EXPERIMENTAL FACILITY

The experimental facility is presented schematically in Fig. 1. Its basic elementa are the next:

• heating element: spiral or with internal heater 1:

• assembly body made from the transparent quartz-glass tube for assembly dre-out process visualization 2;

• bars 3;

• flange 4

• thermocouples J;

• refrigerator 6;

• calibrated measuring glass for hydrogen accumulation 7;

• level gauge (volume) in 8:

• expansion tank for collection of water replaced by steam and hydrogen 9;

• water-provided tank 10.

The collection and treatment of the information is fullfilled by the computer — controlled system. ‘

During the process of the model dry-out a steam-water mixture is directed to the refrigerator where it is condenced, while hydrogen is led to the accumulator. Hydrogen replaces water to the calibrated replacing tank. The pressure difference gauge registers the change of water level in replacing tank vs. time what enables to identify the moment of the steam-zirconium reacton beginning and to measure the amount og the hydrogen produced. The thermocouples are used for measuring the temperatures of the simulator surface and that of steam. For the simulator to be vacuumed and and after that filled with argon serves a special system.

EXPERIMENTS

In the experiments carried out two types of heater were used: one of spiral type and another — as a rod with internal heating.

The spiral type heater was fabricated of stainless steel capillary tube 4 mm in diameter. Inside this heater a small 60 x 5 mm plate zirconium was arranged. The chromel-alumel thermocouple was aranged at the plate centre.

The rod (HPE simulator) was made of the zirconium tube 09.3 x 0.5 mm. It was heated by molybdenum-made electric heater arranged inside which was insulated from the rod wall by pressed magnesium oxide. The total length of the simulator was 550 mm and that of the heated zone was 300 mm. The AC voltage was supplied to the simulator shell ahd heater from the transfomer. The internal part of the simulator was filled with argon.

The technique of the experiments carrying out was as follows. After the facility being filled with distilled deairated water one turned on simultaneously the simulator heating and the system recording in time the temperatures of the simulator surfase and exitingd steam and water level in accumulation tank. Once the electric powder was turned on, the simulator surface reached the saturation temperature and the boiling took place. The beginning of boiling was accompanied by intensive dry-out of the model and consecutive increasing of the rod surface temperature. The front of temperature increase was spread down the rod following the water level in assembly. The experiment was finished when the volume gauge signal reached its extreme value.