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 14C leaching and speciation studies on Irradiated graphite from vandellós I Nuclear Power Plant

Radiocarbon ◽  
2018 ◽  
Vol 60 (6) ◽  
pp. 1871-1881
Author(s):  
Enrique Magro ◽  
Eva María Márquez ◽  
Gabriel Piña ◽  
Marina Rodríguez ◽  
José Luís Gascón ◽  
...  
Keyword(s):  
Nuclear Power ◽  
High Efficiency ◽  
Pure Water ◽  
Management Strategies ◽  
Near Surface ◽  
Carbon 14 ◽  
Irradiated Graphite ◽  
Water Media ◽  
High Concentrations ◽  
Eu Project

ABSTRACTThe understanding of the 14C behavior in waste packages could lead, in the Spanish context, to a revision of the management strategies for radioactive waste and a revaluation of the near surface repository devoted to the disposal of waste containing this radionuclide in high concentrations. To achieve this objective, and in the context of the EU project Carbon-14 Source Term (CAST), the authors of the work presented in this paper have performed leaching experiments with irradiated graphite considering two different scenarios. One, in which the leaching solution simulates some of the expected conditions in a repository where a granite/bentonite mixture has been used as backfill material, and the other, using deionized water as a high efficiency chemical removal agent and for comparison purposes. The analytical approach to measure the release rate and speciation of 14C from irradiated graphite samples in the aqueous and gaseous phase is also described. The main results obtained shows that, after 359 days of leaching, no 14C activity was detected above the detection limits, and only leaching rates regarding beta-gamma emitters were observed: 2×10–6 cm/day for 137Cs and 1×10–5 cm/day for 60Co in granite/bentonite water media and 4×10–6 cm/day for 137Cs in pure water.

Radiocarbon measurements in cemented ion-exchange resins

2012 ◽  
Vol 1475 ◽  
Author(s):  
Stasys Motiejunas ◽  
Algirdas Vaidotas ◽  
Jonas Mazeika ◽  
Zana Skuratovic ◽  
Violeta Vaitkeviciene
Keyword(s):  
Ion Exchange ◽  
Nuclear Power ◽  
Inorganic Compounds ◽  
Liquid Radioactive Waste ◽  
Ion Exchange Resins ◽  
Near Surface ◽  
Solidified Waste ◽  
Order Of Magnitude ◽  
Exchange Resins

ABSTRACTA large amount of liquid radioactive waste has been generated at the Ignalina Nuclear Power Plant (NPP), Lithuania, during its operation. The contaminated liquids are treated with ion exchange-resins, which will generate significant waste stream for cementation. The cemented waste will be disposed of in a near-surface repository. The preliminary safety assessment uncovered that 14C is the most significant radionuclide affecting long-term safety of the closed repository. The method of combined acid striping and wet oxidation with subsequent catalytic combustion has been applied for 14C measurements in cemented ion-exchange resins. It allows separating organic and inorganic compounds from the same sample. At first, the inorganic fraction was extracted by adding acid to the sample followed by absorption of CO2 in a pair of alkali gas washed traps. The remaining carbon was extracted by application of a strong oxidizer. The preliminary results show that activity concentration of 14C in the solidified waste has an order of magnitude of tens and hundreds Bq per gram.

Modeling of irradiated graphite 14C transfer through engineered barriers of a generic geological repository in crystalline rocks

2016 ◽  
Vol 569-570 ◽  
pp. 1126-1135 ◽  
Author(s):  
Povilas Poskas ◽  
Dalia Grigaliuniene ◽  
Asta Narkuniene ◽  
Raimondas Kilda ◽  
Darius Justinavicius
Keyword(s):  
Crystalline Rocks ◽  
Irradiated Graphite ◽  
Geological Repository ◽  
Engineered Barriers

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.

Modeling of Radionuclide Releases From the Geological Repository for RBMK-1500 Spent Nuclear Fuel in Crystalline Rocks in Lithuania

2007 ◽  
Author(s):  
Povilas Poskas ◽  
Asta Brazauskaite
Keyword(s):  
Nuclear Fuel ◽  
Safety Assessment ◽  
Spent Nuclear Fuel ◽  
Near Field ◽  
Crystalline Rocks ◽  
Far Field ◽  
Field Region ◽  
Radionuclide Migration ◽  
Channel Network ◽  
Geological Repository

During 2002–2005 the assessment of possibilities for disposal of spent nuclear fuel (SNF) in Lithuania was performed with support of Swedish experts. Potential geological formations for disposal of SNF were selected, disposal concept was developed, reference disposal site was defined and preliminary generic safety assessment was performed. Performing safety assessment the analysis of radionuclides migration from the repository as well as their impact to human and environment were also very important issues. In this paper results on the analysis of the radionuclide releases from the reference geological repository site for RBMK-1500 SNF in crystalline rocks in Lithuania are presented. For radionuclide migration in the near field region of the repository integrated finite difference method and the concept of compartments were used. For radionuclide migration in the far field the discrete channel network concept was used. The assessment of radionuclide migration in the near and far field region was performed using computer codes AMRER4.5 [1] and CHAN3D [2]. The results of analysis show that most of safety relevant radionuclides of RBMK-1500 SNF are effectively retarded in the near field region. The exposure due to possible release of the radionuclides from the crystalline rocks would be dominated by 129I firstly while after app. 250 thousand years 226Ra is dominating already.

Near-field scanning optical microscopy

1986 ◽  
Vol 44 ◽  
pp. 642-643
Author(s):  
E. Betzig ◽  
A. Harootunian ◽  
M. Isaacson ◽  
A. Lewis
Keyword(s):  
Near Field ◽  
Optical Microscope ◽  
Visible Radiation ◽  
Field Methods ◽  
Optical Elements ◽  
Optical Region ◽  
Order Of Magnitude ◽  
Nondestructive Imaging ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

The Effects of Ion Implantation on the Surface Features of Inconel 600

1985 ◽  
Vol 43 ◽  
pp. 288-289
Author(s):  
John D. Rubio
Keyword(s):  
Grain Boundary ◽  
Ion Implantation ◽  
Nuclear Power ◽  
Power Plants ◽  
Surface Region ◽  
Selective Dissolution ◽  
Boundary Region ◽  
Near Surface ◽  
Inconel 600 ◽  
Steam Generator Tubing

The degradation of steam generator tubing at nuclear power plants has become an important problem for the electric utilities generating nuclear power. The material used for the tubing, Inconel 600, has been found to be succeptible to intergranular attack (IGA). IGA is the selective dissolution of material along its grain boundaries. The author believes that the sensitivity of Inconel 600 to IGA can be minimized by homogenizing the near-surface region using ion implantation. The collisions between the implanted ions and the atoms in the grain boundary region would displace the atoms and thus effectively smear the grain boundary.To determine the validity of this hypothesis, an Inconel 600 sample was implanted with 100kV N2+ ions to a dose of 1x1016 ions/cm2 and electrolytically etched in a 5% Nital solution at 5V for 20 seconds. The etched sample was then examined using a JEOL JSM25S scanning electron microscope.

scholarly journals Near-surface real-time seismic imaging using parsimonious interferometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sherif M. Hanafy ◽  
Hussein Hoteit ◽  
Jing Li ◽  
Gerard T. Schuster
Keyword(s):  
Fluid Flow ◽  
Real Time ◽  
Temporal Resolution ◽  
Seismic Imaging ◽  
Time Lapse ◽  
Rock Properties ◽  
Recording Time ◽  
Near Surface ◽  
Arrival Times ◽  
Order Of Magnitude

AbstractResults are presented for real-time seismic imaging of subsurface fluid flow by parsimonious refraction and surface-wave interferometry. Each subsurface velocity image inverted from time-lapse seismic data only requires several minutes of recording time, which is less than the time-scale of the fluid-induced changes in the rock properties. In this sense this is real-time imaging. The images are P-velocity tomograms inverted from the first-arrival times and the S-velocity tomograms inverted from dispersion curves. Compared to conventional seismic imaging, parsimonious interferometry reduces the recording time and increases the temporal resolution of time-lapse seismic images by more than an order-of-magnitude. In our seismic experiment, we recorded 90 sparse data sets over 4.5 h while injecting 12-tons of water into a sand dune. Results show that the percolation of water is mostly along layered boundaries down to a depth of a few meters, which is consistent with our 3D computational fluid flow simulations and laboratory experiments. The significance of parsimonious interferometry is that it provides more than an order-of-magnitude increase of temporal resolution in time-lapse seismic imaging. We believe that real-time seismic imaging will have important applications for non-destructive characterization in environmental, biomedical, and subsurface imaging.

Heat Transfer Spectroscopy and “Heat Transfer-Distance” Curves

2008 ◽  
Author(s):  
Arvind Narayanaswamy ◽  
Sheng Shen ◽  
Gang Chen
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Atomic Force Microscope ◽  
Near Field ◽  
Surface Force ◽  
Casimir Forces ◽  
Distance Curve ◽  
Transfer Distance ◽  
Atomic Force ◽  
Order Of Magnitude

Thermal radiative transfer between objects as well as near-field forces such as van der Waals or Casimir forces have their origins in the fluctuations of the electrodynamic field. Near-field radiative transfer between two objects can be enhanced by a few order of magnitude compared to the far-field radiative transfer that can be described by Planck’s theory of blackbody radiation and Kirchoff’s laws. Despite this common origin, experimental techniques of measuring near-field forces (using the surface force apparatus and the atomic force microscope) are more sophisticated than techniques of measuring near-field radiative transfer. In this work, we present an ultra-sensitive experimental technique of measuring near-field using a bi-material atomic force microscope cantilever as the thermal sensor. Just as measurements of near-field forces results in a “force distance curve”, measurement of near-field radiative transfer results in a “heat transfer-distance” curve. Results from the measurement of near-field radiative transfer will be presented.

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