Advisers to the Nation on Science, Engineering, and Medicine

National Academy of Sciences

National Academy of Engineering

Institute of Medicine

National Research Council

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce Alberts is president of the National Academy of Sciences.

The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Wm. A. Wulf is president of the National Academy of Engineering.

The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an advisor to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine.

The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce Alberts and Dr. Wm. A. Wulf are chair and vice chair, respectively, of the National Research Council.

Assessment of the Practicality of Pulsed Fast Neutron Analysis for Aviation Security sprang from a 1993 request by the Federal Aviation Administration (FAA) for the National Research Council (NRC) to assist in assessing its explosives-detection program. The resulting Committee on Commercial Aviation Security (CCAS) produced two interim reports on the subject.¹ In the second report, the committee recommended that the FAA should not pursue accelerator-based nuclear detection technologies for the primary screening of checked baggage, nor should it fund any new, large, accelerator-based hardware development projects.

In 1997, the FAA funded Science Applications International Corporation (SAIC) with nearly $1 million to demonstrate the feasibility of using pulsed fast neutron analysis (PFNA) to search for small quantities of explosives in cargo containers. In conjunction with this pursuit, the FAA asked the NRC to independently evaluate the potential of PFNA. This evaluation would take into account both the earlier recommendations from the CCAS and technical developments since its previous reports.

The FAA has continued to pursue accelerator-based nuclear detection technologies that detect explosives and drugs by measuring the elemental composition of materials. These technologies exploit the high nitrogen and oxygen content found in most explosives and the high chlorine content and high carbon-to-oxygen ratio in certain drugs.² PFNA uses a collimated, nanosecond-pulse-width beam of monoenergetic fast neutrons to excite the nuclei of common elements in bulk materials.³ PFNA identifies explosives and drugs by the specific material- and energy-dependent absorption and scattering cross sections of neutrons as they interact with the nuclei of different elements. Inelastic interaction of fast neutrons with nuclei generates gamma rays. From the characteristic gamma-ray spectrum of a material, PFNA can determine its carbon, nitrogen, and oxygen content. The relative amounts of these elements can be used to discriminate explosive from non-explosive materials.

PFNA can generate three-dimensional, characteristic gamma-ray maps and is able to detect explosives and drugs hidden in vehicles and in large cargo containers. However, it also has a number of practical limitations, including large size and weight, the need for radiation shielding, difficulty in penetrating hydrogenous materials, and regulatory and safety issues associated with nuclear-based technologies.⁴

In many ways, the activities undertaken and the technology assessed by the Panel on Assessment of the Practicality of Pulsed Fast Neutron Analysis for Aviation Security are similar to those of the Panel on the Assessment of Pulsed Fast Neutron Transmission Spectroscopy.⁵ Both technologies had strong congressional backing and both have similar advantages and disadvantages.

The specific statement of task as agreed upon by both the panel and the sponsor was to evaluate the potential of PFNA for screening cargo and passenger baggage for explosives and drugs, compared with the potential of current and projected x-ray–based computed tomography (CT) systems. The panel was charged to—

• Review the laboratory-demonstrated explosives-detection performance of PFNA.

• Review, if available, laboratory-demonstrated drugs-etection performance of PFNA.

• Compare demonstrated and projected PFNA capabilities with the demonstrated and projected capabilities of x-ray radiographic and CT systems.

• Evaluate the potential preference of end users for a PFNA-based system over the currently available x-ray radiographic and CT systems.

• Outline any key assumptions that would be required to envision the use of PFNA in airports and, if

appropriate, recommend strategies to confirm these assumptions.

• Determine if PFNA has realistic potential for application to full cargo container inspection as compared with currently available x-ray radiographic and CT systems.

• Identify and prioritize research that should be pursued in the near future to further define the potential of PFNA for cargo and/or baggage screening.

It is important to note what this statement of task did not encompass. Specifically, the panel did not address cargo threats in ports of entry other than airports. Further, the panel used the threat classes as they were presented by the FAA and did not evaluate their efficacy. The panel also restricted its focus to current implementations of the technology and thus did not evaluate applications that exist outside the arena of cargo screening, nor did it conduct an exhaustive review of concepts or technical papers. Within the existing implementations, the only working prototype has been developed by Ancore Corporation. For this reason, the bulk of the analysis centers on the Ancore technology.

The panel's expectation is that this report will be read and used as a reference on the subject. For this reason, it has endeavored to be as comprehensive and detailed as possible in both the analysis and the recommendations.

The panel wishes to thank the following people for their invaluable contributions to this report. The following Ancore employees provided much assistance to the panel: Tsahi Gozani, Rob Loveman, Pat Shea, and John Stevenson. Curtis Bell of the FAA was also very helpful in acquiring information to support our study. The following people provided briefings to aid the panel: R.S. Armstrong, U.S. Customs Service; John Daly, Department of Transportation; D. Ferris, National Institute of Justice; Howard Fleisher, FAA; Richard Lacey, Police Scientific Development Branch of the British Home Office; Lyle Malotky, FAA; Carl Mosby, FAA; Richard Vigna, U.S. Customs Service; Bill Wilkening, FAA; John Pennella, U.S. Customs Service; and Paul Nicholas, U.S. Customs Service.

This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report:

Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations, nor did they see the final draft of the report before its release. The review of this report was overseen by Frank Stillinger, Princeton University. Appointed by the National Research Council, he was responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring panel and the institution.