Behavior and distribution of 239+240Pu and 241Am in the east coast of Peninsular Malaysia marine environment

Simultaneous Determination of Transuranium Radionuclides for Nuclear Forensics by Compact Accelerator Mass Spectrometry

Accelerator mass spectrometry (AMS) is one of the most sensitive techniques used to measure the long-lived actinides. This is particularly of interest for determination of ultra-trace transuranium nuclides and their isotopic fingerprints for nuclear forensics. In this work, a new method was developed for simultaneous determination of transuranium nuclides (Np, Pu, Am, and Cm isotopes) by using 300 kV AMS after a sequential chemical separation of each group of actinides. ²⁴²Pu and ²⁴³Am were utilized as tracers for Np/Pu and Am/Cm yield monitoring. The results show that the chemical behaviors of Np and Pu on the TK200 column and those of Am and Cm on the DGA column were very consistent in 8-9 mol/L of HNO₃ and 0.015-0.03 mol/L of NaNO₂ media during the radiochemical separation. The AMS detection efficiencies for transuranium nuclides were also evaluated. The detection limits for all radionuclides are below femtogram level and even in attogram level for Pu and Cm isotopes. The established method has been successfully applied to accurately measure various transuranium nuclides in a single actinide radionuclide solution, demonstrating its feasibility for nuclear forensic investigation.

Determination of 241Am in Environmental Samples: A Review

The determination of 241Am in the environment is of importance in monitoring its release and assessing its environmental impact and radiological risk. This paper aims to give an overview about the recent developments and the state-of-art analytical methods for 241Am determination in environmental samples. Thorough discussions are given in this paper covering a wide range of aspects, including sample pre-treatment and pre-concentration methods, chemical separation techniques, source preparation, radiometric and mass spectrometric measurement techniques, speciation analyses, and tracer applications. The paper focuses on some hyphenated separation methods based on different chromatographic resins, which have been developed to achieve high analytical efficiency and sample throughput for the determination of 241Am. The performances of different radiometric and mass spectrometric measurement techniques for 241Am are evaluated and compared. Tracer applications of 241Am in the environment, including speciation analyses of 241Am, and applications in nuclear forensics are also discussed.

237Np and 241Am as Fingerprints in the Major River Basins of Southern China and North South China Sea: A Land-Sea Perspective

During the global nuclear weapon tests, large amounts of radioactive elements are released into the environment. Long-period actinide elements such as Np, Pu, and Am exhibit different behaviors in various environments, and their isotope characteristic fingerprints are of great significance for studying the distribution, migration, and prediction of radioactive pollutants. To investigate the distribution of ²⁴¹Am and ²³⁷Np in southern China, activities of ²⁴¹Am (0.008 ± 0.012-0.932 ± 0.066 Bq/kg) and ²³⁷Np (0.037 ± 0.003-1.458 ± 0.063 mBq/kg), ²³⁷Np/²³⁹Pu atom ratios (0.055 ± 0.003-0.864 ± 0.054), and ²⁴¹Am/^239+240Pu activity ratios (0.033 ± 0.075-15.870 ± 0.477) in 95 surface sediment samples collected from the northern South China Sea and major river basins were analyzed for the first time. Due to the different scavenging mechanisms of Am and Pu, ²⁴¹Am is preferentially concentrated by sinking the particulate, while plutonium is scavenged in the coastal area, resulting in a higher ²⁴¹Am/^239+240Pu activity ratio in estuary and coastal areas. The distribution of ²³⁷Np shows obvious spatial inhomogeneity as the high migration rate. The relevant fingerprint characteristic has changed greatly and needs to be updated urgently. As a result of the convergence of land and sea, ²⁴¹Am, ^239,240Pu, and ²³⁷Np are dominated by terrestrial sediments and deposited in the coastal area of southern China, which should be paid more attention to. This work can establish China's current neptunium radioactivity database, and the difference in Np, Pu, and Am scavenging processes may be a powerful tool for evaluating the impact of the Pearl River Estuary salt tide.

Uranium and plutonium in anoxic marine sediments of the Santiago River mouth (Eastern Pacific, Mexico)

The uranium (U) and plutonium (Pu) content with depth in a sediment core collected in the continental shelf off the mouth of the Santiago River in the Mexican Pacific was studied to evaluate the contamination effects of the effluent of the Santiago-Lerma River as it moves into the sea. The large mass of terrestrial detritus delivered by the river influences the physicochemical and geochemical processes in the seafloor. Abnormal concentrations of U and Pu in sediments were examined as indicative of the effects of anoxic conditions. One of the indicators of pollution of seawater is the bacterial activity of the shallow seabed layer; and among the prevailing bacteria, the magnetotactic ones induce the formation of euhedral and framboidal shapes (pyrite). These pyrite entities are by-products of anoxic environments loaded with decomposing detrital material and are very abundant in the surface layers of the sediment core analyzed. The pyrite formation is the result of a biochemical reaction between iron and organic sulphur reduced by bacteria, and the pyrite entities precipitate to the seafloor. In the same upper zone of the profile, ²³⁸U is readily immobilized, while ²³⁴U is oxidized and dissolved in seawater by the effect of hot atom chemistry. This may cause the activity ratio (AR) ²³⁴U/²³⁸U disequilibrium (near 0.41). Furthermore, in the shallow layer of the sediment core, an abnormally high concentration of ^239+240Pu was detected. In this upper layer, the activity concentrations found were 3.19 Bq kg^-1 for ²³⁸U, 1.32 kg^-1 for ²³⁴U and 2.78 Bq kg^-1 for ^239+240Pu. In the lower fractions of the sediment core, normal values of AR ²³⁴U/²³⁸U (≈1) were found, with traces of ^239+240Pu.