Uncertainty and detection limits of Pu-241 determination by liquid scintillation counting (LSC)

[EN]Determination of Pu-241 is an essential issue for radiation protection, as it is the precursor of some nuclides with high radiotoxicity. Pu-241 is a low energy beta emitter, which makes its measurement more challenging than that of Pu alpha emitters. The most widely used method for the measurement of Pu-241 is liquid scintillation counting (LSC). In this method, the assessment of Pu radiochemical yield is done by measuring the sample by alpha spectrometry before being lixiviated and measured by LSC. This double measurement affects uncertainty analysis, as well as decision threshold and detection limit, considering that both components of the total yield (radiochemical and lixiviation) should be contemplated. In this paper, and for quality assurance (QA) purposes, in-depth uncertainty and detection limit formulae for the proposed method, controlling correlations and considering all the parameters involved including chemical and lixiviation yields, have been developed. A sensitivity analysis of the uncertainty budget together with an assessment of Pu-242 tracer quantity to be used, ensuring a total yield of at least 50% and a relative uncertainty of the leaching yield of at most 5%, have been carried out. In addition, an analysis of the impact of the real lixiviation yield value and its uncertainty on the results has been done. As a general conclusion, and considering the values of the parameters chosen for this work (samples of 1 g measured for 24 h by LSC), the Pu-241 uncertainties range from 5% to 30% depending on the activity concentration values and the detection limits range from 14 to 30 Bq kg(-1), depending on yield values. The main components of the uncertainty budget are the net Pu-241 and background counts obtained in the LSC measurement for low contaminated samples while this is the case for the alpha gross count rate in LSC measurement of the alpha calibration source for highly contaminated samples. In addition, an analysis of possible interference by Pu alpha emitters in the Pu-241 signal and a comparison of quench standard curves of H-3 and Pu-241 are also performed.Open Access funding provided by University of the Basque Country UPV/EHU

Selectivity analysis of 99Tc determination by LSC in the field of nuclear decommissioning

In this work, two Tc radiochemical isolation methods—a conventional method by Triskem TEVA ® resin and a rapid method by Empore™ Tc Rad Disk—are compared in the field of nuclear decommissioning and 99Tc assessment. The conventional method results more selective than the rapid one, being able to remove almost 100% of the main radiological interferers with the exception of the 90Y; however, the rapid method obtains higher chemical yields (97% vs. 80%) and slightly lower detection limits (0.025 Bq vs. 0.030 Bq) than the conventional. Both methods are similar with regards to equipment and reagent costs.We would like to acknowledge the Open Access funding provided by the University of the Basque Country UPV/EHU

Radiological environmental monitoring of groundwater around NPP: A proposal for its assessment

Whether a nuclear installation has radiological impact and, in that case, its extension, are the questions behind any environmental analysis of the installation along its operational life. This analysis is based on the detailed establishment of the radiological background of the area. Accordingly, the dismantling and decommissioning process (D&D) of a nuclear power plant starts with a radiological monitoring plan, which includes the radiological characterization of the area and of its surroundings. At the completion of the D&D, unrestricted use for the site will be permitted strictly in accordance with results of the radiological survey within the limits established by the local authorities. Groundwater quality is typically included in any radiological analysis since, among other reasons, a significant part of it is highly likely to end up being extracted for domestic use and hence, human consumption. While there is no regulation containing maximum activity concentration or radionuclide guidance values for water that may be destined for uses other than public consumption, if groundwater is considered a “part” of the land, dose criteria for site release can be applied. Therefore, together with the guidance levels to be established for the different radionuclides expected in the groundwater, the detection limits to be employed when performing routine radio analytical characterization procedures in the laboratory should also be provided. In this paper, we first propose a relation of the potential radionuclides to be analyzed in groundwater, together with their detection limits to be achieved when the determinations are performed in a laboratory, and subsequently, we discuss the most suitable analytical methodologies and resources that would be necessary to undertake radiological characterization plans from a practical point of view

Validation and implementation of a method for 226Ra determination by using LSC

A co-precipitation method followed by a liquid–liquid extraction and liquid scintillation counting is validated by applying it to five different types of matrices. In order to test the applicability of the method, complex matrices are selected. This paper shows the implementation and the results of the validation of the method

COVID-19 pandemic impact on the Spanish radiation protection professionals

The pandemic situation, originated due to the appearance of the SARS-CoV-2 virus, changed many aspects of our lives and jobs. This health crisis also affected the day-to-day work of radiation protection experts, including the wide range of areas involved in this sector. This study aimed to evaluate the impact of this pandemic on the Spanish radiation protection experts. For that purpose, a Google Forms online survey was developed with 39 questions. The survey covered different aspects related to the work developed by the Spanish professionals, taking into account three different time periods along the pandemic situation. According to this survey, the appearance of COVID-19 modified the labour conditions and modalities of many Spanish radiation protection professionals, especially at the beginning of the pandemic. Most on-site activities were related to the health sector and the nuclear industry, other sectors were more flexible, and the workload increased for half of the surveyed participants. Many operational activities suffered delays due to the pandemic, whereas the one-month wearing period of passive personal dosimeters was extended in most cases during the first Spanish alarm state (15th March 2020 up to the 21st June 2020). Finally, difficulties faced in terms of the working area have been identified and may be useful for the future.Peer ReviewedPostprint (published version