TRIP REPORT

US-JAPAN WORKSHOP ON FUSION POWER REACTOR DESIGN (P246) UNIVERSITY OF KYOTO, KYOTO, JAPAN

MARCH 13-16, 1995
by
C.P.C. Wong

Prepared under:
Contract No. DE-AC03-89ER52153
for the U.S. Department of Energy

March 1995

1. PURPOSE OF TRIP

This trip report covers the attendance of Dr. Clement Wong of General Atomics at the US-Japan workshop on Fusion Power Reactor Design (P246), University of Kyoto, Kyoto, Japan (March 13-16, 1995), with People's Republic of China (PRC) and European Community (EC) participation.

2. Workshop

The workshop agenda is attached as appendix A.

Presentations made

I made two presentations for the Starlite-Demo project. The first topic was on " Safety and Licensing of Fusion Power Plants". I presented our Demo safety team activities, summarizing topics of NRC jurisdiction on fusion, fusion safety standard, our road map to develop fusion licensing Code of Federal Regulations (CFRs), Demo safety top level design requirements, and our present activity on hazard assessment of our ARIES-II and IV designs. Dr. E. Salpietro of EC commented that it is unnecessary to invent new regulatory design requirements for fusion. We should only need to show that fusion can easily meet all the present fission industry safety regulations. I believe that he made a good point, we have to indicate clearly that our more stringent Demo design requirements are only used for design guidance and not for the replacement of existing US NRC regulations. However, in the area of licensing, we will help to simplify the process as much as possible. The second topic, I presented, was on " The status of US SiC/SiC-composite development in 1995". I presented the DOE SiC/SiC composite development guideline and summarized the results of the presentations of the US SiC/SiC-composite workshop at RPI last year (1994). I also pointed out the potential fundamental limitation of low thermal conductivity of present SiC/SiC-composite material, which would limit its utility for high heat flux components application. Improvements over present material properties will be necessary.

The Japan, JAERI team showed the DREAM-II design, an extension of the DREAM design presented in the last workshop which had a maintenance hall included within the TF coils. Therefore the machines is necessarily large in size (R=15 m, a=2.15 m, and k95=1.54) and power output, ~3GWe. The large size of the DREAM-II machine is also caused by the excessive total inboard blanket/shield thickness of 3 m, and the design approach of having helium-coolant pipes penetrating the inboard TF coils. The latter is to allow the heat exchanger to be located within the central opening of the tokamak. Many design changes and improvements will be needed to make it to become an attractive machine. For structural materials, they are considering the use of TiAl-alloy and SiC/SiC-composite. TiAl metal matrix is also their material of interest.

The Japan, U of Tokyo team showed their stainless steel pulse power plant design, which is big (R=10m, a=2.9m, k=1.5) and expensive (a 241MWnet device with a thermal efficiency of 24%). It is a day long pulse device. They proposed to use the existing pumping-up hydroelectric power plant as the thermal storage scheme. At a neutron wall loading of 0.5 MW/m2, the first wall will be replaced every 2-5 years. This is a useful piece of work to show how not to design a fusion power plant. This also shows the negative design impacts when SS is used as the structural material for fusion power plant. They did say that the use of both advanced physics and material will lead to a smaller device.

The EC team showed a lot of details, both on design and safety analysis, on their SEAFP program. They started with requirements on safety and developed the model-I design which uses V-alloy, helium-coolant, and Li2O solid breeder, and the model-II design which uses ferritic steel, water-coolant, and 17Li83Pb breeder. Assuming 3 physical barriers and the release fraction of 1% from each barrier, they were able to achieve their goal of not requiring an evacuation plan. Model-I design has much better safety characteristics than the model-II design. The key critical issue for the model-I design is the required control of potential interaction between helium impurities and V-alloy, to prevent the formation of lithium oxides. This could be achieved by suitable interface coating (Al2O3 was proposed) and/or control of helium impurity content to level less than 1 ppm. Concept wise, the model-I helium-cooled, V-alloy design is similar to the option being studied by GA for the Demo-I design.

The Chinese (PRC) team showed again their logic for developing hybrid reactors in order to satisfy the potential fissial fuel need of their fission reactors in the year 2050. They are working on a helium-cooled, nested shell configuration, liquid breeder design called the Fusion Engineering Breeder (FEB). They have also developed more design details, including some work on probabilistic risk assessment (PRA). They are also looking into a volumetric neutron source (VNS) device.

Our US team presented the results of our PULSAR design and the status of our Starlite-Demo physics and engineering activities.

The US also presented our Stellerator design which show details of the coil set, but showed no details of the blanket/divertor design.

The Japanese NIFS team showed the status of the impressive Large Helical Device (LHD) under construction. They also showed their unreasonable goal of a 45 dpa life-time ferritic steel for their extrapolated DEMO design. It is designed to a neutron wall loading of 1.5 MW/m2, and therefore necessarily becomes a big machine when the total power output is 1000 MWe. They also indicated the impossible maintenance scenario of using a 1 m wide slot between the continuously winded helical coils. This approach will lead to excessively long maintenance time even if it is proven to be feasible, which is quite unlikely.

3. APPENDIX A

Agenda of the Japan-US Workshop on Fusion Power Reactors with Participation of China and EU
(March 13 - 16, 1995 at Kyoto University, Kyoto)

March 13 (Mon) AM: Overview (9:00-12:30)

Welcome Address K. Takahashi
Status of US Power Plant Studies Program F. Najmabadi
Fusion Reactor Studies in China X. Deng
The European SEAFP Project: Overview E. Salpietro
Fusion Reactor Studies in JAERI Y. Seki

March 13 (Mon) PM: Reactor Designs (13:30-17:30)

SEAFP: The Fusion Power Station Models I. Cook
Pulsar System Studies R. Miller
Physics of PULSER and advanced Tokamak regimes D. Ehst
DEMO Reactor based on Presently-established Scientific Knowledge N. Inoue
Physics Design of Inductively-operated Tokamak Fusion Reactor Y. Ogawa
Bootstrap Current Profile Control based on the Density Profile Control by the Pellet Injection J. Wong
Drastically Easy Maintenance Reactor: DREAM-2 S. Nishio
Divertor Design of DREAM-2 I. Senda

Reception Party (18:00-21:00) at Kyodai Kaikan

March 14 (Tues) AM: Reactor Designs (9:00-12:30)

Tight Aspect Ratio Tokamak Reactor Studies P. J. Knight
The Effect of the H-mode Power Threshold on POPCON in a Tokamak Reactor O. Mitarai
A Compact Tokamak Reactor Design for VNS's Application L. J. Qiu
Blanket Design (SWIP Version) of a Fusion Engineering Breeder, FEB J. Huang
Engineering Aspects of DREAM-2 T. Kuroda
Pulsar Engineering L. Waganer

March 14 (Tues) PM: Stellarators (13:30-18:00)

Stellarator Power Plant Physics J. Lyon
Stellarator Power Plant Engineering Dai-Kai Sze
Stellarator Power Plants System Studies R. Miller
Design Status of Force-free Helical Reactor (FFHR) O. Motojima
Design Study on Blanket and Coolant in FFHR A. Sagara
Conceptual Design for Divertor of FFHR S. Ohyabu
Structural Design for FFHR S. Imagawa

March 15 (Wed) AM: Environment & Safety (9:00-12:30)

SEAFP: The Safety and Environmental Assessment N. P. Taylor
Safety And Licensing Of Fusion Power Plants C. Wong
Improvement of Tritium Burn-up Rate A. Fukuyama
Fusion Safety Data Base I. Aoki
Fusion Safety Experiments in JAERI T. Kunugi
R&D on Advanced Structural Materials A. Kohyama

March 15 (Wed) PM: Tour of Fusion Facilities/Cultural Sites (13:30-18:00)

Sukiyaki Party (18:30-21:00)

March 16 (Thurs) AM: Materials, Strategy and Future Collaborations (9:00-12:30)

SiC/SiC Material Review S. Ueda
V-alloy Structural Material Dai-Kai Sze
SiC-Composite Development in the US-1995 C. Wong
Comments on Methodology of Comparison between Various Types of Fusion Power Reactors K. Okano
Improvements for DT Tokamak Power Reactor Concept K. Yoshikawa
The Potential of Isotopic Tailoring for Minimizing
Radioactivity of Fusion Structural Materials T. Muroga

5. APPENDIX C

WORKSHOP MEETING:

Key persons:

Host, Dr. Y. Seki
Local host, Prof. K. Yoshikawa
EC leader, I. Cook
PRC leader, L. J. Qiu