Rolf Sievert

Rolf Maximilian Sievert was born with Stockholm on May 6th, 1896. His/her father, Maximillian Sievert, were an industrialist.

In 1914, Rolf Sievert finishes its secondary studies in Stockholm and is registered first of all with the Institut Karolinska then with the Royal Institut of Technology of Stockholm.

It obtains a Master off Science with the Université of Uppsala in 1919.

During the Years 1920, since no standard concerning radiations exists within the various hospitals, Sievert decides to found an organization which in 1925 becomes responsible for the control of the levels of amounts in all the private clinics of Sweden which use radiations as treatment.

Control will very quickly be extended to all the fields touching with the radiations, as well medical as industrial.

Its voluntary co-operation lasts until 1924, date on which Society Cancer of Sweden names it responsible for the Physics laboratory of the Radiations (until 1937).

In 1929, it is on the initiative of the creation of the International commissions on Protections against radiation (ICRP) and to the Units and Measures of Radiations (ICRU).

During the Years 1930, Sievert works on the biological effects due to the ionizing rays. It compares the effects due to low dose received by the radiologists during their daily work, with those caused by the inevitable natural radiation from which nobody escapes.

Many years before the radioactive fallout is not known, Sievert studies the consecutive diseases and pains with the repercussions of ashes of the volcanic eruptions at the Lapons.

It obtains its doctorate in 1932. The title of its thesis is " Eine method zur Messung von Röntgen, Radium und Ultrastrahlung nebst einige Untersuchungen über die Anwendbarkeit derselben in der Physik und der Medizin. MIT einem Anhang enthaltend einige Formeln und Tebellen für die Berechnung der Intensitätsverteilung EIB Gamma-Strahlungsquellen".

He becomes professor associated in medical physics then with the Université with Stockholm. In 1937, the laboratory settles at the hospital of Karolinska and is called from now on " Department of Physics of Rayonnements". The direction is entrusted to him by it and in 1941, he becomes the first professor of the Department of Physics of Medical Radiations, posts that he will occupy until 1965.

Sievert contributes its most important share to clinical physics by developing the bases for calculation of the absorptive Doses necessary to the care of the Tumeur S. It highlighted in particular the important contribution of the secondary radiations.

He invented in addition many instruments making it possible to measure the administered doses, like the room of Sievert.

On the initiative of Sievert, the Swedish government deposits the first law on the protection of the ionizing rays in 1941, entrusting its application to the Department of Physics of Radiations.

From 1956 to 1962, it directs the ICRP, then takes the direction of UNSCEAR (United Nations Commission one the Effects off Atomic Radiation) of 1958 to 1962.

During its retirement, it was occupied actively, as well at the national level as international, of the protection against radiation and measurements of radiations, fields in which it played a part of pioneer.

Rolf Sievert died on October 3rd, 1966 with Stockholm.

The room of Sievert is made of two spheres or concentric cylinders composed of an alloy of Magnésium. A electrode isolated is connected to the interior sphere which can be carried to a given potential. When the room is exposed to an ionizing ray, the air of the cavity ranging between the two spheres becomes conducting by the formation of pairs of ions, it follows a Leakage current which tends to decrease the potential of the internal room. There exists thus a relation between the pressure loss, easily measured, and the quantity of radiation received by the room.

The size of the room can be a few millimetres only, which makes it easily easy to handle.

In the honor of Rolf Sievert, resolution 5 of XVIe International Conference of the Weights and Mesures (CGPM) of 1979 defines Sievert (Sv), inside the system IF, as being the unit of equivalent Dose of ionizing radiations. 1 Sv = 1J/kg

Sievert is used to measure the effective amount or " équivalente" of radiation received by a biological fabric.

The various kinds of radiation having different effects on living tissue, a simple measurement of received energy (in Gray) does not give a clear indication of the probable biological effect of these radiations. The equivalent amount in Sievert is equal to the amount expressed in Gray, multiplied by a factor loading which increases with the dangerosity of radiations and the sensitivity of implied biological fabrics.

An effective amount of 1 Sievert requires Gray for gamma rays or beta but only 0,05 Gray for alpha radiations or 0,1 Gray for neutron radiations of average energy.

One more often uses the milliSievert more in connection with the amounts concerning the man.

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