| 摘要 |
The invention concerns a method of quantitative and non-destructive measurement of fissile material based on fission induced by a pulsed neutron source. The method involves the use of a measurement head comprising a measurement chamber with the pulsed neutron source and a moderator jacket, a fission neutron counter system surrounding the jacket and consisting of a neutron moderator, neutron counter tubes and neutron filters as well as recording devices for measuring the neutron flux inside the measurement chamber and for measuring the relative strength of the pulsed neutron source. The jacket around the measurement chamber which is made from neutron-slowing materials and the neutron counter device are dimensioned so that the mean lifetime 1/ LAMBDA of the neutrons produced by the pulsed source after being slowed in the measurement chamber is significantly greater than the lifetime l/ lambda of the moderated fission neutrons in the fission neutron counter system. According to the invention, the induced fission events are correlated with the generated fission neutron signals by measuring the changes with time of the thermal neutron flux; the frequency distribution of the latter is measured in observation intervals that are periodically opened or opened by each respective fission neutron signal after each source pulse with an adjustable delay time, and the strength of the pulsed neutron source is adjusted in such a way that the correlated neutron signal pairs and triplets can be distinguished from uncorrelated pairs and triplets. |
