Tests of locking devices for the conceptual design of ARR fuel assembly

The objective of this work is to investigate the locking performance of the preliminary designed locking device for the fuel assembly of the ARR(A new Research Reactor). For this purpose, the elements of the locking devices such as bottom guide, receptacle cup and spring were fabricated. Then loading and unloading, rotating resistance, fixing status and vibration characteristics of the locking device were tested. The test results show that using the locking device with fins on the bottom guide can prevent the rotating motion of the fuel assembly. It is observed that the fixing status of the locking device in the lateral direction is incomplete and the lateral motion of the fuel assembly can be occurred due to the manufacturing tolerance of the contact surface between the bottom guide and the receptacle cup. This observation demonstrates that additional spring or guide on the top of the fuel assembly is needed to suppress the lateral motion of the fuel assembly. The vibration test results show that the effect of the contact angle between the bottom guide and receptacle cup on the 1st natural frequency of the fuel assembly is negligible. It is observed that the 1st natural frequency of the fuel assembly with locking device of surface contact type is higher than that of the fuel assembly with fin contact type locking device. In the near future, based on the experimental results, the fuel assembly of the ARR will be newly designed and tested