The TALL 3D installation for high quality experimental data

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SESAME Newsletter #2 (February 2017) 

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The TALL 3D installation for high quality experimental data

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Figure 1

Generation IV nuclear reactors should satisfy improved safety requirements, sustainability, efficiency, achieve better public acceptance and remain competitive. Among different Gen-IV concepts, one of the most promising is the Lead-cooled Fast Reactor (LFR) that uses compact pool-type designs and passive residual heat removal systems. Design and safety assessments of LFRs is contingent upon availability computationally efficient codes capable to accurately predict complex transient phenomena resulting from interplay between pool thermal dynamics and weak forces that drive natural circulation.  Comprehensive and successful verification and validation of a code is a prerequisite for its application in the design and safety analysis of a nuclear reactor.

The TALL-3D facility (Thermal-hydraulic ADS Lead-bismuth Loop with 3D flow test section) is a state-of-the-art experimental loop developed at KTH (Royal Institute of Technology, Stockholm, Sweden) as part of the EU THINS project. The primary goal of the facility is to provide high quality experimental data for calibration, benchmarking and validation of system thermal-hydraulic (STH), computational fluid dynamics (CFD) and coupled STH-CFD codes.

The installation is illustrated in Figure 1. It incorporates (i) the primary loop that operates LBE, (ii) the secondary loop used as an ultimate heat sink, (iii) instrumentation for the measurement of flow parameters in different locations, (iv) safety, service and control equipment. The primary loop has two heated sections at the bottom (Main heater and 3D test section heater), a permanent magnet pump, and a primary heat exchanger at the top that connects the primary loop to the secondary loop.

Total electric power of the facility is 80kW, including 27 kW pin-type Main Heater (MH) and 15 kW heater in the 3D test section. The maximum LBE flow velocity is 5 kg/s in forced circulation and about 0.6 kg in natural circulation. During transients near stagnant flow can be established. The maximum LBE temperature is 480 °C in the hot part of the loop and 350 °C in the cold part. The secondary loop can be operated at temperatures from 50 to 300 °C with coolant flow rates up to 1.2 kg/s. The hydrostatic pressure at the bottom of the primary loop is is 7.8 bar.

The facility can carry out tests in forced, natural and mixed circulation regimes and various transients of safety importance with transitions between different flow regimes (see Figure 2). Design of the facility (i) promotes two-way feedbacks between the local 3D flow phenomena (e.g. thermal stratification, mixing inside the 3D test section) and the dynamics of the loop system; (ii) provides a possibility to isolate sections of the facility with well-defined boundary conditions for separate effect studies; (iii) incorporates extended instrumentation and control equipment to establish a sufficient number of constraints and flow regimes for the separation of the calibration process in the uncertain model input parameters from the process of code validation.

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Figure 2:  Forced to natural circulation transient in TALL-3D (Left: LBE flow temperature – Right: LBE mass flow rate)

Three groups of tests TG01-03 have been defined for the first experimental campaign using the TALL-3D facility. The test group TG01 contains data for the quantification of measurement uncertainty, TG02 concerns model input calibration and TG03 consists of complex transients for the fine tuning of models, open and closed benchmark tests and validation experiments. Currently the first experimental campaign is being finalised by the research team and obtained data is being prepared for the dissemination between SESAME partners.