SCRAM facility

The test facility consisted of a scram tank, a blowdown tank, electric heaters, piping, valves, and measurement instrumentation. The main interest focuseed on the scram tank.

The scram tank was designed on the basis of the SWR-1000 concept. The height and and the inner diameter of the tank were reduced roughly on a scale of 1:6.5. The design pressure of the tank was 100 bar.

There was a "skirt" inside the vessel in order to mitigate the strong temperature gradients at the wall during the blowdown. In the second version of the facility (SCRAM-2001) the skirt consisted of a larger and two smaller cylinders. This arrangement allowed an annular water volume between the larger skirt and the tank wall. The fluid from the internal volume could flow through two identical holes which were drilled symmetrically on the smaller cylinders.

Four pipelines were attached to the scram tank. The depressurization line, where the safety valve was located in, connected the top of the tank to the atmosphere. The bypass line over the safety valve enabled manual depressurization. The draining line was attached to the bottom of the skirt volume. Two blowdown lines connected the scram tank to the blowdown tank. The feedwater line was connected to the blowdown lines.

By design, the top of the scram tank was insulated with mineral wool. The insulation was not used in experiments with reduced initial pressure.

The blowdown tank was basically a buffer tank for the water drained from the scram tank during the blowdown. The accumulator II of the PACTEL facility was used as a blowdown tank.

Three pipelines were attached to the blowdown tank. The blowdown line penetrated the lower flange of the tank. The depressurization line, where the safety valve was located, connected the top of the tank to the atmosphere. The draining line was located in the bottom of the tank. In addition to the lines, one manual valve was installed on the top of the tank. It enabled setting atmospheric pressure in the tank.

The blowdown lines had two separate lines. Both of the lines had a valve and an exchangeable orifice flange, allowing the use of various orifice diameters. The larger line was used for control rod injection phase and the smaller line for leakage into the reactor vessel. Both blowdown lines had an exchangeable orifice flange with two orifice size options. The orifice entrances were bevelled.

The scram system had two operating alternatives, two-tank scram and one-tank scram. The small orifices corresponded to the two-tank operation, where the scram was performed by two scram tanks. The large orifices corresponded to the single-tank operation, where the scram was performed by one scram tank only.

The heater consisted of assembled electric heater rods. The total heating power was 30 kW and reduced heating power was 5 kW. The instrumentation consisted of temperature measurements, two differential pressure measurements and two absolute pressure measurements. Temperatures were measured by 28 thermocouples.