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)

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 DCs 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.