Analysis of corrosion product transport in PWR primary system under non-convective condition

Abstract

The increase of occupational radiation exposure (ORE) due to the increase of the operational period at existing nuclear power plant and also the publication of the new version of ICRP recommendation (ICRP publication No. 60) for radiological protection require much more strict reduction of radiation buildup in the nuclear power plant. The major sources of the radiation, i.e. the radioactive corrosion-products, are generated by the neutron activation of the corrosion products at the reactor core, and then the radioactive corrosion products are transported to the outside of the core, and accumulated near the steam generator side at PWR. Major radioactive corrosion-products of interest in PWR are $Cr^{51},\; Mn^{54},\; Co^{58},\; Fe^{59}$ and $Co^{60}$. Among them $Co^{58}$ and $Co^{60}$ are known to contribute approximately more than 70\% of the total ORE. Thus our main concerns are focused on predicting the transport and deposition of the Co radionuclides and suggesting the optimizing method which can minimize and control the ORE of the nuclear power plant. It is well known that Co-source is most effectively controlled by pH-solubility radiation control, and also some complex computer codes such as CORA and PACTOLE have been developed and revised to predict the corrosion product behavior. However these codes still imply some intrisic problems in simulating the real behavior of corrosion products in the reactor because of 1) the lack of important experimental data, coefficients and parameters of the transport and reactions under actual high temperature and pressure conditions, 2) no general theoretical modelling which can describe such many different mechanisms involved in the corrosion product movements, 3) the newly developed and measured behavior of the corrosion product transport mechanism. Since no sufficient and detailed information is available from the above-mentioned codes (also due to propriority problems), we concentrate on developing a new computer co...