Progress Report on Target Development

The present document is the D08 deliverable report of work package 1 (Target Development) from the MEGAPIE TEST project of the 5th European Framework Program. Deliverable D08 is the progress report on the activities performed within WP 1. The due date of this deliverable was the 5th month after the start of the EU project. This coincided with a technical status meeting of the MEGAPIE Initiative, that was held in March 2002 in Bologna (Italy). The content of the present document reflects the status of the MEGAPIE target development at that stage. It gives an overview of the Target Design, the related Design Support activities and the progress of the work done for the safety assessment and licensing of the target

Electrochemical oxygen sensors for on-line monitoring in lead–bismuth alloys: status of development

International audienceThis paper presents the state of development of oxygen sensors based on the electromotive force (emf) measurement at null current, using yttria stabilized zirconia as solid electrolyte for application in liquid lead-bismuth eutectic (LBE), which is envisaged as a nuclear coolant or as a spallation target in accelerator driven system (ADS) for nuclear waste transmutation. The assembly procedure, the calibration method, as well as the summary of the various validation tests undergone in both static and loop facilities are presented so as to define a real state of achievement and the basics needs for further studies. The sensors are efficient, accurate, rapid and reliable for research loops. However, the poor mechanical resistance as well as the effect of traces of impurities, promoting an increasing time-drift under certain conditions, are to be further studied to improve the sensor reliability for a nuclear use. The oxygen and chromium solubilities were reassessed in the process of the sensor testing, those relations are also given and discussed

Chemistry control analysis of lead alloys systems to be used as nuclear coolant or spallation target

International audienceThis study presents the lead alloy system chemistry analysis for use as nuclear coolant orspallation target in ADS related systems in order to set down the needs for purificationprocesses and monitoring. The study is limited here to the 2 main impurities, oxygen and iron.The analysis of the various potential pollution sources that may occur during the variousoperating modes is given, as well as a first pollution rate assessment. In order to limit theconsequences in term of contamination (clogging) and corrosion, it is necessary to definespecifications for operation as regards oxygen and iron content in the fluid. As iron cannot bemeasured and controlled up to now, the best specification is to set the oxygen as high aspossible, defined by the cold leg interface temperature to ensure tolerable contamination, inorder to maximize the oxidation area to ensure corrosion protection by self-healing oxidelayer for the entire system

Corrosion of structural materials by liquid metals used fusion, fission and spallation

International audienceLiquid metals (lithium, sodium, lead and its liquid alloys Pb-Li or Pb-Bi) are used as coolants for fusion, fission or spallation reactors due to their thermal and nuclear properties. However, these liquid metals are corrosive when they come into contact with solid metallic materials. Preserving structural alloys (no- and low alloyed steels, stainless steels, nickel based alloys) in contact with these liquid metals requires the knowledge of the corrosion phenomena that may occur mainly liquid metal embrittlement and general corrosion with mass transfer. Liquid metal embrittlement is a particularly case of stress corrosion cracking in liquid metals which results in a decrease of the toughness or the ductility of the structural materials. It is also known as liquid metal cracking. Under specific combination of liquid metals, stressed solid metals or alloys and temperatures, an intergranular cracking of the solid alloys is sometimes observed. If wetting is a key factor, temperature, stress and strain rates, solid and liquid metal compositions are also influencing factors. Some results are shown with susceptible couples like ferritic/martensic steels in liquid lead (or its eutectics Pb-Li or Pb-Bi), and with also non susceptible couples like austenitic stainless steels in liquid sodium.General corrosion mechanisms in liquid metals is governed by thermodynamics and may be divided into two main phenomena et61485;Reaction with impurities dissolved oxygen in the liquid metal leads to oxidation of the solid metal when the reaction is thermodynamically possible and may lead to some protective oxide layers. If the activities of carbon (and other soluble elements like nitrogen) in the liquid and in the solid metals are different, carburation or de-carburation of the solid metals may occur, mainly at high temperature (above 600DC) as these phenomena are linked to the diffusion properties.et61485;Dissolution of the solid metal into the liquid metal may occur also and it is the main general corrosion phenomena when oxidation is not possible. The dissolution of alloying elements is function of their solubility in the liquid metal as nickel is very soluble in liquid lithium, liquid sodium or liquid lead, nickel alloys are not suitable for these environments where temperature and flow rates are also important parameters. The alloys containing some nickel, like austenitic stainless steels, will undergo ferritization of the dissolution zone due to the loss of nickel which is an austenite stabilizer. These phenomena show that the chemistry of the liquid metal is a key parameter for general corrosion of structural materials. As the solubility is generally decreasing with temperature, mass transfer may play also an important role in non-isothermal systems with dissolution process in the hottest section and precipitation in the coldest part of the circuits.If sodium does corrode, these phenomena are considered today under control for austenitic steels. For liquid lead and its liquid alloys, corrosion of steels, including liquid metal embrittlement, are important issues which need mitigation strategies including coatings or the development of specific alloys (steels forming a self-healing protective alumina layer) for instance

HfO2-based electrolyte potentiometric oxygen sensors for liquid sodium

International audienc

Oxygen control in lead-bismuth eutectic: First validation of electrochemical oxygen sensors in static conditions

The control of the impurities, and of oxygen in particular, is of major interest for ensuring adequate and safe operation of lead alloys facilities from the viewpoint of the corrosion phenomenon : spallation targets or coolants for hybrid or fast reactors, currently under studies within the transmutation topic of the 1991 law on nuclear waste disposal. In addition, because of the very low oxygen solubility in lead alloys, it is compulsory to avoid saturation in any part of a defined system and in any operating condition so as to avoid any plugging by lead oxide built-up (fuel assembly feet, ...). For the oxygen control, the on-line monitoring of the dissolved oxygen content is required. Electrochemical sensors built with yttria stabilized zirconia were developed and tested in various static facilities : BIP, JACOMEX glove box, COLIMESTA. The experimental results were compared to the theoretical formulation, and a calibration method was applied (search for the singular point defining the saturation temperature). The operating range is as follows: 280°C-550°C, $10^{-10}$ - 10 ppm (1 ppm = l0$^{-4}$ weight%), for a 40% estimated accuracy. Service life is more than 1000 hours up to now. Reproducibility, time drift, time to response, and mechanical resistance are satisfactory. Based upon these results a first validation of these oxygen sensors is obtained in static conditions

Corrosion of 316L(N) austenitic steel in sodium containing dissolved oxygen

International audienc

Steel Detritiation by Melting with Gas Bubbling

International audienc

Alternative dissolution and oxidation behavior of 316LN steel at 550°C in liquid sodium containing low concentration of oxygen

International audienc