The radioactive xenon isotopes Xe-131m, Xe-133, Xe-133m and Xe-135 are important indicators for an underground nuclear explosion. Knowledge about the concentrations and ratios of these isotopes that can be expected due to natural processes is important to be able to discriminate from a nuclear explosion during a CTBT on-site inspection. A series of measurements has been performed 2019 and 2022...
Radon is a naturally occurring radioactive gas produced as a decay product of uranium and thorium in geologic media. Radon is therefore a nearly ubiquitous gas background in the subsurface environment, as well as in many building materials derived from earth materials. In the context of nuclear explosion monitoring, radon as a background influences radiation detector sensitivities as an...
Noble gas systems at International Monitoring System (IMS) radionuclide stations used to operate with 24 or 12 hours sampling time. The next generation noble gas systems utilize shorter sampling periods. At station RN33 on Mount Schauinsland, Germany, a SPALAX system with 24 hours sampling is operated by BfS. A Xenon International system with six hours sampling time was installed in parallel...
Anthropogenic radionuclides have been injected into the atmosphere by nuclear weapon programmes, nuclear weapons testing, nuclear power plants and uranium mining. In this work, we considered the activity concentrations of anthropogenic radionuclides (Cs-137 and Cs-134) detected in the International Monitoring System (IMS) from January 2021 to December 2021. The main objective is to determine...
We are responsible for data analysis and management of radionuclide monitoring stations as the National Data Centre of Japan. There are two International Monitoring System radionuclide monitoring stations in Japan, at Takasaki for particles and noble gases and at Okinawa for particles. The detection frequency of Cs-137 is relatively high at both stations. In this study, we focus on Cs-137...
During the testing phase of the Xenon International radioxenon monitoring system in Knoxville, Tennessee, USA, there were observations of non-traditional xenon isotopes: Xenon-125, Xenon-127, Xenon-129m, and Xenon-122 (via the decay of Iodine-122). While the production mechanisms for non-traditional isotopes were hypothesized, it would be beneficial to perform a complete study on the...
Monitoring radionuclide concentrations is an important component of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) verification regime and can provide direct evidence of the nuclear nature of an explosion. Whereas, in the case of underground nuclear testing, the radioxenon isotopes have the highest probability of escaping into the atmosphere. Four of the xenon isotopes are of interest for...
As part of the Xenon Environmental Monitoring at Hartlepool (XENAH) collaboration, a team of scientists from the UK, US and Sweden have deployed three radioxenon sampling and measurement systems to the north of England, near to the Hartlepool Power Station. The power station comprises two 1600 MW(th) advanced gas-cooled nuclear reactors. The array of SAUNA QB (“cube”) radioxenon measurement...
The radioxenon signatures of 135-Xe, 133-Xe, 133m-Xe, and 131m-Xe are the expected and consistently observed radioxenons in the atmosphere. Testing of the Xenon International System at Knoxville, TN resulted in the detection of several previously unobserved radioxenon isotopes in the atmosphere 125-Xe, 127-Xe, 129m-Xe, and 122-Xe (via the decay of 122-I). These isotopes were periodically...
The Medical Isotope Production (MIP) by fission release radioactive noble gases into the environment.
These emissions increase the environmental background and could hinder the mission of the International Monitoring System (IMS) to detect early a nuclear explosion.
Argentina has been producing radioisotopes by fission since 1985 from the irradiation of Highly Enriched Uranium (HEU) targets....
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 backgrounds of radionuclides in the environment from natural and human made phenomena are well known to interfere with detection of nuclear explosions. International Monitoring System (IMS) stations perform measurements at ground level; however, little has been published regarding the vertical distributions of radionuclides expected from nearby and distant sources and if there is a large...
The Research Organization for Nuclear Energy analyses the dispersion of radioactive air release by using GENII V.2 software. The calculation of GENII V.2 has never been validated with the results of measurements directly and indirectly in the field. The validation of the GENII calculation of I-131 activity concentration was carried out by comparing the results of the GENII calculation of the...
The radioisotope Argon-37 is produced in underground nuclear explosions (UNE) through the neutron activation of Calcium-40 in rock and soil. A sensitivity study was conducted using Monte Carlo N-Particle Code (MCNP) and SCALE to model the predicted production rate of Argon-37 per kiloton explosive equivalent in various rocks following a UNE. The detonation was modelled in MCNP using a simple...
The radiological station located in Havana, Cuba will perform measurements for the International Monitoring System. The Turkey Point and Laguna Verde Nuclear Power Plants are potential sources of noble gases on a regional scale. The objective of this work is to identify the synoptic situations that would contribute to the transit of air masses coming from these facilities through Cuba. For...
This work describes a method for estimating the location, moment and the amount of an unknown atmospheric release of radioactivity, based on detections. First, the source location is estimated by a probability density function based on the time-integrated correlation coefficient between model calculations and measurements of radioactivity concentrations. Model results are calculated with the...
In the International Data Centre radionuclide pipeline, noble gas samples from the International Monitoring System (IMS) radionuclide stations are processed and categorized. The combination of multiple isotope observations of Level C plus prior/post Level B samples close enough in time, at one or more IMS radionuclide stations, forms decisive input for isotopic ratio analysis as these episodes...
An activity evolution model which goes from the release of an assumed underground nuclear explosion, through the atmospheric transport modelling (ATM), to sample collection and measurements can be used to link various quantities, including activities released from a nuclear event, activity concentrations in a plume over an International Monitoring System (IMS) station and activities collected...
Nuclear event radionuclide detection is the next step towards complementing data about any abnormal event recorded by seismic, hydroacoustic and infrasound station networks prior to asking for the approval of the on-site inspection (OSI). Radionuclides travel hundreds of kilometres away from their source under favourable meteorological conditions. In order to determine and assess anthropogenic...
The International Monitoring System (IMS) monitors compliance with the Comprehensive Nuclear Test-Ban Treaty (CTBT) using information collected by sensors (radionuclide, seismic, infrasound, and hydroacoustic) placed around the world. Sensors, however, give limited information; hence scientists at the International Data Centre (IDC) rely on data fusion and atmospheric transport modeling (ATM)...
It has previously been reported at Science and Technology conferences that PNNL has measured Argon-39 at historic underground nuclear explosion (UNE) sites at the Nevada Nuclear Security Site in gas samples from shallow (few meters or less) subsurface soil. Considerable Argon-39 was observed at UNE sites sampled. Thus, the detection of Argon-39 in such samples at strengths sufficiently above...
Exploding wires have been embedded in geologic matrices (concrete, basalt, sandstone, and granodiorite) to study explosive driven elemental diffusion and to elucidate the utility of elemental signatures. The exploding wire detonations have an input energy of up to 900 J equivalent to 0.22 g TNT. Simultaneous to the detonation, monitoring of the air concentration of elements was performed using...
Argon-37 is produced via neutron activation of stable argon or calcium in nuclear reactors. This isotope is used in on-site inspection (OSI) activities. Therefore, its background in the atmosphere from nuclear reactors is an important parameter in interpreting the OSI measurement results. Since its measurement is complicated, only few reports exist on the amount of its production in the...
Monitoring compliance with the Comprehensive Nuclear-Test-Ban Treaty requires, among other things, accurate modelling of the transport of radionuclides in the atmosphere. Crucial to atmospheric transport models (ATMs) when dealing with radioactive particulates are several removal processes, such as dry and wet deposition. Wet deposition in particular plays an often dominant role in the total...
Detection of radionuclides generated from underground nuclear explosions depends, first and foremost, on the movement of nuclides from source to detector. The subsurface environment therefore has a critical role in determining how and when material signatures become detectable. Field-scale tracer experiments are essential to furthering scientific understanding of how the subsurface contains...
A radiological emergency preparedness system in Korea has been developed to predict the behavior of radioactive material released into the environment and estimate the dose assessment for humans in case of a nuclear accident. The system is composed of atmospheric dispersion, marine dispersion, and dose assessment models, along with a graphic user interface module. It can evaluate the...
Given that the on-site inspection area should not exceed 1000 km2, finding the suspected nuclear explosion site is a difficult task requiring extremely accurate methods of assessment. One of the approaches used for nuclear explosion monitoring is to consider sources of radioxenon. Currently, mainly nuclear power plants and medical isotope production facilities are considered as a relevant and...
Of the existing nuclear reactors in the world, the region of the Group of Latin America and the Caribbean (GRULAC) currently has a total of six nuclear power plants operated by Argentina, Brazil and Mexico and 16 research reactors being operated by Argentina, Brazil, Chile, Colombia, Jamaica, Mexico and Peru. Using the RNToolkit web software that allows quick access to data from the...
Current noble gas detection systems for nuclear explosion monitoring are based on the detection of four radioxenon isotopes – Xenon-131m, -133, -133m and -135. The data provided by radioxenon detection could be enhanced by other radionuclide signatures, such as Argon-37. Activation of Calcium-40 in rock by neutrons produces Argon-37, and monitoring for this additional nuclide could help...
Argentina is one of the producers of radioisotopes and the construction of RA-10 responds to the increase in global demand. Increased production of radioisotopes could lead to more release of noble gases. This modern reactor is designed as a multipurpose facility suitable for radioisotope production, material and fuel irradiation research and neutron techniques applications. It is planned to...
Following an underground nuclear explosion, fission products may be vented to the surface and transported through the atmosphere. Traditional requirements for nuclear explosion monitoring systems have focused on simple release scenarios. A more rigorous evaluation of radionuclide inventory releases will provide better requirements for measurement systems and improve analysis of detections. The...
The International Monitoring System (IMS) detects background radioxenon from civilian sources every day. This measurement of the background can interfere with the measurements of radioxenon from nuclear tests. There are methods to discriminate civilian sources with nuclear tests. These include the use of atmospheric transport modelling to determine if the air associated with an IMS measurement...
Measuring radioxenon isotopes is one of the tools used for underground nuclear explosion monitoring. Medical isotope production and reactors also release radioxenon isotopes and discrimination of these benign sources is a key research area. Four isotope ratios have been shown to be a powerful method for discrimination if the isotopes are detected. This research has examined the expected...
Radioxenon is a gaseous fission product produced during nuclear weapons testing. Besides nuclear testing, the biggest radioxenon emission comes from medical isotope production facilities, which emit 109 -1013 Bq/day, while the power plant emits 109 Bq/reactor/day. However, the recent development of generation-IV reactors showed that a potential radioxenon release from a single molten salt...
The global atmospheric background of anthropogenic radionuclides hinders the ability of the Treaty monitoring community to identify possible signatures of a nuclear explosion. In particular, the atmospheric radioxenon background, produced and sustained by civil nuclear facilities such as isotope production facilities (IPFs) and nuclear power plants (NPPs), causes detections on the...
In 2017, the Government of Japan decided to make a voluntary contribution to further enhance the capabilities of the CTBTO verification regime. In that framework, two transportable noble gas systems were deployed in Horonobe and Mutsu, Japan. They respectively started operating in February 2018 and March 2018. Continued operation of the two systems is now financially supported by funding from...
INVAP´s STAX monitor was installed and is measuring at the Ezeiza Atomic Center (CAE-CNEA), Buenos Aires, Argentina since November 2021. Initially, the equipment underwent aliveness tests and calibration with gas like radioactive sources. The electronic set-up was adjusted, in order to optimize measurement performance, thus enabling to track high activity concentration emissions in a...
The International Monitoring System (IMS) noble gas network has proven to be highly reliable, with many years of routine measurements sent to the International Data Centre. With the deployment of noble gas systems, international experts began to routinely see a noble gas background. This background has continued throughout the years, and every single day, the IMS has a radioxenon measurement...
The SPALAX-NG was qualified in 2021 for deployment at International Monitoring System stations. The SPALAX-NG has been operated for several years by CEA/DAM. The SPALAX-NG is a major evolution compared to first generation SPALAX with detection limits of 0.2 mBq/m3 in eight hours for all the relevant radioisotope of xenon, high resolution beta-gamma detection, modularity. This presentation...
To categorize radionuclide data from the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty, the French National Data Center has developed, and has been using in operation for several years, an automated simulation of the industrial background. For all IMS noble gas stations, it calculates every day the expected Xe-133 activity concentrations due to industrial...
Atmospheric transport modelling (ATM) supports the radionuclide verification technology by providing a link between radionuclide detections and the regions of their possible source. In the case of an anomalous detection registered by the International Monitoring System (IMS) particulate network classified as Level 5, CTBTO sends a request for support to Regional Specialized Meteorological...
Radiocesium (Cs-137) is one of the by-products of nuclear fission processes in nuclear reactors and nuclear weapons testing. The deposits of Cs-137 on the ground are resuspended into the atmosphere by different mechanisms like strong winds and forest fires. The major sources can be accidents from nuclear reactors, such as the Chernobyl power plant accident and Fukushima as well as historic...
BAPETEN (Nuclear Energy Regulatory Agency of Indonesia) is currently developing the Indonesian – Radiation Detector Monitoring System (I-RDMS) as an early warning tool to detect environmental radiation exposure increases on the territory of Indonesia. This system aims to check the availability of representative and reliable real-time online data on environmental radioactivity as a Nuclear...
In this study we have used open access data from NASA Earth Science data System and meteorological data from the data set of the International Monitoring System (IMS) stations to find out correlations with the observable detections of radionuclides at the RN43 station in Nouakchott. The data fusion between IMS data and open access data can be considered as a tool for National Data Centres to...
Radionuclides produced from underground nuclear explosions can slowly migrate through the subsurface and vent to the atmosphere, where they are transported to detectors downwind. Underground test sites located in remote areas surrounded by complex terrain features, can greatly affect the detectability of radionuclides once they reach the atmosphere. We describe efforts to validate a modeling...
The Xenon Environmental Nuclide Analysis at Hartlepool (XENAH) collaboration involves scientists from the U.K., U.S and Sweden who are performing measurements of routine emissions from Hartlepool Power Station with cooperation of the reactor operator, EDF Energy. Three diverse and complimentary radionuclide monitoring techniques are being deployed, aiming to characterize radionuclide emissions...
Radionuclide emissions from worldwide nuclear facilities are frequently observed by the CTBT noble gas network. These ever-present and highly variable emissions of the four radioxenon isotopes relevant for CTBT monitoring weaken the abilities of global monitoring of nuclear explosions. This multifaceted problem requires a substantive approach to determining the key steps for distinguishing for...
