Target Transfer Cask

Radiological (airborne release) Target/transfer cask breach releases target volatiles outside, in Zone 2, in STB, or in Zone 2A canyon (TT-3, TT-4, CP-1 CP-3) III IV D 4... 

Fire (radiological and toxic material) Forklift fire incident causes transfer cask breach with possible target exposure and airborne release Failure of electrical equipment or system in SCBs, SGB, ventilation hood, Zone 2 or Zone 2A canyon Lightning strike External fire (vehicle accident, aircraft crash, other building fire) irradiated isotope production target, up to 20,000 curies. Volatiles in process cold traps, up to 70,000 curies. Same material as toxic spill. Residual radiological contamination. 

Radiological (direct Transfer cask breach exposes target in forklift incident (TT-1 through TT-4) III D 4... 

Fire (radiological and toxic material) Forklift fire incident causes transfer cask breach with possible target exposure and airborne release (TT-4 CP-1) IV D 4... 

The shielded transfer casks for irradiated target transfer from the ACRR to the HCF. 

The potential initiating events, preventive features, and mitigating features were evaluated using event tree analysis methodology, which is detailed in Appendix 3E. The analysis showed that the accident risk could be conservatively bounded by a worst case crash of the forklift with target into fixed, unyielding features at the entrance to the HCF. The expected orientation in a collision impact would be a side impact of the cask. Structural analysis of the isotope transfer cask indicates that the cask will not be broken or breached in a conservatively worst case collision. 

Exposure of the forklift operator transporting the cask is estimated to be less than 1 mrem (whole-body) per target transfer, based on a 30 minute transfer operation with the cask positioned on the forklift so that the cask is approximately 3 feet from the operator s abdomen. 

The Target Entrance System (TES) mechanical interlock provides a worker safety function by preventing the removal from the TES of a shield cask containing an irradiated target without the shield cask lid properly installed. This interlock is relevant to both of the operational modes, since target transfer operations could be accomplished in either of these modes. 

The shield cask provides a worker safety function by shielding personnel from irradiated targets during target transfer between the Annular Core Research Reactor high-bay and the HCF target entrance system. 

For this DBA, the undesired event is release of the target from the transfer cask and target breach. Failure frequencies for the various nodes were developed from (Mahn et al. 1995) and (DOE 1996). The ET analysis diagram is shown in Figure 3E.1-2. This figure does not include a fire of the forklift fuel. The outcomes of the ET analysis In Figure 3E.1-2 are shown as eleven branches. The outcomes represent the following detailed accident occurrence scenarios. 

The shield cask serves to provide radiation shielding for facility workers during the transfer of irradiated targets from the ACRR core to the HCF steel transfer box. The thickness of DU in the cask is sufficient to reduce the dose rate from a Mo-99 target irradiated for 7 days at 20 kW fission power followed by a 6-hour decay to approximately 5 mR/hr on contact... 

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