Neutronic study on a magnetic fusion reactor using protective liquid wall of thorium molten salts (original) (raw)
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Selection Criteria for Fusion Reactor Structures
Journal of Thermal Engineering
Fusion energy is the ultimate energy to cover Mankind's energy needs forever. However, taming the fusion energy is the greatest technological challenge the humanity is facing. Development of structural materials to withstand against the extreme conditions in the course of fusion power plant operation is one of the toughest nuts to be cracked. A great number of structural materials have been investigated for fusion reactor applications, such as steels (austenitic stainless steels and ferritic/martensitic steels), vanadium alloys, refractory metals and alloys (niobium alloys, tantalum alloys, chromium and chromium alloys, molybdenum alloys, tungsten and tungsten alloys), and composites (SiCf/SiC and Carbon Fibre Composite CFC composites). Steels have extensive technological data base and significantly lower cost compared to other refractory metals and alloys. Ferritic steels and modified austenitic stainless (Ni and Mo free) have relatively low residual radioactivity. However, steels cannot withstand high neutron wall loads to build an economically competitive fusion reactor. Some refractory metals and alloys (niobium alloys, tantalum alloys, molybdenum alloys, tungsten and tungsten alloys) can withstand high neutron wall loads. But, in addition to their very limited technological data base, they have high residual radioactivity and prohibitively high production costs. A protective, flowing liquid zone to protect the first wall of a fusion reactor from direct exposure to the fusion reaction products could extend the lifetime of the first wall to the expected lifetime of the fusion reactor. In that context, a fusion-fission (hybrid) with a multi-layered spherical blanket has been investigated, which is composed of a first wall made of oxide dispersed steel (ODS, 2 cm); neutron multiplier and coolant zone made of LiPb; ODS-separator (2 cm); a molten salt FLIBE coolant and fission zone; ODS-separator (2 cm); graphite reflector. Calculations are conducted for a liquid wall with variable thickness, containing Flibe + heavy metal salt (UF4 or ThF4) is used for first wall protection. The content of heavy metal salt is chosen as 4 and 12 mol%. A flowing wall with a thickness of ~ 60 cm can extend the lifetime of the solid first wall structure to a plant lifetime of 30 years for 9Cr-2WVTa and V-4Cr-4Ti, whereas the SiCf/SiC composite as first wall needs a flowing wall with a thickness of ~ 85 cm to maintain the radiation damage limit.
Liquid wall options for tritium-lean fast ignition inertial fusion energy power plants
Fusion Engineering and Design, 2002
In an inertial fusion energy (IFE) thick-liquid chamber design such as HYLIFE-II, a molten-salt is used to attenuate neutrons and protect the chamber structures from radiation damage. In the case of a fast ignition inertial fusion system, advanced targets have been proposed that may be self-sufficient in terms of tritium breeding (i.e. the amount of tritium bred in target exceeds the amount burned). This aspect allows for greater freedom when selecting a liquid for the protective blanket, given that lithium-bearing compounds are no longer required. Materials selection may now be based upon other characteristics, such as safety and environmental (S&E), pumping power, corrosion, and vapor pressure, along with others. The present work assesses the characteristics of many single, binary, and ternary molten-salts and liquid metals using the NIST Properties of Molten Salts Database. As an initial screening, liquids were evaluated for their S&E characteristics, which included an assessment of waste disposal rating (WDR), contact dose, and radioactive afterheat. Liquids that passed the S&E criteria were then evaluated for required pumping power. The pumping power was calculated using three components: velocity head losses, frictional losses, and lifting power. The results of the assessment are used to identify those materials that are suitable for potential liquid-chamber fast-ignition IFE concepts, from both the S&E and pumping power perspective. Recommendations for further analysis are also made. # (S. Reyes). Fusion Engineering and Design 63 Á/64 (2002) 635 Á/640
A fusion reactor design with a liquid first wall and divertor
Fusion Engineering and Design, 2004
Within the magnetic fusion energy program in the US, a program called APEX is investigating the use of free flowing liquid surfaces to form the inner surface of the chamber around the plasma. As part of this work, the APEX Team has investigated several possible design implementations and developed a specific engineering concept for a fusion reactor with liquid walls. Our approach has been to utilize an already established design for a future fusion reactor, the ARIES-RS, for the basic chamber geometry and magnetic configuration, and to replace the chamber technology in this design with liquid wall technology for a first wall and divertor and a blanket with adequate tritium breeding. This paper gives an overview of one design with a molten salt (a mixture of lithium, beryllium and sodium fluorides) forming the liquid surfaces and a ferritic steel for the structural material of the blanket. The design point is a reactor with 3840 MW of fusion power of which 767 MW is in the form of energetic particles (alpha power) and 3073 MW is in the form of neutrons. The alpha plus auxiliary power total 909 MW of which 430 MW is radiated from the core mostly onto the first wall and the balance flows into the edge plasma and is distributed between the first wall and the divertor. In pursuing the application of liquid surfaces in APEX, the team has developed analytical tools that are significant achievements themselves and also pursued experiments on flowing liquids. This work is covered elsewhere, but the paper will also note several such areas to indicate the supporting science behind the design presented. Significant new work in modeling the plasma edge to understand the interaction of the plasma with the liquid walls is one example. Another is the incorporation of magneto-hydrodynamic (MHD) effects in fluid modeling and heat transfer.
On the exploration of innovative concepts for fusion chamber technology
Fusion Engineering and Design, 2001
This study, called APEX, is exploring novel concepts for fusion chamber technology that can substantially improve the attractiveness of fusion energy systems. The emphasis of the study is on fundamental understanding and advancing the underlying engineering sciences, integration of the physics and engineering requirements, and enhancing innovation for the chamber technology components surrounding the plasma. The chamber technology goals in APEX include: (1) high power density capability with neutron wall load \ 10 MW/m 2 and surface heat flux \ 2 MW/m 2 , (2) high power conversion efficiency ( \ 40%), (3) high availability, and (4) simple technological and material constraints. Two classes of innovative concepts have emerged that offer great promise and deserve further research and development. The first class seeks to eliminate the solid ''bare'' first wall by flowing liquids facing the plasma. This liquid wall idea evolved during the APEX study into a number of concepts based on: (a) using liquid metals (Li or Sn-Li) or a molten salt (Flibe) as the working liquid, (b) utilizing electromagnetic, inertial and/or other types of forces to restrain the liquid against a backing wall and control the hydrodynamic flow configurations, and (c) employing a thin ( 2 cm) or thick ( 40 cm) liquid layer to remove the surface heat flux and attenuate the neutrons. These liquid wall concepts have some common features but also have widely different issues and merits. Some of the attractive features of liquid walls include the potential for: (1) high power density capability; (2) higher plasma b and stable physics regimes if liquid metals are used; (3) increased disruption survivability; (4) reduced volume of radioactive waste; (5) reduced radiation damage in structural materials; and (6) higher availability. Analyses show that not all of these potential advantages may be realized simultaneously in a single concept. However, the realization of only a subset of these advantages will result in remarkable progress toward attractive fusion energy systems. Of the many scientific and engineering issues for liquid walls, the most important are: (1) plasma-liquid interactions including both plasma-liquid surface and liquid wall-bulk plasma interactions; (2) hydrodynamic flow configuration control in complex geometries including penetrations; and (3) heat transfer at free surface and temperature control. The second class of concepts focuses on ideas for extending the capabilities, particularly the power density and operating temperature limits, of solid first walls. The most promising idea, called EVOLVE, is based on the use of a high-temperature refractory alloy (e.g. W -5% Re) with an innovative cooling scheme based on the use of the heat of vaporization of lithium. Calculations show that an evaporative system with Li at 1 200°C can remove the goal heat loads and result in a high power conversion efficiency. The vapor operating pressure is low, resulting in a very low operating stress in the structure. In addition, the lithium flow rate is about a factor of ten lower than that required for traditional self-cooled first wall/blanket concepts. Therefore, insulator coatings are not required. Key issues for EVOLVE include: (1) two-phase heat transfer and transport including MHD effects; (2) feasibility of fabricating entire blanket segments of W alloys; and (3) the effect of neutron irradiation on W.
Radiation damage studies on the first wall of a HYLIFE-II type fusion breeder
Energy Conversion and Management, 2005
The radiation damage on the first wall [made of (1) a ferritic steel (9Cr-2WVTa), (2) a vanadium alloy (V-4Cr-4Ti) and (3) SiC f /SiC composite] of an inertial fusion energy (IFE) reactor of HYLIFE-II type is investigated. A protective liquid wall with variable thickness, containing Flibe + heavy metal salt (UF 4 or ThF 4) is used for first wall protection. The content of heavy metal salt is chosen as 4 and 12 mol%. Neutron transport calculations are performed with the aid of the SCALE4.3 System by solving the Boltzmann transport equation with the XSDRNPM code in 238 energy groups and S 8-P 3 approximation. A flowing wall with a thickness of 60cmcanextendthelifetimeofthesolidfirstwallstructuretoaplantlifetimeof30yearsfor9Cr−2WVTaandV−4Cr−4Ti,whereastheSiCf/SiCcompositeasfirstwallneedsaflowingwallwithathicknessof60 cm can extend the lifetime of the solid first wall structure to a plant lifetime of 30 years for 9Cr-2WVTa and V-4Cr-4Ti, whereas the SiC f /SiC composite as first wall needs a flowing wall with a thickness of 60cmcanextendthelifetimeofthesolidfirstwallstructuretoaplantlifetimeof30yearsfor9Cr−2WVTaandV−4Cr−4Ti,whereastheSiCf/SiCcompositeasfirstwallneedsaflowingwallwithathicknessof85 cm to maintain the radiation damage limit. Substantial extra revenue can be gained through the insertion of a heavy metal salt constituent into Flibe, which allows breeding fissile fuel for external reactors and increasing energy multiplication
Ann Nucl Energ, 2003
A protective, 60 cm thick flowing liquid wall coolant is investigated as energy carrier, and fusile and fissile breeder medium in an inertial fusion energy (IFE) reactor. Flibe as the main constituent is mixed with increased mole-fractions of heavy metal salt (ThF 4 and UF 4) starting with 2 mol% up to 12 mol%. For a plant operation period of 30 years, radiation damage values were found as DPA= 65 for 2 mol% heavy metal in the coolant, and remain practically constant with increasing heavy metal fraction, well below the presumable limit of DPA=100. Helium production values are calculated as 270 appm for 2 mol% heavy metal fraction, also being far below the limit value of 500 appm and remain at the same level with increasing heavy metal fraction. Such a flowing protective liquid wall extents the lifetime of the rigid first wall structure to a plant lifetime of 30 years. Fissionable metal salt in the flowing liquid enables one to breed high quality fissile fuel for external reactors by a self-sustaining tritium breeding for the fusion plant and increases plant power output.
Laser and Particle Beams, 1993
Even though general conclusions cannot be derived for all the protection schemes in inertial confinement fusion (ICF) reactors, the feasibility of the ferritic alloy HT-9 as the main component of the first structural wall (FSW) in ICF facilities using thin-film Li17Pb83 liquid protection, flowing through porous tubes (INPORT), can be demonstrated as a solution in terms of radiation damage. Swelling and shift in the ductile-brittle transition temperature (DBTT) can be analyzed using the results of experimental fast-fission reactors, which are demonstrated to be good experimental tools in that ICF range. The good performance of HT-9 is remarkable. The generation of new solid transmutants and the depletion of initial constituents need also be considered. Further, a reduced-activation HT-9 (niobium-free) has been studied using recycling and shallow land burial (SLB) criteria. The recycling using that HT-9 is shown to be not feasible, as is SLB waste disposal. The unexpected critical rol...
Compendium of Papers by the Fusion Reactor Studies Group
A cost-based systems model is used to reexamine resistivecoil tokamak power reactors and to examine physics, engineering, and operational tradeoffs needed to project an economically competitive system. The developmental, technological, costs, and operational issues of copper-coil reactors are revisited in light of recent engineering innovations and new developments in physics. The critical isues of engineering innovation (neutronics related) are discussed.
Review of blanket designs for advanced fusion reactors
Fusion Engineering and Design, 2008
The dominating fraction of the power generated by fusion in the reactor is captured by neutron moderation in the blanket surrounding the plasma. From this, the efficiency of the fusion plant is predominated by the technologies applied to make electricity or hydrogen from the neutrons. The main blanket concepts addressed in this paper are advanced ceramic breeder concepts, dual coolant blankets as well as self-cooled liquid metal and Flibe blankets. Two important questions that are addressed are: (i) Can we draw a bottom line conclusion on the most promising concept(s)? (ii) What are the common issues to be resolved independently from individual design and layout proposals to define a feasible route towards advanced fusion reactors? For ceramic breeder concepts, a key issue in the long term could be the limitation of beryllium as the considered multiplier in terms of world sources and achievable temperature levels. For liquid metal blankets, attractive long-term visions have been developed but major technological challenges also exist for the in-vessel blanket technology and the corresponding subsystems. The paper proposes a strategic conclusion derived from the review of blanket designs for advanced fusion reactors.