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Molecular Hydrogen Yields from the α‑Self-Radiolysis of Nitric Acid Solutions Containing Plutonium or Americium
journal contribution
posted on 2018-02-22, 16:22 authored by Colin
R. Gregson, Gregory P. Horne, Robin M. Orr, Simon M. Pimblott, Howard E. Sims, Robin J. Taylor, Kevin J. WebbThe yield of molecular hydrogen,
as a function of nitric acid concentration,
from the α-radiolysis of aerated nitric acid and its mixtures
with sulfuric acid containing plutonium or americium has been investigated.
Comparison of experimental measurements with predictions of a Monte
Carlo radiation track chemistry model shows that, in addition to scavenging
of the hydrated electron, its precursor, and the hydrogen atom, the
quenching of excited state water is important in controlling the yield
of molecular hydrogen. In addition, increases in solution acidity
cause a significant change in the track reactions, which can be explained
as resulting from scavenging of eaq– by
Haq+ to form H•. Although
plutonium has been shown to be an effective scavenger of precursors
of molecular hydrogen below 0.1 mol dm–3 nitrate,
previously reported effects of plutonium on G(H2)α between 1 and 10 mol dm–3 nitric acid were not reproduced. Modeling results suggest that plutonium
is unlikely to effectively compete with nitrate ions in scavenging
the precursors of molecular hydrogen at higher nitric acid concentrations,
and this was confirmed by comparing molecular hydrogen yields from
plutonium solutions with those from americium solutions. Finally,
comparison between radionuclide, ion accelerator experiments, and
model predictions leads to the conclusion that the high dose rate
of accelerator studies does not significantly affect the measured
molecular hydrogen yield. These reactions provide insight into the
important processes for liquors common in the reprocessing of spent
nuclear fuel and the storage of highly radioactive liquid waste prior
to vitrification.
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dose ratesolution acidity causeamericium solutionsaccelerator studiesnitric acid concentrationnitric acidnitrate ionsion accelerator experimentsprecursorH 2Solutions Containing Plutoniumplutonium solutionshydrogen atomtrack reactionsstate waterhydrogen yieldsH aqα- radiolysisnitric acid concentrationsmodel predictionsmodeling resultsMolecular Hydrogen YieldsMonte Carlo radiation track chemistry model
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