The estimated cost of the Superconducting Super Collider, potentially the nation's largest and most expensive scientific device, has gone up again. The SSC's new price tag is likely to be $8.6 billion, according to Department of Energy advisers who are to meet today to complete their estimate.

Earlier this year, DOE officials acknowledged that the cost would probably climb from $5.9 billion to $8 billion, because of recommendations that the collider be extensively redesigned and enlarged. When the SSC was first seriously proposed three years ago, the cost was put at $4.4 billion.

Construction has not begun on the site south of Dallas, where the machine will sling subatomic particles through a 54-mile round tunnel lined with superconducting magnets. The SSC is designed to answer fundamental questions about the origin and nature of matter, but most scientists concede it will have little practical value.

The higher price, discussed by DOE officials yesterday, is bound to revive controversy over the wisdom of building the mammoth scientific apparatus. While the project appears to have strong support in appropriations committees in Congress, which awarded the SSC the Bush administration's full request this year of $318 million, political and scientific critics of the SSC charge that it is going to rob other worthy research of funding.

While physicists specializing in the search for new subatomic particles favor building the collider, many physicists working on other problems are strongly opposed.

In a news conference yesterday, Deputy Energy Secretary W. Henson Moore said four groups were attempting to analyze the cost of the collider. He said estimates ranged from $7.8 billion by the SSC contractor to $8.6 billion by the High Energy Physics Advisory Panel, an independent group that assists DOE.

The higher cost was largely the result of the physics panel including more contingency funds in its estimate, Moore said. The extra funds would be used to offset cost of delays and technological problems in developing the superconducting magnets and the special injectors used to create and propel subatomic particles in the SSC.

Moore stressed that the delays, and their increased costs, could be caused by Congress stretching out the project.

Rep. Sherwood L. Boehlert (R-N.Y.), however, issued a statement that "the greatest threat to this project is not, despite the {energy} department's attempts to imply otherwise, some irrational, delaying tactic by Congress. The threat to this project remains -- as it should -- the department's overly optimistic assessments of this project's costs and benefits."

Moore said the SSC contractor, University Research Associates, committed itself to building the machine for $7.8 billion. "We will go with what the contractor says," Moore said. "We will hold them to this."

Members of physics panel, however, said they stood by the higher estimate. "This is what experience tells us you will need. It's not hypothetical. This is what the committee thinks the project will end up costing," said Hermann Grunder, a member of the panel and director of the Continuous Electron Beam Accelerator Facility in Newport News, Va.

Grunder said the physics panel included greater contingency funds because the SSC must be built from scratch by an untested and still incomplete laboratory in Texas. "The figure acknowledges that they have an enormous task in front of them," Grunder said.

Moore said the various cost estimates, including those of the physics panel announced yesterday, will be compared by DOE managers to produce a final "hard number" for Congress next month.