The experiments have shown that the noticeable hydrogen production due to the steam-zirconium reaction took place at the temperature about 650 °С. It was observed both visually as hydrogen bubbles in the accumulator and by record of the water level changes in the tank 9. In the teats with spiral heater where the temperature didn’t exceed 800 °С, it was marked also that the amount of hydrogen produced diminished with every consecutive turning on of the heater. It apparently may be explained by the

0 50 100 150 200 250 300 350

t, сек

Fig. 2. Change of the water volume in accumulator tank and simulator surface temperature vs. time.

— — TestN. l: —- TestN. 2.

influence of the zirconium oxide layer at the rod surface on the steam access to the clean ziconium surface and, finally on the hydrogen production. At the test with the rod simulator, however, at the temperature of 1000 °С there was a local break-off in oxide film. It may be resulted from both by the rod distorsion and by the hydrodynamic exerting of the steam-droplet mixture on its surface.

In Fig. 2 the results of two tests earned out at the identical initial conditions with the rod IIPE simulator are shown. The electric power in both tests was 1.5 kW. Fig.2 illustrates evidently the dynamics of the assembly dryout and the hydrogen discharge during steam-zirconium reaction. The curves V(i) and T(i) are correlated with each other qwite well. So, the signal from the level gauge being initially constant begins to increase with the begiiming of the steam-zirconium reaction. It’s the moment when the rod temperature reaches its maximum value. At the meam temperature of 1000 °С the amount of the hydrogen produced during 170 s was as much as 143 cm3 in the test No. 1 and 110 an3 in the test No.2. The considerable rod deformation over the length was marked.

In [3] the measuring of the amount of hydrogen produced in the steam-zirconium reaction was carried out at the temperature of 1000 °С. The measuring technique was in determination the mass increase of small zirconium specimens in steam atmosphere during the definite time and consecutive calculation the amount of hydrogen. The mean value of the hydrogen volume produced by 1 cm3 of the specimen surface per 1 s was about 0.0136 cm3. In our tests this value was as much as 0.0125 cm3. The agreement is quite satisfactory. It may be consider as a confirmation of the reliability of the dilatometric method used for the measuring the amount of hydrogen produced.

CONCLUSONS

Experimentally it has been shown that the dilatometric method of the amount of hydrogen produced during steam-zirconium reaction is a perspective one for carefull investigation of this reaction kynetics.

The visualization of the process of the one-rod assembly dry-out has been carried out.

REFERENCES

1. Kovalevitch О. M., Budaev M. A. The Problem of Hydrogen Production at APP Accidents. Afomnaja technikaza rubezhom, 1952, N. 12, c. 25.

2. Fujishiro, T. Hydrogen Generation during Cladding/Coolant Interactions under Reactivity Initiated Accident Conditions. Report Presented at the International Conference NURETH-4, Karlsruhe, 1992. p. 23.

3. Levin A. Ya., Izrailevsky L. B., Morozov A. M. Investigation of Interaction of Zirconium with Steam at 1000 °С. Thermohydraulic Processes on APP Facilities, Proceedings ofVTI, Moscow, Eneigoatomizdat, 1986.