Use of Calix[4]-bis-2,3-naphthocrown-6 for Separation of Cesium from Pressurized Heavy Water Reactor Simulated High Level Waste Solutions (PHWR-SHLW)

Abstract

Distribution studies on Cs(I) were carried out from pressurized heavy water reactor (PHWR) simulated high level waste (SHLW) solution using calix[4]-bis-2,3-naphtho-crown-6 as the ligand. A mixture of 1:1 nitrobenzene and toluene was evaluated as a suitable diluent. The distribution ratio of Cs(I) increased with the aqueous feed acidity upto 3 M HNO₃ and decreased thereafter due to extraction of hydronium ions. The maximum D_Cs value at ∼3 M HNO₃ suggested the possible application of the system for the recovery of radio-cesium from high level waste solution. The addition of 0.4% (v/v) Alamine 336 (a tertiary amine) facilitated the quantitative stripping of Cs(I) with distilled water. Quantitative extraction of Cs(I) from SHLW containing 0.32 g/L of Cs was observed in five contacts at O/A = 1/2 with 2.5 × 10⁻³ M calix[4]-bis-2,3-naphtho-crown-6. Similarly, quantitative stripping of Cs(I) from the loaded organic phase was achieved in two contacts with distilled water at a volume ratio (O/A) of 2. Selectivity studies carried out using several radiotracers such as ¹⁴³Ce, ¹⁴⁰La, ¹⁴⁰Ba, ¹³⁷Cs, ¹⁰³Ru, ⁹⁹Mo, ^99mTc, ⁹⁷Zr, ⁹¹Sr, etc. indicated excellent selectivity for Cs. The reagent exhibited excellent chemical stability up to a period of six months.

Keywords:

• Calix-crown
• cesium
• nuclear waste management
• solvent extraction

ACKNOWLEDGEMENTS

The authors thank Dr. B. A. Moyer, Chemical Sciences Division, ORNL for his useful suggestions.

Notes

^a Nitrate salt

^b Metal powder

^c Oxide and

^d Chloride salt

^e Taken in place of Pm

^f Taken in place of Rh and

^g Taken in place of Tc.

^a Phase ratio (O/A) in extraction cycle was 1/2.

^b Phase ratio (O/A) in stripping cycle was 2.