Stability under γ irradiation aging of an EPOXY/AMINE resin embedding simulated nuclear waste: Critical assessment of the techniques investigating chemical structure (IR and SIM spectroscopies) and bulk properties (DMA,DSC)

In order to predict the long term behaviour of materials simulating embedded nuclear waste (concentrate of evaporated radioactive effluents, mixture of anionic and cationic exchange resin), several techniques have been used:

• — Infrared and HSF-SIMS spectroscopies to investigate chemical structure: no significant differences have been observed between irradiated epoxy resin matrix samples and non-irradiated ones. No structural modification in the materials have been evidenced but some ion exchange resin irradiated in water seem to trap chlorine while releasing their borate content.
• — Dynamic mechanical analysis (DMA) to follow the irradiation effect on relaxational mechanisms. A small increase of the temperature T_α associated with the glass transition temperature for a weak total dose whereas a decrease of T_α for greater doses have been detected (these variations are however close to measurement errors).
• — Differential scanning calorimetry (DSC) to follow the thermal behaviour of the γ irradiated simulated radioactive materials: DSC results agree with those obtained using DMA.

     

Investigation of the stability of glass-ceramic composites containing CeTi2O6 and CaZrTi2O7 after ion implantation

Glass-ceramic composite materials have been investigated for nuclear waste sequestration applications due to their ability to incorporate large amounts of radioactive waste elements. A key property that needs to be understood when developing nuclear waste sequestration materials is how the structure of the material responds to radioactive decay of nuclear waste elements, which can be simulated by high energy ion implantation. Borosilicate glass-ceramic composites containing brannerite-type (CeTi₂O₆) or zirconolite-type (CaZrTi₂O₇) oxides were synthesized at different annealing temperatures and investigated after being implanted with high-energy Au ions to mimic radiation induced structural damage. Backscattered electron (BSE) images were collected to investigate the interaction of the brannerite crystallites with the glass matrix before and after implantation and showed that the morphology of the crystallites in the composite materials were not affected by radiation damage. Surface sensitive Ti K-edge glancing angle XANES spectra collected from the implanted composite materials showed that the structures of the CeTi₂O₆ and CaZrTi₂O₇ ceramics were damaged as a result of implantation; however, analysis of Si L_2,3-edge XANES spectra indicated that the glass matrix was not affected by ion implantation.     

Preparation of radiochemically pure radionuclides145Sm,152+154Eu and169Yb

The separation of radioactive impurities from the original radioactive material allows to achieve a higher precision of nuclear characteristic measurements of radioactive standards. The different ability of lanthanoides to form amalgams has been used for the separation of¹⁴⁵Sm,^152+154Eu and¹⁶⁹Yb from radioactive impurities. The optimum conditions for electrolysis on mercury electrode followed by the sorption on cellulose powder used for the preparation of weightless standards have been described.     

Effect of container adsorption on the210Pb/210Bi secular equilibrium relationship in spiked aqueous solutions

The radioactive boric acid wastes generated from the nuclear power plants have been solidified with cement. One of the properties required for solidified radioactive wastes is resistance to leaching. The leachability of¹³⁷Cs from solidified waste specimens prepared by various formulation has been studied according to the proposed ANS 16.1 Standard Leach Test. For the evaluation of radiological safety in the solidified radioactive waste disposal, the leachability indices have been determined from the leaching test data. The results have turned out to be 5.97–7.60, depending on formulation and solidifying matrix.     

Processing of data from a global atmospheric radioactivity monitoring network for CTBT verification purposes

Summary Finland has the operational capability to take airborne gamma-ray measurements in emergency situations. The original purpose of airborne radiation mapping in Finland was to identify hazardous areas containing radioactive fall-out after a nuclear accident or use of nuclear weapons. Regular exercises are held annually to keep the operational functionality at a high level. The achieved capability has been well demonstrated in international INEX-2-FIN 1997 and Barents Rescue 2001 exercises. The knowledge and competence achieved can easily be applied in international radiation monitoring campaigns designed to expose undeclared nuclear materials or other clandestine nuclear activities. The essential improvements in the detection system are linked to the ability to locate point-like radiation sources rather than large areas of fall-out. This paper describes the aerial gamma-ray measurement method and its usability for the detection of nuclear material production chains and trails of fission or activation products. The ability of airborne detection systems in revealing the use of undeclared nuclear materials has been tested. Various scenarios for exposing clandestine nuclear material production, enrichment and nuclear waste trails have been considered. Based on detection capability calculations and testing in practice, it was found that the detection of one un-shielded significant quantity of natural uranium (10 tons of yellow cake in storage barrels) is possible through the daughter products, using one single 6"'4" NaI detector on the airplane. The developed fixed wing gamma measurement technique is now able to detect significant amounts of nuclear material conveniently and cost-effectively. Large areas can be screened to identify suspicious sub-areas for more detailed ground-based inspection.     

Radioactivity in monitoring materials processing

Monitoring of the concentration of actinides in process streams and waste materials can be effectively carried out by detecting and measuring their radioactive emissions. Such monitoring techniques lead to more efficient control of the process, and also aid in the minimisation of losses to the waste and better accounting of the nuclear materials. This paper provides an overview of some of the techniques such as on-line alpha monitoring, passive and active neutron assay and gamma counting, and also describes the monitoring systems which have been developed in our laboratory for use in a reprocessing plant.     

The possible discovery of neutron activation in 1910

One-hundred-two years ago, on 21 April 1910, the Austrian chemist Carl Auer von Welsbach published a short comment on a fundamental discovery he had made in the field of nuclear sciences. He reported that “jonium” (²³⁰Th) was able to induce radioactivity in other materials if stored in contact with the ionium sample. He was well aware that this observation was “not quite in agreement with current theories”, because, as a basic principle, a radioactive substance cannot activate an inactive substance. Since he could not remove any superficial contamination, he concluded that the previously inactive materials had become radioactive themselves. Auer von Welsbach predicted that this observation “might be of importance for the mysterious field of radioactivity research”. In fact, we believe that in this experiment he incidentally discovered neutron activation and the production of artificial radionuclides (24 years before I. Curie and F. Joliot) or even induced nuclear fission. The neutron source in his experiments is yet unknown and shall be identified in this project. The neutrons could have been produced from nuclear reactions with impurities of beryllium in the sample. Auer von Welsbach may even have observed nuclear fission 29 years before O. Hahn, F. Straßmann, L. Meitner and O. R. Frisch. In any case, he may have noticed the effects of neutron radiation—22 years before its discovery by J. Chadwick. The main aim of this interdisciplinary project (of which preliminary results are presented herein) is to repeat the 1910-experiment and to identify the source of the neutrons. It will be equally important to investigate the historical reasons and circumstances why Auer’s report remained mostly uncommented in the scientific community. The hypothetical consequences are worth discussion: Auer’s publication could have started the “nuclear age” much earlier than it finally began, with all the consequences for mankind.     

A Novel Vanadosilicate with Hexadeca‐Coordinated Cs+ Ions as a Highly Effective Cs+ Remover

The effective removal of ¹³⁷Cs⁺ ions from contaminated groundwater and seawater and from radioactive nuclear waste solutions is crucial for public health and for the continuous operation of nuclear power plants. Various ¹³⁷Cs⁺ removers have been developed, but more effective ¹³⁷Cs⁺ removers are still needed. A novel microporous vanadosilicate with mixed‐valence vanadium (V⁴⁺ and V⁵⁺) ions is now reported, which shows an excellent ability for Cs⁺ capture and immobilization from groundwater, seawater, and nuclear waste solutions. This material is superior to other known materials in terms of selectivity, capacity, and kinetics, and at very low Cs⁺ concentrations, it was found to be the most effective material for the removal of radioactive Cs⁺ ions under the test conditions. This novel vanadosilicate also contains hexadeca‐coordinated Cs⁺ ions, which corresponds to the highest coordination number ever described.     

Uranium leaching using mixed organic acids produced by Aspergillus niger

Source term information is required for to reconstruct a device used in a dispersed radiological dispersal device. Simulating a radioactive environment to train and exercise sampling and sample characterization methods with suitable sample materials is a continued challenge. The Idaho National Laboratory has developed and permitted a radioactive response training range (RRTR), an 800 acre test range that is approved for open air dispersal of activated KBr, for training first responders in the entry and exit from radioactively contaminated areas, and testing protocols for environmental sampling and field characterization. Members from the Department of Defense, Law Enforcement, and the Department of Energy participated in the first contamination exercise that was conducted at the RRTR in the July 2011. The range was contaminated using a short lived radioactive ⁸²Br isotope (activated KBr). Soil samples contaminated with KBr (dispersed as a solution) and glass particles containing activated potassium bromide that emulated dispersed radioactive materials (such as ceramic-based sealed source materials) were collected to assess environmental sampling and characterization techniques. This presentation summarizes the performance of a radioactive materials surrogate for use as a training aide for nuclear forensics.     

Development of prototype titanate ion-exchange loaded-membranes for strontium, cesium and actinide decontamination from aqueous media

We have successfully incorporated high surface area particles of titanate ion-exchange materials (monosodium titanate and crystalline silicotitanate) into porous and inert support membrane fibrils. The resulting membrane sheets were used to evaluate the removal of surrogate radioactive materials for cesium-137 and strontium-90 from high caustic nuclear waste simulants. The membrane supports met the nominal requirement for non-chemical interaction with the embedded ion-exchange materials and were porous enough to allow sufficient liquid flow. Most of the stamped out 47-mm size titanium impregnated ion-exchange membrane discs removed more than 96% of dissolved cesium-133 and strontium-88 from caustic nuclear waste salt simulants.     

Waste cigarette filters: activated carbon as a novel sorbent for uranium removal

Uranium is important in the nuclear fuel cycle as both as an energy source and as radioactive waste. Herein, activated carbon (AC) prepared from waste cigarette filters by convenient carbonization and functionalization was chosen as the raw materials for radionuclides adsorption. Batch adsorption experiments showed that AC presented comparable UO₂²⁺ adsorption capacity (106 mg g^?1) and very outstanding selectivity. The adsorption process accorded with Langmuir model and the pseudo-second-order kinetics model well. This work combines the waste cigarette filters with the radioactive nuclear treatment materials, which may provide a new strategy for the future treatment of waste cigarette butts.

     

Environmental monitoring program around Rokkasho nuclear fuel cycle facilities

Three commercial nuclear fuel cycle facilities, a reprocessing plant, an uranium enrichment plant and a low level radioactive waste disposal center, have been constructed or are in partial operation at Rokkasho-mura in Aomori prefecture, about 700 km north of Tokyo. A monitoring program has been settled on the modulation between Japan Nuclear Fuel Ltd. (JNFL) and Aomori Prefectural Govemment. The basic goal of environmental monitoring is to make sure that the dose equivalent received by the public, living around the facilities, is much lower than the annual dose equivalent limit. The target is as follows: (1) to estimate the dose equivalent received by the public, (2) to understand the accumulation of radioactive materials in the environment and (3) to estimate the influence on the environment due to unexpected release from the nuclear facilities and to make judgement for the enforcement of routine monitoring or not. This paper describes the contents of the monitoring program such as the object of nuclides, measuring/sampling point, kinds of samples etc.     

Distribution coefficients for <Superscript>85</Superscript>Sr and <Superscript>137</Superscript>Cs in Japanese agricultural soils and their correlations with soil properties

The performance of several commercially available portable radiation spectrometers containing small NaI(Tl) scintillation detectors has been studied. These devices are used by field inspection personnel to detect and identify illicit radioactive materials. The detection and identification of enriched uranium is an important deterrent to undeclared nuclear proliferation and nuclear terrorism. This study was conducted using a variety of shielded and unshielded uranium sources in a simulated maritime environment. The results indicate adequate identification capability for various uranium enrichments using the manufacturer’s spectral analysis firmware. More sophisticated methods for analyzing the spectra can be applied to these short field measurements to determine the isotopic enrichment.     

Experimental and theoretical insights into copper phthalocyanine-based covalent organic frameworks for highly efficient radioactive iodine capture

Exploring efficient materials for capturing radioactive iodine in nuclear waste is of great significance for the progress of nuclear energy as well as the protection of ecological environment. Covalent organic frameworks (COFs) have emerged as promising adsorbents because of their predesignable and functionalizable skeleton structures. However, it remains a grand challenge to achieve large scale preparation of COFs. In this work, we developed a mild and efficient microwave irradiation method instead of the traditional solvothermal method to prepare copper phthalocyanine-based covalent organic frameworks (Cu_xPc-COFs) within only 15 min. The nitrogen-rich 1,2,4,5-tetracarbonitrilebenzene (TCNB) was selected as the solely organic ligand to construct copper phthalocyanine-based 2D conjugated COFs. The resultant Cu_xPc-COFs exhibited excellent iodine enrichment with 2.99 g/g for volatile iodine and 492.27 mg/g for iodine-cyclohexane solution, respectively, outperforming that of many porous materials. As indicated by spectroscopic analysis and DFT calculations, this impressive adsorption performance can be attributed to the charge transfer arising from nitrogen-rich phthalocyanine structures and electron-rich π-conjugated systems with iodine molecules. Moreover, the strong electrostatic interaction between Cu(II) on chelate centers and polyiodide anions (I_x^?) also play an important role in the firmly trapping radioactive iodine. Therefore, this study provides a facile and intelligent approach to implement metal-based COFs for the remediation of toxic radioactive iodine.     

Uranium and plutonium containing particles in a sea sediment sample from Thule, Greenland

Particles composed of radioactive materials and probably originating from US nuclear weapons were identified in sea sediment samples collected from Thule, Greenland, in 1997. The weapons were destroyed close to the Thule Air Base in 1968 in an aeroplane crash, which dispersed radioactive materials in the environment. The presence of particulate radioactive materials in the sediment samples was revealed by combining gamma-spectrometry and autoradiography. Isolation and separation of a radioactive particle from a bulk sample were performed using autoradiography, phosphor plate imaging and scanning electron microscopy. Using X-ray microanalysis as well as alpha and beta activity analysis, U and weapons-grade Pu were detected in the granular, brittle particle.     

Decontamination of some radioactive effluents by means of ceramic filters

The paper deals with the use of some ceramic materials for the removal of⁵⁵⁺⁵⁹Fe³⁺ and⁶⁰Co²⁺ ions from residual waters. For this purpose, chamotte powder has been used both by itself or in a mixture with aluminium oxide. The pastes obtained by wetting these materials have been shaped in the form of crucibles. The radioactive ions which exist in residual effluents, have been retained to a large extent on these filters. Separately, the leaching of radioactive ions previously retained on the filtering mass, has been studied under the influence of water and of diluted solutions of hydrochloric acid or sodium chloride.     

Neutron activation analysis of concrete for cross-border nuclear security

The dissolution of the Soviet Union coupled with the growing sophistication of international terror organizations has brought about a desire to ensure that a sound infrastructure exists to interdict smuggled nuclear material prior to leaving its country of origin. To combat the threat of nuclear trafficking, radiation portal monitors (RPMs) are deployed around the world to intercept illicit material while in transit by passively detecting gamma and neutron radiation. Portal monitors in some locations have reported abnormally high background counts. The higher background data has been attributed, in part, to the naturally occurring radioactive materials (NORM) in the concrete surrounding the portal monitors. Higher background increases the minimum detectable activity (MDA) and can ultimately lead to more material passing through the RPMs undetected. This work employed two different neutron activation analysis (NAA) methods for the purpose of developing a process to characterize the concrete surrounding the RPMs. Thermal neutron instrumental NAA (INAA) and fast NAA (FNAA) were conducted on six samples from three different composition concrete slabs. Comparator standards and quality control materials were used to help ensure that the methods were both precise and accurate. The combination of INAA and FNAA accounted for 84–100% of the total elemental composition of the samples. Knowing the composition of the concrete will allow RPM customers to choose suitable materials prior to installation, thereby increasing the ability of the monitors to detect radiological and nuclear materials.     

Radioactive beams — A new application of radioanalytical chemistry

An emerging, exciting area of nuclear science is the use of radioactive nuclear beams to study chemical and physical phenomena. One uses the radioactive products (ms<t_1/2<y) of nuclear reactions induced by charged particles or nuetrons to induce secondary reactions or to act as radiotracers. The use of such beams enhances the tools of the radioanalytical chemist. Applications of such beams in materials science (where the beams act as tracers), and the synthesis of new nuclei (especially with Z104) are described.     

Status of sol–gel process for nuclear fuels

Sol–gel process provides an alternate route for fabrication of ceramic nuclear fuel. The sol–gel process provides several advantages over the conventional powder pellet fabrication process by eliminating handling of radioactive powders. The sol–gel process uses only fluids or fluid like materials, thus become amenable to remote handling. The sol–gel process has been developed for the production of coated particle fuels for High Temperature Gas Cooled Reactors (HTGRs), as sphere-pac fuel for Fast Breeder Reactors (FBRs) and as SGMP fuel for Thermal Reactors. Internal Gelation Process is one of the most important routes of the sol–gel process and has been accepted as the most promising process route globally. Several countries having plutonium or ²³³U based fuel program have developed sol–gel process for nuclear fuels. In India there is special interest for the development of the sol–gel process for the thorium–uranium fuels keeping in view the large resources of thorium in India. Sol–gel process for fuel fabrication is also very attractive route for closing the nuclear fuel cycle efficiently. Author is BRNS Raja Ramanna Fellow.     

功能化金属有机骨架材料在放射性离子检测中的应用

With the shortage of fossil energy and increasing environmental pollution, nuclear energy has received extensive attention by its virtue of high energy density and low emission of greenhouse gases. However, radioactive nuclear waste remains a serious task for its safe and effective disposal due to their harmful effects on human health and the environment. As a new type of multifunctional nanomaterial, metal-organic frameworks (MOFs) are synthesized via the self-assembling combination of inorganic metals and organic ligands. Compared with traditional porous materials, MOFs have broad application prospects in the adsorption and detection of radioactive ions. In this paper, we reviewed the functional modification strategies of MOFs and summarized the progress in the applications of functionalized MOFs in removal and fluorescence sensing of contaminated ions in recent years. Besides, the future development trends are also discussed.