[en] At the Belgian Nuclear Research Centre SCK-CEN, activities related to fusion focus on environmental tolerance of opto-electronic components. The objective of this program is to contribute to the knowledge on the behaviour, during and after neutron irradiation, of fusion-reactor materials and components. The main scientific activities for 1997 are summarized

[en] The five papers of this session present the progress and current status of the activities within the Wendelstein 7-x stellarator project investigating the design for its applicability as a thermonuclear reactor. The items of main interest include the modular design of the superconducting magnetic coil system, the blanket, the divertor design concept, and plasma parameters. (DG)

[en] The progress made in fusion research in the past 10 years, or even 20 years, is likely to judged in very different ways by those who are involved in this research and by those who look at it from the outside. From the point of view of the fusion community there is little doubt that great progress has been achieved. Outsiders, on the other hand, tend to judge progress not so much in terms of what has been achieved, but rather in terms of what remains to be done; in this respect, the final goal of obtaining commercial energy from nuclear fusion appears today to be 40 or 50 years away, more distance in the future than it was thought to be 10 or 20 years ago. The present article tries to consider both points of view, and, as far as possible, to reconcile them. The authors concentrate on what we consider key issues, rather than attempting a complete coverage of the subject. Most of the article discuss the magnetic confinement approach to fusion, since this is closer to the direct experience of the authors, and it represents the overwhelming majority of the fusion research effort in Europe. In the United States, expenditures on inertial-confinement fusion research are about as large as those of magnetic confinement, but most of the inertial-confinement work is funded out of the military budget for this relevance to nuclear-weapon physics and, consequently, is not published in the open literature. Only a short mention of the inertial confinement approach is made there; this does not necessarily means that its prospects forth future are considered less interesting than those of the magnetic confinement approach

[en] Research and development work on nuclear fusion is still at a relatively early stage. The physical and technological problems are not yet all solved. Detailed construction plans for a fusion reactor and the hypotheses concerning its radioactive stock and its release are still very make-shift. Working from the knowledge gained so far it is possible to predict how many experimental stages still have to be completed before the first fusion reactor will yield electricity. By taking into account the time required for planning, constructing and operating the subsequent pilot plants one can estimate that nuclear fusion could start to contribute to the energy supply in the middle of the next century at the earliest. Nevertheless, it can already be shown today that fusion reactors have a high inherent safety potential and that their impact on the environment and our climate is very small both during normal operation and in the event of accidents. (orig./DG)

[en] It is shown in this paper that the D-He-3 fusion fuel cycle is not only credible from a physics standpoint, but that its breakeven and ignition characteristics could be developed on roughly the same time schedule as the DT cycle. It was also shown that the extremely low fraction of power in neutrons, the lack of significant radioactivity in the reactants, and the potential for very high conversion efficiencies, can result in definite advantages for the D-He-3 cycle with respect to DT fusion and fission reactors in the twenty-first century. More specifically, the D-He-3 cycle can accomplish the following: (1) eliminate the need for deep geologic waste burial facilities and the wastes can qualify for Class A, near-surface land burial; (2) allow inherently safe reactors to be built that, under the worst conceivable accident, cannot cause a civilian fatality or result in a significant (greater than 100 mrem) exposure to a member of the public; (3) reduce the radiation damage levels to a point where no scheduled replacement of reactor structural components is required, i.e., full reactor lifetimes (approximately 30 FPY) can be credibly claimed; (4) increase the reliability and availability of fusion reactors compared to DT systems because of the greatly reduced radioactivity, the low neutron damage, and the elimination of T breeding; and (5) greatly reduce the capital costs of fusion power plants (compared to DT systems) by as much as 50 percent and present the potential for a significant reduction on the COE. The concepts presented in this paper tie together two of the most ambitious high-technology endeavors of the twentieth century: the development of controlled thermonuclear fusion for civilian power applications and the utilization of outer space for the benefit of mankind on Earth

[en] Funding for fusion energy R ampersand D by the Federal government is an important investment in the development of an attractive and possibly essential new energy source for this country and the world in the middle of the next century and beyond. This funding also sustains an important field of scientific research - plasma science - in which the United States is the world leader and which has generated a panoply of insights and techniques widely applicable in other fields of science and in industry. And U.S. funding has been crucial to a productive, equitable, and durable international collaboration in fusion science and technology that represents the most important instance of international scientific cooperation in history as well as the best hope for timely commercialization of fusion at this time because the development costs are too high and the potential economic returns too distant. But funding fusion is a bargain for society as a whole. However, in light of present congressional funding climates the authors are suggesting a program which falls far short of what US DOE is proposing, but provides monies to keep the program alive, and to retain limited participation in the international program which currently is aimed at the construction of ITER. This limited funding will severly strain the program as it exists domestically at present, will limit industrial participation, will stretch the reasonable date for an operating demonstation fusion reactor, but will maintain the basic stucture of a domestic fusion research program

[en] Ignitor is a proposed high-magnetic field tokamak aimed at studying plasma burning conditions in Deuterium-Tritium plasmas. A preliminary safety analysis has been started to assess the machine safety. Environmental Source Terms (EST), i.e., radioactive and energy inventories have been evaluated. Probabilistic safety assessment, deterministic evaluation of envelope accidental sequences and evaluation of doses to the public have been carried out. The main result is that even the consequences of the worst release scenario are well below the maximum allowable levels. (orig.)

[en] Within the SEAFP and ITER studies dose calculations have been performed for tritium and activation products. Unit release rates as well as preliminary activation product source terms have been investigated. The individual dose values at the fence of the site together with the collective dose to the public have been obtained. Worst case and typical release conditions have been investigated. Additionally, various release durations under accidental conditions, ranging from 1 hour up to 7 days, have been considered. (orig.)

[en] Various tokamak accident scenarios (e.g. rupture of windows or coolant lines) postulate a pressure transient, possibly to levels exceeding ambient pressure within the reactor. This transient can result in transport into the pumping system of the dust previously deposited in the torus and the exhaust ducts. The objective of this experimental work was to investigate quantitatively the behaviour of dust deposited inside the tokamak. The accident conditions are simulated in a model test facility. The similarity criteria are defined for transferring the experimental results from the model to the tokamak. A theoretical model and the experimental results are presented for the transport of solid particles in rarefied gases. (orig.)

[en] The absolute neutron yield of the 14 MeV Frascati neutron generator (FNG) is routinely measured by means of the associated alpha-particle method with a silicon surface barrier detector (SSD). This paper describes the work carried out to characterize the neutron source in terms of absolute intensity and angle-energy distribution of the emitted neutrons. The development of the measuring setup and the assessment of the measurement results are also reported. A complementary calibration procedure for validating the SSD results, based on the use of fission chambers and the activation technique, is also reported. An accurate analysis of the system has been performed via the Monte Carlo neutron and photon MCNP transport code. A detailed model of the neutron source that includes ion slowing down has been inserted into the MCNP code to permit a numerical calibration of the neutron source for comparison with the experimental results. The resulting agreement among the various methods is very good considering the uncertainties, and an accuracy of ±2% is achieved for the measurement of the 14 MeV neutron yield of the FNG. copyright 1996 American Institute of Physics