Cesium deposition on the surface of the sodium coolant circulation loop

The authors measurements of the cesium activity in the circuit of the BOR-60 reactor have shown that the specific activity of 137Cs in the coolant decreases substantially when the reactor is shut down and increases when the reactor is started up. On the basis of these results, knowing the total surface of the first loop and the volume of the coolant and taking the temperature dependence into account, we determined the effective cesium distribution coefficient for the entire reactor. At 2200C this coefficient was 2.2 cm, i.e., virtually coincided with that obtained for the piping. In the shut-down BOR-60 reactor, therefore, ∼ 30% of the total amount of cesium in the primary loop (excluding the cold trap) may be located on the surfaces. When the temperature is raised part of the cesium moves from the deposits into the coolant