I have made contributions in diverse areas including neutronics, thermal-hydraulics, nuclear fuel, public communication, irradiation and renewable energy. These studies either propose novel solution or reveal insights into the mechanisms.

The adventure started at University of Illinois at Urbana-Champaign, where I was allowed to decide the subject of my Ph.D. study. I decided to test a new idea of coupling neutronics and thermal-hydraulics after taking courses in neutronics, thermal-hydraulics, and programming. I named the new idea Integrated Tight Coupling, or ITC, which modified the equations, instead of solving the same set of equations with different approaches as the traditional loose coupling and tight coupling do. The implementation of ITC is similar to that of loose coupling, but primary results suggest that ITC allows a coarser mesh and fewer iterations [1]. During my Ph.D. period, I completed an internship at Idaho National Laboratory. I added and validated new features and models to a code that predicts hydrogen distribution inside a containment. Results of the 12-week work is published in [2].

After my graduation, I wanted to learn more about the Fukushima accident and do something for it, so I joined Japan Atomic Energy Agency (JAEA) as a postdoctoral scholar. I collaborated with the researchers to gain insights into fuel behavior during LOCA experimentally and computationally. I scrutinized experimental data and found that the mechanical behavior of cladding was affected by its thermal diffusivity, thermal expansion and oxygen dissolved in the metallic layer, which had not been considered in the analysis. Therefore, I derived equations using published data, and the updated code gave better predictions [3]. In addition, I designed experiments to reveal the order of cracks formed in cladding during LOCA quench conditions using different thermal stresses, which was achieved economically by different thermal capacities inside the cladding. High thermal stress resulted in cracks in the oxide while low thermal stress did not. It suggests that the cracks form in the αZr(O) layer first, and then in the oxide, finally in the prior-β layer when the fracture of cladding occurs [4]. I visited Helmholtz-Zentrum Dresden-Rossendorf (HZDR) after the end of the work contract in Japan. I successfully developed an interface to couple DYN3D (the in-house neutronic code of HZDR) and OpenFOAM, and verified it with a 3-D reactor model with help of my supervisors in three months [5].

Then I was attracted by the aggressive nuclear power program in China.  I have been conducting independent research and supervising a group of students at Huazhong University of Science and Technology since 2018. The research was guided by the idea that the development of nuclear power would be mainly affected by two factors. One is the price of nuclear power, and the other is the public perception of nuclear safety. As nuclear safety has gained attention after the Fukushima accident, the related cost increases. Therefore, we explored three economical ways to enhance nuclear safety. 

First, I studied the concept of a passive residual heat removal heat exchanger (HX) and came up with an idea of changing the configuration of C-shaped HX tubes to spiral-shaped ones. The CFD computation suggests that the new design enhances heat transfer and increases cooling capacity [6]. In addition, I noticed that none had examined the effect of tube defect on the performance of the HX, so we did it. The computational results suggest that it is correlated with the size of the surface area of the deficient tubes instead of their locations [7]. Second, I was inspired by moisture spikes on the lid of a Staub cookware that were designed to create a rainforest effect and return juices evenly to the food. I proposed placing moisture spikes on the dome of the containment to enhance water circulation during an emergency. We tested two designs—spherical and conical spikes—and the computational results suggest that the former has a better heat transfer performance [8]. A spherical spike improves the heat transfer rate by 11.7%. The spiral-shaped heat exchanger tubes and moisture spikes have the potential to be implemented in any nuclear power plant without much cost.

Third, nuclear industry has spent lots of efforts on enhancing nuclear safety, but many people still claim that nuclear is dangerous. Therefore, it could be efficient to gain support with a better understanding of people’s perceptions. We conducted surveys to gain insights into young Chinese people’s opinions on nuclear power using concepts of behavioral economics. The analyses suggest that young Chinese people’s perceptions of radiation significantly impacted their opinions on nuclear power. In addition, perceptions of nuclear reactor technology seemed independent of their perceptions of nuclear power, which were not the main factor influencing the respondents’ support for nuclear power [9-10]. In other words, either boasting the advanced reactor technology or working on people’s perception of nuclear power would not gain support for nuclear power efficiently. The key is how people think about radiation.  

In addition to nuclear power, I proposed new ideas in areas including irradiation and renewable energy. I got a chance to visit a gamma irradiator, and then I came up with a new configuration of a shuffle-dwell gamma irradiator based on the fact that radiation emits in an isotropic fashion. It has potential for increasing energy utilization and throughput, which leads to higher profitability [11]. I attended a seminar and learned that forecasting models of renewable energy were evaluated statistically. I proposed evaluating these models from the perspectives of stability of the power grid and the availability of usable energy [12].

Currently I continue the research on passive safety systems, such as a natural circulation loop. I like to think about new ideas to improve the performance of current systems and treat problems holistically. These years of research experience suggest that I think differently from most people. Therefore, I usually skip literature review and go ahead with my ideas. I would check what other researchers have done in this field when I need materials for the Introduction section of a manuscript.

References

[1] Hsingtzu Wu, Rizwan-uddin, “A Tightly Coupled Scheme for Neutronics and Thermal-hydraulics using Open-source Software,” Annals of Nuclear Energy. Vol. 87, January 2016, pages 16-22.

[2] Hsingtzu Wu, Haihua Zhao, “Validation of hydrogen gas stratification and mixing models,” Annals of Nuclear Energy. Vol. 85, November 2015, pages 137-144.

[3] Hsingtzu Wu, Yutaka Udagawa, Takafumi Narukawa, and Masaki Amaya, “Validation of updated RANNS with effect of oxygen-dissolved metallic Zircaloy-4 under LOCA quench condition,” Nuclear Engineering and Design, Vol. 300, 15 April 2016, Pages 249-255.

[4] Hsingtzu Wu, Yutaka Udagawa, Takafumi Narukawa, and Masaki Amaya, “Crack formation in cladding under LOCA quench conditions,” Nuclear Engineering and Design, Vol. 303, July 2016, Pages 25-30.

[5] Hsingtzu Wu, Alexander Grahn and Soeren Kliem, “Verification of a coupling interface for DYN3D and OpenFOAM with a three-dimensional mini-core,” Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020, a virtual meeting, May 18-22, 2020.

[6] Hsingtzu Wu, Linfeng Yan, Lanshan Yuan, “Pilot numerical study of new design of passive residual heat removal heat exchanger tubes,” Progress in Nuclear Energy, Volume 146, 2022, 104150.

[7] Linfeng Yan, Dawei Wang, Hsingtzu Wu, “Analysis of Influence of Tube Failure on Performance of Passive Residual Heat Removal Heat Exchanger,” Nuclear Technology, Volume 208, Issue 12, 2022, 1822-1831.

[8] Li Zhou, Hsingtzu Wu, “A pilot study on modification of containment dome surface to enhance condensation,” Progress in Nuclear Energy, Volume 156, 2023, 104557.

[9] Hsingtzu Wu, Leyao Huang, “Young Chinese people's radiological beliefs significantly associated with their opinions on nuclear power,” Progress in Nuclear Energy, 138, 2021, 103797.

[10] Hsingtzu Wu, Leyao Huang, Lanshan Yuan, Da-Wei Wang, Shaoxuan Wang, “Young Chinese people's perceptions of nuclear power: Connection with enthusiasm for information, perceptions of nuclear reactor technology and NIMBY,” Progress in Nuclear Energy, Volume 141, 2021, 103964.

[11] Hsingtzu Wu, “A proposed new configuration of a shuffle-dwell gamma irradiator,” Nuclear Engineering and Technology, Volume 54, Issue 8, 2022, Pages 3176-3180.

[12] Hsingtzu Wu, Da-Wei Wang, “A New Method to Compare Performance of Forecasting Models,” proceedings of 2021 IEEE 5th Conference on Energy Internet and Energy System Integration (EI2), 2021, pp. 1320-1325, doi: 10.1109/EI252483.2021.9713024.