Beam tests of the trigger and digital processing electronics for the electromagnetic calorimeter of the CMS experiment

A prototype of the trigger and digital processing electronics for the electromagnetic calorimeter of the CMS experiment, coupled to a prototype of the PbWO4 crystal calorimeter, was tested during summer 96 in the H4 beamline at the CERN SPS. A very successful operation was achieved for this system, which runs in synchronous and pipelined mode at the LHC clock frequency, and performs the basic trigger and data acquisition functions needed in the CMS electromagnetic calorimeter. The performance of the trigger front-end electronics is well within the established requirements: a highly efficient bunch crossing identification ( > 99.9%), a good trigger energy resolution ( s/E ~9%/sq( E)+2%) and a highly efficient electron cluster shape identification ( ~99%) have been achieved. The FERMI digitizing system based on a dynamic analog compressor and a sampling ADC showed a very good perform ance, in particular the energy resolution for 150 GeV electrons was 0.54%, equal to the resolution obtained with a conventional charge integration ADC system

Innovative Sodium Fast Reactors Control Rod Design

International audienc

Optimization of minor actinides bearing radial blankets for heterogeneous transmutation in fast reactors

International audienceA new methodology dedicated to the optimization of minor actinides (MA) transmutation in dedicated blankets is discussed here. In the so-called heterogeneous transmutation approach, minor actinides are loaded in specific assemblies located at the periphery of a fast reactor core. Thus, the resulting perturbation on the core behavior is limited and the management of minor actinides is entirely decoupled from standard fuel management. This also allows greater flexibility in the blankets design, in terms of material, volume fraction or neutron spectrum to be used. On the other hand, the low neutron flux level experienced at the periphery of the core slows down the transmutation process. If this effect can be compensated by an increase of the minor actinides fraction loaded in the blankets, this also strongly increases their decay heat and neutron source level, which complicates spent fuel reprocessing and handling. An optimization is carried out with regards to the neutron spectrum and americium concentration in the blankets, with the dual objective of maximizing the transmuted MA mass while minimizing the total MA inventory in the fuel cycle by limiting the cooling time of such blankets. Artificial neuron networks are coupled with a genetic algorithm in order to reduce total calculations time. It is shown here that regardless of the MA mass to be loaded, the use of a slightly moderated neutron spectrum is the most promising option for heterogeneous transmutation. This result is confirmed by full core calculations. An analysis with regards to the irradiation time is also performed, and it is shown that maximization of the irradiation time should be sought in the specific case studied here. It is concluded that from a purely physical point of view, no breakthrough can be obtained for heterogeneous transmutation

Analysis and optimization of minor actinides transmutation blankets with regards to neutron and gamma sources

Heterogeneous loading of minor actinides in radial blankets is a potential solution to implement minor actinides transmutation in fast reactors. However, to compensate for the lower flux level experienced by the blankets, the fraction of minor actinides to be loaded in the blankets must be increased to maintain acceptable performances. This severely increases the decay heat and neutron source of the blanket assemblies, both before and after irradiation, by more than an order of magnitude in the case of neutron source for instance. We propose here to implement an optimization methodology of the blankets design with regards to various parameters such as the local spectrum or the mass to be loaded, with the objective of minimizing the final neutron source of the spent assembly while maximizing the transmutation performances of the blankets. In a first stage, an analysis of the various contributors to long- and short-term neutron and gamma source is carried out whereas in a second stage, relevant estimators are designed for use in the effective optimization process, which is done in the last step. A comparison with core calculations is finally done for completeness and validation purposes. It is found that the use of a moderated spectrum in the blankets can be beneficial in terms of final neutron and gamma source without impacting minor actinides transmutation performances compared to more energetic spectrum that could be achieved using metallic fuel for instance. It is also confirmed that, if possible, the use of hydrides as moderating material in the blankets is a promising option to limit the total minor actinides inventory in the fuel cycle. If not, it appears that focus should be put upon an increased residence time for the blankets rather than an increase in the acceptable neutron source for handling and reprocessing

Study on the self-shielding and temperature influences on the neutron irradiation damage calculations in reactors

International audienc

Towards spatial kinetics in a low void effect sodium fast reactor: core analysis and validation of the TFM neutronic approach

The studies presented in this paper are performed in the general framework of transient coupled calculations with accurate neutron kinetics models able to characterize spatial decoupling in the core. An innovative fission matrix interpolation model has been developed with a correlated sampling technique associated to the Transient Fission Matrix (TFM) approach. This paper presents a validation of this Monte Carlo based kinetic approach on sodium fast reactors. An application case representative of an assembly of the low void effect sodium fast reactor ASTRID is used to study the physics of this kind of system and to illustrate the capabilities provided by this approach. To validate the interpolation model developed, different comparisons have been performed with direct Monte Carlo and ERANOS deterministic S N calculations on spatial kinetics parameters (flux redistribution, reactivity estimation, etc.) together with point kinetics feedback estimations

Nuclear data propagation with burnup : impact on SFR reactivity coefficients

International audienceFor the next generation fast reactor design, theGeneration IV International Forum (GIF) defined globalobjectives in terms of safety improvement, sustainability,waste minimization and non-proliferation. Among thepossibilities studied at CEA, Sodium cooled Fast Reactor(SFR) are studied as potential industrial tools for nextdecade’s deployment. Many efforts have been made in thelast years to obtain advanced industrial core designs thatcomply with these goals. Concerning safety issues,particular efforts have been made in order to obtain coredesigns that can be resilient to accidental transients. The“safety” level of such new designs is often characterizedby their “natural” behavior under unprotected transientssuch as loss of flow or hypothetical transient over power.Transient analysis needs several accurate neutronic inputdata such as reactivity coefficient and kinetic parameters.Beside estimation of the level of “absolute” values,associated uncertainties have also to be evaluated for thewhole set of relevant data. These estimations have to beperformed for different core state such as end of cyclecore for feedback coefficient. This means thatuncertainties have to be obtained not only a fixed time butalso have to be propagated all through irradiation.To do so, we need to couple Boltzman and Batemanequations at sensitivities level. The coupling processcould be done with the help of the perturbation theorywhich gives adapted framework suited for deterministiccalculation codes. This coupling is currently in progressin ERANOS code system. The actual implementation givesaccess to estimation of sensitivities for both reactivitycoefficients and mass balance.After a brief theoretical description of Boltzman/Batemancoupling capabilities in ERANOS, the study presented inthis paper focuses on sensitivity and uncertaintiesestimation for the main feedback coefficients involved infast reactor transients: the thermal sodium expansioncoefficient and the Doppler Effect. Using thesesensitivities, a global evaluation of impact of the fueldepletion can be quantified for these reactivity effects atcore scale for end of cycle state. An illustration is givenfor a GEN IV SFR industrial core design (SFR V2B). Afirst glance at preliminary uncertainty level is presentedusing current covariance matrices available at CEA

An optimization methodology for heterogeneous minor actinides transmutation

In the case of a closed fuel cycle, minor actinides transmutation can lead to a strong reduction in spent fuel radiotoxicity and decay heat. In the heterogeneous approach, minor actinides are loaded in dedicated targets located at the core periphery so that long-lived minor actinides undergo fission and are turned in shorter-lived fission products. However, such targets require a specific design process due to high helium production in the fuel, high flux gradient at the core periphery and low power production. Additionally, the targets are generally manufactured with a high content in minor actinides in order to compensate for the low flux level at the core periphery. This leads to negative impacts on the fuel cycle in terms of neutron source and decay heat of the irradiated targets, which penalize their handling and reprocessing. In this paper, a simplified methodology for the design of targets is coupled with a method for the optimization of transmutation which takes into account both transmutation performances and fuel cycle impacts. The uncertainties and performances of this methodology are evaluated and shown to be sufficient to carry out scoping studies. An illustration is then made by considering the use of moderating material in the targets, which has a positive impact on the minor actinides consumption but a negative impact both on fuel cycle constraints (higher decay heat and neutron) and on assembly design (higher helium production and lower fuel volume fraction). It is shown that the use of moderating material is an optimal solution of the transmutation problem with regards to consumption and fuel cycle impacts, even when taking geometrical design considerations into account

A comparison of curium, neptunium and americium transmutation feasibility

International audienceMinor actinides transmutation is the process of decreasing the long term radiotoxicity of the nuclear spent fuel by submitting it to a neutron flux so as to achieve fission of the heavy nuclides concerned. In the case of a closed fuel cycle, minor actinides are the main contributors to the spent fuel radiotoxicity after a few centuries. The isotopic vector of the minor actinides feed to be transmuted depends heavily on the fuel cycle considered PWRs with UOX fuels will mainly lead to neptunium and americium production while MOX fueled reactors will produce mainly americium and curium. Americium is the main element currently considered for transmutation due to its relatively short half-life and important production. On the other hand, neptunium is seen as a secondary candidate for transmutation due to its very long half life and low activity while Curium has transmutation is generally ruled out due to the important activity of curium isotopes. Two modes of transmutation in fast reactors are generally opposed, namely the homogeneous approach in which minor actinides are directly mixed with the fuel while in the heterogeneous approach, the minor actinides are loaded in dedicated targets. It is shown in this paper that the impacts on the fuel cycle of heterogeneous americium transmutation are similar to the one of homogeneous curium transmutation. It is further shown that given the quantities of curium in the fuel cycle, only a limited number of reactors would be required to effectively transmute the curium production of fast reactors with americium bearing blankets. Curium transmutation thus appears a feasible option in a completely closed fuel cycle without significantly higher fuel cycle impacts than with only americium transmutation. It is finally verified that neptunium transmutation can be achieved regardless of the approach considered

Validation of Fast Neutron Reactors fertile blanket depletion calculations through the analysis of the DOUBLON experiment in PHENIX with TRIPOLI-4® and DARWIN3-SFR

International audienceA reliable assessment of the final inventory in the fertile blanket of a Fast Neutron Reactor is an important issue for fuel cycle physics, as it impacts safety, reprocessing and design studies. The performances of fertile blankets neutronics calculations is a long standing issue, as there as specificities in these regions that are quite challenging, especially for depletion codes.The new CEA fuel depletion calculation package is DARWIN3-SFR, which incorporates the deterministic neutronics code APOLLO3® and the depletion module MENDEL. This paper details the validation of DARWIN3-SFR for fertile blanket calculations through the re-interpretation of the DOUBLON pin-irradiation in the Phenix reactor.During this irradiation, nine pins are studied through isotopic ratios, which give us information about the depletion and, indirectly, the neutron flux calculations inside the blanket. This environment is especially challenging for neutronics codes, since there is a strong variation of the neutron energy and population over a short distance. Our recent analysis of TRAPU - which is a similar experiment, but in the core center - has proven DARWIN3-SFR to be reliable for the fuel depletion calculations of fissile subassemblies; nevertheless, its performances in the fertile blankets still require validation.We observe that, once the calculated neutron flux level has been adjusted to the experiment through the 148Nd/238U ratio, DARWIN3-SFR provides results similar to the reference stochastic code TRIPOLI-4®. However, both codes have difficulties to reproduce some of the measured isotopic ratios inside the fertile blanket. Whilst DARWIN3-SFR produces identical results for most of the isotopes analysed (234U, 235U, 236U, 238Pu, 239Pu, 240Pu), variations of the neutron spectrum lead to some disparities for the production of 241Pu and 242Pu. Indeed, the low-energy flux estimation is higher with TRIPOLI-4® than with DARWIN3-SFR in the energy range where the 240Pu has a high capture cross section, which increases the calculated production of 241Pu and 242Pu.DARWIN3-SFR and its predecessor DARWIN-2 are efficient at calculating the average neutron flux level over the entire fertile blanket. However, the results of the two codes show a strong pin-to-pin dispersion, resulting in a different shape of the neutron flux inside the blanket. With DARWIN3-SFR, the estimated neutron spectrum is softer than in DARWIN-2, which impacts the 238U capture and fission reaction rates and hence the production of plutonium