Leaching of Actinides from Simulated Nuclear Waste Glass
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Werner. Lute, editor
LEACHING OF ACTINIDES FROM SIMULATED NUCLEAR WASTE GLASS
S.
PICKERING AND C.T. WALKER
Commission of the European Communities, Karlsruhe Establishment, Postfach 2266,
P.
Joint Research Centre,
European Institute for Transuranium Elements,
D-7500 Karlsruhe,
Federal Republic of Germany
OFFERMANN
Hahn-Meitner-Institut fOr Kernforschung Berlin Glienicker Strasse 100, D-1000 Berlin
39
INTRODUCTION The aim of the work was to measure the resistance of simulated nuclear waste glasses to leaching by water and salt solution under the conditions of elevated temperature and pressure.
Of particular interest was the behaviour of Am and
Np.
EXPERIMENTAL Glass preparation The compositions of the glasses investigated, GP 98/12 and C31-3-EC, The GP 98/12 glass
listed in table I. and 2.7 W/o PuO2 . Am-241 by
are
was doped with an additional 4.95 w/oUO2
Of the PuO2 , 8.6 w/o was initially Pu-241 which produced
s-decay.
The C31-3-EC glass was doped with 1 W/o Hp-237 and
0.05 W/o Am-241 as oxides. The glasses were melted in cast in cylindrical graphite moulds.
a platinum crucible and
After annealing at 6000C for 3h the rods
of glass were sectioned to provide specimens
10 mm 0 and -
5 mm high.
Leaching conditions Leaching of the glass was carried out in
stagnant conditions in PTFE lined 5
autoclaves at 200C under air at a pressure of 25-50x10 Pa. Distilled water and NaCl solution saturated at R.T. were the leachants used at leachant volume to specimen surface area ratios
(V/S ratio) of 5 and 10 ml/cm2 (10 ml/cm2 corres-
ponds to the MCC 1 recommendationsý. ment to avoid
A fresh soecimen was used for each measure-
complications due to the repeated drying of the surface layer
that could arise from cumulative measurements on one specimen. Provided by the Institut fOr Nukleare Entsorgungstechnik,
KfK,
Karlsruhe
114
Post-leaching examination A surface layer formed on both types of glass during leaching. contained a significant amount of loosely bound water.
This layer
The layer could be dried
either by heating or by allowing the specimens to equilibrate with dry air at R.T.
The dried layer,
at least on GP 98/12, however,
was capable of reabsorbing
up to 25 W/o of water in only 20 mins from air with 50 % RH.
After drying the
glass at 2001C the surface layer reabsorbed only 80 % of the water that was 0
reabsorbed after drying at : 150 C. The procedure that was adopted to measure the weight of material lost to the leachant therefore was weigh the specimens in dry air after equilibration with dry air at R.T. In the case of glass C31-3-EC doped with Am-241,
the
ct-spectrum of the
specimens was then measured to record the increased Am concentration in the surface layer after leaching.
The weight of the surface layer was determined
by reweighing the glass after removing the layer by scraping. The Np content of the leachant was determined by neutron activation analysis (NAA) after extraction of the Np from the leachant with thenoyltr
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