CST20 The 25 th Conference of the Mechanical Engineering Network of Thailand October 19 – 21, 2011, Krabi Design of New Facility for Bypass Flow Experiment Worasit Kanjanakijkasem 1,* , Elvis Dominguez-Ontiveros 2 and Yassin A. Hassan 2 1 Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, United States 2 Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843, United States * Corresponding Author: marveric111@yahoo.com, marveric111@neo.tamu.edu Mobile (US): +1 979 204 7193, Mobile (Thai): 081 343 1796 (SMS Only) Abstract Bypass flow in prismatic core of very high temperature gas-cooled reactor (VHTR) is an important feature in the reactor core design of Generation IV reactor. Although many researchers have investigated about flows in VHTR for a long time, details of thermal/hydraulic characteristics of flows in this reactor core type still are not fully understood. As starting of bypass flow project, old facility was designed to assess the methods of flow measurement including PIV technique to enhance the understanding about bypass flow. In preliminary study, basic characteristics of air flow in the model of prismatic core of VHTR were studied experimentally and numerically based on old facility. All results were matched successfully but flow similarities between experiment and actual operation of reactor core could not be attained. In the first step of new facility design, the concept of multiple-path flow is employed by matching pressure drop of each flow passage. Because the results of this design show some unfavorable features, another concept starting from specifying mass flow rate based on flow area ratio is applied and examined by numerical simulations. The compromised design of new facility is met after performing few simulations. Keywords: Bypass Flow, Prismatic Core, VHTR, Generation IV Reactor. 1. Introduction The Generation IV Forum (GIF) was initiated in 2000 and formally chartered in July 2001. Late of 2002, GIF announced the selection of six reactor technologies which were believed to represent the future shape of nuclear energy. These reactor types were selected on the basis of being clean, safe and cost-effective, resistant to diversion of materials for weapons proliferation and secure from terrorist attacks [1]. The Generation IV systems are expected to become available for commercial introduction in the period between 2015 and 2030 or beyond [2]. The evolution of nuclear systems is shown in Fig. 1. Six reactor technologies selected by GIF are gas-cooled fast reactor (GFR), lead-cooled fast reactor (LFR), molten salt reactor (MSR), sodium-cooled fast reactor (SFR), supercritical water-cooled reactor (SCWR), and very high- temperature gas-cooled reactor (VHTR).