Measurements and standards for bulk-explosives detection Larry Hudson n , Fred Bateman, Paul Bergstrom, Frank Cerra, Jack Glover, Ronaldo Minniti, Stephen Seltzer, Ronald Tosh National Institute of Standards and Technology, 100 Bureau Drive, Stop 8460, Gaithersburg, MD 20899, United States article info Available online 23 November 2011 Keywords: Security standards Bulk-explosives detection Radiation safety Technical performance Test objects Improvised-explosive devices abstract Recent years have seen a dramatic expansion in the application of radiation and isotopes to security screening. This has been driven primarily by increased incidents involving improvised explosive devices as well as their ease of assembly and leveraged disruption of transportation and commerce. With global expenditures for security-screening systems in the hundreds of billions of dollars, there is a pressing need to develop, apply, and harmonize standards for x-ray and gamma-ray screening systems used to detect explosives and other contraband. The National Institute of Standards and Technology has been facilitating the development of standard measurement tools that can be used to gauge the technical performance (imaging quality) and radiation safety of systems used to screen luggage, persons, vehicles, cargo, and left-behind objects. After a review of this new suite of national standard test methods, test objects, and radiation-measurement protocols, we highlight some of the technical trends that are enhancing the revision of baseline standards. Finally we advocate a more intentional use of technical-performance standards by security stakeholders and outline the advantages this would accrue. Published by Elsevier Ltd. 1. Introduction For better or for worse, the use of ionizing radiation to perform security screening is presently a growing industry. Governments around the world are devoting enormous resources into threat- detection technologies while attempting to manage the trade-offs between system cost and performance in the context of rapid technological change and evolving threat scenarios. While stan- dards related to radiation safety and performance of medical imaging systems have long been established, the last decade’s proliferation of security products that use ionizing radiation revealed a relative dearth of national and international standards that could be applied to the various venues and targets where security screening is now being applied in unprecedented ways. This article reviews the recent efforts by NIST and other stake- holders to fill these standards gaps, in the areas related to detection of bulk explosives by systems employing x-rays or gamma-rays. As such, these standards are a necessary component of explosives counter measures, vigorously pursued to allay potentially catastrophic economic, personal, and social costs. Standards are often invisible, and forgotten, yet they are just as often the conditiones sine quibus non that insure both the perfor- mance and the safety of a product or system. With support from the US Department of Homeland Security, this work responds to well-documented gaps in transportation and commercial secur- ity, which have been the subject of national workshops (ANSI- HSSP, 2010), presidential directives, commission reports, and recent security legislation. The goal is to help address these new formal governmental and institutional requirements for inspec- tion of baggage, cargo, vehicles, and airline passengers by assem- bling a corpus of new standards, test methods, test artifacts, dosimetry protocols, and technical guidance documents, sup- ported by an infrastructure of metrology and computational modeling. These open, consensus standards are developed under the processes and structures provided by established national and international standards development organizations (SDOs). Table 1 shows the designations by SDO of the standards covered by this project for various border, transportation, and public- location venues, column-sorted by technical performance and safety. It is useful to stress that the standards designated in Table 1 are measurement standards, providing tools with which to dis- criminate between competing products, insure their safe use, and gage their appropriateness for the task and performance over time. These standards are finding increasing use in national and international settings through close cooperation between US governmental agencies, industrial partners, and foreign partners. In this paper we first review the area of radiation safety, with particular focus on the screening of human subjects with ionizing radiation. Then we cover the technical performance standards for Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/apradiso Applied Radiation and Isotopes 0969-8043/$ - see front matter Published by Elsevier Ltd. doi:10.1016/j.apradiso.2011.11.029 n Corresponding author. E-mail address: larry.hudson@nist.gov (L. Hudson). Applied Radiation and Isotopes 70 (2012) 1037–1041