Conference Agenda

The network of subsea data cables (SDC) transmits the majority of international data. After thirty years of fiber-optic SDC installation across the oceans, almost all coastal and island countries gained access to the only global fixed infrastructure network. While their essential role in intercontinental communication remains, the fibers within the cables are increasingly used as sensors that have the potential to monitor large parts of the water column. Specifically, Distributed Acoustic Sensing (DAS) technology enables existing fiber-optic cables to function as distributed hydrophones, detecting vibrations and movements along the seafloor. While primarily developed for monitoring cable integrity and environmental conditions, this technology also creates potential dual-use applications, allowing cables to detect vessels and monitor underwater activities – including military ones. This secondary capability raises important considerations for infrastructure resilience, as it provides early warning of potential damage while simultaneously introducing new security dimensions to subsea cable systems.

In this study, we seek to understand the key factors influencing the placement of SDCs. While earlier research proposed various explanations for the development of internet infrastructure, it often lacked statistical validation. Our analysis identifies the national-level conditions that either encouraged or discouraged decision-makers from constructing backbone accesses through subsea cable projects. Using regression analysis on a global dataset of country-year observations (n = 4916), we found that socio-economic factors (population size and economic performance), political conditions (state fragility and conflict), and geographic characteristics (seismic risk and proximity to neighboring territories) all had significant impacts on the number of existing and planned cable landings. These findings reveal that the global distribution this maritime infrastructure is skewed towards wealthy, populated, and more stable states, which puts them also in an advantaged position in sensing data access. This work can serve as a foundation for further research leveraging quantitative statistics to unveil hidden structures in the construction of material internet infrastructures and initiate a debate on the equitable regulation and distribution of sensing data.

The interest in the international community in Small Modular Reactors (SMRs) is increasing steadily. Research is being conducted by startups and well-known companies in the field of reactor technology and development into the feasibility of SMRs and advanced nuclear fuels. The compact modules offer enhanced flexibility and accessibility for both new users and applications, rendering them particularly appealing to countries that have not yet adopted nuclear power generation or sites not suitable for traditional nuclear power plants. Simultaneously, novel challenges are emerging for the verification and safeguarding processes. New challenges to the safeguarding of SMRs originate from remote and isolated locations, novel fuels such as High-Assay Low-Enriched Uranium (HALEU) or novel reactor concepts. They also arise from sites with multiple reactor units, which result in a higher inspection workload. The objective of this project is to develop technologies based on particle physics that can be used to complement existing safeguard technologies, thus minimising the workload of safeguard inspectors. This involves the reconciliation of the requirements of facility operators and policymakers with the technical possibilities.

One potential solution to support inspectors is the deployment of antineutrino detectors in outdoor locations, outside of the immediate vicinity of the reactor facility. Antineutrinos are created in fission processes in large quantities during the operation of a nuclear reactor and have the capacity to leave not only the reactor module but also the surrounding containment structure. The capability for external detection enables the detector to function as a safeguard monitoring device for a broad range of SMR types and configurations, including subsequent integration. In this study, we analyse how the energy spectrum and other interesting parameters of detected antineutrinos can provide information on the isotopic content of the nuclear fuel. In addition, reactor simulations for a representative SMR site with multiple units are conducted to investigate the changes in the composition of the nuclear fuel over a fuel cycle and beyond. We also examine how these changes affect the antineutrino spectrum. It will be further demonstrated that antineutrino detectors offer the potential for effectively monitoring the operational status of multi-unit sites. A central aspect of this analysis is the impact of shutting down individual units, a possible scenario for clandestine plutonium extraction, on the resulting antineutrino spectrum. This is also of interest in scenarios involving the diversion of nuclear material from a single module. The detection of reactor antineutrinos thus permits the independent monitoring of reactors, independent of the facility operator, and the verification of information provided by the operator.

As other countries, China relies on the expansion of nuclear energy to reach less dependence on coal, China relies on the expansion of nuclear energy, including fast breeder reactors. These reactors can operate in a mode in which consumption of fissile material is less than the production. The Chinese sodium-cooled reactor CFR-600 is planned with an electrical capacity of 600MW. However, it is capable of producing a significant amount of weapons-grade plutonium in the blankets as well. The first CFR-600 may already be operational, the second is planned for 2026. There are concerns that China may use breeder reactors for military purposes, as it vastly expands its nuclear weapons program. How much and how fast the Chinese warhead inventory can grow depends on the additional fissile material stockpiles it can produce. In light of this development and the current global political circumstances, we present results on the CFR-600 plutonium production based on burnup simulations using OpenMC.

The insights derived from the simulation are utilized to facilitate a more profound examination of the broader political implications associated with China's escalating nuclear armament. Although China reportedly ceased the production of weapons-grade plutonium in the early 1990s, it stopped voluntarily reporting its plutonium stockpiles to the IAEA in 2017. The results of this simulation carry significant political ramifications, particularly concering the interpretation of China’s opague and expanding nuclear posture. This concern is amplified by U.S. intelligence reports revealing the construction of hundreds of new missile silos in China’s north-central desert, potentially capable of housing large numbers of intercontinental ballistic missiles (ICBMs), which are the most important delivery systems for nuclear weapons. If the CFR-600 reactors are indeed being used for military purposes, this development, along with the ongoing nuclear modernization and expansion of military infrastructure, would provide further indications of a more assertive and ambitious chinese nuclear posture, in contrast to its historically passive one.

Since the 1950s, numerous applications for muography have been identified, ranging from the study of ancient and modern structures to volcanology and various fields of industry. In recent years, muons have also been investigated as a potential method for nuclear verification.

As part of the natural cosmic radiation, high-energy muons can penetrate metres of dense material. While passing through matters, muons lose their energy, undergo multiple Coulomb scattering and can be absorbed. The nature of these interactions allows the use of radiographic density methods. Recent research in the field of international nuclear safeguards has shown that muography is potentially suitable for imaging both nuclear materials in shielded containers and hidden structures in underground facilities. In 2024, a simulation study was carried out to investigate whether muon radiography could identify unknown features such as tunnels that had not been declared prior to the construction of a geological repository for spent fuel [1]. A year earlier a field trial was carried out to investigate the ability of muon tomography to re-verify spent fuel loaded into a shielded cask [2]. Although the research projects are still ongoing, it has already been shown that muography has great potential as an imaging technique for imaging hidden underground structures and detecting shielded nuclear materials. While both projects are aimed at verifying the peaceful use of nuclear materials and facilities in the context of international safeguards, muography also holds promise for verifying nuclear disarmament. In this context, a recent Canadian research project investigated the ability of muon tomography to verify the dismantling of a nuclear weapon while protecting sensitive information about the exact structure of the weapon [3].

In summary, the research projects show that, in addition to the possibilities offered by muography, there are still certain limitations in the measurement of the target material that need to be addressed. Therefore, muography should be further investigated as a potential technique to support nuclear verification activities in the field of nuclear safeguards and the disarmament verification regime through further research to improve the detector system and the analysis algorithms. It is clear, however, that such a technology used in compliance with disarmament treaties will have to meet additional requirements compared to nuclear safeguards, such as the need to protect sensitive information and meet safety obligations.

[1] L. F. Thompson et al., "The Use of Muon Tomography in Safeguarding Nuclear Geological Disposal Facilities”, Journal of Advanced Instrumentation in Science, vol. 2022, May 2022.

[2] G. Bonomi et al., "Muon Tomography for Reverification of Spent Fuel Casks (the MUTOMCA Project)”, Journal of Advanced Instrumentation in Science, vol. 2024, no. 1, Mar. 2024.

[3] D. Pérez-Loureiro et al., "Canadian Technology Demonstration of the Passive Techniques: Muon, Neutron, and Gamma-Rays for Nuclear Disarmament Verification”, Proceedings of the INMM & ESARDA Joint Annual Meeting, 2021.

To ensure the non-proliferation of nuclear weapons, member states to the Treaty on the Non-Proliferation of Nuclear Weapons that are not listed as nuclear weapon states agreed to the International Atomic Energy Agency (IAEA) applying safeguards measures on fissile material and nuclear facilities. This is also relevant for nuclear waste management during interim storage and deep-geological disposal. Here, safeguards measures such as seals, closed-circuit television (CCTV) cameras, radiation detectors or laser scans are applied to containers with spent nuclear fuel and other nuclear waste to ensure the containment and surveillance of this material. Similar measures are applied to the facilities themselves to verify the design information of the built structures. These monitoring systems over the past have grown in complexity, nowadays produce large amounts of data and have become more and more interconnected and automated. At the same time, digital twin concepts increasingly gain popularity in industry contexts while enabling technologies such as high-performance computing and machine learning have become more easily available.

With this poster, we will present a project that aims to explore the possibilities and limitations of digital twins for safeguards in nuclear waste management. We will sketch our approach to modeling a safeguards inspection and monitoring system and the data traces, inspection data and operator declarations relevant to this. We will discuss the PostgreSQL database implementation of this model capable of tracking the system state over time and the Python API that can be used to connect different applications to the database. This includes a Python-powered Dash app as Graphical User Interface (GUI), visualizing the system state from an operator and inspectorate perspective, as well as software to simulate different physical aspects, such as neutron and gamma radiation as well as light detection and ranging (LiDAR). In the end, we will outline the planned extension of this prototype software to a larger digital twin framework, where real measurement data can be processed and analyzed alongside the simulated data, e.g. for experimental design optimization and anomaly detection. Through that, this work aims at supporting and facilitating remote monitoring, the development of new safeguards techniques, as well as education and training.

The role of weapon systems with autonomous functions (AWS) shapes warfare in Ukraine and increasingly influences will European defence planning. However, norms and safeguards for human control (HC) have not yet been established. International organisations, as emphasized in the UN GGE guidelines, IEEE Standards Association, and REAIM Blueprint for Action in 2024, as well as defence firms, anticipate HC as central requirement (Riebe et al., 2024). Enhancing human control is a universal challenge in the field of human-computer interaction (HCI), especially in security-critical areas with increasing levels of automation, e.g., in medicine. Thus, this poster aims to present and invite the audience to discuss the design of our project "Designing for Agency", which aims to bridge the gap between HCI and arms control research and provide recommendations for safeguards through iterative interdisciplinary knowledge transfer and expert workshops. The project aims to research approaches, and best practices to enhance HC from the perspective of human agency in HCI while considering the domain context of AWS, arms control research and practice.

Additive Manufacturing (AM), a technology that allows for the generation of objects layer by layer following a 3D digital design, has not only captivated hobbyists' fascination over the last decades but has become increasingly researched for and integrated into manufacturing processes. Coined 3D-printing, AM allows for creating complex geometries and on-demand manufacturing of items previously impossible to make with subtractive manufacturing technologies or demanding lengthy and expensive lead times. Also, the military technology sector has caught up to the technology, aiming to translate its advantages into increased military effectiveness. Next to industrial actors developing applications aimed at improving the weight-to-performance ratios of military goods and creating solutions to optimise maintenance through in-situ and on-demand printing, among others, more actors have also advanced military technology with AM; those range from individuals, associations, to armed groups and right-wing terrorists. Examples include the extensive use of 3D-printing in Ukraine within the scope of their drone warfare and the online proliferation of design files to “print” firearms. I want to present a poster at the SPS25 that illustrates these technological developments, as detailed in a forthcoming PRIF report of mine. Showcasing and analysing the technical realities and limits is a first step in understanding AM´s potential risks and impact on political violence. The report details both applications of industrial and various other actors and how the technology is used by armed forces and applied in conflict settings. While AM is a wide field, this presentation would focus on military technology, particularly approaching it from an angle more extensive than a sole focus on weaponry. With the presentation of my findings at the SPS25, I would like to start a dialogue with the arms control community about control of this technology, which stands as an example for democratised and diffused emerging technology. As such, the discussions around what if an emerging technology becomes accessible can centre around the reality and consequences of de facto realities.

Metaphors are not simply rhetorical embellishments. Instead, they serve as cognitive structures that influence the perception, discourse, and actions about political realities. In international dialogues around artificial intelligence (AI), the prevalent metaphor of a ‘AI (arms) race’ has surfaced as a significant framing mechanism. This paradigm, grounded on Cold War narratives like the space race and arms race, portrays AI development as a critical, zero-sum contest for global supremacy (e.g., Kania 2018; Roff 2019; Diehl and Lambach 2022). Influential figures, like Elon Musk's dire cautions and Vladimir Putin's claim that AI dominance will dictate world authority, have solidified this perspective (Hull et al. 2022). The race metaphor has indeed stimulated investment and innovation; yet, it fosters urgency, competition, and confidentiality, so compromising long-term partnership and ethical supervision. Academics have increasingly warned that this framing may lead to a self-fulfilling prophecy, as belief in racial dynamics encourages competitive behaviour even without real conflict (Cave and ÓhÉigeartaigh 2018; Houser and Raymond 2020; Ulnicane 2023).

This contribution advocates for a redefinition of our understanding of AI progress. We commence by providing a theoretical framework for comprehending the function of metaphor in International Relations (IR), delineating their cognitive roles, strategic applications, and political ramifications, in conjunction with an exposition of our analytical methodology. We subsequently examine the progression of the ‘race’ metaphor, transitioning from the classical sports race to the arms race, and ultimately to the modern AI arms race, highlighting both consistencies and changes in metaphorical focus. This genealogy elucidates the competitive rationale underlying contemporary discourse and its constraints in directing ethical and collaborative AI governance.

We propose the metaphor of a ‘AI treasure hunt’ as an alternative. Unlike the race's focus on speed, scarcity, and individual triumph, the treasure hunt metaphor highlights curiosity, exploration, communal knowledge, and collective advantage. It redefines AI as a worldwide endeavour focused on revealing latent potential, tackling urgent issues, and constructing systems that emphasise societal well-being. This metaphor is applied to three key AI technopoles: the United States, the European Union, and China, illustrating how recontextualising AI development in each setting can unveil novel discursive and policy opportunities. By extracting essential metaphorical elements and applying them comparatively, we demonstrate how the treasure hunt framework more effectively corresponds with the principles of responsibility, inclusivity, and long-term thinking.

We contend that altering the metaphors employed to conceptualise AI progress is not solely a matter of semantics but rather a strategic endeavour. The frameworks we select influence both creativity and behaviour. By adopting the metaphor of an AI treasure hunt, we aim to encourage a more collaborative, ethically sound, and progressive perspective on the future of global AI competition.

This work introduces a novel thermodynamic framework for analysing Disruption Tolerant Networks (DTNs) through statistical physics and percolation theory. By mapping peer-to-peer communication dynamics onto a one-dimensional binary state (Ising spin) model, we establish a mathematical foundation for understanding collective behaviour in decentralised communication systems. In our approach, communication links are effectively modelled as spin states (up or down, active or inactive), with social activity serving as an analogue to temperature in traditional thermodynamic systems.

The research applies Renormalisation Group (RG) theory to systematically investigate phase transitions and critical phenomena in DTN connectivity patterns. Through this formalism, we derive expressions for correlation length, connectivity, and system entropy, revealing fundamental relationships between social interaction patterns and network resilience. Our analysis demonstrates that the correlation length of DTN communication exhibits exponential scaling with decreasing social restrictions, highlighting how network effectiveness is intrinsically linked to the level of social activity permitted by crisis conditions.

The approach provides insights into different centralised network disruption scenarios, particularly relevant for crisis communication strategies. We identify two major application contexts: direct network disruption (such as cyber incidents as part of hybrid warfare) and indirect network disruption (such as natural disasters like earthquakes and floods). In scenarios with maintained social activity, DTNs can provide crucial communication infrastructure not reliant on network servers. However, in cases of strictly limited social activity (e.g., pandemic lockdowns, floods), the advantages of DTNs are neutralised, potentially leaving communities more dependent on traditional centralised infrastructure.

To address this vulnerability, we propose a dual-pronged approach leveraging both human and technological solutions. This includes equipping civil defence staff with high-capacity ICT devices, setting up network beacons in strategic places or deploying autonomous drone swarms to serve as semi-centralised instances for ground-based communication.

While DTNs offer alternatives to centralised infrastructure, their effectiveness requires careful consideration of technical requirements and social activity. The mathematical approach yields primarily qualitative insights in this initial investigation but establishes a strong basis for future quantitative analyses. These findings contribute to the broader understanding of complex dynamic systems in communication networks while offering concrete implications for resilient communication infrastructure design in challenging environments.

Effective verification of irreversible nuclear disarmament requires innovative frameworks capable of addressing the inherent complexities and risks of disarmament processes. Verification authorities must strategically allocate their limited annual inspections across various categories, necessitating a careful balance of priorities regarding inspection objectives, timing, and frequency. Given the importance of these decisions, the lack of research adopting a holistic, systems-level perspective that prioritizes long-term verification activities in line with planned steps toward irreversibility is concerning. Moreover, the effectiveness of verification strategies at different stages of disarmament-particularly in the post-disarmament period-has not been adequately examined. The State-Level Concept (SLC), developed by the IAEA to enhance the effectiveness of nuclear safeguards implementation, represents a transformative shift by moving from facility-specific evaluations to comprehensive state-level assessments. At its core is Acquisition Path Analysis (APA), which systematically identifies and evaluates potential pathways a state could exploit to acquire weapons-usable material. Complementing this, the IAEA's physical model provides a tailored framework that maps the technical processes required to transform source material into weapons-usable nuclear material, customized to each state's unique nuclear infrastructure. By integrating a systems-based approach and physical modeling, the SLC could offer a transparent framework to define precise verification objectives, analyze technically plausible pathways, and prioritize measures strategically, enhancing effectiveness of disarmament treaties. Therefore , this study proposes a systems-based approach to disarmament verification, focusing on optimally allocating limited inspection resources across different nuclear disarmament phases. Adapted physical model is used to address state-specific nuclear infrastructures, incorporating elements such as civilian and military facilities. Through directed graph modeling, the research identifies and ranks technically plausible cheating pathways, with particular emphasis on concealed activities during warhead dismantlement and weapon-usable material disposition. It is coupled with strategic assessments using game theory to optimize inspection priorities and resource allocation. To ground the analysis, a comparative case study examines how different irreversibility steps in disarmament — specifically during the drawdown and complete end-state phases — influence the allocation of verification resources. Verification strategies were tailored to each phase, with resources shifting from verifying the dismantlement of weapons to monitoring against potential rearmament. The findings highlight the critical importance of strategic resource allocation; by directing verification efforts toward the highest-risk pathways, inspection effectiveness increased without additional resources. Another key finding is that although increased budgets generally enhance verification effectiveness, without implementation of safeguards, effectiveness plateaus and cannot reach its maximum. This underscores that strategic resource allocation and cost-effective verification technologies are more crucial than simply increasing funding. These findings yield critical insights for policymakers and international bodies in crafting credible and effective verification frameworks. By integrating a physical model with risk-based resource allocation, the approach ensures flexibility and applicability across a range of geopolitical settings.

The Alva Myrdal Centre for Nuclear Disarmament (AMC) at Uppsala University, Sweden, is an interdisciplinary research center focusing on nuclear disarmament. The AMC was established in 2021 and consists of eight working groups with different focuses and from academic different disciplines. One working group is purely technical and directed towards technical verification and monitoring.

In this presentation, we will first give a short overview of the AMC and its main activities. Then, we will present the current research topics pursued by the technical working group. One of these is radionuclide monitoring and the development of sensitive detectors for measuring small quantities of radionuclides from nuclear test explosions. In collaboration with the Swedish Defense Research Agency (FOI), a technique for measuring weak signals with coincident gamma spectrometry is being developed. This work is intended to strengthen the verification regime used by the Comprehensive Test Ban Treaty Organization (CTBTO).

Another topic is disarmament verification with passive and active interrogation to be able to verify presence or absence of nuclear material. The working group is represented in the International Partnership for Nuclear Disarmament Verification (IPNDV) and has taken part in the BeCamp2 measurement campaign organized by SCK-CEN during 2023.

In the area of fuel cycle analyses, the working group has modelled reactor systems in Pakistan and North Korea to quantify their current possible plutonium production. Furthermore, the group has focused on the Swedish now decommissioned Ågesta reactor, a heavy water moderated reactor that was built in the 50s and 60s for possible use as a source of Swedish plutonium. The Ågesta reactor was eventually used as a civil power reactor, but it is a suitable reactor for developing methods of nuclear archaeology, by using the operator’s archive to extract core geometries, fuel characteristics and power history necessary for reactor modelling.

Apart from these research topics, the working group is involved in teaching activities on topics of nuclear disarmament. We teach basic physics of nuclear weapons as well as advanced topics like verification of nuclear test explosions. Members of the technical research group have also contributed to a learning module on nuclear weapons hosted by the EU Non-Proliferation and Disarmament Consortium. This module will be launched shortly.

The Democratic People’s Republic of Korea’s (DPRK) nuclear programme continues to expand without limits from a nonproliferation or arms control agreement. Since the departure of the IAEA in 2009, beyond what the DPRK chooses to reveal itself, much of the information we have gained about the trajectory of the programme has come from satellite imagery.

Large electro-optical satellite constellations have enabled day-to-day monitoring of key DPRK facilities, particularly at Yongbyon. After the destruction of the cooling towers in 2008, the 5MWe reactor’s operational status was determined by observation of water outflow that was primarily visible in tasked sub-1m resolution imagery. In contrast, operations of the Experimental Light Water Reactor have been linked to a larger water outflow that is visible in daily 3m resolution imagery.

In addition, satellite imagery beyond the visible spectrum has provided new insights into the DPRK programme. Notable applications of synthetic aperture radar (SAR), high resolution thermal imagery and night imagery from the Visible Infrared Imaging Radiometer Suite (VIIRS) have provided new insights into the programme.

This presentation will demonstrate, with new observations from 2025, how emerging satellite capabilities can be used to monitor a complex and evolving nuclear programme, such as the DPRK’s.

In the case of new disarmament treaties aimed at reducing the number of nuclear warheads, reliable mechanisms for warhead dismantlement must be established. Warhead confirmation systems can assist in these processes, as they are capable of verifying whether nuclear warheads, warhead components, or fissile material are either present or absent. Several systems based on gamma spectroscopy have already been proposed, including the Trusted Radiation Identification System (TRIS) by the Sandia National Laboratories, as well as the Information Barrier eXperimental II (IBX II) developed at Princeton University.

These systems measure the energy distribution of emitted photons using sodium iodide scintillators. In the context of nuclear warhead confirmation, the measured emissions are referred to as a signature. If two objects exhibit the same signature, they are assumed to be identical. During a disarmament process, for instance, the signature of a confirmed nuclear weapon can be compared to that of an object the dismantling state claims to be a nuclear weapon.

However, such signatures are not guaranteed to be unique – meaning that alternative configurations could potentially replicate the signature of a genuine weapon. This issue was already identified in 1997 by the US Office of Arms Control and Nonproliferation as a key unresolved challenge in gamma spectroscopy.

It has since been confirmed that existing systems could, in fact, be deceived by cleverly constructed hoax objects. These could consist, for example, of an optimized combination of radioactive isotopes that would produce the same signature as a nuclear warhead. Additionally, the question arises, of whether shielding effects from other materials could also contribute to a hoax, introducing additional possibilities for constructing more sophisticated hoaxes. A malicious actor could, for instance, suppress secondary emission lines through selective shielding or generate additional spectral lines via characteristic X-ray emission from the shielding material.

To investigate this matter is the focus of our work. We examined whether combinations of shielded radioactive isotopes can produce gamma emission signatures that are indistinguishable from those of actual nuclear warheads. For this, we performed extensive OpenMC simulations of photon transport through different materials. In a subsequent analysis, the simulated transmission rates for different photon energies were used to calculate shielded emission spectra of radioactive isotopes. A minimization algorithm was applied to identify configurations of shielded isotope whose signatures most closely resemble those of actual nuclear warheads.

Our results demonstrate that shielding effects can give rise to new types of hoax objects capable of deceiving gamma spectroscopy based warhead confirmation systems. Consequently, ensuring signature uniqueness in these systems remains a challenge that needs to be addressed on an even broader scale.

Mass spectrometric measurements on uranium samples taken in nuclear facilities and their surrounding environment can provide a wide range of important information about activities being carried out in these facilities. Not only the degree of uranium enrichment (²³⁵U/²³⁸U) can be determined, the ²³⁶U/²³⁸U isotopic ratio is a widely used tracer, which provides sensitive information on source identification for safeguard purposes, nuclear forensics studies and environmental monitoring [1]. An additional strong tool in nuclear forensics is the ²³⁰Th/²³⁴U chronometry. The method relies on the fact that uranium ore processing and further chemical purification of uranium (i.e. for enrichment) removes almost all impurities, including all radioactive decay products. In the case of the ²³⁰Th/²³⁴U chronometer the decay of ²³⁴U with a half-life of 245,500 years to ²³⁰Th is used for age determination. Measuring the parent-daughter ratio in the sample, and assuming a quantitative separation of impurities and daughter isotopes from the U-solution, the decay equations can be applied to calculate the time elapsed since the date of the last purification. This method was developed for the age-determination of samples with high ²³⁵U enrichment, and therefore comparably high ²³⁴U contents, and for large sample quantities of several milligrams [2].

For the detection of undeclared activities in nuclear facilities, swipe and environmental samples are taken containing only traces of uranium bearing microparticles which can be analyzed for isotopic composition. In the case that undeclared activities are detected, the time when these activities have happened needs to be verified. Therefore, more sensitive analytical methods must be developed for a reliable ²³⁰Th/²³⁴U age-dating application [3]. Advanced mass spectrometry methods like SIMS with large-geometry instruments are considered the preferential analytical methods to determine the isotopic composition of these environmental samples with a very high precision [4]. The successful development and establishment of a method for age-dating application mainly relies on the accessibility of well-designed reference materials that are not only used for calibration of the analytical device, but also for the determination of important measurement parameters, such as the relative sensitivity factor.

This presentation will provide some general background information about the analyses of microparticulate samples containing known uranium isotopic ratios and Th abundances with a focus on the development of reference particles with well-defined properties designed particularly for new age-determination applications.

Literature: [1] Diez-Fernández, H.,et al.: Talanta 206 (2020) 120221. [2] Vargas, Z., et al.: Applied Radiation and Isotopes 102 (2015) 81-86. [3] Szakal, C., et al.: Analyst 144(14) (2019) 4219-4232. [4] Groopman, E. E., et al.: Journal of Analytical Atomic Spectrometry 37(10) (2022) 2089-2102.

There are currently numerous innovative nuclear reactor designs being proposed as part of what could be the next era of commercial nuclear energy production. Many of them follow a trend of reducing construction and footprint scale by increasing compactness and integration. Such is the case of Small Modular Reactor (SMR) concepts, a subcategory of Novel Advanced Reactors (NARs), conceived for modular production, transportation and assembly. Another key feature of various NAR designs is the use of novel fuels such as TRISO (graphite-coated uranium pebbles) or liquid salts with fuel cycles different from the traditional uranium one. As opposed to uranium fuel rods, these alternatives are to be employed as bulk materials, sometimes in constant flow, and in some cases are foreseen to remain enclosed within the reactor for its entire lifetime. While offering economic, practical and temporal advantages, these atypical structures and fuels in NARs make them, at present, more opaque to external examination. Thus posing the challenge of developing corresponding novel measuring and inspection techniques to quantify and monitor NAR reactor inventories for safeguards purposes, amongst others.

The study being presented addresses this challenge by considering Nuclear Resonance Fluorescence (NRF) as a tool for the non-destructive probing of NARs, with the objective of identifying and quantifying specific fuel isotopes relevant to non-proliferation verification. NRF is a process in which a sample of interest is irradiated with a beam of high-energy photons. The nuclei in the sample absorb a fraction of the high-energy photons and subsequently emit further high-energy photons that can escape the material and thus be detected. The energy of the emitted photons depends on the emitter’s nuclear structure and can therefore be used as a signature to identify specific isotopes. Making the technique appropriate for the detection and quantification of fissile material within a non-fissile environment. Since the energies of the photons are high enough to travel through shielding materials, this method could be potentially used to non-destructively inspect the interior composition of objects such as NARs.

A feasibility analysis of this promising application of NRF is being carried out with a focus on the interaction between high-energy photon beams and the specific shielding materials that can be present in such reactors. The comprehensive classification of these materials across predominant NAR designs is used as a starting point to determine the properties relevant to NRF and the availability of corresponding experimental data. Followed by the investigation of photon beams in equivalent bulk material combinations, conducted through preliminary computer simulations. Therein including the identification of limiting factors such as the absence of data and the characteristics of photon sources and detectors necessary for the practical implementation of NRF measurements in this context. An initial assessment is thus presented of the potential advancement of the NRF measuring approach as a NAR non-proliferation verification technique.

New types of nuclear reactors are being actively developed in several countries and considered as future sources of low-carbon electricity. Among these, especially the concept of “Small Modular Reactors” (SMRs) has gained traction in policy and investment circles, for domestic or export use. These concepts, if successful, not only foresee an overall increase in nuclear capacity but also an increase in nuclear sites, thanks to the more flexible deployment plans. Furthermore, many of these concepts intend to use nuclear fuel with higher-than-before uranium enrichment to offset the technical drawbacks of smaller reactor sizes. This potential increase in number of reactors and sites combined with the higher fissile material content in the fuel (up 20% instead of 3-5%) leads to new proliferation concerns. Traditional non-proliferation safeguards are centered on large facilities with large inventories and long breakout times, due to the low enrichment. A shift away from this model requires a rethinking of effective safeguards, especially due to the logistical and budgetary restraints on a safeguards inspectorate.

In the last decade, there have been advancements in monitoring nuclear power plants using the antineutrino emissions of active reactor cores, including the successful deployment of tonne-scale prototypes at traditional large nuclear power plants. Antineutrinos are produced by the fission fragments produced in an active reactor. These emissions are a continuously emitted spectrum directly tied to the core content, i.e. a spectral measurement can provide a “fingerprint” of the plutonium and uranium content. Additionally, antineutrino emissions are impossible to shield effectively, allowing for reactor monitoring at a stand-off distance of up to tens of meters and outside the reactor building itself – making it highly attractive as potential safeguards tool for monitoring sites autonomously and non-intrusively.

In the first stage of the nuSENTRY project, OpenMC-based simulations of future reactor types, chiefly SMRs and related compact reactors – such as naval reactors – are conducted to understand the expected antineutrino spectra of an SMR-like reactor throughout the entire fuel/reactor lifecycle. These findings will be used to understand the applicability of existing and future antineutrino detection technologies for these new types of reactors. In future stages of the nuSENTRY project, these reactor simulations will be combined with Geant4-based detector simulations to evaluate the feasibility of antineutrino detection as safeguards tool for SMR installations. Different detection approaches will be compared as new detector R&D can potentially provide directional discrimination of reactors – a boon for SMR-type sites with multiple reactors in a small area. Furthermore, it is also planned to consider the use of secondary signatures present at a nuclear site, including long-term neutron measurements or use of cosmic muons for building imaging, to enhance confidence in the antineutrino measurements.

Fusion energy systems, while avoiding the use of fissile materials such as highly enriched uranium and plutonium, still pose certain proliferation risks. Key concerns include the diversion of tritium for military purposes, the production of weapon-grade plutonium using fusion neutrons, and the dual-use potential of laser/inertial confinement fusion facilities for nuclear weapons development. This talk examines these risks with a focus on material monitoring challenges, the technical feasibility of plutonium breeding in fusion reactors, and the role of advanced experimental and computational methods in circumventing nuclear test bans. Strategies for mitigating proliferation risks include the integration of safeguards-by-design in early-stage reactor concepts, international standardization of monitoring frameworks, and fostering dialogue between fusion research and nonproliferation communities. Given the increasing global interest in fusion energy, these measures are critical to ensuring that its development remains secure and aligned with peaceful objectives.

In geopolitical conflicts and arms races, nuclear weapons, missiles and space systems are connected in many ways. Risks for international security and stability are difficult to contain by arms control, non-proliferation and disarmament, facing limited motivations and capabilities. Constraints are hard to verify for dual-use potentials and complex interactions among weapon types and delivery systems, air and missile defenses, command and control.

Addressing the complexity of challenges, a framework of verification and security provides a basis to systematically compare nuclear, missile and space arms control. To be effective, agreements needs to be adequately verified to build confidence and assure compliance of State Parties. Preconditions are to define the goals of legal requirements and means of monitoring treaty-limited items and activities, balancing what can and should be verified. Verification is to identify permitted activities and provide early warning of prohibited military capabilities for timely responses minimising security risks. Residual security risks determine the degree of (non-)verifiability, avoiding and detecting intolerable deviations from prescribed activities beyond significance thresholds with reasonable efforts. Related security issues and verification options (national technical means, on-site inspections, safeguards, multilateral vs. bilateral mechanisms) are discussed for existing, past and future arms control agreements of nuclear weapons (NPT, NWFZ, CTBT, TPNW, NWC), missiles (INF Treaty, MTCR, New START, missile ban) and space systems (OST, ABM Treaty, ASAT ban).

The task is to build a firewall against high-risk events which combines technical indicators (capabilities), and contextual factors (security environment): (a) identify high-risk activities, materials and equipment that should be prohibited; (b) determine permissible activities consistent with peaceful applications of technology and know-how; (c) assess in-between activities. Possible criteria for evaluation include benefit-cost-risk effectiveness of verification requirements and instruments; efforts applied to weapons lifecycle stages (from R&D and testing to deployment and elimination), and objects (destructive mechanism, materials, equipments, facilities); breakout scenarios (countermeasures, significance threshold, risk reduction); and uncertainties (dual-use, transparency and confidence-building). Adaptive verification includes stages with different criteria for nuclear, missile and space arms control:

1. Do not have access to high-risk capability, materials or components: Baseline information exchange and data gathering identify the current status of capabilities with reasonable accuracy without proliferating sensitive information. This includes declarations, on-site inspections and remote monitoring of status and location of components, materials, facilities and delivery.
2. Prevent and detect (re-)armament advancing capability to breakout from constraints: prohibited items and activities need to be detected leading to high-risk capability to ensure that legitimate and dual-use capabilities are not converted for such prohibited purposes.
3. Disarm and disinvent existing capability to the degree possible: Disarmament verification monitors agreed pathways to reduce and eliminate risky capabilities by active dismantlement and disposal, conversion or destruction of nuclear facilities.
4. Remove intentions to acquire advanced capability and discourage their reemergence by creating a favourable security environment: Implement political, organisational and societal mechanisms to improve contextual factors of verification, including national ratification and implementation, conflict resolution and institutional regulations, security, public discourses, education and societal participation.

A common challenge with debates on irreversibility of nuclear disarmament is that,

while most agree on its importance, there is little shared understanding of the meaning and implications of the concept. This is true on multiple levels, both in terms of broader goals and outlook and especially in terms of practical steps and approaches.

This paper will argue that irreversibility is intrinsically linked to another concept used in studies of nuclear non-proliferation, namely nuclear latency – the cumulative possession of capabilities needed to develop nuclear weapons. Linking irreversibility and latency is helpful in understanding the role of remaining nuclear capabilities in a disarmed world, the risks they pose, and in identifying some possible approaches to mitigating those risks.

While both latent capabilities and re-armament intentions may exist in concrete forms, neither may be fully discernible to those assessing the risks of that state rearming. There are ways of observing and characterising both, but none are perfect. When faced with this challenge, states might prefer to overestimate the risk of nuclear rearmament than underestimate it and suffer the consequences unprepared.

This predicament resonates with anyone seeking to understand the risks today that an unarmed state may acquire nuclear weapons for the first time. The perspectives involved in this risk assessment are very similar to those that would be involved in assessing the risks of reversible nuclear disarmament. But in a disarmed world, they would be measured from an entirely different frame of reference to the world we live in now. This challenges our imagination to reconsider how latent nuclear capabilities and political intentions might be observed in a disarmed world, and how those observations might inform our assessments of rearmament risks – before, during, and after disarmament.

This paper will draw on existing understandings of capabilities related for nuclear proliferation, including approaches learned from IAEA Safeguards; studies of technology development, weaponisation and militarisation; and considerations on the role of knowledge, and organisational factors. These various aspects of nuclear weapon latency can be combined to form a broad, holistic set of indicators by which states might assess the risks that a disarmed state might disarm. The paper will discuss such a set of indicators and discuss various ways in which they would be relevant in a nuclear disarming and a nuclear disarmed world.

The proposed analytical approach, of looking at irreversibility and latency as deeply related phenomena, and framing irreversibility as the long-term management of risks arising from nuclear latency after disarmament, aims to not only offer a different perspective on the issue of defining and understanding irreversibility, but also to highlight some practical approaches that future work on irreversibility can build on.

An effective implementation and compliance framework is essential for any future nuclear disarmament treaty. Although various elements have been proposed, a comprehensive and cohesive approach that effectively deters rearmament remains elusive. To help address this gap, the VeSPoTec research consortium conducted a 1.5-day tabletop exercise focused on irreversibility and compliance in a regional nuclear disarmament scenario. The exercise brought together experts from international organizations, think tanks, and research institutions to simulate the implementation and verification of a fictional regional nuclear disarmament agreement involving three hypothetical nuclear-armed states. Participants explored the prospective role and mandate of a Regional Verification Organization (RVO) while negotiating tailored, state-specific measures to ensure compliance and irreversibility in the disarmament process.

The simulation was structured around three key components: defining the mandate of the RVO, negotiating state-specific verification strategies, and testing the framework through compliance scenarios. This approach allowed participants to address practical challenges in implementing regionally tailored disarmament agreements while maintaining synchronized progress among state parties with different nuclear capabilities and fissile material stocks.

During the exercise, the ad hoc development of a comprehensive disarmament framework was instrumental in uncovering the key challenges that future efforts will need to address. Participants were tasked with defining a suitable institutional and legal scope of the RVO while reconciling diverging technical approaches to disarmament. Such divergences for instance emerged around how to ensure irreversibility, with experts placing varying emphasis on different components of the nuclear fuel cycle. Because all participants represented nuclear-armed states, proposed verification approaches tended to favour confidentiality and limited oversight. The absence of non-nuclear-armed state perspectives, which might have favoured more intrusive measures, highlighted how stakeholder identify can shape verification design. Interestingly, these constraints allowed participants to explore creative options for increasing the costs of reversal early in the process with minimal interference.

Playing out a scenario based on limited trust between state parties allowed the participants to address what level of confidence might be sufficient to determine compliance. It also stimulated discussions around exit strategies, such as maintaining certain capabilities, ensuring readiness to re-arm, and drawing the line between hedging and legitimate deterrence actions. Moreover, the presence of differing nuclear capacities and fissile material stocks emphasized the complexity of pursuing equal standards in state-RVO agreements.

Beyond identifying such challenges, the exercise fostered dialogue on enhancing treaty robustness – underscoring the role of capacity building, technological cooperation, and selective transparency in fostering mutual trust and balancing disarmament with national security and industrial interests. The diverse backgrounds of participants enabled discussions that blended technical and political perspectives with regional insights from the Middle East, South and East Asia, the United States, and Europe.

Overall, the VeSPoTec tabletop exercise highlights the key challenges in implementing regionally tailored disarmament agreements. By highlighting the need to reconcile divergent perspectives in developing coherent verification frameworks, the exercise provides valuable insights that should inform future disarmament efforts and negotiations.

Recent years have seen multiple UN Member States express support for the proposal of a Group of Scientific and Technical Experts on Nuclear Disarmament Verification (GSTE-NDV) within the United Nations. The initiative’s proponents argue that the GSTE-NDV would provide unique and practical benefits in support of the long-term goal of nuclear disarmament and enable UN Member States to work collaboratively on nuclear disarmament verification in a multilateral setting. Following UN General Assembly (UNGA) Resolution 79/240, the UN is seeking views from member states on the possible merits, objectives, mandate and modalities of a GSTE-NDV, through written submissions as well as a series of informal consultations. The results of this process will be published in September as a report by the UN Secretary General, which will be submitted to the UNGA’s eightieth session in late 2025. During this year’s session, the UNGA may also be called to vote on a resolution on establishing the GSTE-NDV.

We will discuss the origin of the concept and some historical precedents; and what value its proponents consider it can have in the context of other work on nuclear disarmament and the wider geopolitical environment. We will then outline the key questions about a GSTE-NDV, including its objectives, possible mandate and modalities, format, location and reporting structures; as well as the Group’s membership. We will also examine similarly structured institutions, such as international panels or advisory bodies, that could be examined as possible models and for lessons learned and its role in capacity-building for the development of multilateral nuclear disarmament verification capabilities. Finally, we will outline options and recommendations for these as food-for-thought.

Exploring Antineutrino-based Safeguards for Naval Propulsion Reactors

In a world with an increasingly chaotic security landscape, the danger of nuclear proliferation is rising. In recent years, a new potential proliferation concern has emerged with the planned employment of nuclear propulsion in submarines by Non-Nuclear Weapon States under the NPT. A prominent example of this is the sale of conventionally armed, nuclear powered attack submarines by the US and the UK to Australia under the AUKUS agreement, effectively placing significant quantities (SQs) of special nuclear material outside of traditional safeguards regimes due to their military nature. Here, it is important to give safeguards inspectors powerful tools for a comprehensive and reliable safeguards regime, capable of detecting a potential diversion of weapons-grade nuclear material.

Here, we present research on the development and the detailed simulation of an antineutrino detector for the monitoring of a nuclear-powered submarine anchored in the base of a consenting host state. Nuclear reactors are the biggest manmade sources of antineutrinos, which are produced by the beta decay of the fission products. Their spectral distribution is directly dependent on the amount and type of nuclear material present in the reactor. Although they rarely interact with other matter, and thus are difficult to detect, this is offset by the huge number of antineutrinos produced in the reactor. Their detection via the inverse beta decay, whereby an incident antineutrino turns a proton into a neutron, thus enables stand-off monitoring without revealing sensitive information about the reactor’s design. To this aim, we will simulate a naval reactor with OpenMC, and the subsequent detection of its antineutrino emission a few tens of meters away using Geant4. The goal is to produce a model of a compact, tonne-scale detector suitable for use at a naval base of a consenting host state in the context of non-proliferation safeguards. While focusing on the type of nuclear reactors relevant for the AUKUS-class submarines, we will explore the plausible parameter space of nuclear reactors typically employed in other submarines in terms of enrichment fraction (focusing on HEU fuel), reactor power (from tens to a few hundred MWth), and burnup. Finally, we will explore deployment concepts and possible measurement and verification regimes to implement this approach in the context of safeguards

With the suspension of New START – the last standing U.S.–Russia nuclear arms control treaty, and prospects for its extension after expiry in 2026 uncertain, insights into nuclear deployments available from on-site inspections are lost. Moreover, the poor quality of U.S.–Russia and U.S.–China relations renders prospects for nuclear weapons agreements in the foreseeable future low. The consequences are reduced insights into nuclear deployments, increased worst-case assumptions and risks of nuclear weapons use, and loss of opportunities for creating shared understandings and forging mutual trust. Before this backdrop, it is expected that satellite remote sensing will be a critical tool for assessing nuclear forces and postures. Today, there is abundant satellite data generated from diverse imaging modalities and over multiple frequency bands with high temporal resolution available for perusal by governments and civil society. In view of the sheer size and diversity of datasets, data fusion and data analysis will increasingly be facilitated by machine learning (ML) / artificial intelligence (AI) techniques. This article takes as its entry point the urgency of conceptualizing satellite remote sensing, potentially involving the use of ML/AI, as a crucial component of future nuclear arms control founded on and promoting trust. However, the current data ecosystem exhibits factors that could impact the trustworthiness of compliance assessments based on the data workflows. Those factors are disparate and diffuse data sources and diverse actors. This article explores those factors in two steps. First, a case study in the use of ML/AI and satellite imagery is considered, demonstrating baselining and subsequent monitoring of activities at a chosen nuclear weapons deployment, production, storage, or dismantlement site. The case study is used to give a mixed quantitative–qualitative account of trustworthiness-impacting pressure points as encountered in data access, processing, and analysis, including from the potential use of synthetic imagery for model training. Second, the article looks at adjacent treaty regimes where the factors – disparate and diffuse data sources and diverse actors – have played a non-trivial role: the International Atomic Energy Agency safeguards regime and Comprehensive Test Ban Treaty Organization’s International Monitoring System and International Data Center. Technical reports and documented member state views articulated in the respective international forums are analyzed to draw relevant lessons for the arms control context. The article concludes by discussing the implications of the conducted two-step analysis for the prospects of future arms control as well as implications for the role – negative or positive – of ML/AI-facilitated satellite remote sensing in a future treaty verification regime, while fully cognizant that the certainty requirements for risk reduction and threat management differ from those for treaty verification or recently proposed “demonstrative verification.”

The presented research explores the novel biosecurity threats arising from the growing convergence of large language models (LLMs), biological design tools (BDTs) ), and automation technologies—including robotics— in the life sciences. A critical distinction is drawn between the varied risk profiles of LLMs and BDTs, underscoring how LLMs have the potential to democratize access to dual-use knowledge and reduce technical barriers to biological misuse. In contrast, BDTs could enable technologically sophisticated actors to design potential pandemic pathogens (PPP) or sophisticated biological weaponry. In addition, we assess the potential of AI-tools and automation technologies to diminish the barriers to entry for non-experts in bioengineering and analyze its implications for the design-build-test-learn cycle and its enabling capacity. In the realm of potential bioweapons, the analysis shows that these AI systems accelerate the entire development process - from knowledge access to experimental design to experimental optimization - while breaking down tacit knowledge barriers. As a result, previously experience-based expert knowledge is becoming increasingly technologizable and thus potentially usable by non-state, malicious actors. To prepare for a future in which AI can autonomously conduct tasks such as gene design, pathogen modeling, experimental planning, and execution—via self-driving laboratories and autonomous robotics equipped with decision-making logic—it is essential to critically assess the implications of such advancements. We therefore highlight the challenges of balancing innovation with responsible governance and propose possible pathways to mitigate risk. By elucidating these new frontiers in biosecurity threats, we aim to inform proactive policy-making and responsible innovation in the rapidly evolving landscape of AI-enabled biotechnology.