Shirou Takahashi

Evaluation of Flow-Induced Vibration for Fixed Type Guide Rods of Shroud Head and Steam Dryer in ABWR

For the purpose of shortening outage schedules, fixed type guide rods are expected to be used in the ABWR. Guide rods are the component for a shroud head and a steam dryer installation. However, guide rods are located near the main steam nozzle, therefore flow-induced vibration (FIV) is concern due to the high steam velocity. In the present study, tests of the 1/1.87-scale model and computational fluid dynamics (CFD) analysis for the 1/1.87-scale test and the actual ABWR model were conducted to prove the structural integrity of fixed type guide rods against FIV. As a result of CFD calculation, reduced damping was more than 5 and reduced velocity was approximately 1.44, so resonance did not occur fixed type guide rods. The maximum fluctuating stresses were conservatively evaluated as 8 MPa by the turbulence and 2 MPa by the Karman vortex shedding. Both values were below allowable limit. As noted above, the structural integrity against FIV was confirmed, so it is feasible to use the fixed type guide rods in the ABWR. (authors)

Development of an Inertia-Increased ABWR Internal Pump

It is possible to simplify the reactor internal pump power supply system in the ABWR without affecting the core flow supply when a trip of all RIPs event occurs by eliminating the motor-generator sets and increasing the rotating inertia of the RIPs. This inertia increase due to an additional flywheel, which leads to a gain in weight and length, requires a larger diameter nozzle with a thicker sleeve. However, a thicker sleeve nozzle and a longer and heavier motor casing may change the RIP performance. In the present study, the inertia-increased RIP was verified through full-scale tests. The rotating inertia time constant for coastdown characteristics (behavior of the RIP speed in the event of power loss) for the inertia-increased RIP was doubled compared with the current RIP. The inertia-increased RIP with the thicker sleeve nozzle maintained good performance and its power supply system without motor-generator sets was judged appropriate for the ABWR.Copyright