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This method describes the determination of radium (Ra-226) in water solutions working without interferences from other radium isotopes or radionuclides. For solid samples special chemical treatment is necessary.
The method of Ra-226 determination uses the a-radiation from its progenies
The method includes the following steps:
To avoid adsorption the sample should have pH = 1 by adding 10 ml 14 mol/l nitric acid per liter sample. In laboratory the samples are filtrated.
To a 1 liter sample the following chemicals are added:
The solution is heated to boiling. From the hot solution the sulfates are precipitated by adding 2,5 ml sulphuric acid (9 mol/l). Wait overnight and decant from the solution. The precipitation is to be washed with distilled water and centrifuged two times. Leave the precipitation in the centrifuge glass.
The precipitation is dissolved with 5 ml Na4EDTA (0,5 mol/l) by use of a water bath in the heat and quantitatively transferred to a de-emanation tube. The end volume of the solution in the tube is about 25 ml.
3. Buildup phase
The solution is de-emanated completely from Rn-222 by bubbling with
nitrogen for about 5 min. At the end the tube is set under vacuum with a pump.
The end-point of the procedure is the date/time ´First de-emanation after
sample preparation´. This is equal to the start point of Rn-222 buildup. After
7 days about
4. Transfer of Rn-222
Attach a scintillation chamber as well as the sample tube to the
apparatus. With the vacuum pump on open
Measure the chamber by use of the analysis ´Ra-226 in liquid´ of the counter program. Ensure that a well nitrogen flushed chamber is used for analysis. Before each analysis the actual chamber background can be determined by an overnight measurement.