Study On The Optical Method For The Prestressed-strain Loss Monitoring Of The Anchor Cable Embedded In Nuclear Containment Vessel

Nuclear power plant concrete containment vessel is a key part to prevent nuclear accident damage.The state of the prestressed anchor cable is a direct measure of its strength.The past experience showed that the nuclear containment vessel prestressed anchor cable with a very slow strain loss.At present,the monitoring methods can not meet the requirement of the extremely slow changes of prestressed strain loss.Thus,there are two requirements:one is the long-term,quite slow monitoring and the other is the high precision monitoring of the prestressed strain loss for anchor cable in nuclear containment vessel of the nuclear power station.Based on the principle of white-light optical Michelson interference,a pressure ring fiber optic white light interference sensor was designed.The sensor could carried out a long-term high-precision measurement.It provided a feasible method for monitoring of the prestressed strain loss for anchor cable,after the corresponding experimental test and data processing.In addition,the long-term usage of the white-light interferometer required a low consumption in its power supply.The interferometer was optimized based on the Field Programmable Gate Array（FPGA）.The power consumption of the white-light interferometer was reduced about5W.The main work was list as following:1.A white light interference sensor was introduced to monitor the prestressed strain loss of anchor cable in nuclear containment vessel.In this paper,the pressure ring elastomer was designed.It could be installed at the anchorage of the nuclear containment vessel.And the prestressed strain loss of anchor cable was reflected by measuring the deformation of pressure ring.Thus,The mechanical design and the ANSYS finite element analysis of the pressure ring was carried out.Through the calculation and analysis,the shape variable in the middle part of the pressure ring was obvious.Under the vertical load of 3050KN,the increment of tensile strain could approach-0.889?10^-4（minus sign indicated concave inward）.According to the simulation analysis,the sensing fiber was wound around the middle part of the pressure ring elastomer.The loading and unloading tests were carried out under 5000KN press machine.The curve of variation obtained by data processing had good linearity and repeatability.This presented a new way for monitoring of the prestressed strain loss for anchor cable in containment vessel of nuclear power station.2.Based on the FPGA technique,the scanning module,data acquisition and transmission module of the interferometer had been optimized in both hardware and software.A communication protocol was created to realize the flexibility data transfer with a personal computer in data collection station.Combining the advantages of FIFO with DDR3 SDRAM,a large capacity asynchronous FIFO cache system was designed based on AXI4.In this paper,UART data transmission format,AD7606 acquisition card timing,Ethernet UDP communication protocol,and AXI4 bus protocol were introduced.Based on these principles,all modules were integrated through debugging and testing.Then the FPGA system could implement the step motor control and realize the data acquisition and transmission.In summary,according to the requirements of the sensor for monitoring of the prestressed strain loss of the anchor cable in containment vessel of the nuclear power station,the mechanical design,simulation analysis and pressure test under laboratory conditions of the pressure ring was carried out.In order to optimize the power consumption performance of the white light interference system,the hardware and software of some modules were designed based on the FPGA technique.This achievement had made a good basis on the future practical usage of this white-light technique to monitor the prestressed strain loss of the anchor cable embedded in containment vessel of the nuclear power station.