The Nuclear Regulatory Commission voted yesterday to permit limited work on the Seabrook nuclear power plant in New Hampshire to continuenuntil Feb. 18, when it rule on whether all work must halt.

The commission said it would permit excavation. It said it would also allow the bringing of new construction materials onto the site, provided the principal builder, Public Service Co. of New Hampshire, could show that it would otherwise suffer a substantial economic penalty.

In the meantime, it asked Public Service to submit additional information by Thursday.

The commission's appeal board had ordered a halt to construction of the $2 billion project as of Feb. 4, but the commission had suspended that order pending the outcome of yesterday's four hour hearing. The commission's actions following the hearing reinstated the order, except for the limited work, pending its final decision on Feb. 18.

Attorneys for environmentalist groups argued that Public Service should he required to halt work and be prevented from accepting not already on the site.

A key issue in the conflict is what type of cooling the plant should use - and "open cycle" system that would pump ocean water through, or a "closed cycle" system wmploying cooling towers. Public Service wants to use the "open cycle."

Environmentalists also argued that Public Service failed to examine enough sites to determine if Seabrook is the best.