scholarly journals Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 ∘C

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1272
Author(s):  
M. Carme Chaparro ◽  
Nicolas Finck ◽  
Volker Metz ◽  
Horst Geckeis
Keyword(s):  
Carbon Steel ◽  
Numerical Model ◽  
Cation Exchange ◽  
Reactive Transport ◽  
Corrosion Products ◽  
Mineral Dissolution ◽  
Long Term Results ◽  
Short Term ◽  
Complexation Reactions

The geological disposal in deep bedrock repositories is the preferred option for the management of high-level radioactive waste (HLW). In some of these concepts, carbon steel is considered as a potential canister material and bentonites are planned as backfill material to protect metallic waste containers. Therefore, a 1D radial reactive transport model has been developed in order to better understand the processes occurring during the long-term iron-bentonite interaction. The numerical model accounts for diffusion, aqueous complexation reactions, mineral dissolution/precipitation and cation exchange at a constant temperature of 25 ∘C under anoxic conditions. Our results suggest that Fe is sorbed at the montmorillonite surface via cation exchange in the short-term, and it is consumed by formation of the secondary phases in the long-term. The numerical model predicts precipitation of nontronite, magnetite and greenalite as corrosion products. Calcite precipitates due to cation exchange in the short-term and due to montmorillonite dissolution in the long-term. Results further reveal a significant increase in pH in the long-term, while dissolution/precipitation reactions result in limited variations of the porosity. A sensitivity analysis has also been performed to test the effect of selected parameters, such as corrosion rate, diffusion coefficient and composition of the bentonite porewater, on the corrosion processes. Overall, outcomes suggest that the predicted main corrosion products in the long-term are Fe-silicate minerals, such phases thus should deserve further attention as a chemical barrier in the diffusion of radionuclides to the repository far field.

scholarly journals Reactive transport modelling of long-term interactions between iron and MX-80 bentonite

2021 ◽  
Vol 1 ◽  
pp. 169-170
Author(s):  
M. Carme Chaparro ◽  
Nicolas Finck ◽  
Volker Metz ◽  
Horst Geckeis
Keyword(s):  
Carbon Steel ◽  
Numerical Model ◽  
Reactive Transport ◽  
Transport Model ◽  
Corrosion Products ◽  
Mineral Dissolution ◽  
Secondary Phases ◽  
Short Term ◽  
Complexation Reactions

Abstract. The geological disposal in deep bedrock repositories is the preferred option for the management of high-level radioactive waste. In some of these concepts, carbon steel is considered as potential canister material and bentonites are planned as backfill material to protect metal waste containers. Therefore, a 1D radial reactive transport model has been developed in order to better understand the processes occurring during the long-term iron–bentonite interaction. The conceptual model accounts for diffusion, chemistry of the porewater and aqueous complexation reactions, mineral dissolution/precipitation and absorption, at a constant temperature of 25 ∘C under anoxic conditions. The geometry of the axisymmetric model reflects the canister–bentonite interface and the bentonite. The primary phases considered are montmorillonitic smectite, quartz, muscovite, albite, illite, pyrite and calcite. We assume that carbon steel is composed only of iron. The potential secondary phases considered are from reported experiments, such as magnetite, nontronitic smectite, greenalite, cronstedtite and siderite. The numerical model results suggest that at the iron–bentonite interface, Fe is adsorbed at the smectite surface via ion exchange in the short term and it is consumed by formation of the secondary phases in the long term. Furthermore, calcite precipitates are due to cation exchange in the short term and due to montmorillonitic smectite dissolution in the long term. The numerical model predicts the precipitation of nontronitic smectite, magnetite and greenalite as corrosion products. Results further reveal a significant increase in pH in the long term, whereas dissolution/precipitation reactions result in limited variations of the porosity. Progressing bentonite dissolution owing to the rising pH and concomitantly increasing silicate concentrations in the porewater induce formation of Fe-silicates as corrosion products at the expense of magnetite. A sensitivity analysis has also been performed to study the effect of selected parameters, such as corrosion rate, diffusion coefficient and composition of the porewater, on the corrosion products. Overall, outcomes suggest that pH and concentration of dissolved Si play an important role in corrosion mechanisms. The predicted main secondary phases in the long term are Fe-silicate minerals. Thus, such phases deserve further attention as possible chemical barriers for radionuclide migration in the repository near-field.

Long-Term Results of Radioscapholunate Fusion Following Fractures of the Distal Radius

1997 ◽  
Vol 22 (6) ◽  
pp. 705-710 ◽  
Author(s):  
L. NAGY ◽  
U. BÜCHLER
Keyword(s):  
Long Term Results ◽  
Short Term ◽  
Non Union ◽  
Partial Fusion ◽  
Traumatic Lesions ◽  
Residual Motion ◽  
Radioscapholunate Fusion ◽  
Wrist Fusion

Fifteen patients with radioscapholunate (RSL) fusion for traumatic lesions of the radiocarpal junction, whose short-term results have been previously reported, were reassessed after an average follow-up time of 8 years. Five patients had undergone wrist fusion because of non-union or early progressive arthritis. Of the ten wrists with retained mobility, eight continued to function satisfactorily. Two wrists were painful for reasons other than secondary midcarpal arthritis. Patient satisfaction was comparable in both groups with the wrist score better for wrists with residual motion. The survival of RSL partial wrist fusion corresponded inversely with the number of preceding operations and the range of motion before partial fusion. Secondary midcarpal arthritis, if present, arose early and was well tolerated. Failures were strongly linked to technical mistakes and complications.

Long-Term Deformations of Strengthened Reinforced Concrete Linear Elements

2016 ◽  
Vol 691 ◽  
pp. 51-60 ◽  
Author(s):  
Martin Krizma ◽  
Lubomir Bolha
Keyword(s):  
Reinforced Concrete ◽  
Long Term Results ◽  
Short Term ◽  
Limit States ◽  
Linear Elements ◽  
Repeated Load ◽  
The Moment ◽  
Concrete Elements ◽  
Fiber Fabric

The issue of strengthening the damaged linear reinforced concrete elements have been engaged since 2008. We focused on the analysis of resistance and the characteristics of limit states of serviceability in the damaged and subsequently strengthened elements at a short-term loading. In the introduction phase, the strengthening of the elements was carried out with the following procedures – installation of an overlayer on the coupling board or a combination of the board and use of glass – fiber fabric (GFRP). The strengthening was also affected by the type of contact (reinforced/non-reinforced) – the deformed element/coupling board and its effect on resistance, type of deformation and serviceability. In the non-reinforced contact, we applied some of the types of adjustments to the surface of the strengthened element. At the moment, we are dealing with the effects of time and repeated load on the strengthened elements. The results correspond to the reinforced contact. The values are compared with the short-term results of the strengthened beams and with the long-term results of the beams prepared for strengthening.

The Response of the Neurotic Personality to Abreaction

1952 ◽  
Vol 98 (413) ◽  
pp. 630-639 ◽  
Author(s):  
Anthony Hordern
Keyword(s):  
Long Term Results ◽  
Short Term ◽  
Initial Results

The purpose of this paper is to draw attention to results achieved in selected neurotic cases treated by short-term abreactive techniques in St. Clement's Hospital during recent months. Patients usually stay in for about two months; as yet it is too early to assess long-term results of this form of treatment, but it is felt that some of the initial results are extremely encouraging.

scholarly journals Preoperative Somatostatin Analogues in Patients with Newly-diagnosed Acromegaly: A Systematic Review and Meta-analysis of Comparative Studies

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Chengxian Yang ◽  
Ge Li ◽  
Shenzhong Jiang ◽  
Xinjie Bao ◽  
Renzhi Wang
Keyword(s):  
Systematic Review ◽  
Comparative Studies ◽  
Meta Analysis ◽  
Somatostatin Analogues ◽  
Long Term Results ◽  
Current Evidence ◽  
Cochrane Library ◽  
Cure Rate ◽  
Short Term

Abstract Biochemical remission after transsphenoidal surgery is still unsatisfied in acromegaly patients with macroadenomas, especially with invasive macroadenomas. Concerning the impact of preoperative somatostatin analogues (SSAs) on surgical outcomes, previous studies with limited cases reported conflicting results. To assess current evidence of preoperative medical treatment, we performed a systematic review and meta-analysis of comparative studies. A literature search was conducted in Pubmed, Embase, and the Cochrane Library. Five randomized controlled trials (RCT) and seven non-RCT comparative studies were included. These studies mainly focused on pituitary macroadenomas though a small number of microadenoma cases were included. For safety, preoperative SSAs were not associated with elevated risks of postoperative complications. With respect to efficacy, the short-term cure rate was improved by preoperative SSAs, but the long-term cure rate showed no significant improvement. For invasive macroadenomas, the short-term cure rate was also improved, but the long-term results were not evaluable in clinical practice because adjuvant therapy was generally required. In conclusion, preoperative SSAs are safe in patients with acromegaly, and the favorable impact on surgical results is restricted to the short-term cure rate in macroadenomas and invasive macroadenomas. Further well-designed RCTs to examine long-term results are awaited to update the finding of this meta-analysis.

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