SAFETY ASPECTS OF TARGETS FOR ADTT: Activity, volatile products, residual heat release

Safety aspects of heavy metal liquid targets for the accelerator driven systems connected with the activity accumulation and residual energy release due to the irradiation with high energy proton beam are discussed. The results obtained for the lead-bismuth target that are under construction in IPPE now in the frame of ISTC Project No. 559 are briefly presented. The calculations and the analysis of the accumulation of the spallation reaction products, activity and energy release at various moments after the accelerator shutdown are presented. The concentrations of the reaction products, the total and partial activities, the activities of volatile products are determined. The contributions of the short-lived nuclides important for the prediction of the facility behaviour in regimes with the accelerator beam trips. The calculations and analysis of the residual energy release due to different decay type have been performed. 1. Analysis of the total activity. The calculations of the total activity of the lead-bismuth target having cylinder form, 20 cm diameter and 60 cm length have been performed. Atomic mass is 208.3, the total mass is 197.35 kg. The target is irradiated with 800 MeV, 1.25 mA proton beam. The calculations have been performed for two irradiation regimes: Regime A- the target is irradiated three months. Regime B- the target is irradiated three months, then is cooled without irradiation half of year, after that the target is irradiated six months. For the both cases the activity of the target has been estimated for various time intervals. Neutron spectra were calculated using intranuclear cascade model with the averaging in the target volume. The discrepancies of the integral and differential characteristics of the neutron beam created in the target by the proton beam calculated in different laboratories (LANL, PSI, ENEA, INR, KFK, JINR, ANSALDO, CDF) were analysed. These data differ in the integral characteristics not very considerably (excluding the data of ANSALDO and CDF,