Condensation pool test facility used for the experiments of the second generation Nordic BWRs consists of the following main parts: a condensation pool, two pressure tanks, two blowdown pipes, an ECCS strainer, a pump with piping and a pressurized air injection system.
The pool is a cylinder shaped pool with open top made of stainless steel. The inner diameter of the pool is 2.4 m, the cross-sectional area 4.5 m² and the height 5.0 m. There are five circular windows in the pool wall for visual observation of the interior.
There are two pressure tanks (volumes 0.8 m³ and 0.6 m³). The tanks can be pressurized to an absolute pressure of 7.5 bar with the help of the pneumatic system.
From each of the pressure tanks goes a blowdown line towards the pool. The lines are connected to the upper ends of the vertical blowdown pipes above the pool. The pipes are made of stainless steel and placed inside the pool in a non-axisymmetric location. Two different diameter can be used, either DN150 or DN200. The inner diameters are 162.3 mm and 213.1 mm, respectively. The length of both pipes is approx. 4.0 m. The lower ends of the pipes are 1.0 m above the bottom of the pool.
Inside the pool is the ECCS strainer, which is made of stainless steel. The sides of the strainer are made of screen plate. The dimensions of the strainer are 1033x1000x443 mm.
The pump is placed outside the pool. The intake pipe is connected to the ECCS strainer. The pump sucks water through the strainer and pumps it back to the pool above the pool level.
Pressurized air can also be blown from the pneumatic system directly to the pump intake pipe, when the pump is sucking water through the strainer.
Measurement instrumentation includes temperature, pressure and flow rate measurements. During the experiments the events in the pool can also be recorded with several video cameras through the windows on the pool walls and below the pool level with an underwater camera.
For the experiments of the first generation
Nordic BWRs the facility was slightly modified. The test rig construction is equipped with four DN200 (Ø219.1x3.0) blowdown pipes. The pipes are submerged 1.0 m and the distance from the pipe outlets to the 0-level is 1.2 m. Horizontal locations of the pipes are axisymmetric. The pressurized air injection system was not in use. There are two pressure tanks (volumes 0.8 m³ and 1.1 m³). The tanks can be pressurized to a suitable pressure by using air compressors.
A cylinder shaped strainer is installed with the centerline in vertical direction. The diameter is 175 mm, the height 300 mm and the screen area 0.12 m2. The perforation is made of 3 mm diameter holes in a triangular pitch of 6 mm as in the plant conditions. The horizontal part of the intake pipe behind the strainer is made of transparent PMMA (Poly Methyl MathAcrylate). Flow through this pipe can be recorded by a video camera for visual observation of the void fraction. Pressurized air can also be blown from the pneumatic system directly to the pump intake pipe, when the pump is sucking water through the strainer.
For the POOLEX test facility was modified again. The pressure tanks, an ECCS strainer, and the pump were removed. Steam needed during the experiments is produced with the steam generators of the nearby PACTEL test facility. All three PACTEL steam generators are connected to each other on the secondary side via a common steam line. The maximum operating pressures on the primary and secondary sides of the PACTEL facility are 8.0 MPa and 4.6 MPa, respectively. The maximum electrical heating power of the PACTEL core simulator available for steam production is 1 MW.
Steam is led through a steam line towards the water pool. The line is made of standard DN80 and DN50 steel pipes. The line is thermally insulated with mineral wool to prevent steam from condensing before reaching the blowdown pipe. DN200 (inner diameter 214.1 mm), DN100 (inner diameter 110.3 mm) and DN80 (inner diameter 84.9 mm) stainless steel pipes are used separately as blowdown pipes in the preliminary experiments. Additional instrumentation includes strain gauges and valve position sensors.
For the STRA experiments an ECCS strainer and a pipeline returning the sucked water to the pool were added to the test rig. The strainer was located at the elevation of the blowdown pipe outlet so that the bottom of the strainer was, however, clearly below the pipe outlet elevation. The circulated water was returned to the level of the blowdown pipe outlet.
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