Nanotechnology knowledge diffusion: measuring the impact of the research networking and a strategy for improvement

Radiolabelling of industrially manufactured nanoparticles is useful for nanoparticle dosimetry in biodistribution or cellular uptake studies for hazard and risk assessment. Ideally for such purposes, any chemical processing post production should be avoided as it may change the physico-chemical characteristics of the industrially manufactured species. In many cases, proton irradiation of nanoparticles allows radiolabelling by transmutation of a tiny fraction of their constituent atoms into radionuclides. However, not all types of nanoparticles offer nuclear reactions leading to radionuclides with adequate radiotracer properties. We describe here a process whereby in such cases nanoparticles can be labelled with ⁷Be, which exhibits a physical half-life of 53.29 days and emits γ-rays of 478 keV energy, and is suitable for most radiotracer studies. ⁷Be is produced via the proton-induced nuclear reaction ⁷Li(p,n)⁷Be in a fine-grained lithium compound with which the nanoparticles are mixed. The high recoil energy of ⁷Be atoms gives them a range that allows the ⁷Be-recoils to be transferred from the lithium compound into the nanoparticles by recoil implantation. The nanoparticles can be recovered from the mixture by dissolving the lithium compound and subsequent filtration or centrifugation. The method has been applied to radiolabel industrially manufactured SiO₂ nanoparticles. The process can be controlled in such a way that no alterations of the ⁷Be-labelled nanoparticles are detectable by dynamic light scattering, X-ray diffraction and electron microscopy. Moreover, cyclotrons with maximum proton energies of 17–18 MeV that are available in most medical research centres could be used for this purpose.     

Confinement and migration of radionuclides in a nuclear waste deep repository

The safety of the geological disposal of nuclear waste is evaluated, among other factors, through the ability of radionuclides to be confined, first by waste packages then by engineered barriers and host rocks. Deep underground conditions favour the immobilisation of most radionuclides by sorption or precipitation, which means that mobile radionuclides, such as ¹²⁹I or ³⁶Cl, may contribute to most of the ultimate dose release during up to a million years. However, degraded evolution scenarios must be taken into account (oxygen intrusion, faults, …) to assess earlier dose releases. To cite this article: P. Toulhoat, C. R. Physique 3 (2002) 975–986.     

SRIM and FLUKA simulation for target design

ABSTRACT

The increasing demand for radionuclides in nuclear medicine requires optimised production strategies. This study investigates whether any strategy is able to predict radionuclide production yields with simulations using the Monte Carlo code FLUKA. In further studies on the nuclear reaction ⁸⁹Y(p,n)⁸⁹Zr FLUKA results are compared with experimental data. In general, there is good agreement between both. Discrepancies typically can be explained by experimental details and problems.     

The study of the nuclear reactions for the production of antimony isotopes

Nuclear reactions using proton beams and tin targets are studied in order to obtain antimony radionuclides. A new target system that includes on-line monitoring of target heating is used. To determine the parameters of proton beams, experimental studies on nuclear reactions are performed using Ti, Cu and stainless steel targets. Using modern model approximations, cross sections are determined for the formation of radionuclides ¹¹⁹Sb and ¹¹⁷Sb in the investigated nuclear reactions.     

Radiochemical studies in the development of deep geological repository in the Czech Republic

In this contribution the main achievements of radiochemical studies performed within the framework of the Czech DGR development programme are summarized and further plans outlined. The results of selection of the most dangerous radionuclides in spent fuel assemblies from VVER 440 reactors, based on spent fuel inventory calculations and analyses of migration rate of radionuclides to the environment, are presented in the first part of the contribution. It is shown that ¹⁴C, ¹²⁹I, ¹²⁶Sn, ¹³⁵Cs, ³⁶Cl, ⁷⁹Se, ²²⁶Ra, ²³⁷Np, ²²⁹Th, and ²⁴²Pu belong among the most dangerous radionuclides in the Czech disposal concept. Problems with the determination of migration parameters of radionuclides are described in the second part of this contribution.     

Radiochemical studies in the development of deep geological repository in the Czech Republic

In this contribution the main achievements of radiochemical studies performed within the framework of the Czech DGR development programme are summarized and further plans outlined. The results of selection of the most dangerous radionuclides in spent fuel assemblies from VVER 440 reactors, based on spent fuel inventory calculations and analyses of migration rate of radionuclides to the environment, are presented in the first part of the contribution. It is shown that ¹⁴C, ¹²⁹I, ¹²⁶Sn, ¹³⁵Cs, ³⁶Cl, ⁷⁹Se, ²²⁶Ra, ²³⁷Np, ²²⁹Th, and ²⁴²Pu belong among the most dangerous radionuclides in the Czech disposal concept. Problems with the determination of migration parameters of radionuclides are described in the second part of this contribution.     

Characteristics of radionuclide contamination of different zones of Semipalatinsk Nuclear Test Site “Opytnoe pole”

Data on the spatial distribution of radionuclides (²⁴¹Am, ²³⁹Pu, ¹³⁷Cs and ¹⁵²Eu) formed during nuclear explosions of different types near P2 SNTS test site are presented. Radionuclide contamination induced by the explosions varies in the concentrations of individual radionuclides, their proportions and species. Examination of the variations is a crucial task to plan remediation activities as well as those aimed at decrease of radiation risk for population and prevention of repeated contamination. Concentrations of ²⁴¹Am and ^239+240Pu that are the most toxic radionuclides in the area lie in hundred thousands of Bqkg^?1. The most contaminated areas are classified by the radionuclide concentration, ratio and form present in soil.     

A new code for modelling the near field diffusion releases from the final disposal of nuclear waste

The canisters with spent nuclear fuel produced during the operation of WWER reactors at the Czech power plants are planned, like in other countries, to be disposed of in an underground repository. Canisters will be surrounded by compacted bentonite that will retard the migration of safety-relevant radionuclides into the host rock. A new code that enables the modelling of the critical radionuclides transport from the canister through the bentonite layer in the cylindrical geometry was developed. The code enables to solve the diffusion equation for various types of initial and boundary conditions by means of the finite difference method and to take into account the non-linear shape of the sorption isotherm. A comparison of the code reported here with code PAGODA, which is based on analytical solution of the transport equation, was made for the actinide chain 4N+3 that includes ²³⁹Pu. A simple parametric study of the releases of ²³⁹Pu, ¹²⁹I, and ¹⁴C into geosphere is discussed.     

球床高温气冷堆燃料颗粒中放射性核素的累积释放份额研究

本文利用Fick扩散定律,给出经典方法和改进的两种累积释放份额的严格数学表达式,并分析与之相关的穿透时间的物理内涵,并分别用以上两种方法计算137Cs,90Sr,110mAg三种重要放射性核素通过SiC层扩散的累积释放份额.研究表明,传统的"穿透时间"概念并非放射性核素释放到SiC层外的时间,本文提出的改进方法可以更准确的描述放射性核素在燃料元件中的输运和扩散行为.     

The determination of the rate of conjugation immunoglobuline with bifunctional chelator

The work was performed under the GACR project: „Technology of preparation of radionuclides and their labelled compounds for nuclear medicine and pharmacy with the use of the reactor LVR-15“ reg. no. 104/03/0499. Imaging of cell’s antigens with the use of labelled immunoglobulines allows imaging of specific receptors on cell membrane and specific tumours. It is necessary to carry out the labelling of the immunoglobulines with radionuclides of suitable physical properties, which form cations (e.g., ¹¹¹In, ⁹⁰Y, ¹⁷⁷Lu) that form very strong chelates of sufficiently high stability constant preventing the dissociation of complexes or the radionuclide under “in-vivo” conditions. The immunoglobuline must be conjugated with the bifunctional chelator (BCH), which contains both chelating unit and reactive group for binding to the immunoglobuline. In our laboratory we have conjugated human IgG and monoclonal antibody CD20 with diethylenetriamine pentaacetic acid dianhydride (cDTPAA). Radionuclides ⁹⁰Y and ¹⁷⁷Lu prepared on the LVR-15 reactor in NRI Rez were used for labelling. After conjugation and labelling the yields in relation to the amount of isotopic carrier have been determined.     

Studies of natural radionuclides and dose estimation from soil samples of Kumaun Himalaya, India

In the present study, the distribution of natural radionuclides in soil samples collected from different geological units of Kumaun Himalayas are assessed using gamma ray spectrometer with Nal(Tl) detector. The naturally occurring radioactivity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K were found to vary from 36.4 Bq/kg to 166.6 Bq/kg, 15.3 Bq/kg to 94.7 Bq/kg and 645.9 Bq/kg to 1378.9 Bq/kg, respectively. The total absorbed gamma dose rate was found to vary from 80 nGy/h to 179.6 nGy/h. The resulting dose due to the presence of these radionuclides was estimated from radiation protection point of view. The significance of this investigation is also discussed in details.     

Assessment of natural radioactivity in rice and their associated population dose estimation

ABSTRACT

The concentration of natural radioactivity in rice is an important parameter for the determination of population exposure by the ingestion of natural radionuclides during habitual consumption of food. All types of food including rice contain a detectable amount of natural radioactivity which successively relocate into the human body via the ingestion pathway. Rice is the main cultivated crop in Bangladesh and most of the Bangladeshi people consume rice as their staple food. Hence, studies on the evaluation of natural radioactivity in rice have been performed by gamma-ray spectrometry using High Purity Germanium (HPGe) detector in order to estimate various radiation hazards due to rice consumption. The average activity levels of natural radionuclides ²²⁶Ra, ²²⁸Ra and ⁴⁰K in the rice samples were 1.09?±?0.31, 0.17?±?0.21 and 4.70?±?1.59?Bq?kg^?1, respectively. The estimated effective doses for the respective radionuclides caused by the rice consumption were 43.69, 16.39 and 4.15?µSv?y^?1, respectively which was below the UNSCEAR compiled value. The calculated excess lifetime cancer risk (ELCR) values via rice consumption were found below the acceptable limit of 0.29?×?10^?3 for radiological risk.     

The production and isolation of Cu-64 and Cu-67 from zinc target material and other radionuclides

A two-stage method is described for the purification of Cu radionuclides from up to 5 g of ^natZn and other radionuclides. After proton bombardment, co-produced ^66,67Ga is removed by passing the dissolved zinc in 7 M HCl through a 2.5 ml column of AmberChrom CG-71, a methacrylate-based polymeric resin. This first column eluate, which contains ⁶⁵Zn, ^64,67Cu, and ^56,57,58Co, is taken to incipient dryness and reconstituted in 300 ml 0.05 M HCl. This solution is then pumped through a novel 10 ml column of dithizone impregnated AmberChrom CG-71, where Cu radionuclides are efficiently retained with no breakthrough. Zinc and Co radionuclides elute smoothly during washing with no tailing. More than 97% Cu is eluted by washing with 40 ml 5 M HNO₃ warmed to 50 °C. No dithizone is detected in this eluate.     

Health and ecological hazards due to natural radioactivity in soil from mining areas of Nasarawa State,Nigeria

Nasarawa State is located in north central Nigeria and it is known as Nigeria's home of solid minerals. It is endowed with barite, copper, zinc, tantalite and granite. Continuous releases of mining waste and tailings into the biosphere may result in a build-up of radionuclides in air, water and soil. This work therefore aims to measure the activity concentration levels of primordial radionuclides in the soil/sediment samples collected from selected mines of the mining areas of Nasarawa State. The paper also assesses the radiological and radio ecological impacts of mining activities on the residents of mining areas and their environment. The activity concentrations of primordial radionuclides (²²⁶Ra, ²³²Th and ⁴⁰K) in the surface soils/sediment samples were determined using sodium iodide-thallium gamma spectroscopy. Seven major mines were considered with 21 samples taken from each of the mines for radiochemistry analysis. The human health hazard assessment was conducted using regulatory methodologies set by the United Nations Scientific Committee on the Effects of Atomic Radiation, while the radio ecological impact assessment was conducted using the ERICA tool v. 1.2. The result shows that the activity concentrations of ⁴⁰K in the water ways of the Akiri copper and the Azara barite mines are 60 and 67?% higher than the world average value for ⁴⁰K, respectively. In all mines, the annual effective dose rates (mSv y^?1) were less than unity, and a maximum annual gonadal dose of 0.58 mSv y^?1 is received at the Akiri copper mine, which is almost twice the world average value for gonadal dose. The external hazard indices for all the mines were less than unity. Our results also show that mollusc-gastropod, insect larvae, mollusc-bivalve and zooplankton are the freshwater biotas with the highest dose rates ranging from 5 to 7 µGy h^?1. These higher dose rates could be associated with zinc and copper mining at Abuni and Akiri, respectively. The most exposed terrestrial reference organisms are lichen and bryophytes. In all cases, the radio ecological risks are not likely to be discernible. This paper presents a pioneer data for ecological risk from ionizing contaminants due to mining activity in Nasarawa State, Nigeria. Its methodology could be adopted for future work on radioecology of mining.     

Cesium,americium and plutonium isotopes in ground level air of Vilnius

Systematic observations of radionuclide composition and concentration in the atmosphere have been carried out at the Institute of Physics in Vilnius since 1963. Increases in activity concentration of radionuclides in the atmosphere were observed after nuclear weapon tests and the Chernobyl NPP accident. At present the radiation situation in Lithuania is determined by two main sources of radionuclides, forest fire and resuspension products transferred from highly polluted region of the Ukraine and Belarus. The activity concentrations of ¹³⁷Cs were measured in two to three days samples while plutonium and americium in monthly samples. The extremely high activity concentrations of ²³⁸Pu, ^239,240Pu, ²⁴¹Am determined in the atmosphere during the Chernobyl accident can be explained by transport of “hot particles” of different composition. Activity concentration in 1995–2003 of ²⁴¹Am and ^239,240Pu isotopes ranged from 0.3 to 500 and from 1 to 500 nBq/m³, respectively. ²³⁸Pu/^239,240Pu activity ratio in measured samples differs from 0.03 to 0.45. A decrease in ²⁴⁰Pu/²³⁹Pu atomic ratio from 0.30 to 0.19 was observed in 1995–2003.     

Cesium, americium and plutonium isotopes in ground level air of vilnius

Systematic observations of radionuclide composition and concentration in the atmosphere have been carried out at the Institute of Physics in Vilnius since 1963. Increases in activity concentration of radionuclides in the atmosphere were observed after nuclear weapon tests and the Chernobyl NPP accident. At present the radiation situation in Lithuania is determined by two main sources of radionuclides, forest fire and resuspension products transferred from highly polluted region of the Ukraine and Belarus. The activity concentrations of ¹³⁷Cs were measured in two to three days samples while plutonium and americium in monthly samples. The extremely high activity concentrations of ²³⁸Pu, ^239,240Pu, ²⁴¹Am determined in the atmosphere during the Chernobyl accident can be explained by transport of “hot particles” of different composition. Activity concentration in 1995–2003 of ²⁴¹Am and ^239,240Pu isotopes ranged from 0.3 to 500 and from 1 to 500 nBq/m³, respectively. ²³⁸Pu/^239,240Pu activity ratio in measured samples differs from 0.03 to 0.45. A decrease in ²⁴⁰Pu/²³⁹Pu atomic ratio from 0.30 to 0.19 was observed in 1995–2003.     

Radioactive ion beams for biomedical research and nuclear medical application

In this article a review is given on the research strategies, on experimental work and application of ISOLDE produced radionuclides used in the field of biomedicine over a period of more than 2 decades. Special attention will be directed to the radio-lanthanides for several reasons: firstly, the radio-lanthanides are three-valent metallic radionuclides which show any radiation properties we wish (single photon emission suitable for SPECT, positron emission suitable for PET, β⁻- and Auger electron emission suitable for therapy). Even the alpha decay mode (suitable for therapy in selected cases) is available in the lanthanide group. Secondly, the 15 lanthanides can be seen chemically as one single element for labelling of tracer molecules, providing the unique possibility to study systematically relationships between physico-chemical molecule parameter and a biological response without changes in the basic tracer molecule. Very recent developments in bioconjugation chemistry call for three-valent metallic radionuclides for all kinds of nuclear medical application: diagnosis, in vivo dosimetry and radionuclide therapy where the rare-earth elements will play an important role in future. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of salinity on the concentrations of radioisotopes in the aquatic environment of a hypersaline coastal lagoon

Research of the effect of salinity on the fate of radionuclides has been focused on seas or estuarine systems while there is almost no information on marine environments with a salinity higher than that of sea water. The hypersaline Bardawil lagoon is a concentration basin, with evaporation exceeding precipitation. This study presents the characteristics of some environmental factors including salinity and their influence on the distribution of natural and artificial radionuclides in different compartments of the lagoon. The concentrations of ²³⁸U, ²³⁴Th, ²²⁸Ra and ¹³⁷Cs in sediments show some degree of dependency on the water's salinity. Migration of these radionuclides in the lagoon's sediments must take place from high salinity to low-salinity regions. Cluster analysis revealed the data structure for sediment by separating ¹³⁷Cs and ⁴⁰K from ²³²Th, ²²⁶Ra, and ²³⁴Th and for sand by separating ⁴⁰K from the other radioisotopes.     

Radiochemical separation methods for preparation of biomedical cyclotron radionuclides

A short review of the radiochemical methods for preparation of widely used or promising cyclotronproduced radionuclides for nuclear medicine and biomedical or environmental studies is given. The presented data include the current status of the production of some gamma-emitters (⁹⁷Ru, ¹¹¹In, ¹²³I, ²⁰¹Tl), generator-pairs (⁶⁸Ge/⁶⁸Ga, ⁸²Sr/⁸²Rb, ¹²⁸Ba/¹²⁸Cs, ¹⁷⁸W/¹⁷⁸Ta), radioisotopes for metabolism studies (²⁶Al, ⁶⁷Cu, ²³⁷Pu) and actinides tracers for environmental researches (²³⁵Np, ²³⁶Np, ²³⁶Pu). The conditions for preparation of high-purity isotopes have been investigated and procedures including target chemistry design were developed.     

Distortion effects in light hypernuclei

We have studied the particle-bound levels in the hypernuclei_Λ ^3,4H,_Λ ⁵He,_Λ ⁸Li and_Λ ^8,9Be in the framework of the full microscopic Resonating Group Method (RGM). In a first step we have solved the respective nuclear many-body problem within the RGM. For each hypernucleus we have then performed a static calculation, in which the nuclear degrees of freedom were kept fixed, and a dynamical calculation in which nuclear degrees of freedom were allowed to vary. The differences between these two studies allowed us to investigate nuclear distortion effects caused by the presence of theΛ-particle. We find the nuclear distortion effects to be inverse proportional to the binding of the nuclear constituents. Thus, the strongest effects are observed for_Λ ³H and for_Λ ⁹Be. Our dynamical approach does not show the strong overbinding of_Λ ³H and_Λ ⁹Be as reported in other cluster model studies. Our results for thep-shell hypernuclei agree reasonably well with those obtained in a semi-microscopic Orthogonal Condition Model (OCM) study which used the same effectiveΛN-interaction as employed in our calculation.