<P> Only a year after Röntgen's discovery of X rays, the American engineer Wolfram Fuchs (1896) gave what is probably the first protection advice, but it was not until 1925 that the first International Congress of Radiology (ICR) was held and considered establishing international protection standards . The effects of radiation on genes, including the effect of cancer risk, were recognized much later . In 1927, Hermann Joseph Muller published research showing genetic effects and, in 1946, was awarded the Nobel Prize in Physiology or Medicine for his findings . </P> <P> The second ICR was held in Stockholm in 1928 and proposed the adoption of the rontgen unit, and the' International X-ray and Radium Protection Committee' (IXRPC) was formed . Rolf Sievert was named Chairman, but a driving force was George Kaye of the British National Physical Laboratory . The committee met in 1931, 1934 and 1937 . </P> <P> After World War II, the increased range and quantity of radioactive substances being handled as a result of military and civil nuclear programmes led to large groups of occupational workers and the public being potentially exposed to harmful levels of ionising radiation . This was considered at the first post-war ICR convened in London in 1950, when the present International Commission on Radiological Protection (ICRP) was born . Since then the ICRP has developed the present international system of radiation protection, covering all aspects of radiation hazard . </P> <P> The International System of Units (SI) unit of radioactive activity is the becquerel (Bq), named in honor of the scientist Henri Becquerel . One Bq is defined as one transformation (or decay or disintegration) per second . </P>

Which of the following is a spontaneous release of particles or energy from an unstable nucleus