Working Through Mistakes,
Miscues, and Mishaps in Actinide
Separations
Shane Knockemus
US EPA / NAREL
Montgomery, AL
May 4, 2004
Goal
To give some examples of laboratory goof ups
that I have been victim of, and how to salvage a
successful analysis without having to rerun the
sample from square one.
My examples include using the wrong strip
solutions, omitting important oxidation/reduction
steps, and arranging the cartridges in the wrong
order.
TEVA / TRU separation scheme
Separation Scheme (part 1)
Separation Scheme (part 2,3)
1
2 3
1 2 3
1. Rinse: 2.5 M HNO3
TEVA
2. 9 M HCl
3. 6 M HCl
TEVA
(Th)
(Th)
(Discard) 1
1
2
3
1 Load solution: 2.5 M HNO3/0.5 Al(NO3)3,
ferrous sulfamate, ascorbic acid. Elements
are loaded in the following valence states:
Am+3, Pu+3, Th+4, U+6, (Np+4).
(Am,
Pu,
U)
Th
2 Rinse: 2.5 M HNO3, ferrous sulfamate.
1. Rinse: 2.5 M HNO3
2.5 M/0.1 M NaNO2
2.5 M HNO3
3 Rinse: 2.5 M HNO3.
2. 9 M HCl
3. 4 M HCl
TRU
5
1
TRU
5
(Discard) 1
4
4. 0.1 M HCl/0.1 M H2C2O4
5. 0.1 M (NH4)2C2O4
1 2 3 (Discard)
4
2 3
2 3
U
Pu
2 3
Am
Goof up scenario #1
What went wrong?….I used the U strip solution
(ammonium oxalate) to elute Pu fraction.
Result: Pu and U were eluted together.
Point of realization?
How to salvage usable analyses….If the mistake is
realized before it is too late the Pu. and U may be
precipitated selectively.
It may also be an option to precipitate Pu and U
together if both were precipitated in the presence of
TiCl3. Good resolution is a necessity.
Selective Precipitation Scenario
Sol’n w/ Pu+4 and U+6
Nd+3, HF
filter---save filtrate
NdF3--Pu
Sol’n w/ U+6
reduce volume
Nd+3, TiCl3, HF
NdF3--U
Clean Pu Spectrum
Clean U Spectrum
Precipitating the U fraction from the filtrate of the Pu pptn can diminish
the recovery slightly (10-20%), but results are still within acceptable ranges.
Pu and U Together
With slightly improved resolution, which may be obtained by counting the
sample on a lower shelf, Pu and U could possibly be determined simultaneously.
Goof Up Scenario #2
What went wrong?…ferrous sulfamate was not added
to load solution.
Result: Pu will remain in the +4 valence, and will be
retained and eluted with Th fraction from TEVA.
Point of realization?…If the mistake is realized after the
Th fraction has already been filtered and counted then
the filter must be leached and/or wet ashed to do
chemistry that will enable Pu / Th separation. If the
mistake is realized prior to the precipitation and filtration
of Th, but after the elution of Th (and Pu), the solution
containing the Pu / Th mixture may be used for
subsequent chemistry.
Pu and Th Together
Th / Pu Separation Scheme
Sol’n w/ Th and Pu
SO4-2, BaCl2
BaSO4 (Th, Pu)
EDTA
Ti+3, KOH
Filtrate w/ PuO2+2
HClO4, heat
Ti(OH)3 -- (Th, Pu)
Water, Fe+2, Nd+3, HF
HClO4, water, Nd+3
KMnO4, HF
NdF3 – Th
(save filtrate)
NdF3 -- Pu
Pu-less Th Spectrum
Pu Spectrum
Goof Up Scenario #3
What went wrong?….did not oxidize Pu to +4 valence
prior to elution of Am from TRU.
Result: Pu will remain in +3 valence, and will be eluted
with Am fraction.
Point of realization?…before or after precipitation.
Subsequent chemistry involved in separating Am and
Pu will be the same as the Th / Pu chemistry involved in
“Goof up scenario #2”, whereas the Am will behave the
same as Th.
Pu and Am Together
Pu-less Am Spectrum
Pu Spectrum
Goof Up Scenario #4
What went wrong?….cartridges set up in wrong
order (TRU-TEVA rather than TEVA-TRU).
Result: Everything retained on TRU.
Point of realization?….at the time of
disconnecting tandem arrangement.
Subsequent chemistry involved in obtaining
usable analyses involves a mixture of things
already covered.
Spectrum of Everything Retained on TRU
Everything stripped from TRU with 0.1 M ammonium oxalate
How to Salvage Usable Analyses
Everything on TRU (Am+3, Pu+3, Th+4, U+6).
Am eluted with 4 M HCl.
Pu / Th eluted together with 1 M HCl / 0.1 M
oxalic acid. Pu and Th separated by chemistry
demonstrated in ‘Goof Up Scenario #2’.
U eluted with 0.1 M ammonium oxalate.
Spectra From Goof Up #4
Super Goof Up Scenario
What went wrong?….cartridges were arranged
in the wrong order, ferrous sulfamate reduction
of Pu omitted, sodium nitrite oxidation of Pu
omitted, and wrong stripping solutions were
used.
How To Fix Super Goof Up
Get out of the lab!
Sober up.
Consider a desk job.
Problems Encountered
The behavior and stability of Pu at the +6 valence
proved to be hard to predict at times.
In scenario # 2, 3, and 4 getting Pu to maintain a +6
valence during the NdF3 precipitation of both Th and Am
proved to be difficult and at times not complete.
Don’t co-precipitate samples with CeF3 in the presence
of a strong oxidizer, as it will oxidize the Ce to +4
valence and will render the fluoride precipitation
impossible.
Pu Contamination in Th Spectra
Pu Contamination in Am Spectrum
Acknowledgements
The chemistry involved in obtaining successful
separations was borrowed / learned from David
Sill and Steven Bohrer from RESL in Idaho Falls,
ID.
Conclusions
Mistakes are inevitable as long as humans are
involved.
Don’t be too quick to dump a sample and start
over when a mistake is made. Something can
be learned from most mistakes.
Successful separations are still quite possible in
most situations when mistakes are made.