Kouji Shiina

Experimental Study on Thermal Striping in Mixing Tees With Hot and Cold Water

Thermal striping tests in mixing tees with hot and cold water were conducted for three types of flow conjunctions in order to establish an evaluation method for high-cycle thermal fatigue of piping systems. Two kinds of examinations were planned. The preliminary tests were flow visualization tests carried out using acrylic pipes to obtain flow pattern characteristics and flow temperature fluctuations. The main tests were temperature fluctuation measurement tests carried out using metal pipes to evaluate the unsteady heat transfer coefficient based on measured temperature fluctuations of fluid and pipe wall. This paper reports visualization test results. The flow patterns were visualized by injection of methylene blue and compared with flow analysis results by the k-e turbulence model. Temperature fluctuations of fluid 3mm from the inner pipe wall were measured with C-A thermocouples. Fundamental features such as locations with a large fluctuating temperature, the fluctuating temperature amplitude and its frequency were identified.Copyright

Transition period fuel cycle from current to next generation reactors for Japan

Long-term energy security and global warming prevention can be achieved by a sustainable electricity supply with next generation fast breeder reactors (FBRs). Current light water reactors (LWRs) will be replaced by FBRs and FBR cycle will be established in the future considering the limited amount of uranium (U) resource. The introduction of FBRs requires plutonium (Pu) recovered from LWR spent fuel. The authors propose advanced system named “Flexible Fuel Cycle Initiative (FFCI)” which can supply enough Pu and hold no surplus Pu, can respond flexibly the future technical and social uncertainties, and can achieve an economical FBR cycle. FFCI can simplify the 2nd LWR reprocessing facility for Japan (after Rokkasho Reprocessing Plant) which only carries out U removal from LWR spent fuel. Residual “Recycle Material” is, according to FBRs introduction status, immediately treated in an FBR reprocessing to fabricate FBR fuel or temporarily stored for the utilization in FBRs at necessary timing. FFCI has high flexibility by having several options for future uncertainties by the introduction of Recycle Material as a buffer material between LWR and FBR cycles.

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)