Nuclear Production of Hydrogen, Fourth Information Exchange ...

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A URANIUM THERMOCHEMICAL CYCLE FOR HYDROGEN PRODUCTION Introduction Thermochemical processes are promising large-scale methods to produce hydrogen because the energy input is in the form of lower-cost heat rather than more expensive electricity. Nuclear Energy is a primary candidate to supply that heat (Forsberg, 2009). In a thermochemical process, heat plus water yields hydrogen and oxygen, all other chemicals within the process being recycled. A thermochemical cycle should: i) operate at high thermodynamic efficiency; ii) have a small number of process steps; iii) not have a significant inventory of volatile or hazardous chemicals that can cause off-site risks; iv) operate at reasonable temperatures. No existing thermochemical cycle meets all of these criteria (Brown, 2000). There is a need for better thermochemical cycles. Uranium exists in many valence states, has overlapping 6d and 5f electrons, and a complex chemistry – exactly the chemistry one would investigate for development of a thermochemical cycle. However, there has been almost no consideration of using uranium in thermochemical cycles because it was thought to be expensive or unusable because of its radioactivity. The nuclear fuel cycle involves mining natural uranium (0.7% 235 U) followed by enrichment of the uranium (3-5% 235 U) in the 235 U isotope for use in nuclear fuels. The enrichment process has produced as a by-product over a million tonnes of excess depleted uranium (~0.3% 235 U) available at little or no cost. The depleted uranium is primarily 238 U with a half-life of several billion years; i.e. its radioactivity is extremely low. The primary handling hazard is that it is a heavy metal, not that it is radioactive. Based on these considerations, there are strong incentives to examine possible uranium thermochemical cycles. An investigation was undertaken at Oak Ridge National Laboratory to find and develop a thermochemical cycle based on uranium (Ferrada, 2009; US Patent, 2008). This paper describes the recent development of a new uranium thermochemical cycle (UTC). Process description A series of UTC were investigated using a combination of thermodynamic analysis and experiments. The thermodynamics of alternative cycles were analysed using Outokumpu’s HSC 5.0 Chemistry software computer code version 5.11 (Outokumpu, 2002). As reported elsewhere, the experiments were used to demonstrate the major process steps with recycle of the uranium. Most experiments were conducted in an alumina-lined tube furnace with the uranium in an alumina boat. Hydrogen gases were produced and measured. Reduction of CuO to copper metal, determined by weight loss, was the primary method used to measure the amount of reductant produced. X-ray diffraction analysis was used in most cases to confirm the uranium species. The results of thermodynamic analysis and experiments led to the UTC shown in Figure 1 that uses valence state transitions and the formation of oxidised and reduced uranium species to split H 2 O for the production of H 2 . Some of the chemical reactions are new but most of the chemical reactions are used industrially within the uranium industry. In the hydrogen production step, triuranium octoxide (U 3 O 8 ) is initially reacted with sodium carbonate (Na 2 CO 3 ) and steam to generate hydrogen and sodium diuranate (Na 2 U 2 O 7 ) at 600°C and above. This can be done under mild pressures (~1 atmosphere) with an excess of carbon dioxide (CO 2 ) in an inert carrier gas, such as argon (Ar). Although not demonstrated in this work, the hydrogen can be separated from these gases by selective membranes or pressure swing adsorption and/or cryogenic separation methods. The steam is condensed to recover heat, and the excess CO 2 and carrier gases are recycled. Only this first step in the UTC process is unique, the remaining two steps are conventional processes in the uranium processing industry (Edwards, 2000). In the second step, sodium diuranate (Na 2 U 2 O 7 ) is converted to uranyl ammonium tricarbonate [UO 2 CO 3·2(NH 4 ) 2 CO 3 ]. The sodium diuranate is dissolved in an alkaline carbonate solution. This uranium solution is passed through a column of Dowex 1-X resin. The uranium is loaded onto the ion exchange resin while the sodium passes through the column. The Na 2 CO 3 can be recovered and recycled from the uranium-free raffinate. The uranium is then stripped from the resin using a solution of ammonium carbonate [(NH 4 ) 2 CO 3 ]. The resulting uranium solution is dried to produce uranyl ammonium tricarbonate [UO 2 CO 3·2(NH 4 ) 2 CO 3 ]. 454 NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010
A URANIUM THERMOCHEMICAL CYCLE FOR HYDROGEN PRODUCTION Figure 1: Uranium thermochemical cycle for the production of hydrogen In the third step, the uranyl ammonium tricarbonate [UO 2 CO 3·2(NH 4 ) 2 CO 3 ] is heated to 400°C to generate U 3 O 8 , oxygen, ammonia (NH 3 ), carbon dioxide (CO 2 ) and water (H 2 O). The U 3 O 8 , NH 3 , CO 2 and H 2 O can be recycled and used in the next H 2 production cycle. Oxygen is a by-product from the cycle. Observations and conclusions Initial thermodynamic and experimental studies have found a new thermochemical cycle based on uranium. The operating conditions are mild and most of the steps are commercially used in the uranium processing industry. For several of the process steps, there are multiple process options. Additional analysis and experimental work is required before engineering viability (versus scientific proof of principle) can be determined with reasonably credible estimates of efficiencies and economics. NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010 455
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Nuclear Science 2010 Nuclear Produc
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ORGANISATION FOR ECONOMIC CO-OPERAT
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TABLE OF CONTENTS Table of contents
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TABLE OF CONTENTS Y. Gong, E. Chalk
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EXECUTIVE SUMMARY Executive summary
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EXECUTIVE SUMMARY steam turbine, in
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EXECUTIVE SUMMARY sulphur depositio
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EXECUTIVE SUMMARY affords saving 35
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EXECUTIVE SUMMARY safety assessment
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EXECUTIVE SUMMARY The question was
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CHANGING THE WORLD WITH HYDROGEN AN
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NUCLEAR HYDROGEN PRODUCTION PROGRAM
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NUCLEAR HYDROGEN PRODUCTION PROGRAM
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FRENCH RESEARCH STRATEGY TO USE NUC
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PRESENT STATUS OF HTGR AND HYDROGEN
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STATUS OF THE KOREAN NUCLEAR HYDROG
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THE CONCEPT OF NUCLEAR HYDROGEN PRO
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CANADIAN NUCLEAR HYDROGEN R&D PROGR
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APPLICATION OF NUCLEAR-PRODUCED HYD
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STATUS OF THE INL HIGH-TEMPERATURE
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HIGH-TEMPERATURE STEAM ELECTROLYSIS
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MATERIALS DEVELOPMENT FOR SOEC Mate
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A METALLIC SEAL FOR HIGH-TEMPERATUR
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DEGRADATION MECHANISMS IN SOLID OXI
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CAUSES OF DEGRADATION IN A SOLID OX
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70 μm CAUSES OF DEGRADATION IN A S
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NUCLEAR HYDROGEN USING HIGH TEMPERA
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SESSION III: THERMOCHEMICAL SULPHUR
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CEA ASSESSMENT OF THE SULPHUR-IODIN
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STATUS OF THE INERI SULPHUR-IODINE
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INFLUENCE OF HTR CORE INLET AND OUT
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EXPERIMENTAL STUDY OF THE VAPOUR-LI
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DEVELOPMENT OF HI DECOMPOSITION PRO
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SOUTH AFRICA’S NUCLEAR HYDROGEN P
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INTEGRATED LABORATORY SCALE DEMONST
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DEVELOPMENT STATUS OF THE HYBRID SU
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RECENT CANADIAN ADVANCES IN THE THE
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AN OVERVIEW OF R&D ACTIVITIES FOR T
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STUDY OF THE HYDROLYSIS REACTION OF
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DEVELOPMENT OF CuCl-HCl ELECTROLYSI
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EXERGY ANALYSIS OF THE Cu-Cl CYCLE
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CaBr 2 HYDROLYSIS FOR HBr PRODUCTIO
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SESSION V: ECONOMICS AND MARKET ANA
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DEVELOPMENT OF THE HYDROGEN ECONOMI
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NUCLEAR H 2 PRODUCTION - A UTILITY
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ALKALINE AND HIGH-TEMPERATURE ELECT
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THE PRODUCT OF HYDROGEN BY NUCLEAR
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SUSTAINABLE ELECTRICITY SUPPLY IN T
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PROHYTEC, THE FRENCH INDUSTRIAL PLA
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NHI ECONOMIC ANALYSIS OF CANDIDATE
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MARKET VIABILITY OF NUCLEAR HYDROGE
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POSSIBILITY OF ACTIVE CARBON RECYCL
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NUCLEAR SAFETY AND REGULATORY CONSI
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TRANSIENT MODELLING OF S-I CYCLE TH
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PROPOSED CHEMICAL PLANT INITIATED A
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CONCEPTUAL DESIGN OF THE HTTR-IS NU
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USE OF PSA FOR DESIGN OF EMERGENCY
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Page 405 and 406: USE OF PSA FOR DESIGN OF EMERGENCY
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Page 409 and 410: HEAT PUMP CYCLE BY HYDROGEN-ABSORBI
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Page 462 and 463: LIST OF PARTICIPANTS REYTIER, Magal
Page 464 and 465: LIST OF PARTICIPANTS BROWN, Nichola
Page 466: LIST OF PARTICIPANTS SINK, Carl US
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