Domestic Nuclear Detection Office

Under the Coordinated Research Project M22.007, Development and implementation of instruments and methods for detection of unauthorized acts involving nuclear and other radioactive material, the IAEA, in cooperation with U.S. National laboratories established an evaluation campaign to assess the performance of radiation detection equipment for nuclear security applications. The study targets instruments featuring radionuclide identification: spectrometric portal monitors, radionuclide identifiers, spectrometric portable radiation scanners, etc. The evaluation takes a semi-empirical approach, utilizing the instruments' replay and re-evaluation capabilities, also known as injection studies.

This article presents the evolution of the International Electrotechnical Commission (IEC) and the European standards for individual monitoring of ionising radiation issued, respectively, from the committees IEC/Sub Committee 45B and European Committee for Electro-technical Standardization/Technical Committee 45B 'Radiation protection instrumentation'. Standards for passive individual photon and beta dosimetry systems as well as those for active individual monitors are discussed. A neutron ambient dose equivalent (rate) meter standard and a technical report concerning the determination of uncertainty in measurement are also covered.

This report documents a study to eliminate ambiguity in identifying a very low-yield nuclear detonation in the early stages of the response to such an event. The ambiguity arises from the very similar explosive and radiation effects produced by three categories of explosive devices: An explosively driven radiological dispersal device (RDD) or an accidental explosion in which radiologic material is scattered by chemical explosives. A failed nuclear device in which nuclear material, such as uranium or plutonium, has been scattered by conventional explosives. A nuclear device that, in addition to scattering nuclear material, produced a very low-yield from nuclear fission. The study found that the properties of fission products provide a ready solution to the problem. The radiation dose rate from fission products that were produced in a nearly instantaneous “fission event” decreases extremely rapidly over the first eight hours after that event, whereas nuclear materials and common radiological materials produce an essentially constant dose rate. This contrast provides an unequivocal fission product signature. The measurements required to utilize this signature can be made by first responders with radiation detectors already in the field, on time scales of an hour, although later confirmation using more capable detectors, including spectroscopic capability, is advised. The process of categorizing an explosives-related incident, both pre- and post-detonation, can be represented as a Decision Tree. The Decision Tree illustrates the use of already-fielded radiation detectors to categorize incidents as likely to involve only conventional explosives, an explosively driven RDD, or a nuclear device. The identification of an explosion as a fission event is extremely important to evacuation planners. It has been shown that delayed evacuation after sheltering in place for up to 24 hours after a fission event has the potential to reduce radiation exposure to the affected public and responders by a factor of ten. Traditional evidence collection after a nuclear detonation is likely to be similarly delayed, as the value and urgency of collection efforts must be weighed against radiation and other hazardous exposure of the collectors. The evidence that survives the immediate effects of a nuclear detonation will, in many cases, still be available for collection once radiation levels have diminished to acceptable levels. Certain classes of evidence, notably information stored on digital media, may significantly degrade from exposure to post-detonation radiation fields. Technical nuclear forensics collections will be performed in all events with nuclear yield. Modification of the high-yield collection strategy may be necessary for a very low-yield device.

To combat the threat of nuclear terrorism, the Domestic Nuclear Detection Office (DNDO) was established within the U.S. Department of Homeland Security to focus efforts on developing and enhancing radiological and nuclear detection and national technical nuclear forensics capabilities. With respect to nuclear detection, we at DNDO, in concert with interagency partners, are developing and enhancing a multi-faceted, layered, defense-in-depth framework to make prohibitively difficult the importation, possession, storage, development, transportation, or use of nuclear or other radioactive material that is out of regulatory control. In furtherance of this framework, we conduct research and development on detection and forensics technologies, characterize system performance, acquire and deploy detection systems, and support operational partners with the development of programs to effectively perform detection operations. To support the U.S. Government’s (USG) attribution process, we focus on improving the readiness of the overarching USG forensic capabilities; advancing the technical capabilities to perform forensic analyses on pre-detonation nuclear and other radioactive materials; and building and sustaining an expertise pipeline for nuclear forensic scientists. These efforts, coupled with the work of interagency partners, will advance USG capabilities to detect and interdict a nuclear threat and hold accountable those who are responsible for such actions.