAPE FACTORS WITHIN ±4%, AND MAXIMUM DISCREPANCY OF 3% AT THE HOT SPOT. MOREOVER, THE FIRST CRITICALITY EXPERIMENT OF THE HTR-10 REACTOR WAS USED TO PERFORM A FIRST VALIDATION OF THE DEVELOPED MODEL. THE COMPUTED CRITICAL NUMBER OF PEBBLES TO BE LOADED IN THE CORE IS VERY CLOSE TO THE EXPERIMENTAL VALUE OF 16890, ONLY 77 PEBBLES LESS. A METHOD TO CALCULATE THE EQUILIBRIUM REACTOR STATE WAS ALSO DEVELOPED AND APPLIED TO ANALYZE THE SIMPLIFIED PBMR-400 MODEL LOADED WITH DIFFERENT FUEL TYPES. THE POTENTIAL OF THE APOLLO2 METHOD WAS USED TO EVALUATE THE BIAS COMMITTED BY THE AVERAGE COMPOSITION PEBBLE APPROXIMATION. THE SPECTRAL DIFFERENCES BETWEEN THE PEBBLES BEING MOSTLY LINKED TO THE RESONANCE OF PU240, THIS BIAS IS IMPORTANT FOR THE PU LOADED CORE, WHERE DIFFERENCES UP TO ±10% ON THE POWER SHAPE FACTORS AND ON THE MAIN NUCLIDE DENSITIES ARE OBSERVED. BASED ON THE ACCUMULATED EXPERIENCE AT CEA, A COUPLED NEUTRONIC-THERMAL HYDRAULIC 3D CORE MODEL OF A PBR COULD BE BUILT.
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https://tel.archives-ouvertes.fr/tel-00728695
Contributor : Maurice Grimod <>
Submitted on : Thursday, September 6, 2012 - 1:48:18 PM
Last modification on : Tuesday, April 28, 2020 - 11:28:10 AM
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Maurice Grimod. Modélisation neutronique des réacteurs à lit de boulets dans le code APOLLO2. Modélisation et simulation. Université Paris Sud - Paris XI, 2010. Français. ⟨tel-00728695⟩

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