129I Concentrations Research Articles

SU-E-I-78: Establishing a Protocol for Quick Estimation of Thyroid Internal Contamination with 131I in Normal and Emergency Situations

Purpose: I-131 is one of the most frequent radionuclides used in nuclear medicine departments. The radiation workers, who manipulate the unsealed radio-toxic iodine, should be monitored for internal contamination. In this study a protocol was established for estimating I-131 activity absorbed in the thyroid glands of the nuclear medicine staff in normal working condition and also in accidents. Methods: I-131 with the activity of 10 μCi was injected inside the thyroid gland of a home-made anthropomorphic neck phantom. The phantom is made up of PMMA as soft tissue, and Aluminium as bone. The dose rate at different distances from the surface of the neck phantom was measured using a scintillator detector for duration of two months. Then, calibration factors were obtained, for converting the dose rate at each distance to the iodine activity inside the thyroid. Results: According to the results of this study, the calibration factors for converting the dose rates (nSv/h) at distances of 0cm, 1cm, 6cm, 11cm, and 16cm to the activity (kBq) inside the thyroid were found to be 0.03, 0.04, 0.14, 0.29, and 0.49 . Conclusion: This method can be effectively used for quick estimation of the I-131 concentration inside the thyroid of the staff for daily checks in normal working conditions and also in accidents.

Measurement of long-lived radionuclides in surface soil around F1NPP accident site by Accelerator Mass Spectrometry

In March 2011, vast amounts of radionuclides were released into the environment due to the Fukushima Daiichi Nuclear Power Plant (F1NPP) accident. However, very little work has been done concerning accident-derived long-lived nuclides such as 129I (T1/2=1.57×107year) and 36Cl (T1/2=3.01×105year). 129I and 131I are both produced by 235U fission in nuclear reactors. Being isotopes of iodine, these nuclides are expected to behave similarly in the environment. This makes 129I useful for retrospective reconstruction of 131I distribution during the initial stages of the accident. On the other hand, 36Cl is generated during reactor operation via neutron capture reaction of 35Cl, an impurity in the coolant or reactor component. Resulting 36Cl/Cl ratio within the reactor is thus much higher compared to that in environment. Similar to 129I, 36Cl is expected to have leaked out during the accident and it is important to evaluate its effects. In this study, 129I concentrations were determined in several surface soil samples collected around F1NPP. Average 129I/131I ratio was estimated to be 26.1±5.8 as of March 11, 2011, consistent with calculations using ORIGEN2 code and other published data. 36Cl/Cl ratios in some of the soil samples were likewise measured and ranged from 1.1×10−12 to 2.6×10−11. These are higher compared to ratios measured around F1NPP before the accident. A positive correlation between 36Cl and 129I concentration was observed.

Concentration of 129I in aquatic biota collected from a lake adjacent to the spent nuclear fuel reprocessing plant in Rokkasho, Japan.

The spent nuclear fuel reprocessing plant in Rokkasho, Japan, has been undergoing final testing since March 2006. During April 2006-October 2008, that spent fuel was cut and chemically processed, the plant discharged (129)I into the atmosphere and coastal waters. To study (129)I behaviour in brackish Lake Obuchi, which is adjacent to the plant, (129)I concentrations in aquatic biota were measured by accelerator mass spectrometry. Owing to (129)I discharge from the plant, the (129)I concentration in the biota started to rise from the background concentration in 2006 and was high during 2007-08. The (129)I concentration has been rapidly decreasing after the fuel cutting and chemically processing were finished. The (129)I concentration factors in the biota were higher than those reported by IAEA for marine organisms and similar to those reported for freshwater biota. The estimated annual committed effective dose due to ingestion of foods with the maximum (129)I concentration in the biota samples was 2.8 nSv y(-1).

Dynamic modelling of radionuclide uptake by marine biota: application to the Fukushima nuclear power plant accident

The dynamic model D-DAT was developed to study the dynamics of radionuclide uptake and turnover in biota and sediments in the immediate aftermath of the Fukushima accident. This dynamics is determined by the interplay between the residence time of radionuclides in seawater/sediments and the biological half-lives of elimination by the biota. The model calculates time-variable activity concentration of 131I, 134Cs, 137Cs and 90Sr in seabed sediment, fish, crustaceans, molluscs and macroalgae from surrounding activity concentrations in seawater, with which to derive internal and external dose rates.A central element of the model is the inclusion of dynamic transfer of radionuclides to/from sediments by factorising the depletion of radionuclides adsorbed onto suspended particulates, molecular diffusion, pore water mixing and bioturbation, represented by a simple set of differential equations coupled with the biological uptake/turnover processes. In this way, the model is capable of reproducing activity concentration in sediment more realistically.The model was used to assess the radiological impact of the Fukushima accident on marine biota in the acute phase of the accident. Sediment and biota activity concentrations are within the wide range of actual monitoring data. Activity concentrations in marine biota are thus shown to be better calculated by a dynamic model than with the simpler equilibrium approach based on concentration factors, which tends to overestimate for the acute accident period. Modelled dose rates from external exposure from sediment are also significantly below equilibrium predictions. The model calculations confirm previous studies showing that radioactivity levels in marine biota have been generally below the levels necessary to cause a measurable effect on populations. The model was used in mass-balance mode to calculate total integrated releases of 103, 30 and 3 PBq for 131I, 137Cs and 90Sr, reasonably in line with previous estimates.

Changes in concentrations of 131I, 134Cs and 137Cs in leafy vegetables, soil and precipitation in Tsukuba city, Ibaraki, Japan, in the first 4 months after the Fukushima Daiichi nuclear power plant accident

Concentrations of 131I: iodine-131, 134Cs: cesium-134 and 137Cs: cesium-137 in leafy vegetables, soil and precipitation after the Fukushima Daiichi nuclear power plant accident were investigated at Tsukuba city, approximately 170 km from the nuclear power plant. The first precipitation after the accident was on March 21–23, 2011, and contained an amount of radionuclides. The concentration of 131I in leafy vegetables, particularly spinach (Spinacia oleracea L.), was significantly increased because of dry deposition of the first radioactive plume. The concentrations of 131I, 134Cs and 137Cs in soil were significantly increased by the first precipitation on March 21–23; however, the contribution of precipitation to the concentrations of 131I, 134Cs and 137Cs in leafy vegetables was smaller than that in soil. Changes in the concentrations of 131I, 134Cs and 137Cs differed between spinach and komatsuna (Japanese mustard; Brassica campestris var. peruviridis).

Internal dosimetry of nuclear medicine workers through the analysis of 131I in aerosols

131I is widely used in nuclear medicine for diagnostic and therapy of thyroid diseases. Depending of workplace safety conditions, routine handling of this radionuclide may result in a significant risk of exposure of the workers subject to chronic intake by inhalation of aerosols. A previous study including in vivo and in vitro measurements performed recently among nuclear medicine personnel in Brazil showed the occurrence of 131I incorporation by workers involved in the handling of solutions used for radioiodine therapy. The present work describes the development, optimization and application of a methodology to collect and analyze aerosol samples aiming to assess internal doses based on the activity of 131I present in a radiopharmacy laboratory. Portable samplers were positioned at one meter distant from the place where non-sealed liquid sources of 131I are handled. Samples were collected over 1h using high-efficiency filters containing activated carbon and analyzed by gamma spectrometry with a high-purity germanium detection system. Results have shown that, although a fume hood is available in the laboratory, 131I in the form of vapor was detected in the workplace. The average activity concentration was found to be of 7.4Bq/m3. This value is about three orders of magnitude below the Derived Air Concentration (DAC) of 8.4kBq/m3. Assuming that the worker is exposed by inhalation of iodine vapor during 1h, 131I concentration detected corresponds to an intake of 3.6Bq which results in a committed effective dose of 7.13×10−5mSv. These results show that the radiopharmacy laboratory evaluated is safe in terms of internal exposure of the workers. However it is recommended that the presence of 131I should be periodically re-assessed since it may increase individual effective doses. It should also be pointed out that the results obtained so far reflect a survey carried out in a specific workplace. Thus, it is suggested to apply the methodology developed in this work to other nuclear medicine services where significant activities of 131I are routinely handled as an effective means to optimize individual exposures and improve occupational radiation protection safety.

Development of methodology to optimize management of failed fuels in light water reactors

Fuel cladding is one of the key components in a fission reactor that confines radioactive materials inside a fuel tube. During reactor operation, however, cladding is sometimes breached, and radioactive materials leak from the fuel pellet into the coolant water through the breach. The primary coolant water is therefore monitored so that any leak is quickly detected; coolant water is periodically sampled, and the concentration of radioactive iodine 131 (I-131), for example, is measured. Depending on the measured leakage concentration, the faulty fuel assembly with leaking rod is removed from the reactor and replaced immediately or at the next refueling. In the present study, an effort has been made to develop a methodology to optimize the management for replacement of faulty fuel assemblies due to cladding failures using measured leakage concentration. A model numerical equation is proposed to describe the time evolution of an increase in I-131 concentration due to cladding failures and is then solved using the Monte Carlo method as a function of sampling rate. Our results indicate that, to achieve rationalized management of failed fuels, higher resolution to detect a small amount of I-131 is not necessarily required, but more frequent sampling is favorable.

Daily variation of I-131, Cs-134 and Cs-137 activity concentrations in the atmosphere in Osaka during the early phase after the FDNPP accident

To investigate the time variations of radionuclides discharged from the Fukushima Daiichi nuclear power plants accident, we started collecting aerosol samples in Osaka, Japan, using a high-volume sampler from March 15 to May 1, 2011. Atmospheric radioactivity concentrations of I-131, Cs-134 and Cs-137 were measured with germanium semi-conductor detectors. Only I-131 was detected in the early phase and two Cs-134.137 peaks were found in Osaka in April. Using the HYSPLIT model, we concluded that direct transportation of the air mass from the Fukushima area was responsible for such events.

Radioiodine sorption/desorption and speciation transformation by subsurface sediments from the Hanford Site

During the last few decades, considerable research efforts have been extended to identify more effective remediation treatment technologies to lower the 129I concentrations to below federal drinking water standards at the Hanford Site (Richland, USA). Few studies have taken iodate into consideration, though recently iodate, instead of iodide, was identified as the major species in the groundwater of 200-West Area within the Hanford Site. The objective of this study was thus to quantify and understand aqueous radioiodine species transformations and uptake by three sediments collected from the semi-arid, carbonate-rich environment of the Hanford subsurface. All three sediments reduced iodate (IO3−) to iodide (I−), but the loamy-sand sediment reduced more IO3− (100% reduced within 7 days) than the two sand-textured sediments (∼20% reduced after 28 days). No dissolved organo-iodine species were observed in any of these studies. Iodate uptake Kd values ([Isolid]/[Iaq]; 0.8–7.6 L/kg) were consistently and appreciably greater than iodide Kd values (0–5.6 L/kg). Furthermore, desorption Kd values (11.9–29.8 L/kg) for both iodate and iodide were consistently and appreciably greater than uptake Kd values (0–7.6 L/kg). Major fractions of iodine associated with the sediments were unexpectedly strongly bound, such that only 0.4–6.6 % of the total sedimentary iodine could be exchanged from the surface with KCl solution, and 0–1.2% was associated with Fe or Mn oxides (weak NH2HCl/HNO3 extractable fraction). Iodine incorporated into calcite accounted for 2.9–39.4% of the total sedimentary iodine, whereas organic carbon (OC) is likely responsible for the residual iodine (57.1–90.6%) in sediments. The OC, even at low concentrations, appeared to be controlling iodine binding to the sediments, as it was found that the greater the OC concentrations in the sediments, the greater the values of uptake Kd, desorption Kd, and the greater residual iodine concentrations (non-exchangeable, non-calcite-incorporated and non-Mn, Fe-oxide associated). This finding is of particular interest because it suggests that even very low OC concentrations, <0.2%, may have an impact on iodine geochemistry. The findings that these sediments can readily reduce IO3−, and that IO3− sorbs to a greater extent than I−, sheds light into earlier unexplained Hanford field data that demonstrated increases in groundwater 127I−/127IO3− ratios and a decrease groundwater 129IO3− concentrations along a transect away from the point sources, where iodine was primarily introduced as IO3−. While a majority of the radioiodine does not bind to these alkaline sediments, there is likely a second smaller iodine fraction in the Hanford subsurface that is strongly bound, presumably to the sediment OC (and carbonate) phases. This second fraction may have an impact on establishing remediation goals and performance assessment calculations.

Modeling of atmospheric dispersion with dry deposition: an application on a research reactor

An analytical solution of the three dimensional advection-diffusion equations has been formulated to simulate the dispersion of pollutants in the planetary boundary layer. The solution is based on the assumption that the concentration distribution of pollutants in the crosswind direction has a Gaussian shape and the wind speed is constant. The analytical solution has been obtained in two cases where, the vertical eddy diffusivity is taken to be dependent on: (a) the downwind distance x only and (b) the vertical height z only. The dry deposition of the diffusing particles on the ground is taken into account throughout the boundary conditions. The resulting analytical formulae have been applied to calculate the concentration of I-131 using data collected from the experiments conducted to collect air samples around the Research Reactor. Statistical measures are utilized in the comparison between the predicted and observed concentrations. The results are discussed and presented in tables and illustrative figures.

Speciation of iodine isotopes inside and outside of a contaminant plume at the Savannah River Site

A primary obstacle in understanding the fate and transport of the toxic radionuclide 129I (a thyroid seeker) is an accurate method to distinguish it from the stable isotope, 127I, and to quantify the various species at environmentally relevant concentrations (~10−8M). A pH-dependent solvent extraction and combustion method was paired with accelerator mass spectrometry (AMS) to measure ambient levels of 129I/127I isotope ratios and iodine speciation (iodide (I−), iodate (IO3−), and organo-I (OI)) in aquatic systems. The method exhibited an overall uncertainty of 10% or less for I− and IO3−, and less than 30% for OI species concentrations and enabled 129I measurements as low as 0.001Bq/L (1Bq/L=10−13M). The method was used to analyze groundwater from the Savannah River Site (SRS), South Carolina, USA, along a pH, redox potential (Eh), and organic carbon gradient (8–60μM DOC). The data confirmed that the 129I/127I ratios and species distribution were strongly pH dependent and varied in a systematic manner from the strongly acidic source. While 129I speciation in plume samples containing total I concentrations >1.7Bq/L was similar whether measured by AMS or GC–MS ([I−]≫[IO3−]=[OI]), AMS enabled 129I speciation measurements at much lower concentrations than what was possible with GC–MS. AMS analyses demonstrated that groundwater samples minimally impacted by the plume were still orders of magnitude higher than ambient 129I concentrations typically found elsewhere in the USA groundwaters and rivers. This is likely due to past atmospheric releases of volatile 129I species by SRS nuclear reprocessing facilities near the study site. Furthermore, the results confirmed the existence of 129I not only as I−, but also as OI and IO3− species.

Determination of 129I in the accumulated radioactive water and processed water of the Fukushima Daiichi Nuclear Power Plant

Accumulated radioactive water (AW) and processed water (PW) were sampled from certain locations of the accumulated radioactive water processing facility at the Fukushima Daiichi Nuclear Power Plants, in order to estimate the radioactivity of the secondary waste such as zeolite and sludge, which adsorbed radioactive material. The method to separate iodide ion (I−) from other radionuclides using the solid phase extraction sorbent, Anion SR, was optimized to measure the concentration of 129I in the AW and PW samples. After the chemical separation, the concentration of 129I in the sampled water was determined by inductively coupled plasma mass spectrometry with a dynamic reaction cell (DRC-ICP-MS).

Iodine-129 in water samples collected adjacent to a spent nuclear fuel reprocessing plant in Rokkasho, Japan

The spent nuclear fuel reprocessing plant in Rokkasho, Japan, has been undergoing final testing since March 2006. The concentrations of 129I in environmental water samples collected around the reprocessing plant were measured from 2005 to 2012. The 129I concentrations in water samples of the brackish lake adjacent to a plant from 2006 to 2008 which the spent fuel rods were cut and chemically processed, was higher than the background level. The major source of 129I in the lake was dominated by the direct deposition of 129I from the atmosphere than that from the ocean.

Mineral transformation controls speciation and pore-fluid transmission of contaminants in waste-weathered Hanford sediments

Portions of the Hanford Site (WA, USA) vadose zone were subjected to weathering by caustic solutions during documented releases of high level radioactive waste (containing Sr, Cs and I) from leaking underground storage tanks. Previous studies have shown that waste-sediment interactions can promote variable incorporation of contaminants into neo-formed mineral products (including feldspathoids and zeolites), but processes regulating the subsequent contaminant release from these phases into infiltrating background pore waters remain poorly known. In this paper, reactive transport experiments were conducted with Hanford sediments previously weathered for one year in simulated hyper-alkaline waste solutions containing high or low 88Sr, 127I, and 133Cs concentrations, with or without CO2(aq). These waste-weathered sediments were leached in flow-through column experiments with simulated background pore water (characteristic of meteoric recharge) to measure contaminant release from solids formed during waste-sediment interaction. Contaminant sorption–desorption kinetics and mineral transformation reactions were both monitored using continuous-flow and wet-dry cycling regimes for ca. 300 pore volumes. Less than 20% of contaminant 133Cs and 88Sr mass and less than 40% 127I mass were released over the course of the experiment. To elucidate molecular processes limiting contaminant release, reacted sediments were studied with micro- (TEM and XRD) and molecular- (Sr K-edge EXAFS) scale methods. Contaminant dynamics in column experiments were principally controlled by rapid dissolution of labile solids and competitive exchange reactions. In initially feldspathoidic systems, time-dependent changes in the local zeolitic bonding environment observed with X-ray diffraction and EXAFS are responsible for limiting contaminant release. Linear combination fits and shell-by-shell analysis of Sr K-edge EXAFS data revealed modification in Sr–Si/Al distances within the zeolite cage. Wet-dry cycling did not affect significantly molecular-scale transformations relative to continuous-flow controls. Results indicate that contaminants bound to the solid phase in distinct micro- and molecular-scale coordinative environments can generate similar macro-scale release behaviors, highlighting the need for multi-scale interrogations to constrain mechanisms of reactive transport. Data also indicate that weathering-induced change in ion exchange selectivity coefficients should be incorporated in simulations of contaminant release from caustic high-level radioactive waste impacted sediments.

Analysis of 129I in the soils of Fukushima Prefecture: preliminary reconstruction of 131I deposition related to the accident at Fukushima Daiichi Nuclear Power Plant (FDNPP)

Iodine-131 is one of the most critical radionuclides to be monitored after release from reactor accidents due to the tendency for this nuclide to accumulate in the human thyroid gland. However, there are not enough data related to the reactor accident in Fukushima, Japan to provide regional information on the deposition of this short-lived nuclide (half-life = 8.02 d). In this study we have focused on the long-lived iodine isotope, 129I (half-life of 1.57 × 107 y), and analyzed it by accelerator mass spectrometry (AMS) for surface soil samples collected at various locations in Fukushima Prefecture. In order to obtain information on the 131I/129I ratio released from the accident, we have determined 129I concentrations in 82 soil samples in which 131I concentrations were previously determined. There was a strong correlation (R2 = 0.84) between the two nuclides, suggesting that the 131I levels in soil samples following the accident can be estimated through the analysis of 129I. We have also examined the possible influence from 129mTe on 129I, and found no significant effect. In order to construct a deposition map of 131I, we determined the 129I concentrations (Bq/kg) in 388 soil samples collected from different locations in Fukushima Prefecture and the deposition densities (Bq/m2) of 131I were reconstructed from the results.

Influence of releases of 129I and 137Cs from European reprocessing facilities in Fucus vesiculosus and seawater from the Kattegat and Skagerrak areas

129I is a very long-lived radionuclide (T1/2=15.7×106 years) that is present in the environment because of natural and anthropogenic sources. Compared to the pre-nuclear era, large amounts of 129I have been released to the marine environment, especially as liquid and gaseous discharges from two European reprocessing facilities located at Sellafield (England) and La Hague (France). The marine environment, i.e., the oceans, is the major source of iodine. Brown seaweed accumulates iodine at high levels up to 1.0% of dry weigh, and therefore they are ideal bioindicators for studying levels of 129I. In this work, 129I concentrations have been determined in seaweed Fucus vesiculosus and seawater collected in the Kattegat and Skagerrak areas in July 2007. The resulting data were evaluated in terms of 129I concentrations and 129I/137Cs ratios. 129I concentrations were found to be in the order of (44–575)×109atomsg−1 in seaweed and (5.4–51)×109atomsg−1 in seawater, with an enhancement in the Skagerrak area in comparison to the Kattegat area. Iodine-129 concentrations in both seaweed and seawater were used to determine the concentration factor of iodine in brown seaweed F. vesiculosus.The high levels of 129I and 129I/137Cs ratios in the Skagerrak area and their gradually decreasing trend to the Kattegat indicates that the most important contribution to the 129I inventory in those areas comes from Sellafield and La Hague reprocessing plants.

Extraction of 129I and 127I via combustion from organic rich samples using 125I as a quantitative tracer

Iodine-129 (129I) is a biophilic, naturally occurring radioisotope (half-life: 1.57 × 107 years) that has been released in large quantities by nuclear fuel reprocessing. This iodine has cycled throughout the globe and chiefly the northern hemisphere and can be found in a wide variety of environmental materials, particularly organic rich soil and organic matter. Extracting iodine reliably from solid samples has been done by a variety of methods, however, pyrohydrolysis has been the most widely used. There is a wide variation between existing pyrohydrolysis techniques and this raises questions about the quantitative recovery of iodine from method to method. In order to quantify iodine recovery from pyrohydrolysis we have spiked samples with an iodine-125 radiotracer prior to combustion and trapping in an alkaline solution. Inorganic 125I tracer was used as well as humic acid labeled with 125I to simulate the behavior of 129I and 127I in complex organic substances and extract iodine regardless of how it is partitioned. Using these tracers we explored the effect on recovery of 125I under a variety of combustion parameters. These include carrier gas flow rate and iodine volatilization temperature. We observed that the best recoveries of 125I were at flow rates between 400 and 800 mL/min and most 125I recoveries were above 85%. The experiment to determine the temperature at which iodine volatilizes from the sample showed two distinct trends for the release of iodine. One trend showed that most iodine is released at approximately 525 °C, while the other trend showed that the samples needed to reach 800 °C and remain there for at least an hour. These findings illustrate the usefulness and importance of using a quantitative recovery tracer for every iodine extraction. We then combusted and precipitated several Atlantic Ocean seaweed and standard reference materials for AMS analysis as AgI. The 129I concentration of the seaweed ranged between 4.4–5.5 × 109 atoms/g and the 129I/127I ratio was 2.3–2.9 × 10−9, both of which compare well to published values for Atlantic seaweed. The results for the standard reference materials also agree with specified values indicating that this technique is reliable. By optimizing pyrohydrolysis conditions and testing the recovery of iodine with a 125I tracer it is possible to quantify and maximize recovery from organic samples. This will allow for the investigation of variations in the 129I concentration and 129I/127I ratio with a high degree of precision in complex, organic rich samples.

Radionuclide transfer from feed to camel milk

The transfer of 137Cs, 85Sr, 131I, 210Po, 210Pb and 238U from feed to camel's milk was investigated in a pilot experiment with three lactating camels. For a period of 60 days, the animals were fed on spiked feed containing the studied radionuclides. They were subsequently returned to a contamination-free diet and monitored for another 90 days. The activity concentrations of 137Cs, 85Sr and 131I in milk decreased with time and reached background levels after 20 days. Equilibrium transfer coefficients and biological half-lives were estimated and transfer coefficients were calculated as (8.1 ± 3.6) × 10−4, (4.4 ± 1.6) × 10−2, (7.8 ± 3.9) × 10−4, (2.7 ± 3.5) × 10−4, (1.8 ± 1.5) × 10−4 and (7.0 ± 3.6) × 10−3 d L−1 for 85Sr, 131I, 137Cs, 210Po, 210Pb and 238U, respectively. The biological half-lives were estimated to be 6.4, 4.2, 8.9, and 53.3 days for 85Sr, 131I, 137Cs, and 238U, respectively. Estimates of the half-lives were based on a one component model: it was found that the half-life values measured for artificial radionuclides were slightly shorter than those for natural radionuclides. The data obtained in the study are the first published experimental data on radionuclide transfer to camel milk.

Accurate determination of 129I concentrations and 129I/137Cs ratios in spent nuclear resins by Accelerator Mass Spectrometry

Determining long-lived radionuclide concentrations in radioactive waste has fundamental implications for the long-term management of storage sites. This paper focuses on the measurement of low 129I contents in ion exchange resins used for primary fluid purification in Pressurised Water Reactors (PWR). Iodine-129 concentrations were successfully determined using Accelerator Mass Spectrometry (AMS) following a chemical procedure which included (1) acid digestion of resin samples in HNO3/HClO4, (2) radioactive decontamination by selective iodine extraction using a new chromatographic resin (CL Resin), and (3) AgI precipitation. Measured 129I concentrations ranged from 4 to 12ng/g, i.e. from 0.03 to 0.08Bq/g. The calculation of 129I/137Cs activity ratios used for routine waste management produced values in agreement with the few available data for PWR resin samples.

Temporal Variation of Iodine Isotopes in the North Sea

Monitoring temporal variability of (129)I in the North Sea, a relatively large reservoir of radioactive discharges from the nuclear fuel reprocessing facilities, is vital for the environmental situation in the region. New information on concentration levels and distribution of (129)I and (127)I and their species forms (iodide and iodate) are gained here through sampling of surface water in 2010. The results show generally large spatial and temporal (compared to data from 2005) fluctuations of total (129)I and (127)I, and iodide and iodate. In samples south of 53°N, the level of (127)I(-) in 2010 was generally comparable or higher than in 2005. The results also show total (129)I concentrations comparable in the south, but 2-8 times lower in the north, to the analyses made in 2005. Different from total (129)I, the (129)I(-)/(129)IO3(-) values in the northern part were 2 times higher in 2010 than values observed in 2005. These variations in total (129)I and (127)I and their species are related to coastal water offshore propagation and surface currents that are linked to long-term and seasonal climatic changes over the North Atlantic and North Sea. Inventory estimation shows that >90% of (129)I resides in the Southern and German Bights, which also suggests negligible contribution from the Sellafield facility discharges when compared with that from the La Hague. Variability in discharge rate from La Hague may also affect the distribution patterns of (129)I in the North Sea on the monthly scale.