MATERIALS BEHAVIOUR IN SYSTEMS FOR TRANSMUTATION


General Data
  • Responsible : Dolores Gómez Briceño
  • Dedication of graduate personnel: 4,5
  • Costs: including direct, indirect and staff costs (k€): 812

Objetives
   The general objective of the project is to gain insight into the behaviour of the martensitic stainless steels, 9-12%Cr, considered as candidates for the construction of a spallation target for an accelerator-driven system (ADS) and/or as a structural material, under the operating conditions estimated in the conceptual design of this type of sub-critical reactors.
   On the one hand, the project aims at developing the technology required for the use of lead-bismuth as a coolant for a hybrid system, especially with regard to its compatibility with the structural materials. On the other hand, the project contemplates the study of the effect of irradiation on materials subjected to the spectrum expected for a spallation target, in order to support the design of a hybrid system and collaborate in drawing up a suitable database for prediction of system component integrity at the end of their lifetime.

Current Status
   The project on the Behaviour of Materials in Transmutation Systems was initiated in 1998, as part of the Power Plant Structural Materials Project. The scope of the project was defined bearing in mind the research to be carried out in this area by other European laboratories, such as CEA (France), FzK (Germany), ENEA (Italy), RIT (Sweden) and SCK-CEN (Belgium). Materials Behaviour in Systems for Transmutation
   The project is funded by the EU's 5th Framework Programme, within the framework of the TECLA and SPIRE projects. The TECLA project is dedicated to the study of corrosion in structural Pb-Bi materials and to the development of associated technologies, while the SPIRE project aims to study the effect of irradiation of candidate materials for use in the spallation target window. It is also financed by ENRESA and by the National R&D Plan.

Principal Results
   The use of the martensitic and austenitic steels in lead-bismuth at high temperature relies on the formation and prevention of protective oxide layers, which prevents the contact between the liquid metal and the structural material. Aluminised coatings are an alternative to the "in situ" protection by oxide layers.
   The corrosion resistance of lead-bismuth stainless steels at high temperatures depends on the activity of the oxygen in the medium and on the concentration of chromium in the materials. A study has been made of the behaviour of different martensitic and austenitic stainless steels,at temperature from 450 to 600ºC, in lead-bismuth molten with different oxygen activities in the molten metal. All the materials tested (with percentages of chrome ranging from 2.5 to 18) underwent a process of oxidisation in oxidant environments and a dissolution one in reductive environments. Alloys with higher chromium content show thinner oxide layers, more adherent and protective. In particular, high resistance corrosion has been observed for the 304 stainless steel at least in the tested conditions.
   The effect of temperature on oxidisation/corrosion of structural steels in molten lead-bismuth has been studied. Several series of tests have been performed in experimental devices allowing work to be carried out with partial oxygen pressures higher than the magnetite formation partial pressure and lower that the one need to lead oxide precipitation. The results point out the significance of this parameter to the viability of the "in situ protection" and the existence of an apparent threshold of temperature in which the change of oxidation to corrosion occurs. This threshold is a function of material and oxygen concentration.
   The activity of oxygen in the eutectic lead-bismuth is the key parameter to guarantee the use of structural steels in this medium, through protection by the "in-situ" formation of an oxide layer. The sensors used to measure oxygen activity are not commercial off-the-shelf elements, and their development is part of the scope of the TECLA project. Potentiometric sensors of In/In2O3 with stabilised zirconia are being developed and tested in collaboration with the Instituto Químico de Sarriá. Following a series of tests under static conditions, performed by IQS in its laboratories, work has continued at CIEMAT with testing in a natural convection circuit.
   During operation, the materials of the spallation target window in an ADS system will experience heavy irradiation damage, as well as a process of degradation due to corrosion in liquid metals. After a year of operation, the irradiation will cause alterations in the microstructure of the material, as a result of damage estimated at 100 dpa, and the formation of solid (P, S, Ca, others) and gaseous (H, He) impurities will occur. The EM 10 and T 91 steels have been selected for such use in the SPIRE project. As part of the CIEMAT contribution to this project, the mechanical and microstructural characterisation of both materials in the as-received condition has been carried out. During 2002, the microchemistry characterisation of grain boundaries by Auger spectroscopy has been done. In both materials, chromium and molybdenum enrichment in grain boundary as well phosphorus segregation have been found.

Scientific Investigators
  1. Diego Velasco, Gonzalo de
  2. Esteban Ochoa de Retana, Federico
  3. García Mazario, Marta
  4. Hernández Arroyo, Félix
  5. Hernández Mayoral, M. Mercedes
  6. Lancha Hernández, Ana María
  7. Lapeña Gutiérrez, Jesús
  8. Martín Muñoz, Francisco Javier.
  9. Perosanz López, Francisco J.
  10. Serrano García, Marta
References
(1). GÓMEZ BRICEÑO, D.; MARTÍN MUÑOZ, F.J.; SOLER CRESPO, L.; ESTEBAN, F.; TORRES, C. Behaviuor of F82H mod. stainless steel in lead-bismuth under temperature gradient. Journal of Nuclear Materials. 2001,vol. 296, p. 265-272.
(2). SOLER CRESPO, L.; MARTÍN MUÑOZ, F.J.; GÓMEZ BRICEÑO, D. Short term static corrosion tests in lead-bismuth. Journal of Nuclear Materials. 2001, vol. 296, p. 273-281.
(3). GARCÍA-MAZARIO, M.; HERNÁNDEZ- MAYORAL, M.; LANCHA, A.M. Auger electron spectroscopy study of alloy 718 and 304 L stainless steel irradiated with 800Mev protons. Journal of Nuclear Materials. 2001, vol, 296, p.192-202.
(4). GÓMEZ BRICEÑO, D.; MARTÍN MUÑOZ, F.J.; SOLER CRESPO, L.; ESTEBAN, F. Stainless steel corrosion in lead-bismuth under temperature gradient, Actinide and Fission Product Partitioning and Transmutation. In 6th OECD/NEA Information Exchange Meeting, ISBN 92-64-18466-X.
(5). GÓMEZ BRICEÑO, D.; SOLER CRESPO, L.; MARTÍN MUÑOZ, F.J. Basic corrosion studies in stagnant liquid lead alloys. Intermediate Report, Deliverable 1, TECLA Project, Octubre 2001.


( CIEMAT - september 2003 )