Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Selected propertees of accelerator-driven subcritical systems for transmutations

Abstract

In the transmutation systems any reduction in the needed accelerator current. as well as low values of Keff for safety reasons. are most desired. Thus, the maximization of system energy gain without heightening the Keff is the objective of research. This effect can be attained when maximizing the number of tissions induced by primarv (e.g. beam produced) neutrons and in the first generations of the chain reaction due to: a harder spectrum of source than fission neutrons and a privileged position of the first several generations. provided the fissioning in there is highly probable. This is valid for unidirectional coupling of a smaller subcritical device (driver) to a larger one for control. ‘This way. a higher safety can be assured, since the Keff of the system as a whole remains much lower than that derived from its power. provided the control unit little contribute to the overall criticality. For this purpose, a replacement of the (proposed hitherto) absorbing separator by a non-absorbing one and a spatial distancing is suggested. The asymmetry of systems coupling is based upon the size disproportion - the minute driver is contained within the larger driven assembly. Since geometrical effects are independent of the neutron energy, a hard spectrum can be maintained, as there is no neutron excess in thermal systems in contrast to fast ones. The prospects and advantages of the present concept have been confirmed in the performed calculations.

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Reference:

Technical Committee Meeting, Madrid, Spain 17-19 September 1997

International Atomic Energy Agency, Vienna (Austria)

IAEA-TC--903.3, pp:409-424