Research On Application Of Optical Fiber Temperature And Differential Pressure Sensors In Nuclear Power Plants

Optical fiber sensors have advantages of small size,light weight,antielectromagnetic interference,stability,etc.Many researchers have studied their applications in the nuclear radiation environments.Although optical fiber sensors have formed a variety of products suitable for different environments over many years,with the development of sensing and measurement,the stability and precision of optical fiber sensors have been put forward higher requirements.For the measurement of temperature and differential pressure in nuclear power plants,traditional electronic sensors are more difficult to work in high temperature environments.Therefore,this paper proposes the use of optical fiber sensors in the radiation environments,including temperature sensors of two types: fiber Fabry-Perot(F-P)sensors and fiber Bragg grating(FBG)sensors,and FBG differential pressure sensor.This article investigates the research of optical fiber sensors at home and abroad under nuclear radiation environment.The temperature sensitivity of the designed F-P temperature sensor is about 12.0 pm/ ?,and the temperature sensitivity of FBG temperature sensors is about 12~14 pm/?.FBGs are written using femtosecond laser to improve the radiation stability.The characteristics of FBGs are studied after gamma radiation.Radiation will cause the center wavelength of FBG display a shift.In order to reduce the effect of irradiation on FBGs,the method of thermal annealing is considered.After 2 MGy gamma radiation,the temperature characteristics of irradiated and nonirradiated FBGs are compared.Radiation makes temperature sensitivity of FBGs unstable.Aiming at using the temperature sensor interface under the gamma radiation environment,a package suitable for the optical fiber temperature sensor is designed.Based on the strain principle,two kinds of optical fiber FBG differential pressure sensors were designed and manufactured,and they were tested experimentally.The cantilever beam was used to test the strain characteristics of FBG.Based on the experiment,dual-diaphragm and single-diaphragm differential pressure sensor was designed.The dual-diaphragm differential pressure sensor has a larger structure.In order to be used in a nuclear irradiation environment,it is heavier and less sensitive after being fully metal-encapsulated.The design of the single-diaphragm differential pressure sensor simplifies the structure.Through the experimental verification,it isfound that the combined calculation of 8 positive and negative FBGs has a differential pressure sensitivity of 35.0 pm/kPa.In order to further reduce the size of the differential pressure sensor,a better scheme was designed,and the scheme was simulated and analyzed.