INMATES who have received serious threats will be housed in a 50-bed separation unit at Mountjoy Prison.
A refurbished block for "protection prisoners" will be opened for prisoners who have been the subject of threats, it is understood.
The new accommodation will open following the recent completion of refurbishment on the old block. New in-cell sanitation and secure exercise yards have be installed as part of the refurbishment.
The only inmates to be held there will be those who have been attacked in prison, or been threatened, and the majority of the inmates are expected to be members of Dublin criminal gangs, who are involved in feuds with other outfits.
Justice Minister Dermot Ahern said: "The opening of this Unit will also allow for the introduction of a dedicated area for vulnerable prisoners."
Inter-gang disputes at all of the country's prisons, including Mountjoy, have caused a major security headache for the prison service.
The increasing problem led authorities at Castlerea Prison to abandon a non-segregation policy at the jail last September. Up to that point, the jail was the only one in the country that had a non-segregation policy.
The new accommodation block at Mountjoy Prison had previously been used as a separation unit, but was closed three months ago to undergoing refurbishment. This increased numbers within the general prison population
It is hoped that its re-opening will relieve pressure on these numbers, as is a planned policy of committing prisoners from the city's district courts to other jails in the capital, rather than directly to Mountjoy, as is the current practice.
Under the new prison policy, male offenders committed to prison by the district courts sitting in Dun Laoghaire, Swords, Tallaght, Cloverhill and Blanchardstown will in future be committed to Wheatfield Prison.
But this will only come on stream when a new block for 200 prisoners at Wheatfield Prison is opened.
Details of the planned Wheatfield arrangements were confirmed in the Dail by Justice Minister Dermot Ahern. The new block at that prison is expected to be opened later this year.