Diversion Of Nuclear Material Research Articles

Evolution of Legislation Regarding the Use of Nuclear Energy for Peaceful Purposes

The development and use of atomic energy represent one of the greatest achievements of the 20th century, opening new possibilities for global evolution. The United Nations (UN) has formulated the «Millennium Development Goals» and the «Sustainable Development Goals by 2030» to address comprehensive solutions to the social, economic, and environmental challenges facing the planet. In this context, nuclear energy offers unparalleled advantages, but it is essential to consider the risks and challenges associated with its future use and development. Nuclear law serves as a valuable tool for regulating the development of nuclear energy and overcoming these risks and challenges. All countries must strictly fulfill their international obligations, responsibly implement international legal instructions at the national level, and collectively support the international regime and legal framework organized around the United Nations. This, in turn, contributes to the achievement of the shared goal of «atoms for peace and development».
 The international legal framework on nuclear issues emerged alongside the development of nuclear energy worldwide. It evolves as social, economic, scientific, and technical challenges associated with this development are addressed, thereby contributing to the safe, secure, and sustainable development of peaceful nuclear energy use.
 The IAEA and the international community have established an almost universal regime of safeguards aimed at detecting and preventing the diversion of nuclear materials from peaceful nuclear activities to the production of nuclear weapons.
 Based on the results of the conducted research, it has been established that each country not only has the right to use nuclear energy for peaceful purposes but also bears the responsibility and obligation to prevent the proliferation of nuclear weapons and to support nuclear safety and security. All countries should conscientiously fulfill their obligations in accordance with the international legal framework on nuclear safety, fully implement relevant resolutions of the United Nations Security Council, strengthen and expand the existing international legal framework on nuclear safety, and provide institutional guarantees, adhering to universally defined guiding principles for managing international nuclear safety.

Proliferation aspects of partitioning and transmutation (P&T) fuel cycles

Abstract. Nuclear fuel is usually irradiated once but sometimes twice (MOX fuel). This procedure leaves a huge amount of spent fuel. Spent fuel is highly radioactive for a long time. Deep geological repositories are considered the best option for final disposal of this high-level radioactive waste. However, no such repository has been put into operation yet. Several countries consider partitioning and transmutation (P&T) a possible alternative. In P&T nuclear fuel cycles, the spent nuclear fuel is chopped into pieces and separated into different material streams such as plutonium, uranium and minor actinides. This process is called partitioning. From plutonium and minor actinides, new fuel elements are fabricated and used in nuclear reactors. If the overall physical conditions there are favorable, most prominently the presence of a fast neutron spectrum, at least a part of the minor actinides is fissioned and thus transmuted into other, hopefully easier-to-handle, nuclides. Especially when looking at the ingestion-based radiotoxicity index, reduction in minor actinides in nuclear waste is beneficial and might ease the requirements for a final repository. There are several drawbacks when looking at the concept of P&T: among others, several irradiation cycles are needed because the transmutation efficiency is so low. The technology for the processing of the spent fuel, the fuel fabrication and the irradiation is far from commercially available, and it is not clear whether this level can be met at all. This presentation focuses on the proliferation risk posed by possible P&T fuel cycles. The nexus between civil and military use of nuclear technology is widely known. If new fuel cycles are implemented, they should be more proliferation-resistant and not less. This would not be true for P&T fuel cycles: they require a closed nuclear fuel cycle with far more advanced reprocessing than today. Fissile material contained in spent nuclear fuel is not sent to final disposal but is separated into its components, which must be made available separately before they can be recombined into new fuel elements. Besides plutonium, this also includes other transuranic elements of small critical mass. The radiation barrier, an essential protection against unauthorized access to fissile material that could be used for nuclear weapons, is no longer present. The handling of those materials requires special facilities to cope with the immense amount of heat and radiation of the fuel containing high fractions of minor actinides. In those facilities, fissile material fitting for military purposes could be handled as well. Even if thorough safeguards are in place, detailed accountancy of all materials is not possible. The quantities needed to build a nuclear weapon are small compared to the quantities that need to be handled in a commercial-sized P&T fuel cycle. P&T technology is a civil application which clearly strengthens military capabilities. It would be hard to argue why it should only be available to a trustworthy partner (whoever that might be). The implementation of P&T fuel cycles would thus increase the risk of unauthorized diversion of nuclear material, technology and knowledge.

Antineutrino detection concepts for safeguarding spent nuclear fuel

Abstract. Spent nuclear fuel (SNF) from nuclear power generation requires long-term safeguards in interim storage and final disposal. Current safeguarding approaches for spent fuel storage facilities (SFSFs) propose a combination of material accountancy, containment and surveillance, and design information verification. Antineutrino emissions from the ongoing beta decay of fission fragments could provide complementary information on the potential diversion of nuclear material and misuse of the facility or assist in reverification scenarios as antineutrinos pass through any shielding, structure, or geology effectively unhindered. Antineutrino-based safeguards approaches have been discussed and have been under development for nuclear reactor sites for several years. In this relatively recent field of applied antineutrino monitoring, several approaches have been developed, ranging from scintillator-based technologies to large water Cherenkov detectors, each of which is suitable for different deployment scenarios. Utilising this principle for SNF is uniquely challenging, as the antineutrino flux of cooling fuel elements is several orders of magnitude lower than of an active core. In addition, the typical beta decays in SNF emit a softer antineutrinos energy spectrum, requiring large detectors sensitive to signals close to the inverse beta decay energy threshold. This study investigates a range of current technologies that have been proposed for reactor monitoring, along with a novel antineutrino detection concept using a liquid organic (LOr) time projection chamber (TPC). The LOr-TPC concept combines the scalability and high-resolution particle reconstruction of TPCs with the large quantity of target hydrogen atoms provided by organic compounds. The expected signal rate, sensitivity to inventory changes, and directional capabilities of all technologies are estimated and compared against each other for two simplified storage sites, namely one based on an interim storage facility and one based on a geological repository. For each simplified site, varying fuel ages, cask distributions, and detector deployment scenarios are investigated. This comparison will be used to determine the feasibility and potential of antineutrino monitoring as a complementary safeguards tool for SNF storage sites.

Improved Passive Gamma Emission Tomography image quality in the central region of spent nuclear fuel

Reliable non-destructive methods for verifying spent nuclear fuel are essential to draw credible nuclear safeguards conclusions from spent fuel. In Finland, spent fuel items are verified prior to the soon starting disposal in a geological repository with Passive Gamma Emission Tomography (PGET), a uniquely accurate method capable of rod-level detection of missing active material. The PGET device consists of two highly collimated detector banks, collecting gamma emission data from a 360° rotation around a fuel assembly. 2D cross-sectional activity and attenuation images are simultaneously computed. We present methods for improving reconstructed image quality in the central parts of the fuel. The results are based on data collected from 2017 to 2021 at the Finnish nuclear power plants with 10 fuel assembly types of varying characteristics, for example burnups from 5.7 to 55 GWd/tU and cooling times from 1.9 to 37 years. Data is acquired in different gamma energy windows, capturing the peaks of Cs-137 (at 662 keV) and Eu-154 (at 1274 keV), abundant isotopes in long-cooled spent nuclear fuel. Data from these gamma energy windows at well-chosen angles are used for higher-quality images, resulting in more accurate detection of empty rod positions. The method is shown to detect partial diversion of nuclear material also in the axial direction, demonstrated with a novel measurement series scanning over the edge of partial-length rods.

Контрольная деятельность МАГАТЭ

The article explores the verification activity by the International Atomic Energy Agency (IAEA). This activity involves three key aspects: the legal framework, goals, and measures and verification procedures to achieve these goals. The author analyzes legal and technical aspects of the IAEA verification activity, including the notions of diversion of nuclear material and a state’s noncompliance with its commitments related to corresponding safeguards agreements. The analysis is based on the systematic approach that takes into account the evolution of the safeguards system. The author proposes an original approach to reduce the risks of politicization of decisions on noncompliance of states with safeguards agreements by specifying the main notions related to the system of safeguards.

Preliminary proliferation study of the molten salt fast reactor

The molten salt reactor designs, where fissile and fertile materials are dissolved in molten salts, under consideration in the framework of the Generation IV International Forum, present some unusual characteristics in terms of design, operation, safety and also proliferation resistance issues. This paper has the main objective of presenting some proliferation challenges for the reference version of the Molten Salt Fast Reactor (MSFR), a large power reactor based on the thorium fuel cycle. Preliminary studies of proliferation resistance are presented here, dedicated to the threat of nuclear material diversion in the MSFR, considering both the reactor system itself and the processing units located onsite.

Development of PYMUS+ Code for Quantitative Evaluation of Nuclear Material Accounting (NMA) System

The Nuclear Material Accounting (NMA) system is one of the main safeguards measures to detect the existence of nuclear material diversion. It has become more important for large reprocessing facilities to apply Near Real Time Accountancy (NRTA) system based on NMA and statistical techniques to meet quantitative and timeliness goals. It is also important to quantitatively evaluate the performance of NMA system including NRTA from the standpoints of Safeguards and Security by Design (SSBD) prior to construction of nuclear-material-handling facilities. Such evaluation improves safeguards effectiveness and efficiency. Modeling and Simulation (M&S) work is a good way to evaluate performance for various NMA systems and to determine the optimal one among different options. For these purposes, in the present study, the PYroprocessing Material flow and MUF Uncertainty Simulation+ (PYMUS+) code, which uses evaluation algorithms to calculate many safeguards factors such as MUF uncertainty, detection probability, and others, was developed. According to a previous report, the PYMUS code, the predecessor of PYMUS+, can calculate MUF uncertainties only for a fixed model having 10 tHM/year, whereas the PYMUS+ code can additionally calculate detection probabilities according to diverse nuclear diversion scenarios as well as MUF uncertainties. The most important feature of the PYMUS+ code is its capability to evaluate many process and NMA system model options that a user wants to evaluate. Furthermore, a user can make a static process model having simplicity and a matching NMA model based on the PYMUS+ code regardless of facility throughput and is not even required to have professional programming knowledge. In the present work, some intercomparative studies were conducted to verify the M&S techniques applied in this code. It is expected that this code will be a useful tool for evaluation of NRTA system of pyroprocessing and other reprocessing facilities.

Investigations on Detecting Potential Nuclear Material Diversion from a Pyroprocessing Facility

Under normal operating conditions, a pyroprocessing facility removes highly radioactive and nonradioactive fission product waste from used nuclear reactor fuel to recycle the remaining uranium (U), plutonium (Pu), and other actinides contained in it. The products from this facility are separate ingots of U and mixed transuranic elements (TRUs)–uranium (TRU-U). Uranium in both ingots will be depleted U with 235U enrichment less than 1%. The TRU-U ingot will contain neptunium, Pu, americium (Am), and curium (Cm) mixed with U with an approximate TRU:U ratio of 1:1. Four scenarios of nuclear material diversion by potential misuse of the pyroprocessing facility operations are analyzed and compared with the scenario of normal operating condition when the electrowinning process or the TRU-U ingot manufacturing process is misused. These diversion scenario analyses are carried out to understand the proliferation potential and to recommend safeguards measures. The four scenarios of nuclear material diversion analyzed are (1) 50 g Pu, (2) 100 g Pu, (3) 200 g Pu, and (4) all Pu, i.e., 452 g in the 1-kg TRU-U ingot. Plutonium cannot be diverted by itself because other TRUs (Am and Cm) will be simultaneously extracted with Pu. This is because the reduction potentials of those actinides are not distinguishably different from that of Pu on a liquid cadmium cathode of the electrowinning step of the pyroprocess. Hence, in addition to Pu, simultaneous diversion of respective amounts of Am and Cm for the four diversion scenarios are considered. The diversion scenario analysis also considered the concealment of Pu and Cm removal from the TRU-U ingot by adding an equivalent amount of 252Cf to replenish the neutron source emissions. These five scenarios (four nuclear material diversion scenarios and one normal operation scenario) are modeled and simulated using the Monte Carlo N-Particle (MCNP6) radiation transport computer code by incorporating the model of a NaI gamma radiation detection system. The results show that the presence and absence of Pu in the TRU-U ingot can be confirmed by the NaI gamma radiation detection system. However, identifying the presence of U in the TRU-U ingot is difficult using the NaI gamma radiation detection system due to interference from TRU gamma radiation. To identify the U presence in the TRU-U ingot, an application of nuclear magnetic resonance (NMR) is studied. The NMR technology employs a numerical calculation approach based on density functional theory (DFT) simulation. The DFT calculation results show that the detection of U in a pyroprocess is feasible by NMR technology. In addition, these four nuclear material diversion scenarios are analyzed through MCNP6 simulations by incorporating the model of a coincidence neutron detection system. To conceal the nuclear material diversion, the simulations are performed by replacing the diverted Pu and Cm by an appropriate mass of 252Cf neutron source that is equivalent to the neutron source strengths of the diverted mass. Simulation results show that this concealment (misuse) results in a deceived Pu mass estimate in the TRU-U ingot if the Pu-to-244Cm–ratio method (proposed method in the literature) is used.

Methods for Determining the Working Electrode Interfacial Area for Electroanalytical Measurements of Metal Ions in Molten LiCl-KCl

Voltammetry is a promising approach to determining the concentration of actinides and rare earths in molten chloride salts for real time or near real time monitoring of nuclear fuel electrorefining. In this process, actinides and rare earths accumulate in eutectic LiCl-KCl from reaction of UCl3 with spent nuclear fuel. Monitoring the salt composition is key in order to maintain optimal process conditions, to determine when to treat or discard salt, and to safeguard the process against nuclear material diversion. Voltammetry methods such as cyclic voltammetry (CV), chronopotentiometry (CP), chronoamperometry (CA), normal pulse voltammetry (NPV), and square wave voltammetry (SWV) have been extensively reported in the literature for application to molten LiCl-KCl typically containing one rare earth or actinide chloride. Our studies have expanded the salt matrices to include quaternary salts with two electrochemically active metal chlorides. We believe this to be the first step in determining if these basic electrochemical analysis methods can be applied to salts containing many components with similar standard reduction potentials. In the simpler ternary salt systems, classic diffusion limited rate equations such as those derived by Randles-Sevcik and Berzins-Delahay have been applied to correlate CV peak height to concentration. Application of these equations requires knowledge of both the diffusion coefficient of the salt compound in the LiCl-KCl and the interfacial area between the working electrode and salt. In our experimental investigations, we have determined that both of these quantities can be difficult to establish a priori. Diffusion coefficients for metal chlorides in molten LiCl-KCl appear to vary with concentration. And the high temperature electrochemical cells located in insulated furnaces make it challenging to precisely determine the electrode-salt interfacial area. In this paper, we focus on empirical evaluation of methods for determining this area—ranging from the simplest approach of dipping a cold electrode into the molten salt to measure the film height to more elaborate approaches such as using a vertical electrode actuator, coating the electrodes with glass, and integrating a pre-peak which may represent formation of a monolayer of metal on the electrode. Salt mixtures investigated include LiCl-KCl-UCl3, LiCl-KCl-UCl3-MgCl2, LiCl-KCl-ThCl4-LaCl3, LiCl-KCl-LaCl3-GdCl3, and LiCl-KCl-LaCl3-MgCl2. It will be shown that with accurate determination of the electrode-salt interfacial area that concentration correlations can be developed with error as low as 2-3%. Both using differential insertion depth with the vertical electrode translator and using glass-coated working electrodes are promising approaches—the latter of which is believed to be more easily implemented in a production operation scenario.

The impact of metrology study sample size on uncertainty in IAEA safeguards calculations

Quantitative conclusions by the International Atomic Energy Agency (IAEA) regarding States' nuclear material inventories and flows are provided in the form of material balance evaluations (MBEs). MBEs use facility estimates of the material unaccounted for together with verification data to monitor for possible nuclear material diversion. Verification data consist of paired measurements (usually operators' declarations and inspectors' verification results) that are analysed one-item-at-a-time to detect significant differences. Also, to check for patterns, an overall difference of the operator-inspector values using a “D (difference) statistic” is used. The estimated DP and false alarm probability (FAP) depend on the assumed measurement error model and its random and systematic error variances, which are estimated using data from previous inspections (which are used for metrology studies to characterize measurement error variance components). Therefore, the sample sizes in both the previous and current inspections will impact the estimated DP and FAP, as is illustrated by simulated numerical examples. The examples include application of a new expression for the variance of the D statistic assuming the measurement error model is multiplicative and new application of both random and systematic error variances in one-item-at-a-time testing.

A Novel Framework for Safeguarding Naval Nuclear Material

ABSTRACTThe present international standard allows non-nuclear weapon states (NNWS) to forego safeguards when nuclear material is used in a “non-proscribed military activity,” though no criteria have been established to determine when NNWS can remove naval nuclear material from safeguards. Though at present, only nuclear-armed states possess nuclear submarines, the global nuclear naval landscape may soon change with the advancement of Brazil's fledgling program and the possible precedent it would set for other NNWS. A framework is needed to shore up nuclear security and prevent nuclear material diversion from the nuclear naval sector. Proposed and existing nonproliferation frameworks, including a Fissile Material Cut-off Treaty and commitments through the nuclear security summits, are insufficient to close this loophole. A Naval Use Safeguards Agreement (NUSA), modeled after the Additional Protocol of the International Atomic Energy Agency, would provide a framework to remove the opacity surrounding nuclear material in the naval sector. Designed for NNWS and encouraged as confidence-building measures for nuclear weapon states, NUSA would explicitly outline those stages in the naval nuclear fuel cycle where safeguards are to be applied and in what context. This viewpoint also further provides direction for targeted research and development in technical naval nuclear safeguards solutions.

Determination of the plutonium content in a spent fuel assembly by passive and active interrogation using a differential die-away instrument

In this paper, we present a novel approach to estimating the total plutonium content in a spent fuel assembly (SFA) that is based on combining information from a passive measurement of the total neutron count rate (PN) of the assayed SFA and a measure of its multiplication. While PN can be measured essentially with any non-destructive assay (NDA) technique capable of neutron detection, the measure of multiplication is, in our approach, determined by means of active interrogation using an instrument based on the Differential Die-Away technique (DDA). The DDA is a NDA technique developed within the U.S. Department of Energy's Next Generation Safeguards Initiative (NGSI) project focused on the utilization of NDA techniques to determine the elemental plutonium content in commercial nuclear SFA's [1]. This approach was adopted since DDA also allows determination of other SFA characteristics, such as burnup, initial enrichment, and cooling time, and also allows for detection of certain types of diversion of nuclear material. The quantification of total plutonium is obtained using an analytical correlation function in terms of the observed PN and active multiplication. Although somewhat similar approaches relating Pu content with PN have been adopted in the past, we demonstrate by extensive simulation of the fuel irradiation and NDA process that our analytical method is independent of explicit knowledge of the initial enrichment, burnup, and an absolute value of the SFA's reactivity (i.e. multiplication factor). We show that when tested with MCNPX™ simulations comprising the 64 SFA NGSI Spent Fuel Library-1 we were able to determine elemental plutonium content, using just a few calibration parameters, with an average variation in the prediction of around 1–2% across the wide dynamic range of irradiation history parameters used, namely initial enrichment (IE=2–5%), burnup (BU=15–60GWd/tU) and cooling time (CT=1–80y). In this paper we describe the basic approach and the success obtained against synthetic data. We recognize that our synthetic data may not fully capture the rich behavior of actual irradiated fuel and the uncertainties of the practical measurements. However, this design study is based on a rather complete nuclide inventory and the correlations for Pu seem robust to variation of input. Thus it is concluded that the proposed method is sufficiently promising that further experimentally based work is desirable.

Chapter Three: Can Iran's Capability Be Kept Non-Weaponised?

This paper explains how Iran developed its nuclear programme to the point where it threatens to achieve a weapons capability within a short time frame, and analyses Western policy responses aimed at forestalling that capability. Key questions are addressed: will the world have to accept an Iranian uranium enrichment programme, and does having a weapons capability mean having the Bomb? For nearly two decades, Western strategy on the Iran nuclear issue emphasised denial of supply. Since 2002, there has also been a demand-side dimension to the strategy, aimed at changing Iran's cost–benefit calculations through inducements and pressure. But the failure of these policies to prevent Iran from coming close to achieving a nuclear-weapons capability has promoted suggestions for fallback strategies that would grant legitimacy to uranium enrichment in Iran in exchange for intrusive inspections and constraints on the programme. The paper assesses these ‘second-best’ options in terms of their feasibility and their impact on the proliferation risks of diversion of nuclear material and knowledge, clandestine development and NPT break-out, and the risk of stimulating a proliferation cascade in the Middle East and beyond. It concludes that the risks are still best minimised by reinforcing the binary choice presented to Iran of cooperation or isolation, and strengthening denial of supply.

Chapter Two: Western Strategy So Far

This paper explains how Iran developed its nuclear programme to the point where it threatens to achieve a weapons capability within a short time frame, and analyses Western policy responses aimed at forestalling that capability. Key questions are addressed: will the world have to accept an Iranian uranium enrichment programme, and does having a weapons capability mean having the Bomb? For nearly two decades, Western strategy on the Iran nuclear issue emphasised denial of supply. Since 2002, there has also been a demand-side dimension to the strategy, aimed at changing Iran's cost–benefit calculations through inducements and pressure. But the failure of these policies to prevent Iran from coming close to achieving a nuclear-weapons capability has promoted suggestions for fallback strategies that would grant legitimacy to uranium enrichment in Iran in exchange for intrusive inspections and constraints on the programme. The paper assesses these ‘second-best’ options in terms of their feasibility and their impact on the proliferation risks of diversion of nuclear material and knowledge, clandestine development and NPT break-out, and the risk of stimulating a proliferation cascade in the Middle East and beyond. It concludes that the risks are still best minimised by reinforcing the binary choice presented to Iran of cooperation or isolation, and strengthening denial of supply.

Conclusion

This paper explains how Iran developed its nuclear programme to the point where it threatens to achieve a weapons capability within a short time frame, and analyses Western policy responses aimed at forestalling that capability. Key questions are addressed: will the world have to accept an Iranian uranium enrichment programme, and does having a weapons capability mean having the Bomb? For nearly two decades, Western strategy on the Iran nuclear issue emphasised denial of supply. Since 2002, there has also been a demand-side dimension to the strategy, aimed at changing Iran's cost–benefit calculations through inducements and pressure. But the failure of these policies to prevent Iran from coming close to achieving a nuclear-weapons capability has promoted suggestions for fallback strategies that would grant legitimacy to uranium enrichment in Iran in exchange for intrusive inspections and constraints on the programme. The paper assesses these ‘second-best’ options in terms of their feasibility and their impact on the proliferation risks of diversion of nuclear material and knowledge, clandestine development and NPT break-out, and the risk of stimulating a proliferation cascade in the Middle East and beyond. It concludes that the risks are still best minimised by reinforcing the binary choice presented to Iran of cooperation or isolation, and strengthening denial of supply.

Chapter One: Framing the Problem: Iran's Pursuit of Fissile Material

This paper explains how Iran developed its nuclear programme to the point where it threatens to achieve a weapons capability within a short time frame, and analyses Western policy responses aimed at forestalling that capability. Key questions are addressed: will the world have to accept an Iranian uranium enrichment programme, and does having a weapons capability mean having the Bomb? For nearly two decades, Western strategy on the Iran nuclear issue emphasised denial of supply. Since 2002, there has also been a demand-side dimension to the strategy, aimed at changing Iran's cost–benefit calculations through inducements and pressure. But the failure of these policies to prevent Iran from coming close to achieving a nuclear-weapons capability has promoted suggestions for fallback strategies that would grant legitimacy to uranium enrichment in Iran in exchange for intrusive inspections and constraints on the programme. The paper assesses these ‘second-best’ options in terms of their feasibility and their impact on the proliferation risks of diversion of nuclear material and knowledge, clandestine development and NPT break-out, and the risk of stimulating a proliferation cascade in the Middle East and beyond. It concludes that the risks are still best minimised by reinforcing the binary choice presented to Iran of cooperation or isolation, and strengthening denial of supply.

Notes

This paper explains how Iran developed its nuclear programme to the point where it threatens to achieve a weapons capability within a short time frame, and analyses Western policy responses aimed at forestalling that capability. Key questions are addressed: will the world have to accept an Iranian uranium enrichment programme, and does having a weapons capability mean having the Bomb? For nearly two decades, Western strategy on the Iran nuclear issue emphasised denial of supply. Since 2002, there has also been a demand-side dimension to the strategy, aimed at changing Iran's cost–benefit calculations through inducements and pressure. But the failure of these policies to prevent Iran from coming close to achieving a nuclear-weapons capability has promoted suggestions for fallback strategies that would grant legitimacy to uranium enrichment in Iran in exchange for intrusive inspections and constraints on the programme. The paper assesses these ‘second-best’ options in terms of their feasibility and their impact on the proliferation risks of diversion of nuclear material and knowledge, clandestine development and NPT break-out, and the risk of stimulating a proliferation cascade in the Middle East and beyond. It concludes that the risks are still best minimised by reinforcing the binary choice presented to Iran of cooperation or isolation, and strengthening denial of supply.

FIGARO: detecting nuclear materials using high-energy gamma-rays

The potential diversion of nuclear materials is a major international concern. Fissile (e.g., U, Pu) and other nuclear materials (e.g., D, Be) can be detected using 6–7MeV gamma-rays produced in the 19F(p,αγ) 16O reaction. These gamma-rays can induce neutron emission via photoneutron and photofission processes in nuclear materials. However, they are not energetic enough to generate significant numbers of neutrons from common benign materials. Neutrons are counted using an array of BF3 tubes in a polyethylene moderator. A strong increase in neutron count rates is seen when irradiating depleted uranium, Be, D2O, and 6Li, with little or no increase for other materials (e.g., H2O, SS, Cu, Al, C, 7Li). Experiments using both photon and neutron shielding show that the technique is resistant to countermeasures. We have reduced the neutron background from proton beam reactions (thus increasing the system's sensitivity) and have tested a high-current gas cell which should be capable of operating at proton beam currents of up to 100μA.

CO 2 and the world energy system: the role of nuclear power

The greenhouse effect, and other transnational and global environment, health and safety issues, require energy system planning on an international scale. Consideration of equity between nations and regions, particularly between the industrialized and developing countries, is an essential ingredient. For the immediate future, the next several decades at least, fossil fuels will remain the predominant energy sources. More efficient use of energy seems to be the only feasible strategy for the near to mid-term to provide growing energy services for the world economy while moderating the increasing demand for fossil fuels. In the longer term, nonfossil sources are essential for a sustainable world energy system, and nuclear power can play an important, if not dominant, role. The challenge is to design and implement a safe and economic nuclear power world enterprise which is socially acceptable and is complimentary to other nonfossil sources. The elements of such an enterprise seem clear and include: much safer reactors, preferably passively safe, which can be deployed at various scales; development of economic resource extension technologies; effective and permanent waste management strategies; and strengthened safeguards against diversion of nuclear materials to weapons. All of these elements can best be developed as cooperative international efforts. In the process, institutional improvements are equally as important as technological improvements; the two must proceed hand-in-hand.

Safeguards controversy, continued

Does the International Atomic Energy Agency's inspection system really prevent the theft or diversion of nuclear material? A former agency spokesman says Richard Bolt's criticisms were unjustified—and Bolt responds.