Retention Properties of Carbide-Corundum Ceramics Containing Carbon-14, Caesium-137, and Strontium-90

2003 ◽  
Author(s):  
Serge A. Dmitriev ◽  
Olga K. Karlina ◽  
Vsevolod L. Klimov ◽  
Micheal I. Ojovan ◽  
Galina Yu. Pavlova ◽  
...  
Keyword(s):  
Xrd Analysis ◽  
Argon Atmosphere ◽  
Use Of Self ◽  
Carbon 14 ◽  
Reactor Graphite ◽  
Strontium 90 ◽  
Exothermic Process ◽  
Reacting Mixtures ◽  
Carry Over ◽  
Experimental Processing

The system C–Al–TiO2 is of considerable interest for the processing of irradiated reactor graphite waste with the retention of biologic hazardous carbon-14. Investigations of this system were conducted both theoretically and experimentally. Previously, the thermodynamic calculations of the phase composition of resulting end product were performed for a wide variety of components content in the system being investigated. These simulation results have been supported by XRD-analysis of produced specimens. The experimental processing of reactor graphite was conducted by the use of self-sustaining reactions in C–Al–TiO2 mixtures. A search of modifier additives was performed to perfect end product properties. Test specimens were produced by mass ranging from 0.2 to 3 kg in the argon atmosphere. Various techniques were applied to characterize the produced specimens. The compressive strength of specimens of doped carbide-corundum matrices synthesized ranged from 7 to 18 MPa. The carry over of Cs-137 and Sr-90 during synthesis reaction was about 3% wt. The leachability attained of Cs-137 and Sr-90 from specimens was around 10−5 g/(cm2.day). The carbon-14 is combined in the end product in chemically and thermic stable titanium carbide. The carry-over of the carbon combined in carbon monoxide from the reacting mixtures during exothermic process was less than 1% wt. This corresponds roughly to up 0.01% wt. of the carbon-14 inventory, which can be present in the irradiated reactor graphite.

Investigation of reactor graphite processing with the carbon-14 retention.

2002 ◽  
Vol 757 ◽  
Author(s):  
M. I. Ojovan ◽  
O. K. Karlina ◽  
V. L. Klimov ◽  
G. A. Bergman ◽  
G. Yu. Pavlova ◽  
...  
Keyword(s):  
Thermodynamic Simulation ◽  
Xrd Analysis ◽  
Carbon 14 ◽  
Reactor Graphite ◽  
Reacting Mixtures ◽  
Strong Candidate ◽  
Run Up ◽  
Carbide Ceramics ◽  
Carry Over ◽  
Experimental Processing

ABSTRACTThe system C – Al – TiO2 has been demonstrated to be a strong candidate for the processing of irradiated reactor graphite waste with the retention of biologic hazardous carbon-14 in chemically and thermal stable corundum-carbide ceramics. The corundum-carbide ceramics is obtained from the powdered precursors blend through self-sustaining thermochemical reactions. Investigations of the system C – Al – TiO2 were carried out both theoretically and experimentally. The refining thermodynamic calculations of the phase composition of resulting end product were performed for a wide variety of components content in the system being investigated. Aluminium oxycarbides production was taken into account in the calculations. Thermodynamic functions of aluminium oxycarbides Al4O4C and Al2OC have been calculated for this purpose using currently available literature evidences and own assessments of missing data. On the basis of thermodynamic simulation the proportions of the source substances were determined, which result in the aluminium oxycarbides production. These simulation results have been supported by XRD-analysis of produced specimens. The experimental processing of reactor graphite was conducted by the use of self-sustaining reactions in C – Al – TiO2 powder blends. Test specimens were produced by mass ranging from 0.1 to 3 kg in the argon atmosphere. Various techniques were used to characterize the produced specimens. The compressive strength of specimens of corundum-carbide matrices produced ranges from 7 to 13 MPa. The leaching rates of Cs-137 and Sr-90 from specimens ranged between 10-4 and 10-5 g/(cm2.day) respectively. The carry-over of the carbon combined in carbon monoxide from the reacting mixtures during exothermic process may run up to 1% wt. that appropriates roughly to less than 0.01% wt. of the carbon-14 in the irradiated reactor graphite.

Immobilization of carbon-14 from reactor graphite waste by use of self-sustaining reaction in the C–Al–TiO2 system

2005 ◽  
Vol 345 (1) ◽  
pp. 84-85 ◽  
Author(s):  
O.K. Karlina ◽  
V.L. Klimov ◽  
M.I. Ojovan ◽  
G.Yu. Pavlova ◽  
S.A. Dmitriev ◽  
...  
Keyword(s):  
Use Of Self ◽  
Carbon 14 ◽  
Reactor Graphite

Model study of atmospheric transport using carbon 14 and strontium 90 as inert tracers

1994 ◽  
Vol 99 (D10) ◽  
pp. 20647 ◽  
Author(s):  
D. E. Kinnison ◽  
H. S. Johnston ◽  
D. J. Wuebbles
Keyword(s):  
Atmospheric Transport ◽  
Carbon 14 ◽  
Model Study ◽  
Strontium 90

scholarly journals Research of Mechanical Properties of Random Disordered CuNi Alloys

2019 ◽  
Vol 8 (12S) ◽  
pp. 276-281
Keyword(s):  
Crystallite Size ◽  
Vacuum Chamber ◽  
Lattice Strain ◽  
Average Crystallite Size ◽  
Xrd Analysis ◽  
Argon Atmosphere ◽  
Oil Refining ◽  
Preparation Technique ◽  
Disordered Alloys ◽  
Peak Broadening

Preparation technique and structural analysis of random CuNi disordered alloys have been discussed. The arcmelting method is used to prepare different compositions of substitutional random disordered Cu1-x Nix (0.1, 0.3, 0.5, 0.7, 0.9) alloys. The stoichiometric amounts of highly purity constituents copper and nickel metals 5 N (99.999%) have been melted under argon atmosphere in vacuum chamber of 10−3 torr. The substitutional random disordered alloys free from carbon and oxygen traces are confirmed from XPS data. A lattice strain is produced in CuNi alloys as the environment of Ni atoms change from sites to sites. Lattice parameters, unit cell volume, structure and inter-planar spacing were calculated from XRD analysis. The average crystallite size of different compositions of random disordered CuNi alloys is calibrated by using Scherer’s method and Williamson-Hall (W-H) method. The roles of crystallite size and lattice strain on the XRD peak broadening of the random disordered CuNi alloys were analyzed. The strain increases with increase in concentration of Ni and exhibits a maximum of 0.00247 at 50% Ni concentration. The CuNi alloys find very wide applications in oil refining and long corrosion free life.

Synthesis of Nickel/Ba-Hexaferrite Magnetic Nano-Composite via Mechanical Alloying Route

2013 ◽  
Vol 829 ◽  
pp. 520-524
Author(s):  
Issa Sobhani ◽  
Abolghasem Ataie ◽  
Mahdiye Ijavi ◽  
Zoya Sadighi
Keyword(s):  
Magnetic Properties ◽  
Milling Time ◽  
Phase Evolution ◽  
Xrd Analysis ◽  
High Energy ◽  
Argon Atmosphere ◽  
Metallic Nickel ◽  
Process Conditions ◽  
Nano Composite ◽  
20 Nm

In this study, nickel and Ba-hexaferrite powders were subjected to high energy mechanical milling in argon atmosphere to produce nickel/Ba-hexaferrite magnetic nanocomposite. Effects of milling time and Ni amount on the phase evolution, morphology and magnetic properties of the products have been investigated by XRD, FESEM/SEM and VSM, respectively. XRD analysis of nanocomposite indicated only Ni peaks after 5 h milling which implied the embedding of Ba-hexaferrite particles inside the metallic nickel. FESEM results revealed that the increasing of the milling time up to 30 h reduced nanocomposite particles size into 20 nm. VSM results showed that the magnetic properties of the nickel/Ba-hexaferrite nanocomposite were affected by the process conditions. The highest saturation magnetization (33.8emu/g) was obtained for the sample containing 30 wt% Ni milled for 20 h Ni series of powder mixture. In addition, it was found that by increasing the milling time coercive field decreases.

scholarly journals An approach to modelling the impact of 14C release from reactor graphite in a geological disposal facility

2015 ◽  
Vol 79 (6) ◽  
pp. 1495-1503 ◽  
Author(s):  
Charalampos Doulgeris ◽  
Paul Humphreys ◽  
Simon Rout
Keyword(s):  
Near Field ◽  
Significant Proportion ◽  
Reactor Core ◽  
Microbial Reduction ◽  
Gaseous Species ◽  
Geological Disposal ◽  
Carbon 14 ◽  
Reactor Graphite ◽  
Disposal Facility ◽  
The Impact

AbstractCarbon-14 (C-14) is a key radionuclide in the assessment of a geological disposal facility (GDF) for radioactive waste. In the UK a significant proportion of the national C-14 inventory is associated with reactor-core graphite generated by the decommissioning of the UK's Magnox and AGR reactors.There are a number of uncertainties associated with the fate and transport of C-14 in a post-closure disposal environment that need to be considered when calculating the radiological impacts of C-14-containing wastes. Some of these uncertainties are associated with the distribution of C-14-containing gaseous species such as 14CH4 and 14CO2 between the groundwater and gaseous release pathways. As part of the C14-BIG programme, a modelling framework has been developed to investigate these uncertainties. This framework consists of a biogeochemical near-field evolution model, incorporating a graphite carbon-14 release model, which interfaces with a geosphere/biosphere model. The model highlights the potential impact of the microbial reduction of 14CO2 to 14CH4, through the oxidation of H2, on C-14 transport. The modelling results could be used to inform the possible segregation of reactor graphite from other gasgenerating wastes.

scholarly journals Preliminary investigation of 14C migration from RBMK-1500 reactor graphite disposed of in a potential geological repository in crystalline rocks in Lithuania

Radiocarbon ◽  
2018 ◽  
Vol 60 (6) ◽  
pp. 1839-1848
Author(s):  
Dalia Grigaliuniene ◽  
Povilas Poskas ◽  
Raimondas Kilda ◽  
Asta Narkuniene
Keyword(s):  
Nuclear Power ◽  
Near Field ◽  
Preliminary Investigation ◽  
Crystalline Rocks ◽  
Near Surface ◽  
Carbon 14 ◽  
Reactor Graphite ◽  
Irradiated Graphite ◽  
Geological Repository ◽  
Order Of Magnitude

ABSTRACTThere are two units with RBMK-1500 type reactors at the Ignalina Nuclear Power Plant (Ignalina NPP) in Lithuania where graphite was used as a neutron moderator and reflector. These reactors are now being decommissioned, and Lithuania has to find a solution for safe irradiated graphite disposal. It cannot be disposed of in a near surface repository due to large amounts of 14C (radiocarbon, carbon-14); thus, a deep geological repository (DGR) is analyzed as an option. This study had the aim to evaluate 14C migration from the RBMK-1500 irradiated graphite disposed of in a potential DGR in crystalline rocks taking into account the outcomes of the research performed under the collaborative European project CAST (CArbon-14 Source Term) and to identify the potential to reduce the conservatism in the assumptions that was introduced in the lack of data and led in the overestimated 14C migration. The information gathered during the CAST project was used to model 14C transport in the near field by the water pathway and to perform uncertainty analysis. The study demonstrated that more realistic assumptions could reduce the estimated 14C flux from the near field by approximately one order of magnitude in comparison with the previous estimations based on very conservative assumptions.

scholarly journals The Simulated Characterization and Suitability of Semiconductor Detectors for Strontium 90 Assay in Groundwater

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 984
Author(s):  
Graeme Turkington ◽  
Kelum A. A. Gamage ◽  
James Graham
Keyword(s):  
Surface Area ◽  
Limit Of Detection ◽  
Semiconductor Detectors ◽  
Point Energy ◽  
Carbon 14 ◽  
Beta Emitters ◽  
Nuclear Decommissioning ◽  
Strontium 90 ◽  
Potassium 40 ◽  
Yttrium 90

This paper examines the potential deployment of a 10 mm × 10 mm × 1 mm cadmium telluride detector for strontium-90 measurement in groundwater boreholes at nuclear decommissioning sites. Geant4 simulation was used to model the deployment of the detector in a borehole monitoring contaminated groundwater. It was found that the detector was sensitive to strontium-90, yttrium-90, caesium-137, and potassium-40 decay, some of the significant beta emitters found at Sellafield. However, the device showed no sensitivity to carbon-14 decay, due to the inability of the weak beta emission to penetrate both the groundwater and the detector shielding. The limit of detection for such a sensor when looking at solely strontium-90 decay was calculated as 323 BqL−1 after a 1-h measurement and 66 BqL−1 after a 24-h measurement. A gallium-arsenide (GaAs) sensor with twice the surface area, but 0.3% of the thickness was modelled for comparison. Using this sensor, sensitivity was increased, such that the limit of detection for strontium-90 was 91 BqL−1 after 1 h and 18 BqL−1 after 24 h. However, this sensor sacrifices the potential to identify the present radionuclides by their end-point energy. Additionally, the feasibility of using flexible detectors based on solar cell designs to maximise the surface area of detectors has been modelled.

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