Amount Of 226Ra Research Articles

Distribution features of <sup>238</sup>U, <sup>232</sup>Th and <sup>226</sup>Ra in bottom sediments of the shelf and continental slope of Svalbard

The features of the distribution of concentrations of238U,232Th and226Ra in the surface layer of bottom sediments in the bottom sediments of the shelf and continental slope of Svalbard are considered. The content of226Ra,232Th, and238U varied in the range 22–134.3, 22.4–50.9, and 10.9–37.7 Bq/kg, respectively. The amount of226Ra nonequilibrium with238U (226Raex) ranged from 23 to 73% of the total226Ra content in sediments. The maximum concentrations of226Ra,238U,232Th and226Raex(134.3, 37.7, 50.9, and 98.2 Bq/kg, respectively) were obtained in the area of increased bioproductivity (Eagle Trough). In this zone, the relationship between the concentrations of226Ra and226Raexwith the content of organic matter in sediment is well expressed, the correlation coefficients areR= 0.94 and 0.92, respectively, which indicates a significant contribution of the biological community to the accumulation of226Ra in bottom sediments. The226Ra concentration and the226Ra excess value are negatively related to the redox potential of the sediment (R= –0.88). This pattern is also true in other areas of the Svalbard waters. In general, for the entire array of observations, the concentrations of238U and232Th increase with increasing content of organic carbon in the sediment (R= 0.72 and 0.7, respectively). The concentrations of238U and232Th decrease with increasing Ccarbcontent in the sediment (R= –0.79 and –0.81, respectively). The data obtained indicate the need to take into account the226Ra excess when assessing the total natural radioactivity of marine sediments, the value of which may exceed the radioactivity of238U and232Th.

Specific Features of the 226Ra, 238U, and 232Th Distribution in the Surface Layer of Marine Sediments under the Conditions of Active Biosedimentation in the Arctic Front Zone

The distribution of natural radionuclides and organic matter in bottom sediments of the active biosedimentation zone on the section drawn through the arctic front of the North Atlantic was studied. The ratios of the amounts of 226Ra, 238U, and 232Th, both deposited in the surface layer of bottom sediments from seawater and supplied with the terrigenic material, were estimated. Direct deposition of radium from water to marine sediments correlates with the organic matter content. The concentration of radium that is not in equilibrium with uranium varies in the range 95–99% of the total content and increases with an increase in the content of chloroform-soluble bitominoid (CB) (R = 0.95). The deposition of nonequilibrium 238U from water to bottom deposits is also significant and ranges from 42 to 69% of the total 238U content. The concentration ratio of nonequilibrium uranium and nonequilibrium radium in the sediments decreases with increasing depth and increases with an increase in the CB content of the deposit. Positive correlation is observed between the content of thorium and total uranium (R = 0.93) and of its nonequilibrium and terrigenic fractions (R = 0.93 and 0.94, respectively).

Influence of High Total Dissolved Solids Concentration and Ionic Composition on γ Spectroscopy Radium Measurements of Oil and Gas-Produced Water.

Radium measurements in high total dissolved solids (TDS) fluids from oil and gas extraction can have unfavorable precision and accuracy, in part because these high-level impurities incur attenuation. γ spectroscopy is often recommended for determining radium activities in these fluids, but even this method can produce a range of reported activities for the same sample. To reduce measurement duration and to maintain or improve accuracy, we propose a method to rapidly assess both 226Ra and 228Ra and to account for the self-attenuation of γ rays in high-TDS oil and gas fluids when they are monitored by a well detector. In this work, comparisons between a NaCl-only and a multi-cation-chloride synthetic brine spiked with known amounts of 226Ra and 228Ra indicated that both the TDS concentration and the type of TDS (i.e., Na only vs Na-Mg-Ba-Ca-Sr) influenced self-attenuation in well-detector γ spectroscopy, thus highlighting the need to correct for this TDS-influenced self-attenuation. Radium activities can be underestimated if the correction is not applied. For instance, 226Ra activities could be ∼40% lower in a sample when measured directly at the 186 keV energy level if the attenuation of the high TDS of the fluid is not considered. We also showed that using a NaCl-only brine to match the matrix of high-TDS oil and gas brines is inadequate to produce accurate measurements, rather, the full set of cations should be included.

226Ra measurements through gamma spectrometric counting of radon progenies: How significant is the loss of radon?

Most determinations of 226Ra are based on gamma spectrometric measurements of 226Ra progenies 214Pb and 214Bi. This approach assumes radioactive equilibrium between these radionuclides which is normally achieved by sealing the sample containers so that the direct decay product of 226Ra, 222Rn, is not lost. We investigated to what extent 222Rn is lost from various sample containers usually used for gamma spectrometric measurements and which have been sealed applying different techniques. The sample containers containing reference material with known amounts of 226Ra were placed in an air-tight measurement chamber and we measured the 222Rn accumulation over time in the chamber. Taking the leakage of the experimental set-up into account, we related the measured 222Rn to the 226Ra content of the reference material to calculate the 222Rn loss from the sample containers. For most of the reference materials investigated the sealing techniques applied reduced the 222Rn loss to <6%. We found that BaSO4 sample matrix and plastic containers sealed with epoxy resin most effectively minimize the 222Rn loss (<1%). For those sample matrixes like phosphogypsum and Mn-fibers, which are characterized by high emanation and diffusion of radon, sealing is very important to reduce the 222Rn loss.

Validation of &amp;lt;sup&amp;gt;226&amp;lt;/sup&amp;gt;Ra and &amp;lt;sup&amp;gt;228&amp;lt;/sup&amp;gt;Ra Measurements in Water Samples Using Gamma Spectrometric Analysis

Radium isotopes can be analyzed by different analytical methods based on gamma spectrometric measurements or alpha spectrometry. An improved method was developed to determine radium isotopes from water using gamma spectrometry after radiochemical separation. The Radium was selectively extracted from acidified samples using co-precipitation procedure with iron hydroxide and followed by precipitation of radium as radium sulphate Ba(Ra)SO4. The precipitate Ba(Ra)SO4 was filtered through the Millipore filter paper, dried and weighed to calculate chemical yield. 226Ra and 228Ra activities were measured using low-background gamma spectrometry in water samples. Radium was pre-concentrated from environmental samples by co-precipitation with BaSO4. The amounts of 226Ra and 228Ra on the sample were obtained by gamma-ray spectrometry for the 351 keVγ-ray from 214Pb and for the 911 keV γ-ray from 228Ac, both in radioactive equilibrium with precursors, respectively. The accuracy, selectivity, traceability, applicability and Minimum Detectable Activity (MDA) of the technique were discussed. Also, the effect of physical and chemical characteristics of the water samples such as TDS, pH, soluble species, sulphate and bicarbonate that effect on the radium determination were taking into consideration. The method has been validated with a certified reference material supplied by the International Atomic Energy Agency and reliable results were obtained. The radiochemical yields for radium were 70% - 90% and recovery was 97% and 80% for 226Ra and 228Ra, respectively.

NATURAL RADIOACTIVITY IN DRINKING WATER OF DRILLED WELLS IN ZANJAN, NORTHWESTERN IRAN

Background: Many radioactive compounds may be released into the environment and hence into the drinking water supplies due to the human activities. Radionuclides can also enter the food chain if the contaminated water is used for drinking or irrigation purposes. Objective: To estimate the annual effective dose of natural radioactive materials like 226Ra and 40K in drinking water of wells in Zanjan, nortwestern Iran. Methods: 82% of drinking water in Zanjan comes from drilled wells. Water samples from the main sites of drinking water from different parts of Zanjan were collected. The amount of 226Ra and 40K were measured by gamma-ray spectrometry using a NaI (Tl) detector. The annual effective dose of the radioactive materials was calculated for children (2–7 years old) and adults (≥17 years old) with annual water intake of 350 and 500 L, respectively. The annual effective dose received by residents of the city due to consumption of the contaminated drinking water was also calculated. Results: The mean±SD concentrations of 226Ra and 40K were 32.4±7.8 and 20.5±27.4 Bq/L, respectively. The mean±SD annual effective dose received by residents of the city due to consumption of the contaminated drinking water was 7.13±1.76 and 4.59±1.12 mSv/y for children and adults, respectively. Conclusion: The level of radioactive compounds in water of drilled wells in Zanjan is significantly higher than the ICRP permissible limit of 1 mSv/y.

Life exposure to 226Ra and possible consequences

This paper presents a model of continuous exposure to 226Ra by water consumption over a 55-year period. The effects of 226Ra concentration in drinking water were investigated. Reaching the peak at the age of 16, the assessed effective dose has shown that children are more sensitive to radiation than adults. It has been found that consumption of 226Ra–rich water during certain period of life increases consequent effective doses. The earlier the exposure, the higher amount of 226Ra could be retained causing the higher values of effective dose later in life. However, long-term exposure to 226Ra in drinking water as well as consumption of 226Ra-rich water during a certain period of life does not indicate the appearance of malignant diseases in the year of exposure and later in adults.

Conditioning and long-term storage of spent radium sources in Turkey

Conditioning of radium sources is required before long-term interim storage to avoid the release of radioactive material and to limit radiation exposure. In this study, containment of the radium sources was achieved by high integrity encapsulation designed to control the radon emanation problem. The capsules were made of Type 316 austenitic stainless steel with dimensions of 22 mm diameter and 160 mm height. The gas pressures which was caused by encapsulation of different amounts of 226Ra were determined. The maximum gas pressure found 10 atm for 900 mCi of 226Ra in one capsule at 20 °C. A lead shielding device was designed to limit radiation exposure. A 200 l drum was used as a conditioned waste package for the radium sources and represents a Type A package under the IAEA transport regulations.

Transport of U- and Th-Series Radionuclides in Groundwater

The purpose of this study is to understand the behaviour of the actinides in groundwater by combining data on the distribution of both longlived and short-lived nuclides of the U and Th decay series in an aquifer with a model for the nuclide transport along aquifer flow lines. The groundwater concentrations of the short-lived nuclides, such as 222Rn, 224Ra and 234Th, provide information only on local aquifer conditions, while the concentrations of the long-lived nuclides reflect geochemical processes along extended flow paths. In an important study, Krishnaswami et al. (1982) calculated sorption rate constants for many of the decay series nuclides in an aquifer using a batch model. However, no study yet has combined the data provided by both long and short-lived radionuclides to study the transport mechanisms along a flow line. Furthermore, although colloidal phases have been found to be important carriers of U and Th in numerous natural aqueous systems, very few investigations have been conducted on their importance in the transport of naturally-occurring actinides in groundwater. The aquifer investigated here is the sandy unconfined Upper Glacial Pleistocene aquifer situated in Long Island, NY. Extensive information regarding the geology and the hydrology of the aquifer is available and numerous high quality and well-documented wells are available for sample collection. This aquifer is underlain by a discontinuous layer of impermeable clay, below which is a sandy confined aquifer, the Magothy, where reducing conditions prevail. Radionuclide data from several wells in this aquifer have been reported by Copenhaver et al. (1993). Samples from the Upper Glacial aquifer have been taken along two flow lines at three different depths and filtered through 0.45 gm filter cartridges. In addition, cross-flow ultrafiltration has been used to separate colloids >10 kD from ultrafiltered water that represents the dissolved load. This technique, described in previous papers, has proven to be successful in studying the association of uranium and other elements with colloids (e.g. Porcelli et al., 1997). The concentrations of the long-lived radionuclides :3SU, 234U and 23eTh have been measured by thermal ionization mass spectrometry and the short-lived radiogenic daughters 222Rn, 226Ra, 228Ra, 224Ra, 234Th by counting methods. In addition, the water samples have been analysed for pH and conductivity in the field, and for concentrations of major cations, anions and trace elements. Water samples from the Upper Glacial aquifer have pH values of 5.4 to 6.5 and TDS (Total Dissolved Solid) of 20 to 100 mg/l. The high Mn concentration in a deep sample of the shallow aquifer likely indicates a difference in redox conditions. The Magothy aquifer has TDS o f 50 mg/1, comparable to that of the unconfined aquifer, but much higher Fe and Mn concentrations. The 222Rn activities generally full within a restricted range throughout the Upper Glacial aquifer of 65 to 170 dpm/kg, with two peak values of 3 36 and 522 dprn/kg. The amount of Rn in the water represents -4 % of the Rn produced in the rock by decay. Assuming that the aquifer rock consists of solid spherical grains with uniform distribution of Ra, this amount of Rn can only be supplied by grains of ~ 0.1 ~tm in size and therefore cannot be produced by the aquifer which average grain size is ~1 mm. This has been observed previously (e.g. Copenhaver et al., 1993). High Rn concentrations have been observed and lead to the requirement that Rn is circulating through nanopores or that the source of Rn is on the surface. We observe that the dissolved Rn concentration is generally greater where the dissolved 226Ra concentration is lower, suggesting that higher Rn concentrations in the water are due to increased amounts of 226Ra on aquifer surfaces due to deposition of dissolved 226Ra. Therefore we infer that Rn concentrations here are controlled by the distribution of Ra on surfaces rather than by enhanced release from

226Ra induced bone-cancers: the effects of a delayed Na-alginate treatment.

At the present time no unequivocal evidence exists which shows that a reduction in the body-burden of a radionuclide by decorporative treatment results in a proportional decrease in the risk of long-term radiation effects. We have investigated the effectiveness of the daily administration of Na-alginate via the diet in removing 226Ra from the skeleton and in reducing the number of late effects such as osteosarcomas. The animals used were male C57Bl mice which had been injected with one of three different amounts of 226Ra (4.4, 10.7 or 24.8 kBq) four days prior to the onset of the decorporative treatment. The results showed that although this treatment was able to produce a substantial reduction in the 226Ra content of the mice it did not reduce the incidence of osteosarcoma. These results question the effectiveness of decorporation procedures initiated at longer times after contamination.

Dose delivered to various bone and marrow sites of radium 226 injected mice related to the observed heterogeneity in damage to haemopoietic marrow cells.

A method of determining local radiation doses from 226Ra to selected bone marrow sites of 226Ra-injected mice is presented. The 226Ra burden in selected cortical and trabecular bone sites of BALB/c mice and the morphometric characteristics of these bone sites and of their marrow cavities in BALB/c mice are measured. These data, along with information on dosimetry from the literature, are used to calculate the cumulative dose in the selected bone and marrow cavity sites. The amount of 226Ra picked up by a bone is shown to be linearly related to the area of bone surface. The energy absorption in various bone and bone marrow sites is not homogeneous. The relationship between local marrow doses and the observed non-uniformity in damage to haemopoietic marrow cells of different marrow sites 300 days after 226Ra injection is discussed. The degree of marrow damage does not simply reflect the calculated marrow dose. This dose-effect study gives some indications for (1) a modification of the approach used in local 226Ra dosimetry and (2) additional damage to the stem cells due to irradiation of their regulating system.