First study of 237Np in Chinese soils: Source, distribution and mobility in comparison with plutonium isotopes

Determination and Assessment of Transuranic Isotopes (Pu, Np, Am) Activities and Isotopes Ratios in Antarctic Marine Sediments

“…Therefore, we believe that the main source of radionuclides in Antarctic Ocean sediments is still global fallout caused by long-distance water and atmospheric transport. Studies 6,23 have shown that the current 237 Np/ 239 Pu atom ratio has been significantly reduced compared with the reference value of the preceding century. Neptunium is generally considered to be a highly soluble and fluid pentavalent state (NpO 2+ ) in well-oxygenated seawater.…”

“…1−4 Due to the long life, α or β emission ( 237 Np, T 1/2 = 2.14 × 10 6 years, α emitter; 239 Pu, T 1/2 = 2.41 × 10 4 years, α; 240 Pu, T 1/2 = 2.14 × 10 6 years, α; 241 Pu, T 1/2 = 14.4 years, β; 241 Am, T 1/2 = 433 years, α) and easy enrichment in organs of these transuranic radionuclides, 5 transuranic nuclides have been listed as the most radiotoxic "Group 1" radionuclides by IAEA and have drawn great environmental concern. 6 Transuranic isotopes are also verified as ideal tracers to study the environmental processes since 1945. 7 For instance, as most 239 Pu and 240 Pu are produced through sequential neutron activation reactions of uranium, 240 Pu/ 239 Pu atom ratio is variable for reprocessing plants, reactor accidents, and weapon fallout, making it an effective indicator to identify different Pu sources.…”

“…Research on the 237 Np/ 239 Pu atom ratio shows that the current ratio has changed significantly from the reference value of the same source in the preceding century in various environments. 6,23 Now it is difficult to directly trace the source of Np in a certain area through this ratio. Therefore, it is particularly important to investigate the environmental background value and update the reference ratio in a relatively single area of radioactive pollution sources.…”

“…Neptunium (Np), plutonium (Pu), and americium (Am) are three kinds of anthropogenic radioactive transuranium deriving from nuclear weapons testing (NWT) from 1945 CE to the 1980s in addition to accidental release and nuclear wastes. − Due to the long life, α or β emission ( 237 Np, T 1/2 = 2.14 × 10 6 years, α emitter; 239 Pu, T 1/2 = 2.41 × 10 4 years, α; 240 Pu, T 1/2 = 2.14 × 10 6 years, α; 241 Pu, T 1/2 = 14.4 years, β; 241 Am, T 1/2 = 433 years, α) and easy enrichment in organs of these transuranic radionuclides, transuranic nuclides have been listed as the most radiotoxic “Group 1” radionuclides by IAEA and have drawn great environmental concern . Transuranic isotopes are also verified as ideal tracers to study the environmental processes since 1945 .…”

“…A large number of studies − have shown that the distribution of 241 Am/ 239+240 Pu activity ratio in seawater and marine sediments is significantly different, and the different sorting of Am and Pu by sinking particles and in situ decay of parent 241 Pu makes more 241 Am enriched in marine surface sediments. Research on the 237 Np/ 239 Pu atom ratio shows that the current ratio has changed significantly from the reference value of the same source in the preceding century in various environments. , Now it is difficult to directly trace the source of Np in a certain area through this ratio. Therefore, it is particularly important to investigate the environmental background value and update the reference ratio in a relatively single area of radioactive pollution sources.…”