software; the energy resolution was 1.8 keV on the 1332 keV line and 165 eV on the 5.9 keV line. The detection efficiency
for
γ
- and x-rays was measured using graduated sources from the OSGI set and was 13, 7.4, 3.7, and 1.8% on the 121, 302.9,
661, and 1173 keV lines, respectively, for the high-purity germanium and 0.68, 0.74, 0.6, and 0.26% on the 20, 26, 30, and
46 keV lines, respectively, for the silicon-lithium detector. The activity of the radionuclides was determined from the relation
A =
sk
1
k
2
/ t
α
eff
η
γ
,
(1)
where s is the area of the total absorption peak, in counts; k
1
and k
2
are the correction to the measurement geometry and
aliquots, respectively; t is the measurement time, in sec;
α
eff
is the detection efficiency, in arb. units;
η
γ
is the emission inten-
sity of
γ
- and x-rays, in arb. units. The standard error of the measurement method was no more than ±10%.
The barium targets (m
Ba
= 500 mg) were hermetically sealed in quartz ampuls, placed in an aluminum container
block, and irradiated in a vertical channel of a VVR-SM reactor with thermal neutron flux density 3.5·10
13
sec
–1
·cm
–2
for
120 h. After irradiation, they were allowed to stand for 10 days in order to accumulate the maximum amount of the desired
131
Cs and for impurity radionuclides with
T
1/2
< 1 day to decay, and then it was dissolved in 1–1.5 M hydrochloric acid. After
the barium compounds were completely dissolved, aliquots with k
2
= 1500–2500 were extracted from the solutions for qual-
itative and quantitative analysis. About 30
131
Ba
γ
lines and seven
133
Ba with
γ
-ray yield 0.042–48.4% and 0.46–61.6%,
respectively, were detected when measuring the activity of the aliquots over 1000 sec in high-purity germanium detector [5].
The following barium x-ray lines were identified: K
α
= 30.84 and K
β
= 34.96, corresponding to the transition
131
Ba
→
131
Cs
and K
α
= 29.67 and K
β
= 33.61 keV for the transition
131
Cs
→
131
Xe. It was established experimentally that it is difficult to
determine the presence of other radionuclides in barium solutions, since the activity of matrix
131
Ba and
133
Ba predominates.
131
Cs was separated from the
131
Ba bulk by precipitating Ba
2+
in the form of carbonate in a weakly alkaline medium
followed by filtering. Traces of barium ions in the filtrate were removed, after the solution was evaporated to the minimum
volume, by adding 5 M solution of sulfuric acid. Since
131
Cs is a daughter radionuclide, after 8–10 days, which are neces-
sary to reach radioactive equilibrium between
131
Ba and
131
Cs, the barium carbonate residue obtained as a result of primary
Isotope (abundance, %)
Nuclear reaction
Radionuclide
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