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Although recent decades have been the warmest since 1850, and global mean temperatures during 2015 and 2016 beat all instrumental records, the rate of increase in global surface air temperature (GSAT) significantly decreased at the beginning of the 21st Century. In this context, we examine the roles of ice melting and associated increase in sea-water mass, both of which significantly increased at the same time as GSAT decreased. Specifically, we show that (1) the slowdown of the rate of increase in GSAT between the specific periods 1992–2001 and 2002–2011 exists in all three climate records analyzed and is statistically significant at the 5% level amounting between 0.029 and 0. 036°C/yr and leaving an energy of 14.8–18.4 1019 J/yr available; (2) the increase of the atmosphere-related ice melt between these two periods amounts to 316 Gt/yr which requires 10.5 1019 J/yr, that is, between 57% and 71% of the energy left by the slowdown; and (3) the energy budget shows, therefore, that the heat required to melt this additional 316 Gt/yr of ice is of the same order as the energy needed to warm the atmosphere during the decade 2002–2011 as much as during the previous one, suggesting a redistribution of heat within the atmosphere–cryosphere system.

A rapid development of nuclear energy production reaching 173 EJ/y in 2060 and 605 EJ/y in 2110 limits the Global Mean Surface Temperature (GMST) increase to 1.5°C with respect to preindustrial value, with a reduction of the stored carbon dioxide from 800 Gt in the original MESSAGE-Efficiency scenario to 275 Gt in the present one, while multiplying by 6 the Total Primary Energy Supply between 2015 and 2110.

The framework MESSAGE from the IIASA fulfills the IPCC requirement RCP 2.6. To achieve this, it proposes the use of massive deployment of Carbon Dioxide Capture and Storage (CCS), dealing with tens of billion tons of CO2. However, present knowledge of this process rests on a few experiments at the annual million tons level. MESSAGE includes three scenarios: ‘Supply’ with a high energy consumption; ‘Efficiency’ which implies the end of nuclear energy and the intermediary ‘MIX’. We propose, as a variant of the MESSAGE framework, to initiate a sustained deployment of nuclear production in 2020, reaching a total nuclear power around 20,000 GWe by the year 2100. Our scenarios considerably reduce the interest or necessity for CCS. Renouncing nuclear power requires an energy consumption reduction of more than 40% compared to the ‘Supply’ scenario, without escaping the need to store more than 15 billion tons of CO2.

Un developpement rapide de la production d’energie nucleaire pour atteindre 173 EJ/an2 (4 152 Mtep, 47 921 TWh) en 2060, puis 605 EJ/an (14 520 Mtep, 167 585 TWh) en 2110, permettrait de limiter l’elevation de la temperature globale moyenne de surface (GMST3) a 1,5 °C par rapport a sa valeur preindustrielle, tout en reduisant la quantite de CO2 a stocker en passant des 800 Gt envisagees dans le scenario MESSAGE-Efficiency originel a 275 Gt dans le scenario objet du present article, et en doublant l’energie primaire totale disponible entre 2015 et 2110.

We discuss here the concept of Thorium Molten Salt Reactor dedicated to future nuclear energy production. The fuel of such reactors being liquid, it can be easily reprocessed to overcome neutronic limits. In the late sixties, the MSBR project showed that breeding is possible with thorium in a thermal spectrum, provided that an efficient pyrochemical reprocessing is added. With tools developed around the Monte Carlo MCNP code, we first re-evaluate the performance of a MSBR-like reference system with 232Th/233U fuel. We find an important reduction of inventories and induced radiotoxicities at equilibrium compared to other fuel cycles, with a doubling time of about thirty years. We then study how to start this interesting reference system with theplutonium from PWR spent fuel. Such a transition appears slow and difficult, since it is very sensitive to the fissile quality of the plutonium used. Deployment scenarios of 232Th/233U MSBR-like systems from the existing French PWRs demonstrate the advantage of an upstream 233U production in other reactors, allowing a direct start of the MSBR-like systems with 233U. This finally leads us to explore alternatives to some MSBR features, for energy production with 232Th/233U fuel from the start. We thus test different options, especially in terms of core neutronics optimization and reprocessing unit adaptation.

We summarize here the results of the TARC experiment whose main purpose is to demonstrate the possibility of using Adiabatic Resonance Crossing (ARC) to destroy efficiently Long-Lived Fission Fragments (LLFFs) in accelerator-driven systems and to validate a new simulation developed in the framework of the Energy Amplifier programme. An experimental set-up was installed in a CERN PS proton beam line to study how neutrons produced by spallation at relatively high energy ( E n ⩾1 MeV ) slow down quasi-adiabatically with almost flat isolethargic energy distribution and reach the capture resonance energy of an element to be transmuted where they will have a high probability of being captured. Precision measurements of energy and space distributions of spallation neutrons (using 2.5 and 3.5 GeV/c protons) slowing down in a 3.3 m×3.3 m×3 m lead volume and of neutron capture rates on LLFFs 99Tc, 129I, and several other elements were performed. An appropriate formalism and appropriate computational tools necessary for the analysis and understanding of the data were developed and validated in detail. Our direct experimental observation of ARC demonstrates the possibility to destroy, in a parasitic mode, outside the Energy Amplifier core, large amounts of 99Tc or 129I at a rate exceeding the production rate, thereby making it practical to reduce correspondingly the existing stockpile of LLFFs. In addition, TARC opens up new possibilities for radioactive isotope production as an alternative to nuclear reactors, in particular for medical applications, as well as new possibilities for neutron research and industrial applications.

The Transmutation by Adiabatic Resonance Crossing (TARC) experiment was carried out as PS211 at the CERN PS from 1996 to 1999. Energy and space distributions of spallation neutrons (produced by 2.5 and 3.57 GeV/c CERN proton beams) slowing down in a 3.3×3.3×3 m3 lead volume and neutron capture rates on long-lived fission fragments 99Tc and 129I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation.

An already existing, sub-critical arrangement made of natural uranium and water moderator has been exposed to a low intensity (≈ 109 ppp) proton beam from CERN-PS at several kinetic energies from 600 MeV to 2.75 GeV. The energy delivered by the hadronic cascade induced by the beam in the device has been measured by the temperature rise of small sampling blocks of uranium located in several different positions inside the device and counting the fissions in thin probe foils of natural uranium. We find typically G ≈ 30 in reasonable agreement with calculations, where G is the ratio of the energy produced in the device to the energy delivered by the beam. This result opens the way to the realisation of the so-called Energy Amplifier, a practical device to produce energy from thorium or depleted uranium targets exposed to an intense high energy proton beam. Results show that the optimal kinetic is ≥ 1 GeV, below which G decreases but is still acceptable in the energy range explored

We present results from an experimental study of reabsorption effects in subthreshold pi0 production in the reaction Xe-129 + Au-197 at 44 MeV/nucleon. Within the picture of pion generation in nucleon-nucleon scattering we deduce, from our data and from a comparison with the systematics of production cross sections available for lighter reaction systems, information on the pi0 absorption length in nuclear matter. For the pi0 kinetic-energy range congruent-to 5-100 MeV the energy-averaged lambda(abs) and its momentum dependence are obtained, and compared with optical-model calculations.

For the reaction of 16 O and 36 Ar with the AgBr component of emulsion at 210±10 MeV and 65±15 MeV per nucleon, respectively, the fragments' charge and emission angle have been measured. An additional momentum-flow-tensor analysis provides a strict criterion to distinguish the very central from peripheral events. The analysis reveals that complete stopping is possible in both reactions. It is also shown that an analysis of the data with respect to the criticality of the fragmentation process based solely on central events might lead to conclusions different from those inferred so far from inclusive data.

In a pragmatic view of media communication, we present a new method for studying cognitions during reception (labeled ECER method) to go beyond some theoretical and methodological limitations of dual-process theories of attitude formation and change. This implementation of real-time process-tracking operationalizes cognitive elaboration and cues that set processing in motion. It enables picking up viewers' cognitive responses during exposure to the message and analysing them with a cognitivo-discursive analysis (Tropes software). In a first application, the ECER method is integrated into an experiment on the role of the viewer's degree of involvement in cognitive processing. The results show that the more the viewers are involved, the more they engage in cognitive elaboration and the more they develop cognitive strategies of discourse that express a “ real world ”. Inconsistent with current models, we show that involvement does not result in processing one type of cues (peripheral or central) more than another.

europhysicsnews 24 • volume 38 • number 2 amounts of uranium 233 available remained tiny, insufficient to allow the rapid development of a thorium-uranium concept. It appears today that the growth rate of nuclear power worldwide does not require the fast development of breeder reactor concepts. It is then possible, as we show in this paper, to constitute a stockpile of uranium 233 that could allow the development of a fleet of thorium-uranium reactors. We show also that such a concept has many major advantages, in particular concerning the disposal of radioactive waste and the risks of nuclear proliferation.We give a brief description of the types of reactors being considered to implement this fuel cycle and of a strategy that makes use of today’s reactors to create the initial stockpiles of uranium 233.

PACS; Une filière nucléaire thorium-uranium dans laquelle le noyau fissile principal est l'uranium 233, dont la régénération par capture neutronique est assurée par le thorium 232, présente des avantages potentiels importants par rapport à la filière actuelle uranium-plutonium : en particulier, une moindre production de déchets de haute activité et vie longue, et une prolifération nucléaire plus difficile. On présente rapidement les types de réacteurs envisagés pour mettre cette filière en oeuvre. On montre enfin qu'une stratégie utilisant les réacteurs à eau pressurisée actuels, avec un combustible oxyde mixte de thorium et de plutonium, permettrait de constituer le stock initial d'uranium 233.

L'énergie est un thème de débats parfois exacerbés. L'objectif de cet ouvrage est d'apporter des éléments de référence de la part de scientifiques et économistes reconnus.

This paper deals with the neutronic Monte Carlo simulations in view of an eXperimental Accelerator Driven System (XADS) optimization and characterization. With this aim, the quite realistic concept of XADS chosen for our investigations, comes from the preliminary studies done by Framatome ANP. First, we simulate this basic concept with different fuels and characterize the time evolution of the conceivable fuels, especially with minor actinides. Secondly, we consider the neutronic parameters in view of an extrapolation of the XADS toward a large ADS. We also consider some alternative solutions to reduce the flux peak in the first assemblies around the spallation target of a large ADS and consequently to improve the shape factor and the efficiency of the core. Finally, we focus on the generation of 233 U based on a plutonium and minor actinide fuel associated to thorium oxide to start power Molten Salt Reactors (MSR) and to accelerate the transition toward a 232 Th/ 233 U cycle which offers an interesting option for nuclear waste reduction and nuclear energy production during many centuries.

Carlo Rubbia (1) recently made the headlines by proposing to use hybrid systems to produce energy. A hybrid system associates a high intensity proton or deuteron accelerator to a neutron multiplier assembly. Such systems might have a number of advantages when compared to standard reactors. If correctly designed, they would make critical accidents, such as that of Tchernobyl, impossible. However, it is true that loss of cooling accidents such as that of Three Mile Island might still be possible, unless we resort to systems with natural convection cooling properties, such as those with molten salt fuels or liquid metal coolants. The number of neutrons available for breeding or waste transmutation is larger in hybrid systems than in reactors. Systems based on the Thorium-Uranium cycle, be they hybrids or traditional, would produce much less Plutonium and higher actinides than those based on the usual Uranium-Plutonium cycle. The interest in hybrid systems based on the Thoriud-Uranium cycle originate...

It is well known that charged particles emit bremsstrahlung radiation when they are accelerated. Classical electron bremsstrahlung occurs when a proton is emitted by an electron accelerated in the field of a nucleus. The bremsstrahlung process also occurs in the scattering of nucleons, for which it is the lowest energy inelastic process that can occur. Like electron bremsstrahlung, nucleon-nucleon bremsstrahlung also requires the exchange of a virtual particle to conserve energy and momentum. In electron bremsstrahlung a virtual photon is exchanged but with two nucleons a meson can be exchanged. Unlike electron bremsstrahlung, in nucleon-nucleon bremsstrahlung the photon can originate from the exchanged meson. This exchange contribution has been shown in calculations to be a significant fraction of bremsstrahlung events. Thus bremsstrahlung serves as a probe of exchange currents in the nucleon-nucleon interaction. Because of a lack of a free neutron target or an intense neutron beam, few measurements of neutron-proton bremsstrahlung exist, each having poor statistical accuracy and poor energy resolution. The white neutron source at the Weapons Neutron Research (WNR) target area at the Los Alamos Meson Physics Facility (LAMPF) produces neutrons with energies from below 50 to above 400 MeV. Using time-of-flight techniques and a liquid hydrogen target, we are measuring the outgoing photons of energies up to 250 MeV at gamma ray angles of around 90° relative to the incident beam. Protons scattered at very forward angles are also detected in coincidence with the gamma rays.

This paper is an introduction to the physics of Accelerator Driven Subcritical Reactors (ADSR) and some technologies associated with them. The basic neutronics is presented with a specific discussion of modifications with respect to that of critical reactors. The fuel evolution in ADSR's is discussed, including the influence of reactivity surges and drops on the limitation of the design reactivity. The application of ADSRs to nuclear waste management is examined and the different options are discussed. Finally, some practical proposals are briefly discussed.

The possible interest of accelerator driven subcritical reactors for minor actinides incineration is examined. The physics of neutron multiplying systems is recalled. The differences between critical and subcritical reactors' control are described, with emphasis on the importance of the delayed neutrons fraction. The minor actinides fuel evolution is studied with the conclusion that fast neutron spectra are clearly more efficient then thermal neutron spectra. It is, also, shown that characteristic times for incineration should be in the order of 10 years. The number of minor actinides incinerators necessary for 60 PWRs is estimated to be about 6 with total thermal power of 9 GW. These reactors will, also, be able to transmute essentially all 99 Tc and 129 I produced by the 60 PWR. The excess electricity cost for MA incineration is estimated to be about 5%.

s the conference in The Hague was taking place, the outlook on global warming was increasingly alarming. In spite of the price increase of oil, a good thing from this point of view, and of gas in the near future, there does not seem to be any sign ofa reac­ tion similar to that of 1973. Though energy conservation, and the development of renewable energysources are desirable, it is more obvious every day that these will not be sufficient to stabilise, and even less, to reduce the emission of greenhouse gases. Clearly, it is only through the renewed development of nuclear energy in the industrialised countries that we can obtain a significant and rapid reduction of gas emissions. We need only note that countries like France and Sweden,whichproduce their electricity without burn­ ing fossil fuels, generate half as much carbon dioxide per unit of energy consumed as Denmark whose electricity is produced essentially in coal or lignite plants. It seems paradoxical, then, that the energy supply scenarios put forward by such instances as the World EnergyCouncil do not seem to consider seriously a renew­ al of nuclear energy. On the contrary, certain countries, like Germany, are considering pulling out of nuclear energy altogeth­ er. It's as though the dangers associated with nuclear energy were perceived as worse than those related to global warming. Does this view rest on objective data, or is it not, rather, irrational? We cannot do without thinking this matter through: the future of our planet maydepend on the choices we make. We will attempt, here, to initiate such a reflection, as unbiased as possible. The first thing to do, then, is to compare the risks due to nuclear energy and to the production of greenhouse gases from the combustion offossil fuels. Nuclear risks

The full understanding of the kinetics of a subcritical assembly is a key issue for its online reactivity control. Point kinetics is not sufficient to determine the prompt reactivity of a subcritical assembly through the response to a dirac pulse, in particular in the cases of a large reflector, a small reactor, or a large subcriticality.Taking into account the distribution of intergeneration times, which appears as a robust characteristic of each type of reactor, helps to understand this behaviour.Eventually, a method is proposed for the determination of the prompt reactivity. It provides a decrease rate function depending on the prompt multiplication coefficient Keffp. Fitting a measured decrease rate with this function, calculated once for the reactor, gives the true value of keffp. The robustness of the method is tested. (Elsevier)

We have performed detailed Monte Carlo simulations of different subcritical fast hybrid reactor fuel configurations leading to the possible use of these devices as energy generators. The method is based on the coupling between a validated neutron transport code and a mathematical solution of the equations describing the time evolution of the neutron spectrum and mean cross-section during the reactor operation. We have optimized the geometrical and operational characteristics of reactors based on 232 Th / 233 U and nat U/Pu oxide fuels and simulated their operation over 20 fuel cycles (200 years of energy generation). Quantitative results are presented for the inventories, waste production and induced radiotoxicities under alternative scenarios of fuel reprocessing. The possible paths to start a fuel cycle based on thorium are studied, identifying the use of highly enriched uranium or plutonium from PWR spent fuel as options to start a fuel cycle which tends asymptotically towards 232 Th / 233 U . The comparison between the simulated hybrid systems and the existing PWR reactors indicate significant reductions of the total radiotoxicity for fuel cycles based on thorium and fuel reprocessing which include the minor actinides, as well as plutonium and uranium separation.

Energy and space distributions of spallation neutrons (from 2.5 and 3.57 GeV/c CERN proton beams) slowing down in a 3.3 x 3.3 x 3 m3 lead volume and neutron capture rates on long-lived fission fragments 99 Tc and 129 I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation.

The use of accelerator driven system (ADS) like for instance the Energy Amplifier concept (EA) proposed by C. Rubbia and his group might be one of the solutions to solve the energy problem and in particular to answer the question: what could we do with the nuclear waste produced by the present nuclear reactors? We present in this paper the EA concept, which is illustrated by two experiments performed at the CERN-PS facility. One of them is the TARC (Transmutation by Adiabatic Resonance crossing) experiment which is designed to demonstrate the high efficiency offered by the EA to destroy the long-lived fission fragments.

In the TARC experiment the differential neutron flux φ(E,r) of a spallation of 2.5 and 3.5 GeV/c proton in large lead block is measured in the range between 0.1 eV and 1.5 MeV. A new technique, using small quantities (less than 0.1 gram) of material, is used for measuring the transmutation rate as a function of neutron energy in the range between 0.1 eV up to a few keV. The method is applied to a target of 86 mg (99Tc) mixed with 1.7 g of Aluminum. From these measurements the energy profile of the capture cross section can be extracted.

The superheavy nucleus 108 272 Hs and its evaporation daughters have been produced using the reaction 232 Th( 40 Ar,γxn) with beam energies 10.5 and 15.0 MeV/ A . The Giant Dipole Resonance γ-radiation from the hot conglomerate system prior to fission has been isolated using a differential method. The pre-fission component shows a strong dipole angular distribution relative to the spin direction. A saturation of the GDR strength is observed for the highest excitation energies.

Event-by-event emission pattern of all charged fragments in central and semi-central, symmetric, semi-symmetric and asymmetric heavy-ion collisions at energies (50–220) A ·MeV have been studied in nuclear emulsions. The most central collisions, selected by momentum-tensor elongation and multiplicity criteria, exhibit one single fused source. Collective flow in this source is observed in symmetric (Kr + AgBr) collisions and weakly indicated in semi-symmetric (Ar + AgBr) collisions. Semi-central events exhibit quasi-target, quasi-projectile and participant or incomplete fusion sources from which no or very weak flow signals are observed. The emission from these sources is described by a Coulomb explosion model except for the fact that sub-Coulomb barrier fragments are frequent.

Heavy hypernuclei are produced in the annihilation of antiprotons in [sup 238]U. The delayed fission of heavy hypernuclei and hypernuclei of fission fragments are observed by using the recoil-distance method in combination with measurement of secondary electron multiplicity. The lifetime of hypernuclei in the region of uranium is found to be (1.25[plus minus]0.15)[times]10[sup [minus]10] sec. It is observed that [Lambda] hyperons predominantly stick to the heavier fission fragments. The yield of hypernuclei is found to be (7.4[plus minus]1.7)[times]10[sup [minus]3] per stopped antiproton. No coincidences with [ital K][sup +] were found. Statistical and systematic errors on the number of events expected do not rule out this possibility.

The results on delayed and prompt fission of heavy hypernuclei obtained by the LEAR PS177 collaboration are recalled and discussed. It is shown that the hypernuclei life-times can be explained in term of a weak strangeness violating lambda-nucleon interaction with a cross section close to 6.0 10−15 barns. The lambda attachment function is shown to be sensitive to the scission configuration, just before fission, and to the neck dynamics. This function provides a new way to study the nuclear scission process.

Measurements of neutron yields and their angular distributions in coincidence with fission fragments produced in antiproton annihilation at rest in a natural uranium target have been carried out Low Energy Antiproton Ring (LEAR) at CERN. A total of 16.3\ifmmode\pm\else\textpm\fi{}0.9 neutrons per annihilation have been found, distributed among direct knockout (27%), evaporation (21%), and fission (52%) processes. Angular distributions show that neutrons below approximately 5 MeV result entirely from moving fission fragments, and above approximately 12 MeV entirely from the excited, prescission nucleus. An estimate of the angular momentum of the excited fission fragment gives \ensuremath{\sim}13\ensuremath{\Elzxh}. We are able to account for all baryons produced in annihilation, including neutrons from this experiment and light charged nuclei found in another LEAR experiment, to within 4.5\ifmmode\pm\else\textpm\fi{}2.5 of the initial 237 units in the initial state.

Antiproton induced fission probabilities of U238, Bi209, Pb208 and Au177 are reported together with the mass distribution of the fission fragments in the U238 and Bi209 cases. The charged particles multiplicities observed in co-incidence with fission have, also, been measured for U and Bi and are presented.

Double-differential cross sections for photons above 20 MeV were measured for the 3 He+(d, C, Cu and Au) reactions at 284 MeV. The comparison of their energy spectra shows that the high-energy gamma rays are produced by the same mechanism in the very light 3 He + d system and in heavier ones like 3 He + (C, Cu and Au) or Xe + Sn, previously studied by the MSU group. A calculation of the 3 He+(C and Au) systems at 90° in the laboratory was performed, assuming that photons are produced in first-chance nucleon-nucleon collisions and for a realistic momentum distribution of the nucleons in the 3 He projectile. The results are in good agreement with the experimental data which suggests that secondary collisions are not important in the production of photons above 50 MeV for nucleus-nucleus reactions at 90 MeV/nucleon.

A review of experimental data on Nucleus-Nucleus-Gamma reactions is given. Spectra display an exponential shape above 30 MeV, with an almost linear variation of the exponential parameter with incident beam energy. The laboratory angular distributions show strong forward peaking, as well as a remarkable insensitivity to the mass ratios of target and projectile. Transformed into the nucleon-nucleon center of mass, these angular distributions display forward backward symmetry. They are mostly isotropic, with a slight admixture of a dipole component. In first approximation, the intensity of the spectra appear to be proportional to the number of first nucleon-nucleon collisions, which leads to a simple scaling law. Exclusive measurements display an interesting correlation between the hardness of the spectra and the centrality of the collision. Experimental results put stringent constraints on theoretical models. The scaling laws appear to contradict the prediction of collective models where both nuclei behave like entities. The angular distributions do not seem to be easily reconciled with emission by thermal sources. Semi-classical dynamical calculations of the BUU or Landau-Vlassov type, where the collision term is the source of incoherent photon emission, have been used extensively to reproduce the experimental results. These calculations were able to reproduce most of the experimental features. Photon emission in Nucleus-Nucleus collisions is, thus, intimately related to that occuring in the elementary n-p reaction. Recent measurements and calculations show that most of the photon production is, in this case, related to the charged pion exchange between the two nucleons. Therefore, Nucleus-Nucleus collisions may be a unique probe of the exchange currents in hot and dense nuclear matter.

A schematic scission model is applied to the lambda-attachment function recently obtained by the LEAR PS177 collaboration, in their measurement of the prompt fission of hypernuclei. It is shown that the attachment function is sensitive to the scission configuration, necking dynamics and nuclear temperature at scission. It provides a new and powerful way to study the nuclear scission process.

We calculate the differential cross section for nucleonnucleon bremsstrahlung in covariant way based on a realistic meson-exchange approximation for the NN-scattering amplitude. The results are discussed in comparison to semiclassical approximations and with respect to the role of internal radiation diagrams. The influence of the anomalous magnetic moment on the proton-neutron bremsstrahlung is found to contribute up to 50% for specific kinematical conditions. Recent measurements on the elementary differential cross sectionpn→pnγ are found to be quite accurately reproduced. Furthermore, for use in proton-nucleus and nucleus-nucleus collisions, we present a parametrization of thepnγ cross section within a broad kinematical range.