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The division's objectives are to promote the advancement of knowledge and understanding of the fundamental physical phenomena characterizing nuclear reactors and other nuclear systems. The division encourages research and disseminates information through meetings and publications. Areas of technical interest include nuclear data, particle interactions and transport, reactor and nuclear systems analysis, methods, design, validation and operating experience and standards. The Wigner Award heads the awards program.
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Glass strategy: Hanford’s enhanced waste glass program
The mission of the Department of Energy’s Office of River Protection (ORP) is to complete the safe cleanup of waste resulting from decades of nuclear weapons development. One of the most technologically challenging responsibilities is the safe disposition of approximately 56 million gallons of radioactive waste historically stored in 177 tanks at the Hanford Site in Washington state.
ORP has a clear incentive to reduce the overall mission duration and cost. One pathway is to develop and deploy innovative technical solutions that can advance baseline flow sheets toward higher efficiency operations while reducing identified risks without compromising safety. Vitrification is the baseline process that will convert both high-level and low-level radioactive waste at Hanford into a stable glass waste form for long-term storage and disposal.
Although vitrification is a mature technology, there are key areas where technology can further reduce operational risks, advance baseline processes to maximize waste throughput, and provide the underpinning to enhance operational flexibility; all steps in reducing mission duration and cost.
Sapna Singh, Garima Singal, A. K. Nayak
Nuclear Science and Engineering | Volume 187 | Number 2 | August 2017 | Pages 185-201
Technical Paper | doi.org/10.1080/00295639.2017.1307048
Articles are hosted by Taylor and Francis Online.
Natural Circulation Boiling Water Reactors (BWRs) are susceptible to boiling two-phase flow instabilities under certain conditions, which can lead to flow oscillations in the reactors. These oscillations could be in-phase or out-of-phase in nature depending on the geometry and operating conditions of the system.
This paper reports on a study on the effect of both thermal hydraulics as well as neutron kinetics on the characteristics of boiling two-phase natural circulation flow instabilities in a pressure tube type natural circulation BWR. RELAP5/MOD3.2 code has been used to simulate the natural circulation behavior in multiple channels of the reactor. Before applying the RELAP5 model for simulation of natural circulation in this reactor, the code was benchmarked with the experiment conducted in a multichannel boiling natural circulation loop, having geometry similar to this reactor. The results showed that the RELAP5 model is able to capture the boiling induced-flow instabilities. Then the model was applied to simulate the reactor behavior. The prediction showed that the reactor could experience both Type-I and Type-II density wave oscillations depending on the channel inlet subcooling and channel power. Unlike Type-II instability wherein clear cut outs of phase oscillations among multiple channels were observed, in Type-I instability it was observed that mixed mode oscillations could be present, especially at low subcooling. The phase difference among the channels were found to change with time in Type-I instability. These are completely new findings with regard to characteristics of boiling two-phase natural circulation.
The fuel in this reactor is a combination of (Th-233U)O2 and (Th-Pu)O2, which is different from conventional BWRs. Also, the coolant (light water) is present in different pressure tubes which are physically separated from moderator (heavy water). The effect of neutronic feedback due to this fuel and geometrical configuration on characteristics of Type-I and Type-II instabilities has not been investigated before. In view of this, a systematic investigation was done to study the effect of neutronic feedback on Type-I and Type-II oscillations observed in this reactor. The simulation showed that the threshold power for both Type-I and Type-II instability slightly stabilizes with introduction of neutronic feedback. Since the magnitude of void reactivity feedback is very small in the present fuel composition, the stability boundary was only slightly altered with the introduction of neutronic feedback. Regarding the oscillation characteristics, it was found that change in magnitude of void reactivity has almost no effect on Type-I oscillations whereas the Type-II oscillations get stabilized when void reactivity magnitude was increased. This kind of effect due to void reactivity feedback is in contrast to findings based on conventional BWR and is an important finding of the present study.
