The Development of a Mechanistic Basis for Modelling Fuel Dissolution and Container Failures Under Waste Vault Conditions

1988 ◽  
Vol 127 ◽  
Author(s):  
D. W. Shoesmith ◽  
S. Sunder ◽  
B. M. Ikeda ◽  
F. King
Keyword(s):  
Experimental Data ◽  
Titanium Alloys ◽  
Nuclear Waste ◽  
Waste Disposal ◽  
Predictive Models ◽  
Crevice Corrosion ◽  
Electrochemical Techniques ◽  
Short Term ◽  
Mechanistic Basis ◽  
Radionuclide Release

ABSTRACTDue to the long containment periods required for radionuclides in a nuclear waste disposal vault, the justification that a particular containment system is acceptable will be based on relatively short-term experimental data used to support predictive models. To justify this approach, we must possess a sound mechanistic understanding of processes such as fuel dissolution, radionuclide release and container corrosion. Since these processes are driven by oxidants in the vault, it is natural to study them by electrochemical techniques. In this paper, we have reviewed a number of electrochemical methods used in the study of waste vault reactions. More detailed descriptions are given of the development of predictive models for the dissolution of UO2, the crevice corrosion of titanium alloys and the uniform dissolution of copper.

Crevice Corrosion in Oxygen Scavenger Injection System

2021 ◽  
Author(s):  
Amela Keserovic ◽  
Øystein Birketveit
Keyword(s):  
Crevice Corrosion ◽  
Electrochemical Techniques ◽  
Localized Corrosion ◽  
Injection System ◽  
Recent Experience ◽  
Oxygen Scavenger ◽  
Short Term ◽  
Oxygen Scavengers ◽  
Cyclic Potentiodynamic Polarization ◽  
Stainless Steel 316

Abstract Biulfite-based oxygen scavengers (OS) have been traditionally used in oilfields to reduce corrosion resulting from dissolved oxygen. Recent experience with a leakage in OS-A oxygen scavenger injection system has shown that the same production chemicals in neat form can cause corrosion themselves, specifically – crevice corrosion. In this paper a tendency of three bisulfite-based oxygen scavengers to initiate crevice corrosion on 316 stainless steel (316 SS) was evaluated by means of long-term exposure tests and short-term electrochemical techniques; cyclic potentiodynamic polarization (CPP) and Tsujikawa–Hisamatsu electrochemical method (THE). The testing was performed at ambient temperature and pressure to mimic the topside injection system conditions. The tested oxygen scavengers differed in bisulfite concentration (OS-A, 341 g/L; OS-B, 328 g/L; OS-C, 750 g/L) and pH (pH 3, 6 and 5, respectively). Two 316 SS coupons were attached together using elastomer O-rings to simulate steel-to-steel crevice between. The surface of the coupons was examined at 50x magnification after the test termination. The results presented herein showed that 30-day long exposure tests were not long or aggressive enough to provide information about the corrosivity of the chemicals in terms of crevice corrosion. Instead, the combination of short-term electrochemical techniques proved to be useful in explaining a possible cause of the leakage in OS-A injection system and allowed ranking of the products based on their tendency to initiate localized corrosion.

The Effect of Chloride Concentration on Crevice Corrosion of some Welded Titanium Alloys

2008 ◽  
Vol 59 (2) ◽  
pp. 140-144
Author(s):  
Laurentiu Popa ◽  
Maria Radulescu ◽  
Alice Dinu ◽  
Lucian Velciu ◽  
Ioan Viorel Branzoi
Keyword(s):  
Waste Management ◽  
Titanium Alloys ◽  
Nuclear Waste ◽  
Crevice Corrosion ◽  
Chloride Concentration ◽  
Geological Disposal ◽  
Buffer Material ◽  
High Level Nuclear Waste ◽  
High Level

Geological disposal is identified by nearly all experts in the field of waste management as the only safe and sustainable option presently available, but the progress towards its implementation is slow. The nuclear waste must be safely storaged for hundreds of thousand years. Titanium alloys are some of the most promising candidates as container materials for the long-term disposal of high level nuclear waste (HLW) in rock salt formations. In the case of titanium waste containers, between the containers walls and the surrounding buffer material used to pack the disposal borehole some crevices can appear in the welded zone container/ shielding lid, under a biofilm etc. For this purpose we studied the effect of chloride concentration on crevice corrosion of some welded titanium alloys (Grade 2 and Grade 12, respectively) in chloride solutions at 90oC by electrochemical methods (Ecorr vs time, potentiodynamic tests).

scholarly journals Requirement of the assessment strategy for biosphere in mature safety cases for nuclear waste repositories – Finland case

2015 ◽  
Vol 79 (6) ◽  
pp. 1607-1612 ◽  
Author(s):  
A. T. K. Ikonen
Keyword(s):  
Nuclear Waste ◽  
Waste Disposal ◽  
Nuclear Waste Disposal ◽  
Vital Role ◽  
Simple Boundary ◽  
Safety Case ◽  
Safety Cases ◽  
High Level ◽  
Radionuclide Release ◽  
Waste Repositories

AbstractIn safety assessments for nuclear waste disposal, the biosphere is a completely open system, whereas the bedrock can be treated with comparably simple boundary conditions. The bedrock has a vital role in providing and maintaining favourable conditions for the waste, but the public interest tends to focus on the biosphere. More importantly, the bedrock groundwater does arrive from the biosphere. Also, the regulations usually set the safety criteria in terms of doses occurring in the biosphere. Thus, it is reasonable to address the biosphere as a part of the disposal system, performance of which should be described based on conceptual models that cover phenomena and processes controlling radionuclide release and transport. From these, the actual assessment models and data are expected to be derived based on high-level research and expertise obtained through empirical study. In this paper, the complexity expected of a biosphere assessment within a mature safety case is discussed through the example of the Finnish regulations and recent safety cases for nuclear waste disposal. Both elaborate and complex presentations and stylised approaches have their benefits, and a balance needs to be sought.

Preferential Dissolution Phenomena of Nuclear Waste Materials

1982 ◽  
Vol 15 ◽  
Author(s):  
D. R. Clarke ◽  
J. F. Flintoff
Keyword(s):  
Nuclear Waste ◽  
Waste Materials ◽  
Green Density ◽  
Release Rates ◽  
Short Term ◽  
Rate Of Dissolution ◽  
Soluble Phase ◽  
Precursor Powders ◽  
Radionuclide Release ◽  
Preferential Dissolution

ABSTRACTPreferential dissolution of polyphase nuclear waste materials in short term leach tests can exaggerate radionuclide release rates when extrapolated to the lifetime of the waste form. Possible preferential leach phenomena are associated with the presence of cracks, intergranular phases and readily soluble phases. The rate of dissolution and the microstructural connectivity of the most soluble phase determine the period over which perferential dissolution is observable. The connectivity of phases is amenable to control during processing by altering the starting green density of the precursor powders.

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