1. TECHNOLOGY CHALLENGES ON THE ROAD TO THE FUSION REACTOR
Roberto Andreani
EFDA Associate Leader for Technology
SOFT Venezia September 2004

2. Content Present situation of the fusion programme
Which are our (my) ideas about a DEMO (PROTO) reactor
How does it compare with ITER and what we wish to change/improve
What then needs to be done
Are we too, or too little optimistic?
SOFT Venezia September 2004

3. Present situation of the fusion programme (1)
A positive decision on ITER construction has been taken, since a long time, by the European council. The site decision is unfortunately still on hold.
The physics basis of ITER, established first in 1992 and then confirmed in 1998, when proposing the reduced version of the machine, has been very satisfactorily confirmed by the experiments.
In particular JET and JT-60 have contributed but, like in a large painting, a lot of details have been added on the basis of the results obtained on many other experiments run worldwide.
SOFT Venezia September 2004

4. Present situation of the fusion programme (2)
The potential operating domain of ITER has been very appropriately chosen to allow extrapolating the physics of ITER to a reactor in case of successful performance of the experiment.
The basic engineering design of ITER is complete. A number of design details and some technological choices are still missing and will be decided during the initial phases of construction as it always occur with large projects. The new Director and the new International Team will have to take responsibility.
The materials and the technologies needed to build ITER with reasonable confidence have been developed during the more than 10 years of R&D conducted by the ITER parties in view of the construction.
SOFT Venezia September 2004

5. Present situation of the fusion programme (3)
In Europe, in the framework of the EFDA technology programme, a number of strategic objectives have been pursued:
- Review critically the new design of ITER in support to the International Team
- Prepare technological and manufacturing solutions safely applicable to the critical areas of the project, even independently from the final configuration which might be adopted.
Typical examples the radiation enduring magnet insulation, the high heat flux resistant plasma facing components, the divertor, the vacuum vessel, providing reliable recipes for the construction of components of the machine.
- Build and test prototypes of crucial systems like the fuel cycle, the divertor remote maintenance system, the cryogenic pumping system, in view of assuring their reliability.
SOFT Venezia September 2004

6. Present situation of the fusion programme (4)
- Conduct a comprehensive set of design and R&D activities, both in physics and engineering, on the ITER day one Heating and Current Drive systems. In ICRH integrate the JET experience of manufacturing and testing an ITER relevant antenna.
- Prepare a set of essential facilities needed to test mock-ups and prototypes and to allow quality control during series manufacturing.
- Assist the French Association in preparing the site to host ITER as a true European site.
- All of these activities have been conducted putting great attention to the need to train European industry in view of the manufacturing phase.
SOFT Venezia September 2004

7. Present situation of the fusion programme (5)
All together, during the last three years of the technology programme, about 160 M€ have been spent by European Associations and Industry, under coordination by EFDA, in preparation of ITER.
SOFT Venezia September 2004

8. Present situation of the fusion programme (6)
In addition to the ITER activities, exploratory activities are conducted in view of the design and construction of a DEMO, especially, but not only, in those domains, like the materials, where we already know that, beyond ITER, we will need new better suited solutions.
A debate has been taking place, since somewhat more than a year, about the possibility of adopting and following a “fast track” in our quest for fusion power. This requires an agreement amongst a number of international partners to properly share the different elements of a broader approach to fusion. We hope that this agreement materialises soon.
SOFT Venezia September 2004

9. Which are our (my) ideas about a DEMO (PROTO) reactor (1)
A DEMO should likely demonstrate that a fusion reactor can indeed produce a significant amount of energy, delivered to the electrical grid. No guarantee could be provided before hand on the availability of the machine but it is expected that the quality of operation and the load factor would be acceptable and improving with time.
An electric power of the order of 1000 MW seems appropriate considering that the size of the machine would have to be large enough to allow reaching a value of the gain Q (= P fusion/ P heat&CD) of the order of 30. By simple considerations, one recognises that the size of ITER is of the same order of the size needed for a reactor.
SOFT Venezia September 2004

10. Which are our (my) ideas about a DEMO (PROTO) reactor (2)
Considering the most advanced concept of reactor studied in the Power Plant Conceptual Study, the size of a 1500 MWe reactor approximately coincides with the size of ITER. This implies extremely high operating temperatures (> C) and efficiency, and then advanced materials still in the early stage of development. But also considering a water cooled 1000 MWe reactor and modest extrapolations in physics and technology, the linear size would be only % larger than ITER.
SOFT Venezia September 2004

11. How does DEMO compare with ITER and what would we wish to change or improve (1)
There are a number of critical areas in which we do not have yet a consolidated design choice : the coolant, the main structural material, the first wall, the blanket and the divertor, the remote handling system.
Additional problems, like the choice of the superconductor for the magnets (which might have a strong impact on the cost) or the decision on the type of additional heating and current drive systems are not so crucial for the success of DEMO.
The coolant. A preference for helium has been already expressed in the European programme when helium cooling was chosen for the two European blanket concepts to be tested in ITER. Helium presents advantages in operating temperature (thermodynamic efficiency of the reactor) and safety (due to the absence of chemical reactivity with the materials present in DEMO).
SOFT Venezia September 2004

12. How does DEMO compare with ITER and what would we wish to change or improve (2)
Structural material. The austenitic steel used for ITER would undergo an excessive swelling when subject to the fluences foreseen in DEMO (an equivalent damage of dpa compared with 3 dpa in ITER) and would present the problem of high activation, high nuclear heating and long decay time. Europe is developing EUROFER, a 9 Cr ferritic martensitic steel which looks rather promising. This type of steels has already performed well in fast breeder reactors at that level of fission neutrons fluence. It is in the same category of steel to which the Japanese F82H belongs.The operating temperature of EUROFER ( C) sets the limit to the thermodynamic efficiency of the reactor. A problem to be properly accounted for is that martensitic steels are ferro-magnetic.
The fusion variety has to account for the high neutron energy and the need to reduce the level of activation and minimize the radioactivity decay time of the irradiated material. The first irradiation results with fission neutrons, although up to a limited number of dpa, are promising. The validation of these results using the right breed of neutrons is however a must before adopting EUROFER for DEMO. This implies to start as soon as possible, in parallel with ITER construction, with the construction of IFMIF.
SOFT Venezia September 2004

13. How does DEMO compare with ITER and what would we wish to change or improve (3)
First wall. DEMO first wall could not provide an acceptable lifetime using graphite or beryllium as in ITER and in the present machines. A metallic first wall would be desirable, tungsten or, even better, steel to reduce activation. Experimentation on the existing machines needs to be pursued in order to establish the compatibility of the plasma regimes with these types of solutions.
Blanket. Experimentation with ITER is essential in order to test blanket solutions. Two concepts, both helium cooled, one with a pebble bed of lithium ceramic as a solid breeder and beryllium multiplier, the second with a liquid lithium lead eutectic, are being developed in Europe. A helium cooled, lithium lead blanket avoids the presence of beryllium. Hopefully the engineering and technological problems related with both solutions will be solved in the framework of the ITER test programme.
SOFT Venezia September 2004

14. How does DEMO compare with ITER and what would we wish to change or improve (4)
Divertor. A helium cooled divertor would be highly desirable. The relevant R&D programme is already under way inside EFDA and appears well oriented although there is a long way to go.
Superconducting materials. The success of ITER operation would provide an assurance for the use of Nb3-Sn as the superconducting material. In the mean time the fusion programme is going to carefully monitor the industrial developments in the field of high temperature superconductors applications and an exploratory R&D will be conducted also by EFDA in view of their application to fusion specific needs.
Heating & CD systems. The choice of the best solutions in this respect will be likely dictated by the results obtained in ITER.
SOFT Venezia September 2004

15. What then needs to be done (1)
We are moving towards a transition from a strongly physics oriented programme to a physics based, large, industrial type programme to build the reactor.
The European fusion programme is still predominantly physics oriented. There are in the programme about 2000 professionals, out of them, one third between technologists and engineers. The financial resources spent on technology during the VIth Framework Programme are about 1/7th of the financial resources assigned by the Commission to the entire fusion programme.
In the mean time there is also a diffused scarcity of experienced personnel. No machine has been built in Europe and in the world during the last 15 years.
SOFT Venezia September 2004

16. What then needs to be done (2)
All this translates in the fact that more or less all the European Associations, involved in technology activities, are working at present at the limit of their capabilities.
Definitely, in my opinion, to move on a fast track towards the reactor, we need a strong enhancement in the human and financial resources devoted to fusion technology and engineering in the European programme.
The broadening of the human basis of the programme in the Associations is also absolutely necessary to prepare new generations of fusion scientists and engineers.
In the mean time ITER will require a very strong involvement of the most qualified European industry.
SOFT Venezia September 2004

17. Are we too or too little optimistic? (1)
Success of the programme (of DEMO) will depend on a number of factors:
A steady state operation of ITER according to the expectations.
An in-depth understanding of the physics regimes of ITER, obtained through the experimentation, allowing to produce a reliable model of the plasma of DEMO, which should not be an experiment in this respect.
A successful operation of the remote handling systems in ITER, to guarantee the needed availability of this machine for experimentation and to design a DEMO with confidence.
A strong investment in qualified human resources in the Associations.
A solid industrial involvement throughout the construction and operation of ITER to prepare a well qualified European “fusion” industry to play a crucial role in DEMO.
SOFT Venezia September 2004

18. Are we too or too little optimistic? (2)
In conclusion:
I personally feel that we have prepared a good basis from which to proceed.
Of course we cannot be sure of the success,
but
The game and the potential results are worth playing.
SOFT Venezia September 2004