CN112924518A - Method for analyzing neptunium content in neptunium dioxide sample - Google Patents
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Abstract
A method for analyzing the neptunium content in a neptunium dioxide sample adopts high silver oxide as an oxidant and combines a controlled potential coulometry method to determine the neptunium content. The valence state of the neptunium in the neptunium dioxide sample is quickly adjusted to be hexavalent, so that the phenomenon that the oxidation and reduction current is too large when cerium (IV) is used for adjusting the valence state of the neptunium in the coulometry determination is avoided, and the alarm of an instrument stops working; the mode of adding sulfamic acid is adopted to destroy and add excessive high silver oxide, so that the excessive high silver oxide is prevented from being removed in a glove box by adopting a heating mode, and the operation is safe and the time is saved. The coulometric analysis method for the neptunium content established by the standard has accurate analysis result and wide application range, and can directly complete the analysis and determination of the neptunium content by adopting the control potential titration. The device is simple and convenient to operate, reduces errors of manual operation under the condition of ensuring radiation protection, and is high in accuracy of analysis results, good in analysis precision, low in consumption of analysis materials and low in experiment cost.
Description
Technical Field
The invention relates to the field of analysis of neptunium content, in particular to a method for analyzing the neptunium content in a neptunium dioxide sample.
Background
The neptunium content in the neptunium dioxide sample is an important index for judging whether the neptunium sample is qualified or not, and is an analysis item which needs to be detected; the method can accurately, timely and stably analyze whether the neptunium content in the neptunium dioxide sample is normal for the operation of the reaction process flow and judge whether the process parameters such as the calcination temperature and the like meet the requirements, thereby playing a crucial role. Therefore, the establishment of an analysis method for precisely determining the neptunium content in the neptunium dioxide sample has extremely important significance.
The stewart and the like measure the contents of neptunium in various valence states by a potential-controlled coulometry method, and the method has the defects that the oxidation on a platinum counter electrode is slow, the absolute error of the measurement is large, and the measurement process is complicated; the method for determining 1-3 mg of neptunium by a galvanostatic method such as Behcet al needs to titrate by ferric sulfate (III), but the preparation steps of a ferric sulfate (III) standard solution are complex; the neptunium is measured by the research of the Chinese atomic energy science institute and the Lanzhou nuclear fuel plant respectively by adopting a constant-current coulometry method and a potentiometric titration method, the neptunium content is 2mg, and the precision is poor.
The standard adopts high-silver oxide as an oxidant and combines a control potential coulometry method to determine the neptunium content. The valence state of the neptunium in the neptunium dioxide sample is quickly adjusted to be hexavalent, so that the phenomenon that the oxidation and reduction current is too large when cerium (IV) is used for adjusting the valence state of the neptunium in the coulometry determination is avoided, and the alarm of an instrument stops working; the mode of adding sulfamic acid is adopted to destroy and add excessive high silver oxide, so that the excessive high silver oxide is prevented from being removed in a glove box by adopting a heating mode, and the operation is safe and the time is saved. The coulometric analysis method for the neptunium content established by the standard has accurate analysis result and wide application range, and can directly complete the analysis and determination of the neptunium content by adopting the control potential titration. The device is simple and convenient to operate, reduces errors of manual operation under the condition of ensuring radiation protection, and is high in accuracy of analysis results, good in analysis precision, low in consumption of analysis materials and low in experiment cost.
Disclosure of Invention
The invention aims to: provides an analysis method for the neptunium content in a neptunium dioxide sample.
The invention has the following remarkable effects: the invention relates to an analysis method for determining the neptunium content in a neptunium dioxide sample in an after-treatment process by using a control potential method. The method precision (RSD) is better than 0.2%, and the relative expansion uncertainty is 1.5 multiplied by 10-3And (K is 2), the method can meet the requirement of post-processing product analysis, and is accurate and reliable.
Detailed Description
Example 1
An analysis method for the neptunium content in a neptunium dioxide sample comprises the following steps:
(1) preparation of sulfuric acid solution
A certain amount of nitric acid is measured, stirred and added into deionized water, cooled and transferred into a 1L volumetric flask, and diluted to the scale with water.
(2) Preparation of sulfamic acid solution
An amount of sulfamic acid solid was weighed into a 100mL beaker and deionized water was added to form a saturated solution.
(3) Preparation of aluminium sulphate solution
A quantity of aluminum sulfate solids was weighed into a 100mL beaker and deionized water was added to form a saturated solution.
(4) Dissolution of the sample
A certain amount of neptunium dioxide sample is weighed and placed in a beaker. Adding analytically pure nitric acid solution and analytically pure HF solution. The beaker was placed on an electric furnace and the sample was completely dissolved at a temperature to concentrate the solution to a volume of about 1 mL. Adding sulfuric acid solution, continuing heating and concentrating until the solution is nearly dry, and transferring the sample solution into a weighed sample dividing bottle by using a dropper.
(5) Sample dispensing
The neptunium solution mass transferred to the sample vial was weighed. And (4) pressing the sample distribution bottle to enable the sample solution to be dripped into the electrolytic cell cup, and weighing the residual solution in the sample distribution bottle. The mass difference is the mass of the solution in the electrolytic cell cup, and the mass of the neptunium in the electrolytic cell cup is calculated according to the concentration of the neptunium solution.
(6) Measurement of blank electric quantity
Preheating by a coulometer, adding a sulfuric acid solution into an electrolytic cell cup, adding high silver oxide, and stirring while adding until excessive high silver oxide is added and the black color is not faded after 10 min. And (4) dropwise adding sulfamic acid solution to completely eliminate excessive high silver oxide. Stirring, adding aluminum sulfate solution, adding sulfuric acid solution to submerge the gold electrode on the sample liquid surface, and introducing argon after installing the electrode. Reducing at a reduction potential, and stopping reduction when the residual current is reduced to below 10 muA; the oxidation is carried out at an oxidation potential and is stopped when the residual current drops below 10 mua.
(7) Determination of samples
In the separated neptunium sample, the blank charge is determined according to step (6).
(8) Determination of chemical correction factor
Accurately dividing 1 mg-2 mg (accurate to 0.01mg) of neptunium standard solution into electrolytic cell cups according to the step (5), and recording the mass m of the neptunium standard solutionn. According to the step (7)Measuring the neptunium standard solution, and recording the oxidation electric quantity Qn of the neptunium standard solution; record the oxidation electric quantity Qs of the sample
(9) The amount of the substance to be measured is calculated from the amount of electricity required for oxidation according to Faraday's law.
Calculating a chemical correction factor Fch according to formula (1):
in the formula:
fch-chemical correction factor in units of moles/coulombs (mol/C);
mn-mass in grams (g) of neptunium standard solution in the cell;
mn-the molar mass of the neptunium standard substance, in grams per mole (g/mol);
the oxidation charge measured for the Qn-Netunium standard in coulombs (C);
QBblank oxidation charge in coulombs (C).
The neptunium content in the neptunium dioxide sample is calculated according to the formula (2):
in the formula:
CNp-neptunium content in the sample in hundred percent (%);
fch-chemical correction factor in units of moles/coulombs (mol/C);
ms — the molar mass of neptunium in the sample solution in grams per mole (g/mol);
qs-measured oxidation charge of the sample in coulombs (C);
QBblank oxidation charge in coulombs (C).
ms-the mass of the neptunium sample in grams (g) in the cell cup;
example 2
A method for analyzing the neptunium content in a neptunium dioxide sample comprises the following specific determination steps:
(1) preparation of sulfuric acid solution
30-35 mL of analytically pure nitric acid is measured by a 50mL measuring cylinder, added into 500-550 mL of secondary water, cooled and transferred into a 1L volumetric flask, the volume is determined by deionized water, and the concentration of the prepared sulfuric acid is 0.5 mol/L.
(2) Preparation of sulfamic acid solution
Weighing 80-100 g (accurate to 1mg) of analytically pure sulfamic acid solid in a 100mL beaker, and adding 70-80 mL of deionized water to prepare a sulfamic acid solution which is a saturated sulfamic acid solution.
(3) Preparation of aluminium sulphate solution
Weighing 80-100 g (accurate to 1mg) of analytically pure aluminum sulfate solid in a 100mL beaker, and adding 70-80 mL of deionized water to prepare a saturated aluminum sulfate solution.
(4) Dissolution of the sample
A sample of neptunium dioxide 0.03g (to the nearest 0.01mg) was accurately weighed out and placed in a 50mL beaker. Adding 4-5 mL of analytically pure nitric acid solution, and adding 2-3 drops of analytically pure HF solution. The beaker is placed on an electric furnace (the temperature is adjusted to be within the range of 0-250 ℃), the sample is completely dissolved at 160-180 ℃, and the volume of the concentrated solution is about 1 mL. Adding 1-2 mL of sulfuric acid solution (1), continuing heating and concentrating until the sample is nearly dry, transferring the sample solution into a weighed sample dividing bottle by using a dropper, and diluting the sample by using the sulfuric acid solution (1) until the neptunium concentration is 1-3 mg/g.
(5) Sample dispensing
The mass of neptunium solution transferred to the sample vial is weighed with a one-hundred-thousandth balance. And (4) pressing the sample distribution bottle to enable the sample solution to be dripped into the electrolytic cell cup, and weighing the residual solution in the sample distribution bottle. The mass difference is the mass of the solution in the electrolytic cell cup, and the mass of the neptunium is 1 mg-2 mg according to the concentration of the neptunium sample solution, namely the mass m of the neptunium in the electrolytic cell cups。
(6) Measurement of blank electric quantity
Preheating for 30min by coulometer, and placing in electrolytic cellThe cup was charged with 10-15 mL of sulfuric acid solution (1) and analytically pure silver oxide was added with stirring until excess silver oxide was added and the black color did not disappear after 10 min. And (3) dropwise adding sulfamic acid solution (2) to completely eliminate excessive black oxidized high silver. Continuously stirring for 3-5 min, adding 0.1mL of aluminum sulfate solution (3), and 15-20 mL of sulfuric acid solution (1) to submerge the gold electrode on the sample liquid surface, and introducing argon (with the purity of 99.99%) for 10-15 min (the argon flow is 10-15 mL/min). Reducing at a reduction potential of 0.665V, and stopping reduction when residual current is reduced to below 10 muA; oxidizing at 1.025V, stopping oxidation when residual current is reduced to below 10 μ A, and recording blank oxidation electric quantity QB。
(7) Determination of samples
To a divided sample of 1mg to 2mg neptunium was added 10mL to 15mL of sulfuric acid solution (1) and analytically pure silver oxide with stirring until excess silver oxide was added and the black color did not disappear after 10min, at which time the solution appeared clear pink. Continuously stirring for 3-5 min, adding 0.1mL of aluminum sulfate solution (3), and 15-20 mL of sulfuric acid solution (1) to submerge the gold electrode on the sample liquid surface, and introducing argon (with the purity of 99.99%) for 10-15 min (the argon flow is 10-15 mL/min). Reducing at a reduction potential of 0.665V, and stopping reduction when residual current is reduced to below 10 muA; the oxidation was carried out at an oxidation potential of 1.025V, and stopped when the residual current dropped below 10. mu.A, and the oxidation charge Qs of the sample was recorded.
(8) Determination of chemical correction factor
Accurately dividing 1 mg-2 mg (accurate to 0.01mg) of neptunium standard solution into electrolytic cell cups according to the step (5), and recording the mass m of the neptunium standard solutionn. Measuring the neptunium standard solution according to the step (7), and recording the oxidation electric quantity Qn of the neptunium standard solution;
(9) the amount of the substance to be measured is calculated from the amount of electricity required for oxidation according to Faraday's law.
Calculating a chemical correction factor Fch according to formula (1):
in the formula:
fch-chemical correction factor in units of moles/coulombs (mol/C);
mn-mass in grams (g) of neptunium standard solution in the cell;
mn-the molar mass of the neptunium standard substance, in grams per mole (g/mol);
the oxidation charge measured for the Qn-Netunium standard in coulombs (C);
QBblank oxidation charge in coulombs (C).
The neptunium content in the neptunium dioxide sample is calculated according to the formula (2):
in the formula:
CNp-neptunium content in the sample in hundred percent (%);
fch-chemical correction factor in units of moles/coulombs (mol/C);
ms — the molar mass of neptunium in the sample solution in grams per mole (g/mol);
qs-measured oxidation charge of the sample in coulombs (C);
QBblank oxidation charge in coulombs (C).
msThe mass of the neptunium sample in the cell cup is given in grams (g).
Claims (6)
1. A method for analyzing the neptunium content in a neptunium dioxide sample is characterized in that: the method comprises the following steps:
step (1) preparation of sulfuric acid solution
Measuring a certain amount of nitric acid, adding into deionized water while stirring, cooling, transferring into a 1L volumetric flask, and diluting with water to a scale;
step (2) preparation of sulfamic acid solution
Weighing a certain amount of sulfamic acid solid in a 100mL beaker, and adding deionized water to form a saturated solution;
step (3) preparation of aluminum sulfate solution
Weighing a certain amount of aluminum sulfate solid in a 100mL beaker, and adding deionized water to form a saturated solution;
step (4) dissolution of the sample
Weighing a certain amount of neptunium dioxide sample, and placing the neptunium dioxide sample in a beaker; adding a nitric acid solution and an HF solution; heating the beaker, completely dissolving the sample at a certain temperature, and concentrating the volume of the solution to about 1 mL; adding a sulfuric acid solution, continuously heating and concentrating until the solution is nearly dry, and transferring the sample solution into a weighed sample separating bottle by using a dropper;
step (5) sample taking
Weighing the mass of the neptunium solution transferred into the sample separating bottle; extruding the sample dividing bottle to enable the sample solution to enter an electrolytic cell cup, and weighing the residual solution in the sample dividing bottle; the mass difference is the mass of the solution in the electrolytic cell cup, and the mass of the neptunium in the electrolytic cell cup is calculated according to the concentration of the neptunium solution;
step (6) measurement of blank electric quantity
Adding a sulfuric acid solution into an electrolytic cell cup, adding high silver oxide, and stirring while adding until excessive high silver oxide is added and the black color is not faded after 10 min; dropwise adding sulfamic acid solution to completely eliminate excessive high silver oxide; continuously stirring, adding an aluminum sulfate solution, adding a sulfuric acid solution to ensure that the gold electrode is just completely submerged on the liquid surface of the sample, and introducing argon after installing the electrode; reducing at a reduction potential, and stopping reduction when the residual current is reduced to below 10 muA; oxidizing at an oxidation potential, and stopping oxidation when the residual current is reduced to below 10 muA; recording the oxidation electric quantity Qs of the sample;
step (7) measurement of sample
Measuring blank electric quantity in the well-divided neptunium sample according to the step (6);
step (8) determination of chemical correction factor
Accurately dividing 1 mg-2 mg of neptunium standard solution into electrolytic cell cups according to the step (5), and recording the mass m of the neptunium standard solutionn(ii) a Measuring the neptunium standard solution according to the step (7), and recording the oxidation electric quantity Qn of the neptunium standard solution;
and (9) calculating the quantity of the measured substance from the electric quantity required for oxidation according to Faraday's law.
Calculating a chemical correction factor Fch according to formula (1):
in the formula:
fch-chemical correction factor in units of mole/coulomb, mol/C;
mn-the mass of neptunium standard solution in gram, g in the electrolytic cell;
the unit of the molar mass of Mn-neptunium standard substance is gram/mole and g/mol;
the oxidation electric quantity measured by Qn-neptunium standard substance is coulomb C;
QB-the oxidation charge of the blank, in coulombs C;
the neptunium content in the neptunium dioxide sample is calculated according to the formula (2):
in the formula:
CNp-the neptunium content in the sample;
fch-chemical correction factor in units of mole/coulomb, mol/C;
ms — the molar mass of neptunium in the sample solution, in grams/mole, g/mol;
qs is the oxidation charge measured for the sample in coulomb C;
QB-the oxidation charge of the blank, in coulombs C;
msthe mass of the neptunium sample in the cell cup is given in grams.
2. The method according to claim 1 for analyzing the neptunium content in a neptunium dioxide sample, characterized in that: in the step (4), analytically pure nitric acid solution and analytically pure HF solution are added.
3. The method according to claim 1 for analyzing the neptunium content in a neptunium dioxide sample, characterized in that: in the step (4), the beaker is placed on an electric furnace for heating.
4. The method according to claim 1 for analyzing the neptunium content in a neptunium dioxide sample, characterized in that: and (5) extruding the sample dividing bottle to enable the sample solution to be dripped into the electrolytic cell cup.
5. The method according to claim 1 for analyzing the neptunium content in a neptunium dioxide sample, characterized in that: in the step (6), coulometer preheating is carried out.
6. The method according to claim 1 for analyzing the neptunium content in a neptunium dioxide sample, characterized in that: in the step (8), 1 mg-2 mg of neptunium standard solution is accurately dispensed into the electrolytic cell cup, and the precision is 0.01 mg.
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