CRIMINAL charges could be brought against the operators of the Dounreay nuclear plant following the fiasco that resulted in power being cut off last month.

The procurator-fiscal in Wick is conducting a full-scale investigation into the incident and has asked for witness statements from employees involved as well as copies of any material that could be used in evidence.

A spokesman for the plant yesterday confirmed that the investigation was under way, saying ''We will co-operate fully.''

Discussions have taken place between the Nuclear Installations Inspectorate and the fiscal's office in Wick, a Crown Office spokesman said, adding that they were ''commonplace'' at this stage of an investigation.

The inquiry follows the extremely embarrassing and potentially catastrophic loss of power to the plant when a contractor working on a digger cut through the main cable. For reasons that have not been fully explained, the back-up power supply failed to kick in. The ventilation system then ceased operating and all 300 non-essential personnel were evacuated.

Management at the Caithness complex denied the breach could have caused a nuclear reaction, but confirmed that the main electricity supply and the back-up supply to the fuel cycle area, where the most dangerous nuclear work is undertaken, were both disrupted for hours.

The area affected included the facility where the controversial cargo of nuclear fuel from Georgia is currently being stored.

Two weeks ago, the Government's nuclear inspectors ordered the shutdown of the entire fuel cycle area, including all its processing and reprocessing plants, until evidence that it can be safely operated is provided.

A Crown Office spokeswoman yesterday said: ''The PF at Wick has been consulted by the NII in relation to the recent incident at Dounreay which led to the loss of power at the plant. Discussions of this nature are commonplace at this stage.''

In January this year, the Atomic Energy Authority was fined #2000 at Inverness Sheriff Court after managers pled guilty to offences under health and safety laws.

The fines related to four workers who breathed in radioactive dust while working for a sub-contractor repackaging rusting drums full of radioactive waste debris in one of Dounreay's ''low active' nuclear waste pits.

The prosecution, the first in the plant's 40-year history, followed a two-year probe involving the NII, the Crown Office, and previous Wick procurator-fiscal Alastair McDonald.

Two weeks ago, a major shake-up of staff was announced at Dounreay following the embarrassing safety lapses.

The majority of changes involved drafting in more staff to key positions in a bid to restore confidence in the operation and strengthen the in-house management team.

Some of the changes, which involve bringing top experts into senior positions from other nuclear establishments and the hiring of another 20 skilled engineers in addition to the 20 recently recruited, reflected the pressure from the NII.

It has been taking a tough line on the UKAEA following the recent lapses.