The updated IAEA database of natural matrix reference materials

The International Atomic Energy Agency (IAEA) maintains a database of biological and environmental reference materials of natural origin (human and animal tissues, foods, plants, soils, sediments, etc.) for trace elements, radionuclides, stable isotopes, organic contaminants and other related measurands. The purpose is to help analysts to select reference materials for quality assurance purposes that match as closely as possible (i.e., with respect to matrix type and concentrations of the measurands of interest) the real samples that are to be analyzed. Former versions of this database were prepared in co-operation with the United Nations Environment Programme (UNEP), and provided as hardcopies free of charge. The latest version was from 1995. More recently the database has been updated by the IAEA so that it now contains more than 22,500 values (mass fraction or concentration) for 660 different measurands and 1,705 reference materials developed by 56 producers from 22 countries. This paper gives an overview of the structure and content of the database and of the two ways it may be browsed. Emphasis is given to reference materials that are intended to verifying analysis for radioanalytical measurements. The database is soon accessible on-line, cost-free, via the internet.     

Radiation chemistry of polymers

Results of basic and applied research in radiation chemistry of polymers in Russia and Belarus for the last 5–10 years are presented.     

Radiation processing techniques in remediation of pollutants,and the role of the IAEA in supporting capacity building in developing countries

Radiation treatment, or a combination of radiation with conventional biological–chemical–physical processes, can help in the remediation of contaminated surfaces and in combating industrial chemical effluents and air pollution. The use of ionizing radiation as a powerful tool for inactivation of microbes is a valuable option to address likely threats from biohazard contamination that could be introduced either deliberately or inadvertently into areas where the public are exposed to, as well as for treatment of volatile organic compounds and similar hazardous chemical agents is an emerging development in tackling harmful pollutants. The role of the IAEA has been crucial both in supporting the development of local capabilities as well as in fostering international cooperation due to the multidisciplinary expertise required for achieving sustainable benefits. The IAEA is implementing Coordinated Research Projects, (CRP) thematic topical reviews of issues and challenges involved, and Technical Cooperation (TC) assistance in establishing and maintaining infrastructure in the MS. This paper will give an insight into the above mentioned IAEA activities, with examples of successes achieved through CRPs, as well as challenges on the road for broader dissemination of radiation processing technology for environmental remediation.     

Radiation modification of semicrystalline polymers

Three problems of the radiation modification of polymers are dealt with. Different methods of grafting are compared with respect of the formation of true graft copolymer and homopolymer in the polyethylene-styrene system; the prevention of the penetration of monomer by grafting polytetrafluoroethylene is shown; the mechanical properties of crosslinked ethylene polymers below and above the melting point are discussed.     

Laser material processing of polymers

Since the first laser was developed in 1960, laser technology has been growing and now covers a wide range of laser types and applications. One of the most important applications of lasers is the use of a high power laser beam for material processing. One very interesting material group in which lasers can be used for processing is polymers. In these materials the lasers can be used for drilling and cutting, as well for welding. Lasers can produce holes at very high speeds and in dimensions which in practice are unobtainble by other processing methods. Contour cutting with high speeds and narrow tolerances is also possible.

This paper will briefly describe the laser processing mechanisms involved in laser drilling, cutting, welding and engraving, and will give some typical examples of laser processing with special attention to processing of polymers.     

Radiation degradation susceptibility of vinyl polymers: Nitriles and anhydrides

The effect of γ irradiation on a series of vinyl polymers, which included polymethacrylonitrile, poly(α-chloroacrylonitrile), poly(dimethyl itaconate), poly(acrylic anhydride), and poly(methacrylic anhydride), was studied as part of a program to develop improved positive lithographic resists. Radiation-induced degradation was observed for polymethacrylonitrile, poly(α-chloroacrylonitrile), and poly(methacrylic anhydride). Molecular weight degradation as a function of dose was monitored by membrane osmometry or GPC techniques. For γ-irradiated poly(dimethyl itaconate) and poly(acrylic anhydride) crosslinking was found to predominate over chain scission. [G(s)–G(x)] values, calculated from molecular weight inverse versus dose curves, indicate that both nitrile polymers degraded more efficiently than a poly(methyl methacrylate) reference standard on the basis of M _n changes. The radiation behavior of the first three polymers confirms earlier findings than vinyl polymers with quaternary carbons predominantly degrade when subjected to ionizing radiation.     

IAEA Programme of natural matrix reference materials for the determination of radionuclides

Summary The International Atomic Energy Agency has been providing analytical quality control services (AQCS) to its Member States since the 1960's. The AQCS programme distributes reference materials (RMs), organizes intercomparison runs, and provides training courses for quality assurance in chemical analysis and radioactivity measurements of food, biological, environmental and marine materials. This paper focusses on those aspects of the subject dealing with reference materials and intercomparison runs for the determination of radionuclides. Nineteen natural matrix reference materials are available for the determination of radionuclides. Twelve new intercomparison and reference materials are in preparation or under consideration. The radionuclides of interest include: K-40, Mn-54, Co-60, Sr-90, Tc-99, Ru-106, Ba-133, Cs-134, Cs-137, Pb-210, Ra-226, Th-228, Th-232, Pu-238, Pu-239+240.     

Radiation detection and data processing

Some of the advances that have taken place in radiation detection and data processing over recent years have been the direct consequence of advances in technology. A wider range of detectors has resulted from improvements in materials available and a reduction in the cost of data processing devices has followed from advances in electronic circuit fabrication techniques. Some selected examples are given and discussed.     

Radiation sterilization of enzyme hybrids with biodegradable polymers

Ionizing radiations, which have already been utilized for the sterilization of medical supplies as well as gas fumigation, should be the final candidate to decontaminate “hybrid” biomaterials containing bio-active materials including enzymes because irradiation induces neither heat nor substances affecting the quality of the materials and our health. In order to check the feasibility of ⁶⁰Co-gamma rays on these materials, we selected commercial proteases including papain and bromelain hybridized with commercial activated chitosan beads and demonstrated that these enzyme-hybrids suspended in water showed the significant radiation durability of more than twice as much as free enzyme solution at 25-kGy irradiation. Enhanced thermal and storage stability of the enzyme hybrids were not affected by the same dose level of irradiation, either, indicating that commercial irradiation sterilization method is applicable to enzyme hybrids without modification.     

Chemical modification of natural polymers in China

Abstract

This paper introduces the main Chinese research work on the chemical modification of natural polymers including silk, Chinese lacquer, gutta-percha, cellulose, and chitin. The following aspects of this research work are emphasized: research on the mechanism of graft copolymerization of vinyl monomer onto natural polymers, research on overcoming the defects of natural polymers to allow further application by chemical modification, and research on exploring new applications of natural polymers.     

Radiation contribution to the thermal conductivity of plastic foams

The validity of two approaches widely used to determine the radiant thermal conductivity in plastic foams is discussed. While one approach is based on the solution of a geometric model, the other is derived from the experimental determination of the extinction coefficient. A comparison to recently reported experimental data shows that the geometric approach predicts values that are in good agreement. In contrast, values deduced from measurements of the mean extinction coefficient significantly underestimate the radiant thermal conductivity, an effect that can be traced to the way that the extinction coefficient is measured. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 190–192, 2005     

Radiation chemistry of smart polymers (A Review)

Radiation chemistry methods used to prepare smart polymers are surveyed. The properties of these polymeric materials are considered. The benefits of radiation-chemical procedures for manufacturing smart polymers are discussed. The areas of their practical use are outlined     

Biodegradable polymers derived from natural fatty acids

A new class of polyanhydrides synthesized from nonlinear hydrophobic fatty acid esters, based on ricinoleic, maleic acid, and sebacic acid, possessed desired physico-chemical and mechanical properties for use as drug carriers. The polymers were synthesized by melt condensation to yield film-forming polymers with molecular weights exceeding 100,000. Their rate of elimination from rats in the course of about 2 months was faster than that found for similar polyanhydrides previously tested. In vitro studies showed that these polymers underwent rapid degradation in the first 10 days. The drug release followed first-order kinetics, showing a rapid drug release rate in the first 10 days which correlated with the degradation of the polymers. The fatty acid ester monomers underwent in vitro enzymatic degradation to the natural starting acids. Tests in rats demonstrated their toxicological inertness and biodegradability. © 1995 John Wiley & Sons, Inc.     

Polyelectrolyte capsules made of two biocompatible natural polymers

In this study the influence of the experimental conditions on the obtention of polyelectrolyte multilayer capsules was investigated. Two ways of the simple coacervation method was used to obtain spherical capsules involving chitosan and hyaluronan, chitosan being inside the particle covered by a hyaluronan layer to increase the biocompatibility. The ¹H-NMR spectroscopy confirmed a polyelectrolyte complex formation and the optical microscopy shows that the complexed capsules have good sphericity with average diameters ranging from 590 at 1550 μm in the experimental conditions adopted. One can observe that in the acid medium the complexed capsules are much stable than the chitosan beads. The structures described provide a starting point for the design and fabrication of complexed capsules made of two biocompatible natural polymers with potential applicability in medical or pharmaceutical applications. Few diffusion experiments demonstrated that the complexed layer controls the diffusion of dextran included in the chitosan inner domain.     

Radiation effects on polymers—IV: Straight radiation vulcanization of styrene-butadiene rubber mixes

Vulcanization of styrene-butadiene rubbers was carried out by gamma radiation in air. For unloaded unextracted rubbers, the dose required for optimum cross-linking was about 40 megaroentgens (MR). Elimination of foreign materials and stabilizers and also incorporation of filler affected the vulcanization. Loaded samples gave vulcanizates with best complex physico-mechanical properties for filler content of 50 (phr) and a dose of 30 MR. Evaluation of various fillers has shown that the best properties were obtained with HAF among the black fillers and silica in the case of white fillers.     

Radiation processing of wastewater evaluated by toxicity assays

Biological assays have been applied to industrial effluents and sewage influents, from distinct sites, before and after being submitted to ionizing radiation treatment. The objective of this study was to evaluate the efficiency of radiation, mainly electron beam accelerator, for the acute toxicity removal. The selected sampling presented a very toxic level and the radiation process was efficient for toxicity removal for 87.7% of irradiated samples. The sewage influents required lower radiation doses to reduce toxicity when compared to raw industrial effluents.