Reliable determinations of plutonium isotope ratios are required in the nuclear field. Thermal ionisation mass spectrometry (TIMS) is used for this purpose. Commercially available TIMS instruments cannot distinguish between ²⁴¹Am and ²⁴¹Pu. A purification step before measurement to remove americium from plutonium solutions is required. Nevertheless, the amount of ²⁴¹Am in-growth due to ²⁴¹Pu decay (half-life 14.3 years) in the time between plutonium purification and TIMS measurements can be significant for an accurate determination of the ²⁴¹Pu/²³⁹Pu isotope ratio. This paper presents a method, with a focus on nuclear safeguards, to correct for the ²⁴¹Am in-growth after plutonium purification. In addition, the method provides an estimate for the americium ionisation efficiency to allow an even more accurate determination of the ²⁴¹Pu/²³⁹Pu isotope ratio.

核领域需要可靠地测定钚同位素比率。热电离质谱 (TIMS) 用于此目的。市售的 TIMS 仪器无法区分²⁴¹ Am 和²⁴¹ Pu。需要在测量前进行纯化步骤，以从钚溶液中去除镅。尽管如此，在钚纯化和 TIMS 测量之间的时间内，由于²⁴¹ Pu 衰变（半衰期为 14.3 年）而导致的²⁴¹ Am 向内生长的量对于准确确定²⁴¹ Pu/ ²³⁹ Pu 同位素比可能具有重要意义。本文提出了一种以核保障为重点的方法，以纠正²⁴¹钚纯化后生长。此外，该方法还提供了对镅电离效率的估计，从而可以更准确地确定²⁴¹ Pu/ ²³⁹ Pu 同位素比值。