Flowing Pb Bi Research Articles

Long-term corrosion performance of T91 ferritic/martensitic steel at 400 °C in flowing Pb-Bi eutectic with 2 × 10−7 mass% dissolved oxygen

Long-term corrosion behavior of T91 ferritic/martensitic steel in oxygen-doped flowing Pb–Bi eutectic is investigated by exposure for up to 20,000 h at 400 °C, 2 m/s and 2 × 10−7mass% dissolved oxygen. The corrosion phenomena and kinetics of interaction are characterized qualitatively and quantitatively. The steel shows major oxidation resulted in the formation of a bilayer Fe3O4 / Fe(Fe,Cr)2O4 scale. After 20,000 h, the scale thickness averages 12.6 (±2.7) μm. The metal recession due to oxidation does not exceed 5 (±1) μm. Besides oxidation, the localized dissolution of the steel is observed reaching of ∼100 μm in depth after 20,000 h.

Corrosion Interaction of 9%Cr Ferritic/Martensitic Steels at 450 and 550 °C With Flowing Pb–Bi Eutectic Containing 10−7 Mass % Dissolved Oxygen

Corrosion behavior of 9%Cr F/M P92, E911, and EUROFER steels was investigated in flowing (2 m/s) Pb–Bi with 10−7 mass % O at 450 and 550 °C for up to 8766 and 2011 h, respectively. The steels show mixed corrosion modes simultaneously revealing protective scale formation, accelerated oxidation, and solution-based attack. At 450 °C, the accelerated oxidation resulted in a metal recession averaging 6 μm (± 2 μm) after ∼ 8766 h, while local solution-based corrosion attack ranged from ∼40 to 350 μm. At 550 °C, the accelerated oxidation resulted in a metal recession of about 10 μm (± 2 μm) after ∼ 2011 h. Solution-based corrosion attack appears more regularly at 550 °C, with a maximum depth ranged from ∼90 to 1000 μm. The incubation time for the solution based attack at 450 °C is 500–2000 h and < 300 h at 550 °C.

Effect of cold working on the corrosion resistance of JPCA stainless steel in flowing Pb–Bi at 450 °C

Development of a high performance proton beam window material is one of the critical issues for the deployment of the accelerator-driven transmutation system (ADS) with liquid Pb–Bi eutectic as a spallation target and coolant. In the present study, we applied 20% cold work treatment to JPCA austenitic stainless steel and investigated it from the corrosion behavior viewpoint. The corrosion test of 20% cold-worked JPCA SS has been carried in the JLBL-1 (JAEA Lead–Bismuth Loop-1) apparatus. The maximum temperature, the temperature difference, the flow velocity and the exposure time of the liquid Pb–Bi were 450°C, 100°C, 1m/s, and 1000h, respectively. For comparison analysis, JPCA SS without cold working was also tested in the same time and conditions with the 20% cold-worked JPCA SS. The results showed a different corrosion behavior between the JPCA SS without and with cold working. As for the JPCA SS without cold working, Pb–Bi penetrated into the matrix through a ferrite layer which was formed because of constituent metals dissolution from the matrix into Pb–Bi. As for the 20% cold-worked JPCA SS, dissolution attack occurred only partially and formed localized superficial pitting corrosion. It was found that the different corrosion behavior occurred because the cold working induced a structure transformation from γ-austenite to α′-martensite and affected the corrosion resistance of the JPCA SS in flowing Pb–Bi at 450°C.

Creep-to-rupture tests of T91 steel in flowing Pb–Bi eutectic melt at 550 °C

Uniaxial creep-to-rupture tests were performed on T91 in air and in flowing lead–bismuth eutectic melts. Compared to specimens tested in air, the specimens tested in liquid–metal show: (i) strain and strain rate increase up to a factor of about 50 (strain rate); (ii) time-to-rupture decrease; (iii) rapid transition into the third creep stage at high stress (above 180 MPa). The analysis of the test results revealed several important surface phenomena, which lead to different behavior of the specimens tested in lead–bismuth eutectic melts compared to those tested in air. Under high stress, and therefore high strain, the crack propagation process is mostly controlled by the reduction of the surface energy due to Pb and Bi adsorption on the steel surface. Under low stress (140 and 160 MPa) and low strain, this process is delayed due to the competing mechanism of healing the oxide scale cracks.

The effect of temperature and oxygen content on the flowing liquid metal corrosion of structural steels in the Pb–Bi eutectic

We performed corrosion tests of 1000 h each on approximately 20 types of structural steels (austenitic, ferritic and martensitic) in convection loops with flowing Pb–Bi at 500, 450 and 400 °C and a temperature gradient of 100 °C. These experiments were performed in liquid Pb–Bi with different oxygen concentrations (from approximately 1 × 10 −6 to 2 × 10 −5 wt.%) to ascertain at what oxygen concentration and up to what temperature the oxygen technology can create protective oxide or spinel layers to reduce or prevent corrosion. The results showed that the structural materials contemplated for building an ADS system, including 9% Cr–1% Mo (W) martensitic steels and similar steels with a higher Si content (2–3%), can be used with their surface unpassivated at up to 450 °C and suffer only minimal corrosion (up to 5 μm/year). At higher temperatures, their surface must be passivated prior to and regularly during the operation; however, no technology to perform such passivation in the presence of Pb–Bi is known that this time. In addition, we measured the impact of various alloying elements, such as Fe, Cr, Ni, Mn, Si, Al and Mo, on the corrosion of such steels and searched for potential ways to passivate their surface or create protective oxide or spinel layers during operation by varying the amount of oxygen in liquid Pb–Bi.

The impact of the composition of structural steels on their corrosion stability in liquid Pb–Bi at 500 and 400 °C with different oxygen concentrations

In recent years, heavy liquid metals have found exercise as possible coolants and targets in the conversion of radioactive elements in accelerator driven systems (ADS). Liquid lead–bismuth eutectic alloy is one of candidates for this using tanks to its suitable nuclear and physical properties. Performed examination was aimed at research of compatibility choice materials for parts of ADS with liquid Pb–Bi eutectic alloy, influence of composition choice materials on their corrosion resistance, influence of temperature and oxygen content. We performed corrosion tests of 1000 h each on approximately 20 types of structural steels (austenitic, ferritic and martensitic) in convection loops with flowing Pb–Bi at 500 and 400 °C and using different oxygen concentrations. The impact of Fe, Cr, Ni, Mn, Si, Al and Mo content on the corrosion stability of these steels was measured without and after preliminary passivation through creating thin spinel or oxide layers on their surface.

Corrosion–erosion test of SS316 in flowing Pb–Bi

Corrosion tests of austenitic stainless tube were done under flowing Pb–Bi conditions for 3000 h at 450 °C. Specimens were 316SS produced as a tubing form with 13.8 mm outer diameter, 2 mm thickness and 40 cm length. During operation, maximum temperature, temperature difference and flow velocity of Pb–Bi at the specimen were kept at 450, 50 °C, and 1 m/s, respectively. After the test, specimen and components of the loop were cut and examined by optical microscope, SEM, EDX, WDX and X-ray diffraction. Pb–Bi adhered on the surface of the specimen even after Pb–Bi was drained out to the storage tank from the circulating loop. Results differed from a stagnant corrosion test in that the specimen surface became rough and the corrosion rate was maximally 0.1 mm/3000 h. Mass transfer from the high temperature to the lower temperature area was observed: crystals of Fe–Cr were found on the tube surface in the low-temperature region. The sizes of crystals varied from 0.1 to 0.2 mm. The depositing crystals were ferrite grains and the chemical composition ratio (mass%) of Fe to Cr was 9:1.

Tensile testing of MANET II in flowing Pb–Bi alloy at elevated temperature

Experiments were carried out to study the influence of lead bismuth eutectic (LBE) on the tensile properties of the martensitic CrNiMoVNb steel named MANET II (Martensit for Next European Torus) considered as structural material for the first wall and blanket in fusion reactor conceptual design. In order to investigate a possible liquid metal embrittlement (LME) effect, tensile tests in flowing Pb–Bi at various temperatures (between 180 and 300 °C) were carried out. For comparison of the tensile test results achieved in Pb–Bi, tests were also carried out in the same facility but in an Ar atmosphere at the same temperature. After the tests, the fracture faces of the specimens were examined by SEM to analyse the fracture type (brittle or ductile). Additionally the ruptured specimens were longitudinally sectioned and analysed by metallurgical and SEM examinations.

Corrosion studies in liquid Pb–Bi alloy at JAERI: R & D program and first experimental results

The program of corrosion study in liquid Pb–Bi at Japan Atomic Energy Research Institute (JAERI) is described. It was planned to clarify effects of parameters such as temperature, temperature difference between high-temperature and low-temperature parts, oxygen concentration in liquid Pb–Bi, flow rate, irradiation, stress and chemical composition of materials. The program contains the basic corrosion study in static Pb–Bi for elucidation of corrosion mechanism and effects of oxygen concentration in liquid Pb–Bi and ion irradiation on corrosion behavior. It also contains the corrosion study in flowing Pb–Bi using a corrosion testing loop. From the initial result of the static corrosion tests in oxygen saturated Pb–Bi at 550 ° C for 500 h, it was shown that the thickness of the corrosion film decreases with increasing Cr content in steels.

Current status of JAERI spallation target material program

In the joint project of spallation neutron source between JAERI and KEK, material technology has been developed for the mercury target in the neutron source facility, the lead–bismuth target in the transmutation test facility, superconducting accelerator, post-irradiation examination and the ion beam test. Design of target system is progressing for the mercury spallation target: a pressure test of moderator, an impacting test in mercury and a corrosion test have been carried out. For nuclear transmutation with ADS an engineering facility is proposed. A material corrosion test loop is built-up and SS316 and F82H steels are to be tested in a flowing Pb–Bi. Fracture toughness of superconducting cavity material was found to be considerably large at 4 K. Irradiated samples at SINQ are to be transported to JAERI Hot Laboratory. For simulating radiation damage small disk specimens were irradiated in single, dual and triple ion beam modes.

Kinetics of gas phase oxygen control system (OCS) for stagnant and flowing Pb–Bi Systems

Pb and Pb–Bi are known to be very corrosive to structural materials at elevated temperatures. In recent studies, the necessity of measurement and control of the oxygen concentration in the liquid metal in order to safely operate a liquid Pb or Pb–Bi loop has been shown. The dynamic behaviour of the gas phase oxygen control system (OCS), which was developed at Forschungszentrum Karlsruhe (FZK), is investigated with respect to diffusion as the limiting process of oxygen exchange between the gas phase and the liquid metal. In this paper the development of a physical model for this diffusion process is described and compared to experimental results of a stagnant liquid Pb–Bi system. The experimental findings are in very good agreement with the theoretical equations describing the thermodynamic and kinetic behaviour of such a system. Recent investigations in a Pb–Bi loop at the Karlsruhe Lead Laboratory (KALLA) indicate that this gas phase OCS is a promising candidate system for an accelerator-driven subcritical system (ADS).

Corrosion behavior of steels in flowing lead–bismuth

Corrosion of steels in a flowing Pb–Bi environment has been studied. Specimens were exposed to the melt at 300°C and 470°C for up to 3116 h. The flow velocity was close to 2 m/s and the oxygen concentration in Pb–Bi was maintained at 1–2×10 −6 wt% . Independent of the specific steels (Optifer IV, T91 and EP823 martensitic steels, 1.4970 austenitic steel), no sign of dissolution was detected for either temperatures. In all cases, a protective oxide layer was formed on the steel surface. It was very thin (thickness ≪1 μm ) in the case of the 1.4970 austenitic steel, which presented the maximum resistance to oxidation in Pb–Bi–O. After 3116 h at 470°C, the thickness of the oxide layer (magnetite scale Fe 3O 4) formed on the martensitic steels ranged from about 10 to 20 μm. The oxidation resistance of the three martensitic steels decreases in the sequence: EP823, T91 and Optifer IV. The presence of silicon in the EP823 Russian steel (≈2 wt%) reduces the oxide layer growth. Results show that the present level of oxygen content in Pb–Bi is suitable for ensuring stable protection of steels against liquid metal corrosion at least for that period.