PRETORIA, South Africa (AP) _ At 21, Vorster Gauche's political hero is Ronald Reagan, his nemesis is Nelson Mandela and his dream is to live in a white nation carved out of black Africa.

Gauche is part of a sizable minority of college students who oppose apartheid's demise and are pushing for a ''No'' vote in the March 17 referendum on political reforms.

President F.W. de Klerk, who says he will resign if the referendum is defeated, was prevented from speaking at the University of the Orange Free State on Monday when right-wing students shouted him down and someone sprayed tear gas.

Last April, students at the University of Pretoria, which Gauche attends, shouted down Mandela, leader of the African National Congress. They're likely to give de Klerk a similar reception when he visits the university on Friday.

''We don't like violence, like throwing tear gas, but to me screaming out in the hallway isn't violence,'' said Gauche, a member of the student chapter of the pro-apartheid Conservative Party.

Gauche said conservative students have been driven to such actions by the government's political reforms and more permissive social laws.

Other students lounging in the university's Conservative office nodded in agreement.

In addition to the breaking down of racial barriers, the students oppose the introduction of nudity on movie screens and Communist literature on bookshelves.

''The government is selling out everything we have, and we feel frustrated. You get out of control,'' said 20-year-old Yolande Burger.

With 23,000 students, the University of Pretoria is the largest in the country and one of the most conservative. It is one of five Afrikaans-language universities in South Africa. Only 61 blacks were enrolled in 1989, the most recent figures available.

Students at the country's English-speaking universities generally are more liberal and support de Klerk's reforms.

Anre Vorster, the 26-year-old chairman of the student Conservative Party chapter, estimates campus membership at 1,500. But he says there are many more supporters who fear being labeled racists if they join.

''The last thing we are is racists,'' Vorster said. ''We just want everyone to have their own land. We want to give the 26 million black people the same opportunities as us. We just don't want them to dictate to us.''

Like the national Conservative Party, student Conservatives envision South Africa being carved into separate black and white nations and point to Yugoslavia and the former Soviet Union as proof different ethnic groups don't belong together.

De Klerk's reforms, they say, will lead to a black, ANC government that would impose Communist rule, crush the Afrikaner culture and ruin the economy.

The left-leaning ANC seeks a multiracial democracy with no special privileges for whites. The ANC is closely aligned with the South African Communist Party and says there must be some redistribution of wealth from whites to blacks. But it says whites will be welcome and needed to help develop the country.

The student Conservatives have similar backgrounds. They come from conservative families but had contact with blacks while growing up.

Several said the turning point in their political lives came in 1983, when the governing National Party expanded parliament to give Indians and people of mixed-race representation.

''South Africa only started to become like a Third World country after reforms started,'' said Vorster, referring to the 1983 change.