ORNL-4191 - the Molten Salt Energy Technologies Web Site

2
a STATIC
-~
-0 AGITATED
A AVERAGE
A SALT (AS BI EQUIVALENT)
(()' I .......... ...... ~~1 ~
I I 1
..... 1 ........ ~ ....
1 -
150
I-
..... -1- 1
0 10 20 30 40 50 60 70
TIME (days1
Fig. 12.3. Stability of Solutions of Protactinium in Bismuth.
Behavior of this sort cannot be explained by a
simple mechanism. However, slow reversible ad-
sorption (negligible at high temperature) followed by
irreversible diffusion into a solid (but oxidizable)
phase is consistent with the data. This phase does
not seem to be the thorium-bismuth intermetallic.
After the cooling step, the metal samples, which were
taken with an open dipper, tended to show more prot-
actinium when the liquid metal was being stirred
vigorously, suggesting that the protactinium was on
a dispersed phase rathcr than on the vessel walls.
Strips of various metals were immersed for 5 min
and 2 hr in the bismuth to see how much protactinium
was adsorbed; results are shoyqil in Table 12.1. When
the metals were dipped directly into bismuth, niobium
picked up the most protactinium, with beryllium, iron,
and carbon picking up less (carbon, milch less). Ad-
sorption on iron reached about onethird of its 2-hr