Crud Behaviors in High-Temperature Water, (I): Characterization of Water in JMTR OWL-1 Loop

The characteristic of corrosion products (crud) in the OWL-1 loop water was first examined, in order to study the deposition behavior of crud on material surfaces. Under the steady operation of the loop, the concentration of the crud, passing through a 0.45 pm millipore-filter (crud-F), was 20-30 μg/l and that, being filtered (crud-P), was below 1 μg/l. Both cruds consisted mainly of Fe, with other minor elements, such as Cr, Ni, Mn and CO. The X-ray diffraction analysis of crud-P revealed that M 2 O 3 -type compounds constituted around 22% of the total crystalline compounds. The specific activity of 60 Co differed between crud-P and -F; the value in the former was larger than that in the latter by an order of magnitude, indicating no occurrence of rapid isotopic exchange of Co between two kinds of cruds. However, the ratio of the amounts of nuclides in crud-P and -F seems to be similar between 58 Co and 60 Co and between 54 Mn and 56 Mn. These results have been ascribed not to an isotopic mixing but to the chemical similarity between Ni and Co and between Fe and Mn (all are precursors of 58 Co, 60 Co, 54 Mn and 56 Mn).