Potential Source Apportionment and Meteorological Conditions Involved in Airborne 131I Detections in January/February 2017 in Europe.

Traces of particulate radioactive iodine (131I) were detected in the European atmosphere in January/February 2017. Concentrations of this nuclear fission product were very low, ranging 0.1 to 10 µBq m-3 except at one location in western Russia where they reached up to several mBq m-3. Detections have been reported continuously over an 8-week period by about 30 monitoring stations. We examine possible emission source apportionments and rank them considering their expected contribution in terms of orders of magnitude from typical routine releases: radiopharmaceutical production units > sewage sludge incinerators > nuclear power plants > spontaneous fission of uranium in soil. Inverse modeling simulations indicate that the widespread detections of 131I resulted from the combination of multiple source releases. Among them, those from radiopharmaceutical production units remain the most likely. One of them is located in Western Russia and its estimated source term complies with authorized limits. Other existing sources related to 131I use (medical purposes or sewage sludge incineration) can explain detections on a rather local scale. As an enhancing factor, the prevailing wintertime meteorological situations marked by strong temperature inversions led to poor dispersion conditions that resulted in higher concentrations exceeding usual detection limits in use within the informal Ring of Five (Ro5) monitoring network.

Analysis of 22Na using a spectral summation technique on high-volume aerosol samples.

Measurement of cosmogenic 22Na in daily aerosol samples is often difficult due to low atmospheric production rates. A new technique based upon spectral summation of sequential high-volume aerosol samples to measure 22Na is described and validated. This summation technique has broad applications to any detection system that produces sequential representative sample measurements in which radioisotopes are just below the detection limit, provided the energy calibration is stable. It is anticipated that a global dataset of this radionuclide will have many important environmental science applications.

Source term estimation of radioxenon released from the Fukushima Dai-ichi nuclear reactors using measured air concentrations and atmospheric transport modeling.

Systems designed to monitor airborne radionuclides released from underground nuclear explosions detected radioactive fallout across the northern hemisphere resulting from the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. Sampling data from multiple International Modeling System locations are combined with atmospheric transport modeling to estimate the magnitude and time sequence of releases of (133)Xe. Modeled dilution factors at five different detection locations were combined with 57 atmospheric concentration measurements of (133)Xe taken from March 18 to March 23 to estimate the source term. This analysis suggests that 92% of the 1.24 × 10(19) Bq of (133)Xe present in the three operating reactors at the time of the earthquake was released to the atmosphere over a 3 d period. An uncertainty analysis bounds the release estimates to 54-129% of available (133)Xe inventory.

Radioxenon detections in the CTBT international monitoring system likely related to the announced nuclear test in North Korea on February 12, 2013.

Observations made in April 2013 of the radioxenon isotopes (133)Xe and (131m)Xe at measurement stations in Japan and Russia, belonging to the International Monitoring System for verification of the Comprehensive Nuclear-Test-Ban Treaty, are unique with respect to the measurement history of these stations. Comparison of measured data with calculated isotopic ratios as well as analysis using atmospheric transport modeling indicate that it is likely that the xenon measured was created in the underground nuclear test conducted by North Korea on February 12, 2013, and released 7-8 weeks later. More than one release is required to explain all observations. The (131m)Xe source terms for each release were calculated to 0.7 TBq, corresponding to about 1-10% of the total xenon inventory for a 10 kt explosion, depending on fractionation and release scenario. The observed ratios could not be used to obtain any information regarding the fissile material that was used in the test.

Monte Carlo simulation of a PhosWatch detector using Geant4 for xenon isotope beta-gamma coincidence spectrum profile and detection efficiency calculations.

A simulation tool has been developed using the Geant4 Toolkit to simulate a PhosWatch single channel beta-gamma coincidence detection system consisting of a CsI(Tl)/BC404 Phoswich well detector and pulse shape analysis algorithms implemented digital signal processor. The tool can be used to simulate the detector's response for all the gamma rays and beta particles emitted from (135)Xe, (133m)Xe, (133)Xe, (131m)Xe and (214)Pb. Two- and three-dimensional beta-gamma coincidence spectra from the PhosWatch detector can be produced using the simulation tool. The accurately simulated spectra could be used to calculate system coincidence detection efficiency for each xenon isotope, the corrections for the interference from the various spectral components from radon and xenon isotopes, and system gain calibration. Also, it can generate two- and three-dimensional xenon reference spectra to test beta-gamma coincidence spectral deconvolution analysis software.

Statistical analysis of uncertainties of gamma-peak identification and area calculation in particulate air-filter environment radionuclide measurements using the results of a Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) organized intercomparison, Part I: assessment of reliability and uncertainties of isotope detection and energy precision using artificial spiked test spectra, Part II: assessment of the true type I error rate and the quality of peak area estimators in relation to type II errors using large numbers of natural spectra.

In this paper, the uncertainties of gamma-ray small peak analysis have been examined. As the intensity of a gamma-ray peak approaches its detection decision limit, derived parameters such as centroid channel energy, peak area, peak area uncertainty, baseline determination, and peak significance are statistically sensitive. The intercomparison exercise organized by the CTBTO provided an excellent opportunity for this to be studied. Near background levels, the false-positive and false-negative peak identification frequencies in artificial test spectra have been compared to statistically predictable limiting values. In addition, naturally occurring radon progeny were used to compare observed variance against nominal uncertainties. The results infer that the applied fit algorithms do not always represent the best estimator. Understanding the statistically predicted peak-finding limit is important for data evaluation and analysis assessment. Furthermore, these results are useful to optimize analytical procedures to achieve the best results.

The INVITTOX Data Bank of in-vitro techniques in toxicology.

The dissemination of information about methods in in-vitro toxicology is subject to a number of constraints which are identified and discussed, as are the ways in which INVITTOX seeks to address these problems. The continued interest of scientists in INVITTOX suggests that a real gap in information provision is being filled.