Thermal-Hydraulic Integral Effect Test Facilities
R & D Facilities > Reactor Research


The ATLAS is a large-scale thermal-hydraulic integral effect test (IET) facility for evolutionary pressurized water reactors APR1400 and OPR1000. The ATLAS facility has the following characteristics: (a) 1/2-height&length, 1/288-volume, and a full pressure simulation of APR1400, (b) maintaining a geometrical similarity with APR1400 including 2(hot legs)×4(cold legs) reactor coolant loops, a direct vessel injection (DVI) for an emergency core cooling water, integrated annular downcomer, etc., (c) incorporation of specific design characteristics of OPR1000 such as cold leg injection and low-pressure safety injection pumps, (d) maximum 10% of a scaled nominal core power.

The ATLAS are mainly used to simulate various accident and transient scenarios for OPR1000 and APR1400, including the reflood phase of a large-break loss-of-coolant accident (LBLOCA), small-break LOCA (SBLOCA) scenarios including DVI line breaks, a steam generator tube rupture, a main steam line break, a feed line break, a mid-loop operation, etc. The data are used for validation of safety analysis codes and verification of new design features. A new International Standard Problem (ISP) exercise of the OECD/NEA CSNI, i.e., ISP No. 50, was recently launched with the ATLAS.

ATLAS: Advanced Thermal-Hydraulic Test Loop for Accident Simulation

Major components in the ATLAS facility
Major components in the ATLAS facility
Photograph of the ATLAS facility
Photograph of the ATLAS facility


The ATLAS facility consists of a primary system, a secondary system, a safety system, an auxiliary system, a power supply system, an instrumentation & control system, and a data acquisition system (DAS). The first floor of the ATLAS facility is at a ground level of 72.3 m. The total height of the facility is about 30m, i.e., 10m under ground and 20 m above ground. All the major components, e.g., reactor vessel (RV), SGs, pressurizer, SITs, are located above ground. The ATLAS facility adopts a jet condenser for a heat removal from the secondary system to the component cooling water system and containment simulators to simulate the containment back pressure and to measure a break flow.

Unlike most other IET loops, the ATLAS is designed to allow for the simulation of LBLOCA scenarios, at least for the reflood phase. This is primarily due to a need identified during the regulatory review for the standard design certification of the APR1400. Although the APR1400 has the characteristics of an enhanced safety, more information on the downcomer behavior and the transient interaction between the core and downcomer would be required for the late reflood phase of a LBLOCA after a depletion of the safety injection water from the safety injection tanks (SITs). Other transient and accident scenarios including SBLOCAs, DVI line breaks, main steam line breaks (MSLBs), etc., should also be simulated in the ATLAS.

Control room during ATLAS operation
Control room during ATLAS operation
  • Brief history

    Brief history
    Date Action
    Dec. 2003 Construction Start
    Jun. 2005 Steel Structure
    Dec. 2005 Installation Completion
    Dec. 2006 Commission Test Completion
    Jul. 2007 1st Open Test (LBLOCA Reflood Test)
    Nov. 2007 2nd IET International Workshop
    During 2008 DVI line break and SBLOCA Tests
    Apr. 2009 International Standard Problem (ISP-50) Kickoff

  • Overall test program of the ATLAS facility

    Overall test program of the ATLAS facility
    Stages Scenarios Objectives
    Start-up Tests Natural Circulation 3″ SBLOCA Identification of the RCS loop characteristics
    Comparison with analysis codes
    1st Stage
    LBLOCA Reflood Support for resolving the APR1400 safety issues
    Downcomer and core T/H behavior with DVI
    DVI Line Break Test data for unique design configuration
    Support for analysis code validation
    Data for domestic standard problem
    SBLOCAs Data for unique RCS configuration with DVI
    Validation for industry and regulatory analysis codes
    Data for international standard problem
    2nd Stage
    MSLBs Boron behavior for direct vessel injection of ECC water
    SGTRs Assessment of accident progress and code prediction capability
    FLBs Assessment of accident progress and code prediction capability
    Mid-Loop Operation Assessment of accident progress and code prediction capability
    3rd Stage
    Tests for beyond-DBA and accident management
    Tests requested by the regulatory body and/or industry
    International cooperative programs


    The VISTA facility is to investigate the overall thermal-hydraulic behavior of the SMART. It has the same height and 1/486 volume with respect to the SMART and is used to understand the thermal-hydraulic responses following transients and finally to verify the system design of the SMART. The reactor core is simulated by electrical heaters with a capacity of 819 kW. Unlike the integrated arrangements of the SMART, the primary components including a reactor vessel, a reactor coolant pump, a helical-coiled steam generator, and a pressurizer are connected by pipes with one another for an easy installation of the instrumentation and a simple maintenance. The secondary system with a single train is simply designed to remove the primary heat source. Besides these major systems a make-up water system and a chilled water system are installed to control the feedwater supply and its temperature. Some of the safety-related systems to simulate a piping break and a safety injection will be installed after carrying out performance tests such as the normal operation and operational transients as well as some of the accidents. The PRHR system of the VISTA facility is composed of a single train of the cooling sub-system, which includes an emergency cooldown tank (ECT), a heat exchanger (HX), a compensating tank (CT), several valves and related piping. It is connected to both the feedwater and steam lines of the secondary system to create a flow path with a natural circulation.

    VISTA: Experimental Verification by Integral Simulation of Transients and Accidents

    SMART: System-Integrated Modular Advanced Reactor

    Photograph of the VISTA facility
    Photograph of the VISTA facility
    Schematic diagram of the VISTA facility
    Schematic diagram of the VISTA facility