Feasibility of Very Deep Borehole Disposal of US Nuclear Defense Wastes
Name
NFC-127.pdf
Description
NFC-127.pdf
Size
14.42 MB
Format
Adobe PDF
Checksum (MD5)
ab4c92169898137ec6c1ee4c8a97081f
Author(s)
Dozier, Frances E.
Driscoll, Michael J.
Buongiorno, Jacopo
Date Issued
June 2011
Publisher
Massachusetts Institute of Technology. Center for Advanced Nuclear Energy Systems. Nuclear Fuel Cycle Program
Series/Report no.
MIT-NFC;TR-127
Abstract
This report analyzes the feasibility of emplacing DOE-owned defense nuclear waste from
weapons production into a permanent borehole repository drilled ~4 km into granite
basement rock. Two canister options were analyzed throughout the report: the canister
currently used by the DOE for vitrified defense waste and a reference canister with a
smaller diameter. In a thermal analysis, the maximum temperatures attained by the rock
surrounding the waste, waste form, canister, liner, and gaps during the post-emplacement
period were calculated. From this data, simple analytic equations were formed that can be
used to calculate the maximum temperature differences for both defense waste and spent
fuel when one does not want to repeat the analysis. Canister corrosion and waste form
dissolution analyses were performed using Pourbaix diagrams. Finally, the cost and time
for drilling the borehole and emplacing the defense waste were calculated.
The temperature change in the granite is 15.1°C for the reference canister and 45.7°C for
the DOE Canister. The resulting maximum temperature at the bottom of the borehole is
135.1°C (reference canister) and 165.7°C (DOE canister) for the bounding defense waste.
The centerline temperature for the borosilicate glass waste package is approximately
150°C for the reference canister and 207°C for the DOE canister. Because of the
thermodynamic properties, overall corrosion resistance, and reasonable cost, pure copper
was shown to be the best borehole outer canister material. High-chromium stainless steel
could also be a good option for borehole canisters because it has been shown to be highly
corrosion-resistant in environments similar to predicted borehole environments. Cesium
ion was found to have the highest concentration in the borehole environment. However,
the relatively low half life of the most abundant cesium isotope suggests that the cesium
would decay before the canister is breached. For the reference canister, the drilling and
emplacement costs are not expected to exceed $46/kg of vitrified waste and the total
disposal cost was found to be $153/kg of vitrified waste. The total cost of disposal of
defense waste in DOE containers is not expected to exceed $53/kg of vitrified waste.
Based on these analyses, disposal of vitrified defense waste in deep boreholes is expected
to be technically and economically feasible.
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