Radioactive Decontamination Research Articles

Accurate determination of 129I concentrations and 129I/137Cs ratios in spent nuclear resins by Accelerator Mass Spectrometry

Determining long-lived radionuclide concentrations in radioactive waste has fundamental implications for the long-term management of storage sites. This paper focuses on the measurement of low 129I contents in ion exchange resins used for primary fluid purification in Pressurised Water Reactors (PWR). Iodine-129 concentrations were successfully determined using Accelerator Mass Spectrometry (AMS) following a chemical procedure which included (1) acid digestion of resin samples in HNO3/HClO4, (2) radioactive decontamination by selective iodine extraction using a new chromatographic resin (CL Resin), and (3) AgI precipitation. Measured 129I concentrations ranged from 4 to 12ng/g, i.e. from 0.03 to 0.08Bq/g. The calculation of 129I/137Cs activity ratios used for routine waste management produced values in agreement with the few available data for PWR resin samples.

Radioactive decontamination using soil puddling with water(3. Decontamination and volume reduction of radioactive contaminants,<Special issue>Countermeasures for radiocesium contaminated soil)

Radioactive decontamination using soil puddling with water(3. Decontamination and volume reduction of radioactive contaminants,<Special issue>Countermeasures for radiocesium contaminated soil)

Efficient radioactive decontamination methods for removal of surface soils in farmlands

Efficient radioactive decontamination methods for removal of surface soils in farmlands

Accurate determination of 41Ca concentrations in spent resins from the nuclear industry by Accelerator Mass Spectrometry

The radiological characterisation of nuclear waste is essential for managing storage sites. Determining the concentration of Long‐Lived RadioNuclides (LLRN) is fundamental for their long-term management. This paper focuses on the measurement of low 41Ca concentrations in ions exchange resins used for primary fluid purification in Pressurised Water Reactors (PWR). 41Ca concentrations were successfully measured by Accelerator Mass Spectrometry (AMS) after the acid digestion of resin samples, followed by radioactive decontamination and isobaric suppression through successive hydroxide, carbonate, nitrate and final CaF2 precipitations. Measured 41Ca concentrations ranged from 0.02 to 0.03ng/g, i.e. from 0.06 to 0.09Bq/g. The 41Ca/60Co activity ratios obtained were remarkably reproducible and in good agreement with the current ratio used for resins management.

On the Accumulating Characteristics of Nuclide Cs in Chenopodium Album Linn, the Hyper-Accumulator Plant

Studying and screening nuclide hyper-accumulator plants and their planting methods for rapid and effective radioactive decontamination in the environment is the vital study content of the environmental radioactive contamination rehabilitation and control. This study measures and analyzes the accumulating amount and characteristics of Cs in Chenopodium album Linn by taking Chenopodium album Linn as the experimental material and CsCl solutions at different concentrations as the treatment factors, and applying the technology of pot culture to simulate the natural contaminate environment with radioactive nuclide Cs. The results indicate that the accumulating amount of Cs in Chenopodium album Linn increases as the CsCl concentration rises. The accumulating amount in the above-ground plant parts reaches the highest level of 0.964mg/g DW as the CsCl concentration reaches its highest one of 100mg/Kg; and that in the underground counterparts is 0.306mg/g DW. The accumulating amount of S (of the above-ground plant parts) /R (of the underground counterparts) > 1, having the basic characteristics of Cs hyper-accumulator plants.

On the Accumulating Characteristics of Nuclide Sr in Comnyzacanadensis (L.) Cronq, the Hyper-Accumulator Plant

Studying and screening nuclide hyper-accumulator plants and their planting methods for rapid and effective radioactive decontamination in the environment is the vital study content of the environmental radioactive pollution rehabilitation and control. Taking Comnyzacanadensis (L.) Cronq as experimental material, this study measures and analyzes the accumulating characteristics of nuclide Sr in Comnyzacanadensis (L.) Cronq by treating them with SrCl2 of various concentrations and applying the technology of pot culture to imitate the natural environment polluted by radioactive nuclide Sr. The results show that as the concentration of SrCl2 increases, the accumulation of Sr in Comnyzacanadensis (L.) Cronq also increases; when the concentration of SrCl2 content reaches a maximum level of 200mg/Kg, the SrCl2 content of the above-ground part shows its highest level of 0.709mg/g DW, while the SrCl2 content of foot end 0.201mg/g DW. The experiment results indicate that Comnyzacanadensis (L.) Cronq has the basic characteristics of Sr Hyper-accumulator, due to the fact that the accumulated amount of S in its above-ground part is larger than that of R in its foot end, i.e. S/R >1.

Micrometer-level naked-eye detection of caesium particulates in the solid state

Large amounts of radioactive material were released from the Fukushima Daiichi nuclear plant in Japan, contaminating the local environment. During the early stages of such nuclear accidents, iodine I-131 (half-life 8.02 d) is usually detectable in the surrounding atmosphere and bodies of water. On the other hand, in the long-term, soil and water contamination by Cs-137, which has a half-life of 30.17 years, is a serious problem. In Japan, the government is planning and carrying out radioactive decontamination operations not only with public agencies but also non-governmental organizations, making radiation measurements within Japan. If caesium (also radiocaesium) could be detected by the naked eye then its environmental remediation would be facilitated. Supramolecular material approaches, such as host–guest chemistry, are useful in the design of high-resolution molecular sensors and can be used to convert molecular-recognition processes into optical signals. In this work, we have developed molecular materials (here, phenols) as an optical probe for caesium cation-containing particles with implementation based on simple spray-on reagents and a commonly available fluorescent lamp for naked-eye detection in the solid state. This chemical optical probe provides a higher spatial resolution than existing radioscopes and gamma-ray cameras.

Decontamination of radioactivity from contaminated vegetables derived from the Fukushima nuclear accident

Abstract Many kinds of vegetables were contaminated by a huge amount of radioactivity, such as 131I or 137Cs, derived from the Fukushima nuclear accident. The concentration of radioactivity in contaminated vegetables was higher than the value of the legal limit for shipment, therefore, we attempted to identify a simple and effective removal method for contaminated farm products to ensure the relief of farmers and the security of consumers. First, the radioactivity distribution and adhesion state of contaminated vegetables were investigated by an imaging plate (IP) image. As a result, there were two types of contamination, spot type or spread type, of vegetables. The removal of radioactivity by physical or chemical methods was investigated. As a result, radioactivity removal by water washing showed no significant difference between boiling water and cold water. There was no significant difference between hand washing and running water washing. The result of chemical removal showed that reducing agents removed radioactivity from vegetables by 70–80% for 131I and more than 80% for 137Cs. In particular, ascorbic acid is promising as a safe and versatile option.

Surface Science Contributing to Radioactive Decontamination and Identification in Environment

Surface Science Contributing to Radioactive Decontamination and Identification in Environment

Radioactive decontamination of water by membrane processes — A review

The recent accident at the Fukushima Daiichi Nuclear Power Plant caused by the Great East Japan Earthquake of March 11, 2012 reminded us vividly of the serious hazards of radioactive substances spread over a wide range of the affected region. Currently, there is a great concern over the effect of contaminated soil and water on the health and safety of the inhabitants of the region. Hence, the advancement in the technologies of nuclear waste treatment is of vital importance if we decide to live with nuclear power to maintain our modern civilization. Among various separation technologies used, membrane technologies have been chosen in this article since they are considered as one of the emerging technologies with many advantages over the conventional processes. In this review the membrane technology is classified into different processes and, for each process, progress made since the onset of this millennium in the radioactive decontamination of water is shown. The new directions are shown by considering the progress made in membrane manufacturing and membrane processes. Thus, the combined efforts of the researchers who are engaged in membrane and membrane process design with those who are engaged in nuclear waste treatment near the plant sites were highlighted.

A new series of Cs+, K+ and Na+ chelators: Synthesis, kinetics, thermodynamics and modeling

The synthesis of two molecules, B1 and B2, based on elements of norbadione A, the natural Cs+ chelator in mushrooms, associated, in the case of B2, with an 18-crown-6 ether is reported. Thermodynamic and kinetic analyses performed in water, ethanol and ethanol/water 9/1 v/v (M1) show in M1 and ethanol that B1 and B2 form stable complexes with Na+, K+ and Cs+. Affinity constants, measured spectrophotometrically in ethanol and M1, by the use of the Specfit program, are in the 105 and 106 range for B1 and B2, respectively. The second-order rate constants are in the 106–107M−1s−1 range and the first-order rate constants about unity. The ratios of the second-order/first-order rate constants confirm the thermodynamic results in EtOH. The kinetic processes become much too fast to allow runs in M1. Molecular simulations in EtOH imply the existence of two isomers for each of the Cs+/B1 and Cs+/B2 complexes. With B1, the more stable one is that in which the two enolates are parallel and mimic the alkali-metal inclusion cavity already envisaged for norbadione A. With B2, two similar structures are extracted, in both of which Cs+ is included in the crown ether and capped by the enolate. The affinity of B1 for Cs+ is comparable to that of norbadione A, whereas that of B2 is higher. These results are encouraging as they introduce a new series of alkali chelators which can lead to molecules capable of complexing 137Cs+ for radioactive decontamination.

Radiation Effects on Zeolite Nanomaterials - Some Potential Implications for Cleaning Liquid Nuclear Waste and for Enhanced Radioactive Decontamination

A series of group 1 and group 2 element cation-exchanged samples of zeolite X were prepared and exposed to a beam of spin-polarised, positive muons (of energy 28MeV/c) from a particle accelerator. Longitudinal field repolarisation measurements were made which identified, in each case, both diamagnetic and paramagnetic muon fractions. One of the paramagnetic components revealed a hyperfine field compatible with values reported previously for free muonium atoms (1585 G), while a secondary component was detected showing roughly half the hyperfine coupling measured for atomic muonium, leading to the conclusion that the muonium had become chemically-bound within the zeolite structure, probably via a single-electron bond to a coordinatively unsaturated aluminium atom. A significant “lost fraction” was also indicated along with superhyperfine and anisotropic components that repolarised in weaker magnetic fields (0-100G). As a general trend, the muonium atom yield was found to increase in order of the increasing radius/charge (riz) ratio, though it is constant within the experimental errors, while the chemically bound muonium was formed in similar proportion in all samples (14.1 + 1.9% of the total muonium polarisation), with the exception of HX and the parent NaX (from which the other zeolite samples were prepared by cation-exchange), in which it was absent. Along with data from zero-field experiments which were also undertaken, this is interpreted in terms of an entrapment or effective “scavenging” of radiolytic electrons by the cations (in the order Na+>K+; Mg2+>Ca2+>Sr2+>Ba2+) whose combination with positive muons is therefore impeded, thus reducing the yield of muonium atoms. Results for LiX are anomalous since the muonium yield is greater than expected, possibly due to a greater degree of covalency in the Li-0 bonding than pertains for the other cations. These results may have some implications for zeolites that suffer longterm radiation exposure/damage when they are used to clean radioactive cations (e.g. Cs +, Sr2+) from the waters of nuclear power stations and as materials whose cation-exchange capacity has been deliberately enhanced by prior exposure to ionising radiation.

Decontamination of Human and Rabbit Skin Experimentally Contaminated with 99mTc Radionuclide Using the Active Components of “Shudhika”—a Skin Decontamination Kit

Radioactive contamination can occur as a result of accidental or intentional release of radioactive materials (RM) into the environment. RM may deposit on clothing, skin, or hair. Decontamination of contaminated persons should be done as soon as possible to minimize the deleterious health effects of radiation. The goal of this study was to evaluate the decontamination efficiency (for residual contaminant) of the active components of "Shudhika," an indigenously developed skin decontamination kit. The study kit is for external radioactive decontamination of intact skin. Decontamination efficiency was evaluated on the skin surface of rabbit (n = 6) and human volunteers (n = 13). 99mTc sodium pertechnetate (200-250 μCi) was used as the radio-contaminant. Skin surface area (5 × 5 cm2) of thoracic abdominal region of the rabbit and the forearm and the palm of human volunteers were used for the study. Decontamination was performed by using cotton swabs soaked with chemical decontamination agents of the kit. Decontamination efficiency (% of the contaminant removed) was calculated for each component of the study. Overall effectiveness of the kit was calculated to be 85% ± 5% in animal and 92% ± 3% in human skin surfaces. Running water and liquid soap with water was able to decontaminate volunteers' hand and animal skin up to 70% ± 5%. Chemical decontamination agents were applied only for trace residues (30% ± 5%). Efficiency of all the kit components was found up to be 20% ± 3% (animal) and 28% ± 2 (human), respectively. Residual contamination after final decontamination attempt for both the models was observed to be 12% ± 3% and 5% ± 2%. After 24 and 48 hours of the decontamination procedure, skin was found to be normal (no redness, erythema and edema were observed). Decontaminants of the study kit were effective in removal of localized radioactive skin contamination when water is ineffective for further decontamination. By using the chemical decontaminants of the study kit, the use of water and radioactive waste generation could be reduced. Cross-contamination could also be avoided. During radiologic emergencies where water may be radioactively contaminated, the study kit could be used.

森林の放射能汚染と除染

森林の放射能汚染と除染

Multi-phased, post-accident support of the Fukushima Dai-Ichi nuclear power plant

In the wake of the March 11 earthquake and tsunami and the subsequent flooding of several of the Fukushima Dai-Ichi reactors, Japan and the Japanese utility TEPCO faced a crisis situation with incredible challenges: substantial amounts of radioactive mixed seawater and freshwater accumulated in the basements of four reactor and other buildings on the site. This water held varying levels of contamination due to the fact that it had been in contact with damaged fuel elements in the cores and with other contaminated components. The overall water inventory was estimated at around 110,000 tons of water with contamination levels up to the order of 1 Ci/l. Time was of the essence to avoid overflow of this accumulated water into the ocean. AREVA proposed, designed and implemented a water treatment solution using a proven chemical coprecipitation process with ppFeNi reagent, which is currently in use for effluent treatment on several nuclear sites including AREVA sites. In addition to the extremely short schedule the other challenge was to adapt the chemical treatment process to the expected composition of the Fukushima water and, in particular, to evaluate the impact of salinity on process performance. It was also necessary to define operating conditions formore » the VEOLIA equipment that had been selected for implementation of the process in the future facility. The operation phase began on June 17, and by the end of July more than 30,000 tons of highly radioactive saltwater had been decontaminated - the Decontamination Factor (DF) for Cesium was ∼10{sup 4}. It allowed recycling the contaminated water to cool the reactors while protecting workers and the environment. This paper focuses on the Actiflo{sup TM}-Rad water treatment unit project that was part of the TEPCO general water treatment scheme. It presents a detailed look at the principles of the Actiflo{sup TM}-Rad, related on-the-fly R and D, an explanation of system implementation challenges, and a brief summary of operation results to date. AREVA's response to the Fukushima Dai-Ichi crisis was multi-phased: emergency aid and relief supply was sent within days after the accident; AREVA-Veolia engineering teams designed and implemented a water treatment solution in record time, only 3 months; and AREVA continues to support TEPCO and propose solutions for waste management, soil remediation and decontamination of the Fukushima Dai-Ichi site. Despite the huge challenges, the Actiflo{sup TM}-Rad project has been a success: the water treatment unit started on time and performed as expected. The performance is the result of many key elements: AREVA expertise in radioactive effluents decontamination, Veolia know-how in water treatment equipments in crisis environment, and of course AREVA and Veolia teams' creativity. The project success is also due to AREVA and Veolia teams' reactivity and high level of commitment with engineering teams working 24/7 in Japan, France and Germany. AREVA and Veolia deep knowledge of the Japanese industry ensured that the multi-cultural exchanges were not an issue. Finally the excellent overall project management and execution by TEPCO and other Japanese stakeholders was very efficient. The emergency water treatment was a key step of the roadmap towards restoration from the accident at Fukushima Dai-Ichi that TEPCO designed and keeps executing with success. (authors)« less

除染へ挑戦する建設土木技術

除染へ挑戦する建設土木技術

The Effectiveness of Decontamination Products in the Nuclear Medicine Department

This study assesses the effectiveness of using everyday cleaning agents for the radioactive decontamination of wet (99m)Tc-pertechnetate spills in the nuclear medicine department. Six cleaning agents (water, water and soap, alcohol, bleach, a commercial glass cleaner, and a commercial decontaminating agent) were analyzed for decontamination effectiveness for a wide range of surfaces (Formica, vinyl, vinyl-polyester, plastic, rubber, and polyester). Within the experiment, the contamination was removed to radioactivity levels of less than 1% of the original contamination level. The results indicate that for a range of surfaces, the investigated commercially available cleaning agents had little or no benefit over plain tap water when used to decontaminate (99m)Tc-pertechnetate spills.

Evaluation of the efficiency of radioactive decontamination for alkyd and epoxy–urethane coating systems

This article presents experimental results obtained by the investigation of the efficiency of radioactive decontamination of a metal surface with alkyd and epoxy–urethane coating systems, which are used for the painting of military equipment. During the evaluation of the efficiency of decontamination, the impact of contaminants on the coating was not examined but the amount of contaminants residual after decontamination was, and was determined by activity measurements of the surface. The samples for testing were painted aluminum plates contaminated by liquid solutions of radioactive isotopes 60Co, 133Ba, 152Eu and 241Am (A=12297.91 Bq/ml). Decontamination of contaminated samples was performed with 0.5% detergent solution on the basis of synthetic surfactants. The activity measurements of samples were conducted using gamma spectroscopy system with a high-resolution high-purity germanium (HPGe) detector of relative efficiency of 50% at 60Co (1.33 MeV). The degree of removal of the radioactivity on the samples was observed as an indicator of the efficiency of decontamination. A comparison of the results is presented in relation to the retention time of the contamination on the surface coating, which is an important factor for the efficiency of decontamination. The samples with an alkyd coating system showed better efficiency of decontamination than the samples with the epoxy–urethane coating system, although the coatings based on epoxy and urethane resin were superior in relation to the alkyd in terms of protection, decorative characteristics and chemical resistance. The difference in the efficiency of decontamination for the examined coatings increases almost linearly in relation to the retention time of the contaminants in the coating.

Selective Radioactive Decontamination employing Dual Stimuli Responsive N-Aza crown ether containing polymer hydrogels

AbstractWe report the synthesis and properties of two different hydrogels based on N-isopropylacrylamide/acrylic acid and copolymers of oligo-ethylene glycol methacrylates incorporating N-Aza crown ethers. Both hydrogels show rapid response to environmental stimuli and their size can be tuned by pH and temperature. Swollen states lead to high adsorption of water and high contact surface area with ions whereas in the collapsed state the material releases water and the ions not selectively retained by the polymer.Preliminary autoradiography tests show that these materials strongly bind 90Sr and both pH and temperature can be used to fine tune binding selectivity. This results in such materials being promising candidates for use as smart scavenging agents for radioactive decontamination.

Adsorption of radioactive substances by an electrically activated natural adsorbent

Processes of radioactive decontamination of water with application of an electrical discharge effect are investigated. It is shown that use of electrical discharge of the torch type considerably increases the efficiency of the adsorption decontamination of water. By the method of thermally stimulated relaxation, it is revealed that accumulation of surface and space charges takes place in adsorbents. The method of X-ray structural analysis is shown to be a tool allowing qualitative investigation of the processes in the adsorbent structure.