EFFECT OF CARBONATE ON THE SOLUBILITY OF NEPTUNIUM IN NATURAL GRANITIC GROUNDWATER

Cited 4 time in webofscience Cited 0 time in scopus
  • Hit : 286
  • Download : 0
This study investigates the solubility of neptunium (Np) in the deep natural groundwater of the Korea Atomic Energy Research Institute Underground Research Tunnel (KURT). According to a Pourbaix diagram (pH-En diagram) that was calculated using the geocheinical modeling program PHREEQC 2.0, the redox potential and the carbonate ion concentration both control the solubility of neptunium. The carbonate effect becomes pronounced when the total carbonate concentration is higher than 1.5 x 10(-2) M at E(h) = -200 mV and the pH value is 10. Given the assumption that the solubility-limiting stable solid phase is Np(OH)4(am) under the reducing condition relevant to KURT, the soluble neptunium concentrations were in the range of 1 x 10(-9) M to 3 x 10(-9) M under natural groundwater conditions. However, the solubility of neptunium, which was calculated with the formation constants of neptunium complexes selected in an OECD-NEA TDB review, strongly deviates from the value measured in natural groundwater. Thus, it is highly recommended that a prediction of neptunium solubility is based on the formation constants of ternary Np(IV) hydroxo-carbonato complexes, even though the presence of those complexes is deficient in terms of the characterization of neptunium species. Based on a comparison of the measurements and calculations of geochemical modeling, the formation constants for the "upper limit" of the Np(IV) hydroxo-carbonato complexes, namely Np(OH)(y)(CO(3))(z)(4-y-2z), were appraised as follows: log K degrees(122) = -3.0+/-0.5 for Np(OH)(2)(CO(3))(2)(2-), log K degrees(131) = -5.0+/-0.5 for Np(OH)(3)(CO(3))(-), and log K degrees(141) = -6.0+/-0.5 for Np(OH)(4)(CO(3))(2-).
Publisher
KOREAN NUCLEAR SOC
Issue Date
2010-10
Language
English
Article Type
Article
Keywords

WASTE-DISPOSAL; HYDROLYSIS; COMPLEXATION; EQUILIBRIA; BEHAVIOR; OXIDE; KURT

Citation

NUCLEAR ENGINEERING AND TECHNOLOGY, v.42, no.5, pp.552 - 561

ISSN
1738-5733
URI
http://hdl.handle.net/10203/101162
Appears in Collection
NE-Journal Papers(저널논문)
Files in This Item
There are no files associated with this item.
This item is cited by other documents in WoS
⊙ Detail Information in WoSⓡ Click to see webofscience_button
⊙ Cited 4 items in WoS Click to see citing articles in records_button

qr_code

  • mendeley

    citeulike


rss_1.0 rss_2.0 atom_1.0