Radioactivity 1
Monday 18 July 2011
, Posted by crazy at 09:55
What is radioactivity
Matter consists of tiny particles called “atoms”. The atoms themselves aremade up of a nucleus around which electrons revolve. Some nuclei are stableand their lifetime infinite. Others are unstable, meaning that they changespontaneously while emitting one or more types of radiation. In that case,they are said to be radioactive. Polonium 210, for instance, spontaneously turns into stable lead 206. Some elements have both stable and unstable
isotopes. Carbon is a case in point: carbon 12, the most prevalent isotope,is stable, whereas carbon 14 is radioactive. Other elements – 28 out of the 109 known today – occur only as radioactive isotopes. This is the case for uranium, plutonium and radium
A little history
Henri Becquerel discovered radioactivity in 1896 while doing research on X-rays, which had just been
discovered by Wilhelm Röntgen. In 1898, Pierre and Marie Curie discovered radium and proposed the
word "radioactivity" to describe the phenomenon of radiation. In 1934, Irène and Frédéric Joliot-Curie produced
man-made radioactivity
discovered by Wilhelm Röntgen. In 1898, Pierre and Marie Curie discovered radium and proposed the
word "radioactivity" to describe the phenomenon of radiation. In 1934, Irène and Frédéric Joliot-Curie produced
man-made radioactivity
MESURING RADIOACTIVITY
Radioactivity is a measurable phenomenon. There are three
international units of measure. Each one uses different
types of data
international units of measure. Each one uses different
types of data
The disintegration rate is measuredin becquerel (Bq). This is the number of disintegrations of radioactive nuclei occurring in a sample every second. For instance, about 9,000 atoms disintegrate every second in the body of a person weighing 70 kg. That person’s activity is therefore 9,000 Bq. The former unit was
the curie, which equaled 37 billion becquerel
the curie, which equaled 37 billion becquerel
The amount of radiation absorbed
by an organism or object exposed to radiation
is measured in gray (Gy). This is ameasurement of energy representing 1 joule per kilogram of matter. For example, in the French Massif Central region, an object or a body absorbs 200 billionths of a gray every hour. The gray superseded the rad (1/100th of a gray) in 1986.
• The biological effects of radiationon the exposed organism are measured in sievert (Sv). This is a radiation protection unit. It is expressed in “dose equivalent” and takes into account the
characteristics of the radiation and of the organ irradiated. The sievert superseded therem (1/100th of a Sv) in 1986. The millisievert (mSv), or thousandth of a sievert, is frequently used. Worldwide, the average annual “dose equivalent” from natural radiation is around 2.4 mSv per person
by an organism or object exposed to radiation
is measured in gray (Gy). This is ameasurement of energy representing 1 joule per kilogram of matter. For example, in the French Massif Central region, an object or a body absorbs 200 billionths of a gray every hour. The gray superseded the rad (1/100th of a gray) in 1986.
• The biological effects of radiationon the exposed organism are measured in sievert (Sv). This is a radiation protection unit. It is expressed in “dose equivalent” and takes into account the
characteristics of the radiation and of the organ irradiated. The sievert superseded therem (1/100th of a Sv) in 1986. The millisievert (mSv), or thousandth of a sievert, is frequently used. Worldwide, the average annual “dose equivalent” from natural radiation is around 2.4 mSv per person
