A survey of fiber optic sensor technology for nuclear waste tank applications

The need for suitable remote sensors in highly radioactive defense waste storage tanks is discussed. The harsh radiological and chemical tank environment precludes the use of standard sensors because of the need for intrinsically safe systems. Potential sensor systems based on fiber optics technologies suitable for hardening to the tank environment are identified. The need for certification standards for this type of environment is also discussed.     

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采用球形托卡马克(ST)等离子体位形,对氦冷嬗变包层、钠冷嬗变包层、氟锂铍(FLiBe)熔盐冷嬗变包层三种嬗变包层中子学方案进行了初步计算分析,并就各自的中子学特性进行了比较.结果表明,从嬗变长寿命放射性锕系核素237Np的角度考量,FLiBe冷却嬗变包层的嬗变性能最优.对氦冷嬗变包层的计算结果表明,通过改变初装料时237Np在次锕系元素中的成分比例,可使包层在比较长的运行时间(9.62年)内,保持稳定有效增殖系数、稳定功率、稳定产氚率.     

Fuels and targets for transmutation

The major technological aspects of fuels and targets for the transmutation of minor actinides are discussed. The changes in the fuel properties, the effects on the fabrication processes and the irradiation behaviour caused by recycling of minor actinides (compared to conventional uranium-based fuel) are outlined. The most promising developments are identified. To cite this article: R.J.M. Konings, D. Haas, C. R. Physique 3 (2002) 1013–1022.     

Radioactive waste partitioning and transmutation within advanced fuel cycles: Achievements and challenges

If nuclear power becomes a sustainable source of energy, a safe, robust, and acceptable solution must be pursued for existing and projected inventories of high-activity, long-lived radioactive waste. Remarkable progress in the field of geological disposal has been made in the last two decades. Some countries have reached important milestones, and geological disposal (of spent fuel) is expected to start in 2020 in Finland and in 2022 in Sweden. In fact, the licensing of the geological repositories in both countries is now entering into its final phase. In France, disposal of intermediate-level waste (ILW) and vitrified high-level waste (HLW) is expected to start around 2025, according to the roadmap defined by an Act of Parliament in 2006. In this context, transmutation of part of the waste through use of advanced fuel cycles, probably feasible in the coming decades, can reduce the burden on the geological repository. This article presents the physical principle of transmutation and reviews several strategies of partitioning and transmutation (P&T). Many recent studies have demonstrated that the impact of P&T on geological disposal concepts is not overwhelmingly high. However, by reducing waste heat production, a more efficient utilization of repository space is likely. Moreover, even if radionuclide release from the waste to the environment and related calculated doses to the population are only partially reduced by P&T, it is important to point out that a clear reduction of the actinide inventory in the HLW definitely reduces risks arising from less probable evolutions of a repository (i.e., an increase of actinide mobility in certain geochemical situations and radiological impact by human intrusion).     

Magic numbers and low energy nuclear transmutation by protons in host metals

The observed nuclear transmutations by protons or deuterons in host metals at low reaction energies are evaluated. Reaction probabilitiesN(Z) depending on the atomic numberZ show maxima close to the magic numbers with the exception ofZ=20. The exponential decay of the maxima onZ have an incrementZ′=10. Exactly this empirically derived relation fits a sequence of the magic numbers of 3 ⁿ , where the basis value 3 reminds of the threefold scheme of the quarks. Dedicated to Prof. Dr. D. Sc. Drs. h.c. Arthur Sharmann to his 70th birthday, 26 January 1998.     

Prospects for coherently driven nuclear radiation by Coulomb excitation

Possible experiments are discussed in which Coulomb excitation of nuclear isomers would be followed by sequential energy release. The possibility of coherent Coulomb excitation of nuclei ensconced in a crystal by channeled relativistic heavy projectiles is considered. The phase shift between neighbor-nuclei excitations may be identical to the photon phase shift for emission in the forward direction. Thus, the elementary string of atoms may radiate coherently with emission of characteristics nuclear γ rays, and the intensity of the radiation would be increased due to the summation of amplitudes. Mössbauer conditions should be important for this new type of collective radiation, which could be promising in the context of the γ-lasing problem.     

Swedish containers for disposal of spent nuclear fuel and radioactive waste

The purpose of a disposal is to isolate the radioactive waste from man and the environment. If the isolation is broken, the leakage and transport of radioactive substances must be retarded. The package is one of several barriers, used to achieve these two main functions. For short-lived, low and intermediate level waste four standard containers of steel and concrete are used. Spent fuel will be placed in a canister consisting of a pressure-bearing insert of cast nodular iron and an outer corrosion barrier of copper before it is deposited in a deep geological repository. In particular, the development of a high integrity copper canister for the isolation of spent nuclear fuel is described in this paper. To cite this article: T. Hedman et al., C. R. Physique 3 (2002) 903–913.     

The selective separation of 90Sr and 99Tc in nuclear waste using molecular recognition technology products

This paper describes the use of IBC’s AnaLig® Sr-01 and AnaLig® Tc-02 molecular recognition technology products to effectively and selectively separate and recover strontium and technetium from radioactive waste solutions. The use and effectiveness of AnaLig® Sr-01 and AnaLig® Tc-02 are also compared with traditional commonly applied methods using Eichrom’s Sr Resin and TEVA Resin. Different concentrations of Ca²⁺, Ba²⁺, Pb²⁺, and K⁺ interfering ions on Sr²⁺ sorption were tested. Methods for the determination of ⁹⁰Sr and ⁹⁹Tc with emphasis on avoiding so called “matrix effects”, maximizing chemical recoveries, selectivity, minimizing time of analyses and reaching the lowest LLD were modified or developed.     

Transmutation of radioactive nuclear waste — present status and requirement for the problem-oriented nuclear data base

Transmutation of long-lived actinides and fission products becomes an important issue of the overall nuclear fuel cycle assessment, both for existing and future reactor systems. Reliable nuclear data are required for analysis of associated neutronics. The present paper gives a review of the status of nuclear data analysis focusing on the waste transmutation problem.      

Determination of spatial and energy distributions of neutrons in experiments on transmutation of radioactive waste using relativistic protons

The experiments on transmutation of ¹²⁹I and ²³⁷Np using uranium-lead targets surrounded by a paraffin moderator were performed at the Joint Institute for Nuclear Research (JINR, Russia). The targets were irradiated by 1.5 GeV and 7.4 GeV protons at the Synchrophasotron of JINR. In the frame of present work spatial and energy distributions of neutrons on the surface of the paraffin moderator were measured using SSNTD technique. It is shown that measured values of spetral indices do not pretend on the energy of incident protons but depend on the target composition. The presence of the uranium insertion softens neutron spectra.     

Synthesis and sintering of a monazite-brabantite solid solution ceramic for nuclear waste storage

Various geological arguments suggest that monazite can be an interesting waste-form for actinides such as Np, Pu, Cm and Am. We set up a simple procedure for making dense pellets of monazite-brabantite solid-solution ceramics with composition Ca_0.092Th_0.092Ce_0.089La_0.727PO₄. It consists of co-milling CaCO₃, ThO₂, CeO₂, La₂O₃, and NH₄H₂PO₄, 1250 °C calcination, milling, cold-pressing, and sintering at 1450 °C for 4 h. X-ray investigations showed that the reaction scheme from oxides to monazite is complex and involves various P+La-based intermediate compounds. The final density of the the product is around 95% of the theoretical density. The texture is homogeneous with a typical grain of size 5-20 μm. This process is designed to be adapted to hot cells and telemanipulators.     

Basic technology for developing cost-effective thermal waste recycling industry

The advantages of electron-beam treatment of flue gases of industrial and power plants are discussed. The equations of the basic chemical reactions are presented, and a mathematical model of the cleaning process is developed. A conclusion on the self-repayment of this technology was drawn, which opens up new prospects for its implementation.     

Natural radiation sources,including some lessons for nuclear waste management

The average effective dose at the global level is, according to UNSCEAR, estimated to be 2.4 mSv from naturally occurring sources. This average value can be divided as follows: 1.3 mSv associated with radon, 0.39 mSv from cosmic radiation, 0.46 mSv from terrestrial radiation, and 0.23 mSv from internal radiation, radon excluded. These values can vary quite significantly depending on the place of habitation. Despite this large variation, no sound epidemiological study has yet shown the health effects on the most exposed populations, apart from a few studies concerning radon, but in which the predominant role of tobacco is difficult to determine. To cite this article: H. Métivier, C. R. Physique 3 (2002) 1035–1048.     

Spectroscopic investigations on glasses,glass-ceramics and ceramics developed for nuclear waste immobilization

Highly radioactive nuclear waste must be immobilized in very durable matrices such as glasses, glass-ceramics and ceramics in order to avoid their dispersion in the biosphere during their radioactivity decay. In this paper, we present various examples of spectroscopic investigations (optical absorption, Raman, NMR, EPR) performed to study the local structure of different kinds of such matrices used or envisaged to immobilize different kinds of radioactive wastes. A particular attention has been paid on the incorporation and the structural role of rare earths—both as fission products and actinide surrogates—in silicate glasses and glass-ceramics. An example of structural study by EPR of a ceramic (hollandite) irradiated by electrons (to simulate the effect of the β-irradiation of radioactive cesium) is also presented.     

Geomechanics issues related to long-term isolation of nuclear waste

A short review of current geomechanics issues is presented with respect to nuclear waste isolation in salt, clay, granite and volcanic tuff. Mention of the significance of regional seismicity is followed by examination of the importance of the disturbed rock zone (DRZ) in each rock type. To cite this article: C. Fairhurst, C. R. Physique 3 (2002) 961–974.     

Separation of long-lived radionuclides from high active nuclear waste

The management of vitrified high activity waste issued from the reprocessing of spent nuclear fuel is often made questionable by the presence within this waste of long-lived radionuclides (LLRNs). New management scenarios of this waste are under study at the CEA since the beginning of the 1990s, involving the development of separation processes for some LLRNs. Six LLRNs are the targets of these studies; they are: (i) the minor actinides: neptunium, americium and curium; (ii) the fission products: technetium, iodine and caesium. The present paper highlights the main achievements of the research performed at the CEA in this field. To cite this article: C. Madic et al., C. R. Physique 3 (2002) 797–811.     

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.     

Prospects for and problems of using light-water supercritical-pressure coolant in nuclear reactors in order to increase the efficiency of the nuclear fuel cycle

Trends in the development of the power sector of the Russian and world power industries both at present time and in the near future are analyzed. Trends in the rise of prices for reserves of fossil and nuclear fuels used for electricity production are compared. An analysis of the competitiveness of electricity production at nuclear power plants as compared to the competitiveness of electricity produced at coal-fired and natural-gas-fired thermal power plants is performed. The efficiency of the open nuclear fuel cycle and various versions of the closed nuclear fuel cycle is discussed. The requirements on light-water reactors under the scenario of dynamic development of the nuclear power industry in Russia are determined. Results of analyzing the efficiency of fuel utilization for various versions of vessel-type light-water reactors with supercritical coolant are given. Advantages and problems of reactors with supercritical-pressure water are listed.     

Template identification technology of nuclear warheads and components

Template identification technology （TIT） is designed for the scenarios where a batch of disarmed nuclear weapons or components would be dismantled to observe a nuclear disarmament treaty. The core function played by the TIT is to make a judgment on whether the verified item belongs to a certain kind of nuclear weapons or component （NW/NC） or to which kind the verified item belongs. This paper analyses the functions played by the TIT in the process of NW/NC dismantlement, and proposes that two phases would be followed when applying the TIT： firstly to establish NW/NC templates with a sample of size n drawn from a certain kind of disarmament NW; secondly to authenticate NW/NC by means of the TIT. This paper also expatiates some terms related to the concept of the TIT and investigates on the development status of NW/NC TIT based on radiation signatures. The study concludes that the design of template structure is crucial to the establishment of an effective TIT and that starting from different research angles and aiming at the same goal of classification different template structures and corresponding template identification methods can be built up to meet specific identification requirements.