Jiguo Liu

Retrieving Fuel Elements by Pneumatic Suction in Pebble-Bed High Temperature Gas-Cooled Reactor

Spent fuel storage system of pebble-bed high temperature gas-cooled reactor needs to retrieve fuel elements and spent fuel elements from storage tank during fuel reloading condition and some other special status. This function is to be achieved by the negative pressure suction system. Research in depth is needed towards the negative pressure suction system design and experiment in order to reliably supply the system with enough suction capability and meanwhile prevent the fuel element from over-speed impact damage. A comprehensive experimental facility of negative pressure suction was built to investigate and verify the designed system. The facility mainly comprises a fuel canister, a suction tube, a tube feeder, a gas isolator, a Roots blower and pipelines. The negative pressure suction force was provided by the Roots blower and drove the fuel elements out of the canister through the tube. The Roots blower was driven by a frequency converter so that the suction flow rate could be adjusted as wanted. The dynamics model of spherical element in the tube was established. The pressure drop distribution of the negative pressure suction system was also calculated. Then the pressure drops and the sphere velocity were measured at different air flow rates. Based on the experimental results and calculation analysis, parameter requirements for the Roots pump were concluded. Therefore, fuel elements could be successfully retrieved without over-speed impact damage. These results provide useful experience for engineering design of negative pressure suction system in the spent fuel storage system.Copyright

Electromagnetic Self-Locking Device for Air Cylinders in Spent Fuel Storage System of Pebble-Bed High Temperature Gas-Cooled Reactor

In the spent fuel storage system of pebble-bed high temperature gas-cooled reactor, several air cylinders would be employed in complex machines, such as the spent fuel charging apparatus and the spent fuel canister crane. The cylinders were designed to actuate movements smoothly in radioactive environment. In order to lock them in safe position when the compressed air source is offline by accident, an electromagnetic self-locking device was designed. When power-off, the compressive spring would push out the lock plunger to enable self-lock. When power-on, the lock plunger would be withdrawn by the magnetic force of the coil to unlock the cylinder. In order to optimize the design more efficiently, numerical simulation was performed to optimize geometry parameters of the structure surrounding the working air gap so as to improve the performance of the device. A prototype was then fabricated. Combining the simulation results with experimental test, the actuating force characteristics of the device in locking and unlocking process was analyzed. The temperature rise when the device stays unlocked with power supply was also calculated and validated. The results showed that this electromagnetic self-locking device could realize the locking and unlocking functions effectively, and the maximum temperature rise also conforms the required limit. The as-fabricated device would help guarantee the fail-safe feature of the air cylinders of complex machines in compressed air outage.Copyright