Method for measuring plutonium content of neptunium dioxide sample
Technical Field
The invention relates to the field of determination of plutonium content, in particular to a method for determining the plutonium content of a neptunium dioxide sample.
Background
With the rapid development of the aerospace industry in China, the demand for neptunium is continuously increased, the production of neptunium dioxide products is correspondingly generated, an analysis and detection method of each item in the corresponding neptunium dioxide products must be established, and the plutonium content is one of the items which must be detected. It is therefore necessary to analyze the plutonium content of neptunium dioxide in a timely and accurate manner.
Examples of the analysis method for measuring the plutonium content include coulometry, X-ray analysis, and α -counting. Wherein coulometry and X-ray analysis can determine the plutonium content in the high plutonium content solution. The plutonium content of neptunium dioxide is very small and this type of process cannot be applied.
Since neptunium has similar chemical properties and has alpha radioactivity, 100% of neptunium cannot be completely separated after extraction and separation, and thus, the measurement result by adopting an alpha counting method is high. The energy based on neptunium is 4.8MeV and the energy based on the neptunium is 5.5MeV by adopting an alpha energy spectrum method for measurement, the content of neptunium elements can be measured at the same time, the analysis data is accurate and reliable, and meanwhile, the detection requirement of a process sample can be met.
Disclosure of Invention
The invention aims at: a method for measuring the trace plutonium in a large number of neptunium samples, which is simple in process and convenient to operate, is studied.
The technical scheme of the invention is as follows: an analytical determination method for the plutonium content of a neptunium dioxide sample, comprising the following steps:
preparing a nitric acid hydrofluoric acid mixed acid solution;
measuring a certain volume of analytically pure nitric acid solution, adding the solution into 10-20 mL of water while stirring, adding a certain volume of analytically pure hydrofluoric acid solution, cooling, and transferring into a volumetric flask for constant volume;
step (2) nitric acid solution;
taking a certain volume of analytically pure nitric acid, placing the analytically pure nitric acid in 20-30 mL of deionized water, cooling to room temperature, and then transferring the solution to a volumetric flask for constant volume;
step (3) TOPO-xylene solution;
weighing a certain mass of analytically pure TOPO solid, dissolving the TOPO solid in 10-20 mL of dimethylbenzene, transferring the TOPO solid into a volumetric flask, and fixing the volume by using the dimethylbenzene;
step (4) sodium nitrite solution;
weighing a certain mass of analytically pure sodium nitrite, dissolving in 10-20 mL of deionized water, transferring to a volumetric flask, and fixing the volume by using the deionized water;
step (5) preparation of plutonium standard discs;
transferring 0.1-0.2 mL of plutonium solution with known content into a stainless steel small disc, drying, and measuring and counting on an alpha spectrometer;
dissolving the sample in the step (6);
weighing 10 mg-40 mg neptunium dioxide sample in a 25mL beaker; adding 4-5 mL of the mixed acid solution obtained in the step (1), heating until the solution is completely dissolved, evaporating until the solution is nearly dry, adding 2-3 mL of 2mol/L nitric acid solution (2), and fixing the volume;
diluting the solution in the step (7);
transferring a certain volume of the sample solution in the step (6) into another volumetric flask, and adding 2mol/L of the nitric acid solution in the step (2) to fix the volume;
step (8) extraction separation;
transferring 1mL of the sample dilution liquid obtained in the step (7) into an extraction tube, transferring a certain volume of the sodium nitrite solution obtained in the step (4), transferring 1mL of the TOPO solution obtained in the step (3) into the extraction tube by using a sampler, mixing for 3-5 min, centrifuging for 1min, and discarding the water phase;
step (9) sample preparation;
transferring a certain volume of the organic phase solution in the step (8) into a small disc, drying the small disc again, taking down and cooling to room temperature;
step (10) sample measurement;
opening an alpha spectrometer; measurement step (9) sample tray alpha count (N) was measured on an alpha spectrometer 1 ) Stainless steel trays without sample reagent were measured sequentially, i.e. blank count (N 0 ) Standard disc counts (N b ) Measuring sample count (N 1 );
The plutonium content of the neptunium dioxide sample of step (11) is calculated according to formula (1):
wherein:
c-measurement of the content of plutonium in neptunium dioxide, mu gPu/gNpO 2 ;
V 0 Moving the volume of the organic phase sample from the tray to mL;
V 1 -organic phase sample volume, mL, before extraction;
V 2 -neptunium removed by extraction dissolves the sample volume, mL;
V 3 -neptunium sample is dissolved and then the volume is fixed, and the volume is mL;
m s -plutonium content in standard disc, μg;
N b -the counting rate of plutonium in standard discs;
n—count rate of plutonium in sample disc;
N 0 -blank disc count rate;
n-dilution of the solution;
m-is called NpO 2 Quality of the product, mg.
In the step (1), deionized water is used for constant volume.
In the step (2), deionized water is used for constant volume.
In the step (3), a one-ten-thousandth or one-ten-thousandth analytical balance is adopted to weigh a certain mass of analytically pure TOPO solid.
In the step (4), sodium nitrite with certain mass is weighed by adopting a one-ten-thousandth or one-ten-thousandth analytical balance.
In the step (5), drying is performed under an infrared lamp.
In the step (6), heating is placed on an electric heating plate.
In the step (8), mixing for 3-5 min on a vortex mixer, centrifuging for 1min in a low-speed table type centrifuge, and discarding the water phase.
In the step (9), preheating is carried out for 30min.
In the step (11), the data calculation is modified according to GB/T8170, the result keeps three valid digits, and the result is reported as the average value of the two measurement results.
The invention has the remarkable effects that: the damage of the radioactivity of the sample to the operator is reduced, and the measurement error caused by the influence of americium element on the plutonium content measurement is eliminated. The analysis method for measuring the content of the plutonium in the neptunium can be used for measuring the content of the plutonium in neptunium products of power stack spent fuel post-treatment plants, the precision of the analysis method is better than 10%, and the labeling recovery rate is between 80% and 110%. The TOPO extraction and separation method has good separation effect of plutonium in neptunium, can meet the requirement of measuring the plutonium content in neptunium sample solution, and has the advantages of small interference of alpha energy spectrum measurement, few influence factors and good detection effect.
Detailed Description
Example 1
An analytical determination method for the plutonium content of a neptunium dioxide sample, comprising the following steps:
(1) Preparation of nitric acid hydrofluoric acid mixed acid solution
Measuring a certain volume of analytically pure nitric acid solution by using a measuring cylinder, adding the solution into 10-20 mL of water while stirring, then transferring the solution into a volumetric flask by using a sampler, cooling, and then transferring the solution into the volumetric flask to fix the volume by using deionized water.
(2) Nitric acid solution
Taking a certain volume of analytically pure nitric acid into 20-30 mL of deionized water by using a sampler, cooling to room temperature, transferring to a volumetric flask, and fixing the volume by using the deionized water.
(3) TOPO-xylene solution
A certain mass of analytically pure TOPO solid is weighed by adopting a ten-thousandth or ten-thousandth analytical balance, dissolved in 10 mL-20 mL of dimethylbenzene, and transferred to a volumetric flask to be fixed in volume by using the dimethylbenzene.
(4) Sodium nitrite solution
And weighing a certain mass of analytically pure sodium nitrite by adopting a ten-thousandth or ten-thousandth analytical balance, dissolving in 10-20 mL of deionized water, transferring to a volumetric flask, and fixing the volume by using the deionized water.
(5) Preparation of plutonium standard discs
And (3) taking 0.1-0.2 mL of plutonium solution with known content in a stainless steel small disc by using a sampler, drying under an infrared lamp, drying on an electric furnace, and measuring and counting on an alpha spectrometer.
(6) Sample dissolution
10mg to 40mg neptunium dioxide samples were weighed in 25mL beakers using a ten-thousandth analytical balance. Adding 4-5 mL of the mixed acid solution (1), placing and heating on an electric plate until the solution is completely dissolved, evaporating until the solution is nearly dry, adding 2-3 mL of 2mol/L nitric acid solution (2), and transferring into a volumetric flask for constant volume.
(7) Dilution of the solution
And (3) taking a certain volume of the sample dissolving solution (6) by adopting a sampler, adding 2mol/L nitric acid solution (2) into another volumetric flask, and fixing the volume.
(8) Extraction separation
1mL of sample dilution (7) is moved into an extraction tube by a sampler, a certain volume of sodium nitrite solution (4) is moved by the sampler, 1mL of TOPO solution (3) is moved by the sampler, the mixture is mixed for 3-5 min on a vortex mixer, and then the mixture is put into a low-speed table centrifuge for centrifugation for 1min, and the water phase is discarded.
(9) Sample making disc
A volume of the organic phase solution (8) was removed in a small stainless steel dish. And (3) placing the small tray under an infrared lamp for drying, then baking at a high temperature on an adjustable electric furnace, taking down and cooling to room temperature.
(10) Sample measurement
The alpha spectrometer was turned on and preheated for 30min. The measuring source disk (9) measures alpha counts on an alpha spectrometer and sequentially measures blank counts, standard counts and sample counts.
(11) Calculating the content of plutonium in neptunium dioxide samples from the measured counts
Example 2
A method for determining the plutonium content in a sample of neptunium dioxide, the specific determination steps comprising the steps of:
(1) Preparation of nitric acid hydrofluoric acid mixed acid solution
A100 mL measuring cylinder is used for measuring 70mL of analytically pure nitric acid solution in a 100mL beaker containing 10mL to 20mL of deionized waterThen 0.3mL of analytically pure hydrofluoric acid solution is added by a 1mL adjustable sampler, cooled to room temperature, transferred into a 100mL volumetric flask, and the volume is fixed by deionized water. The prepared nitric acid hydrofluoric acid mixed acid solution is 11mol/L HNO 3 -0.08mol/L HF。
(2) Nitric acid
15mL of analytically pure nitric acid is measured in a 100mL beaker containing 20mL to 30mL of deionized water by a 25mLL measuring cylinder, cooled to room temperature, transferred to a 100mL volumetric flask, and the volume is fixed by the deionized water, and the concentration of the prepared nitric acid is 2.0mol/L to 2.3mol/L.
(3) TOPO-xylene solution
0.7328g of analytically pure TOPO is weighed by a ten-thousandth or ten-thousandth analytical balance, dissolved in 10 mL-20 mL of dimethylbenzene, transferred to a 100mL volumetric flask, and fixed in volume by the dimethylbenzene, and the concentration of the prepared TOPO solution is 0.18 mol/L-0.22 mol/L.
(4) Sodium nitrite solution
13.8g of analytically pure sodium nitrite is weighed by adopting a ten-thousandth or ten-thousandth analytical balance, dissolved in 10 mL-20 mL of deionized water, transferred to a 100mL volumetric flask, and fixed in volume by using deionized water, and the concentration of the prepared sodium nitrite solution is 1.9 mol/L-2.1 mol/L.
(5) Preparation of plutonium standard discs
Transferring 0.1mL of plutonium solution with known content into stainless steel small tray by sampler, oven drying under 250W infrared lamp, oven drying in 1000W adjustable electric furnace, and collecting plutonium standard tray with plutonium content of 1.0X10 -7 mg~5.0×0 -7 mg。
(6) Sample dissolution
10mg to 40mg neptunium dioxide samples were weighed in 25mL beakers using a ten-thousandth analytical balance. Adding 4-5 mL of the mixed acid solution (1), placing on a 170 ℃ electric plate for 1 hour until the sample is completely dissolved, transferring into a 10mL volumetric flask, and fixing the volume by deionized water.
(7) Dilution of the solution
1mL of the sample solution (6) is removed by a 1mL adjustable sampler into another 10mL volumetric flask, and 2mol/L nitric acid solution is added for volume determination.
(8) Extraction separation
1mL of sample dilution (7) is moved into a 5mL extraction tube by adopting a 1mL adjustable sampler, 0.1mL of sodium nitrite solution (4) is added by adopting a 0.1mL adjustable sampler, 1mL of TOPO solution (3) is moved into the 1mL adjustable sampler, the mixture is mixed for 3 to 5min on a 40W 2400 rpm vortex mixer, and then the mixture is put into a 10mL X6 4000 rpm low-speed table centrifuge for centrifugation for 1min, and the water phase is discarded.
(9) Sample making disc
Remove 0.2mL of organic phase solution (8) in a stainless steel dish. And (5) placing the small tray under an infrared lamp for drying, then baking at a high temperature on an electric furnace, taking down and cooling to room temperature.
(10) Measurement
The alpha spectrometer was turned on and preheated for 30min. The measurement source disk (9) measures the alpha count (N) on an alpha spectrometer 1 ) Stainless steel trays without sample reagent were measured sequentially, i.e. blank count (N 0 ) Standard disc counts (N b ) Measuring sample count (N 1 )。
(11) Result calculation
The content of plutonium in the neptunium dioxide sample is calculated according to formula (1):
wherein:
c-measurement of the content of plutonium in neptunium dioxide (. Mu. gPu/gNpO) 2 );
V 0 -moving the organic phase sample volume, (mL) out of the tray;
V 1 -organic phase sample volume before extraction, (mL);
V 2 -neptunium removed by extraction dissolves the sample volume, (mL);
V 3 -the neptunium sample is dissolved and then the volume is fixed, (mL);
m s plutonium content in standard disc, (μg);
N b -the counting rate of plutonium in standard discs;
n—count rate of plutonium in sample disc;
N 0 -blank disc count rate;
n-dilution of the solution;
m-is called NpO 2 Product-like quality, (mg).
The data calculation is modified according to GB/T8170, the result keeps three valid digits, and the result is reported as the average value of the two measurement results.