In "NRC Cracks Down on Criticism" {Sept. 29}, Jack Anderson and Joseph Spear have inadvertently left a false impression about the manner in which the Nuclear Regulatory Commission deals with employees who hold professional opinions that differ from those of their supervisors. Years ago the commission recognized that safe operation of nuclear power plants would require assurance that any staff scientist or engineer could have direct access to the commissioners, without fear of reprisal, about any issue of importance to the agency's mission. Since that time NRC employees have periodically been encouraged by management, in writing, to discuss their concerns with the commissioners and other high-level managers through either an informal open-door policy or a formal procedure specified in Chapter 4125 of the NRC Manual.

This system works. Several years ago I held a differing professional opinion and was allowed to address the full commission in a meeting open to the public. There was no reprisal; in fact, I was commended by my superiors for this action at my next performance appraisal.

I have no firsthand knowledge of the problems discussed in the Anderson-Spear column and cannot speak to the accuracy of the events as reported. But I can imagine that many thoughtful readers would be concerned about a federal agency -- charged with the responsibility of regulating nuclear electric power -- that stifled technical dissenters on its staff. There may be rare and isolated instances of suppression that I have no knowledge of. However, encouraging differing professional opinions is the rule of the day at the NRC.

ROBERT E. ALEXANDER Chief, Radiation Protection & Health Effects Branch Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington