Volume 100, Issue 8-9 - Special Jubilee Issue

This paper provides a brief account of the development of this journal over the last fifty years. Having started in 1962 as a modest outlet for reporting research results in radiochemistry, Radiochimica Acta soon became a respected specialist journal. There has been long-term continuity both in editorial activity and publishing management, resulting in welldefined publishing policies. Starting with the Founding Editors, the Board of Editors was changed only in 1977 and 1996. Similarly the original Publisher, Akademischer Verlag, published the journal until 1983. Since then OldenbourgWissenschaftsverlag has been managing the publication process. The journal has been broad-based, encompassing all chemical aspects of nuclear science and technology. It has played a significant role in the dissemination of new knowledge, occasionally by bringing forth special issues in fast emerging areas. It has kept pace with the changing trends in worldwide radiochemical research. Whereas by about the middle of 1980s all areas of radiochemistry were equally represented, today the emphasis is more on applied topics, such as chemical behaviour and mobility of actinides and fission products, accelerator-based radiochemistry, medical applications of radioactivity, etc. The number of published scientific contributions to date amounts to about 5100, covering about 30 000 printed pages. The total number of authors is around 7000. The journal follows a strict peer-review system and is supported by a network of about 400 referees. About 200 manuscripts are received per year, out of which 30-35% are rejected. The impact factor (IF) of the journal is almost the highest among the radiochemistry related journals, and the cited half-life (CHL) among the highest of all chemistry and physics oriented journals. In short, today Radiochimica Acta is a well established, internationally recognised periodical. Presently, approximately 50 percent of the published contributions originate from Europe, 25 percent fromNorth- and South America and the remaining 25 percent from Asia, Australia and Africa together. All articles are published in English, and the journal is available to readership both on-line and in printed form.

The nuclear sector in the UK operates under regulation requiring assurance that the quality of radioactive measurements is “fit for purpose”. Laboratories operate a quality system under ISO 17025:2005 which is monitored by the United Kingdom Accreditation Service. Few of the test methods used in UK laboratories are based on standard methods so non-standard procedures are validated through the use of certified reference materials, and continued quality assurance is provided through participation in proficiency testing and interlaboratory comparison exercises. The majority of organisations accredited for radioactivity measurements under ISO 17025:2005 in the UK are environmental monitoring laboratories routinely processing soils, vegetation, air filters and water samples. There are no certified reference materials available in the UK or elsewhere adequately supporting the work of these laboratories. The same is true for the nuclear decommissioning and waste management community that regularly analyses concrete, soil, brick, sludge and oils for activities at Low Level Waste and Intermediate Waste Levels. The nuclear sector has a number of issues regarding availability of isotopic tracers for analysis, supplies of material for nuclear medicine, proficiency testing exercises involving representative matrices and activity levels but the most pressing need is in the area of certified reference materials for validation of methods analysing alpha, beta, and gamma emitting radionuclides.

In 1996 the Editors of Radiochimica Acta brought out a special volume of the journal to celebrate the hundredth anniversary of the discovery of radioactivity [1]. On the occasion of the 50 th anniversary of Radiochimica Acta, which follows closely upon the centenary of Marie Curie’s second Nobel Prize in 1911, the author has the privilege to informally review “Radiochemistry and Nobel Prize Awards”, including discoveries of radioelements and new fields in chemistry based on radiochemical methods.

In the early history of radiochemistry in Japan Yoshio Nishina and Kenjiro Kimura were internationally known for their discovery of symmetric nuclear fission of uranium. They also succeeded in getting U-237, which is an (n+1) series (neptunium series) nuclide, from U-238 by fast neutron irradiation. Kimura was an excellent leader of the radiochemical analysis of Bikini ashes in 1954. The results of that analysis contributed to the improvement of environmental radioactivity in the world. A tragic story of Nobuo Yamada working at the Radium Institute is related. The start of radiochemistry symposia in Japan is described.

Nuclear and radiochemistry is one of the frontier areas of chemistry with high impact on national security, energy supply, scientific advances, social and economic development. Nuclear and radiochemistry in China is now experiencing a renaissance, which is being strongly motivated by China’s huge demand for nuclear energy. With this in review, the progress in nuclear and radiochemistry of China is selectively addressed. Some hot topics have been summarized and the main research results achieved by Chinese scientists in this field are highlighted, with emphasis on the basic nuclear chemistry, actinide and trans-actinide chemistry, chemistry of spent nuclear fuel reprocessing, radioanalytical chemistry, environmental radiochemistry and radiopharmaceutical chemistry, etc. Some measures about how to promote the radiochemical education and research in China are suggested, and future perspectives are briefly outlined as well.

Radiochemistry in India essentially blossomed under the auspices of the Department of Atomic Energy (DAE) for the last 55 years or so. Major activities in this area are centred at Bhabha Atomic Research Centre, Mumbai (BARC) and Indira Gandhi Centre for Atomic Research, Kalpakkam (IGCAR). Though there were several centers of excellence which were established by renowned radiochemists during the 1960s at the academic institutions in different parts of the country and nurtured by their close associates during the eighties and nineties, their glamour did not last long and only very few have sustained the challenges presented by social and technological upheaval of last five decades. Board of Research in Nuclear Sciences (BRNS), an organ of DAE has been in the forefront for promotion of education and research in nuclear sciences at academic institutions. It sponsors symposia in Nuclear and Radiochemistry (NUCAR), Nuclear Analytical Chemistry (NAC) and Applications of Radioisotopes in Chemistry, Environment and Biology (ARCEB) which are organized periodically to provide a platform for interaction of the radiochemists within and outside DAE. A professional body, viz. Indian Association of Nuclear Chemists and Allied Scientists (IANCAS), formed in early eighties at BARC, Mumbai has been spearheading the campaign to popularize the subject of radiochemistry in schools and colleges through workshops and publishing monographs and thematic bulletins regularly in the area of interest to the radiochemists. During the last five decades, radiochemistry programme at BARC has centered around attaining excellence in basic research utilizing radiations and radioisotopes to unravel various nuclear and chemical phenomena, related to actinides and fission products. This programme encompassed a number of research and development areas such as nuclear fission, nuclear reactions, nuclear probes for materials study, nuclear and chemical properties of actinides, actinide spectroscopy, separation science of actinides, thermodynamics and characterization of fuels, post irradiation examination, chemical and non destructive assay techniques for nuclear materials. Production and application of radioisotopes in societal benefit activities in agriculture, industry and health science was another facet of the radiochemistry programme at BARC. The radiochemistry programme at IGCAR has been focused on chemistry of fast reactor and fuel cycle related materials such as sodium and boron, in addition to the chemistry of actinides, fission products and pyrochemical studies related to processing of spent fuels. Publication of about 2000 peer reviewed papers in international journals of repute and award of Ph.D. degrees to more than 150 scientists is an evidence of the front line research activities pursued under this programme. All along the 55 years, sustained efforts were made to meet the growing challenges of closed nuclear fuel cycle (both thermal as well as fast). After five decades of continuous research and development perhaps one can feel satisfied that the programme could fulfil not only the dreams of its founders but is also ready to take on the future challenges related to the second and third stage of Indian nuclear power programme.

With the inception of Pakistan Atomic Energy Commission (PAEC) in 1956, peaceful uses of atomic energy commenced for the benefit of scientific community as well as masses of Pakistan. Radiochemistry played a vital role right from the beginning. The research and development in this field accelerated soon after the criticality of the first research reactor named as Pakistan Research Reactor (PARR- 1) at the Pakistan Institute of Nuclear Science and Technology (PINSTECH), Islamabad. The first radioisotope produced at PARR-1 for application in nuclear medicine was 131I. Later on, many other radioisotopes were prepared and radiopharmaceuticals were synthesised for their use in industry and hospitals. Besides providing pure radioactive tracers for nuclear medicine, radiochemistry also enhanced the detection limit of impurities at all stages of nuclear fuel cycle for power generation. In 1983, research in the field of nuclear data measurement began. The main aim was to identify suitable conditions for the production of radionuclides for cancer diagnostics, treatment and therapy. With the establishment of a second research reactor (PARR-2) at PINSTECH, research in neutron activation analysis, radioisotope production and separation studies gained more momentum and many research articles were published. Solvent extraction, adsorption and ion-exchange were the main routes of separation in those studies. Separation of heavy metals and treatment of waste generated in a nuclear power plant are other important aspects related to environmental restoration and nuclear waste management, where radiochemistry is required. In future, work in radiochemistry will be continued on similar lines to develop novel radiopharmaceuticals, identify indigenous schemes for nuclear waste management and work out intelligent procedures for material characterization for benefit to mankind, especially the people of Pakistan.

The unique role of the heaviest elements in chemical and physical sciences is discussed. With the actinide series (Z = 90-103) and the superactinide series (Z = 122-155), the heaviest elements have significantly shaped the architecture of the Periodic Table of the elements. Relativistic effects in the electron shells of the heaviest elements change the chemical properties in a given group in a non-linear fashion. Relativistically stabilized sub-shell closures give rise to a new category of elements in the Periodic Table: volatile metals. The prototype for this property is element 114 which, due to the relativistic stabilization of its 7s2 7p 2 1/2 electron configuration, is volatile in its elementary state, but, in contrast to a noble gas, exhibits a marked metalmetal interaction with a gold surface at room temperature. Nuclear shell effects dominate the physical properties of the transuranium elements. These give rise to superdeformed shape isomers (fission isomers) in the actinides (U-Bk). Superheavy elements (Z ≥ 104) owe their existence solely to nuclear shell effects at N = 152, 162, and 184. At this time, a building lot is the location of the next spherical proton shell closure as there is evidence that the center of the “island of stability” is not at Z = 114. This needs urgently further theoretical and experimental efforts. The cross sections for the syntheses of elements 119 and 120 will give us important information on the “upper end of the Periodic Table of the elements”.

The chemistry of superheavy elements - or transactinides from their position in the Periodic Table - is summarized. After giving an overview over historical developments, nuclear aspects about synthesis of neutron-rich isotopes of these elements, produced in hot-fusion reactions, and their nuclear decay properties are briefly mentioned. Specific requirements to cope with the one-atom-at-a-time situation in automated chemical separations and recent developments in aqueous-phase and gas-phase chemistry are presented. Exciting, current developments, first applications, and future prospects of chemical separations behind physical recoil separators (“pre-separator”) are discussed in detail. The status of our current knowledge about the chemistry of rutherfordium (Rf, element 104), dubnium (Db, element 105), seaborgium (Sg, element 106), bohrium (Bh, element 107), hassium (Hs, element 108), copernicium (Cn, element 112), and element 114 is discussed from an experimental point of view. Recent results are emphasized and compared with empirical extrapolations and with fully-relativistic theoretical calculations, especially also under the aspect of the architecture of the Periodic Table.

Experimental verification and characterization of the two-mode fission are reviewed. The presence of two independent deformation-paths in low energy fission of actinides is demonstrated by studying correlation among saddle-point configurations, scission-point configurations, and mass-yield distributions; the elongated scission configuration is related with the fission process that goes over a higher threshold energy and results in a symmetric mass-division mode, while the compact scission configuration with the process that experiences a lower threshold ends up with an asymmetric mass-division mode. Based on an extensive systematic analysis of scission properties in a wide range of actinide fission, the bimodal fission observed in the spontaneous fission of the heavy actinides is interpreted as the result of the presence of two fission paths, namely, the ordinary asymmetric fission path and a strongly shell-influenced symmetric mode.

Decay data are commonly used to characterise and quantify radioactive material, and provide an important means of understanding the properties and structure of the nucleus. Experimental measurement techniques are reviewed, with the emphasis placed on recent developments that represent a potential quantum leap in advancing our knowledge, particularly by means of γ-ray spectroscopy. A select number of internationally-accepted decay-data evaluations and compilations are also discussed in terms of their contents. Both energy and non-energy related applications require the input of well-defined decay data, and such activities have been reviewed. Various important decay-data issues are assessed, and note taken of any significant requirements for better quantified data.

Medical radionuclide production technology is well established. Both reactors and cyclotrons are utilized for production; the positron emitters, however, are produced exclusively using cyclotrons. A brief survey of the production methods of most commonly used diagnostic and therapeutic radionuclides is given. The emerging radionuclides are considered in more detail. They comprise novel positron emitters and therapeutic radionuclides emitting low-range electrons and α-particles. The possible alternative production routes of a few established radionuclides, like 68 Ga and 99m Tc, are discussed. The status of standardisation of production data of the commonly used as well as of some emerging radionuclides is briefly mentioned. Some notions on anticipated future trends in the production and application of radionuclides are considered.

Radiometals play an important role in diagnostic and therapeutic radiopharmaceuticals. This field of radiochemistry is multidisciplinary, involving radiometal production, separation of the radiometal from its target, chelate design for complexing the radiometal in a biologically stable environment, specific targeting of the radiometal to its in vivo site, and nuclear imaging and/or radiotherapy applications of the resultant radiopharmaceutical. The critical importance of inorganic chemistry in the design and application of radiometal-containing imaging and therapy agents is described from a historical perspective to future directions.

Successful utilization of medical isotopes in the radiolabeling reactions to a significant degree depends on the technically achievable specific activity. In this respect, the Szilard-Chalmers effect is considered in detail as a radiochemical tool to increase the specific activity of radionuclides produced by direct nuclear reactions. In the present study, a physico-chemical model is described utilizing the specific aspects of thermodynamically and kinetically stabilised metal-ligand complexes. The approach is applied as a proofof- principle study to increase the specific activity of 166 Ho, produced via the (n, γ) nuclear reaction. As a target material, 165 Ho-DOTA is used. In this case, 166 Ho, the product nucleus of the neutron capture reaction, is obtained chemically as non-complexed cationic 166 Ho III species in situ. Consequently, it can effectively and quantitatively be separated from the inactive 165 Ho-DOTA target material by means of fast and simple chromatographic, column-based methods. We were able to verify the physico-chemical model by the experimentally obtained data. For the first time we quantitatively describe the interaction of the ligand-framework of the target material (e.g. the Ho-DOTA complex) with the radiation field of the nuclear reactor. The analysis of the experimental data allows to assume that radionuclides with half-lives of T 1/2 < 64 h can be produced at a TRIGA II nuclear reactor via the Szilard-Chalmers effect with specific activities higher than in the case of direct irradiation of common target materials such as oxides.

Fast chemical separation procedures applied in nuclear research require dedicated experimental techniques. Rapid discontinuous separation procedures are illustrated by an example to isolate technetium from fission products. The use of a gas jet and its combination with a thermochromatographic separation and with the continuous solvent extraction technique SISAK is described and examples are given for the investigation of short-lived fission products. The potential of resonance ionization mass spectrometry (RIMS) as a highly sensitive technique using different experimental systems is outlined for ultra trace analysis of long-lived plutonium and neptunium isotopes, including isotope ratio measurements of the plutonium isotopes. In addition, the precise determination of the first ionization potentials (IP) of ten actinide elements up to einsteinium and of technetium carried out by using the photoionization threshold method and requiring sample sizes of ∼ 10 12 atoms is presented.

The k 0 method is a highly successful standardization method developed for Neutron Activation Analysis (NAA), later also introduced in Prompt Gamma Activation Analysis (PGAA). After the careful calibration of the irradiation and counting facilities, the k 0 method makes the use of elemental standards unnecessary. Masses of the components are determined relative to the flux monitor, or, in the case of PGAA, to other known components of the sample. The development of the method is summarized in this review together with the description of methods implemented at different laboratories. The activities carried out in the laboratories of the authors are described as examples for the successful implementation of the k 0 approach to activation analysis.

Even though chemical processes related to the corrosion of spent nuclear fuel in a deep geological repository are of complex nature, knowledge on underlying mechanisms has very much improved over the last years. As a major result of numerous studies it turns out that alteration of irradiated fuel is significantly inhibited under the strongly reducing conditions induced by container corrosion and consecutive H 2 production. In contrast to earlier results, radiolysis driven fuel corrosion and oxidative dissolution appears to be less relevant for most repository concepts. The protective hydrogen effect on corrosion of irradiated fuel has been evidenced in many experiments. Still, open questions remain related to the exact mechanism and the impact of potentially interfering naturally occurring groundwater trace components. Container corrosion products are known to offer considerable reactive surface area in addition to engineered buffer and backfill material. In combination, waste form, container corrosion products and backfill material represent strong barriers for radionuclide retention and retardation and thus attenuate radionuclide release from the repository near-field.

The selective partitioning (P) of long-lived minor actinides fromhighly active waste solutions and their transmutation (T) to short-lived or stable isotopes by nuclear reactions will reduce the long-term hazard of the high-level waste and significantly shorten the time needed to ensure their safe confinement in a repository. The present paper summarizes the on-going research activities at Forschungszentrum Jülich (FZJ), Karlsruher Institut für Technologie (KIT) and Institute for Transuranium Elements (ITU) in the field of actinide partitioning using innovative solvent extraction processes. European research over the last few decades, i.e. in the NEWPART, PARTNEW and EUROPART programmes, has resulted in the development of multi-cycle processes for minor actinide partitioning. These multi-cycle processes are based on the co-separation of trivalent actinides and lanthanides (e.g. by the DIAMEX process), followed by the subsequent actinide(III)/lanthanide(III) group separation in the SANEX process. The current direction of research for the development of innovative processes within the recent European ACSEPT project is discussed additionally. This paper is focused on the development of flow-sheets for recovery of americium and curium from highly active waste solutions. The flow-sheets are verified by demonstration processes, in centrifugal contactors, using synthetic or genuine fuel solutions. The feasibility of the processes is also discussed.

With the rapid growth of human demands for nuclear energy and in response to the challenges of nuclear energy development, the world’s major nuclear countries have started research and development work on advanced nuclear energy systems in which new materials and new technologies are considered to play important roles. Nanomaterials and nanotechnologies, which have gained extensive attention in recent years, have shown a wide range of application potentials in future nuclear energy system. In this review, the basic research progress in nanomaterials and nanotechnologies for advanced nuclear fuel fabrication, spent nuclear fuel reprocessing, nuclear waste disposal and nuclear environmental remediation is selectively highlighted, with the emphasis on Chinese research achievements. In addition, the challenges and opportunities of nanomaterials and nanotechnologies in future advanced nuclear energy system are also discussed.