Board of Governors of the International Atomic Energy Agency stopped adding countries to the board from 1957 to 1961 classified into different categories such as ten most advanced, continuing members, and elected by the General Conference.
The International Atomic Energy Agency (IAEA) is an international organization that seeks to promote the peaceful use of nuclear energy, and to inhibit its use for any military purpose, including nuclear weapons. The Board of Governors of the International Atomic Energy Agency (IAEA) is one of the two policy making bodies of the IAEA, along with the annual General Conference of IAEA members. Thirteen were designated by the previous Board as either one of the ten countries that are the most advanced in atomic energy technology plus the most advanced from any of the eight regional groups not represented by the first ten. 1957 Argentina
Australia
Brazil
Canada
Czechoslovakia
France
Guatemala
India
Indonesia
Italy
Japan
South Korea
Pakistan
Peru
Portugal
Romania
Sweden
Turkey
South Africa
USSR
United Arab Republic
United Kingdom
United States 1958 Australia
Brazil
Canada
France
India
Japan
South Africa
USSR
United Kingdom
United States Belgium
Denmark
Poland Argentina
South Korea
Pakistan
Romania
Turkey Netherlands
United Arab Republic
Indonesia
Venezuela
Peru 1959 as above 1960 as above 1961 as above 
