Research On The Improvement For Nuclear Fuel Assembly Test Rig

YIBIN NUCLEAR FUEL ELEMENT PLANT (YFP), as one of nuclear fuel supplying systems, sets up synchronistically with the self-reliance policy for nuclear power plants in China, is the unique base to manufacture fuel assemblies for Qinshan NPPs Phase I and Phase II, Daya Bay NPP, LingAo NPP and Pakistan Chashma NPP. The final working procedure during the production of nuclear fuel elements is inspection of fuel assembly configuration by the test rig. The burdensome task of inspecting all the assemblies in YFP awaited the existing unique test rig imported from Germany. As the only one test rig is operating, there is a tremendous operating risk. For the reasons mentioned above, a technique improving is to be performed on a test rig imported from South Africa, and which is old and incapable for production at the present time.According to the drawings and manufacture and inspect specifications of 17x17,15x15 fuel assemblies, the final inspect items include: total length of fuel assembly, the end face parallelism between top and bottom nozzles, central straightness of fuel assembly, the torsion between top and bottom nozzles, perpendicularity error. The fuel assembly test rig should inspect the items mentioned above, show the values of the items and judge the inspecting results automatically.During this improving, the intrinsic pillar, lead rail and lead screw should be preserved and made use of, some mechanical parts should be improved and supplemented, and some appropriate design on the electrical control system should be performed. Those include improving the pedestal, top head, and preventer of the fuel assembly test rig; adopting rotary moving senser and optical scale to measure the length of 17x 17 fuel assembly; adding a measuring frame, a top head, a stand for optical scale, and adding a gear and counter weight for top head.Based on the features of the fuel assembly and the measurement principles of its test rig, it has been performed that an analysis on the potential factors (error sources) affected the measuring results of the assembly. The error sources include temperature error, measuring device error, measuring method error, mechanical accuracy error. An analysis and evaluations are completed. As a result, the main error source is the temperature one. After modifying by computer, the overall accuracy of the test rig meets the measuring requirements completely.The control system is one of the key points during the improving. The test rig should carry out functions including manual mechanical adjustments, operating for reference, single block operating and auto measuring. In accordance with the design requirements and rules, it have been elaborated that the combination, type, features and characteristics of the system hardware. The system software is also designed. It provides with HMI interface, good compatibility, accuracy, and responsibility. It has seven main menus for showing measurement, setting parameter, printing report, showing system, registration, cancellation and exit.The problems during installing and regulating have been discussed, and some relevant settling ways are also presented.