Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Experimental and numerical studies on thermal-hydraulics of spallation targets

X. Cheng, C. Pettan, J.U. Knebel, T. Schulenberg, G. Heusener

Abstract

Transmutation of actinides and other high level nuclear waste offers the possibility of increasing the public acceptance for nuclear energy. In this aspect accelerator driven systems (ADS) are promised to play an important role [1, 2]. The target where neutrons are generated by a proton beam is one of the most important units of an ADS. To achieve high thermal-hydraulic performance, different target concepts have been proposed in the past. One of the most favorable concepts is the liquid-metal target. In a liquid metal target the beam window is exposed to a high radiation and thermal flux. The coolability of the beam window is considered as one of the most critical items in designing a spallation target. It has been agreed that detailed thermal-hydraulic R&D works are needed for designing liquid metal targets. To gather practical experience on a liquid metal target, two pilot liquid lead-bismuth targets of 1 MW are now under design or under construction. The first one was designed and fabricated at the Institute of Physics and Power Engineering in the framework of the ISTC 559 project. This target will be tested at the LANSCE accelerator of Los Alamos National Laboratory. The second target will be designed and fabricated in Western Europe and be tested at the SINQ accelerator at Paul Scherrer Institut. The Forschungszentrum Karlsruhe (FZK) is actively involved in both projects, especially in thermal-hydraulic design of both targets. A three steps strategy is being proposed for the research activities accompanying the target design, i.e.:

Numerical analysis with the aim to provide the first knowledge about the thermal-hydraulic behavior in a spallation target and to achieve a preliminary design of the target;
Model experiments to achieve basic information for the target design, to provide experimental data base for model development and code validation;
Prototypic experiments in Pb-Bi for the final design of a spallation target.

A comprehensive experimental and numerical research program is underway at FZK. Table 1 summarizes the research activities undertaken at FZK relating to the target thermal-hydraulics. At present, three different target systems are taken into consideration, i.e. two pilot targets and an ADS-target system that can be used in an ADS-demonstrator or in the ADS reactor of the three-beam concept [7]. Test facilities suitable for different fluids, e.g. water and Pb-Bi, have been set up or are being under construction. Computer codes of different purposes, e.g. 1-D system analysis or 3-D CFD codes, have been used for the overall layout of the target system and for the detailed assessment of local thermal-hydraulic phenomena. The results obtained up to now confirm the necessity of the model experiment and the suitability of the HYTAS test facility for studying the hydraulic behavior of spallation targets. Numerical simulation with both the 1-D system code and the CFD code has provided useful information for design of the targets. The experimental studies at both the HYTAS test facility and in KALLA will provide important test data for the final target design, for model improvement and for validation of computer codes. In the present paper, an overview is given about the research programme at FZK relating to the target thermalhydraulics. Main results obtained up to now are presented and discussed.

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key words: Fast Neutron Spectrum Systems, Nuclear Technology

Reference:: Proceedings of a Committee Meeting (TCM) on “Core Physics and Engineering Aspects of Emerging Nuclear Energy Systems for Energy Generation and Transmutation” held in Argonne, Illinois, U.S.A., 28 November - 1 December 2000; International Atomic Energy Agency, Vienna (Austria); IAEA-TECDOC--1356, pp:308-325