CN105761770B - It is a kind of to use azanol acetic acid to be stripped the plutonium purification cycle technique of reagent - Google Patents

Abstract

The invention belongs to nuclear fuel to post-process field.To solve the problems such as existing Purex flow plutonium purification cycle plutonium enriched level using salt-free go back original reagent is relatively low, security is poor, azanol acetic acid is used to be stripped the plutonium purification cycle technique of reagent the invention provides a kind of.The technique includes：2BX azanol acetic acid concentration is 0.5 0.8mol/L, and 2BF plutonium nitrate concentration is 8 15g/L；2BS concentration of nitric acid is 0 0.5mol/L；Cycles of concentration is 36 times；Series >=9 grade are stripped, mend 35 grades of series of extraction.The plutonium purification cycle technique of the present invention can realize that stripping process plutonium concentrates more than 5 times, and the plutonium concentration of gained plutonium product liquid reaches as high as 70g/L, achieves higher plutonium yield and good uranium removal effect；Operation stability is good in process condition range；With preferable economy.

Description

A recycling process for purifying plutonium using hydroxylamine acetic acid as stripping reagent

technical field

The invention belongs to the field of nuclear fuel reprocessing, and particularly relates to a plutonium purification cycle process using hydroxylamine acetic acid as a stripping reagent.

Background technique

The Purex process is currently the main process used in reprocessing plants, which includes a co-decontamination cycle, a uranium purification cycle and a plutonium purification cycle. Among them, the purpose of the plutonium purification cycle is to purify and concentrate the crude plutonium product obtained from the co-decontamination cycle through extraction and stripping processes, and finally obtain qualified plutonium products, see Figure 1.

In order to ensure the plutonium yield of the entire reprocessing process, it is generally required that the plutonium yield of the plutonium purification cycle must reach 99.9%. Since the plutonium purification cycle has the characteristics of high concentration of plutonium in the organic phase (above 10g/L), in the process of stripping and enriching plutonium, with the increase of the stripping concentration ratio, the difficulty of achieving a yield of 99.9% is a geometric progression. Increase, forming a difficult point in the plutonium purification cycle process.

In the plutonium purification cycle, the use of salt-free reducing reagents can reduce the volume of radioactive waste in the reprocessing process, simplify the Purex process technology, and improve the economic benefits of reprocessing. Therefore, the research and development of salt-free reducing reagents is one of the main research contents of the Purex process . At present, there are two main groups of salt-free reducing reagents commonly used in plutonium purification cycles, namely: 1. hydroxylamine-hydrazine system, and 2. dimethylhydroxylamine-hydrazine system.

Hydroxylamine (NH ₂ OH) has a strong reducing property, so it has received extensive attention in the research of salt-free reducing reagents. Barney studied the reaction of hydroxylamine reducing Pu(IV) in _HNO3 solution. It can be seen from the reaction rate equation that the reaction is greatly affected by acidity. As the acidity increases, the reaction speed slows down significantly. The reduction effect of Pu(IV) is better under high temperature conditions. The main advantage of hydroxylamine as a reducing agent is that it can be completely decomposed into relatively safe gases such as nitrogen and nitrous oxide, but the rate of reduction of Pu(IV) by hydroxylamine is relatively slow, and it takes a long time to complete the reaction. At the same time, using hydroxylamine-hydrazine as the plutonium reduction and stripping reagent to achieve a plutonium yield of 99.9% is generally 2BF:2BX:2BS=2:1:0.3, with 12 stages of stripping and 2 stages of supplementary extraction. The maximum extraction and enrichment factor cannot exceed 2.3, and the number of re-extraction stages cannot exceed 3, otherwise the plutonium yield cannot reach 99.9%, resulting in a low enrichment level of plutonium and a low concentration of 2BP plutonium.

As for dimethylhydroxylamine, Koltunov et al. studied the reduction behavior of N,N-dimethylhydroxylamine to Pu(IV) and Np(VI), and the results showed that it can quickly reduce Pu(IV) to Pu(III ). The advanced two-cycle flow + process developed by Zhang Xianye of China Institute of Atomic Energy based on the salt-free reducing reagent N,N-dimethylhydroxylamine-monomethylhydrazine has completed the thermal test of the key process section, and its advantage is that it can obtain comparative Higher stripping ratio of hydroxylamine-hydrazine system. However, dimethylhydroxylamine and monomethylhydrazine are not very stable and less safe; at the same time, the reaction product after the reaction will polymerize in the plutonium nitrate solution, so it is very dangerous. Using dimethylhydroxylamine and monomethylhydrazine as plutonium reduction and stripping reagents, the general process conditions to achieve a plutonium yield of 99.9% are 2BF:2BX:2BS=3.5:1:0.3, 10-stage stripping, 3-stage supplementary extraction, Among them, the maximum concentration ratio of stripping cannot exceed 4.0, and the number of re-extraction stages cannot exceed 3 stages, otherwise the yield of plutonium cannot reach 99.9%.

Contents of the invention

In order to solve the problems of low plutonium concentration level and poor security in the existing Purex process plutonium purification cycle using salt-free reducing reagents, taking into account the plutonium concentration effect and process safety, the present invention provides a method using hydroxylamine acetic acid as a stripping reagent plutonium purification cycle process. The process includes:

(1) The concentration of araminoacetic acid in 2BX is 0.5-0.8mol/L, and the concentration of nitric acid is 0.3-0.7mol/L;

(2) The concentration of plutonium nitrate in 2BF is 8-15g/L;

(3) The nitric acid concentration of 2BS is 0-0.5mol/L;

(4) The concentration ratio is 3-6 times;

(5) The number of back-extraction series is ≥9, and the number of re-extraction series is 3-5.

The hydroxylamine acetic acid concentration of the 2BX is preferably 0.7 mol/L.

The concentration factor is preferably 5 times.

This process uses hydroxylamine acetic acid as a salt-free reducing agent to realize the purification and concentration of plutonium products. The key point of this process is the selection of process conditions. Since there are many process parameters involved, and the selection direction of relevant process conditions is not given in the existing literature, in this case, considering the high radioactivity and High toxicity, so the plutonium purification cycle process of the present invention overcomes a lot of difficulties in the selection of process conditions, and finally determines the suitable range of process conditions.

The plutonium purification circulation process of the present invention can realize the plutonium concentration of more than 5 times in the stripping process, and the plutonium concentration of the obtained plutonium product liquid can reach up to 70g/L, and a relatively high plutonium yield and good uranium removal effect are achieved; the range of process conditions The internal operation stability is good; there is no need to add supporting reducing agent at the same time during the stripping process, which reduces the use of reagents, improves economic efficiency, and has no impact on the subsequent plutonium precipitation process.

Description of drawings

Fig. 1 Schematic diagram of plutonium purification cycle process in Purex process.

detailed description

The embodiments of the present invention will be further described below in conjunction with examples.

Example 1

Applying the plutonium purification cycle process of the present invention to the purification and concentration of plutonium products in the Purex process, the following process conditions are adopted:

(1) The concentration of araminoacetic acid in 2BX is 0.6 mol/L, and the concentration of nitric acid is 0.6 mol/L;

(2) The concentration of plutonium nitrate in 2BF is 12g/L;

(3) The nitric acid concentration of 2BS is 0.3mol/L;

(4) The concentration factor is 5.5 times;

(5) There are 12 stages of back-extraction and 4 stages of re-extraction.

The plutonium concentration of the obtained plutonium product liquid is 71.4g/L, the residual plutonium concentration in the organic phase is about 0.4mg/L, and the plutonium yield is greater than 99.99%.

Example 2

Applying the plutonium purification cycle process of the present invention to the purification and concentration of plutonium products in the Purex process, the following process conditions are adopted:

(1) The concentration of araminoacetic acid in 2BX is 0.8mol/L, and the concentration of nitric acid is 0.4mol/L;

(2) The concentration of plutonium nitrate in 2BF is 9g/L;

(3) The concentration of nitric acid in 2BS is 0.1mol/L;

(4) The concentration factor is 6 times;

(5) There are 10 stages of back extraction and 5 stages of re-extraction.

The plutonium concentration of the obtained plutonium product liquid is 60.8g/L, the residual plutonium concentration in the organic phase is about 0.3mg/L, and the plutonium yield is greater than 99.99%.

Claims (3)

1. a kind of plutonium purification circulation process that adopts azaminoacetic acid as stripping reagent, it is characterized in that this process comprises: (1) The concentration of araminoacetic acid in 2BX is 0.5-0.8mol/L, and the concentration of nitric acid is 0.3-0.7mol/L; (2) The concentration of plutonium nitrate in 2BF is 8-15g/L; (3) The nitric acid concentration of 2BS is 0-0.5mol/L; (4) The concentration ratio is 3-6 times; (5) The number of back-extraction series is ≥9, and the number of re-extraction series is 3-5. 2. The plutonium purification cycle process using hydroxylamine acetic acid as stripping reagent as claimed in claim 1, characterized in that: the concentration of hydroxylamine acetic acid in the 2BX is 0.7mol/L. 3. The plutonium purification cycle process using hydroxylamine acetic acid as stripping reagent as claimed in claim 1, characterized in that: the concentration ratio is 5 times.