Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Safety analyses for ADS cores with dedicated fuel and proposals for safety improvements

W. Maschek, A. Rineiskii, K. Morita, G. Mühling, M. Flad, R.J.M. Konings

Abstract

The efficiency of Accelerator Driven Systems (ADSs) for transmutation and incineration of nuclear waste is strongly related to the utilization of so-called dedicated fuels. In the ideal case these fuels should consist of pure TRUs without the classical fertile materials as U238 or Th232 for achieving highest incineration/transmutation rates. Dedicated fuels still have to be developed and programs are under way for their fabrication, irradiation and testing. These fertile-free fuels may suffer from deteriorated thermal-physical properties, as a reduced melting point, reduced thermal conductivity or even thermal instability. Safety analyses show, that the use of dedicated fuels may lead to a strong deterioration of the safety parameters of the reactor core as e.g. the void worth, the Doppler or the kinetics quantities as neutron generation time and ßeff. These quantities are of special importance in the case of severe accidents. In addition, a dedicated core may contain multiple ‘critical’ fuel masses, resulting in a considerable recriticality potential Current knowledge on these dedicated fuels suggests that ‘critical’ reactors may not be feasible, because of safety reasons. However, for ADSs, the subcriticality of the system should cope with these deteriorated safety parameters. First analyses are presented, which show potential safety problems for ADSs with such dedicated cores in the severe accident range. Inherent safety measures are proposed to obtain a balanced safety approach with special emphasis on severe accidents.

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key words: Fast Neutron Spectrum Systems, Nuclear Technology
Reference:
Proceedings of a Committee Meeting (TCM) on “Core Physics and Engineering Aspects of Emerging Nuclear Energy Systems for Energy Generation and Transmutation” held in Argonne, Illinois, U.S.A., 28 November - 1 December 2000
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--1356, pp:265-276