ORNL-1816 - the Molten Salt Energy Technologies Web Site

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PERIOD ENDING DECEMBER 10,7954
TABLE 11.1. DECONTAMINATION OBTAINED IN THE FLUORIDE-VOLATILITY
PROCESS BY SCRUBBING UF6
Synthetic ARE fuel, prepared by hydrofluorination of 6 g of irradiated
uranium metal in 67 g of NaF-ZrF4 (56-44 mole X), fluorinated at
65OoC with 40- to 80-fold excess fluorine.
Run 1: UF6 product plus excess fluorine passed through 67 g
of molten NaF-ZrF4 at 65OoC into a dry-ice trap and
then resublimed into second trap.
Runs 2 and 3: UF, product separated from excess fluorine in dry-ice
trap and then volatilized through a C8Fl, still into a
second trap.
Beta Decontami nati on Factors
Activity Run 1 Run 2 Run 3
Over-al I Scrub* Over-a1 I Scrub* Over-al I Scrub*
Gross 4800 2.7 290
Ru 350 2.3 16
Zr 3.2 lo4 6.8 x lo4
Nb 1800 47 1200
1.2 250 2.2
14
4.7 lo4
TRE 2 x 106 2 x 10, 2 105
*Decontamination factor calculated for scrub step alone on basis of activity extracted from scrub material.
Scrubbing the UF, product from the fluorination
and sublimation steps with fluorocarbon (C,Fl,)
did not improve the decontamination (runs 2 and 3,
Table 11.1). Approximately 9 g of UF, sublimed
from a fluorination run, was passed into the bottom
of a C,F, distillation column (0.5 in. in diameter
by 14 in. high, packed with t2-in. nickel Fenske
helices) that was operating at full reflux at about
gas
had to be refluorinated from the NaF bed at 65OOC
before being trapped. However, the gross decon-
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tamination factors in the two fractions were of the
same order, that is, 2 x lo3. The uranium loss on
the NaF was only 0.01%. Two experiments were
then performed with 30-9 beds of 20- to 40-mesh
NaF held at 65OOC to eliminate the refluorination
step (runs 2 and 3, Table 11.2). The results in
both tests showed high absorption of ruthenium
and niobium beta activities, and the over-till gross
4
beta decontamination factor was greater than 10 .
eral, 1 to 10% of
Nearly all the niobium activity was accounted for
in the reactor and fused salt, while 7555 of the