scholarly journals Radiation damage effects on helium diffusion in zircon

2021 ◽  
Vol 36 (16) ◽  
pp. 3239-3247
Author(s):  
A. Diver ◽  
O. Dicks ◽  
A. M. Elena ◽  
I. T. Todorov ◽  
T. Geisler ◽  
...  
Keyword(s):  
Activation Energy ◽  
Radiation Damage ◽  
Structural Disorder ◽  
Fast Diffusion ◽  
Helium Bubbles ◽  
Helium Atoms ◽  
Using Data ◽  
Effects Of Radiation ◽  
Dynamics Simulations ◽  
Helium Diffusion

AbstractWe report the effects of radiation damage on helium diffusion in zircon using data from molecular dynamics simulations. We observe an increase in activation energy for helium diffusion as a result of radiation damage and increasing structural disorder. The activation energy in a heavily damaged region is smaller than in a completely amorphous system which is correlated with remaining order in the cation sublattices of the damaged structure not present in the fully amorphized system. The increase in activation energy is related to the disappearance of fast diffusion pathways that are present in the crystal. Consistent with the change in activation energy, we observe the accumulation of helium atoms in the damaged structure and discuss the implications of this effect for the formation of helium bubbles and zircon’s performance as an encapsulation material for nuclear waste. Graphic abstract

Empirical constraints on the effects of radiation damage on helium diffusion in zircon

2017 ◽  
Vol 218 ◽  
pp. 308-322 ◽  
Author(s):  
Alyssa J. Anderson ◽  
Kip V. Hodges ◽  
Matthijs C. van Soest
Keyword(s):  
Radiation Damage ◽  
Effects Of Radiation ◽  
Helium Diffusion

Finite Element Analysis of Composite Ceramic-Concrete Slab Constructions Exposed to Fire

2016 ◽  
Vol 861 ◽  
pp. 88-95
Author(s):  
Balázs Nagy ◽  
Elek Tóth
Keyword(s):  
Composite Structures ◽  
Elevated Temperatures ◽  
Cfd Simulation ◽  
Concrete Slab ◽  
Composite Ceramic ◽  
Reinforced Concrete Beam ◽  
Element Analysis ◽  
Standard Fire ◽  
Using Data ◽  
Dynamics Simulations

In this research, conjugated thermal and fluid dynamics simulations are presented on a modern hollow clay slab blocks filled pre-stressed reinforced concrete beam slab construction. The simulation parameters were set from Eurocode standards and calibrated using data from standardized fire tests of the same slab construction. We evaluated the temperature distributions of the slabs under transient conditions against standard fire load. Knowing the temperature distribution against time at certain points of the structure, the loss of load bearing capacity of the structure is definable at elevated temperatures. The results demonstrated that we could pre-establish the thermal behavior of complex composite structures exposed to fire using thermal and CFD simulation tools. Our results and method of fire resistance tests can contribute to fire safety planning of buildings.

Mechanisms and kinetics of initial pyrolysis and combustion reactions of 1,1-diamino-2,2-dinitroethylene from density functional tight-binding molecular dynamics simulations

2019 ◽  
Vol 97 (11) ◽  
pp. 795-804 ◽  
Author(s):  
Dong Xiang ◽  
Weihua Zhu
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Density Functional ◽  
Tight Binding ◽  
Combustion Process ◽  
Exponential Factor ◽  
Three Stages ◽  
Dynamics Simulations ◽  
Combustion Processes ◽  
Kinetics Of

The density functional tight-binding molecular dynamics approach was used to study the mechanisms and kinetics of initial pyrolysis and combustion reactions of isolated and multi-molecular FOX-7. Based on the thermal cleavage of bridge bonds, the pyrolysis process of FOX-7 can be divided into three stages. However, the combustion process can be divided into five decomposition stages, which is much more complex than the pyrolysis reactions. The vibrations in the mean temperature contain nodes signifying the formation of new products and thereby the transitions between the various stages in the pyrolysis and combustion processes. Activation energy and pre-exponential factor for the pyrolysis and combustion reactions of FOX-7 were obtained from the kinetic analysis. It is found that the activation energy of its pyrolysis and combustion reactions are very low, making both take place fast. Our simulations provide the first atomic-level look at the full dynamics of the complicated pyrolysis and combustion process of FOX-7.

scholarly journals A NOVEL DESIGN OF PERISTALTIC CARBON NANO PUMP AND AN ANALYSIS OF HELIUM FLOW

2021 ◽  
Vol 55 (6) ◽  
Author(s):  
M. Gokhan Günay ◽  
Ubade Kemerli
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Pump Design ◽  
Helium Atoms ◽  
Multi Walled Carbon Nanotubes ◽  
Temperature And Pressure ◽  
Dynamics Simulations ◽  
Walled Carbon Nanotubes ◽  
Novel Design ◽  
Main Carbon

A novel nano-scale pump that can transport atoms or small molecules with a peristaltic motion is designed. It is proven by molecular-dynamics simulations that the introduced nano-pump design works properly. The designed nano-pump consists of one main carbon nanotube named the flow tube and two rotors where multi-walled carbon nanotubes are attached. The pumping of helium atoms by the designed peristaltic carbon nano-pump is investigated by molecular-dynamics simulations. For varying rotor speeds and blade counts, time-averaged velocity, temperature, and pressure results of pumped helium atoms are calculated, and relationships between them are modeled as polynomial surfaces. The results showed that rotor frequency increases the velocity of helium linearly and the temperature and pressure of helium non-linearly. Furthermore, the blade count of the proposed mechanism does not substantially affect the velocity as per the previous studies in the literature.

scholarly journals LATE RADIATION TOXICITY AFTER RADICAL RADIOTHERAPY FOR GENITAL CANCER

2020 ◽  
Vol 25 ◽  
pp. 130-147
Author(s):  
O. Sukhina ◽  
◽  
K. Nemaltsova ◽  
O. Panov ◽  
◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Radiation Damage ◽  
Malignant Tumors ◽  
Practical Experience ◽  
Radiation Toxicity ◽  
Long Term Effects ◽  
Radiation Cystitis ◽  
Local Radiation ◽  
Effects Of Radiation ◽  
Female Genital

Radiation therapy for malignant tumors of the female genital area, even with the use of modern radiotherapy equipment and dosimetric planning, causes the development of local radiation changes. An approach involving methods of general and local exposure is used in their treatment. One of the most promising directions is the creation of optimal combinations of medicines (in the form of ointments, gels, aerosols, suppositories, etc.), which have a therapeutic effect on the inflammatory process. The article reflects the clinical course and stage of occurrence of late radiation reactions of the skin, vaginal/cervix mucosa, bladder, and intestines, as well as the features of their treatment. Literary data and own practical experience in the treatment of radiation complications are presented. When reviewing the topic under study, it could be concluded that the leading cause of the development of local radiation damage is the errors in the planning and implementation of radiation therapy, when high absorbed doses that exceed the tolerance of healthy tissues are used. Another reason for this is the poor accounting for dose distribution of ionizing radiation in tissues, the presence of concomitant diseases in patients, and the underestimation of the long-term effects of radiation. Key words: female genital organs, radiation damage, radiodermatitis, radioepitheliitis, radiation rectitis, radiation cystitis.

A Study of Radiation Effects in Curium-Doped Gd2Ti2O7 (Pyrochlore) and CaZrTi2O7 (Zirconolite)

1981 ◽  
Vol 11 ◽  
Author(s):  
J.W. Wald ◽  
P. Offemann
Keyword(s):  
Radiation Damage ◽  
Nuclear Waste ◽  
Radiation Effects ◽  
Laboratory Data ◽  
Primary Host ◽  
Waste Forms ◽  
Rare Earth Titanate ◽  
Effects Of Radiation ◽  
Similar Phase ◽  
Nuclear Waste Forms

Radiation effects studies in both glass and glass ceramic nuclear waste forms have identified a rare-earth titanate phase of the general formula (RE) 2Ti207 which is capable of acting as a host phase for actinides.1,2 Ringwood and co-workers3 have also proposed a structurally similar phase, zirconolite (CaZrTi2 07), as one of the primary host phases in the SYNROC waste form. Data from these and other previous studies, as well as mineralogical information available on these titanate phases, have not provided an unambiguous interpretation of the effects of radiation damage relative to nuclear waste forms. This paper reports new laboratory data concerning radiation damage effects in both of these phases.

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