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Estimate of Gaseous 14Carbon Concentrations Emanating from the Intermediate-Level Vault Disposal Facility

Technical Report ·
DOI:https://doi.org/10.2172/890184· OSTI ID:890184
{sup 14}Carbon-bearing resin waste will be disposed in the Low-Activity Waste (LAW) Intermediate Level Vaults (ILV) located in E-Area on the Savannah River Site (SRS). This waste will be buried in a cementitious environment in the vadose zone, i.e., the subsurface zone above the aquifer. As the resin ages, and equilibrates with slowly infiltrating water, it is expected that the {sup 14}C will partition to the solid, liquid, and gaseous phases. The objective of this task was to estimate the concentration of gaseous {sup 14}C in the waste pore space that is in contact with the resin leachate. The approach used to estimate this value was built largely around data generated from lysimeter studies that were conducted for 9 years. These lysimeters contained the same type of used resins (mixed-bed deionizer resins used in the purification of the heavy water moderator of SRS reactors) as are being disposed in the ILV. During the 9 year period, pore water {sup 14}C leaching concentrations were monitored to provide an excellent estimate of the long-term behavior of {sup 14}C release rates from the resins. Thermodynamic calculations were conducted to calculate {sup 14}CO{sub 2(g)} concentrations. These calculations included the {sup 14}C pore water data from the lysimeter study, and data from a field study that was a natural analogue to a long-term cementitious environment (Khoury et al. 1992). The calculations predicted an extremely low {sup 14}CO{sub 2(g)} concentration of 1.9 x 10{sup -7} Ci/m{sup 3} {sup 14}CO{sub 2(g)} in the air spaces above the resin leachate. This low concentrations is not surprising in light of both laboratory and field observations that concrete acts as a strong sorbent of CO{sub 2(g)}. This calculated {sup 14}CO{sub 2(g)} concentration will now be included in future risk calculations.
Research Organization:
SRS
Sponsoring Organization:
DOE
DOE Contract Number:
AC09-96SR18500
OSTI ID:
890184
Report Number(s):
WSRC-TR-2005-00222
Country of Publication:
United States
Language:
English