WHEN THE old Atomic Energy Commission was broken up and the Nuclear Regulatory Commission created, one of the purposes was to reassure the public on the question of nuclear safety. The AEC had been both a promoter and supposedly impartial regulator of nuclear power, but those functions clashed. An independent regulator, it was thought, would not be burdened by the same divided loyalties.

Now, however, the NRC has taken a step calculated to erode the very public confidence it was set up to enhance. The agency has moved to exempt itself in large measure from the Sunshine Act, meant to force federal agencies to conduct public business -- you guessed it -- in public and not in private meetings behind closed doors. The act allows the private discussion of certain matters, usually in personnel matters or those involved in litigation, but formal records must be kept even of these meetings.

To escape this stricture, the five-member NRC has created a new kind of meeting -- or non-meeting -- called a "gathering." At gatherings, commissioners can discuss commission business in private and without the keeping of a transcript. The idea is to free the commissioners from the inhibitions they would otherwise feel when discussing issues that are at the same time highly controversial and very technical.

When the commission proposed this relief for itself some months ago, there were protests, not least from some overseers on the Hill. Such members of Congress as Edward Markey, often a critic, urged the commissioners to reconsider.

They now say they will defer a decision pending an American Bar Association review of the Sunshine Act.

The commissioners' desire to be able to discuss issues in private is very human and understandable. If they weren't conducting vital public business, we would sympathize with them. But public office carries a burden: openness to public scrutiny. If the members of the NRC want to stay in office, they should take this time to reconsider and obey the Sunshine Act. If they won't, Congress should make them.