Content of Long-Lived Radionuclides of Carbon-14 and Chlorine-36 in Reactor Graphite and in the Biosphere (Is there a Problem with Carbon-14 and Chlorine-36 when It Comes to the Processing of Reactor Graphite?)

The system C–Al–TiO2 is of considerable interest for the processing of irradiated reactor graphite waste with the retention of biologic hazardous carbon-14. Investigations of this system were conducted both theoretically and experimentally. Previously, the thermodynamic calculations of the phase composition of resulting end product were performed for a wide variety of components content in the system being investigated. These simulation results have been supported by XRD-analysis of produced specimens. The experimental processing of reactor graphite was conducted by the use of self-sustaining reactions in C–Al–TiO2 mixtures. A search of modifier additives was performed to perfect end product properties. Test specimens were produced by mass ranging from 0.2 to 3 kg in the argon atmosphere. Various techniques were applied to characterize the produced specimens. The compressive strength of specimens of doped carbide-corundum matrices synthesized ranged from 7 to 18 MPa. The carry over of Cs-137 and Sr-90 during synthesis reaction was about 3% wt. The leachability attained of Cs-137 and Sr-90 from specimens was around 10−5 g/(cm2.day). The carbon-14 is combined in the end product in chemically and thermic stable titanium carbide. The carry-over of the carbon combined in carbon monoxide from the reacting mixtures during exothermic process was less than 1% wt. This corresponds roughly to up 0.01% wt. of the carbon-14 inventory, which can be present in the irradiated reactor graphite.

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Simplified solid-state scintillation counting on glass microfiber medium in plastic bag for hydrogen-3, carbon-14, and chlorine-36 in biological and organic materials

Analytical Chemistry ◽

10.1021/ac50157a087 ◽

1967 ◽

Vol 39 (14) ◽

pp. 1911-1912 ◽

Cited By ~ 8

Author(s):

Gopi Nath. Gupta

Keyword(s):

Solid State ◽

Organic Materials ◽

Scintillation Counting ◽

Carbon 14 ◽

Plastic Bag ◽

Chlorine 36

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Investigation of reactor graphite processing with the carbon-14 retention.

MRS Proceedings ◽

10.1557/proc-757-ii3.13 ◽

2002 ◽

Vol 757 ◽

Author(s):

M. I. Ojovan ◽

O. K. Karlina ◽

V. L. Klimov ◽

G. A. Bergman ◽

G. Yu. Pavlova ◽

...

Keyword(s):

Thermodynamic Simulation ◽

Xrd Analysis ◽

Carbon 14 ◽

Reactor Graphite ◽

Reacting Mixtures ◽

Strong Candidate ◽

Run Up ◽

Carbide Ceramics ◽

Carry Over ◽

Experimental Processing

ABSTRACTThe system C – Al – TiO2 has been demonstrated to be a strong candidate for the processing of irradiated reactor graphite waste with the retention of biologic hazardous carbon-14 in chemically and thermal stable corundum-carbide ceramics. The corundum-carbide ceramics is obtained from the powdered precursors blend through self-sustaining thermochemical reactions. Investigations of the system C – Al – TiO2 were carried out both theoretically and experimentally. The refining thermodynamic calculations of the phase composition of resulting end product were performed for a wide variety of components content in the system being investigated. Aluminium oxycarbides production was taken into account in the calculations. Thermodynamic functions of aluminium oxycarbides Al4O4C and Al2OC have been calculated for this purpose using currently available literature evidences and own assessments of missing data. On the basis of thermodynamic simulation the proportions of the source substances were determined, which result in the aluminium oxycarbides production. These simulation results have been supported by XRD-analysis of produced specimens. The experimental processing of reactor graphite was conducted by the use of self-sustaining reactions in C – Al – TiO2 powder blends. Test specimens were produced by mass ranging from 0.1 to 3 kg in the argon atmosphere. Various techniques were used to characterize the produced specimens. The compressive strength of specimens of corundum-carbide matrices produced ranges from 7 to 13 MPa. The leaching rates of Cs-137 and Sr-90 from specimens ranged between 10-4 and 10-5 g/(cm2.day) respectively. The carry-over of the carbon combined in carbon monoxide from the reacting mixtures during exothermic process may run up to 1% wt. that appropriates roughly to less than 0.01% wt. of the carbon-14 in the irradiated reactor graphite.

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Helium-4 characteristics of groundwaters from Central Australia: Comparative chronology with Chlorine-36 and Carbon-14 dating techniques

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2006.06.682 ◽

2006 ◽

Vol 70 (18) ◽

pp. A338

Author(s):

Justin T. Kulongoski ◽

David R. Hilton ◽

Stephen Hostetler ◽

Richard Cresswell ◽

Gerry Jacobson

Keyword(s):

Carbon 14 ◽

Helium 4 ◽

Central Australia ◽

Chlorine 36

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An approach to modelling the impact of 14C release from reactor graphite in a geological disposal facility

Mineralogical Magazine ◽

10.1180/minmag.2015.079.6.24 ◽

2015 ◽

Vol 79 (6) ◽

pp. 1495-1503 ◽

Cited By ~ 6

Author(s):

Charalampos Doulgeris ◽

Paul Humphreys ◽

Simon Rout

Keyword(s):

Near Field ◽

Significant Proportion ◽

Reactor Core ◽

Microbial Reduction ◽

Gaseous Species ◽

Geological Disposal ◽

Carbon 14 ◽

Reactor Graphite ◽

Disposal Facility ◽

The Impact

AbstractCarbon-14 (C-14) is a key radionuclide in the assessment of a geological disposal facility (GDF) for radioactive waste. In the UK a significant proportion of the national C-14 inventory is associated with reactor-core graphite generated by the decommissioning of the UK's Magnox and AGR reactors.There are a number of uncertainties associated with the fate and transport of C-14 in a post-closure disposal environment that need to be considered when calculating the radiological impacts of C-14-containing wastes. Some of these uncertainties are associated with the distribution of C-14-containing gaseous species such as 14CH4 and 14CO2 between the groundwater and gaseous release pathways. As part of the C14-BIG programme, a modelling framework has been developed to investigate these uncertainties. This framework consists of a biogeochemical near-field evolution model, incorporating a graphite carbon-14 release model, which interfaces with a geosphere/biosphere model. The model highlights the potential impact of the microbial reduction of 14CO2 to 14CH4, through the oxidation of H2, on C-14 transport. The modelling results could be used to inform the possible segregation of reactor graphite from other gasgenerating wastes.

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Preliminary investigation of 14C migration from RBMK-1500 reactor graphite disposed of in a potential geological repository in crystalline rocks in Lithuania

Radiocarbon ◽

10.1017/rdc.2018.139 ◽

2018 ◽

Vol 60 (6) ◽

pp. 1839-1848

Author(s):

Dalia Grigaliuniene ◽

Povilas Poskas ◽

Raimondas Kilda ◽

Asta Narkuniene

Keyword(s):

Nuclear Power ◽

Near Field ◽

Preliminary Investigation ◽

Crystalline Rocks ◽

Near Surface ◽

Carbon 14 ◽

Reactor Graphite ◽

Irradiated Graphite ◽

Geological Repository ◽

Order Of Magnitude

ABSTRACTThere are two units with RBMK-1500 type reactors at the Ignalina Nuclear Power Plant (Ignalina NPP) in Lithuania where graphite was used as a neutron moderator and reflector. These reactors are now being decommissioned, and Lithuania has to find a solution for safe irradiated graphite disposal. It cannot be disposed of in a near surface repository due to large amounts of 14C (radiocarbon, carbon-14); thus, a deep geological repository (DGR) is analyzed as an option. This study had the aim to evaluate 14C migration from the RBMK-1500 irradiated graphite disposed of in a potential DGR in crystalline rocks taking into account the outcomes of the research performed under the collaborative European project CAST (CArbon-14 Source Term) and to identify the potential to reduce the conservatism in the assumptions that was introduced in the lack of data and led in the overestimated 14C migration. The information gathered during the CAST project was used to model 14C transport in the near field by the water pathway and to perform uncertainty analysis. The study demonstrated that more realistic assumptions could reduce the estimated 14C flux from the near field by approximately one order of magnitude in comparison with the previous estimations based on very conservative assumptions.

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