Abstract
An HPLC method is presented for the separation and determination of lanthanides (Lns), thorium (Th), uranium (U) and plutonium (Pu) from irradiated (Th, Pu)O2. Individual separation of Lns, Th, U and Pu is a challenging task becauseof 1) lanthanideshavingsimilar physical and chemical properties, 2) presence of complex matrix like irradiated fuel and 3) the co-existence of multiple oxidation states of Pu. Different procedures were developed for separation of individual lanthanides and actinides.The individual lanthanides were separated on a dynamically modified reversed phase (RP) column using n-octane sulfonic acid as an ion interaction reagentand employingdual gradient(pH and concentration) of α-hydroxyisobutyric acid (HIBA). In order to improve the precision on the determination of Lns, terbium (Tb) was used as an internal standard. The method was validated employing simulated high level liquid waste. Concentrations of lanthanides viz. lanthanum (La) and neodymium (Nd) in the dissolver solution were determined based on their peak areas. Th, U and Pu were separated on a RP column using mobile phase containing HIBA and methanol. Since Pu is prone to exist in multiple oxidation states, all the oxidation states were converted into Pu (IV) using H2O2 in 3M HNO3. Under the optimized conditions, Pu(IV) eluted first followed by Th and U. The concentrations of Th, U and Pu were determined by standard addition method andwere found to be 1.10 ± 0.02 mg/g, 5.3 ± 0.3 μg/g and 27 ± 1 μg/g, respectively, in the dissolver solution of irradiated fuel. These values were in good agreement with the concentration of Th determined by biamperometry and those of U and Puby isotope dilution thermal ionization mass spectrometry.
Highlights
The Indian nuclear program envisages the effective utilization of thorium (Th) as a fertile material for the sustained production of electricity in the country [1]
Chromatographic Behavior of Lanthanides, Th, U and Pu In solution, under the chromatographic conditions, lanthanides exist in III oxidation state whereas Th and U exist in IV and VI states, respectively
Retention behaviors of Lns and Pu(III) is different from Th(IV), U (VI), Pu(VI) and Pu(IV) when α-HIBA was used as an eluent on reversed phase (RP) column [21].With α-HIBA, Lns and Pu(III) form mainly cationic complexes which are different from those formed by Th, U, Pu(VI) and Pu(IV) [25]
Summary
The Indian nuclear program envisages the effective utilization of thorium (Th) as a fertile material for the sustained production of electricity in the country [1]. Mixture of (Th, 233U) O2 and (Th, 239Pu) O2 was proposed as fuel for advanced heavy water reactor (AHWR) to make system self-sustaining in 233U [2,3]. Pu)O2 fuel clusters were irradiated in the Pressurized Water Loop (PWL) of CIRUS reactor, BARC. The implementation of mixed oxide based fuel cycle requires development of methodologies for evaluating the performance of the fuel in the reactor. Burn-up is an important parameter for nuclear fuel development, fuel management and fuel performance analysis [4,5]. Burn-up is defined as the atom percent fission of heavy element (mass ≥ 225) during its life time in the reactor. Radiochemical and chemical analysis methods are generally used for burn-up determination of irradiated nuclear fuels [6]. The destructive method involved dissolution of fuels followed by individual separation and determination of IJAMSC
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