SPECIAL TECHNIQUES FOR WIDE RANGE NEUTRON FLUX MONITORINGIN FAST REACTORS

摘要

The neutron flux monitoring system in a fast reactor totally differs with that of the any other type of reactor. High temperatures, Sodium gamma background, low shutdown neutron flux, wide range of variation of neutron flux and larger dimensions put a lot of restrictions on the choice of sensors and instrumentation. The fissions produce fast rising pulses in the neutron detectors whose frequency is a means of measuring power. These pulses are also highly statistical in nature with superimposed gamma noise. As the reactor goes from shutdown to full power, the frequency goes from 0 to 10 GHz depending on the power, which makes the further detection, amplification and processing difficult. The pulses overlap, noise gets predominant, and counting can't be done. A special technique to cover the entire 10 decade monitoring with a single kind of electronics and detector is proposed. This paper details the scheme, test results at various levels (in lab and experimental reactors) and the final proposed design.