Commissioning of CIRCE Facility for SGTR Experimental Investigation for HLMRs and Pre-Test Analysis by SIMMER-IV Code

In the framework of the European Commission MAXSIMA project, a large-scale test section, aiming to experimentally investigate the Steam Generator Tube Rupture (SGTR) postulated event, in a relevant configuration for Gen IV MYRRHA reactor, was implemented in the large pool CIRCE facility at ENEA CR Brasimone. The test section is mainly composed by four tube bundles of 31 tubes. Each one of which constitutes a full scale portion of the tube bundle of the Primary Heat eXchanger (PHX) of MYRRHA plant. The bundles are set in 6 inch tubes with a lower and upper tube plate, absolving structural tasks. Water flows upwards in the central tube at 200°C, 16 bar and about 0.1 kg/s, the first rank of six tubes is pressurized at 16 bar by argon for feedbacks on possible domino effect and the outer ranks are composed by opened tubes at the lower and upper end. Lead Bismuth Eutectic alloy (LBE), at 350°C under a cover gas of argon at about 1 bar, flows downwards shell side of the bundle, pushed by a pumping system composed by centrifugal and jet pumps connected in series, for reaching about 80 kg/s. Water tube is fed by external tank and supply line. Two regulation valves and one isolation valve are set for water pressure and mass flow rate regulation and interruption, respectively. Reached the water and LBE stationary conditions of MYRRHA PHX, in terms of pressure, temperature and mass flow rate, the central water tube is pulled upwards by an external hydraulic jack, realizing the tube rupture. Its position is well defined on the tube by a notch worked with machine tools. Four SGTR tests are foreseen to be carried out, one at a time, in the four tube bundles, excluding the necessity to extract the test section from CIRCE main vessel after each test. This paper presents the overall components implemented for carrying out the tests. In particular, the assembling of the whole test section, gas line for pressurizing the water tank and supply line and depressurization line of CIRCE cover gas. It discharges into a 1500 L tank, for collecting possible discharged LBE particulate. The Data acquisition and Control System (DACS) is realized in LabVIEW environment. It allows the remote control of the facility during the preparation phases, tests execution and safe shutdown. PID controllers are implemented for water heating and pressurization and water and LBE mass flow rate regulation. The main commissioning tests carried out and acquired variables by DACS, aiming to check the suitable functioning of all components, are presented. The pre-test numerical analysis of the SGTR experiments in CIRCE facility is performed by 3D Cartesian SIMMER-IV code. The obtained results show that the developed model is able to reach the initial condition of the tests in agreement with MYRRHA stationary conditions. Once reached, the water injection into LBE pool was numerically simulated. The pressure in CIRCE cover gas increased up to the opening rupture disk value of 6 bar in about 10 s, providing a grace period more than enough for carrying out the tests (3 or 5 s) in safe conditions.