PENGUKURAN BERAT RADIONUKLIDA 137Cs DALAM LARUTAN PELAT ELEMEN BAKAR U3Si2/Al DENSITAS 4,8 gU/cm3 PASCA IRADIASI DENGAN METODE KOLOM KROMATOGRAFI

Abstract

The burn up value of the fuel is one of the parameters that must be known in the post-irradiation examination. The determination of burn up aims to determine the performance of U₃Si₂/Al fuel after being used in the reactor. One of the isotops that can be used as an indicator of burn up is ¹³⁷Cs because it has a long half-life (T_1/2) of 30.17 years with a fission yield of 6.26%. Therefore, in this study, a separation was carried out to determine the amount of ¹³⁷Cs in the U₃Si₂/Al fuel solution post irradiation using the cation exchange column method using zeolit from Lampung along with its recovery rate. The solution of irradiated U₃Si₂/Al fuel from Top (T), Middle (M), and Bottom (B) position, was each pipetted in a duplicate manner (duplo) in an amount of 50 µL and added with 2 mL of 0.1 M HNO₃. The solutions were then measured activity using a gamma spectrometer to obtain the initial weight of ¹³⁷Cs radionuclide. The solution was then inserted into a chromatography column containing 700 mg of zeolit Lampung and allowed to flow under vacuum condition. The separation results showed that ¹³⁷Cs was bound to the zeolit in the form of ¹³⁷Cs-zeolit solid phase, while other isotops remained in the liquid phase. The solid ¹³⁷Cs-zeolit and ¹³⁷Cs in the supernatant were then measured with a gamma spectrometer to determine the weight of ¹³⁷Cs bound to the zeolit. The measurement results showed that the average initial weight of ¹³⁷Cs (before separation) were 7.49 × 10^-3 µg/gFEP and dan 6.97 × 10^-3 µg/gFEP for T1 and T2 from top section, 10.50 × 10^-3 µg/gFEP for M1 from Middle section, and dan 8.43 × 10^-3 µg/gFEP and 8.76 × 10^-3 µg/gFEP for B1 and B2 from Bottom section, respectively. After separation, the average weight of ¹³⁷Cs were 7.43 × 10^-3 µg/gFEP and 6.82 × 10^-3 µg/gFEP for T1 and T2, 10.10 × 10^-3 µg/gFEP for M1, and 8.32 × 10^-3 µg/gFEP and 8.41 × 10^-3 µg/gFEP for B1 and B2, respectively. From the weight of ¹³⁷Cs before and after separation, the average separation recovery with the cation exchange chromatography column method using zeolit was obtained at 97.748%. This recovery value indicates that zeolit Lampung is highly selective for absorbing ¹³⁷Cs in the solution of irradiated U₃Si₂/Al fuel.