The Design Of Reactor Power Monitor Based On ¹⁶N? Energy Spectrum Measurement

Reactor power is a significant parameter for nuclear power plants'safety and control.Accurate measurement of nuclear reactor power is of great importance to the safe operation of the reactor in many important nodes,such as nuclear reactor start-up,increasing power,full power operation,and power reduction operation.Therefore,the design of the reactor power measurement instrument follows the principle of diversity.Generally multiple measures are adopted to monitor the reactor power to ensure the safety of the reactor,such as various kinds and redundant design.The ¹⁶N concentration in the primary loop of the nuclear reactor has a linear relationship with the reactor power.By online monitoring the ¹⁶N?radioactivity in the primary loop,the nuclear reactor power can be measured efficiently and quickly.At present,¹⁶N power monitor systems mostly use the method of ¹⁶N total gamma dose measurement in domestic.that is,it monitors the reactor power by detecting the ¹⁶N total?radioactive intensity of main pipe of the primary loop.However,there are many other activated and fission?radionuclides in the primary loop,which is a certain interference to the method of the ¹⁶N total?dose monitoring reactor power.This paper studies the reactor power measurement method based on ¹⁶N?energy spectrum for purpose of eliminating the interference of other?radionuclides in the water of the main pipe,which can measure the reactor power more accurately.It is of practical value.The main research of the thesis is as follows:1.Establish a theoretical model for monitoring reactor power based on¹⁶N?energy spectrum.2.Because ¹⁶N?radioactivity is too high in the primary loop,MCNP is used to optimize the simulation of the shielding design of the reactor power monitor based on ¹⁶N?energy spectrum measurement.So that after setting a reasonable shielding,the NaI detector can obtain a good ¹⁶N?energy spectrum and have a high enough counting rate when running at full power.?1?On account of the source system is large and the particle penetration probability is small,the Monte Carlo simulation result is too small,resulting in a large simulation error,and may not even get the simulation result.In this paper,multiple MCNP simulation methods are used for comparison,such as direct calculation,segmentation and dose estimation.?2?The calculation of the lead chambers with different thicknesses without the collimating aperture is used to select the lead chamber shielding based on shielding most of the?rays of the main pipe and reducing the NaI detector counting rate to a lower range by the source item analysis.The lead thickness is set to18cm eventually.?3?MCNP software is simulated when the size of collimating aperture was selected as 0.5cm,1cm and 2cm.Analyzing through the appropriate range of detector counting rate,the size of collimating aperture is selected as1cm.According to the above simulation data,the lead shielding of ¹⁶N monitor was designed and processed.3.Establishing the experimental measurement system based on ¹⁶N?energy spectrum monitoring reactor power,the detector was debugged,and the energy calibration experiment was conducted by using PuC source which emits 6.13MeV?ray,¹³⁷Cs source which emits 0.662MeV?ray,⁶⁰Co source which emits 1.173MeV and 1.332MeV?rays.