Radioactive 129I Research Articles

Rapid and selective removal of radioactive iodide ions from wastewater via bismuth-based metal-organic frameworks

As one of the main components of the nuclear wastewater discharged from Fukushima, the efficient and safe disposal of radioactive 129I- is very urgent. Here, the trapping ability of water-soluble iodine anions is studied through a metal-organic framework of bismuth (Bi-MOF, select CAU-17 as the representative). It is found that CAU-17 achieves efficient capture of I- ions through chemical and physical cooperative adsorption, with a maximum adsorption capacity of up to 268.9 mg g-1. In addition, the adsorbent also exhibits superior adsorption kinetics and selectivity for I- ions and works stably over a wide pH range of 2–12. Density functional theory (DFT) calculations indicate that most I- ions are immobilized by attacking the Bi3+ sites of the CAU-17 ternary channel to form BiOI compounds. Compared with silver-based adsorbent, the prepared Bi-based adsorbent CAU-17 is more economical and practical. In summary, this work demonstrates the promising application of Bi-MOFs for purifying industrial water-soluble radioactive iodide ions.

Selective removal of radioactive iodine from water using reusable Fe@Pt adsorbents

Environmental damage from serious nuclear accidents should be urgently restored, which needs the removal of radioactive species. Radioactive iodine isotopes are particularly problematic for human health because they are released in large amounts and retain radioactivity for a substantial time. Herein, we prepare platinum-coated iron nanoparticles (Fe@Pt) as a highly selective and reusable adsorbent for iodine species, i.e., iodide (I−), iodine (I2), and methyl iodide (CH3I). Fe@Pt selectively separates iodine species from seawater and groundwater with a removal efficiency ≥ 99.8%. The maximum adsorption capacity for the iodine atom of all three iodine species was determined to be 25 mg/g. The magnetic properties of Fe@Pt allow for the facile recovery and reuse of Fe@Pt, which remains stable with high efficiency (97.5%) over 100 uses without structural and functional degradation in liquid media. Practical application to the removal of radioactive 129I and feasibility for scale-up using a 20 L system demonstrate that Fe@Pt can function as a reusable adsorbent for the selective removal of iodine species. This systematic procedure is a standard protocol for designing highly active adsorbents for the clean separation and removal of various chemical species dissolved in wastewater.

Synthesis, structure and thermal stability of iodine-contained sodalites Na8(AlSiO4)6Cl2-I (x = 0–2) for 129I immobilization

Sodalites are one of the potential candidate forms for the radioactive 129I immobilization. In this work, the synthesis, structure and thermal stability of iodine-contained sodalites Na8(AlSiO4)6Cl2-xIx (x = 0–2) were studied. The high temperature solid phase method combined with high pressure tableting and NaOH solution scrubbing was proposed to synthesize iodine-contained sodalites with single phase. The X-ray diffraction Rietveld analysis shows that, the crystal structure of Na8(AlSiO4)6Cl2-xIx varies as a function of the iodine content, x. The thermal stability of iodine-contained sodalites was studied by thermogravimetric analysis and high temperature annealing experiments. The iodine-contained sodalites exhibit good stability below 750 °C. A phase decomposition from the sodalite phase into the nepheline phase was observed for each composition at higher temperatures. The quantitative analysis of phase decomposition of Na8(AlSiO4)6Cl2-xIx annealed at 900 °C for 3 h further confirms the negative effects of iodine-doping on the thermal stability of samples.

Pure and Sb-doped ZrO2 for removal of IO3− from radioactive waste solutions

Radioactive 129I with a long half-life (1.57 × 107 y) and high mobility is a serious radiohazard and one of the top risk radionuclides associated with its accidental and planned releases to nature. The complex speciation chemistry of iodine makes its removal a complicated task, and usually a single method is not able to remove all iodine species. Especially its oxidized form iodate (IO3−) lacks a selective and effective removal method. Here, the granular aggregates of hydrous zirconium oxides with and without antimony doping were tested for IO3− removal and the effects of contact time, competing anions in different concentrations and pH were examined. The materials showed high selectivity for IO3− (Kd over up to 50,000 ml/g) in the presence of competing ions and relatively fast uptake kinetics (eq. < 1 h). However, B(OH)4− and SO42−, as competing ions, lowered the iodate uptake significantly in basic and acidic solution, respectively. The suitability of the materials for practical applications was tested in a series of column experiments where the materials showed remarkably high apparent capacity for the IO3− uptake (3.2–3.5 mmol/g).Graphic abstract

Exposure Ages, Noble Gases and Nitrogen in the Ordinary Chondrite Karimati (L5)

Noble gas and nitrogen isotopic compositions of Karimati ordinary (L5) chondrite are presented. Aliquots of the meteorite were studied in two noble gas mass spectrometers. Its cosmic ray exposure (CRE) history, trapped noble gases and nitrogen isotopic systematic are examined. The compositions of Ne and Kr in this meteorite indicate presence of mixture of solar wind and Q trapped components. In addition to the primordial components, radiogenic 129Xe (from the decay of short-lived radioactive 129I) is observed in the two aliquots (129Xe/132Xe ranges between 1.054 and 1.311). The U/Th-4He and K-40Ar ages are discordant. U/Th-4He ages are younger than the K-40Ar ages, indicating loss of helium. The trapped N component is isotopically light analogous to Q gas/solar wind. The cosmic-ray exposure ages of the two aliquots are 16.1 ± 2.7 Ma and 16.6 ± 2.0 Ma based on the cosmogenic 21Nec and 38Arc concentrations.

Anthropogenic 129I in the sediment cores in the East China sea: Sources and transport pathways

With the increased numbers of nuclear power plants constructed along the east coast of China, it is important to know radioactive sources and transport pathways between land and sea, in order to better understand the impact of these nuclear facilities to the marine environment. Two sediment cores collected from the East China Sea dated to 1959–2010 were analyzed for long-lived radioactive 129I and stable 127I. It was observed that 129I levels (129I/127I ratio of (15.0–75.0) × 10−12) were significantly increased compared to the pre-nuclear value (129I/127I = 1.5 × 10−12). Some 129I peaks were observed in layers of 1959, 1966, 1971 and 1976 (1977), corresponding to the atmospheric nuclear weapon tests at Pacific Proving Grounds and Lop Nor. The high values of 129I after the late 1970s are attributed to the releases from the European reprocessing plants. In addition to ocean current transport, the atmospheric dispersion through the interaction of the Westerlies with East Asia monsoon is the important pathway of large-scale transport of pollutants from high latitude West Europe to middle latitude East Asia. Riverine input is the main transport pathway of radioactive pollutants released from Lop Nor to the East China Sea through the atmospheric dispersion, deposition and runoff processes.

Pre-nuclear level of 129I in Chinese loess-paleosol sections: A search for the natural 129I level for dating in terrestrial environments

Due to its long half-life (15.7 Myr), radioactive 129I has great potential for dating geologic materials as old as 100 Myr. Thus, knowing the natural level of 129I is crucial to dating applications. The initial ratio of 129I/127I in the ocean has been quantified by a number of researchers who have reached a consensus value. However, the applicability of 129I dating in the terrestrial environment remains problematic because the lack of an initial 129I/127I value. In this work, samples of loess-paleosol sections from the Chinese Loess Plateau (CLP) were analyzed for 129I/127I, aiming to provide an initial 129I/127I ratio that can be adopted for dating purposes in terrestrial environments. A value of (2.0 ± 1.0) × 10−11 for the 129I/127I ratio was found in two investigated loess-paleosol sections from Xifeng and Luochuan, China. This ratio is one order of magnitude higher than the initial value reported for the marine environment. Alteration of the natural initial 129I in the investigated samples due to the downward migration of anthropogenic 129I and by excess fissiogenic 129I from uranium was not supported. Consequently, the 129I/127I ratio measured is considered to be a pristine value, and the difference from that in the marine systems is attributed to an isotopic dilution effect.

Experimental determination of solubilities of magnesium borates: Solubility constants of boracite [Mg3B7O13Cl(cr)] and aksaite [MgB6O7(OH)6·2H2O(cr)

Abstract In this study, solubility measurements regarding boracite [Mg3B7O13Cl(cr)] and aksaite [MgB6O7(OH)6·2H2O(cr)] from the direction of supersaturation were conducted at 22.5 ± 0.5 °C. The equilibrium constant (log10K0) for boracite in terms of the following reaction, Mg 3 B 7 O 13 Cl cr + 15 H 2 O l ⇌ 3Mg 2 + + 7B OH 4 − + Cl − + 2H + is determined as −29.49 ± 0.39 (2σ) in this study. The equilibrium constant for aksaite according to the following reaction, MgB 6 O 7 OH 6 · 2H 2 O cr + 9H 2 O l ⇌ Mg 2 + + 6B OH 4 − + 4H + is determined as −44.41 ± 0.41 (2σ) in this work. This work recommends a set of thermodynamic properties for aksaite at 25 °C and 1 bar as follows: ΔHf0 = −6063.70 ± 4.85 kJ·mol−1, ΔGf0 = −5492.55 ± 2.32 kJ·mol−1, and S0 = 344.62 ± 1.85 J·mol−1·K−1. Among them, ΔGf0 is derived from the equilibrium constant for aksaite determined by this study; ΔHf0 is from the literature, determined by calorimetry; and S0 is computed in the present work from ΔGf0 and ΔHf0. This investigation also recommends a set of thermodynamic properties for boracite at 25 °C and 1 bar as follows: ΔHf0 = −6575.02 ± 2.25 kJ·mol−1, ΔGf0 = −6178.35 ± 2.25 kJ·mol−1, and S0 = 253.6 ± 0.5 J·mol−1·K−1. Among them, ΔGf0 is derived from the equilibrium constant for boracite determined by this study; S0 is from the literature, determined by calorimetry; and ΔHf0 is computed in this work from ΔGf0 and S0. The thermodynamic properties determined in this study can find applications in many fields. For instance, in the field of material science, boracite has many useful properties including ferroelectric and ferroelastic properties. The equilibrium constant of boracite determined in this work will provide guidance for economic synthesis of boracite in an aqueous medium. Similarly, in the field of nuclear waste management, iodide boracite [Mg3B7O13I(cr)] is proposed as a waste form for radioactive 129I. Therefore, the solubility constant for chloride boracite [Mg3B7O13Cl(cr)] will provide the guidance for the performance of iodide boracite in geological repositories. Boracite/aksaite themselves in geological repositories in salt formations may be solubility-controlling phase(s) for borate. Consequently, solubility constants of boracite and aksaite will enable researchers to predict borate concentrations in equilibrium with boracite/aksaite in salt formations.

Silver phosphate glasses for immobilization of radioactive iodine

Management of radioactive 129I is a challenging issue due to its significantly long half-life and negative health effects. In this study, silver iodide (AgI)-incorporated silver phosphate glasses were prepared to immobilize 129I for a long time. A melt-quenching method was employed to synthesize the glasses at 450°C to prevent the evolution of I during the heat treatment. Characterization of the AgI-Ag2O-P2O5 specimens revealed that the addition of AgI was possible up to 60mol% into the glassy matrix although there were some amounts of Ag4I(PO4) and AgI clusters. This result was supported by the structural analysis which showed that the major iodine environment was composed of Ag and O regardless of the specimen compositions. The normalized leaching rates obtained by the 7-day PCT-A test showed that the chemical stability of iodine was satisfactory with the lowest leaching rate of 1.7×10−4gm−2/d. Our findings in this study demonstrate the potential of silver phosphate glass for the immobilization of radioactive 129I.

A comprehensive study of noble gases and nitrogen in “Hypatia”, a diamond-rich pebble from SW Egypt

This is a follow-up study of a work by Kramers et al. (2013) on a very unusual diamond-rich rock fragment found in the area of south west Egypt in the south-western side of the Libyan Desert Glass strewn field. This pebble, called Hypatia, is composed of almost pure carbon. Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) results reveal that Hypatia is mainly made of defect-rich diamond containing lonsdaleite and multiple deformation bands. These characteristics are compatible with an impact origin on Earth and/or in space. We also analyzed concentrations and isotopic compositions of all five noble gases and nitrogen in several ∼mg sized Hypatia samples. These data confirm the conclusion by Kramers et al. (2013) that Hypatia is extra-terrestrial. The sample is relatively rich in trapped noble gases with an isotopic composition being close to the Q component found in many types of meteorites. 40Ar/36Ar ratios in individual steps are as low as 0.4±0.3. Cosmic-ray produced “cosmogenic” 21Ne is present in concentrations corresponding to a nominal cosmic-ray exposure (CRE) age of roughly 0.1 Myr if produced in a typical meter-sized meteoroid. Such an atypically low nominal CRE age suggests high shielding in a considerably larger body. In addition to the Xe–Q composition, an excess of radiogenic 129Xe (from the decay of short-lived radioactive 129I) is observed (Xe129/Xe132=1.18+/−0.03). Two isotopically distinct N components are present, an isotopically heavy component (δN15∼+20‰) released at low temperatures and a major isotopically light component (δN15∼−110‰) at higher temperatures. This disequilibrium in N suggests that the diamonds in Hypatia were formed in space rather than upon impact on Earth (δNatm15=0‰). All our data are broadly consistent with concentrations and isotopic compositions of noble gases in at least three different types of carbon-rich meteoritic materials: carbon-rich veins in ureilites, graphite in acapulcoites/lodranites and graphite nodules in iron meteorites. However, Hypatia does not seem to be directly related to any of these materials, but may have sampled a similar cosmochemical reservoir. Our study does not confirm the presence of exotic noble gases (e.g. G component) that led Kramers et al. (2013) to propose that Hypatia is a remnant of a comet nucleus that impacted the Earth.

Synthesis of lead vanadate iodoapatite utilizing dry mechanochemical process

For consolidation and subsequent deep geological repository of radioactive 129I, a novel synthesis method of iodine-bearing lead vanadate apatite Pb10(VO4)6I2 was developed. In order to reduce the reaction temperature, a dry mechanochemical process was applied and iodoapatite was successfully synthesized without heating. Calcining the as-synthesized low crystalline specimen at 300°C gave a single-phase with high crystallinity. The obtained powder was consolidated by hot-press sintering at 400°C under uniaxial pressure of 90MPa and submitted to leach tests by immersion into pure water at room temperature. The normalized leach rate of iodine on the first day was about 2.6×10−1gm−2d−1. After 56days of immersion, the iodine leach rate was reduced to less than 1/30 of the initial rate in newly changed water. Iodoapatite specimens in which part of VO43− was substituted with PO43−, Pb10(VO4)4.8(PO4)1.2I2, were also synthesized by the same method.

Radioactive 129I in surface water of the Celtic Sea

Relatively large amounts of radioactive iodine 129I (T 1/2 = 15.7 Ma) have been documented in seawater such as the English Channel, the Irish Sea and the North Sea. Data on the concentration of the iodine isotopes in waters of the Celtic Sea are missing. Aiming to provide first 129I data in the Celtic Sea and compare them with levels in the other close-by seawater bodies, surface seawater samples were analyzed for the determination of 127I and 129I concentrations. The results revealed a high level of 129I in these waters and suggest strong influence by liquid discharges from La Hague and Sellafield reprocessing facilities. 127I concentrations are rather constant while the 129I/127I ratio reaches up to 2.8 × 10−8 (ranging from 10−10 to 10−8), which is 2–4 orders of magnitude higher than pre-nuclear era natural level. Transport of 129I to the Celtic Sea is difficult to depict accurately since available data are sparse. Most likely, however, that discharges originated from La Hague may have more influence on the Celtic Sea 129I concentrations than the Sellafield. Comprehensive surface water and depth profiles 129I data will be needed in the future for assessment of environmental impact in the region.

Correlation between iodine isotopes (129I and 127I) species and marine parameters in the Baltic Sea

Iodine is a bio-intermediate and redox-sensitive element in the oceans and understanding the relationship between transformation of iodine species promotes them as indicators of biochemical cycling in the ecosystems. To gain an insight into the transformation of iodine species, correlations between the iodine species (127IO3−, 127I−, 129I−, 129IO3−) and marine parameters (temperature, salinity, oxygen, total phosphorus, nitrate and ammonium) are assessed here for the Baltic Sea during different seasons. The datasets used cover the periods of August 2006, April 2007 and November 2009. The results indicate that the correlations between radioactive 129I, stable 127I species and marine parameters mainly response to their respective sources as well as oceanographic environments. Also, insignificant correlations of iodine species and nutrients data (total phosphorus, nitrate and ammonium) are observed, suggesting that transformation activity of iodine species in the Baltic Sea is not directly linked to biological production.

Is soil natural organic matter a sink or source for mobile radioiodine ( 129I) at the Savannah River Site?

129I is one of the three major radiation risk contributors to the public as a consequence of past nuclear processing activities at Department of Energy (DOE) facilities. Elevated levels of 129I are present in the surface soils of F-Area of Savannah River Site, which used to be an isotope separation facility for the production of nuclear weapons components. The 129I in soils is thought to be bound predominantly to soil organic matter (SOM). Measurements of stable 127I and radioactive 129I in humic acids (HAs) and fulvic acids (FAs) obtained by five successive alkaline, two glycerol and one citric acid–alkaline extraction, demonstrated that these extractable humic substances (HS) together account for 54–56% and 46% of the total 127I and 129I in the soil, respectively. The remainder was likely bound to residual SOM. The iodine content (μg-I/g-C) generally decreased with each subsequent extract, while 129I/ 127I increased concurrently. The coincident variations in chemical compositions, aromaticity (estimated by UV spectroscopy), functional groups (e.g., aliphatic), degree of humification, relative migration in the hydrophobic interaction column, and molecular weight indicated that: (1) iodine in different HAs was bound to a small-size aromatic subunit (∼10 kDa); (2) the large-size subunit (∼90 kDa), which likely linked the small-size unit through some weak chemical forces (hydrogen bonds, hydrophobic or electrostatic interactions), determined the relative mobility of iodine bound to organic matter; (3) from the strong correlation between iodine content and aromaticity in the HAs, we suggested that iodine incorporation into the SOM via covalent aromatic C–I bond is the key mechanism controlling iodine behavior in this system. However, this relationship is not universal for all fractions of organic matter as evidenced from the different slopes of this relationship at the two sampling sites, as well as from the different relationships for HAs and FAs, respectively. These differences in iodination are due to different SOM molecular sizes, compositions, and availability of preferred iodination sites. 129I in the soil downstream from the contaminated site and near a wetland abruptly dropped below our detection limit (0.5 pCi- 129I/g-soil), which suggests that the high SOM in the plume soil around the 129I-contaminated F-Area might be a natural barrier to scavenge radioiodine released from the nuclear waste repository by forming organo-iodine compounds. Soil resuspension experiments showed that mobile 129I was mostly associated with a low average molecular weight amphiphilic organic carrier (13.5–15 kDa). SOM clearly behaves as a sink for iodine at the Savannah River Site F-Area. However, this work demonstrates that a small fraction of the SOM can also behave as a source, namely that a small fraction that may be readily dispersible under some environmental conditions and presumably release iodine in the organic-colloidal form. This radioiodinated organo-colloid likely can get into the groundwater through infiltration or surface runoff where it might migrate further into the wetlands. Results from this study provide the geochemical basis for future 129I migration controls, remediation, and/or land–groundwater management strategies.

Iodine Isotopes (129I and 127I) in the Baltic Proper, Kattegat, and Skagerrak Basins

Radioactive anthropogenic pollution has raised concerns about the present and future environmental status of the semienclosed Baltic Sea. We here study the distribution and inventory of the anthropogenic radioactive (129)I in water depth profiles collected from 16 sites in August 2006 and 19 sites in April 2007 in the Baltic Proper and related Kattegat and Skagerrak basins. The results reveal considerable differences of (129)I concentration in terms of spatial and temporal variability and expose relatively high concentrations in the deep waters. Variability in the concentration of (127)I, stable natural isotope of iodine, seems to follow changes in the seawater salinity, but in oxygen-poor bottom waters sediment diagenetic release may contribute to the concentration of both isotopes in the water body. Inventory estimates show that (129)I in August 2006 (24.2 ± 15.4 kg) is higher than that in April 2007 (14.4 ± 8.3 kg) within the southern and central Baltic Proper whereas almost a constant load occurs in the Kattegat Basin. Calculated model inventory shows correspondence to empirical data and provides a guideline for future environmental assessment on the impact of (129)I load in the studied region.

Global distribution and long‐term fate of anthropogenic 129I in marine and surface water reservoirs

Since the advent of the nuclear age in the mid‐1940s, the mass of radioactive 129I (t1/2 = 15.7 Myr) circulating in the Earth's hydrosphere has increased nearly fortyfold from its natural background level of 140 kg. Nuclear fuel reprocessing has been by far the major contributor, responsible for releasing 5400 kg of 129I, primarily into the North Atlantic Ocean. Regional and global trends in the distribution of the 129I inventory are elucidated from an examination of more than 600 determinations of 129I in environmental samples from around the world. Because the major point sources are located in Europe and the United States, more than 99% of the present 129I reservoir is distributed in the Northern Hemisphere, where both 129I concentrations and 129I/I ratios in rivers, lakes, and shallow seawater are several orders of magnitude above the preanthropogenic background. Downwelling in the North Atlantic presently provides a major sink for marine 129I; however, marine upwelling along the margins of the Pacific will eventually return part of this anthropogenic input to the ocean surface, where it will find its way back into surface waters and the atmosphere. Iodine‐129 has a long half‐life (15.7 Myr), and consequently, there is also the possibility that climate change will influence the dynamics of iodine transfer in surface reservoirs. We model the effect of a collapse in thermohaline circulation and project a concentration increase of more than 3 orders of magnitude in shallow oceans over the 10,000 years that follow if nuclear reprocessing is to continue at the present rate.

オホーツク海および日本海に胚胎する表層型ガスハイドレート鉱床における間隙水のハロゲンと放射性ヨウ素同位体（&lt;sup&gt;129&lt;/sup&gt;I）の地球化学

Sulfate, halogen, and radioactive 129I concentrations were determined in pore waters associated with massive gas hydrate deposits in shallow sediments along the boundary between the Amurian and Okhotsk plates in the Okhotsk Sea and Japan Sea. Because of the strong biophilic behavior of iodine and weaker behavior of bromine, in contrast to conservative chlorine, in the marine system and the presence of a long-lived radioisotope of iodine (129I), these analyses are useful for determining the age and nature of source organic materials responsible for hydrocarbons, mostly methane, in gas hydrates. Rapid sulfate decreases with depth reflect active methane migration toward the seafloor, particularly around gas hydrate-bearing sites at both locations. While salt exclusion from gas hydrates during crystallization is likely to have resulted in the downward increase of Cl, and potentially Br and I concentrations, gas hydrate dissociation at depth caused a gentle dilution of pore waters. Biophilic Br and I concentrations rapidly increase with depth, reaching 1500 and 400 μM at the core bottom, respectively, indicating that upwelling fluids are enriched in Br and I derived from marine organic materials degraded in deep sediments. The 129I/I ratios thus reflect the potential ages of source formations of iodine and associated methane, providing ∼35 Ma northeast off Sakhalin Island in the Okhotsk Sea and ∼30 Ma in the Umitaka Spur-Joetsu Knoll region in the eastern margin of the Japan Sea. These ages correspond well with the initial activities of the Amurian and Okhotsk plates and the subsequent opening of the Japan Sea, which formed the present geological setting of the northeastern margin of the Eurasian continent. Active plate motions led to the rapid accumulation of organic-rich sediments that are responsible for iodine and methane in gas hydrate occurring along the plate boundary.

129I from the Nuclear Reprocessing Facilities Traced in Precipitation and Runoff in Northern Europe

A huge amount of radioactive 129I has been released into the environment from the nuclear energy industry, atomic weapon tests, and nuclear accidents. In this study, we present weekly and seasonal data on 129I measured in precipitation and runoff of northern Europe during 1998 and 1999. The 129I concentration is at 10(8)-10(9) atoms/L in precipitation and (2-5) x 10(8) atoms/L in runoff water, and it is 3-4 orders of magnitude higher than in the prenuclear era. Snow shows lower 129I concentration than rain, and there is apparently a positive correlation between surface air temperature and 129I. Precipitation chemistry, expressed as the content of Cl, SO4, and NO3 and atmospheric ozone, exhibits weak negative correlation with 129I values. Our 129I data on precipitation suggest significant influence of the northern European atmosphere by the discharges from the nuclear reprocessing facilities at Sellafield and La Hague.

｀１２９´Ｉ法による間隙水の年代測定と石油探鉱への応用

Radioactive 129I method is very useful for petroleum exploration. 129I is naturally produced by cosmic-ray-induced spallation of 129Xe in the upper atmosphere, and by spontaneous fission of 238U in the Earth's crust.129I dating method gives an isolation age of interstitial water from the sea to the sedimentary system. A half-life of 129I is 15.7m.y., so that its application age is restricted between 3 to 90Ma. This is the first and the only geochronologic method to determine the age of fluid in the Tertiary sedimentary basin, while conventional methods are available only for solid or younger fluid. An application to U.S. Gulf Coast basin (Moran et al., 1995) revealed vertical migration of brine from older, deeper sources to present young host formations.Another application of fissiogenic 129I as a tracer in Paleozoic Anadarko basin, Oklahoma (Moran, 1996), to determine the source rock was also presented.129I dating method will be expected to give geochemical evidences about fluid migration in the basin, and resolve the genetics of dissolved-in-water type iodine-natural gas deposits in Neogene to Quaternary sediments in Japan.

Neutron Capture Cross Sections and Resonances of Iodine-127 and Iodine-129

Neutron capture by 127,129I has been measured using the Oak Ridge Electron Linear Accelerator as a pulsed neutron source. Neutron energies were determined by time-of-flight. Resonance peaks were parameterized for radioactive 129I up to 3400 eV and for stable 127I from 2660 to 4260 eV. Average capture cross sections were derived for 129I from 3 to 500 keV and for 129I from 3 to 2200 keV. Over the 3- to 100-keV range, the 129I cross sections average ∼70% of the corresponding 127I cross sections but show much more fluctuation as a function of energy. The greater fluctuation is attributed to the approximately three times wider level spacing.