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Radioactivity standards at the BIPM

A brief history of international radium standards at the BIPM



  September 1910

The Radiology Congress met in Brussels and established the International Radioactivity Commission (Commission Internationale de Radioactivité). Mme M. Curie was asked to prepare an International Radium Standard.

  18 March 1912

A. Debierne addressed a letter to Ch.-Éd. Guillaume (then Deputy Director of the BIPM) asking him if the BIPM would be willing to keep the Radium Standard.

  12 May 1912

S. Meyer, secretary of the Commission Internationale des Étalons de Radium, thanked R. Benoît, Director of the BIPM, for agreeing to keep the standard.

  21 February 1913

The standard was deposited "in the lower division of the safe located in the first vault".

  1913 to 1935

Eight times in total the international standard was taken out for various comparisons at the Laboratoire Curie and brought back to the vault at the BIPM. After being used for the last time it was kept at the Laboratoire Curie.

  1934

O. Hönigschmid prepared twenty radium standards from pitchblende, originating from High Katanga, containing a high percentage of radium free of mesothorium. Among them, standard No. 5430, with a mass almost identical to that of the "Curie standard", was assigned to France and handed over to the Laboratoire Curie.

  21 April 1939

Standard No. 5430 was deposited at the BIPM.

  30 May 1940

The standard was transferred to a place outside Paris for safe keeping.

  October 1948

At the 9th CGPM the Soviet delegation proposed to "organize comparisons of national standards of radium with international standards of radium and to maintain these at the Bureau International".

  July 1953

The Joint Commission for Radioactivity (Commission mixte de radioactivité), meeting in Stockholm, entrusted standard No. 5430 to the Director of the Radium Institute (Institut du Radium).

  3 December 1959

The Faculty of Sciences of Paris, to which the Radium Institute belonged, decided to entrust the BIPM with the radium standard No. 5430. This standard remained the "property of the University of Paris".

  October 1960

The 11th CGPM authorized the BIPM to maintain radium standard No. 5430.

  9 March 1961

The University of Paris donated the standard to the BIPM and an international comparison of radium standards was organized in 1963. Later, primary measurement methods and the introduction of the SI definition for activity replaced the need to hold such standards.

  22 January 1993

Having kept the artefact safely at the BIPM for a further thirty-two years, the radium standard 5430 was finally disposed of as radioactive waste, by the French authorities, following international safety recommendations.



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