A review on clogging of recirculating steam generators in Pressurized-Water Reactors

International audienceCorrosion product deposits in the secondary side of nuclear power plant steam generators may result in Tube Support Plate (TSP) clogging and tube fouling. Magnetite has an inverse solubility above 150C, which favours iron precipitation when temperature increases. Flashing and electrokinetics are two strengthening processes for precipitation in TSP clogging. Surface chemistry of magnetite particles was discussed to understand its' interaction with TSP. Particle deposition by boiling was identified as the limiting process by performing numerical applications with nominal conditions. Guidelines drawn from this review for investigating specifically TSP clogging consist on conducting representative condition experiments and electrokinetics investigations

Comparison of mass transfer coefficient approach and Nernst−Planck formulation in the reactive transport modeling of Co, Ni, and Ag removal by mixed-bed ion-exchange resins

International audienceExperiments performed under chemical and flow conditions representative of pressurized water reactors (PWR) primary fluid purification by ion exchange resins (Amberlite IRN9882) are modeled with the OPTIPUR code, considering 1D reactive transport in the mixed-bed column with convective/dispersive transport between beads and electrodiffusive transport within the boundary film around the beads. The effectiveness of the purification in these dilute conditions is highly related to film mass transfer restrictions, which are accounted for by adjustment of a common mass transfer coefficient (MTC) on the experimental initial leakage or modeling of species diffusion through the bead film by the Nernst−Planck equation. A detailed analysis of the modeling against experimental data shows that the Nernst−Planck approach with no adjustable parameters performs as well as, or better than, the MTC approach, particularly to simulate the chromatographic elution of silver by nickel and the subsequent enrichment of the solution in the former metal

Influence of the dissolved hydrogen concentration on the radioactive contamination of the primary loops of DOEL-4 PWR using the OSCAR code

International audienceCorrosion products are generated in the primary circuit during normal operation and are activated in the core. Those activated corrosion products, mainly 58Co and 60Co (coming respectively from the activation of 58Ni and 59Co), are then transported by the primary fluid and deposited on the out-of-flux surfaces (steam generators, primary coolant pipes…). To minimize this radioactive contamination, one needs to understand the behavior of corrosion products by carrying out measurements in PWRs and test loops combined with a reactor contamination assessment code named OSCAR. The aim of this article is to evaluate the influence of the change in the Dissolved Hydrogen (DH) concentration on the contamination of the primary loops of DOEL-4 PWR, a Belgian unit. After the description of the principle of the OSCAR V1.3 code, its use is illustrated with the simulation of DOEL-4. Finally, those calculations are compared to autoclave experiments called DUPLEX with thermodynamic and chemical conditions closed to those observed in PWRs. OSCAR V1.3 calculations show that an increase in the DH concentration results in a decrease in 58Co surface activities. These results are consistent with those from the DUPLEX experiments. Finally, an increase of the DH concentration is then recommended in operating PWRs to reduce the 58Co surface contamination

Simulation of Co-60 uptake on stainless steel and alloy 690 using the OSCAR V1.4 code integrating an advanced dissolution-precipitation model

International audienceThe contamination of a nuclear cooling system by activated corrosion products (ACPs) is a process that involves many different mechanisms all interacting with each other. One of the most important mechanisms is dissolution-precipitation. This governs the transfer of soluble corrosion products between the circulating water and the immobile oxidized surfaces, and is strongly dependent on the water chemistry. The dissolution-precipitation model was improved in version 1.4 of the OSCAR computer code, which simulates the ACPs transfer in nuclear reactor systems. The OSCAR v1.4 code is now able to better calculate the incorporation of minor species (e.g., a cobalt isotope) into oxides using the chemistry module, PHREEQCEA, which determines the composition of an ideal solid solution and the equilibrium concentrations of elements in the aqueous solution. This model was challenged by comparing the results obtained using OSCAR v1.4 with the experimental results of a test performed in a dedicated loop by Studsvik Nuclear AB. Finally, with this model, the OSCAR v1.4 code accurately reproduces soluble $^{60}$Co uptake on stainless steel and alloy 690 under various experimental conditions (pH, Zn injection and flow rate)

Predicting ion exchange resins decontamination factors - Experiments on synthetic primary coolant containing Ni, Co and Ag and modeling results

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Comparison of Mass Transfer Coefficient Approach and Nernst–Planck Formulation in the Reactive Transport Modeling of Co, Ni, and Ag Removal by Mixed-Bed Ion-Exchange Resins

Experiments performed under chemical and flow conditions representative of pressurized water reactors (PWR) primary fluid purification by ion exchange resins (Amberlite IRN9882) are modeled with the OPTIPUR code, considering 1D reactive transport in the mixed-bed column with convective/dispersive transport between beads and electrodiffusive transport within the boundary film around the beads. The effectiveness of the purification in these dilute conditions is highly related to film mass transfer restrictions, which are accounted for by adjustment of a common mass transfer coefficient (MTC) on the experimental initial leakage or modeling of species diffusion through the bead film by the Nernst–Planck equation. A detailed analysis of the modeling against experimental data shows that the Nernst–Planck approach with no adjustable parameters performs as well as, or better than, the MTC approach, particularly to simulate the chromatographic elution of silver by nickel and the subsequent enrichment of the solution in the former metal

The OSCAR code: a simulation tool to assess the PWR contamination for decommissioning

International audienceKnowing the contamination state of the end-of-life nuclear reactor systems by Long-Lived RadioNu-clides (LLRNs) is a key stage for the decommissioning process. Indeed, the initial state is necessary to optimize the decommissioning works and to manage the radioactive waste as well. To address this issue, the contamination state is usually characterized using different types of techniques: in-situ gamma spectrometry, gamma camera scanning, dose rate measurements, , , measurements of samples obtained by smears or scrapings and then chemical separation processes, scaling factor approach… To reduce the amount of these measurements and thus the Occupational Radiation Ex-posure (ORE) and the decommissioning costs, a method is to assess the level of contamination by simulation. Furthermore, at the design stage of a new reactor, its decommissioning has to be taken into account and a simulation tool, such as the OSCAR code, can predict the radioactive source term at the end of life of a future reactor.The OSCAR code (Outil de Simulation de la ContAmination en Réacteur - tOol of Simulation of Con-tAmination in Reactor) has been developed by the CEA in collaboration with EDF and Framatome since the 1970s. The OSCAR code simulates the production and transfer of Activated Corrosion Products (ACPs) and Actinides and Fission Products and (AFPs) in the reactor systems and thus calculates the masses and activities of radionuclides deposited inside piping and heat exchangers of different circuits. As the OSCAR code has been originally devoted to mainly an industrial objective, which is the reduction of the Occupational Radiation Exposure (ORE) for operating PWRs, it deals with the main ACPs, 60Co, 58Co, 54Mn…, which are short-lived radionuclides. Nevertheless, it also cal-culates LLRNs of interest for decommissioning, such as 55Fe, 63Ni, 90Sr, 239Pu…, most of which are difficult to measure. The OSCAR code is validated through on-site measurements, including the EMECC campaigns, an operational experience feedback unique in the world, that consist of measur-ing the gamma surface activities mainly of the PWR primary system but also of auxiliary systems.After a presentation of the features and modeling of the OSCAR code, the paper will present some OSCAR simulation results of long-lived ACPs and AFPs deposited inside PWR circuits and their comparison with measurements. Perspectives of the OSCAR code on the decommissioning pro-grams will also be discussed