Top-level personnel jobs, traditionally reserved for career bureaucrats with a vested interest in the system, will be opened up to noncareer and short-term political appointees in many agencies.

A number of departments already have decided to exclude the post of personnel director (or equivalent) from the list of jobs reserved for career civil servants.The change is part of the new Senior Executive Service that gets rolling this summer.

The switch will make it possible for agencies to hire more outsiders for the key people-management jobs. It has upset many in the career personnel community, both for personal advancement reasons and out of fear that the civil service system in agencies may be compromised.

Under SES, thousands of Grade 16 to 18 jobs-pay $44,756 to $47,500-gradually will be integrated into the new system. It promises higher pay benefits and promotions as a trade-off for less job security.

Incumbents tapped for the SES may refuse to join. But new people hired for many key "supergrade" slots will have to join the SES. It will have an overall ratio of about 90 career people for every 10 noncareer appointees. Carter administration officials hope the clout of that 10 percent, and greater management powers in the SES, will make it possible for the 10 percent to steer the bureaucracy in the direction the White House wants it steered.

Agencies have authority to reserve a limited number of jobs for career people. But many are expected to follow the lead of the Office of Personnel Management. It has removed its top internal personnel job from the career reserve list, meaning that an outstanding executive from industry-or Billy Carter or Don Nixon if deemed qualified-can have the slot.

Backers of the "new blood" system believe it will give more flexibility to people assigned by the president to run agencies. It will permit them to clearly establish top personnel operations in the management team, as in industry. Some personnel directors in the past have, rightly or wrongly, used their civil service status and staying power to block actions planned by political appointees to end-run the entrenched bureaucratic system.

Those against putting noncareer people into top personnel jobs fear it will turn the shops-not now the perfect defenders of little guy rights into absolute rubber stamp operations for short-haul politicians with big ideas.

Career workers will still be able to take top personnel jobs with status. But the fear is that many agency heads will choose to have their own in those jobs, cutting down promotion potentials for career bureaucrats in the personnel field.