RU2498296C1 - Method of determining specific activity of strontium-90 and caesium-134 or caesium-137 radionuclides in milk or milk whey - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of determining specific activity of strontium-90 and caesium-134 or caesium-137 radionuclides in milk or milk whey involves preparing a starting sample for analysis by mixing milk or milk whey with a sorbent, depositing radionuclides on the sorbent, separating the sorbent from the milk or milk whey, washing and drying the sorbent, measuring specific activity of the radionuclides in the sorbent, the method being characterised by that the sorbent added to milk or milk whey is manganese dioxide, and specific activity of strontium-90 and caesium-134 or caesium-137 radionuclides in milk or milk whey is determined using the equations: Q₁=A_meas.·m_s/M_pr.·K_Sr-90, Q₂= A_meas.·m_s/M_s·K_{Sr-134 or 137}, where: Q₁ is the specific activity of the strontium-90 radionuclide in milk or milk whey, Bq/g, Q₂ is the specific activity of the caesium-134 or caesium-137 radionuclide in milk or milk whey, Bq/g, A_meas. is the specific activity of the strontium-90 or caesium-134, 137 radionuclides in the sorbent, Bq/g; m_s is the mass of the washed and dried sorbent after contact with milk or milk whey, g; M_s is the mass of the milk or milk whey sample in contact with the sorbent, g; K_Sr-90 is the sorption coefficient of strontium-90 from milk or milk whey on the manganese dioxide sorbent, K_{Cs-134 or Cs-137} is the sorption coefficient of Cs-134 or Cs-137 from milk or milk whey on the manganese dioxide sorbent, wherein the sorption coefficients of strontium-90 or caesium-134 or caesium-137 from milk are equal to 0.4-0.6 and 0.8-0.9, respectively; and the sorption coefficients of strontium-90 and caesium-134 or caesium-137 from milk whey are equal to 0.8-0.9 and 0.8-0.98, respectively.

EFFECT: method enables fast and accurate calculation of activity of strontium-90 and caesium-134 or caesium-137 radionuclides in milk or milk whey.

4 tbl, 2 ex

Description

The invention relates to the study and analysis of dairy products and can be used to determine the specific activity of radionuclides of strontium-90 (Sr-90) and cesium-134 (Cs-134) or cesium-137 (Cs-137) in milk or whey.

A known method for the determination of radioactive strontium-90 in milk, involving the preparation of an initial milk sample for analysis by precipitation of proteins with hydrochloric acid, separation of serum with a given pH value, the conversion of strontium from serum into the analyzed sample and measuring its activity. In this case, the transfer of strontium-90 from serum to the analyzed sample is carried out by introducing titanium phosphate in the Sr form as a sorbent in pH 1.5 as a sorbent, after which it is washed and the activity is measured directly in the sorbent.

(see RF patent No. 1032888)

The disadvantage of this method is that it contains many operations, time-consuming, requires additional consumption of chemicals for the precipitation of milk proteins and allows you to determine only strontium-90.

Closest to the claimed technical essence and the set of essential features is a method for determining the specific activity of strontium-90 (Sr-90) radionuclide in milk by the yttrium-90 (Y-90) daughter element by precipitation of Sr-90 and Y- ions contained in milk 90 ammonium salt of inositol hexaphosphoric acid and measuring the activity of strontium-90 (Sr-90) on a beta spectrometer of the Progress radiometric complex.

(see RF patent No. 2139534)

However, this method allows only Sr-90 to be determined from Y-90. To carry out the sorption of Sr-90 with a salt of inositol hexaphosphoric acid (hereinafter - IHPA), it is necessary to acidify milk 6 M HCl to a pH of 4.4 ± 0.2 at a temperature of (2 ± 1) ° С. After that, the prepared milk sample is brought into contact with the IGFC salt by shaking, subsequent separation, washing, drying and determining the specific activity of the sorbent.

The specific activity of the sorbent, its sorption coefficient from milk is determined by calculation by the specific activity of Sr-90 in milk.

The disadvantages of the method is the operation of acidification of milk and bringing its pH to 4.4 ± 0.2 with mandatory cooling to a temperature of (2 ± 1) ° C; the ability to determine in milk only one radionuclide Sr-90.

The objective of the invention is the development of a method for determining the specific activity of the strontium-90 (Sr-90) radionuclide in milk or whey by the daughter element of yttrium-90 (Y-90) and cesium-134 (Cs-134) or cesium-137 (Cs-137 ) by precipitation of Sr-90 and Y-90, Cs-134 or Cs-137 ions contained in milk or serum with manganese dioxide and measuring the activity of the sorbent according to Sr-90 on a Progress beta-spectrometer of a radiometric complex, and Cs-134 or Cs -137 - on a Progress gamma-ray spectrometer.

The problem is solved by developing a method for determining the specific activity of strontium-90 and cesium-134 or cesium-137 radionuclides in milk or whey, which includes preparing the original milk samples for analysis by mixing for a certain time milk or whey with a sorbent in a ratio of not more than than 10: 1 and particle sizes of the sorbent not more than 0.5 mm, without changing the initial acidity of the preparations, deposition of radionuclides on the sorbent, separation of the sorbent from milk or whey, washing and under drying the sorbent, measuring the specific activity of radionuclides in the sorbent, characterized in that manganese dioxide is introduced into milk or milk serum without changing the acidity of their environment, and the specific activity of strontium-90 and cesium-134 or cesium-137 radionuclides in milk or milk serum is determined from the equations:

Q ₁ = A _meas. M _s / M _ave. K _Sr-90 , Q ₂ = A _meas. M _s / M _ave. K _{Cs-134 or Cs-137} , where:

Q ₁ - specific activity of strontium-90 radionuclide in milk or whey, Bq / g;

Q ₂ - the specific activity of radionuclides of cesium-134 or cesium-137 in milk or whey, Bq / g;

A _rev. - the specific activity of radionuclides of strontium-90 or cesium-134 or cesium-137 in the washed and dried sorbent after contact with milk or serum, Bq / g;

m _s - mass of washed and dried sorbent after contact with milk or whey, g;

M _Ave - the mass of a sample of milk or whey in contact with the sorbent, g;

K _Sr-90 - coefficient of sorption of strontium-90 from milk or whey on a sorbent - manganese dioxide;

K _{Cs-134 or Cs-137} is the sorption coefficient of Cs-134 or Cs-137 from milk or whey on a sorbent - manganese dioxide.

When implementing the method, a technical result is achieved that the use of manganese dioxide as a sorbent ensures the deposition of strontium-90 and cesium-134 or cesium-137 radionuclides on it without changing the initial acidity of the medium at an uncontrolled temperature, without the use of additional reagents.

The method is as follows.

Sorbent, manganese dioxide, is introduced into milk or whey in a ratio of 1:10, the resulting mixture is stirred for 45-90 minutes. by shaking or shaking to evenly distribute the sorbent throughout the volume of milk or whey, filter the sorbent through a paper or double dacron filter, rinse with distilled water, and dry at a temperature of 140-150 ° C to a mass not exceeding the initial mass of the sorbent. The specific activity of the sorbent is measured on any recording device, in particular on the Progress gamma and beta spectrometric complex.

Based on the specific activity of the sorbent and its sorption coefficient from milk or whey, the specific activity of Sr-90 or Cs-134 or Cs-137 in milk or whey is calculated from the equations:

Q ₁ = A _meas. M _s / M _ave. K _Sr-90 , Q ₂ = A _meas. M _s / M _ave. K _{Cs-134 or Cs-137} , where:

Q ₁ - specific activity of strontium-90 radionuclide in milk or whey, Bq / g;

Q ₂ - the specific activity of radionuclides of cesium-134 or cesium-137 in milk or whey, Bq / g;

A _rev. - the specific activity of radonucdides Sr-90 or Cs-134 or cesium-137 in the washed and dried sorbent after contact with milk or serum, Bq / g;

m _s - mass of washed and dried sorbent after contact with milk or whey, g;

M _Ave - the mass of a sample of milk or whey in contact with the sorbent, g;

K _Sr-90 - coefficient of sorption of strontium-90 from milk or whey on a sorbent - manganese dioxide;

K _{Cs-134 or Cs-137} is the sorption coefficient of cesium-134 or cesium-137 from milk or whey on a sorbent - manganese dioxide.

Example 1. To 50 g of milk add 5 g of manganese dioxide, mix manually or on a shaker for 60 minutes, filter the sorbent through a paper or double lavsan filter, wash with 50-70 ml of distilled water, and dry at a temperature of 140-150 ° С to a mass not exceeding 5 g. The specific activity of the sorbent is measured on the Progress gamma and beta spectrometric complex.

The specific activity of Sr-90 or Cs-134 or Cs-137 in milk is calculated according to the above equations.

The sorption coefficients of Sr-90 and Cs-134 or Cs-137 from milk on manganese dioxide obtained experimentally correspond to the following values:

K _Sr-90 = 0.51 ± 0.04;

K _{Cs-134 or Cs-137} = 0.82 ± 0.03.

The values of the sorption coefficients of radionuclides from milk on manganese dioxide are shown in Tables 1, 2.

To determine the sorption coefficients of radionuclides on manganese dioxide, calculated amounts of Sr-90 and Cs-134 or Cs-137 were introduced into a milk or whey sample. After measuring the specific activity of milk or serum on the Progress beta, gamma-spectrometric complex, the total activity in the milk or serum sample in contact with the weighed portion of the sorbent was found (Asum., Bq = Aud., Bq / g × m samples, g).

Then, the specific and total activity of the washed and dried sorbent after contact with milk or serum was measured. The sorption coefficients of radionuclides on manganese dioxide were determined by the formula:

Korbts. = Asum. washed and dried sorbent, Bq / Asum. milk or whey samples, Bq

Example 2 To 80 g of whey add 8 g of manganese dioxide, mix manually or on a shaking apparatus for 45 minutes, filter the sorbent through a paper or double lavsan filter, wash with 80-90 ml of distilled water, and dry at a temperature of 140-150 ° С to a mass not exceeding 8 g. The specific activity of the sorbent is measured on the Progress gamma and beta spectrometric complex.

The specific activity of Sr-90 or Cs-134 or Cs-137 in whey is calculated according to the above equations.

The sorption coefficients of Sr-90 and Cs-134 or Cs-137 from whey on manganese dioxide, obtained experimentally, correspond to the following values:

K _Sr-90 = 0.8 ± 0.06;

K _{Cs-134 or Cs-137} = 0.70 ± 0.07

The values of the sorption coefficients of radionuclides from serum on manganese dioxide are presented in Tables 3, 4.

Claims (1)

A method for determining the specific activity of strontium-90 and cesium-134 or cesium-137 or cesium-137 radionuclides in milk or whey, including preparing an initial sample for analysis by mixing milk or whey with a sorbent, precipitating radionuclides on a sorbent, separating the sorbent from milk or whey, washing and drying the sorbent, measuring the specific activity of radionuclides in the sorbent, characterized in that manganese dioxide is introduced into the milk or whey as the sorbent, and the specific activity is radionuclide o strontium-90 and cesium-134 or cesium-137 in milk or whey are determined from the equations:
Q ₁ = A _meas . M _s / M _ol · K _Sr-90 , Q ₂ = A _meas . M _s / M _ol · K _{Cs-134 or 137} ,
where Q ₁ is the specific activity of the strontium-90 radionuclide in milk or whey, Bq / g;
Q ₂ - the specific activity of radionuclides of cesium-134 or cesium-137 in milk or whey, Bq / g;
And _ism - specific activity of strontium-90 or cesium-134, 137 radionuclides in the sorbent, Bq / g;
m _s - mass of washed and dried sorbent after contact with milk or whey, g;
M _CR - the mass of the sample of milk or whey in contact with the sorbent, g;
K _Sr-90 - coefficient of sorption of strontium-90 from milk or whey on a sorbent - manganese dioxide.
K _{Cs-134 or Cs-137} - coefficient of sorption of Cs-134 or Cs-137 from milk or whey on a sorbent - manganese dioxide,
while the sorption coefficients of strontium-90 and cesium-134 or cesium-137 from milk are 0.4-0.6 and 0.8-0.9, respectively; and sorption coefficients of strontium-90 and cesium-134 or cesium-137 from whey are respectively 0.8-0.9 and 0.8-0.98.