The X-10 nuclear reactor was built at the Clinton Engineering Works in Oak Ridge, Tennessee, USA, as the world’s first Pu production reactor. Operation commenced in November 1943, producing Pu on the gram-scale for the first time. A 61.1 mg sample of ²³⁹Pu has been identified at Los Alamos National Laboratory containing multiple forensic signatures consistent with production from the X-10 reactor in early 1944, when the first samples of reactor-produced Pu were shipped from X-10 to Los Alamos. Our nuclear forensics investigation included Pu isotopic analysis, chronometry, X-10 reactor physics simulations, and trace metal analyses. This historic sample has been determined to be among the oldest reactor-produced Pu reported in the literature and is among the first 1.4 kg of Pu ever produced.

X-10 核反应堆在美国田纳西州橡树岭的克林顿工程工厂建造，是世界上第一个生产 Pu 的反应堆。1943 年 11 月开始运营，首次以克级规模生产 Pu。洛斯阿拉莫斯国家实验室发现了一个 61.1 毫克的²³⁹ Pu样品，其中包含多个法医签名，与 1944 年初 X-10 反应堆的生产一致，当时反应堆生产的第一批样品从 X-10 运往洛斯阿拉莫斯. 我们的核取证调查包括 Pu 同位素分析、计时法、X-10 反应堆物理模拟和痕量金属分析。该历史样品已被确定为文献中报道的最古老的反应堆生产的 Pu 之一，并且是有史以来生产的首批 1.4 公斤 Pu 之一。