Use of gadolinium as a neutron absorber in nuclear reactors: radiolysis of gadolinium nitrate solutions

Radiolysis of gadolinium nitrate solutions was investigated in a GAMMACELL and in the WR-1 reactor. The results from the two were similar although the dose rate in the WR-1 reactor was about 200 times higher than in the GAMMACELL. The initial G(H2) values in the presence of various cover gases (N2, He, O2 and air) for the solutions and for water vapour are less than 1. The G(H2) values are lower for the solutions with lower initial pH. In the presence of nitrogen and air, the pH of the solutions decreases with absorbed dose. Formation of an unidentified gadolinium compound in the irradiated solutions is indicated. A precipitate is formed when gadolinium nitrate solution is irradiated in the presence of alumina. (author)