The REWET-MARIA test facility was located in a laboratory of the Department of the Energy Technology in Lappeenranta University of Technology near the REWET facilities: it used the same ECC injection, data acquisition and other peripherical facilities. As the REWET- MARIA facility had been designed for investigating reflooding phenomena in the MARIA loop during the LOCA experiments, its test section was an exact copy of the test section in the MARIA loop.
In the facility, the fuel rod test bundle was simulated by a bundle of 19 electrically heated fuel rod simulators in a triangular grid. The central rod was unheated as in the MARIA experiments. The heated length and the lattice pitch of the rods were the same as in the MARIA loop, but the diameter of the simulator rods differed slightly from the diameter of the MARIA test rods (in MARIA loop 9.1 mm, in REWET-MARIA facility 8.5 mm). The simulated residual heat in the fuel rod simulators was generated by a heating coil packed in magnesium oxide inside a stainless steel cladding. The uniform power distribution and the smaller diameter of the fuel rod simulators were chosen to reduce the expenses.
The outer walls of the test section were covered by heating elements to warm up the downcomer before experiments. The test section was thermally isolated. The intact loop was simulated by a stainless steel pipe connecting the upper plenum and the downcomer. The broken loop contained stainless steel pipes from the upper plenum and from the downcomer connected through a condenser to a condensate tank.
| Heated length of fuel rod simulators | 100 cm |
| Outer diameter of fuel rod simulators | 8.5 mm |
| Axial power distribution of fuel rod simulators | uniform |
| Number of rods in bundle | 18 |
| Wall thickness of the fuel channel | 2 mm |
| Bundle geometry | hexagonal |
| Lattice pitch | 12.2 mm |
| ECC injection locations | upper plenum and/or downcomer |
| Heating power of fuel rod simulators | 0-38 kW |
| Linear heating power | 0-20 W/cm |
| ECC injection flow rate (cold level rise) | 0-15 cm/s |
| System pressure | 0.1-1.0 MPa |
| Max surface temperature o.f fuel rod simulators | 750 �C |
| ECC coolant temperature | 15-120 �C |
The main measurements in the experiments were the temperatures of rod cladding, coolant and downcomer walls. The thermocouples measuring the cladding temperatures had been brazed onto the surface of the simulator rods. The temperature of the coolant in the downcomer was measured at six different levels with one to three thermocouples at each level.
The water level was measured in the rod bundle, in the downcomer and along the test section using the pressure difference transtucers. System pressure, ECC coolant flow rates and the heating power of the fuel rod simulators were also measured.
The REWET-MARIA facility was disassembled at 1991. Totally 146 experiments were carried out.
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