Concentration Of 99Tc Research Articles

Online Solid-Phase Extraction-Inductively Coupled Plasma-Quadrupole Mass Spectrometry with Oxygen Dynamic Reaction for Quantification of Technetium-99.

Quantification of pg/L levels (i.e., 0.6 mBq/L) of radioactive technetium-99 (99Tc) was achieved within 15 min in the presence of isobaric and polyatomic interference sources such as ruthenium-99 (99Ru) and molybdenum hydride (98Mo1H) at 3–11 orders of magnitude higher concentrations. Online solid-phase extraction–inductively coupled plasma–quadrupole mass spectrometry (ICP–QMS) with oxygen (O2) dynamic reaction cell (online SPE–ICP–MS–DRC) was shown to be a thorough automatic analytical system, circumventing the need for human handling. At three stepwise separations (SPE–DRC–Q mass filters), we showed that interference materials allowed the coexistence of abundance ratios of 1.5 × 10–13 and 1.1 × 10–5 for 99Tc/Mo and 99Tc/Ru, respectively. A classical mathematical correction using the natural isotope ratio of 99Ru/102Ru was used to calculate the residues of 99Ru. Using this optimized system, a detection limit (DL; 3σ) of 99Tc was 9.3 pg/L (= 5.9 mBq/L) for a 50 mL injection and sequential measurements were undertaken at a cycle of 24 min/sample. For the measurement of a lower concentration of 99Tc, an AG1-X8 anion-exchange column was used to study 20 L of seawater. Its DL was approximately 1000 times greater than that of previous methods (70.0 fg/L). Thus, this method withstands coexistences of 5.8 × 10–18 and 3.5 × 10–9 for 99Tc/Mo and 99Tc/Ru, respectively. Spike and recovery tests were conducted for environmental samples; the resulting values showed good agreement with the spike applied.

Iron phosphate glass for immobilization of 99Tc

Technetium-99 (99Tc) can bring serious environmental threats because of its long half-life (τ1/2=∼2.1×105 years), high fission yield (∼6%), and high solubility and mobility in the ground water. The high volatility makes it difficult to immobilize 99Tc in continuous melters vitrifying 99Tc-containing nuclear wastes in borosilicate glasses. This work explores a possibility of incorporating a high concentration of 99Tc, surrogated by the non-radioactive Re, in an iron phosphate glass by melting mixtures of iron phosphate glass frits with 1.5–6mass% KReO4 at ∼1000°C. The retention of Re achieved was ∼1.1mass%. The normalized Re release by the 7-day Product Consistency Test was <10−2g/m2. Surprisingly, the Re escaped from the melt within a short time of heating, especially when the temperature was increased. Therefore, 99Tc volatilization would still be a challenging task for its immobilization in iron phosphate glasses.

Seasonal variation of technetium-99 in Fucus vesiculosus and its application as an oceanographic tracer

The concentration of 99Tc was determined in archived time series seaweed samples collected at Klint (Denmark). The results demonstrate a significantly seasonal variation of 99Tc concentrations in Fucus vesiculosus with maximum values in winter and minimum values in summer. The mechanism driving this seasonal cycle was explored. With the measured 99Tc concentration in seawater collected in the same location and date as for seaweed, the concentration factor of F. vesiculosus to 99Tc was investigated. Constant value of concentration factors of 99Tc independence of sampling date, with an average value of (1.9 ± 0.5) × 105 L/kg, were obtained. This indicates that F. vesiculosus can be used as a reliable bio-indicator to monitor 99Tc concentration in seawater.

Determination of 99Tc in aqueous solutions of various cationic compositions using a varian 725-ES inductively coupled plasma optical emission spectrometer

A procedure was developed for determining the gravimetric concentration of 99Tc in aqueous solutions from spent nuclear fuel reprocessing without their preliminary separation, using an inductively coupled plasma optical emission spectrometer (ICP-OES). The optimal conditions for minimizing spectral and matrix interferences were determined. They allowed the lower limit of Tc determination in process salt solutions to be decreased from 1 to 0.25 mg l−1.

Determination of technetium-99 in environmental samples: A review

Due to the lack of a stable technetium isotope, and the high mobility and long half-life, 99Tc is considered to be one of the most important radionuclides in safety assessment of environmental radioactivity as well as nuclear waste management. 99Tc is also an important tracer for oceanographic research due to the high technetium solubility in seawater as TcO 4 −. A number of analytical methods, using chemical separation combined with radiometric and mass spectrometric measurement techniques, have been developed over the past decades for determination of 99Tc in different environmental samples. This article summarizes and compares recently reported chemical separation procedures and measurement methods for determination of 99Tc. Due to the extremely low concentration of 99Tc in environmental samples, the sample preparation, pre-concentration, chemical separation and purification for removal of the interferences for detection of 99Tc are the most important issues governing the accurate determination of 99Tc. These aspects are discussed in detail in this article. Meanwhile, the different measurement techniques for 99Tc are also compared with respect to advantages and drawbacks. Novel automated analytical methods for rapid determination of 99Tc using solid extraction or ion exchange chromatography for separation of 99Tc, employing flow injection or sequential injection approaches are also discussed.

Differential concentration of Technetium-99 (99Tc) in common intertidal molluscs with different food habits

Concentration of 99Tc has been measured in fucoids and molluscs, sampled in a sheltered intertidal at the southwest coast of Norway from February to November 2006. The concentrations of 99Tc in molluscs differed significantly between species. The filtering bivalve Mytilus edulis had the lowest concentrations with averages of 2.3–5.9Bqkg−1d.w., while the herbivorous gastropods Littorinalittorina, Littorina obtusata and Patella vulgata had higher concentrations. P. vulgata and L. obtusata had the highest concentrations, 40–47 and 26–30Bqkg−1d.w., respectively. L. obtusata has a specialized habit of living, and prefers to feed on fucoids. P. vulgata can graze extensively on the fucoid Ascophyllum nodosum when available. Fucoids are known to have very high uptake of 99Tc, and this was also found in the present study. The high 99Tc-concentrations of L. obtusata and P. vulgata are most likely due to their habit of feeding on fucoids.

Concentration of 99Tc and 137Cs in edible seaweed (Konbu) in the northern part of Japan

Concentration of 99Tc and 137Cs in edible seaweed (Konbu) in the northern part of Japan

Modelling 99Tc concentrations in Fucus vesiculosus from the north-east Irish Sea

In 1994 there were substantial increases in the quantity of 99Tc discharged into the north-east Irish Sea from BNFL Sellafield (UK), concomitant with improvements in waste treatment procedures. As a consequence, the concentration of 99Tc observed in seawater and biota samples, taken from the Irish Sea coastline, increased significantly. Elevated concentrations were also reported in Dutch, Danish, Norwegian, Swedish and Arctic waters in subsequent years. In the present study a simple numerical model was developed and applied to time-series data of 99Tc concentrations in the brown seaweed Fucus vesiculosus, collected from three UK sites in the vicinity of Sellafield (St. Bees, Heysham, Port William). The model considered site-specific scaling effects, lag times, previous discharge history and potential seasonal variation in uptake. In general, there was a good fit between predicted and observed concentrations, but the degree of uncertainty varied inversely with the frequency of sampling. We did not observe a significant seasonal variation. The modelled lag times to the three sites were consistent with transport times based on observations of the water column distribution of 99Tc. The model was applied to a variety of discharge scenarios, reflecting current discussion on the future management of 99Tc releases. Concentrations in Fucus reached asymptotic values in 3–10 years, depending on the scenario and sampling site under consideration.

Long-term study of 99Tc in the marine environment on the Swedish west coast

The activity concentration of 99Tc in brown seaweed ( Fucus vesiculosus and Fucus serratus) and seawater were analysed in samples collected in 1991, 1995 and 2001 at several stations along the Swedish west coast. In addition to these locations, a well-defined site (Särdal, 56.76 °N, 12.63 °E) was included with 99Tc activity concentration data in seaweed from 1967 to 2000. Over the years, the major source of 99Tc in the coastal waters of western Sweden has been the radioactive liquid discharge from the nuclear fuel reprocessing plant in Sellafield (UK) transported via ocean currents in the North Sea. The 99Tc activity concentration in seaweed at the Särdal site increased from approximately 30 Bq kg -1 up to 230 Bq kg -1 (dry weight) between 1997 and 2000 due to the Sellafield EARP (Enhanced Actinide Removal Plant) discharges in 1995–1996, yielding an approximate transport time of 4–5 years between the Irish Sea and the Kattegat. Due to the very sharp gradient in 99Tc concentration between the Baltic Sea and the North Sea, 99Tc is presently one of the best transit tracers for the recent ventilation events in the Baltic Sea.

Use of IAEA reference materials (IAEA-373 and 375) as low-level99Tc references

The concentration of99Tc in IAEA reference materials has been determined with an ICP-MS as 0.86±0.07 Bq·kg−1 dry for IAEA-373 (grass) and 0.25±0.02 Bq·kg−1 dry for IAEA-375 (soil). These being sufficiently higher than the detection limits of typical measurement methods, both materials can be used as reference materials for determining low-level99Tc in environmental samples.

Comparison of the TEVA-Spec resin and liquid-liquid extraction methods for the separation of technetium in soil samples

When ICP-MS is used for99Tc measurements, elements which interfere with99Tc counting should be removed. In this study, a separation method using a novel chromatographic resin (TEVA·Spec® resin) was compared with a liquid-liquid extraction (LLX) method for separation and concentration of99Tc which was trapped in a solution after combustion of environmental soil samples. The results showed that Tc could be separated from Ru at high recoveries with both separation methods. Molybdenum, however, was not removed by LLX, while more than 99% of Mo in soil samples were removed by TEVA·Spec resin.

Determination of technetium-99 in aqueous samples by isotope dilution inductively coupled plasma-mass spectrometry

An isotope dilution/inductively coupled plasma mass spectrometric method (ID/ICP-MS) for measuring the concentration of technetium-99 in aqueous samples was developed at the Savannah River Technology Center (SRTC). The procedure is faster than radiometric tecniques, is less subject to interferences, and has equal or better detection limits. It is currently being used to measure the concentration of99Tc in samples of Savannah River water collected in the vicinity of the Savannah River Site. In this method one liter samples of water are spiked with97Tc. After equilibration, the technetium is extracted from the sample with a chromatographic resin. Interfering elements, molybdenum and ruthenium, are either not retained by the resin or are washed off with, dilute nitric acid. The technetium is then eluted with more concentrated nitric acid, and the99Tc/97Tc ratio in the eluant is measured with an ICP-MS. The99Tc concentration in the original sample is calculated from the99Tc/97Tc ratio. The chemical recovery of the extraction procedure is greater than 90%. The detection limit of the instrument, taken as three times the background counts atm/z=99, is 0.6 part per trillion (ppt). The detection limit of the procedure, taken as three times the standard deviation of several reagent blank analyses, is 0.33 pCi/l.

Time series for sea water and seaweed of 99Tc and 125Sb originating from releases at La Hague

99Tc and 125Sb have been released in low level liquid waste at the reprocessing plant at La Hague (Fr). Over a number of years data have been obtained on the concentration of 99Tc in sea water and in seaweed from sampling locations close to and at increasing distances north and east of the point of release into the English Channel. In addition such data have been obtained on 125Sb for a small number of sampling points. These time series, and the information derived from their intercomparison and from comparison with the release data, are presented in this paper. Time series on 99Tc as well as 125Sb in sea water and seaweed clearly confirm a considerable decrease in release rates at La Hague over the years 1986–1993. Transit times and transfer factors derived from the series are generally in good agreement with the results of modelling efforts. The data do not provide evidence for a time lag between levels of the radionuclides in sea water and those in seaweed longer than a few months. The very high concentration factors for 99Tc in brown seaweeds make these seaweeds very useful for environmental monitoring the radionuclide at low release rates and to trace releases in areas remote from the point of release.

Radioanalytical studies of anthropogenic radionuclides in an anoxic fjord

The vertical distribution of 239+240Pu, 238Pu, 241Am, 99Tc, 137Cs and 134Cs has been studied in the permanently super-anoxic Framvaren fjord in southern Norway. The adjacent Helvik fjord (slightly anoxic below 14 m depth) was studied with the respect to the same radionuclides as a comparison for their distribution and levels during more normal conditions. Th was studied in both fjords as a representative for actinides in oxidation state +4. Vertical distribution of Pu, Am and Th in Framvaren all show increased concentrations with depth. Complex formation with DOC is believed to be the main cause for this behaviour. Increasing 232Th with depth in sediment indicates possible remobilization of this element from the sediments. The limited water exchange between the two fjords is illustrated by the low 238Pu239+240Pu ratio and the higher 134Cs137Cs ratio in Framvaren fjord, concentration of 99Tc in Framvaren are also lower than compared with the Helvik fjord. Concentration of 99Tc in Helvik and Framvaren fjord is approximately constant with depth.

High performance liquid chromatography of 99mTc labeled human serum albumin using an N-methylpyridinium polymer column.

Human serum albumin (HSA) labeled with 99mTc (99mTc-HSA) was analyzed by high performance liquid chromatography using a 4-vinylpyridinium polymer column which specifically resolved albumin components such as human mercaptalbumin (HMA), human non-mercaptalbumins (HNA), etc. The 99mTc-HSA radiochromatogram revealed that 99mTc-HSA consisted of several components. The radiochromatographic profile was similar to that of 99mTc-HMA prepared with 99mTc and separated HMA. This suggested that HMA participated mainly in 99mTc-labeling of HSA. When HSA was labeled with a stoichiometric concentration of 99Tc, the HMA peak was significantly decreased and new peaks were revealed by absorbance at 280 nm. From these results, the role of HMA in labeling HSA with 99mTc was elucidated.

Concentration of 99Tc in Seawater by Coprecipitation with Iron Hydroxide

海水中に7価で存在する過テクネチウム酸イオンを, ピロ亜硫酸カリウムで還元して水酸化鉄に共沈させ回収するための基礎的事項について検討した。最適条件下でのテクネチウムの回収率は98%以上ありほぼ定量的であった。大量の海水試料に本手法を応用するため, 反復共沈濃縮法を検討した。この濃縮法を用いれば, 一定量の水酸化鉄に高収率で反復してテクネチウムを濃縮できることが確認された。

The determination of 99Tc in marine algae.

A method for the determination of technetium in seaweeds was developed by the tracer experiment in which seaweeds were reared in seawater spiked with 95mTcO4- in aquarium. Technetium-99 content is determined for Arame, Eisenia bicyclis. Fresh seaweeds were collected at the coast of Nakaminato-shi, Ibaraki-Pref. and were weighed, air-dried and mineralized by conc. HNO3, followed by extraction with 30% (v/v) tri-n-octylamine-xylene solution. Beta-spectrum of 99Tc was identified by a beta-spectrometer. The concentration of 99Tc in Eisenia bicyclis was 503 mBq/kg fresh. The activity zc+as renteasured again after a year and any decrease was not observed.

The determination of technetium-99 in the brown marine alga [formula omitted] collected along the Belgian coast

The brown alga Fucus spiralis (Fucales) grows along the Belgian coast in sufficient amount to permit regular sampling. The algae were collected at four different places (Nieuwpoort, Oostende, Blankenberge and Zeebrugge) from March 1985 to February 1986. The method used to determine 99Tc and the subsequent results are reported. The concentration of 99Tc (Bq kg −1 dry weight) in whole plants was found to increase as a function of time. In addition, analyses on separated parts have revealed that, generally, apical fragments possess a lower content of 99Tc than the middle and basal ones. These results suggest that the old tissues of Fucus spiralis , present in middle and basal fragments, have integrated technetium uptake over a period of few years, in contrast to the young ones of the apices, which have probably fixed this radionuclide only during a short period of time. The concentration factors (CFs), evaluated on the basis of 3 mBq 99Tc ℓ −1 seawater, varied from 8,000 to 36,000 in whole plants, reaching however 51,000 in middle fragments. These figures are of the same order of magnitude than those reported for related species of Fucus collected along the French coast of the Channel. It adds further evidence that Fucus spiralis may be used as a bioindicator for 99Tc contamination of coastal waters.

99Tc in the sub-arctic food chain Lichen-Reindeer-man

The deposition, migration and annual variations of 99Tc fallout in carpets of lichen collected during the period 1956–1981 have been investigated. The transfer of 99Tc to reindeer and man has also been studied. Technetium showed a shorter mean residence time than 137Cs in the lichen carpet. The activity ratio 99Tc/ 137Cs was generally lower than the theoretical fission ratio of 1·43 × 10 −4. The maximum concentration of 99Tc in lichens occurred in 1967 (ca. 60 mBq kg −1) but in 1975 higher values were found than would have been predicted from fallout. The average depth integrated concentration of 99Tc at 62·3°N, 12·4° E in 1972 was 540 ± 100 mBq m −2. The studies of reindeer tissues show that technetium has a short mean residence time in the muscle tissues (ca. 5 days) and is not accumulated like 137Cs. The committed dose equivalent from 99Tc to the local Lapp population engaged in reindeer breeding is negligible.

Investigation of the Hydrothermal Interaction of 99Tc-Doped Glass with Basalt Repository Nuclear Waste Package Components

AbstractHydrothermal experiments using basalt-repository nuclear waste package components have been carried out at 200°C and 30 MPa using 99Tc-doped PNL 76–68 waste glass. This work was conducted in support of the Basalt Waste Isolation Project. The experiments were carried out in rocking autoclaves that allowed for periodic solution sampling. Preliminary results that illustrated the effect of basalt on 99Tc solution behavior were discussed previously[l]. In this paper, we continue those observations by discussing the additional experiments that investigated the effects of steel. We also include the post-experiment solid phase analyses from all test configurations.The effect of steel on glass dissolution was observed to be minimal when basalt was not present, i.e., there were no discernible differences in the amount of glass dissolved (based on boron release), with or without steel present.The 99Tc solution concentration results showed that basalt, steel, and a combination of basalt and steel have an ability to dramatically lower the concentration of 99Tc in the solution, probably through a redox mechanism[2]. Solid run product analyses showed that without basalt present, a gel-like secondary phase consisting of an iron, zinc clay with an apparent smectite structure formed. When basalt was present clinoptilolite formed as the major secondary phase, due primarily to the presence of aluminum in the basalt mesostasis. Separation of the various solid run products and residual initial solid phases has not yet been achieved. Such a separation would facilitate the identification of the phase or phases with which 99Tc was associated. The solution results indicated that 99Tc, a potentially mobile radionuclide, may be incorporated in a relatively insoluble phase in the environment of a basalt repository. In addition, no synergistic effects between waste package components were observed that would increase the concentration of 99Tc in solution.