* Saudi Arabia has pledged $100 million to the Special Facility for Sub-Saharan Africa, a fund created by the World Bank to provide concessionary financing for the economic revival of sub-Saharan Africa.

The pledge from the Saudi Fund for Development brings the amount committed to $1.2 billion; 15 countries have joined the World Bank in promising funds.

* Hungary recently became the 133rd member of the International Development Association, the World Bank affiliate for concessionary lending. Its subscription in IDA will be $10 million.

Hungary also became the 127th member of the International Finance Corp. IFC is a World Bank affiliate that works with private investors in commercial enterprises in developing countries. Hungary's subscription in IFC will be $1.4 million.

Hungary has been a member of the World Bank since July 1982.

* The IFC has approved loans of $55 million to a Ghana corporation to cofinance a $158 million, 5 1/2-year program to rehabilitate gold mines in that African nation.

The rehabilitation program is expected to increase Ghana's gold output by 50 percent over the next five years. The program is managed by the Ashanti Goldfield Corp. Ltd., a joint venture between Ghana's government and a British firm, Lonrho. Export-Import Bank

* The Export-Import Bank, the federal agency that supports U.S. exports, has approved a $5.2 million loan to Indonesia to help finance a nuclear power project.

The loan will help finance the $425 million Nuclear Science and Engineering Center, which will provide technical and scientific support for a national nuclear power program.

Atomic Energy of Canada Ltd., the prime contractor, is buying supplies from several U.S. suppliers, including General Electric, Thompson General, Cryofals and Cyclotronics Inc.

The Indonesian government will make a 35 percent cash payment of $2.8 million for the U.S. products. It will finance the remaining 65 percent, or $5.2 million, through an Ex-Im Bank loan with an annual interest of 9.5 percent.