The radiochemical purity of a

A. Vasidov, S. Khuzhaev,

and E. A. Markelova

DETERMINATION OF IMPURITY RADIONUCLIDES

IN 

131

Cs SOLUTIONS

---

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