Activity concentrations of 226Ra and 228Ra in drilled well water in Finland

The activity concentrations of (226)Ra and (228)Ra in drinking water were determined in water samples from 176 drilled wells. (226)Ra activity concentrations were in the range of <0.01-1.0 Bq l(-1) and (228)Ra activity concentrations in the range of <0.03-0.3 Bq l(-1). The mean activity concentration of (226)Ra and (228)Ra were 0.041 and 0.034 Bq l(-1), respectively. High radium activity concentrations in drinking water were rare. Only 2-4% of the drilled wells exceeded a (226)Ra concentration of 0.5 Bq l(-1) and 1-2% of the wells exceeded a (228)Ra concentration of 0.2 Bq l(-1). These are the activity concentrations that cause a 0.1 mSv annual effective dose for users of drinking water. The maximum annual effective doses from (226)Ra and (228)Ra for users of drilled wells were 0.21 mSv, and 0.16 mSv respectively. The elevated activity concentrations of (226)Ra and (228)Ra did not occur simultaneously in the same groundwaters and the correlation between (226)Ra and (228)Ra was small.     

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

Levels of 22?,22?Ra, 232Th, 21?Pb, 21?Po and ??K 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 (22?Ra), 215±11 Bq kg?1 (21?Pb) and 311±18 Bq kg?1 (21?Po) 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 22?Ra, 21?Pb and 21?Po (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.     

Natural radioactivity in drinking water in private wells in Finland

Radiation Protection Dosimetry     

CMOS on-chip clock for digital signal processors

An on-chip clock for frequencies up to 190 MHz is presented. This clock generator can be used for application specific digital signal processors which are clocked faster than the off-chip system clock. It is useful for both processors with a few cycles per sample or for high frequency bit-serial processors which need a large number of cycles.<>     

Natural radioactivity in drinking water in private wells in Finland

Natural radioactivity in drinking water was determined in population-based random study of 472 private wells. The mean concentrations of (222)Rn, (226)Ra, (234)U, (238)U, (210)Pb and (210)Po in drilled wells were 460, 0.05, 0.35, 0.26, 0.04 and 0.05 Bq l(-1), and in wells dug in the soil were 50, 0.016, 0.02, 0.015, 0.013 and 0.007 Bq l(-1), respectively. Approximately 10% of the drilled wells exceeded a radon concentration of 1000 Bq l(-1) and 18% a uranium concentration of 15 microg l(-1). The mean annual effective dose from natural radionuclides for a drilled well user was 0.4 mSv and 0.05 mSv for a user of a well dug in the soil. The effective dose arising from (222)Rn was 75% of the total of all natural radionuclides for drilled well users. As regards long-lived radionuclides, (210)Po and (210)Pb caused the largest portion of the effective dose. The dose arising from (238)U, (234)U and (226)Ra was only 8% of the total of all natural radionuclides.     

Modeling of glitches due to rise/fall asymmetry in current-steering digital-to-analog converters

The current-steering digital-to-analog converter (DAC) is the most common type of DAC for high-speed applications. Glitches present in the DAC output contribute to nonlinear distortion in the DAC transfer characteristics degrading the circuit performance. One source of glitches is asymmetry in the settling behavior when switching on and off a current source. A behavioral-level model of this nonideal behavior is derived in this work. Further, a method with low computational complexity for estimating the influence of the modeled errors in the frequency domain is developed. This method can be utilized by circuit designers to derive circuit requirements for fulfilling a given frequency-domain specification, potentially relaxing the requirements compared with a worst-case analysis. Examples of model utilization are given in terms of an analytical examination and MATLAB simulations. A good agreement between simulated and analytical results is obtained.     

210Po and 210Pb in the food chain lichen-reindeer-human

The arctic food chain lichen-reindeer-human, transmitting ²¹⁰Po and its precursor ²¹⁰Pb from natural fallout to human, was studied. Lichen, plant, mushroom, and reindeer samples were collected from Finnish Lapland. The ²¹⁰Po and ²¹⁰Pb activity concentrations and the ²¹⁰Po/²¹⁰Pb ratio in these samples were determined. Published in Russian in Radiokhimiya, 2006, Vol. 48, No. 6, pp. 567–568. The text was submitted by the authors in English. Reported at the 7th Russian-Finnish Symposium on Radiochemistry (St. Petersburg, November 2005).     

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).