Since 1996, the utility has hired new executives and taken steps that it says would prevent violations in the future. Federal prosecutors, while describing the old offenses in harsh terms, said in today's proceedings that they had confidence in the new managers.

After the large number of Millstone candidates flunked their licensing tests, investigators discovered that they had not put in the required number of training hours nor mastered the maneuvers that Millstone had falsely claimed, the Government charged. Some of the candidates have since been retrained and are now on the job, the company said.

Federal prosecutors said economic pressure brought on by deregulation of the nuclear industry had contributed to the violations. ''Rather than treat the problem,'' said Joseph C. Hutchison, an assistant United States Attorney, ''the shortcut was taken so there was some economic saving.''

Mr. Hutchison said complaints by community groups and workers at the plants had led to the three-year Federal investigation.

Stephen C. Robinson, the United States Attorney for Connecticut, said of the agreement, ''No matter who you are, no matter how big or how powerful, if you endanger our citizens, if you violate the law, if you lie to regulators and choose profits over the public, we will come after you.''

Michael G. Morris, the chairman and and chief executive of Northeast Utilities, the parent of Northeast Nuclear, did not dispute a statement that the violations were deliberate, but said the public had never been in danger. As he left the courthouse today, Mr. Morris attributed the violations to ''inattention to detail'' and ''inadvertence,'' not deregulation. ''The whole notion that you react differently in a competitive marketplace is true, but it doesn't cause this kind of behavior,'' he said. He said the lesson for plant owners was ''it's better to operate within all of the laws and the requirements because these kind of fines, these kinds of embarrassments, will come your way if you don't.''

Mr. Morris was hired in 1997, after the offenses took place. Nevertheless, Judge Robert N. Chatigny called him to the front of the court this morning and told him sternly he hoped the plea reflected a commitment by the company ''to be a better citizen in the future than it was in the past.''