Available online at www.sciencedirect.com Nuclear Engineering and Design 238 (2008) 90–101 Numerical design of a 20 MW lead–bismuth spallation target with an injection tube Chungho Cho ∗ , Yonghee Kim, Tae Yung Song, Yong-Bum Lee Korea Atomic Energy Research Institute, P.O. Box 105, Yuseong, Daejeon 305-600, Republic of Korea Received 30 January 2007; received in revised form 19 June 2007; accepted 19 June 2007 Abstract A spallation target system is a key component to be developed for an accelerator driven system (ADS). It is known that a 15–25 MW spallation target is required for a practical 1000 MW th ADS. The design of a 20 MW spallation target is very challenging because more than 60% of the beam power is deposited as heat in a small volume of the target system. In the present work, a numerical design study was performed to obtain the optimal design parameters for a 20 MW spallation target for a 1000 MW th ADS. A dual injection tube was proposed for a reduction of the lead–bismuth eutectic (LBE) flow rate at the target channel. The results of the present study show that a 30 cm wide proton beam with a uniform beam distribution should be adopted for a spallation target of a 20MW power. When the dual LBE injection tube is employed, the LBE flow rate could be reduced by a factor of 7 without reducing the allowable beam current. © 2007 Elsevier B.V. All rights reserved. 1. Introduction In an accelerator driven system (ADS), a high-energy proton beam impinges on a heavy metal target to produce spallation neutrons that are multiplied in a sub-critical blanket. There- fore, the spallation target is one of the most important units of an ADS. A lead–bismuth eutectic (LBE) is preferred as the spallation target material due to its high neutron production rate, effective heat removal, low melting point and low vapor pressure, low neutron absorption and good radiation damage resistance. In addition, it can be used simultaneously as a reactor coolant. A key issue in the target design is how to design an appropri- ate beam window and an LBE target flow so that the system can sustain thermal and mechanical loads as well as radiation dam- age. Recently, there have been intensive studies on the design of the LBE spallation targets (Buono et al., 1998; Dury et al., 1999; Cheng and Slessarev, 2000; Gohar et al., 2001; Tak and Cheng, 2001). It is well-known that a proton beam power of 15–25 MW is required for a practical size (about 1000 MW th power) of an ADS (Gromov et al., 1998a; Kim et al., 2003). The design of a 20 MW spallation target is very challenging because more than ∗ Corresponding author. Tel.: +82 42 868 2914; fax: +82 42 868 2080. E-mail address: chcho@kaeri.re.kr (C. Cho). 60% of the beam power is deposited as heat on the window and a small volume of the target system. Therefore, many studies are especially focused on the cooling capability of the beam window (Buono et al., 1998; Cheng and Slessarev, 2000; Tak et al., 2001, 2005; Smith et al., 2003; Arul Prakash et al., 2006). They showed the importance of the beam window cooling for the design of a spallation target. Due to the difficulties of designing high power targets, Forschungszentrum Karlsruhe proposed a three-beam target sys- tem and a windowless target design is also considered in the MYRRHA project and the X-ADS design (Cheng and Knebel, 1999; Tichelen et al., 1999; ANSALDO, 2001). Although these proposals have several favourable characteristics for a high power target, it is known that they also have different design issues, compared with the conventional target system with a solid window. In a previous study, we designed a 20MW LBE target for HYPER (Cho et al., 2004). However, it was found that the LBE flow rate was too high, almost 10% of the total coolant flow rate, and also the average LBE temperature rise in the target was too low, compared to the LBE heat up in the core. These problems result in an increased pumping power of the coolant, a higher possibility of a thermal striping of the core upper structures, and a decrease of the thermal efficiency of the system. Thus, there is a great necessity to reduce the LBE flow rate in the target channel without hampering the target performance. 0029-5493/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nucengdes.2007.06.011