Electrochemical decontamination method for zirconium alloy waste cladding

A zirconium alloy and electrochemical technology, which is applied in the field of electrochemical decontamination of zirconium alloy waste cladding, can solve the problems of not meeting the standard of commercial decontamination, large amount of waste liquid, and low decontamination coefficient

Active Publication Date: 2020-09-01
LANZHOU UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The Savannah River National Laboratory in the United States used less than 1M hydrofluoric acid to treat high-level radioactive waste cladding materials. The study found that when the etching depth reached 180 μm, the radiation dose was close to the background value. Although the research achieved a certain purpose, it was still The standard for commercial decontamination is not met. The main reason is that the decontamination coefficient is low. About 1 liter of hydrofluoric acid is required for 0.5 grams of pollutants. The cost of decontamination is high and the amount of waste liquid is large.

Method used

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  • Electrochemical decontamination method for zirconium alloy waste cladding
  • Electrochemical decontamination method for zirconium alloy waste cladding
  • Electrochemical decontamination method for zirconium alloy waste cladding

Examples

Experimental program
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Effect test

Embodiment 1

[0042] (1) Preparation of electrolyte: prepare electrolyte with pure water, hydrofluoric acid, sodium fluoride and nitric acid, the molar concentration of hydrofluoric acid in the electrolyte is 0.1mol / L, and the molar concentration of sodium fluoride is 0.1mol / L , the molar concentration of nitric acid is 0.0001mol / L, and the pH value of the electrolyte is 2.0;

[0043] (2) Calcination treatment simulates the zirconium-4 alloy oxide layer similar to the waste cladding:

[0044] Wash the cut zirconium-4 alloy material with washing powder to remove oil stains, then place it in an ultrasonic cleaner for 10 to 20 minutes, repeat two to three times, until there is basically no black residue in the residual liquid after cleaning, and then place it in an oven Drying in medium temperature; place the dried zirconium-4 alloy material in a muffle furnace, and calcine it at 550°C for 1 hour to form an oxide layer similar to the surface of the waste cladding, and clean it with the same me...

Embodiment 2

[0056] The process of electrochemical decontamination of zirconium alloy waste cladding is the same as (1) to (3) in Example 1, and the difference from Example 1 is that the applied voltage is set to 5.0V, 5.5V, 6.5V, 7.0V, 7.5V, 8.0V, the electrochemical etching rate of zirconium alloy waste cladding is shown in Table 1. It can be seen from Table 1 that the etching rate reaches 20 μm / h when the applied voltage is 8 V. Since the high-level radioactive materials in the waste cladding are mainly concentrated near the surface layer of 100 μm, in the nitric acid-hydrofluoric acid-sodium fluoride electrolyte system, the potential 8V (relative to saturated calomel electrode) electrolysis for 5 hours can basically meet the actual electrochemical decontamination needs; in addition, it can also be seen from Table 1 that the etching rate can be controlled by controlling the etching potential.

Embodiment 3

[0062] The process of electrochemical decontamination of zirconium alloy waste cladding is the same as (1)~(3) in embodiment 1, and the difference from embodiment 1 is that the fluorine in the nitric acid-hydrofluoric acid-sodium fluoride electrolyte system is The molar concentration of NaCl was changed to 0.1mmol / L and 10mmol / L.

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Abstract

The invention provides an electrochemical decontamination method for zirconium alloy waste cladding, and relates to the technical field of zirconium alloy waste cladding decontamination. The electrochemical decontamination method for the zirconium alloy waste cladding comprises the following steps that the zirconium alloy waste cladding is connected with copper, the end of the zirconium alloy waste cladding is completely immersed into an electrolyte, and a three-electrode system is adopted to electrolyze the zirconium alloy waste cladding, wherein the three-electrode system takes the zirconiumalloy waste cladding as a working electrode, takes a platinum electrode as an auxiliary electrode, and takes a saturated calomel electrode as a reference electrode, the electrolyte is a mixed solution of hydrofluoric acid, nitric acid and sodium fluoride, and the applied voltage is 5-12V. According to the electrochemical decontamination method for the zirconium alloy waste cladding, the electrochemical decontamination method is adopted to etch an oxide layer in the zirconium alloy waste cladding, the adopted HNO3-HF-NaF electrolyte system has the characteristics of being high in stability, high in electrolysis efficiency and controllable in etching speed, the oxide layer in the surface of the zirconium alloy waste cladding can be removed only by applying the three-electrode system and applying a very small voltage, and the electrochemical decontamination method is simple and convenient in operation, economical, environment-friendly, high in safety and suitable for large-scale industrial production.

Description

technical field [0001] The invention relates to the technical field of decontamination of zirconium alloy waste cladding, in particular to an electrochemical decontamination method for zirconium alloy waste cladding. Background technique [0002] Zirconium-4 alloys are widely used in the protective layer of nuclear reactors. After decommissioning of nuclear power plants or nuclear reactors, a large number of high-level radioactive waste claddings are left. The waste claddings contain a large number of useful nuclides, such as uranium, plutonium, cesium and other high value-added nuclear materials. white. [0003] Commonly used waste cladding treatment methods include wet storage and dry storage. Wet storage is to store waste cladding in desalinated water, and use the natural decay of radionuclides in the waste cladding to convert high-level waste cladding into For low-radiation materials, wet storage takes a long time, and is prone to overheating, hydrogen leakage, and oxyg...

Claims

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Application Information

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IPC IPC(8): C25F1/08G21C3/16
CPCC25F1/08G21C3/16Y02E30/30
Inventor杜永令常彦龙时雪钊
OwnerLANZHOU UNIVERSITY