Dosimetry of indigenously developed (192)Ir high-dose rate brachytherapy source: An EGSnrc Monte Carlo study.

Clinical application using high-dose rate (HDR) (192)Ir sources in remote afterloading technique is a well-established treatment method. In this direction, Board of Radiation and Isotope Technology (BRIT) and Bhabha Atomic Research Centre, India, jointly indigenously developed a remote afterloading machine and (192)Ir HDR source. The two-dimensional (2D) dose distribution and dosimetric parameters of the BRIT (192)Ir HDR source are generated using EGSnrc Monte Carlo code system in a 40 cm dia × 40 cm height cylindrical water phantom. The values of air-kerma strength and dose rate constant for BRIT (192)Ir HDR source are 9.894 × 10(-8) ± 0.06% UBq(-1) and 1.112 ± 0.11% cGyh(-1)U(-1), respectively. The values of radial dose function (gL(r)) of this source compare well with the corresponding values of BEBIG, Flexisource, and GammaMed 12i source models. This is because of identical active lengths of the sources (3.5 mm) and the comparable phantom dimensions. A comparison of gL(r) values of BRIT source with microSelectron-v1 show differences about 2% at r = 6 cm and up to 13% at r = 12 cm, which is due to differences in phantom dimensions involved in the calculations. The anisotropy function of BRIT (192)Ir HDR source is comparable with the corresponding values of microSelectron-v1 (classic) HDR source.

Recovery and purification of 4.66 TBq(126Ci) of 137Cs from a 20-year-old spent sealed source.

An attempt to recover and purify 4.66 TBq(126Ci) of (137)Cs as solution from a 20-year-old doubly encapsulated sealed source containing (137)CsCl was made successfully. The primary capsule was first cut open to retrieve the secondary capsule. The top end of the secondary SS capsule was then cut to render it as an open cylinder and the (137)CsCl pellet inside was dissolved in small aliquots of water. Each aliquot of the (137)CsCl solution was dispensed into glass vials, sealed, assayed and stored. Barium formed during the radioactive decay of (137)Cs was removed by carbonate precipitation. Chloride was removed by heating with HNO(3) and evaporation. About 91.8% of the total activity could be recovered and used subsequently for making brachytherapy sources.

Studies on the nature of the reactions and species involved in potentiometric titrimetric determination of uranium.

The species and reactions involved in the determination of uranium by the Davies and Gray method have been investigated through the behaviour of the various species when present alone or in various combinations in the reaction medium. The studies indicate the formation of Fe(II) and V(III) in the titration system. These two species appear easily prone to oxidation by the titration medium. Probable reasons for the negative bias found when the titration is not completed in the stipulated time period, and for the sharpening of the end-point by the presence of vanadium(IV), are discussed.