Radium-226, measurement techniques

TOOHEY, R.E., KEANE, A.T, RUNDO, J., Measurement techniques for radium and the actinides in man at the Center for Human Radiobiology, Health Phys. 44 Suppl. 1 (1983) 323-341. 

Early experiments in liquids were quite variable for many reasons. The conductivity technique, which was used in the gas phase to measure dose, was not applicable to the liquid phase. Reactions were measured using dissolved radium salts or radon gas as the ionization source. Some thought the chemistry was due to the reactions with radium however, it was soon recognized that it was the emitted rays that caused the decomposition. Both radium and radon could cause radiation damage. Because the radon would be partitioned between the gas and liquid phase, the amount of energy that was deposited in the liquid depended critically on the experimental conditions such as the pressure and amount of headspace above the liquid. In addition, because the sources were weak, long irradiation times were necessary and products, such as hydrogen peroxide, could decompose. 

In 1911 Ernest Rutherford asked a student, George de Hevesy, to separate a lead impurity from a decay product of uranium, radium-D. De Hevesy did not succeed in this task (we now know that radium-D is the radioactive isotope °Pb), but this failure gave rise to the idea of using radioactive isotopes as tracers of chemical processes. With Friedrich Paneth in Vieima in 1913, de Hevesy used °Pb to measure the solubifity of lead salts—the first appfication of an isotopic tracer technique. De Hevesy went... 

A key issue when comparing different techniques for measuring SGD is the need to define the fluid composition that each method is measuring (i.e., fresh, saline, or brackish SGD). For example, whereas hydrogeological techniques are estimates of fresh SGD, the radium and radon methods include a component of recirculated seawater. Therefore, it is often not possible to directly compare the utility of these techniques. Instead, they should be regarded as complementary. 

Fig. 2. Isotherm data for radium, uranium(VI) and plutonium sorption onto haematite (using the batch-sorption technique, liquid solid ratio indicated on diagrams). The general form of the data is consistent with a linear sorption mechanism. For information, error bars corresponding to 40% of the measured value are shovra (see text for further discussion of experimental variability).

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