A case study of management and disposal of TENORMs: radiological risk estimation by TSD Dose and RESRAD-ONSITE

Naturally Occurring Radioactive Materials (NORMs) and Technologically Enhanced NORMs (TENORMs) are among the principal sources of radiation exposure for humans and for the environment. Therefore, the assessment of the impact of NORMs and TENORMs waste on human health is a key issue for their management and for acceptance of disposal sites. The radiological doses to workers and public due to TENORMs disposal depend on the waste inventory, on the usage of the site during operational activities and post closure phase and on the presence of dwelling areas in the vicinity of the disposal site. In the present study it is presented a methodology to preliminary assess the feasibility of a disposal of TENORMs, mainly constituted by phosphate sludges, originated from phosphoric acid industry activities. The hypothetical case study here presented is inspired by a real case study. Different possible scenarios have been considered. The potential doses to workers and to the public on-site have been estimated by the use of the TSD Dose and the RESRAD on-site codes both during the production life cycle of the site and once it ended. Sensitivity analyses were conducted to evaluate the impact of some key parameters, such the coverage thickness and wind velocity, on potential risk for workers and public. </abstract

Pyroprocess Experiments at ENEA Laboratories

A new facility, known as Pyrel III, has been installed at ENEA laboratories for pyrochemical process studies under inactive conditions. It is a pilot plant which allows electrorening and electroreduction experiments to be conducted on simulated fuel. The main component of the plant is a zirconia crucible. The crucible is heated by a furnace which is supported in an externally water-cooled well under the oor of a steel glove-box, where an argon atmosphere is maintained by a continual purge of about 10 L·min-1. The vessel is loaded with LiCl-KCl eutectic salt (59-41 mol%) and is currently operated at 460 °C. Several improvements on Pyrel II (the previous operating plant) have been introduced into Pyrel III. They are described in detail, together with the results from the rst experimental campaign which used lanthanum metal.Moreover, studies about the treatment of chloride salt wastes from pyroprocesses have been conducted in parallel. They follow two main routes: on one hand, a matrix termed sodalite, a naturally occurring mineral containing chlorine, has been synthesized from a mix of nepheline, simulated exhausted salts and glass frit; on the other hand, a novel method proposed by Korea Atomic Energy Research Institute (KAERI) is under assessment. The nal waste forms have been fully characterized with the support of the Politechnique of Milan, by means of density measurements, thermal analysis, and stereomicroscopy observations, FTIR, XRD, and RAMAN spectra, as well as leach tests under static condition

About the Dependence of Breakthrough Curves on Flow Direction in Column Experiments of Transport across a Sharp Interface Separating Different Porous Materials

Conservative transport experiments with layered porous materials (coarse-grained vs. fine-grained) were performed through experimental cylindrical columns to assess the possible occurrence of interface processes at the discontinuity between media with different hydrodynamic and hydrodispersive properties, as proposed by some authors in the past based on modelling and experimental results. The outcomes of the present work show that, under certain conditions, the breakthrough curves (BTCs) obtained for flow through the coarse-grained and then through the fine-grained media (CtF) or vice versa (FtC) can differ. More specifically, an asymmetric behaviour is observed for cases when the ratio between the column and grain diameters is small. Moreover, the discrepancies between CtF and FtC BTCs are enhanced for low flow rates and low quantity of injected solute

Competitive Sorption of Metal Ions from Aqueous Solution onto Sand

none4no32nd Symposium on Scientific Basis for Nuclear Waste Management; St. Petersburg; Russian Federation; 24 May 2009 through 29 May 2009; Code 79940 contributo selezionato e sottoposto a review ISSN: 02729172 ISBN: 978-160511166-7he major part of groundwater contaminants strongly interact with soils and aquifer rocks. Therefore sorption processes on porous matrix are of utmost importance in the frame of the nuclear waste disposal. The objectives of this study were to evaluate sorption uptake by silica sand of some safety-relevant metal ions such as Cs+, Sr2+, Cu2+, Ni 2+ and to investigate the existence of competitive sorption processes between these ions. To this aim, kinetic and equilibrium, mono-component and multi-component, batch experiments were carried out in order to study: i) the influence of metal concentration, pH and contact time, on sorption onto silica sand of the above ions in aqueous solution, and ii) the presence of competition phenomena. Sorption data were well fitted by Langmuir and Freundlich models. Multi-component tests show that the uptake of each ion is reduced in presence of other ions in solution with respect to mono-component batch tests results and that competition between species appears influenced by the equilibrium times of the single species in solution and by pH.noneMorandi, S.; Giacobbo, FRANCESCA CELSA; Mariani, Mario; DA ROS, MirkoS., Morandi; Giacobbo, FRANCESCA CELSA; Mariani, Mario; DA ROS, Mirk

Effect of pH on cation release from sodalite -based matrices for immobilization of spent chloride salt waste from pyroprocessing

The recovering of energy-producing elements such as uranium and plutonium from spent nuclear fuel, which is in line with Generation IV reactors concept, can be performed by pyro-chemical processing. Molten chloride salt waste arising from pyro-processing is one of the problematic wastes for direct application of vitrification or ceramization. Sodalite, a naturally occurring aluminosilicate mineral containing chlorine, is among those mineral phases under consideration as potential matrix for confinement of spent chloride salt waste coming from pyro-processing. In this work, the effect of pH on metal release from sodalite and sodalite blended with borosilicate glass has been evaluated due the lack of data reported in the literature. To this aim, sodalite samples loaded with simulated chloride salts waste, with and without the addition of borosilicate glass, were leached at 90°C for contact times up to 15 days at three different initial values of pH. Leaching results were compared in terms of normalized releases as a function of pH. SEM analyses were also performed in order to compare the matrix surface before and after leaching. According to this study it is apparent that the retention performances of sodalite-based matrices can be significantly worsened under acidic conditions. Therefore it is fundamental to adopt suitable solutions in order to avoid acidic conditions and to preserve the retention capabilities of the sodalite-based confining matrices

Removal of lead (II) from aqueous solutions by adsorption onto activated carbons prepared from coconut shell

In the nuclear field, the availability of effective techniques to eliminate lead pollution from wastewater is of interest both for the purposes of radiation protection from the radioactive isotope lead-210 and also for the issues related to the use of lead in the new generation reactors nowadays under study. Evidences exist of lead pollution due to the radioactive isotope lead-210 in the proximities of uranium extraction mines. In this study, two commercial granular activated carbons obtained by physical activation of coconut shell, specifically developed and selected to purify potable water from dissolved organics (GCN 1240) and for use in gold recovery systems (GCN 816 G), were studied in batch systems to evaluate their effectiveness for separation of lead (II) from aqueous solutions. A characterization of the two carbons, different in particle size, is provided through determination of their pH(PZC) and scanning electron microscope analysis. Adsorption of lead (II) was observed as a function of contact time, and its kinetics were fitted. Adsorption data at equilibrium were fitted by isotherm models and the maximum adsorption capacity of the carbons resulted to be 92.39mg/g (GCN1240) and 32.08mg/g (GCN 816 G). Experiments were carried out to investigate effects of pH on lead adsorption, evidencing that best removal performances of lead occur near pH 5.0. The present study shows that the considered commercial granular activated carbons can be successfully adopted for removal of lead (II) by adsorption from aqueous solutions. Keyword

Leaching behavior of salt wastes conditioned with sodalite blended with two different glass powders

Two different glass powders (a commercially available glass frit and a borosilicate glass) have been used as blending agents for sodalite, an aluminosilicate mineral able to condition chloride salt wastes from pyrometallurgical processes. The synthesis of the mineral phase has been made through a process recently proposed by Idaho National Laboratory in USA, starting from a homogeneous powder of nepheline, chloride salts and glass. The mix, put into an alumina crucible, was introduced in a furnace inside an argon-atmosphere glove-box. The furnace temperature was then raised to 925 C, where it was kept for 7 hours. Leach tests under static conditions, according to ASTM C1285-02, have then been carried out on the final waste forms at room temperature (23 C) and in an oven at 90 C. SEM investigations have also been made before and after leach tests, in order to check the status of the powders. In particular the effect of the leaching process on the surface of the sodalite grains at 90 C from 30 to 150 days has been evidenced. The results obtained in the present study have been usefully compared to those from a similar test on a sodalite added with a glass frit by Idaho National Laboratory. Financial support from the Nuclear Fission Safety Program of the European Union is gratefully acknowledged (project ACSEPT, contract FP7-CP-2007-211 267)

Conditioning of chloride salt wastes from pyroprocesses through the pressureless consolidation process

Sodalite has been taken into account as a matrix for conditioning chloride salt wastes coming from pyroprocesses. The present paper illustrates the research activities finalized to demonstrate the feasibility of sodalite synthesis through the Pressureless Consolidation (PC) process, proposed by Idaho National Laboratories (INL) in USA. A homogeneous powder of nepheline, chloride salts and glass frit was put into an alumina crucible and slightly pressed with another alumina crucible of a smaller diameter, inside which a stainless steel bar had been inserted. The entire assembly was introduced in a furnace inside an Argon-atmosphere glove-box and heated at 925 C for 7 hours. The product obtained has then been characterized by means of density measurements, thermal analysis, stereomicroscopy observations, as well as FTIR and XRD. The latter correspond to the ones of sodalite reported in the spectral library. Leach tests under static conditions according to ASTM C1285-02 (reapproved 2008) have been carried out and successfully compared with those obtained by INL