Radiotoxicity Of Nuclear Waste Research Articles

Approaches to Disposal of Nuclear Waste

We present a concise mini overview on the approaches to the disposal of nuclear waste currently used or deployed. The disposal of nuclear waste is the end point of nuclear waste management (NWM) activities and is the emplacement of waste in an appropriate facility without the intention to retrieve it. The IAEA has developed an internationally accepted classification scheme based on the end points of NWM, which is used as guidance. Retention times needed for safe isolation of waste radionuclides are estimated based on the radiotoxicity of nuclear waste. Disposal facilities usually rely on a multi-barrier defence system to isolate the waste from the biosphere, which comprises the natural geological barrier and the engineered barrier system. Disposal facilities could be of a trench type, vaults, tunnels, shafts, boreholes, or mined repositories. A graded approach relates the depth of the disposal facilities’ location with the level of hazard. Disposal practices demonstrate the reliability of nuclear waste disposal with minimal expected impacts on the environment and humans.

The Issue of Accelerator Beam Trips for Efficient ADS Operation

The development of accelerator-driven systems (ADSs) is motivated by the potential of these machines to reduce the volume and the radiotoxicity of accumulated nuclear waste, more particularly that of minor actinides currently generated by the operation of existing pressurized water reactors. The reduction of both volume and radiotoxicity of nuclear waste is achieved by transmutation and fission of minor actinides into less-active isotopes or shorter-lived by-products.Various technical challenges exist regarding designing reliable and efficient ADSs. The key points are very much linked to the design of the spallation module, the assurance that reactivity remains below criticality under any circumstances, and the accelerator reliability.This paper addresses the latter two challenges imposed on the accelerator in order to assure safe and reliable ADS operation. It discusses the possibility of performing online absolute reactivity measurements and the limits in the number of allowable accelerator beam trips, which might impede plant integrity and/or plant efficiency.

Synthesis and Evaluation of Lipophilic BTBP Ligands for An/Ln Separation in Nuclear Waste Treatment: The Effect of Alkyl Substitution on Extraction Properties and Implications for Ligand Design (Eur. J. Org. Chem. 8/2012)

AbstractThe cover picture shows four radiochemical gloveboxes used for working with plutonium and other α‐active radioactive materials as the background image. The gloveboxes contain centrifugal contactors and mixer‐settler rigs for use in laboratory‐scale solvent extraction, actinide oxide dissolution and aqueous actinide chemistry and spectroscopy. The picture is courtesy of Dr. Robin Taylor, National Nuclear Laboratory, Sellafield, Seascale, Cumbria CA20 1PG, UK. The foreground represents the selective extraction of AmIII over EuIII by new 6,6′‐bis(triazinyl)‐2,2′‐bipyridine (BTBP) ligands, a family of ligands currently under study for the separation of actinides from lanthanides in a proposed future selective actinide extraction (SANEX) process. This separation is foreseen as an important step in reducing the long‐term radiotoxicity of nuclear waste. Details are discussed in the article by F. W. Lewis, L. M. Harwood et al. on p. 1509 ff. magnified image

Recycling the Actinides, The Cornerstone of Any Sustainable Nuclear Fuel Cycles

The sustainability of the current nuclear fuel cycles is not completely achieved since they do not optimise the consumption of natural resource (only a very small part of uranium is burnt) and they do not ensure a complete and efficient recycling of the potential energetic material like the actinides. Promoting nuclear energy as a future energy source requires proposing new nuclear systems that could meet the criteria of sustainability in terms of durability, bearability and liveability. In particular, it requires shifting towards more efficient fuel cycles, in which natural resources are saved, nuclear waste are minimised, efficiently confined and safely disposed of, in which safety and proliferation-resistance are more than ever ensured. Such evolution will require (i) as a mandatory step, evolutionary recycling of the major actinides U and Pu up to their optimized use as energetic materials using fast neutron spectra, (ii) as an optional step, the implementation of the recycling of minor actinides which are the main contributors to the long term heat power and radiotoxicity of nuclear waste. Both options will require fast neutrons reactors to ensure an efficient consumption of actinides. In such a context, the back-end of the fuel cycle will be significantly modified: implementation of advanced treatment/recycling processes, minor-actinides recovery and transmutation, production of lighter final waste requiring lower repository space. In view of the 2012 French milestones in the framework of the 2006 Waste Management Act, this paper will depict the current state of development with regards with these perspectives and will enlighten the consequences for the subsequent nuclear waste management.

Transmutation and the Global Nuclear Energy Partnership

AbstractIn the January 2006 State of the Union address, President Bush announced a new Advanced Energy Initiative, a significant part of which is the Global Nuclear Energy Initiative. Its details were described on February 6, 2006 by the U.S. Secretary of Energy. In summary, it has three parts: (1) a program to expand nuclear energy use domestically and in foreign countries to support economic growth while reducing the release of greenhouse gases such as carbon dioxide. (2) an expansion of the U.S. nuclear infrastructure that will lead to the recycling of spent fuel and a closed fuel cycle and, through transmutation, a reduction in the quantity and radiotoxicity of nuclear waste and its proliferation concerns, and (3) a partnership with other fuel cycle nations to support nuclear power in additional nations by providing small nuclear power plants and leased fuel with the provision that the resulting spent fuel would be returned by the lessee to the lessor. The final part would have the effect of stabilizing the number of fuel cycle countries with attendant non-proliferation value. Details will be given later in the paper.

Concept of a small-scale electron accelerator driven system for nuclear waste transmutation: Part 2. Investigation of burnup

In our earlier paper the target optimization of an electron–neutron (e–n) converter based molten salt ADS concept (MSENC) was presented. In this paper the burnup in this molten salt ADS is investigated. The system is continuously fueled with TRUs obtained from spent nuclear fuel by means of pyrochemical separation, while fission products are continuously filtered out. Effect of MSENC operation on transuranium consumption, mass reduction and radiotoxicity is considered. It seems that while the amount of plutonium is reduced significantly, the higher actinides will build up, which results that radiotoxicity of nuclear waste will not be reduced considerably.

Enhancement of Transmutation Characteristics of the Minor Actinide Burning Fast Reactor Core Concept Using Hydride Fuel Targets and Its Introduction Scenario

Transmutation characteristics of the minor actinide (MA) burning fast reactor core using hydride fuel targets are enhanced to reduce long-term radiotoxicity of nuclear waste. A scenario which introduces the concept is investigated. (1) The MA burner core with plutonium (Pu) multi-recycling can transmute a large amount of MAs; the amount is about that produced in 21 LWRs per year. The targets are shuffled after the 1-year irradiated in the core region and further irradiated for 2 years in the radial blanket region. (2) The MA once-through core can incinerate almost all of the MAs in targets by fission during a 6-year irradiation in the core region. (3) Introduction of the MA burner core for all fast reactors (FRs) after the year of 2020 allows the following scenario. The residual amount of MAs from LWR spent fuel can be held to zero within the 21st century and all FRs will be changed to the self-generated MA transmutation core without the targets. When the MA once-through cores are introduced with MA burner cores, the total number of targets to be reprocessed can be reduced by 50%. (4) Even in the low projection case while the MA burner cores are installed after conventional FRs, MA accumulation would also be held to zero within the 21st century.

REMOVAL OF 243Am WITH PHENOL BASED RESINS

Long-term radiotoxicity of nuclear waste produced during spent nuclear fuel reprocessing could be reduced if the minor actinides (neptunium, americium and curium) contained within the waste are separated into short-lived radionuclides for their subsequent transmutation or for separate storage. Cross-linked phenolic resins based on different substituted phenol were shown to be very efficient for selective uptake of Eu3+ from aqueous solutions containing equal amounts of La3+. In this work, we have prepared and characterized cross-linked phenol based resins to investigate the uptake of 243Am. According to the results obtained for Eu selective extraction and to enhance 243Am sorption, the resins are transformed into their Na+–forms before extraction. The ion selectivities of the cross-linked phenol based resins are then compared as a function of the identity of the ion-exchange phenolic matrix. Radiation stability of the resins was studied and each resin was measured for the effect of ionizing radiations with FTIR spectroscopy, moisture regain and ion exchange capacity.

Fast Reactor Core Concepts for Minor Actinide Transmutation Using Hydride Fuel Targets

Fast reactor core concepts are studied which reduce long-term radiotoxicity of nuclear waste by using minor actinides (MAs) in the form of zirconium-hydride fuel targets. A systematic parameter survey is carried out to investigate the fundamental characteristics of MA transmutation and the core safety parameters such as sodium void reactivity in a 1,000 MWe-class fast reactor core. Two core concepts are proposed, using 36 target assemblies, by adjusting the composition of hydride fuels. One is the MA burner core to transmute a large amount of MAs in a short time combined with Pu multi-recycling in fast reactors, whereby the MAs produced in about 13 LWRs can be transmuted every year with a 58% MA transmutation rate in discharged targets. The other is the MA once-through core to incinerate a small amount of MAs by fission, whereby the MAs produced in about 2 LWRs can be incinerated every year with a 64% MA incineration rate (a 93% transmutation rate) in discharged targets. This study shows these concepts have great potential to achieve good transmutation characteristics of MAs while providing the improved safety characteristics of a fast reactor core.