BCR certified reference materials for reactor neutron dosimetry

A series of reference materials intended for use as activation or fission monitors for neutron fluence rate measurements has been prepared by the Joint Research Centre of the European Commission. Certification has been carried out by expert European laboratories and distribution of the certified reference materials (CRMs) is through the BCR programme of the Commission. The list (18 CRMs) includes materials to cover the complete energy spectrum, and suitable for different irradiation times. Fission monitors are ²³⁸UO₂ or ²³⁷NpO₂ in the form of microspheres. Activation monitors are high purity metals (Ni, Cu, Al, Fe, Nb, Rh, or Ti), certified for interfering trace impurities, or dilute aluminium-based alloys, where aluminium is chosen as a suitable matrix for reducing the neutron self-shielding effect. Newly certified materials are IRMM-530R Al-0.1%Au, replacing the exhausted IRMM-530 material, used as comparator for k ₀-standardization, and three new Al-Co alloys (0.01-1%Co). Two others, in the process of certification are Al-0.1%Ag and Al-2%Sc for thermal and epithermal fluence rate measurements. Other candidate reference materials currently being certified are two uranium-doped glass intended for dosimetry by the fission-track technique.     

A local intercomparison study of ESR dosimetry using tooth enamel

Using electron spin resonance (ESR), tooth enamel is a possible dosimeter in case of a radiation accident. To check the present status of this technique, we conducted a local intercomparison study. We irradiated several samples of tooth enamel with a⁶⁰Co source. Three institutes in Belgium and The Netherlands recorded the ESR signal of the samples. The results of the measurements and the methods used are compared. It is concluded that ESR on tooth enamel can be a useful technique in accident dosimetry, provided further research is done.     

ESR imaging of polymers and solid materials

EPR imaging was applied to the study of several important processes in polymers and materials. The solvent diffusion and induced swelling was visualized in the water/DMF or toluene/DMF interactions with polycarbonate or polystyrene molded rods. The cross-sectional images revealed non-homogeneous solute/solvent diffusion, rod expansion and crack development. The ESR lineshapes in all cases above confirmed that the nitroxide imaging agent did not interact significantly with the polymer matrix; thus the paramagnetic distribution reflected bulk solvent distribution quite well. The diffusion of an electrolyte buffer (Krebs) solution containing a nitroxide spin probe was followed in a cross-sectional image of a polyacrylamide gel rod. A one-dimensional radial diffusion constant was calculated for the solvent piperidinol nitroxide spin probe, TEMPOL. Lastly, solid coal rods were monitored during mild pyrolysis at 150°C in air. Here the naturally occurring organic radical composition was imaged. Even with the increase in total ESR signal and subsequent decline to ca. the initial levels, the coal rod cross-section was essentially homogeneous in paramagnetic centers throughout the heating process. All of the imaging above utilized a homemade L-band, flat loop surface coil spectrometer.     

Synthesis of silver nanoparticles using dl-alanine for ESR dosimetry applications

The potential use of alanine for the production of nanoparticles is presented here for the first time. Silver nanoparticles were synthesized using a simple green method, namely the thermal treatment of silver nitrate aqueous solutions with dl-alanine. The latter compound was employed both as a reducing and a capping agent. Particles with average size equal to 7.5 nm, face-centered cubic crystalline structure, narrow size distribution, and spherical shape were obtained. Interaction between the silver ions present on the surface of the nanoparticles and the amine group of the dl-alanine molecule seems to be responsible for reduction of the silver ions and for the stability of the colloid. The bio-hybrid nano-composite was used as an ESR dosimeter. The amount of silver nanoparticles in the nanocomposite was not sufficient to cause considerable loss of tissue equivalency. Moreover, the samples containing nanoparticles presented increased sensitivity and reduced energetic dependence as compared with pure dl-alanine, contributing to the construction of small-sized dosimeters.     

New inorganic materials for medicine

New inorganic materials (metals and their alloys, carbon materials, ceramics, glass, and glass-ceramics) that are used in one of the branches of medicine,viz., bone endoprosthetics and implantology, are considered. Attention is concentrated on calcium- and phosphoruscontaining glassy and glass-ceramic materials that exhibit bioactivity with respect to a living bone. The main statements of the modern theory of bioactivity of these materials are outlined; physicochemical aspects of this theory are considered in detail. Extensive possibilities for controlling the structures, medico-biological, physicochemical, and mechanical properties of bioactive glasses, glass-ceramics, ceramics, and composites based on them are demonstrated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 246–253, February, 1997.     

Studies on some materials suitable for use as internal standards in high energy EPR dosimetry

EPR-spectroscopic properties (line-intensity,-width, andg-factors) of pyrolized at 550°C sucrose, MgO and MgO doped with Mn²⁺ ions (500∶1) remain unchanged after high-dose (1–100 kGy) irradiation, whereas CaO gives an EPR signal. These properties of these materials make it possible to use them as internal reference EPR standards in the work under conditions of strong ionisation environment, for precise determination of theG-values of other materials, for obtaining exact magnitudes of increase of the EPR response when the method of additional dose is applied, to follow the kinetics of decay of some radiation induced defects.     

New materials for sputtered strain gauges

Commercial strain gauges obtain a gauge factor of approximately 2 with a compensated temperature coefficient of resistivity (TCR). Therefore, material development for sputtered thin films with a high gauge factor and negligible TCR was conducted. The object for self compensated sensor materials is the combination of a semiconducting material (negative TCR) with high gauge factor and a metal (positive TCR) leading to a TCR close to zero. With nickel containing diamond-like carbon films (Ni-DLC or a-C:H:Ni) and Ag-ITO compounds zero crossing in TCR and gauge factors higher than 10 were achieved.     

New materials for sorption of hydrogen

The influence of temperature, duration of thermal treatment, and oxidation modes of the aluminum base on processes in which intermetallic compounds LiLaAl are formed by the method of electrochemical cathodic intercalation was studied. The optimal modes of formation of LiLaAl_ox compounds exhibiting high sorption capacity for hydrogen were determined.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9, 2004, pp. 1516–1519.Original Russian Text Copyright © 2004 by Olshanskaya, Sobgaida, Popova.     

Poly(vinyl alcohol)/heteropolyacid nanocomposites as new materials for radiochromic dosimetry in radiation processing

Radiochromic films composed of polymer matrices and organic dyes are widely used for routine dosimetry purposes in operation of various radiation facilities—gamma and X-ray-irradiation, electron accelerators, and so on. However, the sensitivity of these films rapidly decreases at doses exceeding 30–50 kGy due to a saturation of their optical response, making them unsuitable for accurate dosimetry in radiation processing of polymers and composites where doses up to 200 kGy are typically employed. To overcome this limitation, the use of inorganic substances as the coloring agents of polymer-based radiochromic films was proposed in this paper, specifically, heteropolyacidacid H₃PW₁₂O₄₀ (tungstophosphoric acid) in the matrix of poly(vinyl alcohol) (PVA). Nanocomposite PVA/H₃PW₁₂O₄₀ films were prepared by solution casting and their optical responses toward ⁶⁰Co gamma radiation and beams of 6 MeV electrons for a dose range of 10–200 kGy were investigated. It was established that upon exposure to gamma rays and electron beams, the films turn blue and a broad absorption band at 750 nm appears in their spectra. Importantly, the radiation-induced optical absorption increases in a linear fashion up to the dose of 150 kGy and only slightly deviates from linearity at 200 kGy. Moreover, it was found that the PVA/H₃PW₁₂O₄₀ films have a long shelf life, are dose-rate independent within a wide range, and color-stable after irradiation. All these features make the nanocomposite PVA/H₃PW₁₂O₄₀ films promising for use as routine dosimeters and dose labels in a much wider range of high doses as compared to radiochromic films based on organic dyes.     

New fluoropolymer materials

We report the synthesis of two classes of fluoropolymers that could impact several key lithographic techniques; one has potential applications in next generation photolithography (193 nm, 157 nm, and immersion lithography) and the other in lithographic techniques which are emerging as viable alternatives to photolithography for future applications (i.e., soft lithography).     

Polysaccharides/silica hybrid materials: New perspectives for sustainable raw materials

Polysaccharides/silica hybrids prepared through sol-gel reaction have been studied as a model for new generation of hybrid materials for a virtually unlimited number of applications. Numerous studies have therefore attempted to increase the homogeneity between the organic and inorganic moieties using a wide variety of silica precursors and crosslinking reagents. The current review summarizes and discusses the attempts for using polysaccharides for producing hybrid materials with collective properties from the two counterparts. It discusses several issues and strategies to tune the homogeneity of polysaccharide/silica hybrids and the potential applicability of these hybrid materials in biomedical and industrial fields.     

一种新型葡萄糖基化竹红菌素的合成和ESR研究

以巯基乙酸取代的竹红菌乙素和氨基葡萄糖为反应物,只用一步就合成了一种新型葡萄糖修饰的竹红菌乙素.氨基葡萄糖的取代改善了竹红菌乙素的水溶性及其在光疗窗口的吸收,并保持了其产生¹O₂、O₂^·-、^·OH和半醌负离子自由基的光化学活性.     

New marine biological reference materials for trace metals

Summary A list of reference materials and certified reference materials (CRM's) useful to the marine analytical chemist for validation of trace element determinations is given. The preparation and certification for the trace element content of two new marine biological reference materials, dogfish flesh (DORM-1) and dogfish liver (DOLT-1), is described.     

Metal-organic frameworks—New materials for hydrogen storage

Published data on the physical sorption of hydrogen by new materials with a large specific surface area, crystalline microporous metal-organic frameworks (MOFs), are systematized and analyzed. The hydrogen-accumulating properties of MOFs are compared with those of traditional materials (charcoals and zeolites) and nanocarbon systems. The role of secondary hydrogen spillover in the development of new approaches to increase the adsorption capacity of hydrogen storage materials is separately considered.     

New membrane materials for potassium-selective ion-sensitive field-effect transistors

Several polymeric materials were studied as membrane materials for potassium-selective ion-sensitive field-effect transistors (ISFETs) to overcome the problems related with the use of conventional plasticized poly(vinyl chloride) membranes casted on ISFET gate surfaces. Several acrylate materials, such as ACE, Epocryl and derivatives, showed no reproducible results. Three room-temperature vulcanizing (RTV)-type silicone rubbers were tested. The addition-type RTV-2 silicone rubber was not suitable as a membrane material, but the condensation-type RTV-1 and especially the RTV-2 silicone rubber showed good results. ISFETs with a Silopren membrane showed a durability of at least 2 months.     

New trends in photobiology light dosimetry: Status and prospects

This paper is a report on the state of the art of light dosimetry in photomedicine and photobiology. The basic quantity of interest is the radiant energy fluence rate, which can either be measured using a suitable probe, or calculated theoretically from measured optical constants. First, theoretical models used to analyse experimental transmission and reflection data are briefly discussed. It is shown that a two-flux model derived from the transport equation in the diffusion approximation resembles the Kubelka-Munk and other heuristic models. This illustrates the limitations of these models and suggests their abandonment in favour of transport theory. For theoretical energy fluence rate calculations at least three optical constants are needed, namely the absorption coefficient, the scattering coefficient and the average cosine of the scattering angle. These three constants have been measured for very few tissues. In principle only two of the three constants can be measured directly on thin samples, independent of a theoretical model. The energy fluence rate can be measured quantitatively with a miniature fibre optic probe with isotropic response. Such measurements allow indirect determination of the three optical constants. It appears that we are just beginning to understand the distribution of light energy fluence rate in tissues. Tasks for the near future are comparison of methods to measure optical constants, quantitative checks of calculated and measured energy fluence rates in model tissues and optical phantoms and further development of theoretical models. Particular attention is required for boundary conditions, with and without refractive index matching.     

New fields in the technology for manufacturing carbon-carbon materials. Application of carbon-carbon materials

The review summarizes the results of research on general regularities of synthesis of granulated carbon-carbon materials on the basis of nanodispersed carbon and low-temperature pyrocarbon and of works on application of these materials.