[M-ZZ45] Frontiers in geochemistry: discussing its appeal and future prospects

[MZZ45-P11] Challenges of measuring ultra-trace ²³⁷Np in the hydrosphere

Yuma Sakakieda¹, Akihisa Nakajima¹, Ayumu Nagai², Hiroyuki Hosokawa², Akihiko Yokoyama², Hiromitsu Haba³, Akihiro Nambu³, Yudai Shigekawa³, Jian Zheng⁴, Noriaki Seko⁴, Hiroyuki Hoshina³, Hain Karin⁵, Andreas Wiederin⁵, Shinya Yamasaki¹, Yuichi Takaku¹, *Aya Sakaguchi¹ (1.Univ. of Tsukuba, 2.Kanazawa Univ., 3.RIKEN, 4.QST, 5.Univ of Vienna)

Keywords:Anthropogenic radionuclides, Neptunium isotopes, Spike, Seawater

It is estimated that about 2000 kg of ²³⁷Np, one of the most important nuclides in high-level radioactive waste, has already been released into the surface environment due to human nuclear activities. Since Np is mobile in the environment, it is essential to understand its concentration and distribution in order to understand its behavior and to facilitate its use as a tracer in the water cycle. However, no comprehensive studies have been carried out, especially in aqueous environments, because it is necessary to handle large volume of samples during complicated chemical treatments, and there are no appropriate isotope spikes in mass spectrometry. We have attempted, with the aim of establishing a simpler Np determination method for relatively large volume environmental water samples, to produce ^236gNp as an isotope-spike for ²³⁷Np measurements and to construct a new pretreatment method for large volume environmental water samples.