P. Norajitra

Power plant conceptual studies in Europe

The European fusion programme is ‘reactor oriented’ and it is aimed at the successive demonstration of the scientific, the technological and the economic feasibility of fusion power. The European Power Plant Conceptual Study (PPCS) has been a study of conceptual designs of five commercial fusion power plants and the main emphasis was on system integration. It focused on five power plant models which are illustrative of a wider spectrum of possibilities. They are all based on the tokamak concept and they have approximately the same net electrical power output, 1500 MWe. These span a range from relatively near-term, based on limited technology and plasma physics extrapolations, to an advanced conception. The PPCS allows one to clarify the concept of DEMO, the device that will bridge the gap between ITER and the first-of-a-kind fusion power plant. An assessment of the PPCS models with limited extrapolations highlighted a number of issues that must be addressed to establish the DEMO physics and technological basis.

Conceptual design of the dual-coolant blanket in the frame of the EU power plant conceptual study

Abstract The dual-coolant (DC) blanket—characterised by its simple construction, simple function, and high thermal efficiency—is one of the EU advanced blanket concepts to be investigated in the frame of the long-term power plant conceptual study (PPCS). Its basic concept is based on the use of helium-cooled ferritic steel structure, the self-cooled Pb–17Li breeding zone, and SiC/SiC flow channel inserts, serving as electrical and thermal insulators. The present work on PPCS is drawn extensively on the preparatory study on plant availability carried out in 1999 with an objective to perform the conceptual design of the DC blanket concept where some details are to be selected in accordance with the overall strategy, which allows an extrapolation of the present knowledge between the near-term solutions (helium-cooled pebble bed (HCPB), water-cooled lead–lithium (WCLL) blanket concepts), and the very advanced self-cooled Pb–17Li SiC/SiC (SCLL) blanket concept. In the PPCS the reactor power is adapted to a typical size of commercial reactors of 1500 MWe which requires iterative calculations between the blanket layout and the system code analysis. The results of the first iteration are reported. This work is under the coordination of FZK in co-operation with CEA, EFET, IBERTEF, UKAEA, VTT Processes and VR.

The EU advanced dual coolant blanket concept

Abstract The advanced dual coolant (A-DC) blanket is one of the EU advanced concepts to be investigated in the frame of the long-term power plant conceptual study (PPCS). Its basic concept—following the ARIES-ST concept—is based on the use of helium-cooled ferritic steel structure, the self-cooled Pb–17Li breeding zone, and SiC/SiC flow channel inserts. The latter serves as electrical and thermal insulators and therefore minimize the pressure losses and enable a relatively high Pb–17Li exit temperature leading to a high thermal efficiency. The present work on PPCS is drawn extensively on the preparatory study on plant availability (PPA) carried out in 1999 where a maximum neutron wall load of 5 MW/m2 (corresponding maximum surface heat load of 0.9 MW/m2) was given in the reference case of the A-DC blanket. In the following stage of PPCS the A-DC blanket is normalized and adapted to a typical size of commercial reactors (e.g. 1500 MWe) which requires iterative calculations between the blanket layout and the system code analysis. The status of the work with some idea improvements is reported.

The EU advanced lead lithium blanket concept using SiCf/SiC flow channel inserts as electrical and thermal insulators

Abstract Preparatory work on the EU advanced dual coolant (A-DC) blanket concept using SiCf/SiC flow channel inserts as electrical and thermal insulators has been carried out at the Forschungszentrum Karlsruhe in co-operation with CEA (SiCf/SiC composite-related issues) as a conceptual design proposal to the EU fusion power plant study planned to be launched in 2001 within the framework of the EU fusion programme having the main objective of specifying the characteristics of an attractive and viable commercial D –T fusion power plant. The basic principles and the study method for the A-DC blanket concept are presented in this report. The results of this study show that the A-DC blanket concept has a high potential for further development due to its high thermal efficiency and its simple concept solution.

Self-cooled blanket concepts using Pb7Li as liquid breeder and coolant

Abstract A blanket design concept using Pb17Li eutectic alloy as both breeder material and coolant is described. Such a self-cooled blanket for the boundary conditions of a DEMO-reactor is under development at the Kernforschungszentrum Karlsruhe (KfK) in the frame of the European blanket development program. Results of investigations in the areas of design, neutroncs, magneto-hydrodynamics, thermo-mechanics, ancillary loop systems, and safety are reported. Based on recent progress, it can be concluded that the boundary conditions of a DEMO-reactor can be met, tritium self-sufficiency can be obtained without using beryllium as an additional neutron multiplier, and tritium inventory and permeation are acceptably low. However, to completely judge the feasibility of the proposed concept, further studies are necessary to obtain a better understanding of the magneto-hydrodynamic phenomena and their effects on the thermal-hydraulic performance of a fusion reactor blanket.

European development of He-cooled divertors for fusion power plants

Helium-cooled divertor concepts are considered suitable for use in fusion power plants for safety reasons, as they enable the use of a coolant compatible with any blanket concept, since water would not be acceptable, e.g. in connection with ceramic breeder blankets using large amounts of beryllium. Moreover, they allow for a high coolant exit temperature for increasing the efficiency of the power conversion system. Within the framework of the European power plant conceptual study, different helium-cooled divertor concepts based on different heat transfer mechanisms are being investigated at ENEA Frascati, Italy, and Forschungszentrum Karlsruhe, Germany. They are based on a modular design which helps reduce thermal stresses. The design goal is to withstand a high heat flux of about 10–15 MW m−2, a value which is considered relevant to future fusion power plants to be built after ITER. The development and optimization of the divertor concepts require an iterative design approach with analyses, studies of materials and fabrication technologies and the execution of experiments. These issues and the state of the art of divertor development shall be the subject of this report.

DUAL COOLANT LIQUID METAL BREEDER BLANKET

A blanket concept for a fusion DEMO-reactor combining self-cooling of the liquid metal breeder zone with helium-cooling of the first wall is described. Main emphasis has been placed on high safety and reliability features and on a simple, stiff blanket structure. Results of the analysis in the fields of neutronics, thermal-hydraulics and magneto-hydro-dynamics are reported.

HIP experiments on the first wall and cooling plate specimens for the EU HCPB blanket

Abstract First wall and cooling plates are considered the most important structural parts of the EU HCPB blanket concept which is based on the use of ferritic–martensitic steel as structural material, Li 4 SiO 4 pebbles as breeder material, beryllium pebbles as neutron multiplier, and 8 MPa helium as coolant. Both the first wall and cooling plates contain complex arrays of internal He coolant channels. The favourite manufacturing technology is diffusion welding of two halves of plates applying the hot isostatic pressure (HIP) welding method that allows uniform distribution of the pressure acting on the outer surfaces of the welding objects. The HIP experiment was started with small MANET specimens with internal coolant channels. The objective of this work is to investigate the appropriate HIP technique, boundary conditions, and parameters in order to achieve good mechanical properties of the welding joints as well as to achieve a transition to test specimens of larger dimensions.

European Fusion Power Plant Studies

Abstract The European Power Plant Conceptual Study (PPCS) reported in the summer of 2004. Several conceptual designs (“Models”) for commercial fusion power plants were developed, spanning a range from relatively near term to more substantial extrapolations. The parameters of the Models were chosen by systems analysis to be economically optimal, given the assigned constraints on plasma and technology performance. The conceptual designs were developed in some detail and analyses were made of their safety, environmental impacts and economic performance. The calculated cost of generating electricity from the Models is in the range of published estimates for the future costs from other sources. Even the near-term Models are economically viable. External costs are very low, for all the Models: similar to wind power and much less than for fossil fuels. Economic optimization of the designs did not jeopardize their safety and environmental performance. All the Models proved to have the attractive and substantial safety and environmental advantages found in earlier studies, now established with greater confidence.

Innovations in molding technologies for microfabrication

Micromolding is a key technology for the economic production of components for microsystems. It is applied in several manufacturing techniques including the LIGA process. Especially MicroInjection Molding allows cost-effective large-scale production of components for many applications to be used in microsystems technology. Using special molding machines, lateral dimensions in the micrometer range, structural details down to 200nm and maximum aspect ratios of more than 20 are achieved. Examples for applications are PSU-made housings for microfluidic systems or microcomponents made of PMMA for cardiac catheters. PC or LCP are appropriate materials for interconnection devices in microoptics and electronics. Other examples are injection molded lost plastic molds for electroforming or electroless plating of metal microstructures. An important economic factor is the optimization of the molding process and tool using different simulation techniques. Recently, novel techniques for manufacturing metal or ceramic microstructures were developed by adapting Powder Injection Molding to microtechnologies. Using commercially available feedstocks, microstructures were made of metals or ceramics. Rapid manufacturing of microcomponents is achieved by the so-called Photomolding process using reactive polymer resins as photocurable material and e.g. mold inserts fabricated by laser ablation. The addition of micro- or nanosized ceramics to the resin allows the molding of filled composite with enhanced mechanical properties. Subsequent debindering and sintering steps yield the pure ceramic microcomponents.