Work on decommissioning an 'active handling' building on the Harwell Business Centre site is being restarted after four workers inhaled dust-like radioactive particles.

The incident happened in April as contractors were dismantling a shield facility - or cell - where staff formerly dealt with radioactive materials behind a protective shield.

In a statement issued at the time, the Atomic Energy Authority said: "During decommissioning operations, monitoring equipment indicated unexpected levels of alpha activity."

Dr John Wilkins, UKAEA head of site at Harwell, said that as part of the decommissioning, a protective covering was installed within the building from which there was a release of radioactive particles into the larger building. A check on staff revealed "four operatives inhaled a dose of between one and two millisieverts of radioactivity".

Dr Wilkins described it as a "safe level" with no danger to health as the maximum annual permitted dose for nuclear workers is 20 millisieverts.

But work on the single-storey 1950s building has been at a standstill for more than two months while inquiries were held by the UKAEA and the Government's Nuclear Installations Inspectorate.