Pia Vesterbacka

Multidisciplinary analysis of Finnish esker sediment in radon source identification.

In order to define the naturally-occurring radioactive materials that are the source of radon in natural environments, a comprehensive analytical (geochemical, physical and chemical) methodology was employed to study sand samples from the Hollola esker in the city of Hollola (Lahti area, Finland). Techniques such as gamma-spectrometry, emanation measurements, sequential chemical extraction, scanning electron microscopy (SEM), electron probe microanalyses (EPMA) and inductively-coupled plasma mass spectrometry (ICP-MS) were used to determine the potential source of radon. Monazite and xenotime, uranium- and thorium-bearing minerals and potential radon sources, occurred in significant amounts in the samples and were also the main reason for the distribution of uranium and thereby radium in separate grain-size fractions. Following deposition, the esker sand has been exposed to no significant weathering, and radium has not therefore been much separated from uranium. However, considering its non-compatibility with crystal lattices, it was recognized rather in easily leachable species (44% of the total (226)Ra) than uranium (21% of the total (238)U) in our analyses. The smallest grain-size fraction of the esker sand had a higher emanation power (0.24) than the other fractions (around 0.17). Due to the small relative proportion of this fraction, however, it contributed only slightly to the total emanation (4%). The emanation power of the leachable species was about three times higher (ca. 0.20) than that of the species tightly bound to the crystal lattice (ca. 0.07).

Radioactivity levels in some sediment samples from Red Sea and Baltic Sea

Levels of ²²⁶,²²⁸Ra, ²³²Th, ²¹⁰Pb, ²¹⁰Po and ⁴⁰K in sediments from four monitoring areas, El Hamraween and Ras El Behar (Red Sea, Egypt) and LL3A and JML (Baltic Sea, Finland), have been investigated using alpha and gamma spectrometry. The average activity concentrations were 238±4 Bq kg⁻¹ (²²⁶Ra), 215±11 Bq kg⁻¹ (²¹⁰Pb) and 311±18 Bq kg⁻¹ (²¹⁰Po) for El Hamraween area. In Ras El Behar area, the corresponding values were 16±0.4, 18±1 and 20±5 Bq kg⁻¹, respectively. The activity concentrations for ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po (uranium series) in El Hamraween bottom sediment are much high compared with those in Ras El Behar area, which indicates the enhanced levels due to the activities of phosphate mining and shipment operations in El Hamraween area. Excluding the influence of phosphate mining activities, it can be concluded that the levels of radioactivity in Baltic Sea sediments are higher than those in Red Sea sediments.

Towards quality excellence in radioanalytical laboratories at STUK, Finland

Abstract The development of a uniform and modern quality system for the whole of the Finnish Radiation and Nuclear Safety Authority (STUK) began in 1997. The principle of continuous improvement is widely applied by performing annual self-assessments as well as internal and external audits. One of the most important steps in a quality assurance programme is the proficiency of the personnel. Good initiation, non-stop training during work and knowledge of the physical and chemical properties that affect analytical procedures are the requirements for first-rate and motivated working. Working procedures have been planned and followed through in order to prevent any contamination in laboratories. Considerable emphasis has also been placed on the standardisation of uncertainty estimations. This demands good knowledge of the sources of errors in sample preparation, analysis and measurement. Participating in intercomparison exercises and proficiency tests is one way to demonstrate the validity and quality of the methods used. However, a lack of intercomparison exercises and reference material on certain natural radionuclides occurring in waters and certain artificial radionuclides has complicated the validation and proficiency testing of these measurements. Moreover, the arrangement of intercomparisons has not always been optimal.