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A day in the life of the nuclear community
The November issue of Nuclear News is focused on the individuals who make up our nuclear community.
We invited a small group of those individuals to tell us about their day-to-day work in some of the many occupations and applications of nuclear science and technology, and they responded generously. They were ready to tell us about the part they play, together with colleagues and team members, in supplying clean energy, advancing technology, protecting safety and health, and exploring fundamental science.
In these pages, we see a community that can celebrate both those workdays that record progress moving at a steady pace and the exceptional days when a goal is reached, a briefing is delivered, a contract goes through, a discovery is made, or an unforeseen challenge is overcome.
The Nuclear News staff hopes that you enjoy meeting these members of our community—or maybe get reacquainted with friends—through their words and photos.
Seung Min Woo, Heukjin Boo, Sunil S. Chirayath, Keunhong Jeong
Nuclear Technology | Volume 205 | Number 3 | March 2019 | Pages 464-473
Technical Paper | dx.doi.org/10.1080/00295450.2018.1500074
Articles are hosted by Taylor and Francis Online.
Under normal operating conditions, a pyroprocessing facility removes highly radioactive and nonradioactive fission product waste from used nuclear reactor fuel to recycle the remaining uranium (U), plutonium (Pu), and other actinides contained in it. The products from this facility are separate ingots of U and mixed transuranic elements (TRUs)–uranium (TRU-U). Uranium in both ingots will be depleted U with 235U enrichment less than 1%. The TRU-U ingot will contain neptunium, Pu, americium (Am), and curium (Cm) mixed with U with an approximate TRU:U ratio of 1:1. Four scenarios of nuclear material diversion by potential misuse of the pyroprocessing facility operations are analyzed and compared with the scenario of normal operating condition when the electrowinning process or the TRU-U ingot manufacturing process is misused. These diversion scenario analyses are carried out to understand the proliferation potential and to recommend safeguards measures. The four scenarios of nuclear material diversion analyzed are (1) 50 g Pu, (2) 100 g Pu, (3) 200 g Pu, and (4) all Pu, i.e., 452 g in the 1-kg TRU-U ingot. Plutonium cannot be diverted by itself because other TRUs (Am and Cm) will be simultaneously extracted with Pu. This is because the reduction potentials of those actinides are not distinguishably different from that of Pu on a liquid cadmium cathode of the electrowinning step of the pyroprocess. Hence, in addition to Pu, simultaneous diversion of respective amounts of Am and Cm for the four diversion scenarios are considered. The diversion scenario analysis also considered the concealment of Pu and Cm removal from the TRU-U ingot by adding an equivalent amount of 252Cf to replenish the neutron source emissions. These five scenarios (four nuclear material diversion scenarios and one normal operation scenario) are modeled and simulated using the Monte Carlo N-Particle (MCNP6) radiation transport computer code by incorporating the model of a NaI gamma radiation detection system. The results show that the presence and absence of Pu in the TRU-U ingot can be confirmed by the NaI gamma radiation detection system. However, identifying the presence of U in the TRU-U ingot is difficult using the NaI gamma radiation detection system due to interference from TRU gamma radiation. To identify the U presence in the TRU-U ingot, an application of nuclear magnetic resonance (NMR) is studied. The NMR technology employs a numerical calculation approach based on density functional theory (DFT) simulation. The DFT calculation results show that the detection of U in a pyroprocess is feasible by NMR technology. In addition, these four nuclear material diversion scenarios are analyzed through MCNP6 simulations by incorporating the model of a coincidence neutron detection system. To conceal the nuclear material diversion, the simulations are performed by replacing the diverted Pu and Cm by an appropriate mass of 252Cf neutron source that is equivalent to the neutron source strengths of the diverted mass. Simulation results show that this concealment (misuse) results in a deceived Pu mass estimate in the TRU-U ingot if the Pu-to-244Cm–ratio method (proposed method in the literature) is used.