THE operator of Australia's only nuclear reactor will cut 80 staff and trim its costs to meet about $10 million in savings required by the Federal Budget.

The Australian Nuclear Science and Technology Organisation (ANSTO) says an organisational restructure is needed, especially in the wake of the Budget.

The organisation is the centre of Australia's nuclear science capabilities and expertise and runs the Lucas Heights research reactor in Sydney.

"ANSTO has to meet its core operational, scientific and research objectives in an environment of increasing costs and budget constraints," a spokeswoman said in a statement.

"To achieve this across the organisation there will be reductions in fixed costs and around 80 staff of ANSTO's workforce of 1009."

ANSTO would refocus its activities on its core functions in both the research and operational areas, the spokeswoman said

All members of ANSTO's staff were briefed this morning on the restructure.

"The restructure will initially involve a process of inviting staff to express interest in voluntary redundancy," she said.

"It is with regret that ANSTO takes these measures and recognises the next couple of months will be a stressful time for its staff."

Community and Public Sector Union (CPSU) national secretary Stephen Jones later said the 80 jobs represented close to eight per cent of the ANSTO workforce.

"In one sense I'm not surprised. It's usual for departments to move pretty quickly after they become aware of their (Budget) allocations," he said.

"The longer they wait, the higher they accrue a debt. So that's not surprising."

The union was fundamentally opposed to any compulsory redundancies, he said.

"They are calling for voluntaries (but) they don't rule out compulsories," Mr Jones said.

"That's of concern to us.

"These are some of Australia's best research minds in their field and we think it's bad that, as a result of arbitrary Budget cuts, the Commonwealth stands to lose the services of these people."