Abstract
Previously, authors reported that the 14 MeV-neutron direct interrogation method has made possible to measure for the discrimination of clearance levels of concrete solidification uranium waste.
In this paper, applicability of the method to metal waste matrix is discussed based on the results of simulation experiments by the continuation energy Monte Carlo calculation code (MVP). The problem is that self-neutron moderation effect in a waste cannot be expected when a waste matrix is metal. To solve this, a moderator is adopted so as to surround a metal waste drum and to slow down suitably a 14 MeV neutrons. The simulation calculation showed that this effect is satisfactorily large. The detection limit of radioactivity concentration to 4.5% enriched uranium has been found to be 0.0973Bq/g in the metal waste model of 215.59kg gross weight, in which 61 pipes are stuffed into its drum. Moreover, the position-dependent sensitivity difference in a metal waste drum can be settled as small as to ±13.5%.
In conclusion, it can be said that 14MeV-neutron direct interrogation method can be applied to the waste of a metal system: the detection sensitivity is high enough and the position-dependent sensitivity difference is small admittedly. Hence the method can be applied also to discrimination measurement of the clearance level of metal uranium waste.
