Nuclear Weapons Materials Research Articles

A comparison of two micro-beam X-ray emission techniques for actinide elemental distribution in microscopic particles originating from the hydrogen bombs involved in the Palomares (Spain) and Thule (Greenland) accidents

In order to validate and to gain confidence in two micro-beam techniques: particle induced X-ray emission with nuclear microprobe technique (μ-PIXE) and synchrotron radiation induced X-ray fluorescence in a confocal alignment (confocal SR μ-XRF) for characterization of microscopic particles containing actinide elements (mixed plutonium and uranium) a comparative study has been performed. Inter-comparison of the two techniques is essential as the X-ray production cross-sections for U and Pu are different for protons and photons and not well defined in the open literature, especially for Pu. The particles studied consisted of nuclear weapons material, and originate either in the so called Palomares accident in Spain, 1966 or in the Thule accident in Greenland, 1968. In the determination of the average Pu/U mass ratios (not corrected by self-absorption) in the analysed microscopic particles the results from both techniques show a very good agreement. In addition, the suitability of both techniques for the analysis with good resolution (down to a few μm) of the Pu/U distribution within the particles has been proved. The set of results obtained through both techniques has allowed gaining important information concerning the characterization of the remaining fissile material in the areas affected by the aircraft accidents. This type of information is essential for long-term impact assessments of contaminated sites.

Global Risk of Nuclear Terrorism

The emergence of nuclear terrorism, a threat that President Obama called "the gravest danger we face," has signaled a paradigm shift in international security. Since the collapse of the Soviet Union, sensitive nuclear technologies and materials have become increasingly available. Globalization and the inadequate enforcement of treaties and export controls have allowed the proliferation of nuclear weapons materials. Today, international terrorist organizations seek to employ weapons of mass destruction (WMD) as a means to influence national policies around the world. AlQaida spokesman Suleiman Abu Gheith declared that in order to balance the injustices that have been inflicted on the Muslim population worldwide, al-Qaida's new objective is "to kill 4 million Americans–2 million of them children." As political scientist Graham Allison notes, this could be achieved with either 1,334 attacks similar in magnitude to those of 9/11, or one nuclear bomb.Building a nuclear program is an arduous task that requires tacit knowledge, the recruitment of nuclear scientists, engineers, and machinists, and the resources and time to obtain nuclear materials and components. While it is unlikely that terrorist organizations have the capacity to develop full-fledged programs in the near term, terrorist development and acquisition of nuclear weapons remains a long-term threat that requires international action.

Assurance of Supply: A New Framework for Nuclear Energy

are driving a potential expansion in the use of nuclear energy. Dozens of states have approached the International Atomic Energy Agency (IAEA) for guidance as they explore the possibility of building nuclear power reactors for the first time. With an expansion and spread of nuclear energy will come an expanded demand for nuclear fuel, and for the management of spent nuclear fuel. Where will the fuel supply for an expanded global reactor fleet come from? Will it remain in the hands of existing suppliers, with expanded capacity? Will new states develop their own national enrichment capabilities, adding to the number of states with the capacity to produce either fuel for nuclear power reactors or material for nuclear weapons? Or will multilateral nuclear fuel cycle facilities emerge to meet expanding demand? Many IAEA member states have expressed mounting concern over the risks that could be created by the further spread of technologies such as uranium enrichment or plutonium reprocessing—key technologies for the production of fuel for nuclear power reactors that could also be used to produce material for nuclear weapons. The convergence of these realities points to the need to develop a new framework for the nuclear fuel cycle that provides reliable and predictable access to nuclear fuel and power reactors while strengthening the Nuclear Non-Proliferation Treaty (NPT) regime. Establishing a framework that is equitable and accessible to all users of nuclear energy acting in accordance with agreed nonproliferation norms will be a complex endeavor and should be addressed through a series of interlinked, progressive steps. The first step would be to establish mechanisms that provide assurance of the supply of fuel for nuclear power reactors—and, as needed, assurance of the acqui-

Gas Centrifuge Theory and Development: A Review of U.S. Programs

This article gives a historical and technical review of the U.S. gas centrifuge efforts between 1934 and 1985. The first section tells of how the United States initially led in centrifuge design, only to abandon the still-immature technology in the midst of the Manhattan Project. While interest in the technology continued in Europe, the United States decided that centrifuges were not a viable alternative to existing gaseous-diffusion plants. Five years later, U.S. spies learned of important Soviet achievements in centrifuge design, which, it appeared, might place centrifuges in direct competition with gaseous diffusion. When combined with European enthusiasm for the centrifuge, the United States faced the prospect of losing its control on the enrichment market in the West. Accordingly, the United States organized a program to rebuild its centrifuge dominance. Over the next 25 years, it led the world in machine performance but ultimately failed to commercialize its designs for a variety of reasons. The basic specifications and performance data for several of the U.S. centrifuges designed and tested during these years are reported here for the first time in the public domain. The United States also made a number of contributions in the theoretical domain that were openly shared over the course of the U.S. program. Most of these fell into the field of fluid dynamics, developed to guide the design and optimization of centrifuges. The most important elements, especially those relating to the calculation of separative power, are described in Theoretical Developments. These are of interest to policy-makers because they can be used to predict the rate at which centrifuges produce fissile material for nuclear weapons, an important factor for nuclear nonproliferation. They are also used in calculations related to multi-isotope separation, which is important for nuclear forensics. Examples of both kinds of policy analysis are given in articles by Glaser1 and Wood2 appearing in an earlier issue of Science and Global Security. The U.S. theory is used here to derive a simple equation that enables policy-makers to make good estimates for the separative power of a real centrifuge by knowing only its length and speed.

Hanford remediation at 20 years: A glass half‐empty

AbstractThe U.S. Department of Energy's (US DOE's) responsibilities for its former national nuclear weapons complex include remediation of the Hanford Site in Washington State. In 1989, the site's primary mission shifted from nuclear weapons material production to cleanup of the extensive radioactive and chemical contamination that represented the production legacy. Cleanup is governed by the Tri‐Party Agreement (TPA), between the US DOE, as responsible party, and the U.S. Environmental Protection Agency and Washington State Department of Ecology, as joint regulators. Nearly 20 years have passed since the TPA was signed, but the Hanford remediation is expected to require decades longer. This article covers the cleanup progress to date and challenges that remain, particularly from millions of gallons of highly radioactive liquid wastes and proposals to bring new wastes to Hanford. © 2008 Wiley Periodicals, Inc.

The Use of SIMS and SEM for the Characterization of Individual Particles with a Matrix Originating from a Nuclear Weapon

The application of scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS) for characterization of mixed plutonium and uranium particles from nuclear weapons material is presented. The particles originated from the so-called Thule accident in Greenland in 1968. Morphological properties have been studied by SEM and two groups were identified: a "popcorn" structure and a spongy structure. The same technique, coupled with an energy-dispersive X-ray (EDX) spectrometer, showed a heterogeneous composition of Pu and U in the surface layers of the particles. The SIMS depth profiles revealed a varying isotopic composition indicating a heterogeneous mixture of Pu and U in the original nuclear weapons material itself. The depth distributions agree with synchrotron-radiation-based mu-XRF (X-ray fluorescence microprobe) measurements on the particle (Eriksson, M., Wegryzynek, D., Simon, R., & Chinea-Cano, E., in prep.) when a SIMS relative sensitivity factor for Pu to U of 6 is assumed. Different SIMS identified isotopic ratio groups are presented, and the influence of interferences in the Pu and U mass range are estimated. The study found that the materials are a mixture of highly enriched 235U (235U:238U ratio from 0.96 to 1.4) and so-called weapons grade Pu (240Pu:239Pu ratio from 0.028 to 0.059) and confirms earlier work reported in the literature.

A nondestructive method for discriminating MOX fuel from LEU fuel for safeguards purposes

Plutonium-rich mixed oxide fuel (MOX) is increasingly used in thermal reactors. However, spent MOX fuel could be a potential source of nuclear weapons material and a safeguards issue is therefore to determine whether a spent nuclear fuel assembly is of MOX type or of LEU (Low Enriched Uranium) type. In this paper, we present theoretical and experimental results of a study that aims to investigate the possibilities of using gamma-ray spectroscopy to determine whether a nuclear fuel assembly is of MOX or of LEU type. Simulations with the computer code ORIGEN-ARP have been performed where LEU and MOX fuel types with varying enrichment and burnup as well as different irradiation histories have been modelled. The simulations indicate that the fuel type determination may be achieved by using the intensity ratio 134Cs/ 154Eu. An experimental study of MOX fuel of 14 × 14 PWR type and LEU fuel of both 15 × 15 and 17 × 17 type is also reported in this paper. The outcome of the experimental study support the conclusion that MOX fuel may be discriminated from LEU fuel by measuring the suggested isotopic ratio.

True to Life: Why Truth Matters

Why does truth matter, when politicians so easily side step it and intellectuals scorn it as irrelevant? Why be concerned over an abstract idea like truth when something that isn't true - for example, a report of Iraq's attempting to buy materials for nuclear weapons - gets the desired result, the invasion of Iraq? In this engaging and spirited book, Michael Lynch argues that truth does matter, in both our personal and political lives. Lynch explains that the growing cynicism over truth stems in large part from our confusion over what truth is. "We need to think our way past our confusion and shed our cynicism about the value of truth," he writes. "Otherwise, we will be unable to act with integrity, to live authentically, and to speak truth to power." Lynch diagnoses the sources of our cynicism and argues that many contemporary theories of truth cannot adequately account for its value. He explains why we should care about truth, arguing that truth and its pursuit are part of living a happy life, important in our personal relationships and for our political values.

True to life: why truth matters

Why does truth matter, when politicians so easily side step it and intellectuals scorn it as irrelevant? Why be concerned over an abstract idea like truth when something that isn't true - for example, a report of Iraq's attempting to buy materials for nuclear weapons - gets the desired result, the invasion of Iraq? In this engaging and spirited book, Michael Lynch argues that truth does matter, in both our personal and political lives. Lynch explains that the growing cynicism over truth stems in large part from our confusion over what truth is. We need to think our way past our confusion and shed our cynicism about the value of he writes. Otherwise, we will be unable to act with integrity, to live authentically, and to speak truth to power. Lynch diagnoses the sources of our cynicism and argues that many contemporary theories of truth cannot adequately account for its value. He explains why we should care about truth, arguing that truth and its pursuit are part of living a happy life, important in our personal relationships and for our political values.

Plutonium and “minor” actinides: safe sequestration

The actinides exhibit a number of unique chemical and nuclear properties. Of particular interest are the man-made actinides (Np, Pu, Cm and Am) that are produced in significant enough quantities that they are a source of energy in fission reactions, a source of fissile material for nuclear weapons and of environmental concern because of their long half-lives and radiotoxicity. During the past 50 yr, over 1400 mT of Pu and substantial quantities of the “minor” actinides, such as Np, Am and Cm, have been generated in nuclear reactors. There are two basic strategies for the disposition of these elements: (1) to “burn” or transmute the actinides using nuclear reactors or accelerators; (2) to “sequester” the actinides in chemically durable, radiation-resistant materials that are suitable for geologic disposal. There has been substantial interest in the use of isometric pyrochlore, A 2B 2O 7 (A=rare earths; B=Ti, Zr, Sn and Hf), for the immobilization of actinides, particularly plutonium. Systematic studies of rare-earth pyrochlores have led to the discovery that certain compositions (B=Zr, Hf) are stable to very high doses of α-decay event damage. The radiation stability of these compositions is closely related to the structural distortions that occur for specific pyrochlore compositions and the electronic structure of the B-site cation. This understanding provides the basis for designing materials for the safe, long-term immobilization and sequestration of actinides.

Presidential Candidates Speak Out on Science Policies

Presidential Candidates Speak Out on Science Policies

Response of winter birds to soil remediation along the Columbia River at the Hanford Site.

The Columbia River at the Hanford Site, located in south-central Washington State, U.S.A., is a regionally important refugium for overwintering birds. Some of the river shoreline has been designated by the U.S. Department of Energy for environmental clean-up following past production of materials for nuclear weapons. We evaluated the effects of soil remediation on winter birds at six inactive nuclear reactor areas. Remediation activities consisted of daily excavation and removal of approximately 1035 t of contaminated soil from previously herbicided and denuded areas located between 30 and 400 m and mostly in line-of-sight of the river shoreline. Remediation activities had no apparent effect on numbers of riverine or terrestrial birds using adjacent undisturbed shoreline and riparian habitat.

Toxicity of gadolinium to some aquatic microbes.

The toxicity of gadolinium to algae and bacteria was determined as part of an effort to develop a biological process to purify drums containing spent nuclear reactor heavy water moderator (D2O). This water was contaminated with high concentrations of gadolinium nitrate, a chemical used as a neutron poison during former nuclear reactor operations at the Savannah River Site (SRS) near Aiken, SC. Nuclear reactors were operated for approximately 30 years at the SRS to produce nuclear weapons materials for national defense. Throughout this period, a heavy water solution of gadolinium nitrate was utilized in a standby emergency shutdown system that could inject this chemical into the reactor moderator coolant water. The chemical was used for this purpose because the high neutron absorption cross sections of some gadolinium isotopes make gadolinium salts such as GdNO3 effective in controlling nuclear activity in aqueous systems (Gilbert et al. 1985; Rodenas et al. 1990). The use of this practice resulted in a large inventory of this degraded heavy water containing gadolinium nitrate. Microbiological and chemical studies were initiated to evaluate the potential use of bacteria and algae for water purification of the drums. Since metals are often toxic to microbes when present at concentrationsmore » substantially higher than natural environmental levels, it was hypothesized that Gd may be toxic to selected microorganisms (algae and bacteria) at the very high concentrations (average 80,000 mg/L, maximum 259,000 mg/L) present in most of the drums. Two principal components of the study included: (1) chemical and microbiological characterization of representative drums, and (2) an evaluation of the toxicity of gadolinium to selected species of algae. In addition to wastewater from nuclear production reactor operations, gadolinium waste is also generated from medical applications, especially MRI, and various electronic components including CD disks. Despite growing and widespread usage of this rare element, there is a paucity of information on the toxicity of gadolinium.« less

North Korea and the ‘Agreed Framework’

The Bush administration recently announced that it would continue engagement of North Korea, which has as its centrepiece the 1994 'Agreed Framework' (AF). Under the AF, North Korea is to receive two large electricity-producing nuclear reactors and some heavy fuel oil until the reactors are built. In return, North Korea must freeze and eventually dismantle a plutonium-producing reactor and related facilities, while making a complete declaration of how much nuclear weapons material it has. Critics of the AF question whether the new reactors, which will necessarily produce plutonium as a by-product, can be adequately and verifiably safeguarded. US President George W. Bush has emphasised that assurance of verification of the AF's provisions is vital for progress to be made. Recent findings suggest that the AF is technically verifiable, but only if North Korea meets strict conditions and the International Atomic Energy Agency received strong financial and political support in carrying out its tasks.

A Pragmatic Approach for Negotiating a Fissile Material Cut-Off Treaty

AbstractA Fissile Material Cut-Off Treaty banning the production of fissile material for nuclear weapons or other nuclear explosive devices is a natural next step on the multinational nuclear arms control agenda. Despite interest among key states and excessive stockpiles of fissile material, a formalized cut-off has yet to materialize. A new pragmatic approach for negotiating an FMCT patterned after the recent Mine Ban Treaty is presented as a potential model. Sweden, together with the other countries of the New Agenda Coalition, is identified as a possible candidate to take the lead and host an alternative FMCT negotiation process.

Law enforcement tools available at the Savannah River Site

A number of nuclear technologies developed and applied at the Savannah River Site in support of nuclear weapons material production and environmental remediation can be applied to problems in law enforcement. Techniques and equipment for high-sensitivity analyses of samples are available to identify and quantify trace elements and establish origins and histories of forensic evidence removed from crime scenes. While some of these capabilities are available at local crime laboratories, state-of-the-art equipment and breakthroughs in analytical techniques are continually being developed at DOE laboratories. Extensive experience with the handling of radioactive samples at the DOE labs minimizes the chances of cross-contamination of evidence received from law enforcement. In addition to high-sensitivity analyses, many of the field techniques developed for use in a nuclear facility can assist law enforcement personnel in detecting illicit materials and operations, in retrieving of pertinent evidence and in surveying crime scenes. Some of these tools include chemical sniffers, hand-held detectors, thermal imaging, etc. In addition, mobile laboratories can be deployed to a crime scene to provide field screening of potential evidence. A variety of portable sensors can be deployed on vehicle, aerial, surface or submersible platforms to assist in the location of pertinent evidence or illicit operations. Several specific nuclear technologies available to law enforcement and their potential uses are discussed.

The "age" of plutonium particles

Age determination of plutonium particles is a highly important task in view of the pending cut-off treaty for nuclear weapons materials. By collecting particles from the vicinity or inside the nuclear facilities and determining their ages, it is possible to monitor the observance of the cut-off agreement. In this study, the age determination of Pu particles was demonstrated by Secondary Ion Mass Spectrometry (SIMS). To determine the ionisation efficiency difference of Pu and U, standard Pu materials with known ages were analysed. Finally, the age determination of two real Pu samples was demonstrated.

Responding to economic change in remote, rural regions: federal installations in Idaho and Washington

The federal government's massive spending on nuclear weapons materials and research generated tens of thousands of jobs and pumped billions of dollars into a small number of regions during the 1940s and 1950s. This concentration of financial and physical resources caused the almost overnight formation of small urban centers in what formerly had been remote, rural areas, and made the economies of the regions that surround the two physically largest sites at Hanford and INEEL heavily dependent on nuclear-related government funding. With the end of the Cold War and global agreement to reduce nuclear arsenals, most of these facilities have been made obsolete. More than 10,000 jobs have been recently eliminated and thousands more were lost at private companies providing support services to these facilities and the displaced workers and their families. Further reductions will likely occur within the next 7–10 years. Our research looked at how local leaders in the still largely rural regions surrounding these two Department of Energy (DOE) sites responded to these economic changes, how have the communities reacted to the likelihood that these facilities would never again be a significant economic engine for the region, and what actions are being taken to reduce the impact of significant DOE cutbacks expected in the future? The results raise critical questions regarding the long-term economic future of the two regions and whether a more aggressive multi-faceted effort is required to stave off a long-term decline.

Ecological half-lives of 137Cs in fishes from the Savannah River Site.

Ecological half-lives (Te's) were estimated for 137Cs in largemouth bass, sunfishes, and bullheads from two reservoirs and three streams on the Savannah River Site, a nuclear weapons material production facility in South Carolina. Ecological half-life is the time required for a given contaminant concentration to decrease by 50% as a result of physical, chemical, and/or biological processes that remove it from an ecosystem or render it biologically unavailable. Te's were estimated from whole-fish 137Cs concentrations in samples collected during 1972-1996, following radionuclide releases that occurred primarily during the 1960's and early 1970's. Te's ranged from 3.2 to 16.7 y, and all were shorter than expected from the half-life for radioactive decay (Tp = 30.2 y) alone. Fish taxa from the same locations differed in mean 137Cs concentrations (highest in largemouth bass and lowest in sunfishes) but, in most cases, exhibited similar 137Cs Te's. Rates of 137Cs removal in fishes were strongly correlated with rates of 137Cs removal in water. The shortest Te's occurred in the upper portions of the streams. Te's in lower portions of the streams were longer, as were Te's in one of the reservoirs. Te's in the second reservoir, which had a much shorter water residence time, were nearly comparable to those in the upper portions of the streams until 1991. At that time, 137Cs concentrations in fishes began to increase following drainage and refilling of the reservoir, which apparently resuspended 137Cs buried in the sediments.

Scientific Openness and National Security

S cience is an international enterprise that embraces the importance of sharing information as one of its core values because the building of new knowledge onto old knowledge drives scientific advances. At the same time, the scientific community recognizes the importance of protecting U.S. national security interests from foreign espionage. How then are we to react to news reports of the possible theft of classified information from our nation's weapons laboratories and to the ensuing calls in Congress for increased restrictions on foreign visitors to national laboratories? Concern about possible new restrictions on foreign scientists has led the National Academies to issue a statement (available at [www.national-academies.org/topnews/][1]) and to initiate a fast-track study, with a workshop in August 1999 that will examine how best to ensure the dual objectives of international communication among scientists and protection of classified information. Inappropriate restrictions could harm U.S. interests by impeding the nation's scientific progress, weakening its role as a key player in the international scientific community, and endangering international cooperative activities in areas that bolster national security, such as nuclear safety, weapons proliferation, and environmental cleanup. An ability to maintain strong international ties has been critical to the strength of U.S. science. For example, one-quarter of the 1900 U.S. members of the National Academy of Sciences were born in another country. Of the students who received their Ph.D.'s in science at U.S. universities in 1997, 33 percent were foreign born. Our nation's well-being continues to depend on the many intellectual contributions of individuals who have come from other countries. Although the national laboratories of the Department of Energy (DOE) are engaged in classified military work, they also carry out a large amount of unclassified scientific and engineering research. Many of the foreign scientists who visit them are invited because they bring important new knowledge. A wide range of scientific expertise is essential for maintaining the intellectual vitality and quality of these laboratories and for sustaining their capacity to attract and retain promising young talent. Several studies by the National Academies have articulated the importance of increasing openness to promote the security systems necessary for controlling chemical, nuclear, and biological weapons. The 1997 National Academy of Sciences report Controlling Dangerous Pathogens emphasizes that appropriately structured U.S.-Russian scientific cooperation, featuring direct lab-to-lab contact, is needed to increase the certainty that work on biological weapons is not continued in Russia. Likewise, the 1999 National Research Council report Protecting Nuclear Weapons Material in Russia concludes that “continued DOE involvement in strengthening material protection, control, and accountability in Russia should be a high-priority national security imperative for the United States for at least a decade.” International scientific exchanges can also be a key to finding peaceful resolutions to very difficult issues. Last February, for example, scientists from Israel, the Palestinian Authority, Jordan, the United States, and Canada issued an important joint report on managing the dwindling water resources in the Middle East (available at [www.nap.edu/html/waterfuture][2]). Although regional water management is in large part a political issue, wise decisions will depend on application of the best scientific and engineering knowledge. In the post-Cold War era, the U.S. scientific and engineering communities have increasingly been called on to play diplomatic roles in establishing international partnerships. They have facilitated progress in such areas as counterproliferation, demilitarization, environmental cleanup, nuclear safety, and counterterrorism, while helping to divert foreign military manpower toward civilian goals. These interactions, which are clearly in the nation's best interests, require openness and free communication among scientists. Maintaining these interactions and simultaneously protecting our nation's classified information are critical for our long-term security. [1]: http://www.national-academies.org/topnews/ [2]: http://www.nap.edu/html/waterfuture