Plutonium Impurities Research Articles

Integrated approaches for reducing sample size for measurements of trace elemental impurities in plutonium by ICP-OES and ICP-MS

This study has demonstrated that bulk plutonium chemical analysis can be performed at small scales (< 50 mg material) through three case studies. Analytical methods were developed for ICP-OES and ICP-MS instruments to measure trace impurities and gallium content in plutonium metals with comparable or improved detection limits, measurement accuracy and precision. In two case studies, the sample size has been reduced by 10×, and in the third case study, by as much as 5000×, so that the plutonium chemical analysis can be performed in a facility rated for lower-hazard and lower-security operations.

Optical Fibers for Remote Spectrometry of Alkali Elements in the dc Arc

An optical fiber cable is designed, characterized, and applied to the remote spectrometric analysis of alkali elements as impurities in plutonium by dc arc emission. The analytical performance of the dc arc/optical fiber/polychromator system is tested by the establishment of analytical working curves for sodium, potassium, and rubidium from a set of standards. Accuracy, determined by the use of control samples of known concentration, is found to be 10% or better. The new analytical system provides improvement in both accuracy and efficiency compared to the previously used spectrographic technique.

“Cathode Region” Method for the Spectrochemical (dc Arc) Determination of Impurities in Plutonium

A direct spectrochemical method for 47 impurities in plutonium was developed by exposing on the photographic plate only the cathode region instead of the whole arc gap. The dc plasma parameters were calculated for the two matrices, PuO2 and U3O8. This method enables the measurement of similar parameter values for uranium and plutonium. The matrix factor was used for determination of impurities in PuO2, with U3O8 as standard matrix for the analytical curves (log I/log C). The reproducibility of the method is within ±20% and the detection limits of the impurities are in the concentration range of a few parts per million.

Exploring the transformation behaviour of the allotropes of plutonium

The hysteresis between temperatures of transformation on heating and cooling in the lower three allotropie transformations of plutonium is due to an unusual sluggishness of the transformation mechanism, which is reflected in various ways in the individual transformations. A study of this sluggishness gives 112 ± 1° C and 184 ± 2°C for the equilibrium temperature of the αaiβ & βaiγ transformations respectively. Impurities in plutonium increase the time constant of the transformation mechanism still further. This is a possible source of error in using alloy constitution diagrams obtained by the usual methods as sources of thermodynamic data. Experimental evidence suggests that the latent heat of the δ → δ′ transformation is about 100 cal/g-atom, in disagreement with previous results. The “maximum rates” results used to find the αaiβ and βaiγ equilibrium temperatures show more scatter than that expected from the intrinsic error of the measuring system. An effect at about 280°C, observed while investigating possible causes for this scatter, may have a bearing on the “elbow” effect noticed in the δ → γ transformation by several workers 3–5,8.