In situ gamma spectrometry using portable HPGe detector. Radiological characterization and environmental surveillance around an operating nuclear power plant. Possibilities and limits

In situ technique for measuring radionuclides in the soil using a portable Ge detector is a highly versatile tool for both the radiological characterization and for the monitoring of operating nuclear power plants. The main disadvantage of this technique is related to the lack of knowledge of the geometry of the source whose activity concentration is to be determined. However, its greatest advantage is the high spatial representability of the samples and the lower time and resource consumption than gamma spectrometry lab measurements. In this study, the possibilities and limits offered by in situ gamma spectrometry with a high resolution gamma portable detector in two common uses are shown: First, the radiological background characterization and its relationship with the geology of an area of 2700 km2 are assessed; Secondly, its potential for monitoring man-made activity concentration in soils located around an operating nuclear power plant in Spain for surveillance purposes is evaluated. Finally, high accuracy radiation maps have been prepared from the measurements carried out. These radiation maps are essential tools to know the radioactive background of an area, especially useful to assess artificial radioactive deposits produced after a nuclear accident or incident.

Evaluation of Feasibility of Gamma-Spectrometer NaI PAK-01 and SAS Na M3 Software Application for Regular Radionuclide Analysis of NPP Permissible Wastes

The feasibility of correct NaI gamma-spectrometry activity measurement for each nuclide in 131I, 132I, 133I, 134I, 135I, 133Xe, 135mXe, 135Xe and 222Rn composition is presented. To get this result the special matrix method M3 and SAS Na M3 software were used for spectra processing. SAS Na M3 software was developed for complex NaI gamma-spectra processing. Special algorithms and auxiliary software are used to overcome the problems of the classic spectra processing matrix method. Being used for spectrum processing SAS Na M3 software determines the nuclide composition of the sample, activity of nuclides identified and activities uncertainties. The activity values estimation is made for nuclides not identified in the sample measured but included in SAS Na M3 software nuclides library. The values of minimal detectable activities for NaI ∅3''× 3'' gamma-spectrometer and 1 hour measuring time are ~ 0.6 Bq for 131I, 132I, 133I, 134I and ~ 2 Bq for 135I.

A Method for Identification and Assessment of Radioxenon Plumes by Absorption in Polycarbonates

A method for the retrospective evaluation of the integrated activity concentration of 133Xe during radioxenon plumes and the moment of the plume’s center is proposed and explored by computer modeling. The concept is to use a specimen of polycarbonate material (a stack of Makrofol N foils of thickness 120 µm and 40 µm in 1 L non-hermetic Marinelly beaker) that is placed in the environment or in a controlled nuclear or radiopharmaceutical facility. On a regular basis or incidentally, the specimen may be retrieved and gamma spectrometry in two consecutive time intervals with durations of 8 h and 16 h is performed. To assess the performance of the method, 133Xe plumes of various integrated activity concentrations and with a duration of up to 10 h are simulated and analyzed, assuming that the measurement starts with a delay of up to one day after the moment of the plume center. It is found that the deviation between the estimates by the method and their true values are within a few percent. Depending on the delay, events of integrated 133Xe activity concentration 250–1000 Bq h m−3 might be qualitatively identified. At levels >10,000 Bq h m−3, the uncertainty of the quantitative estimates might be ≤10%.

Technical note: Quantifying Uranium-series disequilibrium in natural samples for dosimetric dating – Part 1: gamma spectrometry

Dosimetric dating techniques rely on accurate and precise determination of environmental radioactivity. Gamma spectrometry is the method of choice for determining the activity of 238U, 232Th and 40K. With the aim to standardise gamma-spectrometric procedures for the purpose of determining accurate parent nuclide activities in natural samples, we outline here basics of gamma spectrometry and practical laboratory procedures. This includes gamma radiation and instrumentation, sample preparation, finding the suitable measurement geometry and sample size for a given detector and using the most suitable energy peaks in a gamma spectrum. The issue of correct efficiency calibration is highlighted. The procedures outlined are required for estimating contemporary parent nuclide activity. For estimating changing activities during burial specific data analyses are required and these are also highlighted.