Measurement Of 129I Research Articles

TOF system at MALT – Measurement of 129I

At Micro-Analysis Laboratory Tandem (MALT), the University of Tokyo, we have developed a new Accelerator mass spectrometry (AMS) technique with a time-of-flight (TOF) detection system for the measurement of 129I. By measuring not only the TOF but also the energy of the ions, we were successful in the discrimination of 129I from the isotope 127I and another ion with almost the same velocity. The measurement is performed with a reproducibility of 9%. The sensitivity of the system is at a ratio of 10 −14.

Iodine-129: Sample preparation, quality control and analyses of pre-nuclear materials and of natural waters from Lower Saxony, Germany

Sample preparation procedures for AMS measurements of 129I and 127I in environmental materials and some methodological aspects of quality assurance are discussed. Measurements from analyses of some pre-nuclear soil and thyroid gland samples and of a systematic investigation of natural waters in Lower Saxony, Germany, are described. Although the up-to-now lowest 129I/ 127I ratios in soils and thyroid glands were observed, they are still suspect to contamination since they are significantly higher than the pre-nuclear equilibrium ratio in the marine hydrosphere. A survey on all available 129I/ 127I isotopic ratios in precipitation shows a dramatic increase until the middle of the 1980s and a stabilization since 1987 at high isotopic ratios of about (3.6–8.3)×10 −7. In surface waters, ratios of (57–380)×10 −10 are measured while shallow ground waters show with ratios of (1.3–200)×10 −10 significantly lower values with a much larger spread. The data for 129I in soils and in precipitation are used to estimate pre-nuclear and modern 129I deposition densities.

AMS measurement of 129I, 36Cl and 14C in underground waters from Mururoa and Fangataufa atolls

AMS analyses of 36Cl, 129I and 14C in underground water have been performed as part of IAEA’s assessment of the radiological situation at Mururoa and Fangataufa atolls. The samples consisted of waters from monitoring wells, and from two cavity-chimneys created by underground nuclear tests. The water samples from the monitoring wells contained varying concentrations of radionuclides, with the highest concentrations of radionuclides found in the two test cavity-chimneys. A comparison of the concentrations of radionuclides determined by AMS, 36Cl and 129I, and with radionuclides determined using conventional methods, 3H, 90Sr and 137Cs, shows a reasonable correlation. However, some differences in behaviour, mainly attributed to differences in the sorption characteristics of the elements, are discernible. The concentrations of radionuclides in the underground environment were used to validate geosphere transport models.

AMS measurements of 14C and 129I in seawater around radioactive waste dump sites

According to a recent IAEA compilation of inventories of radioactive wastes dumped in the world ocean, a total of 85 PBq of radioactive wastes were dumped, in the Atlantic (45 PBq), the Pacific (1.4 PBq) and the Arctic (38 PBq) Oceans and their marginal seas between 1946 and 1993, mostly in the form of low-level wastes. 3H, and 14C formed an important part of the beta-activity of these dumped wastes. Because of its long half-life, 14C will be the main constituent in possible leakages from the wastes in the future. On the other hand, 14C and 129I are important radioactive tracers which have been artificially introduced into the oceans. Small amounts of 14C and 129I can be easily measured by accelerator mass spectrometry (AMS) on mg-size samples of carbon and iodine extracted from 500 ml seawater samples. The high analytical sensitivity enables one therefore to find even trace amounts of 14C and 129I which could be released from radioactive wastes, and to compare the measured levels with the global distribution of these radionuclides. The IAEAs Marine Environment Laboratory (IAEA-MEL) has been engaged in an assessment program related to radioactive waste dumping in the oceans since 1992 and has participated in several expeditions to the Atlantic, Arctic, Indian and Pacific Oceans to sample seawater, biota and sediment for radiological assessment studies. In the present paper, we report on methods of 14C and 129I measurements in seawater by AMS and present data on the NE Atlantic, the Arctic and the NW Pacific Ocean dumping sites. A small increase of 14C was observed at the NE Atlantic dumping site.

Developments towards a fully automated AMS system

The possibilities of computer-assisted and automated accelerator mass spectrometry (AMS) measurements were explored. The goal of these efforts is to develop fully automated procedures for “routine” measurements at the Vienna Environmental Research Accelerator (VERA), a dedicated 3-MV Pelletron tandem AMS facility. As a new tool for automatic tuning of the ion optics we developed a multi-dimensional optimization algorithm robust to noise, which was applied for 14C and 10Be. The actual isotope ratio measurements are performed in a fully automated fashion and do not require the presence of an operator. Incoming data are evaluated online and the results can be accessed via Internet. The system was used for 14C, 10Be, 26Al and 129I measurements.

Iodine-129 in Thyroid Glands: A Sensitive Biological Marker of Fission Product Exposure

appeared in the Journal of Radioanalytical and Nuclear Chemistry, Vol. 243, No. 2 (2000) 467–472.During the electronic submission of the paper the file was damaged, and parts were left out. In order to correct this, we publish the correct paper as a whole.Iodine-129 may be no radiation hazard but it is a useful marker. Animal thyroids concentrate the isotope to 4 orders of magnitude greater than the intake. This results in a potential biological and physical indicator of radioactive contamination. Since 1943, 129I/127I ratio in animal thyroids from the Northern Hemisphere has increased 2 to 5 orders of magnitude. Since 1985, thyroids of deer, living near a nuclear reprocessing facility have contained 129I which is 3 to 7 orders of magnitude greater than pre-nuclear levels. Limited measurements of 129I in thyroids from the Southern Hemisphere have shown little increase. An appendix is presented to show that 129I may be helpful to evaluate past radiation hazard from fission products.

The measurement of 36Cl and 129I in concrete wastes

A method has been developed for the measurement of chlorine and iodine radionuclides in concrete wastes generated from the decommissioning of nuclear power stations. Sequential oxidation of 129I and 36Cl from samples of concrete takes less than 7 h and the method is relatively simple and can be used to reliably determine low levels of 129I and 36Cl. Generally, recoveries for the procedure are high (in excess of 70%) and large sample sizes can be tolerated (≡1–10 g). This paper describes the development of the method and demonstrates a relatively simple, repeatable process for the measurement of 129I and 36Cl in concrete wastes. The equipment and the methods used should be available at most reactor sites or nuclear plants.

Determination of total iodine and sample preparation for AMS measurement of 129I in environmental matrices

A method is described for the measurement of total iodine and sample preparation for accelerator mass spectrometry (AMS) measurement of 129I. Samples were combusted in a stream of oxygen and the iodine liberated was collected in a trapping solution. Aliquots of the trapping solution were used to measure total iodine by gas chromatography and 129I by AMS. The method was tested using standard reference materials 2709 San Joaquin Soil, 2711 Montana Soil and 2704 Buffalo River Sediment from the National Institute of Standards and Technology, IAEA-375 soil from the International Atomic Energy Agency, a bovine thyroid sample from Gomel, KI and KIO3. The recoveries with respect to the reference values were between 89 and 100%. No tracers were used and no efficiency corrections were applied to these results.

Determination of iodine in milk and oyster tissue samples using combustion and peroxydisulfate oxidation.

Two methods are described for the preparation of samples for total iodine measurement in biological matrices. In the first method, the samples were combusted in a stream of oxygen to release iodine that, subsequently, was trapped in a solution as iodide. The second method is a new approach in which the samples were oxidized in a basic solution of peroxydisulfate. In this case, the iodine was retained in solution as iodate. Total iodine was measured by gas chromatographic analysis of the 2-iodopentan-3-one derivative. The methods were tested using Standard Reference Materials (SRMs) 1549 Non-Fat Milk Powder, and 1566a and 1566 Oyster Tissue. Also, KI and KIO3 were used for testing the procedures. The results obtained for the SRMs, given as average +/- standard deviation in micrograms g-1, were: 3.39 +/- 0.14 and 3.40 +/- 0.23 for SRM 1549; 4.60 +/- 0.42 and 4.51 +/- 0.45 for SRM 1566a; and 2.84 +/- 0.16 and 2.76 +/- 0.06 for SRM 1566; values corresponding to combustion and wet oxidation, respectively. Overall, the absolute recoveries varied between 91 and 103%. These methods can also be used in the preparation of targets for the measurement of 129I using accelerator mass spectrometry.

The feasibility of using 129I to reconstruct 131I deposition from the Chernobyl reactor accident.

Radioiodine released to the atmosphere from the accident at the Chernobyl nuclear power station in the spring of 1986 resulted in large-scale thyroid-gland exposure of populations in Ukraine, Belarus, and Russia. Because of the short half life of 131I (8.04 d), adequate data on the intensities and patterns of iodine deposition were not collected, especially in the regions where the incidence of childhood-thyroid cancer is now increasing. Results are presented from a feasibility study that show that accelerator-mass-spectrometry measurements of 129I (half life 16 x 106 y) in soil can be used to reconstruct 131I-deposition density and thus help in the thyroid-dosimetry effort that is now urgently needed to support epidemiologic studies of childhood-thyroid cancer in the affected regions.

The determination of 129I in milk and vegetation using neutron activation analysis

A new method has been developed to measure 129I in the environment with detection limits below 10 mBq/kg of vegetation and 10 mBq/1 of cows' milk. The method is based on extraction of 129I from the milk or vegetation sample, onto an ion exchange resin. An inactive carrier of 127I is added to the sample before separation, to monitor losses throughout the entire procedure. The ion exchange resin is irradiated for 7.5 h in a neutron flux of 10 16 n m −2 s −1 to induce the 129I(n,γ) 130I reaction with thermal neutrons. The 127I carrier undergoes a (n,2n) reaction with fast neutrons to produce 126I. Iodine is extracted from the ion exchange resin after irradiation with an elution scheme which removes contamination from the radionuclide 82Br, the main interference in the analysis. Finally iodine is precipitated as AgI for gamma ray analysis. The sample is counted for 3 h on a Ge semiconductor detector to measure the radionuclide 130I, which has a half life of 12.4 h and 126I, which has a half life of 13.0 days. The measured 130I activity is compared to a known standard to deduce the amount of 129I in the sample, and the concentrations are corrected for losses during processing using the measured activity of 126I. The detection limits for 129I by this method are below 10 mBq/l for milk samples and 10 mBq/kg for vegetation. In addition to routine monitoring of milk and grass samples the method has been used to measure 129I deposition on grass and soils in a field near the Sellafield plant. Results of these analyses, along with measurements of 129I in air and rainfall using the same methodology, have been used to determine deposition velocity and retention coefficients of 129I to grass.

The Antares AMS Centre: A Status Report

The ANTARES accelerator mass spectrometry facility at Lucas Heights Research Laboratory is operational and AMS measurements of 14C, 26Al and 36Cl are being carried out routinely. Measurement of 129I recently commenced and capabilities for other long-lived radioisotopes such as 10Be are being established. The overall aim of the facility is to develop advanced programs in Quaternary science, global climate change, biomedicine and nuclear safeguards.

Development of 129I AMS for the LLNL spectrometer

The multi-user tandem laboratory at LLNL was designed to be a versatile facility which could be configured to develop new capabilities as determined by the requirements of sponsoring agencies and experimental programs. The initial design made some compromises, driven by both the usual budgetary constraints and uncertainties in program needs and support. We were recently funded by the Office of Arms Control in the U.S. DOE to develop an 129I AMS capability. The first 129I measurements were performed this year after upgrades and modifications to the originally installed components were completed. The configuration of the present spectrometer and performance achieved to date will be described. Planned improvements to the injector and high energy spectrometer will be outlined.

Measurements of 129I in a nuclear power reactor by accelerator mass spectrometry

The method of accelerator mass spectrometry is applied to measurements of concentrations of the long-lived volatile fission product 129I ( t 1 2 = 1.6 × 10 7 a) in the primary heat transport (PHT) system and irradiated fuel bay (IFB) of a commercial nuclear power reactor. Concentrations of (8.1 ± 1.1) × 10 12 129I atoms per gram and between 10 11 and 10 13 129I atoms/L were measured in an ion-exchange resin and in the heavy water (PHT) system, respectively. The corresponding value for the IFB system water samples was 5–6 × 10 12 129I atoms/L. These measurements, based on very small size samples (of the order of 0.5 mL) emphasize the advantage of the present method where a simple chemical process for the iodine extraction enables a direct measurement of the 129I atom content of the samples. In view of the physical and chemical properties of iodine and their important implications in the environment, the method is likely to find even wider applications for the monitoring of 129I and the study of long-range nuclear waste storage.

Positive identification of XeH − molecular ion

We describe in the present work the observation of XeH − molecular ions from a standard Hiconex 834 source in which a sputter target of AgI mixed with Ag was sprayed with Xe gas. The formation of XeH − ions is positively demonstrated by identifying 129Xe and 131Xe by AMS analysis and energy and time-of-flight measurements, when negative ions of mass 130 and 132, respectively, are injected into the 14UD Rehovot Pelletron tandem accelerator. No evidence for the formation of Xe − ions was found. The dependence of the intensity of the xenon group on the xenon gas pressure in the ion source shows that the probability of formation of XeH − is very low and should not pose a significant background problem under normal circumstances in AMS measurements of 129I.

AMS measurements at the Munich tandem with a time-of-flight setup

A setup is described for AMS experiments with a time-of-flight measurement. Special features are a Wien filter after the accelerator, a stabilization system for the accelerator voltage using a weak parasitic beam of different magnetic rigidity, timing detectors with microchannel plates and various energy loss and residual energy detectors. The setup has been used for concentration measurements of 129I, 90Sr and 55Fe. In addition, A = 20 and A = 5 ions have been searched for to test the Pauli exclusion principle.

Measurements of 129I in Human and Bovine Thyroids in Europe-transfer of 129I Into the Food Chain

Bovine thyroid glands from different countries in Europe and human thyroid glands from Lower Saxony (Federal Republic of Germany) show isotopic 129I/127I ratios of 2.1 X 10(-9) to 8.2 X 10(-8) for cattle and 2.1 X 10(-9) to 8 X 10(-8) in humans. These values give information about the concentration of fallout 129I in Europe since most of these glands were collected in areas without nuclear facilities. Some of the human thyroids were collected after the Chernobyl accident between May 1986 and February 1988. Results obtained from human thyroids taken in some locations of Lower Saxony show no significant increase of the 129I during this time. Higher concentrations of 129I were only found in cattle grazing in the vicinity of a reprocessing plant in Mol, Belgium. Samples of soil, vegetation, milk, and water from this area contained higher than normal concentrations of 129I. The long-term transfer of radioiodine from the soil to the plant and the translocation within the soil were studied using a soil monolith with a 129I-contaminated surface. During the 4 y of the experiment, the transfer factor plant/soil decreased from 0.3 to 2.2 X 10(-3). Soil samples taken in 5-cm steps to a depth of 30 cm then at 40 and 50 cm depths showed that the transport of radioiodine to lower layers proceeds very slowly. The top 5-cm layer contained about 80% of the total radioactivity 52 mo after contamination. In an in-vivo study with a dairy cow, the transfer of radioiodine from feed to milk to cow meat and to pig thyroid gland was followed for 53 d using 129I-labeled pasture grass contaminated via roots. A part of the milk obtained from the cow was fed to a pig as a substitute for humans. The mean value of the transfer factor milk/feed was 2.4 X 10(-3) d kg-1. The values of the transfer factor cow meat/feed obtained for different muscle cuts and organs (excluding thyroid) ranged between 3.0 X 10(-4) (kidney) and 5.4 X 10(-2) d kg-1 f.w. The transfer factors pig thyroid/milk (as pig feed) and pig thyroid/cow feed exhibited values of 1.2 and 8.7 X 10(-3) d kg-1 f.w., respectively.

Standardization of 129I by a tracer method with photon-photon coincidences from the decay of 125I

Activity measurements of 129I are difficult by reason of the low specific activity of this radionuclide which necessitates high samples masses. A tracer method has therefore been elaborated which eliminates absorption effects from the source by using mixed samples of 129I and 125I, both radionuclides emitting photons with similar energies from about 27 to 40 keV. The photons are counted using two movable photon detectors with thin NaI(Tl) crystals connected to coincidence electronics and varying the source-detector distances from about 0.2 to 12 cm. The activity value obtained shows a relative standard deviation of about 0.4%. A systematic uncertainty in the order of 2% is estimated from the approximations of the method.

Low level measurements of129I in environmental samples

An analytical method for the determination of127I and129I in various environemntal samples has been developed. The method consists of the separation of iodine from the samples using a double layered quartz tube firing apparatus, post-irradiation purification of iodine, and measuring126I and130I by means of gamma spectrometry. The relative standard deviations of this method was less than 6%.

Neutron activation and mass spectrometric measurement of129I

An integrated procedure has been developed for measurement of129I by neutron activation analysis and mass spectrometry. An iodine isolation procedure previously used for neutron activation has been modified to provide separated iodine suitable for mass spectrometric measurement as well. Agreement between both methods has been achieved within error limits. The measurement limit by each method is about 107 atoms /2 fg/ of129I.