PI: Masahiro Kawaji, City College of New York Proposal Number: CBET-1155673
Project Summary
The proposed U.S.-Japan Seminar on Two-Phase Flow Dynamics will bring together young researchers and well established researchers from the two countries in the area of two-phase flow and heat transfer research. Multiphase flow and associated heat transfer occur in a wide variety of industrial processes and are of critical importance in energy generation and conversion systems, chemical reactors, oil recovery and refining systems, and nuclear reactor systems, among others. They are also important subjects to study in many engineering disciplines such as mechanical, chemical, petroleum, nuclear, aerospace, electrical, and environmental.
Objective: The key objective of the seminars is to provide an opportunity for the participants to carry out in-depth discussions on the state of the art of the field, current challenges, and future directions for research on this important and pervasive phenomenon. The interactions amongst researchers from the two countries will lead to development of co-operative research programs beneficial to the advancement of the field and to pooling of intellectual resources of the two countries in charting the direction of future research. Topics to be considered at the seminars include multi-scale modeling and validation. A thorough discussion of these topics is essential as new tools are developed for simulation of multiphase flows.
Intellectual Merit: The physics of multiphase flows is extremely complex and early investigations lead to formulation of empirical correlations. However, these correlations invariably did not fare well when applied to situations beyond the range of parameters over which the correlations had been developed. Subsequent efforts lead to mechanistic models which also relied on empirical constants to correlate the data. More recently advances have been made to numerically simulate the phenomena while solving conservation equations using appropriate boundary and interfacial conditions. These recent advances have increased confidence in extending the results validated with scaled systems to prototypes. Recent advances have also lead to formulation of models at nano, micro, and macroscale. However, scaling of the phenomena over several length scales is still not a resolved issue.
In energy generation and conversion systems, the reduction of greenhouse gas emission is an urgent goal which can be achieved by developing alternative energy generation strategies that do not depend on fossil fuels. Nuclear energy is one such option and consequently is experiencing a renaissance, however, a recent accident at Fukushima Daiichi Nuclear Generating Station in Japan has highlighted a need to improve our understanding of coolant flow and heat transfer in complex flow channels inside a damaged reactor core and spent fuel bay.
The uniqueness of the seminars is in the in-depth discussions that would take place among all the participants. Unlike other meetings and workshops where diverse topics are discussed, this seminar focuses on specific topics of current and future importance in multitudes of applications. The in-depth discussions amongst researchers of the two countries will lead to collaboration that will have lasting impact in advancing the field of two-phase flow and heat transfer. Junior researchers will be intellectually challenged and stimulated through interactions with nationally/internationally recognized senior and well respected members of the technical community.
This Japan-US Seminar on Two-Phase Flow Dynamics was held in Tokyo on June 7-12, 2012. The main objective of the Seminar was to bring together both well established and young researchers from the two countries in the area of two-phase flow and heat transfer to discuss the state-of-the art and future needs and directions of research in this area. The US participants were as follows. Dr. Karen Vierow (Associate Professor, Texas A&M University) Dr. Xiaodong Sun (Associate Professor, Ohio State University) Dr. Martin Lopez Bertodano (Associate Professor, Purdue University) Dr. Michael Corradini (Distinguished Professor, University of Wisconsin) Dr. Vijay K. Dhir (Distinguished Professor and Dean, UCLA) Dr. Mamoru Ishii (Professor, Purdue University) Dr. Sanjoy Banerjee (Distinguished Professor, City College of New York) Dr. Gretar Triggvason (Professor, University of Notre Dame) Dr. Yassin Hassan (Professor, Texas A&M University) Dr. Masahiro Kawaji (Professor, City College of New York) Twenty two technical papers were presented in six Technical Sessions and included in the Seminar Proceedings. Following the Seminar, all the authors of the technical papers were invited to submit their manuscripts in original or revised form to be published in Nuclear Engineering and Design journal. Manuscripts have been received for peer review and the final versions for publication will be completed by the end of December, 2012. In addition to the six Technical Sessions on the first three days, a "Special Seminar on Two-Phase Flow and Heat Transfer Research – Post Fukushima Accident" was held on the fourth day, June 11, to explore two-phase flow and heat transfer research needs and future directions in view of the accident at Fukushima Daiichi Nuclear Power Plant on March 11, 2011. This Special Seminar attracted an audience of more than 100 attendees and a total of 11 Panel presentations were made by the US and Japanese panelists as listed below. S01 Identification of Future Needs and Directions for Two-Phase Flow Research, M. Kawaji S02 Severe Fukushima Daiichi Accident Study MAAP Analysis and Results, Y. Yamanaka (Tokyo Electric Power Company) S03 Preliminary Analysis of Accident Progression of Fukushima Dai-ichi Unit 1 with SAMPSON Code and Major Uncertainties, M. Naitoh (Institute of Applied Energy) S04 Challenges in Two-phase Flow and Reactor Safety Research after Fukushima Accident, M. Ishii S05 Lessons Learned from Fukushima-Daiichi Severe Accident, K. Okamoto (Tokyo University) S06 Recent Issues in Reactor Thermalhydraulics and Safety, S. Banerjee S07 OECD-NEA Projects on Severe Accident and an Example of Melt Behavior Simulation in JAEA, H. Nakamura (Japan Atomic Energy Agency) S08 Uncertainty of Source Terms Evaluation in Severe Accident and Level 2 PRA, A. Yamaguchi (Osaka University) S09 Phenomena Identification in Severe Accident Sequence and Safety Issues for Severe Accident Management of Light Water Reactors, Y. Abe (University of Tsukuba) S10 Nuclear Systems Multiphase Flow Phenomena: Post-Fukushima, M. Corradini An additional presentation was made by Prof. K. Vierow entitled "The SOARCA Project and Analysis of Heat Transfer/Two-Phase Flow during Postulated Severe Accidents". The panel presentations can be divided into three main groups: (1) descriptions of the Fukushima accident including the detailed chronology of events (S05), accident analyses using severe accident analysis codes such as MAAP (S02) and SAMPSON (S03), and source terms and probabilistic risk analyses (S08); (2) multiphase flow phenomena important in severe accidents (S01, S07, S09 and S10) and challenges in modeling those phenomena (S04); and (3) current issues in reactor thermalhydraulics and safety (S06). After the panel presentations, a general Q&A period followed. The first series of questions focused on whether or not vapor explosions occurred at Fukushima. Several panelists expressed that vapor explosions most likely did not occur due to low melt temperatures. A research need was pointed out regarding further studies of molten fuel-coolant interactions which involve three-phase flows of solid-liquid-vapor and require an advanced diagnostic method to investigate. Additional discussions followed on the future needs for advanced modeling of two-phase flow and heat transfer for reactor thermal hydraulics and safety analyses as summarized below. - A need to focus on mechanistic modeling approaches especially for severe accident analysis - Importance of experiments to validate any advanced two-phase flow models - As the current severe accident researchers are aging, an urgent need exists to bring younger researchers into this research field and revive severe accident research - A need for experienced reactor designers and operators to be involved in severe accident code development due to the complexity of actual plant internals and operating procedures. - To fully learn the lessons from the Fukushima accident, Japanese researchers need to thoroughly investigate the accident - A need to develop better accident management procedures and improve the reactor designs in order to prevent severe accidents in the future
