Abstract

This report documents the main results of the Conceptual Design Evaluation (CDE) on the International Fusion Materials Irradiation Facility (IFMIF), conducted during 1997 and 1998. Following the recommendations of the FPCC in January 1997, the activities proposed by the IEA/IFMIF Subcommittee for the CDE phase were, according to the limited funding, to concentrate mainly on a critical evaluation of the design developed during the preceding Conceptual Design Activity (CDA) phase and on improvements of key devices and instrumentation tools. The IFMIF activities continues to be coordinated by the international leadership team already used for the CDA. This CDE report follows basically the work breakdown structure of the project and therefore has the four major sections Test Facilities, Target Facilities, Accelerator Facilities and Design Integration. A major outcome of the CDE was, that in all areas the conceptual design was confirmed and extended, with no substantial changes.

Test Facilities: Special emphasis was put on the validation and improvement of the high-flux test module (HFTM) for structural materials irradiation and the medium-flux test module (MFTM) for tritium release experiments. The HFTM design has been extended mainly to implement additional requirements of the users’ community and to take into account more recent flux/volume and heat deposition calculations from the neutronics. Without neutron reflector approximately 15% burn up and 7.5 dpa can be achieved annually in the medium flux position in a typical breeder ceramic. Significant progress has been achieved in the neutronics with respect to the source term of the D-Li reaction, the 20-50 MeV data evaluation and the assessment of on-line neutron/gamma monitors. An IFMIF simulation experiment was performed with 40 MeV deuterons for measuring the neutron yield as well as the Be-7 and tritium production yield in lithium. User specific tasks have been added because of their relevance for the overall IFMIF performance. These tasks included an evaluation of the Li-target backwall, small-specimen test technology development and a very detailed re-evaluation of irradiation parameters. This re-evaluation is based on extended MCNP transport code calculation and has shown that all relevant irradiation parameters of the IFMIF HFTM matches very well with the related ITER and DEMO values.

Target Facilities: During the CDE phase significant improvements of the conceptual design have been made that include (i) an optimization of the overall system design, (ii) extended thermo-hydraulic calculations to assess the Li jet stability under different conditions, (iii) a probabilistic evaluation of accident sequences showing very low values for potential accident probabilities, and (iv) a detailed outline of lithium purification and on-line monitor systems. As a major result, a notable cost reduction has been achieved by decreasing the total volume of the lithium cells by 37%. A hydraulics analysis for the stability of the target lithium jet has shown in accordance with a water simulation experiment, that the convection flows on both sides of the beam footprint and therefore does not influence the jet stability.

Accelerator Facilities: During the CDE, the three major task areas were (i) RF system development and test, (ii) injector system development and test and (iii) all other conceptual design activity-With respect to high current cw accelerator experience, the IFMIF project presently gains from relevant results in other accelerator projects. E.g. at the University of Frankfurt a 200 mA cw 94% proton beam (corresponds by scaling to 140 mA deuterons) was extracted in July 1998 through a 8 mm aperture, and also at CEA-Sacley a 126 mA cw proton beam was transported recently through a 10 mm aperture for a long operation time with 96% availability. Finally, within a US program, a 100 mA cw proton linac prototype to about 10 MeV is under construction. Relevant activities came also from JAERI, Japan. For the IFMIF project these results and improvements are highly significant, because the experimental data strongly validate the predictions from the codes, greatly increasing confidence that the reference IFMIF design objectives are realistic and can be met largely with available technology.

Design Integration: In the task area "safety assessment" probabilistic risk assessment calculations were performed taking into account the entire IFMIF plant and its subsystems. Within the framework of the task "reliability, availability and maintainability"; the IFMIF team conceived and developed the accelerator system model (ASM), and used it to guide conceptual design choices and to establish a credible RAM model. Finally, within the task area "central control system" two instruments have been evaluated for the interface between the accelerator, target and test cell: An infrared camera device to measure the beam position and temperature distribution on the Li-target, and a multi-channel based neutron monitor for on-line measurements of the special neutron distribution inside the test cell.