exotic nuclei structure and reaction noyaux exotiques ... - IPN - IN2P3

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MURE: MCNP Utilities for Reactor Evolution IPNO Participation: J. Brizi, S. David, O. Méplan, J. N. Wilson Collaboration : LPSC Grenoble L’équipe MURE de l’IPN travaille sur la simulation de réacteurs nucléaires innovants et sur les scénarios associés. Les réacteurs rapides sont sans doute amenés à jouer un rôle dans le futur, du fait de leur capacité d’une part à atteindre la régénération et réduire ainsi d’un facteur 100 la consommation de minerai d’uranium, et d’autre part à recycler les actinides mineurs et réduire ainsi la charge thermique et radiotoxique des déchets produits. Dans ce cadre, nous effectuons des études sur les réacteurs rapides refroidis au sodium, en envisageant par exemple l’utilisation d’un combustible au thorium dans divers scénarios innovants. Introduction Currently there is a renewed interest in the expansion of the role of nuclear power for energy generation due to its lack of CO 2 emissions (which contribute to global warming), its economic viability, and its potential for energy security and independence. The future of nuclear energy may require breeding (reduction of uranium consumption) and optimized waste management. Innovative technologies have to be explored in order to reduce considerably the ore consumption and the associated waste production. Sodium-cooled fast reactors seem to be the most achievable technology in the coming decades, and can play an important role to launch the generation 4 technologies. However, the standard sodium-cooled reactors face to the problem of the positive void reactivity and a major Minor Actinides (MA) production if transmutation is not considered. In this context, we perform neutronic studies on innovative (or evolutive) sodium-cooled reactors. These studies are based on MURE (MCNP Utility for Reactor Evolution), a C++ object-oriented evolution code that couples the Monte-Carlo transport code MCNP with a fuel depletion code under given conditions. Different configurations of a fast sodium cooled reactor (SFR, with a total power of 1.45 GWe) are investigated, using U/Pu or Th/U cycle, with or without minor actinides transmutation. A self-breeding Th/U configuration has been found, using thorium blankets, which allows reducing significantly sodium void reactivity. MURE Numerical studies of a reactor's neutronics can be based on deterministic codes or Monte Carlo codes. The advantage of the former ones is that they are very fast and accurate but only for well known systems such as conventional UOx PWR (Pressuriezed Water Reactor) or U/PU FNR (Fast Neutron Reactor). The study of innovative reactors required the used of accurate numerical codes, independent of models, using Monte Carlo techniques which depend only on the nuclear data li- braries (cross-sections, ...) and allow full 3D description of the exact geometry. Monte-Carlo codes require more CPU time for calculations (but are not prohibitively long) and are the only reference for innovative reactors or fuel cycles. We have developed a number of tools to couple a Monte Carlo transport code for neutronics, MCNP with fuel burn-up, called MURE . This work has taken place in collaboration with LPSC Grenoble, Subatech Nantes and NRI Czech republic. MURE is written in an oriented object C++, allowing greater portability and conviviality. The main part of MURE concerns the burn-up calculation. It consists of a set of MCNP calculations to obtains reaction rates for given reactor material composition, followed by a numerical (Runge- Kutta) integration of the Bateman equations governing the reactor fuel evolution (fissile burn-up, appearance of fission products and minor actinides) using MCNP results and providing the new composition for the next MCNP run. Special attention has been paid to the definition of evolution conditions: power profile over the evolution, reactivity control by either neutron poisons or control rods, refueling capability, ... After the evolution a graphical interface based on ROOT allows a global view of results as well as offers the possibility to make post treatment (radiotoxicity, heat, ...). A new set of tools has been recently added in order to take into account the fuel evolution during the cooling-down period after irradiation, reprocessing and re-fabrication. This allows to quantify more precisely the waste production and the inventory of fissile materials. Moreover, the decay of 241 Pu (period 14,4 years) outside the reactor is now taken into account, and the impact of the reprocessing on the neutronics and on the quantity of 241 Am in waste can be precisely quantified. Waste comparison The fast reactor studied is the sodium fast reactor 117
nides. A global comparison can be performed, in the same conditions of reactor operation (power, oxide fuels, burn-up, breeding rate) and cycle process (chemical losses, cooling down and refabrication times). Figure 2 summarizes the radiotoxicity comparison. Fig. 2. Comparison of total radiotoxicity for reference U/Pu SFR (pink), for Th/U SFR w/o reprocessing (green), for homogeneous MA reprocessing U/Pu SFR (red), and for homogeneous MA reprocessing Th/U SFR (dark green). This shows that the transmutation of minor actinides leads to a reduction by a factor 10 to 100 of the radiotoxicity of waste, from 300 years after discharge up to 1 million of years. When minor actinides are not reprocessed, the thorium cycle offers a reduction by a factor 10 of the waste radiotoxicity only during a few century. After 3000 years both U and Th cycles are similar. With homogeneous reprocessing, there is a clear advantage of Th/U over U/Pu SFR between 300 years and 100,000 years. Then, due to the 233 U contribution, the radiotoxicity of U/Pu SFR is lower. The thorium cycle, coupled with minor actinides reprocessing, leads to a reduction by factor 100 or 1000 of the waste radiotoxicity during 10000 years, as compared to the reference U cycle without MA transmutation. SFR with a thermal power of 3600 MWth. Fissile zone is split into two enrichment zones. The evolution is performed over 250 years with refuelling. The equilibrium is reached after 200 years. The core is divided in 5 radial zones and 1 axial zone. The reference configuration consists on a fuel made of depleted uranium and plutonium at equilibrium. In this case, minor actinides are not reprocessed. The management of the core assemblies depends on 3 parameters: the “cycle length”, the “cooling time” of used assemblies before the reprocessing and the “refabrication time” to make fresh assemblies. At each irradiation time, the inner fuel assembly zone is removed from the core. Assemblies are moved sequentially from the exterior to the interior of the core (Fig. 1). The fresh assemblies are put in the outer zone. The fresh assemblies are made using the recycled U/Pu from previous depleted ones (after “the cooling time”) and a “fresh fuel” (which is depleted Uranium oxide since the reactor is breeder). This refabrication process takes a “refabrication time”. In this study, the irradiation time is 1 year for core assemblies (thus, on average 1/5 of the core is changed each year), the cooling time is 5 years and the refabrication time is 2 years for core assemblies. Fig. 1. Fuel management in the core, cooling-down, reprocessing and fabrication process. When the transmutation strategy is considered, the reprocessed minor actinides are Neptunium, Americium, Curium, Berkelium and Californium. When recycling, the efficiency of Plutonium, Uranium and MA separation is 99.9%, leading to 0.1% of losses that are sent to waste storage with all fission products. This methodology is used to compare the waste radiotoxicity induced by Uranium and Throium cycle, with or without transmutation of minor acti- It has to be noticed that the same calculations can be made for the residual heat, which is the key parameter for the dimensioning of the waste storage. The difference between cycles and reprocessing strategies are very similar to the radiotoxicities conclusions. Waste and inventories In order to compare very precisely the different reprocessing strategies, one must take into account the waste produced, but also the total mass of materials involved in the cycle. This inventory becomes a waste only when the nuclear fleet shut down, and this makes the global comparison quite difficult. Thus, we propose to study the global gain in terms of waste generation, as a function of the time at which the nuclear fleet will shut down. 118
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EXOTIC NUCLEI STRUCTURE AND REACTIO
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in the spectra by analyzing their t
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were taken from ref. [5]. Concernin
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keV -ray with the particles and the
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the 605.9 keV line of the 74 Zn 2+
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Figure 2 a n d analysis. Figure 2 s
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ing particles was thus obtained by
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First p-p p collisions in the ALICE
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Quarkonia physics with ALICE IPNO P
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NA50 updated puzzle IPNO Participat
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Status of the HADES experiment (I):
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Status of the HADES experiments (II
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Status of the HADES experiment (III
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Hadron physics in pbar-p p annihila
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Hadron Electrodynamics IPNO Partici
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G0 experiment at Jefferson Lab. IPN
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GEp-III and GEp-2 at Jefferson Lab
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Exotic low mass narrow baryons from
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The PVA4 parity violation experimen
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Etude des Distributions de Partons
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Latest Results from GRAAL IPNO Part
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Persistence of the Polarization in
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The northern site of the Pierre Aug
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The Pierre Auger southern Observato
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In figure 4 we plot the differentia
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THEORETICAL PHYSICS Research in the
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transfer reaction, the 34 Si(d, 3 H
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Collective excitations with SKYRME
Page 57 and 58: Pairing and nuclear incompressibili
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Page 61 and 62: Evaporation-residue residue cross s
Page 63 and 64: Extending the VMI model: normal and
Page 65 and 66: Alpha particle condensation in nucl
Page 67 and 68: Collective Modes in Ultracold Trapp
Page 69 and 70: Exploring key unknown neutrino prop
Page 71 and 72: Relic astrophysical and cosmologica
Page 73 and 74: After a term by term Borel resummat
Page 75 and 76: Chiral expansions of the π 0 lifet
Page 77 and 78: IPNO Participation: H. Sazdjian Eff
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Page 83 and 84: A pseudo Coulombian potential in D=
Page 85 and 86: The many-body problem with an energ
Page 87 and 88: The rotational spectrum and the att
Page 89 and 90: Z-identification of very heavy nucl
Page 91 and 92: The Pegase project, a new solid sur
Page 93 and 94: But at 80 keV total energy ( 200 eV
Page 95 and 96: Isospin effects on fragment and par
Page 97 and 98: Radial collective energy and fragme
Page 99 and 100: Latent heat of the phase transition
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Page 103 and 104: Fluo X: Deexcitation time measureme
Page 105 and 106: ENERGY AND ENVIRONMENT The increasi
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Page 111 and 112: 3D coupling of Monte-Carlo neutroni
Page 113 and 114: Fission cross sections of actinides
Page 115 and 116: Studies and synthesis of specific m
Page 117 and 118: Chemistry and Electrochemistry of T
Page 119 and 120: function of temperature. The recent
Page 121 and 122: global electron number of the redox
Page 123: (D 0 /D)-1 ln complexes of Pa(V). I
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exotic nuclei structure and reaction noyaux exotiques ... - IPN - IN2P3

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