Reactor Oscillator Method To Measure Small Reactivity Technology Research

Reactivity is the most important kinetic parameters in pile neutron physics,which is a measure of extent that reactor has deviated from the critical point.Precise measurements of reactivity are not only benefit to safe operations of reactor,but also a significant means to verify the validity of physical model of reactor and nuclear data library.The pile oscillator method is the most accurate method to measure small reactivity when the reactor is in a critical condition.The experiments of adopting the pile oscillator method to measure small reactivity are very few in domestic,and there is no open literature about the measurement technique of pile oscillator method.This paper aims to establish the measuring method of pile oscillator.Several key problems of measuring small reactivity in pile oscillator method are studied:the data processing algorithm,the selection of experimental condition,the designing of measurement system.In terms of data processing,we write the algorithm based on correlation analysis.The practice shows that the correlation analysis is suitable for data processing of pile oscillator method.This algorithm can filter the noise signal and harmonic signal in the changing curve of reactor power,and get accurate amplitude of the reactor power oscillation.And in terms of the selection of experimental condition,this paper reagards the fast burst reactor(CFBR-?)as the research object.In order to select the optimal conditions of experiment,several major error factors are analyzed by numerical simulation and derivations of formulas.According to the research,the optimum experiment conditions were selected:the reactor should be maintained critical;the frequency of reactivity oscillation should choose in the flat areas of the transfer function curve;the magnitude of the relative change of reactor power should be no more than 4%.Finally,we have built a pile oscillator measurement system in the CFBR-?,the measuring device is composed of simple apparatus in lab.Via the measurement system,we have measured the reactivity oscillation amplitude when a rotating platform carrying a polyethylene sample rotates outside of the reactor.The result of measurements by pile oscillator method and inverse kinetics method are agreement within 1%.Through the research and experiment work of this paper,the key technology of pile oscillator method for measuring small reactivity is mastered,and the pile oscillator measurement system is successully built in the CFBR-II reactor.