Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Nuclear waste incineration - The case for ADS

J. Magill, P. Peerani, and J. van Geel European Commission, Joint Research Centre Institute for Transuranium Elements, Karlsruhe, Germany
H. Rief, H. Wider European Commission, Joint Research Centre, Institute for Systems, Informatics, and Safety (ISIS), Ispra, Italy

Abstract

In this paper we consider some key issues associated with nuclear waste incineration and how these issues can be addressed with the use of accelerator driven systems (ADS). The first issue is related to the safety and control of reactor systems. The control of critical reactor systems is determined mainly by delved neutrons (which do not appear immediately in the fission process) and their associated reactivity. When critical reactor systems are used to burn nuclear waste, this delayed neutron fraction decreases making the control of the system significantly more difficult. For sub-critical accelerator driven systems, it is shown that the spallation neutrons (which are independent of the sub-critical assembly), can be considered as a very much enhanced delayed neutron fraction. As a result, accelerator driven sub-critical systems will react more benignly and can cope with greater reactivity excursions than critical reactor systems. This is especially true for fast neutron systems. The second issue we address is how much waste we may have to deal with and whether ADSs can cope. At the present level of global nuclear power production, about lo4 tons of spent fuel are being produced each year containing approximately 90 tons Pu, 6 tons Np, 2 tons Am, and 0.5 tons Cm. Since fissioning 1 ton Pu will result in an energy release of approximately 1 GW,y (i.e. the energy produced by one large reactor in one year), a large number of ADSs will be required to burn all the plutonium and minor actinides! The scale of this problem can be significantly reduced by recycling the Pu back into MOX or TMOX fueled PWRs. A detailed analysis of this problem is presented. Finally, we consider some conceptual designs for an accelerator driven waste incinerator with a view to starting relatively small scale experiments. In principle, one should be able to design a system in which at any time less than one critical mass (e.g. of Pu) is present thereby avoiding the possibility of criticality accident. The effective neutron multiplication factor should, however, be as close to 1 as possible to give as high a multiplication factor of the spallation neutrons as possible. We consider the neutronics of some simple geometrical core arrangements.

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key words: Fast Neutron Spectrum Systems, Nuclear Technology
Reference:
Technical Committee Meeting, Madrid, Spain 17-19 September 1997
International Atomic Energy Agency, Vienna (Austria)
IAEA-TC--903.3, pp:295-304