Detection of actinides in wound swabs by the measurement of spontaneously emitted characteristic x-rays

In the event of an accident at a nuclear fuel handling facility, the wounds of the affected workers may be contaminated with actinides such as uranium, neptunium, plutonium, and americium. The accidental absorption of actinides from wounds can lead to a significant degree of internal radiation exposure, which can be hazardous to the human body. Although the current approach for identifying actinide contamination is based on the detection of<i>α</i>-particles, the applicability of this approach is reduced for wound contamination due to the<i>α</i>-particles being easily shielded by various components of bodily fluid. Many actinide nuclides spontaneously emit characteristic x-rays during internal conversion after nuclear decay. X-rays are more penetrating than<i>α</i>-particles and may be easily detected even in the presence of blood. Thus, in the current study, the effects of blood on the measurement of<i>α</i>-particles and spontaneously emitted characteristic x-rays were evaluated using model wound swab samples containing human blood along with²⁴¹Am, which exhibits a high emission rate of characteristic x-rays. Unlike in<i>α</i>-particle measurements, no blood effects were observed during the measurement of spontaneously emitted characteristic x-rays. Additionally, blood-free x-ray measurements were performed using model wound swab samples containing²⁴¹Am along with²³⁹Pu +²⁴⁰Pu, which are important nuclides when considering internal exposure to actinides. In the measured spectra, signals derived from plutonium and americium were separated by peak fitting, and the detection limit of plutonium was estimated to be ∼18.8 Bq during a 300 s measurement. Notably, no previously reported methods can detect plutonium in wound swabs with such sensitivity and accuracy without pretreatment. Moreover, the developed approach allows detection using a palm-sized device, thereby reflecting a clear advantage in terms of portability and compactness.