Nuclear Forensics

Charter and background

This report was produced by a joint Working Group (WG) of the American Physical Society (APS) Panel on Public Affairs and the American Association for the Advancement of Science (AAAS) Center for Science, Technology and Security Policy. The primary purpose of this report is to provide the Congress, U.S. government agencies and other institutions involved in nuclear forensics with a clear unclassified statement of the state of the art of nuclear forensics; an assessment of its potential for preventing and identifying unattributed nuclear attacks; and identification of the policies, resources and human talent to fulfill that potential. The WG formally met twice, once in Washington, D.C., and once in Palo Alto, California, to hear presentations from staff of the DOE/NNSA, the DHS, the DOS, the DTRA, and Congress. The sessions were unclassified, although several members of the WG have access to classified material.

Nuclear forensics, the analysis of nuclear materials recovered from either the capture of unused materials, or from the radioactive debris following a nuclear explosion, can contribute significantly to the identification of the sources of the materials and the industrial processes used to obtain them. In the case of an explosion, nuclear forensics can also reconstruct key features of the nuclear device. Nuclear forensic analysis works best in conjunction with other law enforcement, radiological protection dosimetry, traditional forensics, and intelligence work to provide the basis for attributing the materials and/or nuclear device to its originators. Nuclear forensics is a piece of the overall attribution process, not a stand-alone activity.

A believable attribution capability may help to discourage behavior that could lead to a nuclear event. The chain of participants in a nuclear terrorist event most likely includes a national government or its agents, since nearly all nuclear weapons usable material is at least notionally the responsibility of governments. A forensics capability that can trace material to the originating reactor or enrichment facility could discourage state cooperation with terrorist elements and encourage better security for nuclear weapon usable materials. In addition, most terrorist organizations will not have members skilled in all aspects of handling nuclear weapons or building an improvised nuclear device. That expertise is found in a small pool of people and a credible attribution capability may deter some who are principally motivated by financial, rather than ideological, concerns.

There is an important difference between nuclear forensics as it is practiced today and the analysis of foreign nuclear tests as it was practiced during the Cold War and for some time thereafter, even though both rest on the same scientific base. Nuclear forensics for attribution involves comparing data and analyses from the samples recovered to data and analyses from samples from identified sources. Forensic analysis for attribution therefore requires that data concerning foreign-origin material be available. Some of these data exist in the U.S. but many more reside abroad, in international and national databases, in sample archives, and elsewhere. Therefore, nuclear forensic analysis would benefit from as much international cooperation as possible.

Following a nuclear explosion, trained forensics teams would need to promptly gather highly radioactive samples from fallout and from the atmosphere. These samples then would have to be safely and promptly transported to U.S. and possibly other laboratories. Close coordination among the FBI (if the explosion occurs in the U.S.) and/or local authorities (if elsewhere), first responders and forensics teams is necessary.

Nuclear forensics results such as origin and history of materials and type of explosive device are not available immediately. Some constraints come from nature, some from personnel and equipment availability, some are due to the iterative nature of interpreting nuclear data, where initial results are fed into computer codes before being subject to further analysis. Political leaders will face a period of uncertainty that could range from days to months, during which forensics and other attribution information gradually becomes available.

Nuclear forensics relies on physical, isotopic and chemical analysis of radioactive and sometimes microscopic quantities of materials, including impurities and such things as crystal structures and surface finishes where available. Facilities for such analyses exist at the U.S. DOE laboratories and, on various scales, at a number of IAEA, foreign government and university laboratories around the world. A number of these facilities participated in the analysis of intercepted nuclear weapon usable materials in the past several years. In the event of a nuclear detonation or other nuclear emergency, U.S. facilities would be badly stretched in several respects. The trained specialists needed are too few and would be overcommitted; a high proportion of them are close to retirement age and the ability to replace them and augment their number is inadequate and under funded. Laboratory facilities are not up to the most modern and effective standards that prevail in some other countries such as Japan and France. Specialized field-deployable equipment to make key early measurements in the affected area needs to be improved and tested. As a result, there could be unnecessary delays of days or more in getting forensic results of importance to the overall process of attribution, at a time when it can be readily foreseen that there would be very high pressure for reliable attribution data if the origin of a nuclear explosion were undetermined.

Nuclear forensics remains a technically complex challenge for the scientific and law enforcement communities. The difficulty in successful forensics work, especially as part of an attribution process, should not be underestimated. However, the potential for nuclear forensics to play a crucial role in analysis of both pre- and post-detonation materials is enormous. The problems of a declining pool of technically competent scientists, the need for new technology, and the utility of international cooperation, all point to the need for a set of new initiatives in order to maximize the potential impact of nuclear forensics.