Year
1970
Abstract
The nuclear safeguards research and development program at the Los Alamos Scientific Laboratory is involved in the development of techniques and instrumentation for inspection and measurement of fissionable material. Such technology is fundamental to nuclear safeguards and efficient nuclear materials management as well as to safety, accountability, and quality control of nuclear materials throughout the nuclear industry. To be most useful, physical assay techniques should be nondestructive, rapid, accurate, reasonably simple, and adaptable to a wide range of laboratory, in-plant, and field conditions encountered in the nuclear industry. The difficulties of representative sampling in chemical (destructive) assay of heterogeneous materials are largely obviated in the new nondestructive assay methods, mainly because of their characteristic high penetrability through bulk materials. Nondestructive assay techniques can be separated into two main categories - passive and active. Some passive assay methods have been in use for many years, and in addition new techniques and instrumentation are still being developed. Passive assay methods involve the observation of naturally occurring neutron and gamma radiations from the fissionable materials. These passive \"signatures\" are often adequate for assay applications, especially in the case of Pu. However, for many assay applications the passive signature is too weak or of limited penetrability as is the case for 235U. Also, for the case of \"spent\" reactor fuel, the passive signatures are masked by the high radiation level of the sample. Some new developments in passive assay instrumentation and applications will be described in a later section of this paper.