Within the ITER machine, activated corrosion products (ACPs) will be present in the various in-vessel and vacuum vessel coolant loops as well as in any coolant loops related to test modules, auxiliary heating or diagnostics equipment. The activation products will impact occupational exposure, routine effluents to the environment, and potential releases during accidents. This fact has made the ACP inventory evaluation an important task for ITER public and occupational safety. Thus modeling of ACPs for ITER operation is a necessary requirement providing control and prediction of ACPs during operation. Such modeling has been done so far using the so-called PACTITER code, which is a modification of the PACTOLE code used for light water reactors and is based on a finite element approach where the primary circuit is represented by an arrangement of several volumes in which transient mass balance equations are solved. In the framework of the model there are a finite number of such volumes which are connected to each other by additional mass exchange equations. Therefore, the code provides an approximate solution with the accuracy depending on the number of the control volumes. However the model is limited to solution by numerical methods which may restrict the accuracy of such calculations under complex ITER operation scenarios. In this work we show that the problem can be described in the framework of a continuity equation for laminar flow of water in the coolant circuit. The continuity equation is written in a form which accounts water filtering and precipitation of the ACPs along the cooling ring and can be solved by both analytical and numerical methods. Analytical solutions for the case of a simple ring describing ACPs accumulation in the ring and filters are presented and discussed.