Introduction

Radiotracers come on the scene

The first use of radiotracers happened almost by accident. In 1912, two Austrian-Hungarian chemists G. de Hevesey and F.A. Paneth, research students at Professor Rutherford's Manchester laboratory, were challenged by Rutherford to demonstrate their chemical skills by separating minute traces of radium-D, as it was then known, from the lead with which it was associated and which had been derived from uranium deposits. They worked hard for two years but had to conclude that radium-D and lead must belong to a group of ‘practically inseparable substances’ later known as isotopes.

De Hevesey, a future Nobel Laureate, then conceived the idea of adding radium-D (subsequently identified as 210Pb, a β particle emitting isotope of lead), to bulk lead and use the emitted β particles to trace sparingly soluble lead salts. It worked ‘like a charm’ and was the first example of radio-tracing. Applications to many aspects of chemistry, biology and agriculture soon followed. Through the 1920s, progress was limited by the fact that the only radiotracers available were those separated from naturally radio- active materials. This was to change dramatically in the following years with:

• the discovery of artificial radioactivity by Frederick Joliot and Irene Joliot-Curie (early in1933);

• the construction in 1932 of the first cyclotron designed to produce radionuclides by M. S. Livingston and E. O. Lawrence;

• the discovery of neutron activation by Enrico Fermi in the mid-1930s (Section 1.3.3); and

• the construction in 1942 of the Chicago pile (nuclear fission reactor), by a team also led by Enrico Fermi, which opened the doors for the large scale production of radiotracers (Section 1.3.3).