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Reactor Physics
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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2025 ANS Annual Conference
June 15–18, 2025
Chicago, IL|Chicago Marriott Downtown
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High-temperature plumbing and advanced reactors
The use of nuclear fission power and its role in impacting climate change is hotly debated. Fission advocates argue that short-term solutions would involve the rapid deployment of Gen III+ nuclear reactors, like Vogtle-3 and -4, while long-term climate change impact would rely on the creation and implementation of Gen IV reactors, “inherently safe” reactors that use passive laws of physics and chemistry rather than active controls such as valves and pumps to operate safely. While Gen IV reactors vary in many ways, one thing unites nearly all of them: the use of exotic, high-temperature coolants. These fluids, like molten salts and liquid metals, can enable reactor engineers to design much safer nuclear reactors—ultimately because the boiling point of each fluid is extremely high. Fluids that remain liquid over large temperature ranges can provide good heat transfer through many demanding conditions, all with minimal pressurization. Although the most apparent use for these fluids is advanced fission power, they have the potential to be applied to other power generation sources such as fusion, thermal storage, solar, or high-temperature process heat.1–3
Seyed Ali Hosseini, Alireza Najafi, Amir Saeed Shirani, César Queral, Francesco D’Auria
Nuclear Technology | Volume 211 | Number 3 | March 2025 | Pages 607-623
Note | doi.org/10.1080/00295450.2024.2337313
Articles are hosted by Taylor and Francis Online.
Hydro-accumulators, as a passive part of the emergency core cooling system, have been upgraded in different types of VVER-1000s. The number and performance of these systems are modified in newer types of VVER-1000s to operate at different pressures and flow rates. The VVER-1000/446, as a distinguished design from the old generation (VVER-1000/320), utilizes two stages of hydro-accumulators. The second-stage accumulators (SSAs) are dedicated to improving the performance of the VVER-1000/446 under design extension conditions (DECs) and delaying the onset of core damage. During the upgrading of the VVER-1000/446, some orifices have been embedded as flow restriction components (FRCs) on the injection line of the SSAs to increase the water injection time during DECs.
This paper aims to assess the performance of the SSAs according to their orifice diameter changes during median-break (MB)– and large-break (LB)–loss-of-coolant accidents (LOCAs). Several cases of FRC arrangements were investigated to demonstrate the core damage times during MB-LOCA (200-mm break) and LB-LOCA (400-mm break) scenarios. The results show that although the current size of the installed FRCs on the VVER-1000/446 is quite suitable for the MB-LOCA, it is not a proper choice for the LB-LOCA. Therefore, this demonstrates that the core damage time is highly dependent on the FRC size arrangement.
This paper indicates an arrangement of FRCs that can modify the plant’s response in both MB and LB LOCAs without active injections. Therefore, as an additional finding, the sequential arrangement of FRCs can increase plant resilience against a broad range of LOCAs without operating active emergency cooling systems.
