Transfer cask

Use Balance weights for aircraft, high-speed rotors in gyro-compasses, y-radiation shielding, radio-isotope transportation casks and fuel element transfer casks, in general as structural material applicable to radiation shielding. 

Development of On-Site Accident Criteria for Waste Transfer Casks U.S. Department of Energy, 1989, DE89 010201 (NTIS). 

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... 

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 (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. 

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. 

Fig. 4.3. Schematic of Fort St. Vrain refueling machine. Shown are in-vessel robotic arm over the reactor core relationship of refueling machine, reactor vessel top, and reactor core and refueling machine placing fuel element in transfer cask.

After a suitable decay period, the bottom-loading transfer cask picks up the SNF assemblies from the interim decay storage vessel and transfers them out of containment to the fuel storage facility. This operation can be done after the reactor is back online. 

The cask provides the shielding, inert environment, confinement, component grappling, andl.4-kW(t) cooling capability required to handle sodium-wetted, irradiated core components. Its inside diameter isabout 8 in. The dolly provides traverse drive, cask elevation, and seismic-restraint functions. The control system provides the control consoles, motor control equipment, and all interconnecting cables. Control of the transfer cask is semiautomatic that is, key operations are automatically performed after the operator initiates a command. Interlocks are incorporated to meet safety requirements. Status lights indicate the exact machine conditions during all operations and manual overrides permit the operator to complete key operations in case of a control system failure. 

Component transfer. It is the transfer station between the bottom-loading transfer cask, which operates outside the containment area and CLEM, which remains inside the containment area and operates only when the reactor is shut down. Consequently, both the bottom-loading transfer cask rails and CLEM rails traverse the interim decay storage cover. 

Ex-vessel transfer machine (EVTM). This rail-mounted transfer cask moves core component pots (CCPs) with fresh fuel and other core components from the EVST to the reactor vessel and moves CCPs with SNF and other core components from the reactor vessel to the EVST. The CCPs are small vessels used to transfer fuel and other components in a temperature-controlled sodium environment. The EVTM is also used for fresh fuel, SNF, and other transfer operations within the reactor service building and remains in the reactor service building during reactor operations. 

MUND He Monitoring of fuel transfer casks Attribute... 

Reactor refueling occurs between 12 and 24 month intervals, depending on the fuel cycle operation and mission. A transfer cask is used to exchange spent fuel and other core assemblies in the reactor with new assemblies from the fuel service facility. 

Cask handling accident (horizontally oriented transfer cask or vertically oriented storage overpack)... 

The empty canister is raised and inserted into the transfer cask. The annulus is filled with plant water and the canister is filled with SFP water or plant demineralized water. An inflatable seal is installed in the upper end of the annulus between the canister and the transfer cask to prevent SFP water from contaminating the exterior surface of the canister. The transfer cask with the empty canister is then lowered into the SFP for fuel loading using the overhead crane. Pre-selected assemblies are loaded into the canister and a visual verification of the assembly identification is performed. 

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