Preferential removal of Sm by evaporation from Nd–Sm mixture and its application in direct burn-up determination of spent nuclear fuel

Abstract

Rate of evaporation of Sm and Nd from their mixture was studied based on their ion intensities using thermal ionization mass spectrometry. Because of the comparatively larger evaporation rate of Sm, it was found possible to get the isotopic composition of Nd (fission product monitor) free from isobaric interference of Sm isotopes. The decrease in ion intensity of Sm was studied as a function of time and filament temperature. Based on this study, an easy and time effective method for the determination of burn-up of spent nuclear fuel was examined and the results are compared with that obtained by the conventional method. Typical burn-up value obtained for a pressurized heavy water reactor fuel dissolver solution using the direct method by preferential evaporation of Sm is: 0.84 at.%, whereas the one obtained by the use of conventional method is 0.82 at.%. In both the cases, Nd was employed as the fission product monitor.

Resolving isobaric interference in the determination of Nd isotopes using laser ionisation mass spectrometry towards atom percent fission measurements

“…1 The direct loading and preferential evaporation method using TIMS avoids tedious separation procedures and provides an accuracy of ∼3–4% in burn-up measurements. 12 Another conventional fast method, gamma spectroscopy, provides burn-up with an accuracy of about 10%. Though the present method can give the burn-up data with lower accuracy compared to ID-TIMS and MC-ICPMS, it is comparable with direct loading preferential evaporation TIMS and better than gamma spectroscopy.…”

“…Yet another method was demonstrated in our laboratory for a direct burn-up measurement 12,13 using ID-TIMS without any pre-separation and isobaric interference correction. In this method, dissolver solution is directly loaded onto a TIMS sample lament, followed by assay of the burn-up monitor (Nd) and HEs (U, Pu) in a sequential manner by preferential evaporation.…”

Quantitative determination of 137Cs and 90Sr in dissolver solutions without pre-separation by isotope dilution thermal ionization mass spectrometry

“…This was demonstrated for the determination of 148 Nd in the presence of 148 Sm (ref. 22) and 241 Am with 241 Pu. 25 Very recently, a similar method has been adopted by Li et al for the elimination of isobaric interference due to Rb in the measurement of isotopes of Sr in geological samples.…”

“…21 The natural UO 2 fuel was irradiated in a commercial pressurized heavy water reactor (PHWR) at Madras Atomic Power Station (MAPS), also located in Kalpakkam; this fuel was discharged about twenty years back, aer a burn-up of 8100 MWd per ton. 22 The required amount of the above-mentioned dissolver solutions was sampled from the hot cell and diluted to a known volume using 4 M HNO 3 inside a fume hood. Rhenium laments used for experiments were degassed by heating for 2-3 h at a current of 5 A under vacuum till no signal due to ions of interest was observed.…”

“…During the analysis, Cs ions start appearing at 1.1 A of lament current and measurements were carried out at 1.3 A (corresponding lament temperature of 1000 K) 22 to have stable and sufficient ($600 mV) ion intensity for precise isotopic ratio 28 Vapor pressure at melting point (atm) 29 Liquid range (K) (melting point & boiling point) 29 Vapor pressure (atm) at typical lament operating current (A)/temperature (K) 29 measurement. Aer Cs analysis, the lament was maintained at high temperatures (2.1 A/1280 K) for up to 3 h to remove the isobaric interference of Rb in the isotopic ratio (IR) measurement of Sr. At this lament current of 2.1 A, Sr ions appeared (<1 mV), implying that there will be minimum loss of Sr (thus sufficiently available at measuring condition of 2.6 A/1450 K) and quick burning out of Rb from the sample.…”