An Electrochemical Approach to Predicting Long-Term Localized Corrosion of Corrosion-Resistant High-Level Waste Container Materials

CORROSION ◽  
2000 ◽  
Vol 56 (1) ◽  
pp. 90-104 ◽  
Author(s):  
D. S. Dunn ◽  
G. A. Cragnolino ◽  
N. Sridhar
Keyword(s):  
Localized Corrosion ◽  
High Level Waste ◽  
Corrosion Resistant ◽  
Waste Container ◽  
Electrochemical Approach ◽  
High Level

The Use of Repassivation Potential in Predicting The Performance of High-Level Nuclear Waste Container Materials

1994 ◽  
Vol 353 ◽  
Author(s):  
Narasi Sridhar ◽  
Darrell Dunn ◽  
Gustavo Cragnolino
Keyword(s):  
Field Tests ◽  
Localized Corrosion ◽  
High Level Waste ◽  
Repassivation Potential ◽  
Waste Container ◽  
Highly Sensitive ◽  
Plant Equipment ◽  
Robust Parameter ◽  
High Level Nuclear Waste ◽  
High Level

AbstractLocalized corrosion in aqueous environments forms an important bounding condition for the performance assessment of high-level waste (HLW) container materials. A predictive methodology using repassivation potential is examined in this paper. It is shown, based on long-term (continuing for over 11 months) testing of alloy 825, that repassivation potential of deep pits or crevices is a conservative and robust parameter for the prediction of localized corrosion. In contrast, initiation potentials measured by short-term tests are non-conservative and highly sensitive to several surface and environmental factors. Corrosion data from various field tests and plant equipment performance are analyzed in terms of the applicability of repassivation potential. The applicability of repassivation potential for predicting the occurrence of stress corrosion cracking (SCC) and intergranular corrosion in chloride containing environments is also examined.

An Approach to Analysis of High Level waste Container Performance in an Unsaturated Repository Environment

1993 ◽  
Vol 333 ◽  
Author(s):  
John C. Walton ◽  
Narasi Sridhar ◽  
Gustavo Cragnolino ◽  
Tony Torng ◽  
Prasad Nair
Keyword(s):  
Dominant Role ◽  
Near Field ◽  
Temperature Fields ◽  
Localized Corrosion ◽  
High Level Waste ◽  
Quantitative Methodology ◽  
Waste Container ◽  
Wide Range ◽  
Engineered Barrier ◽  
High Level

ABSTRACTOne of the requirements for the performance of waste packages prescribed in 10CFR 60.113 is that the high level waste must be “substantially completely” contained for a minimum period of 300 to 1000 years. During this period, the radiation and thermal conditions in the engineered barrier system and the near-field environment are dominated by fission product decay. In the present U.S design of the engineered barrier system, the outer container plays a dominant role in maintaining radionuclide containment. A quantitative methodology for analyzing the performance of the container is described in this paper. This methodology enables prediction of the evolution of the waste package environment in terms of temperature fields, stability of liquid water on the container surface, and concentration of aggressive ions such as chloride. The initiation and propagation of localized corrosion is determined by the corrosion potential of the container material and critical potentials for localized corrosion. The coiTOsion potential is estimated from the kinetics of the anodic and cathodic reactions including oxygen diffusion through scale layers formed on the container surface. The methodology described is applicable to a wide range of metals, alloys and environmental conditions.

A Review of 25 years of Corrosion Studies on HLW Container Materials at the CEA

2006 ◽  
Vol 985 ◽  
Author(s):  
Max Helie
Keyword(s):  
Carbon Steel ◽  
Base Alloy ◽  
Atomic Energy Commission ◽  
Propagation Rate ◽  
High Level Waste ◽  
Corrosion Resistant ◽  
Nickel Base ◽  
Corrosion Mechanisms ◽  
High Level

ABSTRACTThe Commissariat à l'Énergie Atomique (CEA, French Atomic Energy Commission) has been involved in researches on nuclear waste management for more than 25 years. One of the key issues is the prediction of the long term behavior and aging of the High Level Waste (HLW) containers in order to develop concepts that will ensure the confinement of the activity over extremely long periods of time.Preliminary studies were carried out on two concepts, one of a thin "corrosion resistant" container made of titanium or nickel base alloy, and the other on a thick "corrosion allowance" container made or carbon steel.The results of these experiments showed that the "corrosion resistant" concept led to a high uncertainty on the development and propagation rate of localized forms of corrosion, and the concept of geological disposal in an argillaceous host formation of thick waste containers made of carbon steel was chosen as the reference. Studies are still in progress to better assess the corrosion mechanisms relevant to this situation in order to provide reliable models for the long term prediction of the containers corrosion behavior.

Stochastic Modeling of Long-Term Waste Package Degradation Incorporating Expert Elicitation on Corrosion Processes

1999 ◽  
Vol 556 ◽  
Author(s):  
J. H. Lee ◽  
K. G. Mori ◽  
D. E. Longsine ◽  
B. E. Bullard
Keyword(s):  
Primary Component ◽  
Expert Elicitation ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Reference Case ◽  
Waste Package ◽  
Waste Container ◽  
Reference Design ◽  
High Level

AbstractThe Viability Assessment (VA) of the potential repository for high-level nuclear waste at Yucca Mountain, Nevada was completed [1]. In the VA design concept, a two-layer waste container provides the primary component of the engineered barrier system (EBS). The VA reference design specifies a 100-mm thick carbon steel as the outer barrier and a 20-mm thick Alloy 22 as the inner barrier. A stochastic simulation model was developed to analyze long-term performance of the waste package in the potential repository. The model was developed by incorporating the latest corrosion data and models for the candidate waste package materials and the information developed from the Waste Package Degradation Expert Elicitation (WPDEE) [2].The reference case results showed that only a small fraction of waste packages fail by localized corrosion (i.e., pit penetrations). The analysis also indicated the degradation mode that is most important to long-term waste package degradation is general corrosion (or passive dissolution) of the inner barrier under dripping conditions. However, the general corrosion rates for dripping conditions used in the analysis have a range over three to five orders of magnitude. This is due mainly to a lack of information on local chemical and electrochemical conditions on the inner barrier after the outer barrier breach. This paper discusses further the areas and issues that need improvement to reduce uncertainty in the waste package degradation analysis. It also discusses additional waste package degradation modes and associated processes that need to be included in the future analysis for the potential repository to enhance the confidence of the analysis.

Long-Term Extrapolation of Passive Behavior of Alloy 22

2002 ◽  
Vol 757 ◽  
Author(s):  
Osvaldo Pensado ◽  
Darrell S. Dunn ◽  
Gustavo A. Cragnolino
Keyword(s):  
Current Density ◽  
Mechanistic Model ◽  
Localized Corrosion ◽  
High Level Waste ◽  
Anodic Current Density ◽  
Oxide Interface ◽  
Enhanced Diffusion ◽  
Passive Behavior ◽  
High Level

ABSTRACTCommon assumptions to extrapolate the lifetime of proposed high-level waste disposal containers made of Ni-Cr-Mo alloys, in the absence of environmental and electrochemical conditions leading to localized corrosion and stress corrosion cracking, are evaluated based on a mechanistic model for passive dissolution. The predominant charge conduction mechanism through the oxide film formed on Ni-Cr-Mo alloys is hypothesized to be interstitial transport of metal cations. Dissolution of the alloy and conduction of interstitial species through the film create vacancies in the alloy. The anodic current density under potentiostatic control decreases as a function of time, and potentiostatic decays in the current density are rationalized on the basis of vacancy accumulation at the metal-oxide interface. It is concluded that the dissolution process is regulated by vacancy-enhanced diffusion of the elements in the alloy. Long-term stoichiometric dissolution arises if the diffusion coefficients of the alloying elements are similar. No credible scenario is envisioned by which catastrophic failure may occur as a result of longterm passive dissolution.

HLW Container Corrosion in Geological Disposal Conditions

1985 ◽  
Vol 50 ◽  
Author(s):  
Max Helie ◽  
Georges Plante
Keyword(s):  
Waste Disposal ◽  
The Other ◽  
Current Concept ◽  
High Level Waste ◽  
Aqueous Corrosion ◽  
Geological Disposal ◽  
Corrosion Resistant ◽  
Waste Container ◽  
Geological Formation ◽  
High Level

In order to prevent a possible return of activity to the biosphere, the current concept for High Level Waste disposal is to build a multi barrier system consisting of a slow leaching waste form, the waste container, backfilling materials and the geological formation. The main threat to the integrity of the container is aqueous corrosion and two concepts are currently accepted, one based on a thin “corrosion resistant” overpack, the other on a thick “corrosion allowance” canister.

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