[en] A multifrequency ACPD system was assembled which can measure very small crack. Stress corrosion cracking test system with SSRT operating high temperature was installed. Stress corrosion cracking test of newly developed alloy 600 and existing alloy 600 was carried out in steam atmosphere of 400 deg C. No crack was observed in both materials within a test period of 2,000 hrs. Corrosion fatigue test system operating at high temperature was installed in which fatigue crack was measured by CDPD. Lead enhanced the SCC of the Alloy 600 in high temperature water, had a tendency to modify a cracking morphology from intergranular to transgranular. Pit initiation preferentially occurred at Ti-rich carbide. Resistance to pit initiation decreased with increasing temperature up to 300 deg C. Test loop for erosion corrosion was designed and fabricated. Thin layer activation technique was very effective in measuring erosion corrosion. Erosion corrosion of a part of secondary side pipe was evaluated by the Check Family Codes of EPRI. Calculated values of pipe thickness by Check Family Codes coincided with the pipe thickness measured by UT with an error of ± 20%. Literature review on turbine failure showed that failure usually occurred in low pressure turbine rotor disc and causes of failure are stress corrosion cracking and corrosion fatigue. (author). 12 refs., 20 tabs., 77 figs

[en] In this work is presented the obtained response for superficial analysis technique by X-ray photoelectron spectroscopy (XPS or ESCA), to determine the corrosion products formed during the copper exposure at environment without pollutants (clean air) at 50, 70 and 90 % of relative humidity at 35 Centigrade. One of the copper corrosion products most knew is Cu₂O. This oxide is formed instantly to be exposed the copper at air. However in function of the exposure time and the relative humidity at it is exposed, the Cu₂O oxide is transformed at Cu O and Cu(OH)₂ (Author)

[en] A new calibration procedure is proposed for the application of recoil implantation of radioactive heavy ions (energies between a few hundred keV and a few MeV) into the near surface of materials as part of a research programme on sub-micrometric wear or corrosion phenomena. The depth profile of implanted radioelements is performed by using ultra thin deposited films obtained by cathode sputtering under argon plasma. Two curves for ⁵⁶Co ion in nickel have been determined for implantation depths of 110 and 200 nm, respectively, and stress the feasibility and reproducibility of this method for such activated depths. The achieved surface loss detection sensitivities are about 1 and 2 nm respectively. The on line detection mode is performed directly on the sample of interest. A general description of the method is presented. A study of the reaction kinematics followed by a general treatment on the irradiation parameters to be adopted are also developed with the intention of using the ultra thin layer activation method (UTLA) to further applications in research and industry. (author)

[en] The high nickel austenitic alloys are generally considered to have good resistance to chloride stress corrosion cracking. In the standard boiling magnesium chloride solution tests, alloys with more than 40% nickel are immune. Nevertheless, more recent data show that cracking can occur in both Alloys 600 and 690 if the solution is acidified. In other low pH media, such as boric acid solution at 100 deg C, transgranular and intergranular cracking are observed in Alloy 600 in the presence of minor concentrations of sodium chloride (2g/I). In concentrated boric acid at higher temperatures (250 and 290 deg C), intergranular cracking also occurs, either when the chloride concentration is high, or at low chloride contents and high oxygen levels. The role of pH and a possible specific action of boric acid are discussed, together with the influence of electrochemical potential. (author)

[en] A key component of the Engineered Barrier System (EBS) being designed for containment of spent-fuel and high-level waste at the proposed geological respository at Yucca Mountain, Nevada is a two-layer canister. In this particular design, the inner barrier is made of a corrosion resistant material (CRM) such as Alloy 825, 625 or C-22, while the outer barrier is made of a corrosion-allowance material (CAM) such as A516 or Monel 400. At the present time, Alloy C-22 and A516 are favored. This publication addresses the development of models to account for corrosion of Alloy C-22 surfaces exposed directly to the Near Field Environmental (NFE), as well as to the exacerbated conditions in the CAM-CRM crevice

[en] The mechanisms of nodule initiation and growth on susceptible zirconium alloys both in- and ex-reactor remain unclear. Hypotheses citing local solute depletion generally can explain more experimental observations than, for example, those relying solely on electrochemical activity at second phase particles, or residual stress, or texture. Since the solutes that protect zirconium from rapid oxidation in high-temperature, high-pressure steam all have oxidation states other than IV, it seems likely that the incorporation of aliovalent oxides into the monoclinic zirconia lattice plays an important role. Corrosion experiments indicated that effective solutes are those forming aliovalent cations that can substitute for Zr(IV) and alter the defect structure without disrupting the matrix. Laboratory alloy optimization for a combination of immunity to nodular corrosion in steam and minimum uniform corrosion in water requires in-reactor confirmation. (author). 49 refs, 4 figs, 1 tab

[en] One of the fundamental discoveries involving radiation effects on the oxidation of Zircaloy in low-oxygen aqueous environments is the influence of thick oxide films. Zircaloy oxidation rates in low-oxygen (hydrogen-rich) coolants initially proceed at relatively low rates, often almost uninfluenced by radiation. Marked upturns in oxidation rate have signaled the onset of radiation effects, appearing to correlate with a threshold oxide thickness. The oxide thickness effects were first recognized in a series of experiments in the Engineering Test Reactor (ETR) and Advanced Test Reactor (ATR). Results of the test reactor experiments lead to formulation of the thick-film hypothesis: beyond a threshold oxide thickness, radiolysis of water that infiltrates oxide cracks and pores controls the oxidation rate; radiation creates microenvironments inside the oxide film, producing highly oxidizing conditions, that are no longer suppressed by the coolant-borne hydrogen. The threshold oxide thickness for the ATR/ETR test series was in the range of 10 to 13 μm. More recently, thick-film behavior has been observed on Zircaloy in several reactors with low-oxygen coolants, including pressure tubes in the Hanford N Reactor, Pickering Units 1 and 2, and the NPD reactor. Radiation enhancements of oxidation also have been reported on PWR fuel cladding in several reactors and on unfueled assembly components. Hydriding in the thick-film regime is also accelerated, which appears to present a dilemma, namely, how can oxidizing and hydriding conditions exist simultaneously within the oxide. A potential explanation is that the effective radiolysis reactions occur at or near the metal/oxide interface. Adsorption on oxide or metal surfaces facilitates separation of oxidizing and reducing species. This paper summarizes the early evidence for thick-film behavior, including oxidation and hydriding trends, updates confirmatory evidence from Zircaloy reactor and fuel assembly components, and highlights other observations from the test reactor series that have potential fundamental significance to explanations of radiation effects on Zircaloy. (author). 24 refs, 9 figs, 3 tabs

[en] The influence of the precipitate size on the corrosion resistance of Zircaloy 4 has been clearly evidenced. The growth kinetics of these second phase particles must be established in order to control the oxide layer growth. A study using TEM and SEM associated with image analysis has been performed in order to determine the shape of the size distribution and to deduce the characteristic parameters of the population. The second step consisted in a comparison of the experimental distributions with the theoretical one, calculated by Lifshitz, Slyozof, Wagner and Kahlweit for the Ostwald ripening mechanism. The parameters of the growth, giving the evolution with time and temperature have been experimentally determined. This is compared with the cumulative annealing parameter, generally used in Zirconium metallurgy to quantify the influence of thermal treatments. (author). 17 refs, 16 figs, 7 tabs

[en] The corrosion of a tube made up of 9Cr-1Mo, 2.25Cr-1Mo, and 2.25Cr-1Mo-Nb ferritic steels and containing artificial defects has been investigated under realistic steam generator conditions (355⁰C, 17.6 MPa) with acid chloride fault water chemistry (2 mg/kg HCl). Four regions of corrosion and magnetite deposition behaviour were observed on the tube surface. In non-heat flux regions, magnetite deposition was affected by mass transfer and probably also by surface potential. In low heat flux regions (<660 kW m^-2) observed increases in the rates of magnetite deposition and corrosion were probably due to rises in the degree of iron supersaturation and HCl concentration, brought about by boiling. Enhanced HCl concentrations in the normal heat flux region (660 kW m^-2) prevented magnetite deposition and caused an increase in corrosion of the three steels. Increases in corrosion and magnetite deposition were also observed at the weld between the 9Cr-1Mo and 2.25Cr-1Mo steels. In defects, accelerated corrosion was seen only in the 9Cr-1Mo steel and was confined to the top 0.15 mm. It is concluded that the corrosion behaviour observed in this work is determined by the residence time and concentration of solutions of HCl on tube and defect surfaces. (author)

[en] Problems is considered of development of the microbiological corrosion of the NPP equipment. The main attention is paid to the selective character of microbiological corrosion in zones of welded joints of austenitic steels. It is noted that the presence of technological defects promotes growth of corrosional damages. Methods for microbiological corrosion protection are discussed