Volumen 62 (2017): Edición 4 (December 2017)

The aim of this study is to exploit a suitable chitosan extraction method from the chitin of indigenous shrimp shells by employing different physicochemical treatments and to improve different bioactive properties of this extracted chitosan (CS) by applying gamma radiation. Chitin was prepared from shrimp shell by pretreatment (deproteination, demineralization and oxidation). Chitosan was extracted from chitin by eight different methods varying different physicochemical parameters (reagent concentration, temperature and time) and assessed with respect to the degree of deacetylation, requirement of time and reagents. The method where chitin was repeatedly treated with 121°C for 30 min with 20 M NaOH, produced the highest degree of deacetylation (DD) value (92%) as measured by potentiometric titration, with the least consumption of time and chemicals, and thus, selected as the best suitable extraction method. For further quality improvement, chitosan with highest DD value was irradiated with different doses (i.e., 5, 10, 15, 20 and 50 kGy) of gamma radiation from cobalt-60 gamma irradiator. As the radiation dose was increased, the molecular weight of the wet irradiated chitosan, as measured by the viscosimetric method, decreased from 1.16 × 10⁵ to 1.786 × 10³, 1.518 × 10³, 1.134 × 10³, 1.046 × 10³ and 8.23 × 10² dalton, respectively. The radiation treatment of chitosan samples increased the antimicrobial activity significantly in concentration dependent manner on both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria, as determined by the well-diffusion method. Four to five percent wet chitosan treated with a radiation dose range of 5.0–10.0 kGy rendered the highest antimicrobial activity with least energy and time consumption. Solubility, water binding capacity (WBC) and fat binding capacity (FBC) also improved due to irradiation of chitosan.

Radiation sterilization has been considered a mass decontamination technique for biodegradable cultural heritage (CH) since its widespread application in the medical field. Initial experiments have revealed advantages, for example, efficiency and effectiveness, but also disadvantages, namely “side effects” concerning CH materials. More than 50 years later, the adequacy of ionizing radiation for some CH artefacts is still the subject of discussion. The main reason why is that science and industry are not yet able to provide a more efficient technique for treating mass decontamination. For wooden items, there is general agreement that the irradiation dose required for insect eradication is not damaging, even in the case of polychromed wood. For cellulose pulp (paper), there is a reduction in polymerization degree (DP) at the high doses necessary to stop the attack of fungi, but this should be considered taking into account the purpose of the treatment. Emergency or rescue treatments are necessary to mitigate the consequences of accidents or improper storage conditions. In some cases (archives), the value of written information is greater than the historical value of the paper support. For other materials, namely textiles, leather and parchment, less research has been published on the effect of ionizing radiation treatment. As a general rule, irradiation is not necessary when only a few CH elements are present that are affected by biological contamination since restorers can solve the problem by classical means. The need for radiation treatment arises when large collections (hundreds, thousands or even more elements) are heavily affected by the biological attack. In Romania, the IRASM gamma irradiator of IFIN-HH is receiving an increasing number of requests for CH treatment, mainly due to an intensive research programme concerning this topic and close liaison with CH owners or administrators. Besides reviewing the scientific results obtained in Romania and abroad, this paper presents some examples from experiences in Romania.

Since the 1980s, research and qualification activities are being carried out at the ⁶⁰Co gamma Calliope plant, a pool-type irradiation facility located at the Research Centre ENEA-Casaccia (Rome, Italy). The Calliope facility is deeply involved in radiation processing research and on the evaluation and characterization of the effects induced by gamma radiation on materials for different applications (crystals, glasses, optical fibres, polymers and biological systems) and on devices to be used in hostile radiation environment such as nuclear plants, aerospace and high energy physics experiments. All the activities are carried out in the framework of international projects and collaboration with industries and research institutions. In the present work, particular attention will be paid to the cultural heritage activities performed at the Calliope facility, focused on two different aspects: (a) conservation and preservation by bio-deteriogen eradication in archived materials, and (b) consolidation and protection by degraded wooden and stone porous artefacts consolidation.

This research specifically focused on the development of a novel methodology to reduce excess nitrate in drinking water utilizing zerovalent iron nanoparticles (nZVI)-stabilized radiation-grafted copolymer matrix. nZVI was synthesized by borohydrate reduction of FeCl₃ and stabilized on acrylic acid (AAc)-grafted non-woven polyethylene/polypropylene (NWPE/PP-g-AAc) copolymer matrix, which was grafted using gamma radiation. The use of nZVI for environmental applications is challenging because of the formation of an oxide layer rapidly in the presence of oxygen. Therefore, radiation-grafted NWPE/PP synthetic fabric was used as the functional carrier to anchor nZVI and enhance its spreading and stability. The chemical reduction of nitrate by nZVI-adsorbed NWPE/PP-g-AAc (nZVI-Ads-NWP) fabric was examined in batch experiments at different pH values. At low pH values, the protective layers on nZVI particles can be readily dissolved, exposing the pure iron particles for efficient chemical reduction of nitrate. After about 24 h, at pH 3, almost 96% of nitrate was degraded, suggesting that this reduction process is an acid-driven, surface-mediated process. The nZVI-water interface has been characterized by the 1-pK Basic Stern Model (BSM). An Eley-Rideal like mechanism well described the nitrate reduction kinetics. In accordance with green technology, the newly synthesized nZVI-Ads-NWP has great potential for improving nitrate reduction processes required for the drinking water industry.

Gamma scanning and radiotracer applications are very effective and inexpensive tools to understand and optimize the process as well as troubleshoot the various types of problems in many chemical, petrochemical industries and refineries. These techniques are non-invasive; hence, the problems can be pinpointed online, which leads to reduce the downtime, schedule the shutdown and maintenance of the plant equipment, rendering huge economic benefits. In a leading refinery of India, the catalytic cracking unit (CCU) was malfunctioning. It was suspected by the refinery engineers that the catalyst powder was being carried over to the fractionator, which could have led to erosion of the fractionator column internals resulting in their rupture, and consequentially, to the fire hazard. To understand the flow behaviour of the catalyst powder and to ensure the mechanical integrity, catalyst accumulation and choking, both radiotracer study and gamma scanning of the CCU reactor was carried out. The reactor consists of a riser, three primary cyclones and three secondary cyclones. Gamma scanning of the reactor was carried out with the help of an automatic gamma scanner using 1.8 GBq of Co-60 sealed source. Results showed that the catalyst powder was accumulated in one of the secondary cyclones and uneven density distribution was observed in another secondary cyclone. The radiotracer study was carried out using the irradiated catalyst powder as a radiotracer, which contains 0.9 GBq of Na-24. The radiotracer was injected in the reactor through the specially fabricated injection system. Radiation measurement was done using the thermally insulated and collimated NaI(Tl) scintillation detectors located at various strategic locations coupled to a multi-detector data acquisition system. The data were mathematically analysed. It was confirmed that the catalyst powder was accumulated in one of the secondary cyclones with no flow downwards. This resulted in excess powder available to travel along with hydrocarbon towards fractionator. Since the quantity of powder released through the hydrocarbon outlet of CCU was higher than the designed value, the catalyst powder was observed in various zones of the fractionator. Mathematical modelling of the radiotracer data obtained at various locations corroborated the scanning results; also, the flow pattern was obtained. Partially blocked secondary cyclone showed plug flow with recirculation; normal working cyclone had plug flow behaviour and the vortex breaker showed parallel flow.

Rectifier columns are considered to be a critical component in petroleum refineries and petrochemical processing installations as they are able to affect the overall performance of these facilities. It is deemed necessary to monitor the operational conditions of such vessels to optimize processes and prevent anomalies which could pose undesired consequences on product quality that might lead to huge financial losses. A rectifier column was subjected to gamma scanning using a 10-mCi Co-60 source and a 2-inch-long detector in tandem. Several scans were performed to gather information on the operating conditions of the column under different sets of operating parameters. The scan profiles revealed unexpected decreases in the radiation intensity at vapour levels between trays 2 and 3, and between trays 4 and 5. Flooding also occurred during several scans which could be attributed to parametric settings.

The pulp and paper industry is highly dependent on water for most of its processes, producing a significant amount of wastewater that should be treated to comply with environmental standards before its discharge into surface-water reservoirs. The wastewater generated primarily consists of substantial amounts of organic, inorganic, toxic and pathogenic compounds in addition to nutrients, which are treated in an effluent treatment plant that often combines primary, secondary, tertiary and advanced treatments. However, the treatment methods vary from industry to industry according to the process utilized. The effective performance of effluent treatment plants is crucial from both environmental and economic points of view. Radiotracer techniques can be effectively used to optimize performance and detect anomalies like dead zones, bypassing, channelling, etc. in wastewater treatment plants. Experiments on the distribution of residence time were performed on the aeration tank and secondary clarifier of a full-scale pulp and paper mill to study the flow behaviour as well as locate system anomalies and hence evaluate the performance of the treatment plants using the radiotracer I-131. The convolution method was applied to model the system with an imperfect impulse radiotracer input. The aeration tank was working efficiently in the absence of any dead zones or bypassing. Various hydrodynamic models available in the literature were applied on the aeration tank and secondary clarifier to obtain the hydraulic representation of the systems.

The present work is a contribution to rescue the history of development of the application of ^99mTc, widely used in nuclear medicine, to its use as tracer for the study of the transport of fine sediment in suspension, in water environment. It addresses the usefulness of its application in obtaining important parameters in environmental studies, illustrating them with some applications already performed and the results obtained. This kind of study, when associated with information on hydrodynamic parameters, for example, river, tidal, wind and wave currents, are powerful tools for the understanding and quantification of fine sediment transport in suspension. Fine sediment is an important vector in the transportation of heavy metals, organic matter and nutrients in water environment, and the quantitative knowledge of its behaviour is mandatory for studies of environmental impacts. Fine sediment labelled with ^99mTc, can also be used to study the effect of human interventions, such as dredging of reservoirs, access channels and harbours, and the dumping of dredged materials in water bodies. Besides that, it can be used to optimize dredging works, evaluating the technical and economic feasibility of dumping sites and their environmental impact. It is a valuable support in the calibration and validation of mathematical models for sediment dynamics.

An automatic control system is one of the most important parts of an irradiation facility. The level of this control is always maintained to comply with safety procedures during routine work in this field. Also sometimes it is limited to the minimum level of regulation required due to economical aspects; some commercial systems are generally made by manufacturers of industrial facilities and considered affordable by irradiators. In some cases specific irradiation facilities tailor their control systems to their needs. For this kind of irradiator the control system can be developed and upgraded according to personal and industrial experiences. These upgrading procedures are also used by others to develop their systems. The objective of this paper is to share a local experience in upgrading security, safety systems and the use of cobalt-60 for the irradiator. It is a composite experiment at SIBO INRA/Tangier, Morocco and concerns the: (i) upgrade of cobalt-60 in a temporary pool in the SIBO irradiator in Tangier. This operation was conducted in collaboration with the International Atomic Energy Agency (IAEA) and was a success story of 2014 according to the general conference of IAEA; (ii) safety and technical upgrade of the system in the SIBO irradiator made in collaboration with IAEA; (iii) installation and upgrade of the security system in accordance with the Global Threat Reduction Programme (GTRP) to reduce the threat of a Radiological Dispersal Device (RDD) in collaboration with The United States Department of Energy’s National Nuclear Security Administration (NNSA).