[en] Electrochemical polarization measurements were conducted on Alloy 600 to screen the corrosive effects of certain PWR secondary water contaminants. These contaminants originate from resin polishing beds, condenser leakage, makeup water, and intentional additions. All additions to AVT water increased the anodic currents, but none produced any evidence of intergranular attack as determined by microscopic examination of metallographic sections after anodic polarization. Current increases were not proportional to potential changes and consequently could not be ascribed to increases in solution conductivity. Carboxylates, fluoride and bisulfate showed uniform attack. Additions of the Zn⁺⁺ cation did not cause any significant increase in anodic current over that of the accompanying acetate anion or produce any localized corrosion. Sulfate and benzosulfonate were found to cause irregular attack after anodic polarization which was changed to uniform attack in the presence of borate inhibitor. However, the anodic currents were not appreciably reduced in the presence of borate, and a strong inhibiting effect was therefore not indicated. This does not preclude the possibility of inhibition of carbon steel in tubesheet crevices with alkaline solutions. 9 refs., 15 figs., 2 tabs

[en] The corrosion performance of type 1016 (UNS G10160) low-carbon steel (LCS) was evaluated by direct current (DC) polarization techniques in waters with concentrated solutes expected in the vadose waters of the proposed Yucca Mountain (YM) geologic nuclear waste storage repository. Solute concentration simulated the expected effects of boiling and evaporation in the vadose waters surrounding the YM waste packages. LCS, a candidate material for the outer layer in current multibarrier waste-package designs, corroded at low general rates with no localized corrosion in deaerated waters at 25 C concentrated to 10 times (X), 100X, and 1,000X the reference water-well concentrations. Higher water temperatures (up to 90 C) and concentrations (100X and 1,000X) favored precipitation of silicate surface layers that further decreased corrosion rates and significantly increased apparent pitting potentials in deaerated water. Aeration increased corrosion rates significantly in 10X water at 25 C, but had lesser effects at 100X and 1,000X. Aeration and chloride additions also significantly degraded the protectiveness of inhibitive precipitate surface films. Added soluble Fe³⁺ in aerated 10X waters increased general corrosion at 25 C and initiated pitting at still higher concentrations and temperatures

[en] Objectives of the workshop were to define limits of water chemistry impurities for various support materials exposed to secondary water for a 40-year lifetime; to review factors affecting corrosion, hideout and return of salts in steam generator crevices; and to discuss additional candidate alloys and tests that would further define and optimize support design to minimize corrosion. The subject areas included: crevice corrosion rates of alloy steels compared to carbon steel; results from examination of support plate segments removed from steam generators; and review of models for corrosion and salt hideout in crevices. The data are intended to provide a basis for utilities to determine their particular design and material needs for steam generator support structures

[en] This report presents the results of a literature review on galvanic corrosion between candidate metals and alloys currently being considered for the waste package containers

[en] Various electrochemical techniques are available to continuously monitor corrosion in conditions simulating those on the secondary side of PWR steam generators. This paper reviews those electrochemical techniques which are potentially useful to measure denting in tube-support crevices in situ. Attention is also given to corollary needs for monitoring the water chemistry which leads to corrosive attack. Finally some suggestions are offered for corrosion monitoring in autoclaves, model boilers and operating steam generators

[en] Laboratory experiments were conducted to simulate the erosion-corrosion of aluminum fuel cladding in water-cooled, plutonium producing, nuclear reactors. Water quality was critical in causing attack in high temperature pressurized water. Little attack occurred in distilled water, whereas attack was progressively worse in river water and well water. Attack in well water was simulated by dissolving 50 ppm CaCO₃ and 10 ppm SiO₂ in distilled water. A corrosion enhancing synergism was apparent between dissolved bicarbonate and silicate ions. 12 refs

[en] The purpose of the Yucca Mountain Site Characterization Project is to evaluate Yucca Mountain for its suitability as a potential site for the nation's first high-level nuclear waste repository. As part of this effort, Lawrence Livermore National Laboratory (LLNL) has been occupied for a number of years with developing and evaluating the performance of waste packages for the potential repository. In recent years this work has been carried out under the guidance of and in collaboration with the Management and Operating contractor for the Civilian Radioactive Waste Management System, TRW Environmental Safety Systems, Inc., which in turn reports to the Office of Civilian Radioactive Waste Management of the US Department of Energy. This report summarizes the history of the selection and characterization of materials to be used in the engineered barrier system for the potential repository at Yucca Mountain, describes the current candidate materials, presents a compilation of their properties, and summarizes available corrosion data and modeling. The term ''engineered materials'' is intended to distinguish those materials that are used as part of the engineered barrier system from the natural, geologic materials of the site

[en] Several candidate container materials have been studied in modified Yucca Mountain (YM) ground water in the presence or absence of YM bacteria. YM bacteria increased corrosion rates by 5--6 fold in UNS G10200 carbon steel, and nearly 100-fold in UNS N04400 Ni-Cu alloy. YM bacteria caused microbiologically influenced corrosion (MIC) through de-alloying or Ni-depletion of Ni-Cu alloy as evidenced by scanning electronic microscopy (SEM) and inductively coupled plasma spectroscopy (ICP) analysis. MIC rates of more corrosion-resistant alloys such as UNS N06022 Ni-Cr-Mo- W alloy, UNS N06625 Ni-Cr-Mo alloy, and UNS S30430 stainless steel were measured below 0.05 microm/yr, however YM bacteria affected depletion of Cr and Fe relative to Ni in these materials. The chemical change on the metal surface caused by depletion was characterized in anodic polarization behavior. The anodic polarization behavior of depleted Ni-based alloys was similar to that of pure Ni

[en] During localized corrosion, a local cell is established between an anode within a crevice or pit and a cathode on the surrounding passive surface. Data are presented to show that concentrated acidic chloride solutions, simulating corrosion product hydrolysis within a crevice or pit, produce potentials which are active (negative) to the normal surface passive potential. This behaviour explains the previously observed active drift of corrosion potential after initiation of crevice or pitting attack in dilute chloride solutions. The active state in concentrated chloride solutions was quite noble (positive) compared to the active state in more dilute solutions. Thus, there is no need to invoke ohmic resistance effects to account for the active state within a crevice or pit. Experiments were devised in which the local anode within a crevice was physically separated from the nearby passive-surface cathode. When the two were coupled together electrically, the cathode surfaces were polarized nearly to the unpolarized local anode potential, with only a few millivolts anodic polarization at the anode within the crevice. The rate of localized corrosion appears from the data to be limited by the rate of dissolved-oxygen reduction on the cathode surfaces. Thus, localized corrosion in dilute chloride solutions will be increased by (a) raising the temperature, (b) adding an oxidizer such as Fe³⁺ ions, or (c) substituting external anodic polarization for dissolved oxidizers. The overall potential Esub(corr), acquired by a specimen undergoing pitting or crevice corrosion is demonstrated to be near the protection potential, Esub(p), below which pitting corrosion cannot propagate. Any potential active to Esub(corr) and Esub(p) results in cathodic polarization and suppression of the anode reaction in a crevice or pit. (author)

[en] The effect of inelastic collisions on the ratio of the longitudinal to lateral diffusion coefficients for electrons in electrostatic fields in gases is investigated for several different momentum transfer cross sections. The effect of varying both the strength of the inelastic effects and their energy dependence is examined and the results are used to discuss some of the Dsub(L)/μ data of Wagner et al. (1967). (Author)