Source Replacement Project for Nuclear Smuggling Detection and Deterrence Radiation Portal Monitor Functional Compliance Tests

The Nuclear Smuggling Detection and Deterrence (NSDD) program utilizes technical expertise from National Laboratories to provide partner countries with the capability to deter, detect, and investigate smuggling of nuclear and radiological material. To accomplish this, NSDD is engaged internationally with training personnel and deploying equipment, such as Radiation Portal Monitor (RPM) systems. To ensure that the equipment operates to standards, NSDD and its partners perform regular functional compliance tests. For RPMs, these function tests are performed using test sources to verify adequate detector efficiency in the hypothetical presence of special nuclear material. Currently, verifying desired detector gamma and neutron efficiency performances relies on Co-57 and Cf-252. Due to their short halflives (272 days and 2.65 years, respectively), these sources must be replaced frequently at considerable expense to the program. Ideal sources to replace Co-57 and Cf-252 should be readily available commercially, exhibit a similar emission profile to the source material seeking to be detected, and possess substantially longer halflives. In the following research, Am-241, and Cs-137 were studied as potential replacements for Co-57, while AmBe was studied as a potential replacement for Cf-252. As part of a student internship in Los Alamos, an approach was developed for executing verification and validation of experimental data acquired at three DOE laboratories on nine RPM systems. Los Alamos National Laboratory, Oak Ridge National Laboratory, and Pacific Northwest National Laboratory acquired deadtime and efficiency data on vehicle, rail, pedestrian, and mobile RPM systems with a variety of sources. The outcomes of the measurements, and importance of including robust verification and validation procedures will be presented in this paper. The results indicate that Am-241 and AmBe would be acceptable replacements for Co-57 and Cf-252. Replacing the traditional sources with these new sources, would be a significant cost saving measure for the program.