Conveners
P2.3 Atmospheric and Subsurface Radionuclide Background and Dispersion: e-poster session
- Christian Maurer (Bundesanstalt für Geologie, Geophysik, Klimatologie und Meteorologie (GeoSphere Austria))
- Jana Meresova (CTBTO Preparatory Commission)
Description
E-poster session with display of each e-poster on an assigned touchscreen
Radionuclide monitoring for nuclear explosions requires sufficient information and an adequate understanding of existing radioxenon sources which are frequently observed as background in atmospheric noble gas samples. In the absence of measured discharge data from nuclear installations, one can only revert to rough approximations of discharges based on publicly available information. In many...
The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) relies on atmospheric transport modelling (ATM) to establish a link between potential source locations and measurement locations of radionuclides. Currently, FLEXPART v9 is used, which simulates radionuclide transport pathways using an idealized noble gas assumption. However, particulate matter undergoes significant dry and wet...
Zaporizhya Nuclear Power Plant is facing the risk of unexpected accidents. If it is damaged, lots of radioactive materials will be released into the air. The atmospheric dispersion model named LADAS (Lagrangian Atmospheric Dose Assessment System) was applied to evaluate the behaviour of radioactive material released into the air for the hypothetical nuclear accident at Zaporizhya. The global...
A central challenge of radioxenon monitoring for the CTBT remains to classify radioactive xenon isotopes originating from reactor sources. This was also crucial for the interpretation of radioxenon detections in the aftermath of the announced North Korean nuclear test explosions. Due to its geo-location, the IMS noble gas system at RN38 played a crucial role for that. At RN38, Takasaki,...
Radiation Protection Centre has launched a network of three SAUNA QB and one SAUNA III atmospheric radioxenon measuring stations in Lithuania. Measurements are performed regularly since the end of 2024 and the number of episodes with the elevated radioxenon (mostly 133Xe) concentrations were detected. The backward atmospheric transport modeling using HYSPLIT computer code allowed us to...
We present our work on the CHIMERE Assisting Radioactive Analysis Toolkit (CARATk), a new toolkit for the CHIMERE chemistry transport model. This toolkit will permit simulation of transport, chemistry and physical processes of radionuclides in the atmosphere.
Our poster will focus on two main points in our development of CARATk.
Firstly, we validate the eulerian transport CHIMERE by...
Xenon radionuclides atmospheric monitoring is part of the International Monitoring System, including multiple measurement stations, that were developed in the context of the Comprehensive Nuclear-Test-Ban Treaty. However, civil infrastructures, mainly nuclear power plants and medical isotope factories, constantly generate these radionuclides, creating a global atmospheric...
Development of nuclear devices tends to take place in secrecy, without sharing specification of technical details. Tests are generally performed underground and unannounced. Seismics will announce a detonation and give an approximate location and time. One of the challenges of CTBTO is the reverse engineering of the specs of the nuclear device itself. After some containment time, noble gases...
Radionuclide monitoring is one of the CTBT verification technologies that measures radioactive particles and noble gases generated by nuclear explosions. Detecting underground nuclear explosions (UNEs) is challenging as these events are unlikely to release radioactive particles into the atmosphere. To address this, monitoring noble gases more likely to escape into the atmosphere has been...
In case of an underground nuclear explosion (UNE), the waveform component of the International Monitoring System (IMS) that is being established by the Preparatory Commission of the Comprehensive Nuclear-Test-Ban Treaty allows for the determination of the location and timing of the event. To confirm the nuclear character of any UNE, the radionuclide component of the IMS searches for traces of...
This study is about radioxenon Xe-133 background in the Southern and Northern hemispheres and to discuss the influence of this context on nuclear test identification.
The study was carried out in four CTBTO stations in Northern and Southern hemispheres. They were chosen taking into account NPPs and medical facilities close the stations. Data was extracted from Review Radionuclide Report (RRR)...
Previously, it was reported that decades-old Ar-39 that remained from the original nuclear explosions at a few Underground Nuclear Explosion Signature Experiment testbeds (U20-az and P-tunnel) at the Nevada National Security Site had been detected. We have undertaken a set of new measurements at several additional vertically-emplaced historic UNE sites specifically chosen to investigate this...
The relative abundances of radioxenon isotopes in underground nuclear explosions depend on the direct production by fission and the β-decay of their radioactive precursors. Since the precursors are moderately volatile elements that can condense into the magma within the nuclear cavity as the system cools off, the radioxenon budget available for subsequent migration to the atmosphere, as well...
Knowing the time pattern of radioxenon releases is crucial for expert analysis in nuclear explosion monitoring. The standard assumption, which uses a constant discharge rate based on the average of the annual total, is overly simplistic. The noble gas measurement systems are not typically sensitive to continuous emissions and instead usually observe puff emissions. The measurement data from...
The nuclear nature of any explosion occurrence under the CTBT can be determined/established using the detections of any relevant radionuclides at IMS stations. This plays an essential role in the compliance monitoring of the Treaty. During an explosion, Radionuclide materials, specifically radioxenon gases, can be carried in the atmosphere or vented from underground or underwater source. Since...
The knowledge of the natural background of xenon radioisotopes in the ground is required to be able to distinguish it from any signals due to a potential underground nuclear explosion, as would be the case during an on-site inspection (OSI). The natural background of xenon isotopes from spontaneous fission in the soil has been studied during several measurement campaigns in Sweden. In most of...
The turbulent diffusion coefficient is the rate at which turbulent motion disperses radionuclides. It controls the rate of spread of their concentrations into the atmosphere, thus influencing their behaviour. The turbulent diffusion coefficient is an essential parameter in the study of atmospheric transport, and the accurate determination of its value in the atmosphere is crucial. This study...
A numerical study of conjugate flow, heat and mass transfer by natural convection of noble gases within an underground cavity partially filled with molten rock is presented. The molten rock is initially considered at rest at an initial temperature and concentration. The molten rock is viscous and possesses strength that is temperature and crystal fraction dependent. Under natural conditions,...
The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) monitors radionuclide detections with the International Monitoring System (IMS) and uses atmospheric transport modelling (ATM) to establish a link between the location of detection and potential sources. ATM simulates the movement of released substances into the atmosphere, taking into account synoptic wind patterns and topography....
The estimation of a source in the CTBT context is an ill-posed problem that is highly sensitive to small variations in data, whether meteorological information or radionuclide concentration values. The current version of the Web-Grape software includes three methods for identifying possible source regions. The first two methods rely on the correlation between measured concentration values and...
Estimation of Xe133 emissions associated with nuclear tests is a challenging task for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) due to noble gas background emissions from nuclear power plants, research reactors, and medical isotope production facilities. These background emissions make data interpretation from the International Monitoring System (IMS) a complex issue since...
Underground nuclear explosions produce radioxenon, which may be transported through the geology and subsequently collected and measured locally in an On-Site Inspection or regionally via the International Monitoring System. Predicting how much radioxenon may be available for collection and measurement requires development of geology-specific subsurface gas transport models to estimate timing...
Since March 2021, the Pacific Northwest National Laboratory (PNNL), in cooperation with Radiation Protection Center in Lithuania, has been supporting a radionuclide background measurement campaign in Pabrade, Lithuania. This measurement campaign aims to provide a better understanding of background detections in a previously unobserved region. Lithuania is a complex region for measuring...
When scientists aim to predict atmospheric dispersion of particulates or gases, they rely on physics codes that require significant computational resources and time for accuracy. To address this, we developed a novel artificial intelligence method to speed up modeling with high accuracy. This method includes two components:
1. Temporal Module: Predicts the temporal evolution of the plume...
Understanding and accurately modelling Xe-133 is fundamental for the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty. Therefore, the potential of nudging techniques within FLEXPART-LCM, the Linear Chemistry Module of FLEXPART 11, to improve global Xe-133 background concentration...
Standard atmospheric transport modelling can be of great help for categorizing specific radioxenon observations but will not prevail on average when it comes to screening out nuclear explosion signals that are mixed into the global industrial background. The challenge pertains to both poorly characterized emissions and uncertainties in the modelled dispersion. Improved screening can be...
Previous studies on the trajectories of air masses from nuclear power plants in the Florida peninsula showed that they contribute to the radioxenon background in the northern Caribbean Sea when the center of the migrating anticyclone was in the Gulf of Mexico and Lousiana, North America.
The objective of this work is to determine whether the Turkey Point and Saint Lucie NPP discharges...
The International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) operates a global network of stations designed to detect potential violations of the CTBT. As a critical part of this system, the noble gas (NG) network plays a major role for the monitoring of radioxenon isotopes. Recently, extended episodes of elevated concentrations of radioxenon were...
Xenon isotopes are relevant to the monitoring regime of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). We report radioxenon measurements data taken directly at source, deriving emission inventories for International Monitoring System (IMS)-relevant isotopes and isotopic ratios used to discriminate nuclear explosions from civil emissions. Time series activity plots have been produced from...
We present ocean modelling work aimed at detecting the debris from nuclear detonations in the ocean. By following the dispersion of near-surface warm pools of radionuclides from specific starting positions, we assess their likely spreading rates and pathways for some months after the explosions, enabling on-site monitoring or sample collection to take place with the best chance of detection....
Some strong indications were identified to confirm nuclear research reactors (NRRs) as a possible source of radioxenon emission generated by neutron activation from stable xenon. This source type is of high relevance to nuclear explosion monitoring for two reasons. First, the isotopic activity ratios may be confused with nuclear explosion signals. Second, neutron activation generates other...
Radioxenon emissions originating from a variety of nuclear facilities (e.g. nuclear power plants) induce a variable and observable background that poses a challenge for the global monitoring of nuclear explosions since it may conceal signals resulting from a nuclear test explosion. More precision is required to accurately model civilian facilities so that noble gas detections can be screened...
Whenever 135Xe is observed, it must originate from a fresh release due to its short half-life (9.2 hours). An activity ratio of 135Xe to 133Xe above 5 is an indicator for a possible nuclear test release. Therefore, it is important to fully understand observation of very high activity ratios of 135Xe to 133Xe in atmospheric air and even 135Xe without simultaneous observation of 133Xe as they...
The International Monitoring System stations may occasionally detect radionuclides relevant to the CTBTO. Such is the case of station MXP44, which is located in Guerrero, in the Mexican state of Baja California. Cesium-137 was detected three times in the year 2024 with a level 4 categorization. The objective of this work is to estimate the possible source origin of the cesium-137 detections....
Atmospheric transport and dispersion models (ATDM) are routinely used in the simulation of the global radioxenon background as well as in the localisation and characterisation of unknown radioxenon emitters. However, ATDMs contain uncertainties due to the assumptions made in the model setup as well as the chaotic nature of the atmosphere. Currently, quantification of these uncertainties and an...
Each anthropogenic emission possesses a unique radionuclide composition, serving as a 'fingerprint' that enables the identification of radionuclide contamination sources. This report presents a cutting-edge and rapid technique for radionuclide detection and source identification, focusing on ultra-trace concentration levels critical for detecting small-scale nuclear tests. Radionuclide...
Following an underground nuclear explosion, fission products may be vented to the surface and transported through the atmosphere. Initial systems built for nuclear explosion monitoring were based on requirements assuming a simple release of these fission products. A more rigorous evaluation of the inventory releases will provide better requirements for IMS stations and improve analysis of...
Atmospheric transport modelling requires the rapid estimation of a radionuclide source term (including radioxenon) potentially released to the atmosphere from an underground nuclear cavity. A versatile model must include venting to the atmosphere and seepage into the host rock, allowing for barometric pumping. The nuclear cavity is connected to the ground surface by two interacting media,...
Air pollution, including radiological pollution, is one of the most harmful consequences of industrialization because of its strong influence on both human health quality and climate in general. Often a need appears to identify one single strong source of air pollution. Such a source may be the result of accident or routine release from nuclear industry. We propose a new algorithm for a single...
Isotopic activity ratios of 135Xe to 133Xe above 5 are considered as an indicator for a possible nuclear test release. High activity ratios of 135Xe to 133Xe in atmospheric air and even 135Xe without simultaneous observation of 133Xe are occasionally observed at IMS noble gas systems. Whenever 135Xe is observed, it must come from a fresh release because its half-life is just 9.2 hours. Despite...
The RN43 station, located in Nouakchott, Mauritania, is a key component of the International Monitoring System (IMS) under the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). Established in 2006, the station plays a crucial role in detecting and analyzing airborne radionuclides, contributing to global atmospheric transport models and radiological risk assessments. Due to its...
In September 2024, anthropogenic radionuclides observed from RN64 station located in Tanzania. This incident triggered us to make a review of data analyses from CDC from January 2010 up October 2024. Key finding includes the detection of both natural and anthropogenic radionuclides (fission and activation products). However, the interest was on anthropogenic radionuclides (fission and...
The detection of underground nuclear explosions by means of the radioactive gases generated during the explosion requires a sufficient fraction of radionuclides to be emitted to the atmosphere. In the case of late seepage observed after a few days to a few weeks, this fraction is very small and results from the transport of gases under the combined effects of thermal gradient and barometric...
Understanding the propagation of the waveform and radionuclide signals is an important component of the International Monitoring System. On October 18th, 2023 we executed a 16.3 T chemical explosive experiment with stable radioxenon and tritium tracers to understand pressure-driven transport through the subsurface. The initial chemical explosion and subsequent gas migration were monitored with...
Belgium remains an important emitter of radioactive xenon into the atmosphere. These emissions are not harmful to the environment, but they can interfere with the very sensitive noble gas detection stations that are part of the verification regime of the Comprehensive Nuclear-Test-Ban Treaty Organization. Radioxenon stack emission data from civilian nuclear facilities, combined with...
The development and validation of noble gas transport models through field collected data is critical in the improvement of nuclear explosion monitoring techniques. Complex surface terrain in the area of release can drastically impact the transport of the resulting plume and the subsurface geology can alter material flow to the surface, resulting in large discrepancies in release times,...
The Source Term Analysis of Xenon (STAX) project is an international technical collaboration that has been installing stack monitors in partnering nuclear facilities and sharing stack effluent data with National Data Centers for use in better understanding Xe background sources detected by the International Monitoring System (IMS). The STAX project is now in its 7th year and during the course...
Radioxenon discharges from nuclear power reactors (NPPs) are frequently detected by the noble gas monitoring systems of the International Monitoring System. However, the standard assumption of continuous releases is not realistic. It has been demonstrated that ramping power down and up during operations are occasions of elevated discharges, which are most likely to be observed. Despite this,...
Detection of radioactive gas from potential underground nuclear explosions can provide irrefutable evidence of nuclear testing. To better understand gas transport from underground explosions toward the surface, scientists in the Low Yield Nuclear Monitoring Program have implemented an experimental program involving tracer gases and high explosives by-product gases released from underground...
The detection of xenon isotopes in the atmosphere plays a critical role in monitoring nuclear explosions under the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Understanding the temporal and geographical distribution of CTBT-relevant xenon isotopes, such as 131mXe, 133Xe, 133mXe, and 135Xe is essential for distinguishing between natural, medical, and anthropogenic sources and potential...
Many Arab countries in the Middle East face negative impacts from dust fallout, which includes both natural and human-made radionuclides. This study thoroughly analyses long-term atmospheric radionuclide levels in Kuwait. Over ten years (2013–2022), daily measurements of natural and anthropogenic radionuclides—specifically 137Cs, 7Be and 40K—were collected using the RN40 station. The average...
The ability to detect and localize radiation sources and special nuclear materials is key for many fields including nuclear security, safeguarding and nuclear materials nonproliferation. A fundamental aspect in in-field detection or imaging is the availability of an accurate natural background radiation map in the area of interest. In general, countries map background radiation levels for many...
A background analysis of xenon in Nigeria would enhance the understanding of its release and dispersion from reactors and natural sources. Although Nigeria lacks a nuclear power plant, it operates a research reactor in Zaria (11.1512° N, 7.6546° E) and is planning a 2GW multipurpose research reactor in Sheda (8.8569° N, 7.0434° E). Nigeria’s strategic location between IMS stations in Niger...
The measurement of radionuclides is continually performed by International Monitoring System (IMS) operated by the Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission (CTBTO PrepCom). The detection of radionuclides plays an important role in confirming if an explosion is nuclear or chemical. As radioactive gases are transported through the subsurface environment, there is...
In 2017, the Government of Japan has decided to make a voluntary contribution to further strengthen the capabilities of the CTBTO verification regime. As part of that initiative, two transportable noble gas measurement systems were deployed in Japan, in Horonobe and Mutsu. They started operations in January 2018 and March 2018, respectively. In January 2025, a third transportable measurement...
Bundesamt für Strahlenschutz (BfS) has been operating a network with weekly sample collection at 6-8 locations in Germany with sampling starting in 1977. Since 2024, this network is complemented by the automatic Xenon system Sauna Qb with a sampling period of 12h followed by automatic radioxenon analysis. The shorter sampling periods of the Sauna Qb promise a much better ability to...
