A disruptive approach to eliminating weapongrade plutonium - Pu burning in a molten salt fast reactor

The successful implementation of disarmament treaties of the last centuries has led to significant amounts of weapon-grade Plutonium which are currently stored in high security storage facilities. Disposing this Plutonium should be seen as 'good housekeeping' avoiding unnecessary costs and the hazards of storing this material indefinitely. In addition, the disarmament is only brought to a successful end when the Plutonium isn't available for the production of new weapons anymore. We propose a disruptive approach for Plutonium disposition and demonstrate the feasibility in a neutronic study. Burning of weapon-grade Plutonium in a molten salt fast reactor is significantly more efficient than in the studied other reactors, while efficient process design has the potential to reduce the security concerns significantly. The proposed system could turn about 1.25 tons of weapon-grade Plutonium into electric energy worth £ 0.5 to 1 billion/year, depending on the electricity price while avoiding the hassle and eliminating the risk of high security Plutonium storage. In conclusion, burning of the weapon-grade Plutonium resulting from disarmament could be an economically very attractive approach to reduce the nuclear threat

Studie zur Partitionierung und Transmutation (P&T) hochradioaktiver Abfälle Stand der Grundlagen- und technologischen Forschung

Das, dem Teilprojekt zu Grunde liegende, Gesamtprojekt gliederte sich in zwei Module: In Modul A (Förderung durch das BMWi, Federführung durch KIT) und Modul B (Förderung durch das BMBF, Federführung durch acatech). Projektpartner im Modul A waren DBE TECHNOLOGY GmbH, die Gesellschaft für Anlagen- und Reaktorsicherheit mbH (GRS), das Helmholtz-Zentrum Dresden-Rossendorf (HZDR), das Karlsruher Institut für Technologie (KIT) und die Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen zusammen mit dem Forschungszentrum Jülich (FZJ). Modul B wurde vom Zentrum für Interdisziplinäre Risiko- und Innovationsforschung der Universität Stuttgart (ZIRIUS) bearbeitet. Die Gesamtkoordination der beidem Module erfolgte durch die Deutsche Akademie der Technikwissenschaften (acatech). Auf Grundlage einer Analyse der wissenschaftlich-technischen Aspekte durch Modul A wurden die gesellschaftlichen Implikationen bewertet und daraus in Modul B Kommunikations- und Handlungsempfehlungen für die zukünftige Positionierung von P&T formuliert. Im, vom HZDR koordinierten, Teilprojekt „Stand der Grundlagen- und technologischen Forschung“ wird eine Übersicht über den genannten Bereich gegeben. Eingeführt wird das Thema mit einer Kurzbeschreibung möglicher Reaktorsysteme für die Transmutation. Danach wird der Entwicklungsstand der Spezialbereiche Trennchemie, Sicherheitstechnologie, Beschleunigertechnologie Flüssigmetalltechnologie, Entwicklung von Spallationstargets, Transmutationsbrennstoffen und Werkstoffkonzepten sowie Konditionierung von Abfällen, beschrieben. Dies wird ergänzt durch Spezifika von Transmutationsanlagen beginnend bei physikalischen Grundlagen und Kerndesigns, über Reaktorphysik von Transmutationsanlagen, Simulationstools und die Entwicklung von Safety Approaches. Im Anschluss wird der Stand existierender Bestrahlungseinrichtungen mit schnellem Spektrum beschrieben. Nachfolgend werden basierend auf dem derzeitigen Stand von F&E die offenen Fragen und Forschungslücken in den einzelnen Teilbereichen – Wiederaufbereitung und Konditionierung, Beschleuniger und Spallationstarget, Reaktor – zusammengestellt und sowohl eine Strategie, als auch ein Fahrplan zur Schließung der Technology Gaps entwickelt. Zusätzlich werden die Hauptbeiträge, des HZDR zur Gesamtstudie beschrieben. Dies sind insbesondere die Beschreibungen der Möglichkeiten und Grenzen von P&T, die Herausforderungen an Bestrahlungseinrichtungen zur Transmutation und deren Effektivität, sowie Sicherheitsmerkmale beschleuniger-getriebener unterkritischer Systeme inclusive grundlegender Störfallbetrachtungen und Sicherheitscharakteristik.The main project, where this sub project contributed to, has been structured into two modules: module A (funded by the federal ministry of economics, managed by KIT) and module B (funded by the federal ministry of education and research, managed by acatech). Partners in module A were DBE TECHNOLOGY GmbH, the Gesellschaft für Anlagen- und Reaktorsicherheit mbH (GRS), the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the Karlsruher Institute of Technology (KIT) and the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen, in co-operation with the Forschungszentrum Jülich (FZJ). Modul B has been executed by the Zentrum für Interdisziplinäre Risiko- und Innovationsforschung der Universität Stuttgart (ZIRIUS). The overall coordination has been carried out by the Deutsche Akademie der Technikwissenschaften (acatech). The social implications have been evaluated in module B based on the analysis of the scientific and technological aspects in module A. Recommendations for communication and actions to be taken for the future positioning of P&T have been developed. In the project part, coordinated by HZDR – status of R&D – an overview on the whole topic P&T is given. The topic is opened by a short description of reactor systems possible for transmutation. In the following the R&D status of separation technologies, safety technology, accelerator technology, liquid metal technology, spallation target development, transmutation fuel and structural material development, as well as waste conditioning is described. The topic is completed by the specifics of transmutation systems, the basic physics and core designs, the reactor physics, the simulation tools and the development of Safety Approaches. Additionally, the status of existing irradiation facilities with fast neutron spectrum is described. Based on the current R&D status, the research and technology gaps in the topics: separation and conditioning, accelerator and spallation target, and reactor are characterized and a strategy as well as a roadmap for closing these gaps has been developed. In addition the major contributions of HZDR to the main project are described. The major parts are the description of the potential and the limits of P&T, the requirements and challenges for transmutation systems and the related efficiency, as well as the safety features of accelerator driven subcritical systems including the transient behavior and the safety characteristics

The Potential of Pressurised Water Reactors to Provide Flexible Response in Future Electricity Grids

The electricity market is undergoing significant change with the increasing deployment of Variable Renewable Energy Sources (VRES) and the adoption of policies to electrify transport, heating and industry, which will continue to increase demands on all conventional power plants including nuclear. The increase in VRES also puts additional emphasis on services such as inertia and frequency response that only conventional plants, including nuclear, are readily able to meet. This study discusses what factors limit the ability of nuclear power plants to provide flexible response and how the UK nuclear power plants might be affected by the changes in future demand profiles. The study focuses on what impact there will be on current Pressurised Water Reactor (PWR) plants, though it also considers Small Modular Pressurised Water Reactor plants which might offer benefits with respect to improved power manoeuvrability. The main finding is that the most important attribute is the minimum power level for long-term operation, followed by the speed at which the plants can be brought online (that is, both start-up rate and ramp rate during power operation). With respect to both of these attributes, new build future PWR plants could potentially achieve large and rapid power changes by dumping part of the steam directly into the condenser, bypassing the steam turbine. Discussions with plant operators highlighted that there is currently limited demand for flexible operation in the UK from nuclear plants when other power plants are readily available to partake in flexible operation. The lack of any requirement for nuclear plants to operate flexibly means that the UK lags behind France, for example, which has much more experience in nonstationary operation of nuclear power plants. The paper also draws attention to the fact that with increasing VRES, there will be fewer plants able to provide rotational inertia and therefore more emphasis on the role the remaining plants (which include nuclear) can play in maintaining grid stability.</jats:p

On the Dimensions Required for a Molten Salt Zero Power Reactor Operating on Chloride Salts

Molten salt reactors have gained substantial interest in the last years due to their flexibility and their potential for simplified closed fuel cycle operation for massive expansion in low-carbon electricity production, which will be required for a future net-zero society. The importance of a zero-power reactor for the process of developing a new, innovative rector concept, such as that required for the molten salt fast reactor based on iMAGINE technology, which operates directly on spent nuclear fuel, is described here. It is based on historical developments as well as the current demand for experimental results and key factors that are relevant to the success of the next step in the development process of all innovative reactor types. In the systematic modelling and simulation of a zero-power molten salt reactor, the radius and the feedback effects are studied for a eutectic based system, while a heavy metal rich chloride-based system are studied depending on the uranium enrichment accompanied with the effects on neutron flux spectrum and spatial distribution. These results are used to support the relevant decision for the narrowing down of the configurations supported by considerations on cost and proliferation for the follow up 3-D analysis. The results provide for the first time a systematic modelling and simulation approach for a new reactor physics experiment for an advanced technology. The expected core volumes for these configurations have been studied using multi-group and continuous energy Monte-Carlo simulations identifying the 35% enriched systems as the most attractive. This finally leads to the choice of heavy metal rich compositions with 35% enrichment as the reference system for future studies of the next steps in the zero power reactor investigation. An alternative could be the eutectic system in the case the increased core diameter is manageable. The inter-comparison of the different applied codes and approaches available in the SCALE package has delivered a very good agreement between the results, creating trust into the developed and used models and methods.</jats:p

Entwicklung einer Version des Reaktordynamikcodes DYN3D für Hochtemperaturreaktoren: Abschlussbericht

Basierend auf dem Reaktordynamikcode DYN3D für LWR, wurde die Codeversion DYN3D-HTR für das Blockkonzept eines graphit-moderierten, helium-gekühlten Hochtemperaturreaktors entwickelt. Diese Entwicklung umfasst die: • methodische Weiterentwicklung der 3D stationären Neutronenflussberechnung für hexagonale Geometrie (HTR-Brennelement-Blöcke), • Generierung von Wirkungsquerschnittsdaten unter Berücksichtigung der doppelten Heterogenität, • Modellierung der Wärmeleitung und des Wärmetransports in der Graphitmatrix. Die nodale SP3-Neutronentransport-Methode in DYN3D wurde auf hexagonale Brennelementgeometrie erweitert. Es wird eine Unterteilung der Hexagone in Dreiecke vorgenommen, so dass die Verfeinerung hexagonaler Strukturen untersucht werden kann. Die Verifikation erfolgte durch Vergleiche mit Monte-Carlo-Referenzlösungen. Für die Behandlung der doppelten Heterogenität der Brennelementstruktur bei Homogenisierung der Wirkungsquerschnitte wurden neue Methoden entwickelt. Zum einen wurde ein zweistufiges Homogenisierungsverfahren basierend auf der Methode der sog. Reactivity Equivalent Transformation (RPT) weiterentwickelt. Zum anderen ermöglichte die Verfügbarkeit des neuen Monte-Carlo-Codes SERPENT die Anwendung eines einstufigen Verfahrens, wobei die 3D heterogenen Strukturen in einem Rechenschritt konsistent erfasst werden können. Weiterhin wur-de in DYN3D ein 3D Wärmeleitungsmodell implementiert, das den radialen und axialen Wärmetransport in der Graphitmatrix beschreiben kann. DYN3D-HTR wurde schließlich anhand der Testfälle für Reaktivitätstransienten erprobt. Die Verifikation erfolgte durch Vergleich zwischen 3D und 1D Berechnung der Wärmeleitung. Schließlich wurde DYN3D mit dem CFD-Code ANSYS-CFX gekoppelt, um auch dreidimensionale Strömungen in Reaktorkernen berechnen zu können. Der Kern wird als poröser Körper modelliert. Die Kopplung wurde an anhand von 2 Testbeispielen, dem Auswurf eines Steuerstabes und einer lokalen Strömungsblockade in einem Brennelement, erprobt

The Higgs as a Portal to Plasmon-like Unparticle Excitations

12 LaTeX pages, 2 figures.-- Published in: JHEP04(2008)028.-- Final full-text version available at: http://dx.doi.org/10.1088/1126-6708/2008/04/028.A renormalizable coupling between the Higgs and a scalar unparticle operator O_U of non-integer dimension d_U<2 triggers, after electroweak symmetry breaking, an infrared divergent vacuum expectation value for O_U. Such IR divergence should be tamed before any phenomenological implications of the Higgs-unparticle interplay can be drawn. In this paper we present a novel mechanism to cure that IR divergence through (scale-invariant) unparticle self-interactions, which has properties qualitatively different from the mechanism considered previously. Besides finding a mass gap in the unparticle continuum we also find an unparticle pole reminiscent of a plasmon resonance. Such unparticle features could be explored experimentally through their mixing with the Higgs boson.Work supported in part by the European Commission under the European Union through the Marie Curie Research and Training Networks “Quest for Unification” (MRTN-CT- 2004-503369) and “UniverseNet” (MRTN-CT-2006-035863); by the Spanish Consolider- Ingenio 2010 Programme CPAN (CSD2007-0042); by a Comunidad de Madrid project (P-ESP-00346) and by CICYT, Spain, under contracts FPA 2007-60252 and FPA 2005-02211