Evaluation of Value for Hydrogen Release from High-level Liquid Waste,(II). Influence of Solution Depth on Hydrogen Release from Non-stirred Nitric Acid Solution.

The proper management of spent fuel arising from nuclear power production is a key issue for the sustainable development of nuclear energy. While conventional reprocessing process, PUREX process, was successful to recover uranium and plutonium, in recent years some countries have turned to focus on advanced reprocessing process, which features of partitioning of minor actinides (MA) and long-lived fission products(LLFP). Most advanced reprocessing processes under development involve new extractants and additional extraction cycles. In China, TRPO extraction process has been developed to partition MA/LLFP from high-level liquid waste(HLLW) since early 1980’s. In parallel to R&D work on separation technologies, studies on concentration & denitration process have been evolved to prepare feed solutions to suit qualifications of extraction. Industrially, concentration & denitration is the internationally recognized standard to treat HLLW released from PUREX before vitrification. It enables to minimize the volume of interim storage, to restrain the corrosion of storage tank, to recover nitric acid in HLLW and to reduce the required evaporation duty of the vitrification process. Generally, the constitution of concentrated HLLW has little impact on the following vitrification process. But when concentration & denitration acts as pretreatment process of partitioning, the composition of actinides, fission products, and nitric acid in concentrated HLLW solution plays significant role in extraction process. A series of technical issues relevant to the connection between concentration ﹠denitration and extractions should be solved. This paper describes current status of concentration & denitration technology utilized in industry and under reprocessing plants. The specific separation requirements in advanced reprocessing process and challenges to apply concentration & denitration process are addressed. Besides, concentration & denitration process was tested in laboratory to adjust feed solutions for TRPO and Cyanex301 partitioning. Results demonstrate its promising prospect in advanced reprocessing process.

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Single-cycle separation of americium (III) from simulated high-level liquid waste using tetra-bis(2-ethylhexyl)diglycolamide and bis(2-ethylhexyl)phosphoric acid solution

Journal of Environmental Chemical Engineering ◽

10.1016/j.jece.2013.06.023 ◽

2013 ◽

Vol 1 (3) ◽

pp. 559-565 ◽

Cited By ~ 14

Author(s):

P.K. Nayak ◽

R. Kumaresan ◽

K.A. Venkatesan ◽

S. Rajeswari ◽

G.G.S. Subramanian ◽

...

Keyword(s):

Phosphoric Acid ◽

Acid Solution ◽

Liquid Waste ◽

Phosphoric Acid Solution ◽

High Level Liquid Waste ◽

Single Cycle ◽

High Level

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Effect of pKa on the extraction behavior of Am(III) in organo phosphorus acid and diglycolamide solvent system

Radiochimica Acta ◽

10.1515/ract-2017-2769 ◽

2018 ◽

Vol 106 (2) ◽

pp. 107-118 ◽

Cited By ~ 7

Author(s):

K. Rama Swami ◽

R. Kumaresan ◽

P. K. Nayak ◽

K. A. Venkatesan ◽

M. P. Antony

Keyword(s):

Nitric Acid ◽

Metal Ions ◽

Phosphinic Acid ◽

Liquid Waste ◽

High Level Liquid Waste ◽

Single Cycle ◽

Cyanex 272 ◽

Extraction Behavior ◽

Trivalent Actinides ◽

High Level

AbstractA combination of neutral and acidic extractant has been proposed for the single-cycle separation of trivalent actinides from high-level liquid waste (HLLW). The nature of acidic extractant in the combined solvent formulation plays a profound role in deciding the extraction and stripping of trivalent actinides. Therefore, the extraction behavior of Am(III) in a solution of tetra-bis(2-ethylhexyl)-diglycolamide (TEHDGA) and acidic extractant (HA) was studied from nitric acid medium. The acidic extractants chosen were bis(2-ethylhexyl)phosphoric acid (HDEHP), bis(2-ethylhexyl)phosphonic acid (PC88A) and bis(2,4,4-trimethylpentyl)phosphinic acid (CYANEX-272) whose pKavalues were 3.24, 4.51 and 6.37, respectively. The distribution ratio of Am(III) was measured as a function of various parameters such as concentration of nitric acid, TEHDGA, HA etc. The data were compared with those obtained in individual solvent systems namely 0.1 M TEHDGA/n-DD and HA/n-DD. Slope analysis of the extraction data indicated the synergic participation of both TEHDGA and HDEHP in the extraction of Am(III) at all acidities. However, antagonistic effect was observed at lower acidity when TEHDGA was mixed to PC88A or CYANEX-272 present inn-DD. Accordingly, a suitable mechanism has been proposed for the extraction of Am(III) at all acidities using these combined solvent formulation. Studies with fast reactor simulated high level liquid waste indicated that extraction of Am(III) was accompanied by co-extraction of lanthanides and unwanted metal ions such as Zr(IV), Mo(VI), Y(III) and Pd(II). However, addition of trans-1,2-diaminocyclohexane-N,N,N,N′-tetraaceticacid (CyDTA) reduced the extraction of unwanted metal ions. Batch extraction and stripping studies indicated the possibility of using 0.1 M TEHDGA+0.25 M HDEHP inn-dodecane for the single cycle separation of Am(III) from FR-SHLLW.

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