The Virginia Board of Corrections, moving to end an embarrassing dispute with the state's new prisons director, today endorsed his plan to abolish a controversial program at the troubled Mecklenburg prison.

"We're trying to turn that place around and get a manageable institution," said Director Allyn R. Sielaff, emerging from a closed-door session with the board.

The board later publicly voted full confidence in Sielaff, the third person to head the state's prisons under Gov. Charles S. Robb.

The vote marked a reversal of the board's position. On Dec. 31 board members voted in an unusual, closed session to order Sielaff to delay his previously announced plan to scrap a so-called behavior modification plan at Mecklenburg.

The board said then that Sielaff's proposal ran counter to recommendations of a board committee that had investigated Mecklenburg after the escape May 31 of six death-row inmates and other inmate disturbances.

Under Sielaff's plan, the Mecklenburg prison will abolish a program that treats disruptive inmates harshly and gradually restores their privileges only as they improve their behavior.

Instead, according to Sielaff's plan, disruptive inmates will be segregated from other inmates at Mecklenburg. They will still receive basic privileges, but under more restrictive conditions, and they will still be allowed to resume routine living conditions by improving their behavior.

Sielaff and other officials said "it is a great myth" that the behavior modification plan worked. Sielaff said inmates were often denied privileges but rarely given incentives to behave well.

The changes by Sielaff were hailed by the National Prison Project of the American Civil Liberties Union, which is suing the state over its alleged failure to implement provisions of a 1983 court-approved consent decree on the operation of Mecklenburg.

The board's action Dec. 31 was seen as a rebuff to Sielaff, who had assumed the job only in late November after months of turmoil within the Department of Corrections.

The board, which is supposed to set policy for the Department of Corrections, indicated then that Sielaff had exceeded his authority as director and was making policy changes without their approval.

Several Democratic legislators, already worried that Republicans will use the prisons issue against them in the fall elections, have told board members they should play a more aggressive role in setting policy and not just react to the director's actions.

Board member Carroll E. Lillard of Madison County declined to comment today on those criticisms. He said the board went ahead with the Sielaff plan after reviewing information from Sielaff and the American Correctional Association. The association said behavior modification programs have largely been discredited as effective prison policy.

The board also voted to ask the legislature to provide money this year to plan a new 300-bed prison and mental hospital for acute psychotic inmates. There was no indication where the hospital might be built, and the issue was considered separately from plans for construction of a new maximum-security facility.

The board also heard a report on a new study by the staff of the Joint Legislative Audit and Review Commission that was highly critical of the state's prison operations.

Sielaff said he was still being briefed on the report, which suggested the department needs better training and management rather than more security guards, and he declined comment on it today.