Unirradiation and y-ray irradiation tests were carried out by using the selected two aqueous molybdate solutions (aqueous (NH4)6Mo7O24^4H2O and K2MoO4 solutions), and compatibility between the two solutions and the structural materials of stainless steel and aluminum, the chemical stability, the circulation characteristics, the radiolysis and the у heating of the two solutions were investigated. In addition, the integrity of PZC was investigated under y-ray irradiation. As a result, the following were found:

1. The compatibility between the two static aqueous molybdate solutions and stainless steel is very well under unirradiation and y-ray irradiation.

2. The two solutions are chemically stable and have smooth circulation under unirradiation and y-ray irradiation.

3. The ratios of hydrogen in the gases generated by the radiolysis of the two solutions are higher than that of pure water.

4. The effect of у heating on the two solutions is the same level as that on pure water.

5. The integrity of PZC is maintained under y-ray irradiation.

However, the pH of the aqueous (NH4)6Mo7O24 4H2O solution needs to be adjusted from weak alkaline to weak acid for the prevention of precipitation. This is a disadvantage as one of the candidates for the irradiation target.

At present, the aqueous K2MoO4 solution, which has no pH adjustment and has higher molybdenum content than that of the aqueous (NH4)6Mo7O24^ 4H2O solution, is investigated as the first candidate of the irradiation target.