Year
2000
Abstract
Gamma rays are ideal probes for the determination of information about the special nuclear material that is in the transparency regime. Gamma rays are good probes because they interact relatively weakly with the containers that surround the SNM under investigation. In addition, gamma rays carry a great deal of information about the material under investigation. We have leveraged these two characteristics to develop three technologies that have proven useful for the measurements of various attributes of plutonium. These technologies are Pu-300, Pu-600 and Pu-900. These technologies obtain the age, isotopics and presence/absence of oxide of a plutonium sample, respectively. Pu-300 obtains the time since the last 241Am separation for a sample of plutonium. This is accomplished by looking at the 241Am/241Pu ratio in the energy region from 330-350 keV, hence the name Pu-300. Pu-600 determines the isotopics of the plutonium sample under consideration. More specifically, it determines the 240Pu/239Pu ratio to determine if the plutonium sample is of weapons quality or not. This analysis is carried out in the energy region from 630-670 keV. Pu-900 determines the absence of Pu02 by searching for a peak at 870.7 keV. If this peak is absent then there is no oxide in the sample. This peak arises from the de-excitation of the first excited state of 17O. The assumption being made is that this state is populated by means of the 17O(~,~’) reaction. The first excited state of 17O could also be populated by means of the 14N(~,p) reaction, which might indicate that this is not a good signature for the absence of Pu02 , however in the samples we have measured this peak is visible in oxide samples and is absent in other samples. In this paper we will discuss the physics details of these technologies and also present results of various measurements.