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The back-end of the nuclear fuel cycle: storing and transporting radioactive waste
Published in Peter R. Mounfield, World Nuclear Power, 2017
In managing the radioactive gaseous wastes the requirement is an effective means of capturing those that are particularly toxic or long lived so that they can go into long-term repositories, combined with controlled release of the others to the atmosphere in highly diluted form (Table 12.6). Capture is possible with carbon-14 but not yet with Tritium. Iodine-129 has a half-life of 16 million years and the best that can be done is to control the time, place and manner of dispersion into the biosphere (Figure 12.12). Krypton, which is a noble gas, is being released to the atmosphere in small amounts, but as reprocessing capacities grow the releases from individual plants might have to be restricted, not only to keep the radiation exposure down as far as reasonably retrievable in the local environment but also to avoid an increased accumulation of krypton-85 in the global atmosphere. Techniques to capture krypton are under development at Mol, Belgium, but the task is not easy and in 1988 they were only in the experimental stage.
Radioactivity
Published in Pradyot Patnaik, Handbook of Environmental Analysis, 2017
Iodine forms several radioisotopes, in the mass range 129–135. Among these, iodine-131 has the highest specific activity, 1.24 × 105 Ci/g with a half-life of 8 days. In comparison, iodine-129 has the longest half-life, 1.6 × 107 years. Its specific activity, however, is relatively low, 1.73 × 10−4 Ci/g. The radioisotopes of this element are produced as fission products in nuclear tests or released during use and processing of fuels in nuclear reactors. Iodine-131 is found in the environment. Exposure can cause thyroid cancer. Iodine-131 in aqueous samples can be measured by three different methods; one is precipitation, while the other two are ion-exchange and distillation methods. These methods are discussed above under other radioisotopes. The detection limit of measuring 1 pCi iodine-131 per liter sample can be achieved by all these methods.
Mineral Resources, Pollution Control, and Nanotechnology
Published in Stephen L. Gillett, Nanotechnology and the Resource Fallacy, 2018
A different approach to redox-switched binding is through electrochemically switched intercalation and release of ions into an open crystal structure. Under the name”electrically switched ion exchange” (ESIX), this has attracted much recent attention, especially for cesium ion (Cs+) extraction. That system is based on an electrode coated with cesium nickel hexacyanoferrate (CsNiFe (CN)6)48 which has the perovskite structure with cyanide ions replacing oxygen ions (Box 5.10), and with only half of the large cavities occupied. On reduction of some of the iron atoms from Fe3+ to Fe2+, the cesium cation is preferentially drawn into the remaining large cavities to maintain charge balance. This intercalation is surprisingly selective even in the presence of other singly charged cations like sodium (Na+), typically an abundant background ion. Reoxidizing the Fe2+ on the electrode by reversing the potential expels the intercalated cesium. As the isotope 49Cs, which is both highly radioactive and has a half-life Just long enough (about 30 years) to remain a hazard for decades, is of great concern in fission waste, the motivation for selective cesium removal at low concentrations is obvious. Another system simultaneously extracts iodide (I-) by including in addition an electrode functionalized with polypyrrole.37 Long-lived iodine-129 (129I, t1/2 ≈ 15.7 million years) is another fission product of great concern as an environmental contaminant.
Application of silica gel to immobilise iodine waste by low-temperature sintering
Published in Philosophical Magazine Letters, 2021
Guilin Wei, Xiaoyan Shu, Zhentao Zhang, Wenhong Han, Fen Luo, Yi Liu, Jingjun Yang, Bingsheng Li, Yi Xie, Lan Wang, Xirui Lu
The development of nuclear energy inevitably generates radioactive iodine waste [1], such as iodine-129, which must be safely managed on account of its long half-life (1.6 × 107 years) [2–4]. Glass-solidification technology is commonly used in the management of radioactive waste [5]. However, some radioactive wastes are volatile at high temperatures, such as I2 (melting point 113.8°C) and AgI (melting point 558°C) [2, 6], which makes the immobilisation process of traditional high-temperature glass much more difficult. Therefore, low-sintering temperature glass has been applied to immobilise iodine waste. Garino et al. [7] mixed low-sintering-temperature glass powder with silver-coated zeolite-doped iodine at 550°C to form a dense waste form. Yang et al. [8] investigated the glass of bismuth–phosphate–zinc oxide, which enabled the immobilisation of iodine waste forms at low-sintering temperatures (600–650°C). Nevertheless, a silicate-based material, namely B2O3–Bi2O3–ZnO–SiO2, is rarely used to immobilise iodine waste, which is mainly due to the high melting point (∼1600°C) [9]. In our previous studies [10, 11], the role of B2O3 in B2O3–Bi2O3–ZnO–SiO2 and B2O3–Bi2O3–ZnO materials was investigated. Based on these results, it was found that 50 mol% of B2O3 is suitable to immobilise iodine waste at low-sintering temperatures.
Examining Practical Application Feasibility of Bismuth-Embedded SBA-15 for Gaseous Iodine Adsorption
Published in Nuclear Technology, 2020
Seong Woo Kang, Jae-Hwan Yang, Man-Sung Yim
However, one major disadvantage of using silver-exchanged zeolites is that a significant portion of the captured iodine may become re-volatilized as time passes. Part of the captured iodine is chemisorbed in the form of silver iodide (AgI), which has low solubility and low volatility, but another significant portion of the adsorbed iodine is physisorbed, which may become re-volatilized.17,18 The longest radioactive isotope of iodine, 129I, has a half-life of 15.7 million years, and another important isotope of iodine, 131I, has a half-life of 8 days. Thus, the materials used for iodine sorption in the nuclear industry should ideally have a lower possibility of re-volatilization as time passes.
Vertical distributions of Iodine-129 and iodide in the Chukchi Sea and Bering Sea
Published in Journal of Nuclear Science and Technology, 2020
Kazuji Miwa, Hajime Obata, Takashi Suzuki
Iodine-129 (129I) is one of iodine’s radioisotopes, and currently, most 129I present in the environment is anthropogenic. Large amounts of 129I have been released into the environment via nuclear weapon tests in/below the atmosphere and reprocessing of nuclear fuel. The amount of 129I in seawater has been increasing by nuclear usage since the 1940s. A total preanthropogenic mass of 129I is estimated at only 130 kg [1]. Aboveground nuclear weapons testing, which peaked in the 1960s, introduced between 50 and 130 kg of 129I into the stratosphere, which eventually found its way into the hydrosphere [2–4]. Anthropogenic 129I released into the environment from nuclear fuel reprocessing plants is mainly transported to the northern hemisphere [1, 5, 6]. These nuclear reprocessing sites have significant impact on 129I in environment, introducing 5401 kg of 129I into atmosphere and ocean. Almost 90% of 5401 kg has been released by Sellafield (UK) and La Hague (France) [1]. In Europe, ocean currents carry iodine toward the northeast from the major points of release, primarily liquid emissions from Sellafield and La Hague [1]. It is reported that 129I which was released from nuclear reprocessing plant as liquid emissions reached Canada Basin via Arctic Ocean [7]. Some of 129I released from Sellafield and La Hague, on the other hand, reached as far as the Barents Sea [8]. The half-life of 129I is very long (15.7 million years), and it is a useful transient tracer in oceanography. Understanding the distribution of 129I in the ocean is important to estimate the impact of anthropogenic radionuclides in natural environments.