Effect of Traditional Uranium Hydrometallurgical Process on Distribution Pattern of Rare Earth Element and Its Application in Nuclear Forensics

Abstract

Uranium ore is the main raw material in the front end of the nuclear fuel cycle in the production of yellowcake. The distribution pattern of rare earth element (REE) has regional characteristics, and it is generally believed that grinding process will not change this feature, so the fingerprint information of REE pattern has been applied in the nuclear verification traceability of yellowcake. In uranium hydrometallurgical plant, uranium ore not only needs to go through grinding, but also needs to go through complex processes such as leaching, extraction, reverse extraction and precipitation to get yellowcake products. In this process, the change of distribution pattern of REE remains to be studied. Therefore, from the perspective of production process, the applicability of the distribution pattern of REE in nuclear forensics traceability was studied. By tracking the production process from uranium ore to sodium diuranate in the conventional uranium hydrometallurgical plant in China, the samples of uranium ore, clarified leach solution, raffinate and sodium diuranate were pre-treated (acid dissolution methods) under the experimental conditions of low procedure background (less than 0.512 ng/mL) and low detection limit (less than 0.007 5 ng/mL). After the REE was separated by TRU resin, the content was accurately determined by inductively coupled plasma mass spectrometry (ICP-MS) and the distribution patterns of REE were drawn. The results show that after the separation of the four samples and removal of a large amount of uranium matrix, the contents of REE measured by ICP-MS are more accurate. The above four samples are enriched in light REE on the whole, with obvious Eu deficit, and the distribution pattern of REE generally presents a right-sloping deep valley. These indicate that uranium materials which have undergone traditional uranium hydrometallurgy process will retain the REE characteristics of uranium ore in general, and the distribution pattern of REE is helpful to identify the origin and history of uranium materials. In view of the obvious enrichment of Er in sodium diuranate sample, it is possible to further explore how the different chemical precipitations of leach ore cause the REE fractionation, so as to better explain how the production process and chemical history of the product affect the REE characteristics of yellowcake, which is also the basis for the use of REE in nuclear forensics traceability.

Keywords

• distribution pattern of ree
• nuclear forensics
• uranium hydrometallurgical process
• inductively coupled plasma mass spectrometry