scholarly journals Effects of Radiation Exposure on SRL 131 Composition Glass in a Steam Environment

1993 ◽  
Vol 333 ◽  
Author(s):  
D. J. Wronkiewicz ◽  
C. R. Bradley ◽  
J. K. Bates ◽  
L. M. Wang
Keyword(s):  
Radiation Exposure ◽  
Glass Surface ◽  
Average Rate ◽  
Reaction Times ◽  
Secondary Phase ◽  
Reaction Rates ◽  
Liquid Volume ◽  
Secondary Phase Formation ◽  
Effects Of Radiation ◽  
Doped Glass

ABSTRACTMonoliths of SRL 131 borosilicate glass were irradiated in a saturated air-steam environment, at temperatures of 150°C, to examine the effects of radiation on nuclear waste glass behavior. Half of the tests used actinide and Tc-99 doped glass and were exposed to an external ionizing gamma source, while the remaining glass samples were doped only with uranium and were reacted without any external radiation exposure. The effects of radiation exposure on glass alteration and secondary phase formation were determined by comparing the reaction rates and mineral paragenesis of the two sets of samples.All glass samples readily reacted with the water that condensed on their surfaces, producing two types of smectite clay within the first three days of testing. Additional crystalline phases precipitated on the altered glass surface with increasing reaction times, including zeolites, smectite, calcium and sodium silicates, phosphates, evaporitic salts, and uranyl silicates. Similar phases were produced on both the nonirradiated and irradiated samples; however, the quantity of precipitates was increased and the rate of paragenetic sequence development was accelerated in the latter. After 56 days of testing, the composite smectite layer developed at an average rate of ~0.16 and 0.63 µm/day for the nonirradiated and irradiated samples, respectively. These comparisons indicate that layer development is accelerated approximately four-fold due to the radiation exposure at high glass surface area/liquid volume (SA/V) conditions. This increase apparently occurs in response to the rapid concentration of radiolytic products, including nitric acid, in the thin films of water contacting the sample monoliths.

scholarly journals The Importance of Secondary Phases in Glass Corrosion

1990 ◽  
Vol 212 ◽  
Author(s):  
William L. Ebert ◽  
John K. Bates
Keyword(s):  
Computer Simulations ◽  
Reaction Times ◽  
Microscopic Analysis ◽  
Secondary Phase ◽  
Secondary Phases ◽  
Reaction Behavior ◽  
Glass Corrosion ◽  
Model Glass ◽  
Secondary Phase Formation

ABSTRACTThe analytical expression used to model glass reaction in computer simulations such as EQ6 is compared to the results of experiments used to support the simulations. The expression correctly predicts the acceleration observed in experiments performed at high glass surface area/1eachant volume ratios (SA/V) upon the formation of secondary phases. High resolution microscopic analysis of reacted glass samples suggests that the accelerated nature of the reaction after secondary phase formation is due to changes in the reaction affinity (i.e., is a solution effect) and not a change in the glass reaction mechanism. The composition of solutions in contact with reacted samples reflect the effects of the secondary phases predicted in the model. Experiments which lead to the generation of secondary phases within short reaction times can be used to identify important secondary phases which must be Included in the data base of computer simulations to correctly project long-term glass reaction behavior.

scholarly journals Electrolyte-Assisted Hydrogen Cycling in Lithium and Sodium Alanates at Low Pressures and Temperatures

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5868
Author(s):  
Jason Graetz ◽  
John J. Vajo
Keyword(s):  
Growth Parameters ◽  
Reaction Times ◽  
Hydrogen Uptake ◽  
Hydrogen Desorption ◽  
Reaction Rates ◽  
Rate Coefficients ◽  
Aluminum Hydrides ◽  
Dehydrogenation Reactions ◽  
Low Pressures ◽  
Sodium Alanates

An investigation of electrolyte-assisted hydrogen storage reactions in complex aluminum hydrides (LiAlH4 and NaAlH4) reveals significantly reduced reaction times for hydrogen desorption and uptake in the presence of an electrolyte. LiAlH4 evolves ~7.8 wt% H2 over ~3 h in the presence of a Li-KBH4 eutectic at 130 °C compared to ~25 h for the same material without the electrolyte. Similarly, NaAlH4 exhibits 4.8 wt% H2 evolution over ~4 h in the presence of a diglyme electrolyte at 150 °C compared to 4.4 wt% in ~15 h for the same material without the electrolyte. These reduced reaction times are composed of two effects, an increase in reaction rates and a change in the reaction kinetics. While typical solid state dehydrogenation reactions exhibit kinetics with rates that continuously decrease with the extent of reaction, we find that the addition of an electrolyte results in rates that are relatively constant over the full desorption window. Fitting the kinetics to an Avrami-Erofe’ev model supports these observations. The desorption rate coefficients increase in the presence of an electrolyte, suggesting an increase in the velocities of the reactant-product interfaces. In addition, including an electrolyte increases the growth parameters, primarily for the second desorption steps, resulting in the observed relatively constant reaction rates. Similar effects occur upon hydrogen uptake in NaH/Al where the presence of an electrolyte enables hydrogenation under more practical low temperature (75 °C) and pressure (50 bar H2) conditions.

scholarly journals DNA-Platinum Thin Films for Use in Chemoradiation Therapy Studies

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Mohammad Rezaee ◽  
Elahe Alizadeh ◽  
Darel Hunting ◽  
Léon Sanche
Keyword(s):  
Inductively Coupled Plasma ◽  
Reaction Times ◽  
Substantial Effect ◽  
Chemotherapeutic Agents ◽  
Chemoradiation Therapy ◽  
Inductively Coupled ◽  
Dna Films ◽  
Effects Of Radiation ◽  
Dna Platination

Dry films of platinum chemotherapeutic drugs covalently bound to plasmid DNA (Pt-DNA) represent a useful experimental model to investigate direct effects of radiation on DNA in close proximity to platinum chemotherapeutic agents, a situation of considerable relevance to understand the mechanisms underlying concomitant chemoradiation therapy. In the present paper we determine the optimum conditions for preparation of Pt-DNA films for use in irradiation experiments. Incubation conditions for DNA platination reactions have a substantial effect on the structure of Pt-DNA in the films. The quantity of Pt bound to DNA as a function of incubation time and temperature is measured by inductively coupled plasma mass spectroscopy. Our experiments indicate that chemical instability and damage to DNA in Pt-DNA samples increase when DNA platination occurs at37°Cfor 24 hours, the condition which has been extensively used for in vitro studies. Platination of DNA for the formation of Pt-DNA films is optimal at room temperature for reaction times less than 2 hours. By increasing the concentration of Pt compounds relative to DNA and thus accelerating the rate of their mutual binding, it is possible to prepare Pt-DNA samples containing known concentrations of Pt while reducing DNA degradation caused by more lengthy procedures.

scholarly journals Ureido Functionalization through Amine-Urea Transamidation under Mild Reaction Conditions

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1583
Author(s):  
Natalia Guerrero-Alburquerque ◽  
Shanyu Zhao ◽  
Daniel Rentsch ◽  
Matthias M. Koebel ◽  
Marco Lattuada ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Reaction Times ◽  
Reaction Rates ◽  
Secondary Amines ◽  
Isocyanic Acid ◽  
Advantages And Disadvantages ◽  
Major Disadvantage ◽  
Wide Range ◽  
Potential Alternative ◽  
Full Conversion

Ureido-functionalized compounds play an indispensable role in important biochemical processes, as well as chemical synthesis and production. Isocyanates, and KOCN in particular, are the preferred reagents for the ureido functionalization of amine-bearing compounds. In this study, we evaluate the potential of urea as a reagent to graft ureido groups onto amines at relatively low temperatures (<100 °C) in aqueous media. Urea is an inexpensive, non-toxic and biocompatible potential alternative to KOCN for ureido functionalization. From as early as 1864, urea was the go-to reagent for polyurea polycondensation, before falling into disuse after the advent of isocyanate chemistry. We systematically re-investigate the advantages and disadvantages of urea for amine transamidation. High ureido-functionalization conversion was obtained for a wide range of substrates, including primary and secondary amines and amino acids. Reaction times are nearly independent of substrate and pH, but excess urea is required for practically feasible reaction rates. Near full conversion of amines into ureido can be achieved within 10 h at 90 °C and within 24 h at 80 °C, and much slower reaction rates were determined at lower temperatures. The importance of the urea/amine ratio and the temperature dependence of the reaction rates indicate that urea decomposition into an isocyanic acid or a carbamate intermediate is the rate-limiting step. The presence of water leads to a modest increase in reaction rates, but the full conversion of amino groups into ureido groups is also possible in the absence of water in neat alcohol, consistent with a reaction mechanism mediated by an isocyanic acid intermediate (where the water assists in the proton transfer). Hence, the reaction with urea avoids the use of toxic isocyanate reagents by in situ generation of the reactive isocyanate intermediate, but the requirement to separate the excess urea from the reaction product remains a major disadvantage.

scholarly journals (Ti,Cr)C-Based Cermets with Varied Nicr Binder Content via Elemental SHS for Perspective Cutting Tools

Crystals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 412
Author(s):  
Stepan Vorotilo ◽  
Philipp V. Kiryukhantsev-Korneev ◽  
Boris S. Seplyarskii ◽  
Roman A. Kochetkov ◽  
Nail I. Abzalov ◽  
...  
Keyword(s):  
Solid Solution ◽  
Gas Permeability ◽  
Combustion Velocity ◽  
Cutting Tools ◽  
Secondary Phase ◽  
Fold Increase ◽  
Combustion Products ◽  
Secondary Phase Formation ◽  
Secondary Reactions ◽  
Nickel Binder

The effects of granulation of reactive mixtures Ti-Cr-C and Ti-Cr-C-Ni on the combustion temperature and velocity, as well as phase composition and mechanical properties (crushing ability) of combustion products, were studied. Granulation was associated with a 1.5-fold increase in combustion velocity, caused by a nearly 10-fold increase in gas permeability. Secondary reactions between TiC, Cr7C3, and molten Ni led to the formation of (Ti,Cr)C FCC solid solution and Ni2.88Cr1.12 intermetallics. After the combustion of Ti-Cr-C-Ni mixtures, prolonged fluorescence was registered, suggesting the exothermic nature of secondary phase formation reactions. The introduction of the nickel binder decreased the content of Cr in the solid solution (Ti,Cr)C owing to the formation of the Ni2.88Cr1.12 phase. To prevent the Cr depletion from the carbide solid solution, Ni-20%Cr binder was added to the granulated 80%(Ti + C)/20%(3Cr + 2C) mixture. Combustion of granulated mixture yielded brittle porous sinter cake, which was easy to crush and mill, whereas the combustion products from the powdered mixtures were more ductile and harder to crush.

scholarly journals Influence of ZnO addition and milling process on structure and conductivity of BaCe0.2Zr0.7Y0.1O3-δ ceramics

2021 ◽  
Vol 15 (3) ◽  
pp. 288-296
Author(s):  
Ana Ana Kaori de Oliveira Ouba ◽  
Adilson Chinelatto ◽  
Edson Grzebielucka ◽  
Kethlinn Ramos ◽  
Janaina Borcezi ◽  
...  
Keyword(s):  
Secondary Phase ◽  
Linear Shrinkage ◽  
High Energy ◽  
Milling Process ◽  
Sintering Aids ◽  
X Ray Diffraction ◽  
Sintering Aid ◽  
Secondary Phase Formation ◽  
Precursor Powders ◽  
Perovskite Lattice

Precursor powders for BaCe0.2Zr0.7Y0.1O3-?(BCZY27) ceramics were synthesized by a modified Pechinimethod and calcined at 900?C for 12 h. The calcined BCZY27 powders were milled in eccentric and in high energy mill with the addition of 2 and 4mol% ZnO as sintering aid. The effects of milling and sintering aids on the sinterability and electrical conductivity were studied. The linear shrinkage in thermomechanical analyses started at 1050?C for the BCZY27 with 4mol% ZnO processed in eccentric mill. Theoretical density above of 90%TD was obtained for the BCZY27 milled with 4mol% ZnO and sintered at 1400?C for 4h. X-ray diffraction analysis of the BCZY27 ceramics sintered at 1400?C confirmed the presence of BaCe0.2Zr0.7Y0.1O3-? and Y0.4Ce0.6O1.8 phases. The incorporation of Zn into perovskite lattice leads to the secondary phase formation. SEM and EDS analyses confirmed the presence of Y0.4Ce0.6O1.8 phase. The sintering was assisted by BaO-ZnO eutectic, which was reflected by the increase of activation energy values for grain boundary conduction. The milling processing did not affect the conductivity properties. The obtained BCZY27 dense sample has conductivity of 7.60 ? 10?3 S/cm at 500?C.

INCREASING THE RESISTANCE OF THE ELECTRONIC COMPONENT BASE TO THE DOSE EFFECTS OF RADIATION EXPOSURE

2021 ◽  
Vol 14 (1) ◽  
pp. 16-22
Author(s):  
Aleksandr Kozyukov ◽  
Konstantin Zolnikov ◽  
Sergey Mescheryakov ◽  
Artem Groshev ◽  
Dmitriy Sysoev
Keyword(s):  
Radiation Exposure ◽  
Technological Process ◽  
Electronic Component ◽  
Transfer Characteristics ◽  
Dose Effects ◽  
Before And After ◽  
Effects Of Radiation ◽  
Process Graphs

The article considers the issues of increasing the resistance of the electronic component base (ECB) to dose effects due to the improvement of the technological process. Graphs of the functions of the transfer characteristics of MOSFETs and CMOS inverters before and after radiation exposure are presented. The effect of the charge in the oxide and on the surface formed under the action of radiation is shown.

Studi Paparan Radiasi pada Pekerja Radiasi Cathlab dengan Menggunakan My Dose Mini sebagai Upaya Keselamatan Radiasi di RSUP Adam Malik Medan

2021 ◽  
Vol 1 (1) ◽  
pp. 41-46
Author(s):  
Martua Damanik ◽  
◽  
Josepa ND Simanjuntak ◽  
Elvita Rahmi Daulay
Keyword(s):  
Radiation Exposure ◽  
Biological Effects ◽  
Exposure Dose ◽  
Radiological Protection ◽  
Safe Level ◽  
Radiation Sources ◽  
Radiation Worker ◽  
Radiation Workers ◽  
Effects Of Radiation ◽  
Radiation Exposure Dose

Cathlab radiation workers, when performing interventional procedures, are at high risk of the effects of radiation exposure. The risk of radiation exposure is deterministic and stochastic biological effects. Therefore, radiation exposure studies of radiation workers at the cath lab were conducted to determine the value of radiation exposure received. This radiation exposure study was conducted by measuring and recording radiation exposure doses received by radiation workers. Measurements are made when the radiation officer performs the intervention procedure. The research was carried out for one month in the cath lab room of the Adam Malik General Hospital, Medan. The modalities used are GE Medical System Interventional Fluoroscopy and Phillips Allura Xper FD20. The dosimeter used is “my dose mini”, which is placed inside a shield or apron worn by radiation workers. The size of the apron shield used is 0.50 mm Pb at the front and 0.25 mm Pb at the rear. Radiation officers whose radiation exposure dose was measured consisted of 10 doctors, 11 nurses, and one radiographer. Each inspection procedure of each radiation worker has a different distance, time, and shield from the radiation source. The measurement of radiation exposure dose is (1-59 μSv) for doctors, (1-58 μSv) for nurses, and 1 μSv for radiographers. To protect against radiation must pay attention to the factors of time, distance, and shielding. Ways that can do are to avoid being close to radiation sources for too long, keep a space at a safe level from radiation, and use shields such as Pb-coated aprons, use Pb gloves, Pb goggles, and thyroid protectors. The amount of radiation exposure dose received by each radiation worker at the time of measurement is still within the tolerance limit. The Nuclear Energy Regulatory Agency (BAPETEN) regulation, which the International Commission recommends on Radiological Protection (ICRP), is 20 mSv/year. The results of this study are expected to be used as input for improving the quality of service for monitoring radiation exposure doses in the Cathlab and as reference material for further research.

Sign in / Sign up

Export Citation Format

Share Document