Radionuclide Composition Research Articles

Measurement of Volatile Radionuclides Production and Release Yields followed by a Post-Irradiation Analysis of a Pb/Bi Filled Ta Target at ISOLDE

A crucial requirement in the development of liquid-metal spallation neutron target is knowledge of the composition and amount of volatile radionuclides that are released from the target during operation. It is also important to know the total amount produced, which could be released if there was an accident. One type is the lead-bismuth eutectic (LBE) target where different radionuclides can be produced following interaction with a high-energy proton beam, notably noble gases (Ar, Kr, Xe isotopes) and other relative volatile isotopes such as Hg and At. The results of an irradiation experiment performed at ISOLDE on a LBE target are compared with predictions from the MCNPX code using the latest developments on the Liège Intranuclear Cascade model (INCL4.6) and the CEM03 model. The calculations are able to reproduce the mass distribution of the radioisotopes produced, including the At production, where there is a significant contribution from secondary reactions. Subsequently, a post-irradiation examination of the irradiated target was performed. Investigations of both the tantalum target structure, in particular the beam window, and the lead-bismuth eutectic were performed using several experimental techniques. No sign of severe irradiation damage, previously observed in other ISOLDE targets, was found.

Comparative Effi ciency of Countermeasures in Agriculture at the Radionuclide-Contaminated Territories

The effi ciency of various countermeasures (radioprotective measures) in agricultural production at the radionuclide-contaminated territories after the radiation accidents in the South Ural, at the Chernobyl NPP and NPP Fukushima I are compared. The infl uence of these accidents on the decreasing of radionuclides uptake and accumulation in plant-breading and animal-breeding products, and consequently, on internal radiation dose for the human being due to foodstuffs varies in different conditions and mainly depends on radionuclide composition of contamination, soil type and manufacturing profi le of production.

Radiochemical characterization of mineral waters for a European interlaboratory comparison

The objective of this work was to select waters as realistic test items for an interlaboratory comparison on gross alpha/beta measurement in drinking waters. For this reason, a preliminary radioanalytical survey studying the naturally occurring alpha emitting radionuclides was carried out in 11 popular and regularly consumed mineral waters from the European market. The activity concentrations of the main naturally occurring alpha-emitting radionuclides (226Ra, 210Po, 234U, 235U, 238U and 228Th) were determined by using alpha spectrometry after separation from the matrix elements. Additionally, the committed effective dose was also estimated from the water consumption. Average activity concentrations of radionuclides in the mineral waters were in the following order: 226Ra>234U>238U>210Po>228Th>235U. The estimated committed effective doses for the analyzed mineral water samples are in the range 2.5–134.2μSv a−1 with an average 41.5μSv a−1, which is well below 100μSv a−1, the total indicative dose recommended by EC/WHO for drinking water (excluding mineral waters). Only one mineral water sample did not meet this requirement, its constant consumption would result in a dose higher than 100μSv a−1, mainly due to the contribution of 226Ra and 210Po. Apart from the main radiological characteristics of the analyzed waters, this study provides additional information for consumers and authorities about the potential internal exposure risk from mineral water intake. Based on the radionuclide composition and the total dissolved solids of the mineral waters two candidates were selected as potential test items for an interlaboratory comparison exercise.

Investigation of Radionuclide Sorption on Peat

Organic sorbents like peat can be successfully used for the purification of radioactive waste waters and are favoured by economical and technical considerations. The peat filters are also friendlier to the environment, since the manufacturing of such filters is a low emission process. This study examined the sorption of radionuclides 137Cs, 55Fe, 63Ni and 14C on peat samples. The initial radioactivity of the peat samples was studied before the experiments. Peat samples were taken from different bogs. Radionuclide solutions were prepared using deionised water and appropriate radionuclide composition from the Salaspils research reactor stock water. It was found that in all cases of peat samples, the main natural radionuclides were 210Pb, 40K and 214Bi. The artificial radionuclides 152Eu, 137Cs and 60Co were also found in the peat samples. Radionuclide sorption studies indicated that the initial radioactivity of the solution decreased in the case of radionuclides 63Ni, 14C, 55Fe and 137Cs. This confirmed that peat samples can effectively remove the radionuclides from radioactive water solutions.

Reconstruction of the contamination of the Techa River in 1949–1951 as a result of releases from the “MAYAK” Production Association

More accurate reconstruction of the radioactive contamination of the Techa River system in 1949-1951 has been made on the basis of refined data on the amounts and the rate of discharge of radionuclides into the Techa River from the Mayak Production Association; this has led to the development of a modified Techa River model that describes the transport of radionuclides through the up-river ponds and along the Techa River and deposition of radionuclides in the river-bottom sediments and flooded areas. The refined Techa River source-term data define more precisely the time-dependent rates of release and radionuclide composition of the releases that occurred during 1949-1951. The Techa River model takes into account the time-dependent characteristics of the releases and considers (a) the transport of radionuclides adsorbed on solid particles originally contained in the discharges or originating in the up-river ponds as a result of stirring up of contaminated bottom sediments and (b) the transport of radionuclides in soluble form. The output of the Techa River model provides concentrations of all source-term radionuclides in the river water, bottom sediments, and floodplain soils at different distances from the site of radioactive releases for the period of major contamination in 1950-1951. The outputs of the model show good agreement with historical measurements of water and sediment contamination. In addition, the river-model output for (90)Sr concentration in the river water is harmonized with retrospective estimates derived from the measurements of (90)Sr in the residents of the Techa Riverside villages. Modeled contamination of the floodplain soils by (137)Cs is shown to be in agreement with the values reconstructed from late measurements of this radionuclide. Reconstructed estimates of the Techa River contamination are being used for the quantification of internal and external doses received by residents of the Techa Riverside communities.

Artificial and natural radioactivity in edible mushrooms from Sao Paulo, Brazil

Environmental biomonitoring has demonstrated that organisms such as crustaceans, fish and mushrooms are useful to evaluate and monitor both ecosystem contamination and quality. Particularly, some mushroom species have a high capacity to retain radionuclides and some toxic elements from the soil and the air. The potential of mushrooms to accumulate radionuclides in their fruit-bodies has been well documented. However, there are no studies that determine natural and artificial radionuclide composition in edible mushrooms, in Brazil. Artificial (137Cs) and natural radioactivity (40K, 226Ra, 228Ra) were determined in 17 mushroom samples from 3 commercialized edible mushroom species. The edible mushrooms collected were Agaricus sp., Pleurotus sp. and Lentinula sp. species. The activity measurements were carried out by gamma spectrometry. The levels of 137Cs varied from 1.45 ± 0.04 to 10.6 ± 0.3Bqkg−1, 40K levels varied from 461±2 to 1535 ± 10Bqkg−1, 226Ra levels varied from 14 ± 3 to 66 ± 12Bqkg−1 and 228Ra levels varied from 6.2 ± 0.2 to 54.2 ± 1.7Bqkg−1. 137Cs levels in Brazilian mushrooms are in accordance with the radioactive fallout in the Southern Hemisphere. The artificial and natural activities determined in this study were found to be below the maximum permissible levels as established by national legislation. Thus, these mushroom species can be normally consumed by the population without any apparent risks to human health.

Qualitative Assessment of Sources and General Dependencies in the Behavior of Anthropogenic Radionuclides in the Techa River

Research on radioactive contamination of the environment involves the important task of assessing the contribution from different sources of contamination. If there are two or more sources of contamination with similar radionuclide composition, assessment of the contribution from each source can be challenging. Such a problem exists, for instance, in the assessment of anthropogenic sources of radioactive contamination of water in the Techa River. At the present time, the main contaminating radionuclides for the Techa River are 90Sr, 137Cs, and 3H. In 2009-2010, the content of radionuclides in the water of the river was 90Sr-3.8-32.9 Bq L, 137Cs-0.02-2.43 Bq L, and 3H-31.0-263.2 Bq L. This work gives a qualitative assessment of the role of different contamination sources in the formation of volumetric activity of Sr in the water of the Techa River. Also, the behavior of anthropogenic radionuclides in the open fluvial river system is reviewed.

Determination of the radionuclide composition and burn-up of high-burn-up WWER-1000 fuel by destructive methods

A sample of WWER-1000 spent nuclear fuel (SNF) with the burn-up of approximately 50 GW day (t U)−1 was studied by methods of destructive analysis. Data on the content of isotopes of U, Pu, Am, Cm, Nd, and Cs are given. The methods used are briefly described. These include anion exchange and extraction chromatography, thermal ionization mass spectrometry, luminescence analysis, and γ- and α-ray spectrometry. The main method of the study is isotope dilution followed by mass-spectrometric analysis. The data obtained will be used for developing of a low-waste and low-cost technology for preprocessing of highburn-up SNF and also for checking the accuracy of calculation of heavy actinide content in SNF and for improving computation methods and programs intended for calculation of the SNF nuclide composition in relation to the fuel burn-up in WWER-type reactors. The Nd and Cs isotopes were used as burn-up monitors.

Migration of transuranic elements in groundwater from the near-surface radioactive waste site

► Plutonium isotopes spatial distribution in unconfined aquifer near shallow waste dump. ► We found that plutonium in aquifer was originated from the dump. ► Pu mobility in waste and aquifer is characterized by in situ partition coefficients. ► Pu in groundwater is associated mainly with low molecular weight species (<1 kDa). Field experiments and laboratory studies were performed to investigate migration processes of plutonium isotopes from a near-surface radioactive waste trench to the underlying sandy aquifer at the Red Forest waste dump in the Chernobyl zone. The objectives of these experiments were to characterize the spatial distribution and possible migration mechanisms of plutonium in the aquifer. During 2002–2007 experimental investigations were carried out and spatial distributions of plutonium isotopes ( 239 , 240 Pu, 238 Pu), 90 Sr and major ions in the aquifer in the direction of the groundwater flow were obtained. Specific activities of radionuclides in groundwater depended on the location of the piezometer and varied in the range of 1–360 mBq kg −1 for 239 , 240 Pu, 0.5–180 mBq kg −1 for 238 Pu and n–n·10 4 Bq kg −1 for 90 Sr. It was found that the spatial features of the distributions of plutonium and strontium specific activities in the upper eolian aquifer were similar, i.e. there was a correlation between the positions of the activity maxima of the radionuclides. The Pu isotopes plume in the aquifer spreads about 15 m downstream of the radionuclides source. Characterization of the initial radionuclide composition of the waste showed that all plutonium in the aquifer originated from the trench. The ratio of plutonium isotopes ( 239 , 240 Pu/ 238 Pu) at the sampling time was the same in waste material and in groundwater samples. In situ ultrafiltration of several groundwater samples was carried out. The size fractionation data obtained suggest that a significant part of plutonium (50–98%) in the groundwater sampled close to the source from the upper part of the aquifer is associated with a very low molecular weight fraction (<1 kDa).

REEVALUATION OF WATERBORNE RELEASES OF RADIOACTIVE MATERIALS FROM THE MAYAK PRODUCTION ASSOCIATION INTO THE TECHA RIVER IN 1949–1951

The Mayak Production Association was the first site for the production of weapons-grade plutonium in Russia. Early operations led to the waterborne release of radioactive materials into the small Techa River. Residents living downstream used river water for drinking and other purposes. The releases and subsequent flooding resulted in deposition of sediments along the shoreline and on floodplain soil. Primary routes of exposure were external dose from the deposited sediments and ingestion of 90Sr and other radionuclides. Study of the Techa River Cohort has revealed an increased incidence of leukemia and solid cancers. Epidemiologic studies are supported by extensive dose-reconstruction activities that have led to various versions of a Techa River Dosimetry System (TRDS). The correctness of the TRDS has been challenged by the allegation that releases of short-lived radionuclides were much larger than those used in the TRDS. Although the dosimetry system depends more upon measurements of 90Sr in humans and additional measurements of radionuclides and of exposure rates in the environment, a major activity has been undertaken to define more precisely the time-dependent rates of release and their radionuclide composition. The major releases occurred during 1950-1951 in the form of routine releases and major accidental releases. The reevaluated amount of total release is 114 PBq, about half of which was from accidents that occurred in late 1951. The time-dependent composition of the radionuclides released has also been reevaluated. The improved understanding presented in this paper is possible because of access to many documents not previously available.

Keeping an eye on the ring: COMS plaque loading optimization for improved dose conformity and homogeneity.

PurposeTo improve tumor dose conformity and homogeneity for COMS plaque brachytherapy by investigating the dosimetric effects of varying component source ring radionuclides and source strengths.Material and methodsThe MCNP5 Monte Carlo (MC) radiation transport code was used to simulate plaque heterogeneity-corrected dose distributions for individually-activated source rings of 14, 16 and 18 mm diameter COMS plaques, populated with 103Pd, 125I and 131Cs sources. Ellipsoidal tumors were contoured for each plaque size and MATLAB programming was developed to generate tumor dose distributions for all possible ring weighting and radionuclide permutations for a given plaque size and source strength resolution, assuming a 75 Gy apical prescription dose. These dose distributions were analyzed for conformity and homogeneity and compared to reference dose distributions from uniformly-loaded 125I plaques. The most conformal and homogeneous dose distributions were reproduced within a reference eye environment to assess organ-at-risk (OAR) doses in the Pinnacle3 treatment planning system (TPS). The gamma-index analysis method was used to quantitatively compare MC and TPS-generated dose distributions.ResultsConcentrating > 97% of the total source strength in a single or pair of central 103Pd seeds produced the most conformal dose distributions, with tumor basal doses a factor of 2-3 higher and OAR doses a factor of 2-3 lower than those of corresponding uniformly-loaded 125I plaques. Concentrating 82-86% of the total source strength in peripherally-loaded 131Cs seeds produced the most homogeneous dose distributions, with tumor basal doses 17-25% lower and OAR doses typically 20% higher than those of corresponding uniformly-loaded 125I plaques. Gamma-index analysis found > 99% agreement between MC and TPS dose distributions.ConclusionsA method was developed to select intra-plaque ring radionuclide compositions and source strengths to deliver more conformal and homogeneous tumor dose distributions than uniformly-loaded 125I plaques. This method may support coordinated investigations of an appropriate clinical target for eye plaque brachytherapy.

Radionuclide composition of fragments of lava-like fuel-containing materials from the CNPP fourth unit

Samples of fuel-containing materials taken inside the CNPP Fourth Unit were analyzed by γ- and α-ray spectrometry. The isotope ratios for Cs, Eu, Pu, Am, and Cm were measured, and the fuel burn-up in the samples was determined. Inconsistencies in theoretical estimations on the production of all the radionuclides over 241Am were revealed. The burn-up values determined from data on the Cs isotopes systematically differ from those determined from data on the other radionuclides. The causes of these facts are discussed.

Activity determination without tracers in high-resolution alpha-particle spectrometry

High-resolution alpha spectrometry was applied for the activity determination of 10 reference sources containing different amounts of 238Pu, 239Pu, 240Pu and 242Pu. They were analyzed as blind sources using a novel spectrum analysis tool ADAM. The information needed in the spectrum unfolding was taken only from the spectrum under investigation, and no tracers were applied. Therefore, a Monte Carlo program AASI was used to compute geometrical detection efficiency of the measurement setup. All reported activities corresponded to those of the reference sources within expanded uncertainty. The developed tools can be used for the activity determination in nondestructive alpha spectrometry or when the radionuclide composition does not change during the sample processing.

Change of the Asian dust source region deduced from the composition of anthropogenic radionuclides in surface soil in Mongolia

Abstract. Recent climate change, especially during the 2000s, may be the primary reason for the expansion of the Asian dust source region. The change in the dust source region was investigated by examining anthropogenic radionuclides contained in surface soil samples from Mongolia. Surface soil was globally labeled by radioactive fallout from nuclear testing during the late 1950s and early 1960s, but there are no current direct sources for anthropogenic radionuclides in the air (before the Fukushima nuclear power plant accident in 2011). Radionuclides in the atmosphere are therefore carried mainly by wind-blown dust from surface soil, that is, aeolian dust. Asian dust carries traces of 90Sr, 137Cs, and other anthropogenic radionuclides; the heaviest deposition occurs in spring and has been recorded in Japan since the early 1990s. The composition of anthropogenic radionuclides in atmospheric depositions would be affected by a change in the dust source. Previous studies of atmospheric deposition at long-term monitoring sites (e.g. in Tsukuba, Japan) have detected changes in the 137Cs/90Sr ratio and in the specific activity of the radionuclides. These changes in the composition of observed atmospheric depositions are supposed to reflect changes in the climatic conditions of the dust source region. To investigate this dust source change, we conducted a field survey of radionuclides (90Sr and 137Cs) in surface soil samples in September 2007 in the eastern and southern regions of Mongolia, where dust storms have occurred more frequently since 2000. The specific activities of both radionuclides as well as the 137Cs/90Sr ratio in the surface soil were well correlated with annual average precipitation in the Mongolian desert-steppe zone. Higher specific activities and a higher 137Cs/90Sr ratio were found in grassland regions that experienced greater precipitation. These findings suggest that the increased specific activities and the activity ratio detected in atmospheric depositions in Japan during years with frequent Asian dust transport events in the 2000s are a sign of grassland degradation.

10.1007/s11983-008-1005-2

Radionuclide composition of soils near craters produced by excavation explosions “1003” and “1004” in 1965 at the Semipalatinsk test site is characterized as of 2005. A conclusion is made that radionuclides 137Cs, 152Eu, 154Eu, 155Eu, 241Am, and 60Co do not penetrate deeper than the upper 2 cm of the chestnut solonetz-like soil. The patterns after the explosions studied can be traced over the terrain near the crater ejecta to present. Contamination levels rapidly decrease with the distance from the ground zero. It is demonstrated that technogenic soils in the region of nuclear tests in a dry-steppe zone can be a source of dust and secondary air contamination.

Radiochemical analysis of potable water from some underground sources of Leningrad oblast

Of the two existing radiochemical procedures for determining the isotope composition and specific activities of radionuclides in potable water (the first procedure was developed at the Center for Examining Water Quality and the second, at the Ramzaev Research Institute of Radiation Hygiene), the second procedure is more reliable. It was used for total radiochemical analysis of water from a series of underground artesian wells of north-western regions of Leningrad oblast.

The effect of physicochemical parameters on the separation recovery of plutonium and uranium from aqueous solutions by cation exchange

The effect of physicochemical parameters such as pH, salinity (e.g. [NaCl]) and competitive cation (e.g. Ca2+ and Fe3+) concentration on the separation recovery of plutonium and uranium from aqueous solutions by cation exchange has been investigated. The investigation was performed to evaluate the applicability of cation exchange as separation and pre-concentration method prior to the radiometric analysis of uranium and plutonium isotopes in natural water samples. Application of the method to test solutions of constant radionuclide concentration and variable composition (0.1, 0.5 and 1 M NaCl; 0.1 and 0.5 M Ca(NO3)2; 0.1 and 1 mM FeCl3; 10) has generally shown that: (1) the optimum pH is 4.5 for uranium and plutonium, (2) increasing salinity results in slightly lower for uranium and significantly higher chemical recovery plutonium and (3) the presence of Ca(II) cations doesn’t significantly affect the chemical recovery of both radionuclides. Contrary, the presence of Fe(III) cations ([Fe(III)] > 0.1 mM) results in significantly lower chemical recovery for both radionuclides (<50%). The later is attributed to the formation of Fe(III) colloids, which present increased chemical affinity for uranium and plutonium and hence compete with the radionuclide binding by the resin. Nevertheless, the results indicate that the method could be successfully applied to a wide range of natural waters.

DOSES FROM EXTERNAL IRRADIATION TO MARSHALL ISLANDERS FROM BIKINI AND ENEWETAK NUCLEAR WEAPONS TESTS

Annual doses from external irradiation resulting from exposure to fallout from the 65 atmospheric nuclear weapons tests conducted in the Marshall Islands at Bikini and Enewetak between 1946 and 1958 have been estimated for the first time for Marshallese living on all inhabited atolls. All tests that deposited fallout on any of the 23 inhabited atolls or separate reef islands have been considered. The methodology used to estimate the radiation doses at the inhabited atolls is based on test- and location-specific radiation survey data, deposition density estimates of 137Cs, and fallout times-of-arrival provided in a companion paper (Beck et al.), combined with information on the radionuclide composition of the fallout at various times after each test. These estimates of doses from external irradiation have been combined with corresponding estimates of doses from internal irradiation, given in a companion paper (Simon et al.), to assess the cancer risks among the Marshallese population (Land et al.) resulting from exposure to radiation from the nuclear weapons tests.

Identification and characterisation of radioactive particles in salt marsh sediments

Radionuclides from authorized low level radioactive effluent discharges from the nuclear fuel reprocessing plant at Sellafield, UK, are present in the Irish Sea sediments. The distribution of radionuclides in salt marsh sediment profiles can be related to the discharge history from Sellafield. Radioactive particles, from the intertidal salt marsh sediments in the Esk estuary (10 km from Sellafield), have been isolated and investigated. Autoradiography and heavy liquid density separation were used to find and isolate these particles. Scanning electron microscopy, combined with energy dispersive X-ray analysis (SEM-EDX), was used to obtain information on the morphology and elemental composition of the particles, and alpha spectrometry for radionuclide composition. Particles are typically 1 — 20 μm size. Elemental analysis suggests that they are composed mainly of uranium. Alpha spectrometry shows that they have been irradiated, and transuranium nuclides (Pu, Am, Cm) can be identified in them.

Guidance on monitoring and data assimilation

Decision makers must react in a prompt and appropriate manner in various emergency situations. The bases for decisions are often predictions produced with decision support systems (DSS). Actual radiation measurement data can be used to improve the reliability of the predictions. Data assimilation is an important link between model calculations and measurements and thus decreases the overall uncertainty of the DSS predictions. However, different aspects have to be taken into account for the optimal use of the data assimilation technique: different countries may have differing measurement strategies and systems as well as differing calculation models. The scenario and the amount and composition of radionuclides released may vary. In this paper we analyse the situation during and after an accident and draw up a list of recommendations that can help modellers to take into account the measurements that are best suited for data assimilation.