Ba isotopic signature for early differentiation between Cs and Ba in natural fission reactors

Hidaka, Hiroshi; Gauthier-Lafaye, F.

doi:10.1016/j.gca.2008.06.005

Cited by 9 publications

(11 citation statements)

References 20 publications

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“…We assumed that Cs was being continuously lost from the uraninite during reactor operation since Cs is not compatible with the uraninite matrix (9). Our estimate was shorter than the 20-y timescale previously postulated (25). The isochrons in Fig.…”

Section: Significancecontrasting

confidence: 52%

“…Cesium is mobile, and 137 Cs accounts for a major portion of reactor waste activity on the timescale of several generations, while 135 Cs remains active long after. Earlier bulk isotopic work identified the presence of radiogenic Ba within the RZs, indicating that differentiation between Ba and Cs occurred on the order of 20 y following criticality and that fissionogenic 135 Ba and 137 Ba chemically behaved as Cs (9,25,26).…”

Section: Significancementioning

confidence: 99%

See 1 more Smart Citation

Discovery of fissionogenic Cs and Ba capture five years after Oklo reactor shutdown

Groopman

Willingham

Meshik

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Understanding the release and sequestration of specific radioactive signatures into the environment is of extreme importance for long-term nuclear waste storage and reactor accident mitigation. Recent accidents at the Fukushima and Chernobyl nuclear reactors released radioactive Cs andCs into the environment, the former of which is still live today. We have studied the migration of fission products in the Oklo natural nuclear reactor using an isotope imaging capability, the NAval Ultra-Trace Isotope Laboratory's Universal Spectrometer (NAUTILUS) at the US Naval Research Laboratory. In Oklo reactor zone (RZ) 13, we have identified the most depleted natural U of any known material with a U/U ratio of 0.3655 ± 0.0007% (2σ). This sample contains the most extreme natural burnup in Sm,Eu, Gd, andGd, which demonstrates that it was sourced from the most active Oklo reactor region. We have discovered that fissionogenic Cs and Ba were captured by Ru metal/sulfide aggregates shortly following reactor shutdown. Isochrons from the Ru aggregates place their closure time at 4.98 ± 0.56 y after the end of criticality. Most fissionogenic Ba andBa in the Ru migrated and was incorporated as Cs over this period. Excesses in Ba in the Ru point to the burnup ofCs. Cesium and Ba were retained in the Ru despite local volcanic activity since the reactor shutdown and the high level of activity during reactor operation.

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Section: Significancecontrasting

confidence: 52%

Section: Significancementioning

confidence: 99%

Discovery of fissionogenic Cs and Ba capture five years after Oklo reactor shutdown

Groopman

Willingham

Meshik

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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“…Subsequently a large number of studies on Ba isotope anomalies in extraterrestrial material were published (e.g., McCulloch and Wasserburg, 1978;Hidaka et al, 2003;Ranen and Jacobsen, 2006;Andreasen and Sharma, 2007). In addition, Ba from the unique 2 Ga-old natural fission reactor of Oklo and Bangombé was analyzed for fissiogenic Ba isotope anomalies (e.g., Hidaka et al, 1993;Hidaka and Gauthier-Lafaye, 2008). The decay of Ba isotopes was investigated in barites (Pujol et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Barium isotope fractionation in the global barium cycle: First evidence from barium minerals and precipitation experiments

et al. 2010

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In this study, we present first results from an ongoing investigation on the stable barium (Ba) isotope fractionation in the natural barium cycle. Stable Ba isotope signatures of international IAEA reference materials (synthetic barium sulfate, IAEA-SO-5, -6, and barium carbonate, IAEA-CO-9), natural Ba minerals and experimental Ba precipitates have been analyzed as a first approach to evaluate potential discriminating processes in the global geochemical barium cycle. Ba = − 0.5‰ was found in a diagenetic barite sample from ODP Leg 207. The observed natural discriminations are clearly larger than the analytical uncertainty of the stable isotope measurements, indicating significant isotope discrimination in the natural barium cycle. Precipitation experiments from aqueous barium chloride solutions at temperatures of~21°C and 80°C indicate that the light Ba isotope is enriched in pure barium carbonate and barium sulfate compared to the aqueous solution. A maximum isotope fractionation of − 0.3‰ is observed for both barium carbonate and sulfate, that -in the case of BaCO 3 -seems to be influenced by precipitation rate and/or the aqueous speciation, but less by temperature.

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“…In the case of the Oklo natural reactor, the short-lived radioisotope 137 Cs (t 1/2 = 30 years) as well as 135 Cs can be used to consider the Cs/Ba differentiation timing in spite of the large difference in half-lives between 135 Cs and 137 Cs. The data suggest the occurrence of early differentiation between Cs and Ba within 20 years after the production of fissiogenic Cs ( 135 Cs and 137 Cs) in the reactors31.…”

Section: Discussionmentioning

confidence: 80%

“…Ba isotopic studies of the natural fission reactor, Oklo, in the east of Gabon in central Africa, may provide a hint to consider the situation of Cs/Ba differentiation under aqueous activity3031. In the Oklo natural reactor, various types of radioisotopes were produced by fission 2.0 billion years ago, and the remnants of the fissiogenic isotopes can still be detected as isotopic anomalies associated with enrichment or depletion of the decay products.…”

Section: Discussionmentioning

confidence: 99%

Radioactive Cs capture in the early solar system

Hidaka

Yoneda

2013

Sci Rep

Self Cite

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Barium isotopic compositions of primitive materials in the solar system are generally affected by s- and r-process nucleosynthetic components that hide the contribution of the isotopic excess of 135Ba formed by decay of radioactive 135Cs. However, the Ba isotopic composition of the chemical separates from chondrules in the Sayama CM2 chondrite shows an excess of 135Ba isotopic abundance up to (0.33 ± 0.06)%, which is independent of the isotopic components from s- and r-process nucleosyntheses. The isotopic excesses of 135Ba correlate with the elemental abundance of Ba relative to Cs, providing chemical and isotopic evidence for the existence of the presently extinct radionuclide 135Cs (t1/2 = 2.3 million years) in the early solar system. The estimated abundance of 135Cs/133Cs = (6.8 ± 1.9) × 10−4 is more than double that expected from the uniform production model of the short-lived radioisotopes, suggesting remobilization of Cs including 135Cs in the chondrules of the meteorite parent body.

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Ba isotopic signature for early differentiation between Cs and Ba in natural fission reactors

Cited by 9 publications

References 20 publications

Discovery of fissionogenic Cs and Ba capture five years after Oklo reactor shutdown

Discovery of fissionogenic Cs and Ba capture five years after Oklo reactor shutdown

Barium isotope fractionation in the global barium cycle: First evidence from barium minerals and precipitation experiments

Radioactive Cs capture in the early solar system

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