Design of a compact high-power neutron source—The EURISOL converter target

Abstract

a b s t r a c tThe EURISOL project, a multi-lateral initiative supported by the EU, aims to develop a facility to achieve high yields of isotopes in radioactive beams and extend the variety of these isotopes towards more exotic types.The neutron source at the heart of the projected facility is designed to generate isotopes by fissioning uranium carbide (UC) targets arranged around a 4 MW neutron source. For reasons of efficiency, it is essential that the neutron source be as compact as possible, to avoid losing neutrons by absorption whilst maximising the escaping neutron flux, thus increasing the number of fissions in the UC targets. The resulting configuration presents a challenge in terms of absorbing heat deposition rates of up to 8 kW/cm 3 in the neutron source; it has led to the selection of liquid metal for the target material. The current paper presents the design of a compact high-power liquid-metal neutron source comprising a specially optimised beam window concept. The design is based on two-dimensional (2D) and three-dimensional (3D) computational fluid dynamics (CFD) numerical simulations for thermal hydraulics and hydraulic aspects, as well as finite-element method (FEM) for assessing thermomechanical stability. The resulting optimised design was validated by a dedicated hydraulic test under realistic flow conditions. A full-scale mock-up was built at the Paul Scherrer Institute (PSI) and was tested at the Institute of Physics of the University of Latvia (IPUL).

Structural-hydraulic test of the liquid metal EURISOL target mock-up

“…The magnitude of the base frequency is at least a factor of two below the calculated value, approximately 60 Hz, depending on assumptions [6]. It would therefore appear that the support afforded to the target by the test rig is not as stiff as expected.…”

“…This was expected as a prior dynamic analysis by Samec et al [6] pressure variations from a CFD analysis to a structural FEM model indicated that resonance in the vanes was likely to lead to high cycle fatigue at 200 Hz and failure after a few hours of operation due to a weakness in the design of the flow vanes. Thus any further increase of the flow rate and decrease of the operating pressure, in particular a prolonged operation under critical conditions, are likely to lead to a failure of the flow vanes and/or the welds that hold them.…”

“…The thermal-hydraulic and structural performance of the target concept was optimised at PSI [2] and experimental investigations described in this paper were used to validate computational results. Hydraulic calculations, including physical modelling of two-phase flow phenomena such as cavitation and free-surface flows, have been carried out by using the Computational Fluid Dynamic Code CFX 11.0 [6]. These calculations have been accompanied by structural calculations performed with ANSYS 11.0 [3].…”

CFD analysis and optimization of a liquid lead–bismuth loop target for ISOL facilities

“…Computational Fluid Dynamics (CFD) tools are commonly used for the thermal and hydraulic design of facilities operating with liquidmetal, e.g., MYRRHA [17], ESS [18] and EURISOL [8,19]. Furthermore, important aspects of CFD analysis such as the turbulence modeling, pressure field and pressure drop in a liquid-metal flow have been validated in the framework of thermal-hydraulics design of the MEGAPIE LBE target [8,19].…”

“…Concerns for the design of these targets include effects like pressure drop, cavitation, liquid-metal recirculation, instabilities, non-uniform flows etc. [7][8][9]. Studies conducted in the past by different researchers highlight the importance of these effects on the target system [10,11].…”