Spectrophotometric and calorimetric studies of Np(V)complexation with sulfate at 10-70A degrees c
One of the approaches to safe management of highlevel nuclear wastes (HLW)calls for the disposal of HLW in geological repositories. Though the engineered barrier systems are expected to last a very long time after the repository is closed, they may gradually deteriorate and eventually lose integrity. consequently, water could contact the waste, dissolve it, and carry radionuclides out of the repository. Under the chemical environment in the vicinity of the waste form, 237Np(V) is one of the most soluble radionuclides and is most likely to be carried away from the repository. Because of its long half-life and high mobility, it is projected that, in the proposed Yucca Mountain Repository, the fractional dose attributed to 237Np will increase to 67% of the total dose in 75000 years [1]. As a result, the migration of Np in the postclosure chemical environment of the repository is a great concern to long-term repository performance. Because the temperature of the HLW repository could remain significantly higher than the ambient even thousands of years after the closure of the repository, predictions of the chemical behavior of Np in the repository can not be made without reliable thermodynamic data concerning the interactions of Np with the ligands that exist in the groundwater of the repository (e.g., OH–, F–, SO42– , PO43– and CO32) at elevated temperatures. Unfortunately, thermodynamic data on actinide complexation at elevated temperatures are scarce and highly scattered [2]. Lack of reliable geochemical thermodynamic data could lead to conservative decisions that have too big safety margins and raise the cost of the project. To help with the performance assessment of the HLW repository and fill the gap in thermodynamic data on actinide complexation at elevated temperatures, we have studied the complexation of actinides (Th, U, Np and Pu) with selected organic and inorganic ligands at elevated temperatures. This paper summarizes the results of the complexation of Np(V) with sulfate at 10–70°C.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 953791
- Report Number(s):
- PNNL-SA-65646; DF0961000; TRN: US1001353
- Journal Information:
- Journal of Thermal Analysis and Calorimetry, 95(2):409-413, Vol. 95, Issue 2; ISSN 1388-6150
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ACTINIDES
HIGH-LEVEL RADIOACTIVE WASTES
MONITORED RETRIEVABLE STORAGE
NEPTUNIUM
NEPTUNIUM COMPLEXES
NEPTUNIUM 237
PLUTONIUM
RADIOACTIVE MATERIALS
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTES
RADIONUCLIDE MIGRATION
SAFETY MARGINS
SULFATES
TEMPERATURE DEPENDENCE
THORIUM
URANIUM
WASTE FORMS
YUCCA MOUNTAIN