Longitudinal study of iodine in market milk and infant formula via epiboron neutron activation analysis

A global radionuclide monitoring system is being engineered as part of a multi-technology verification system for the Comprehensive Nuclear Test Ban Treaty. The system detects airborne radioactive aerosols and gases that can indicate nuclear weapons test debris. The backbone of the system is a network of 80 remote detection stations that utilize high-volume air sampling and high-resolution gamma spectrometry to provide in-situ assay and near-real time reporting. These stations are linked to the International Data Centre, which is a central data processing hub where raw spectral data is automatically processed, analyzed, and disseminated to the states parties. Measurements are categorized based on spectral content to determine which contain anomalous anthropogenic radionuclides that require intensive radiochemical analysis at a certified laboratory. The resulting system has the capability to measure microbecquerel concentrations of radionuclides and provide accessible data products within minutes of field measurements. During the past year of international operations, the minimum detectable concentrations and spectroscopy processing statistics were recorded as a function of geographical location and time. The results show that this system is an effective tool for nuclear test monitoring, as well as other applications such as radiological emergency response, public health monitoring, and scientific research.     

Ashing and microwave digestion of aerosol samples with a polypropylene fibrous filter matrix

Radionuclide monitoring is one of the key techniques required by the International Monitoring System (IMS) and On-Site Inspection (OSI) in the Comprehensive Nuclear Test Ban Treaty (CTBT). There shall be a global network of 80 radionuclide monitoring stations. Atmospheric aerosols are collected generally on filters in the stations. A polypropylene (PP) fibrous filter is often used in sampling atmospheric aerosols. There might be much information to be obtained by measuring aerosol samples after digestion rather than nondestructive analysis directly by γ-spectrometry. The present work focused on pretreatment of the filter samples, which includes the influence of different ashing or microwave digestion conditions on the recoveries of analytes. The inductively coupled plasma-atomic emission spectrometric detection results indicated that the recoveries of elements in the PP fibrous filters by ashing were influenced by ashing time, temperature and the properties of the elements. High recoveries of volatile elements and consistent recovery for other elements were obtained by using a closed microwave system to digest the filters. Higher sensitivity was also obtained when the intercomparison sample was measured by a HPGe well detector after pretreatment by the recommended ashing and microwave digestion procedures.     

Fission product ratios as treaty monitoring discriminants

The International Monitoring System (IMS) of the Comprehensive Test Ban Treaty Organization (CTBTO) is currently under construction. The IMS is intended for monitoring of nuclear explosions. The radionuclide part of the IMS monitors the atmosphere for short-lived radioisotopes indicative of a nuclear weapon test, and includes field collection and measurement stations, as well as laboratories to provide reanalysis of the most important samples and a quality control function. The Pacific Northwest National Laboratory in Richland, Washington hosts the United States IMS laboratory, with the designation “RL16.” Since acute reactor containment failures and chronic reactor leakage may also produce similar isotopes, it is tempting to compute ratios of detected isotopes to determine the relevance of an event to the treaty or agreement in question. In this paper we will note several shortcomings of simple isotopic ratios: (1) fractionation of different chemical species, (2) difficulty in comparing isotopes within a single element, and (3) the effect of unknown decay times. While these shortcomings will be shown in the light of an aerosol sample, several of the problems extend to xenon isotopic ratios. Due to the difficulties listed above, considerable human expertise will be required to convert a simple mathematical isotope ratio into a criterion which will reliably categorize an event as ‘reactor’ or ‘weapon’.     

Application of the nuclide identification system SHAMAN in monitoring the Comprehensive Test Ban Treaty

SHAMAN is an expert system for qualitative and quantitative radionuclide identification in gamma spectrometry. SHAMAN requires as input the calibrations, peak search, and fitting results from reliable spectral analysis software, such as SAMPO. SHAMAN uses a comprehensive reference library with 2600 radionuclides and 80 000 gamma-lines, as well as a rule base consisting of sixty inference rules. Identification results are presented both via an interactive graphical interface and in the form of configurable text reports. An organization has been established for monitoring the recent Comprehensive Test Ban Treaty. For radionuclide monitoring, 80 stations will be set up around the world. Air-filter gammaspectra will be collected from these stations on a daily basis and they will need to be reliably analyzed with minimum turnaround time. SHAMAN is currently being evaluated within the prototype monitoring system as an automated radionuclide identifier, in parallel with existing radionuclide identification software. In air-filter monitoring, very low concentrations of radionuclides are measured from bulky sources in close geometry and with long counting time. In this case true coincidence summing and self-absorption become important factors. SHAMAN is able to take into account these complicated phenomena, and the results it produces have been found to be very reliable and accurate.     

Prospects for the introduction of wide area monitoring using environmental sampling for proliferation detection

The International Atomic Energy Agency (IAEA) is committed to strengthening and streamlining the overall effectiveness of the IAEA safeguards system within the context of the Non-Proliferation Treaty (NPT). The IAEA has investigated the use of environmental monitoring techniques and a variety of techniques were studied as part of extensive field trials. The efficacy of long-range monitoring depends on the availability of mobile signature isotopes or compounds and on the ability to distinguish the nuclear signatures from background signals and attribute them to a source. The Comprehensive Nuclear Test Ban Treaty (CTBT) also requires a variety of environmental sampling and analysis techniques. This paper serves as a scientific basis to start discussions of environmental sampling techniques that could be considered for wide-area monitoring for the detection of undeclared nuclear activities within the NPT or for the possible future use within the CTBT.     

Particulate matter, iron, and zinc in the atmosphere of a large Brazilian town

A Radionuclide Aerosol Sampler/Analyzer (RASA Mark 4) has been developed at PNNL for use in verifying the Comprehensive Nuclear Test Ban Treaty (CTBT). The RASA Mark 4 collects about 20,000 m³ of air per day on a 0.25 m² filter. This filter is automatically decayed for 24 hours, then advanced to a germanium detector for a 24 hour count. This system has been operated in Richland, WA for a limited period of time in a predeployment testing phase. The germanium-detector gamma-ray spectra have been analyzed by automatic spectral analysis codes to determine Minimum Detectable Concentrations (MDC) for a number of isotopes of interest. These MDC's have been compared to other atmospheric measurements in the field and in the laboratory.     

Construction of a shallow underground low-background detector for a CTBT radionuclide laboratory

The International Monitoring System is a verification component of the Comprehensive Nuclear-Test-Ban Treaty, and in addition to a series of radionuclide monitoring stations, contains 16 radionuclide laboratories capable of verification of radionuclide station measurements. This paper presents an overview of a new commercially obtained low-background detector system for radionuclide aerosol measurements recently installed in a shallow (>30 meters water equivalent) underground clean-room facility at Pacific Northwest National Laboratory. Specifics such as low-background shielding materials and active shielding methods will be covered.     

Reinforced evidence of a low-yield nuclear test in North Korea on 11 May 2010

In May 2010 unique aerosol-bound and noble gas (xenon) radionuclide signatures were observed at four East Asian surveillance stations designed to detect evidence of nuclear testing. An article published in early 2012 provided an analysis that suggested the findings were due to a low-yield underground nuclear test in North Korea on 11 May 2010. As the aerosol and noble gas datings, however, only agreed on the fringes of their uncertainties an official North Korean telegram that on 12 May 2010 reported about a nuclear fusion experiment 1 month earlier inspired a solution. Assuming that included a low-yield nuclear explosion and that it had left xenon isotopes in the same cavity, the xenon dating could be “moved” to overlap with the aerosol dating. The article stirred a serious controversy where representatives of the U.S. government and the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) refused to comment on it. In this paper the xenon dating agrees with the aerosol one without resorting to a previous explosion. It shows instead that fractionation during lava cooling is the explanation and how that plays a paramount role in how xenon signatures from underground nuclear explosions should be interpreted. It also presents new observations that effectively imply that no nuclear reactor or any other nuclear installation could have caused the May 2010 signals. All in all these are the most interesting and rich ones ever encountered by the Organization and they truly demonstrate that the verification system can deliver much better sensitivity than it was originally designed for.     

An anion exchange technique for separation of Na and K for neutron activation analysis of W-Ti alloy

Anthropogenic radioactivity is being measured in near-real time by an international monitoring system designed to verify the Comprehensive Nuclear Test Ban Treaty. Airborne radioactivity measurements are conducted in-situ by stations that are linked to a central data processing and analysis facility. Aerosols are separated by high-volume air sampling with high-efficiency particulate filters. Radio-xenon is separated from other gases through cryogenic methods. Gamma-spectrometry is performed by high purity germanium detectors and the raw spectral data is immediately transmitted to the central facility via Internet, satellite, or modem. These highly sensitive sensors, combined with the automated data processing at the central facility, result in a system capable of measuring environmental radioactivity on the microbeequerel scale where the data is available to scientists within minutes of the field measurement. During the past year, anthropogenic radioactivity has been measured at approximately half of the stations in the current network. Sources of these measured radionuclides include nuclear power plant emissions, Chernobyl resuspension, and isotope production facilities. The ability to thoroughly characterize site-specific radionuclides, which contribute to the radioactivity of the ambient environment, will be necessary to reduce the number of false positive events. This is especially true of anthropogenic radionuclides that could lead to ambiguous analysis.     

Fitting formula for the injection volume of a gas chromatograph for radio‐xenon sampling in the lower troposphere

GC is usually used for xenon concentration and radon removal in the International Monitoring System of the Comprehensive Nuclear‐Test‐Ban Treaty. In a gas chromatograph, the injection volume is defined to calculate the column capacity. In this paper, the injection volume was investigated and a fitting formula for the injection volume was derived and discussed subsequently. As a consequence, the xenon injection volume exponentially decreased with the column temperature increased, but exponentially increased as the flow rate increased.     

Cesium-137 concentrations, trends, and sources observed in Kuwait City, Kuwait

As part of the development support for the Comprehensive Nuclear-Test-Ban Treaty (CTBT), the Prototype International Data Center (PIDC) has been processing radionuclide data since 1995. Radionuclide data received from field stations includes gamma-ray spectra, meteorological data, and state of health (SOH) information. To date over 20 radionuclide monitoring stations have transmitted data to the PIDC. The radionuclide monitoring system collects both aerosol and gas samples. Gamma-ray spectral analysis is performed on the samples to determine if they contain anthropogenic radionuclides indicative of nuclear debris. A key radionuclide monitored by this system is ¹³⁷Cs. Due to the half-life of ¹³⁷Cs (30.17 y), amounts of this radionuclide releases are still present in the soil and atmosphere as a result of past nuclear tests and reactor releases. ¹³⁷Cs from these sources are routinely detected in the prototype CTBT radionuclide monitoring system. Out of the multiple stations that contribute data to the PIDC, the highest ¹³⁷Cs activity concentrations and largest range of concentrations are observed at the Kuwait City, Kuwait station. A special study was conducted to investigate the concentrations, trends, and origin of ¹³⁷Cs in the Kuwait aerosol. This study combines over four years worth of aerosol data, meteorological data and soil sample analysis to explore this matter.     

Field testing of collection and measurement of radioxenon for the Comprehensive Test Ban Treaty

Pacific Northwest National Laboratory, with guidance and support from the U.S. Department of Energy's NN-20 Comprehensive Test Ban Treaty (CTBT) Research and Development program, has developed and demonstrated a fully automatic sampler-analyzer (ARSA) for the collection and quantitative measurement of the four xenon radionuclides,^131mXe (11.9 d),^133mXe (2.19 d),¹³³Xe (5.24 d), and¹³⁵Xe (9.10 h), in the atmosphere. These radionuclides are important signatures in monitoring for compliance to a CTBT, and may have applications in stack monitoring and other areas where xenon radionuclides are present. The activity ratios between certain of these radionuclides permit discrimination between radioxenon originating from nuclear detonations and that from nuclear reactor operations, nuclear fuel reprocessing, or from medical isotope production and usage. With the ARSA system, xenon is continuously and automatically separated from the atmosphere at flow rates of about 100 lpm by sorption-bed techniques. Samples collected in 8 hours are automatically analyzed by electron-photon coincidence spectrometry to provide detection sensitivities as low as 100 μBq/m³ of air. This sensitivity is about 10-fold better than achieved with reported laboratory-based procedures¹ for the short time collection intervals of interest. Gamma-ray energy spectra and gas analysis data are automatically collected.     

Xe-135 production from Cf-252

The presence of ¹³⁵Xe is often used as an indicator that fission has occurred, and is used to help enforce the Comprehensive Test Ban Treaty. There are no known commercial suppliers, though it can be acquired. Readily available standards of this isotope are very useful. ¹³⁵Xe can be produced through fission, or by neutron capture on ¹³⁴Xe. At the INL, scientists have previously transported fission products from an electroplated ²⁵²Cf thin source for the measurement of nuclear data of short-lived fission products using a technique called He-Jet collection. A similar system has been applied to the collection of gaseous ¹³⁵Xe, and ¹³³Xe, in order to produce standards of these isotopes.     

Radiocerium separation behavior of ultrafiltration membranes

The Comprehensive Test Ban Treaty calls for the monitoring of aerosol radionuclides throughout the globe. Pacific Northwest National Laboratory has developed the Radionuclide Aerosol Sampler/Analyzer (RASA) for the Department of Energy to automatically collect and measure radioactive aerosols from the atmosphere. The RASA passes high volumes of air through a 3M^TM Substrate Blown Microfiber Media (SBMF) specifically designated as SBMF-40VF. It then automatically moves the filter media in front of a high-purity germanium detector and collects a gamma spectrum. If further analysis on the filter is desired, the filter is sent to a laboratory and radiochemical analysis is performed. This paper discusses the method of dissolution of the SBMF-40VF filter media and the separation of the radioisotopes of interest.     

Production of <Superscript>37</Superscript>Ar in The University of Texas TRIGA reactor facility

The detection of ³⁷Ar is important for On-Site Inspections (OSI) for the Comprehensive Nuclear-Test-Ban Treaty monitoring. In an underground nuclear explosion this radionuclide is produced by ⁴⁰Ca(n,α)³⁷Ar reaction in surrounding soil and rock. With a half-life of 35 days, ³⁷Ar provides a signal useful for confirming the location of an underground nuclear event. An ultra-low-background proportional counter developed by Pacific Northwest National Laboratory is used to detect ³⁷Ar, which decays via electron capture. The irradiation of Ar gas at natural enrichment in the 3L facility within the Mark II TRIGA reactor facility at The University of Texas at Austin provides a source of ³⁷Ar for the calibration of the detector. The ⁴¹Ar activity is measured by the gamma activity using an HPGe detector after the sample is removed from the core. Using the ⁴¹Ar/³⁷Ar production ratio and the ⁴¹Ar activity, the amount of ³⁷Ar created is calculated. The ⁴¹Ar decays quickly (half-life of 109.34 min) leaving a radioactive sample of high purity ³⁷Ar and only trace levels of ³⁹Ar.     

Engineering upgrades to the Radionuclide Aerosol Sampler/Analyzer for the CTBT International Monitoring System

The Radionuclide Aerosol Sampler/Analyzer (RASA) is an automated collection and analysis system designed for aerosol radionuclide monitoring for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The advantages of an automated system include minimal need for human intervention and consistent analytical data. However, maintainability and down time issues threaten this utility, even for systems with over 90 % data availability. Engineering upgrades to the RASA are currently being pursued to address these issues, as well as measures relevant to technical lessons learned from the Fukushima nuclear power plant event. Current work includes a new automation control unit and other potential improvements such as alternative detector cooling and sampling options. This paper presents the current state of upgrades and improvements under investigation.     

Testing and provisional operation of the IMS radionuclide monitoring network

A worldwide radionuclide network of 80 stations, including 40 with noble-gas-detection capability forming part of the International Monitoring System, has been designed to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty. Pending entry into force of the Treaty, the certified stations are operating provisionally and so far an experience of over 100 station-years has been acquired for particulate stations. Noble gas systems are still under testing, though the operational experience is fast growing. A maintenance strategy is being developed on the basis of the experience acquired so far and the analysis of equipment failure.     

Experience of the Finnish National Data Centre in radionuclide analysis for the Comprehensive Nuclear-Test-Ban Treaty

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is setting very specific requirements to processing of gamma-ray spectra. All the data collected in 80 radionuclide particulate stations are transmitted to the International Data Centre (IDC), where they are analyzed. National Data Centres (NDC) are the users of IDC services. The NDC's are responsible of giving technical information to National Authorities, who have thepolitical responsibility of the compliance to the treaty. The IDC analysis is not directly informing if a nuclear test has been conducted; it is just categorizing the spectra to help the NDC's to make their decision. An NDC must have a high confidence on the correctness of the radionuclide analyses the IDC, and the NDC itself, are performing. Special attention must be paid to Event Screening, where the NDC, among other things, needs a historical record of the measured data to be able to ignore the occasionally occurring fission products, for example. The amount of data produced is too large for an NDC to process interactively. Therefore, batch-processing capabilities are required from the NDC. The Finnish NDC is involved in evaluating of the IDC processing and software and it is also proposing a radionuclide processing solution for other NDC's, as well.     

{\rtf1\ansi\ansicpg1250\deff0\deflang1038\deflangfe1038\deftab708{\fonttbl{\f0\froman\fprq2\fcharset238{\*\fname Times New Roman;}Times New Roman CE;}} \viewkind4\uc1\pard\f0\fs24 Digital signal processing in prompt-gamma activation analysis \par }

Summary The International Data Centre of the Comprehensive Nuclear-Test-Ban Treaty Organisation receives atmospheric radioactivity data from the monitoring stations of the International Monitoring System. The Centre is a processing hub through which raw data and analysis results flow to Treaty Member States. Data are processed automatically upon receipt, and then interactively reviewed and screened for detection of CTBT-relevant radionuclides. Atmospheric back-tracking for source location is included in the IDC functions. This paper describes the role of the IDC in this verification effort, the types of radionuclide monitoring data received, the automatic and interactive processing, and the products distributed to Member States.     

Automated separation and measurement of radioxenon for the Comprehensive Test Ban Treaty

A fully automatic radioxenon sampler/analyzer (ARSA) has been developed and demonstrated for the collection and quantitative measurement of the four xenon radionuclides,^131mXe(11.9 d),^133mXe(2.2 d),¹³³Xe(5.2 d), and¹³⁵Xe(9.1 hr), in the atmosphere. These radionuclides are important signatures in monitoring for compliance to a Comprehensive Test Ban Treaty (CTBT). Activity ratios of these radionuclides permit source attribution. Xenon, continuously and automatically separated from the atmosphere, is automatically analyzed by electron-photon coincidence spectrometry providing a lower limit of detection of about 100 μBq/m³. The demonstrated detection limit is about 100 times better than achievable with reported laboratory-based procedures for the short-time collection intervals of interest.