Estimation of acceptable beam-trip frequencies of accelerators for accelerator-driven systems and comparison with existing performance data

Frequent beam trips as experienced in the existing high-power proton accelerators may cause thermal fatigue in accelerator-driven system (ADS) components, which may lead to degradation of their structural integrity and reduction of their lifetime. In this study, acceptable beam-trip frequencies of the ADS accelerator were evaluated and compared with the performance of the ADS accelerator, which was estimated based on the operational data on existing accelerators. Thermal transient analyses were performed to investigate the effects of beam trips on the reactor components, with the objective of determining the feasibility of engineering the ADS and the reliability of the accelerator. These analyses were based on the thermal responses of the following reactor components: the beam window, the fuel cladding, the inner barrel and the reactor vessel. Assuming that the annual plant availability was 70%, our results indicated three acceptable beam-trip frequencies, depending on the beam-trip duration, tau(b): 2 x 10(4) times per year for 0 <= tau(b) <= 10 s; 2 x 10(3) times per year for 10 s < tau(b) <= 5 min; and 42 times per year for tau(b) > 5 min. In order to consider methods to reduce beam-trip frequency, we compared the acceptable beam-trip frequency with the performance of the ADS accelerator, which was estimated based on the operational data on existing accelerators. The comparison showed that for beam trips with a duration of 10 s or less, the beam-trip frequency was acceptable. On the other hand, for beam trips with durations of 10 s < tau(b) <= 5 min and tau(b) > 5 min, it was necessary to reduce the beam-trip frequencies to about 1/6 and 1/35, respectively.