Activity determination without tracers in high-resolution alpha-particle spectrometry

High-resolution alpha spectrometry was applied for the activity determination of 10 reference sources containing different amounts of ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu and ²⁴²Pu. They were analyzed as blind sources using a novel spectrum analysis tool ADAM. The information needed in the spectrum unfolding was taken only from the spectrum under investigation, and no tracers were applied. Therefore, a Monte Carlo program AASI was used to compute geometrical detection efficiency of the measurement setup. All reported activities corresponded to those of the reference sources within expanded uncertainty. The developed tools can be used for the activity determination in nondestructive alpha spectrometry or when the radionuclide composition does not change during the sample processing.     

Standoff alpha radiation detection for hot cell imaging and crime scene investigation

Optical Review - This paper presents the remote detection of alpha contamination in a nuclear facility. Alpha-active material in a shielded nuclear radiation containment chamber has been localized...     

Collection and behaviour of radon progenies on thin Mylar foils

Thin Mylar foils are often used to protect detectors from contamination. However, these foils can be electrostatically charged, possibly leading to their contamination with airborne radon progenies. In the present work, the collection and behaviour of radon progenies on Mylar foils was investigated in detail using alpha spectrometry. The radon progenies collection rate of a small Mylar foil (3 cm²) is equivalent to an air sampler with a flow rate of approximately 0.1 m³/h. It was demonstrated that such contamination may jeopardise the validity of the entire analysis if not interpreted correctly.     

140La/140Ba ratio dating of a nuclear release

In May 2010, air sampling stations in South Korea, Japan and the Russian Federation detected different unstable xenon isotopes and their progenies attached to aerosol particles. The origin of these fission products remains unclear. Previous studies have suggested that a possible reason for these observations is a nuclear test performed in North Korea in May 2010. In the present paper, preliminary spectra recorded at 2 h intervals at the particulate sampling station in Okinawa, Japan are analysed with rigorous mathematical methods. Based on the activity ratios of the ¹⁴⁰Xe progenies ¹⁴⁰Ba and ¹⁴⁰La in a sudden release scenario, the analysis provides an estimate of 12 May 16:00 (UTC) for the release date of the nuclear debris in the form of ¹⁴⁰Xe. The 95 % uncertainty limits for the release date are 11 May 9:00–13 May 13:00 (UTC). The result is very sensitive to the coincidence correction factor of the measurement setup and a larger uncertainty interval cannot be excluded. A continuous release scenario could also explain the data, possibly referring to a leak in a running nuclear reactor either on shore or in a vessel. No studies were made on the attribution of the observations to a release site. However, our conclusion is that fresh nuclear debris has been detected in East Asia, and further studies are required in an international forum to reanalyse the data. Of particular importance for the time-zero analysis is the a posteriori calibration of the Okinawa station with a ¹⁴⁰Ba sample to resolve the uncertainty related to the coincidence correction and other factors.