MEXICO CITY (AP) _ A Cuban delegation headed by the son of President Fidel Castro on Wednesday signed three agreements to cooperate on peaceful uses of nuclear energy.

''I think there will be a type of collaboration and cooperation that will benefit both countries,'' said Fidel Castro Diaz-Balart, speaking at a news conference in Mexico's capital.

He said the accord showed that Cuba is not as isolated as critics of its hard-line Communist government have alleged since the democratic changes in Eastern Europe and the election defeat of Nicaragua's leftist Sandinistas.

The younger Castro, Cuba's executive secretary for nuclear affairs, said the agreements would promote cooperation in areas ranging from nuclear power to medicine and industry. But no specific projects were mentioned.

Each country has a single nuclear power plant. Mexico's troubled Laguna Verde plant along the Gulf of Mexico uses U.S. technology, while Cuba's nuclear plant in Cienfuegos, about 180 miles southeast of Havana, uses Soviet designs.

In response to questions, Castro said Cuba planned to expand its use of nuclear technology throughout its economy, and intended to build more nuclear power plants.

He noted that Cuba has virtually no oil or coal. ''Practically, we don't have options'' to nuclear power, he said.

Critics say Mexico's Laguna Verde plant uses outdated and dangerous technology, and a U.S. plant based on similar technology has been closed.

Soviet designs such as those used in Cuba have come under increasing criticism both within the Soviet Union and in Eastern Europe, especially following the Soviet Chernobyl nuclear plant disaster in 1986.