F PLUTONIUM IN SEA WATERS. FTC.
K.M. WONG 3
359
Toper aliquot, game hydroxide precipitation is made just after the removal of cesium with ammonium
c material has ‘Ne. molybdophosphate (AMP); tests have shown thatAMP carries no detectable pluto-
1 glass beaker, 334
nium from samples in the concentration range encountered.
sh with acid is ame
The plutonium procedure requires 2-3 days for sediment or ashed organism
spattering loss ‘S@ae samples and 3-4 days for sea water. In routine analvsis two sets of 4 parallel samples
ardized pluto. =
- can be processed in one week bya trained technician.
5
.
.
an
a
A
E. and 0.002 d.p.m. per kg (for 1 kg of fresh organisms): this is based on a two a back: ground uncertainty. a counting time of 48 h. and a counting efficiency of 38 °>.
Chemical recovery
No radiochemical procedure in routine use today is quantitative for fall-out
' plutonium in large samples. Procedures based on “average” chemicalyield from spiked
.
:
analyses to correct for chemical loss are not reliable. Neither accidental nor intrinsic
loss in such procedures can be accurately corrected. Therefore, cyclotron produced
" plutonium-236 tracer, free from other plutonium isotopes, is used in this laboratory
for monitoring recovery of plutonium in analysis.
eee Ate
ae
drain carefully
O ml of 12 M
ER
.
:
ah, i: a
|
Vrate ofabout “3
wall with 8 M
2peat the rinse
Sensitivity
The sensitivity of the procedure is respectively: 0.004 d.p.m. per 1001 of sea
B. water(for a 50-1 sample), 0.02 d.p.m. per kg of sediments (for 100 g of dried sediments).
os
‘.ae
i
elk ren
i NY
ayers
*
5
. 7,
Le ee
ea
aa
aa.
eae A”
Sal
‘ples use 25 ml
a
r samples, use
aoe:
igh an anion-
LS
Tn
i ae
m as described
oft >
ioe
‘2
iloric acid and
se. Collect the
‘na hot plate.
On thirty samples of 5-601 of sea water, analyzed by the present procedure,the
average plutonium recovery was 52+ 18°; even higher recoveries, up to 85°, were
obtained in the smaller volume samples. This compares to 25+ 14% (on 38 samples)
2-3 ml each of yy e by the iron(III) hydroxide method?.
aker with each
: final rinse of
1eSSs,
not plate fora
<er twice with
ca. 100 mg of
about 30 min.
2 of small ion-
ned with 12 M
2 the tube and
ig carefully to
rochloric acid.
cacid and | ml
The average recovery on 75 samples of sediments and ashed organisms was
i. 634+20% (range 30-99%} by the given leaching method. Changing the sample size
e between 50 and 400 g of dried sediments showed no systematic effect on the recovery.
A possible explanation for the low recovery in the iron(III) hydroxide proce& dure is that the plutonium is lost through the formation of plutonium(IV) polymers.
E Plutonium(IV)ions are knownto form polymersvery readily in many solutionsat low
mm acid concentrations*’!®'!”, The chemical behavior of the polymers is significantly
ame. different from that of the ionic forms. Plutonium(IV) polymersare difficult to filter.
a & extract, or coprecipitate because the size and charge of the colloidal particles vary
3 & unpredictably under many conditions.
This procedure avoids the difficulty encountered with plutonium(IV) polyE mers, by reduction of Pu(IV) to Pu(ill) with sulfite and then separating the plutonium
m . {fom sea water by coprecipitation with iron(II) hydroxide. Sodium hydrogensulfite
m. OF gaseoussulfur dioxide are both effective for the depolymerization and reduction of
evaporate [0 3% @ colloidal plutonium in acidic solution!”.
Polymerization loss of plutonium in the analysis of sediments and organisms
as described 3
Is small, if not negligible, because the sample solution is maintained at a high acid
, COncentration throughout the procedure.
Absolute values
ul scheme? for a
+s. The iron(I])
#
The data presented here were all normalized to the disintegration rate, cor-
rected for radioactive decay, of a plutonium-236 solution calibrated at the Health
and Safety Laboratory. USAEC, in June 1965. At present there is some uncertainty
about the absolute value of this solution.
Anal. Chim. Acta, 56 (1971) 355—364
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