Year
2006
Abstract
The Detective-EX handheld radionuclide identifier has proven useful in the detection and interdiction of illicit trafficking of radioactive and nuclear materials in shipments and other important situations. The high number of medical, industrial and Naturally Occurring Radioactive Materials (NORM) legitimately present in many places require that the nuclides must be accurately and rapidly identified. The RIID (Radioisotope Identifier) is used to identify the nuclides in the shipment as the second step in the interdiction process. To meet the need for detecting smaller quantities of radionuclides, a RIID with a larger HPGe detector was developed. The first instrument contained a nominal 12% (IEEE relative efficiency) detector while the new instrument contains a nominal 45% detector. This improves the sensitivity while maintaining the accurate identification of nuclides and the reduction of the false positive rate and the innocent alarm rate. In this work, the performance of the two HPGe instruments in the identification of uranium and plutonium is compared. The ANSI N42.34 requirements are the basis for the tests. Previous work also showed the performance of a HPGe-based RIID with mixtures of nuclides. The single nuclides and certain mixtures of nuclides for both shielded and unshielded sources in the standard were used. Results comparing the performance of both systems, with the standard and with each other are given. The results show the larger HPGe system provides the correct identification more rapidly on the test samples, indicating that smaller amounts of material can be detected in the specified times.