For decades, Social Security has administered the largest retirement program in the world. It has delivered with great efficienty and elan billions of dollars each month to tens of millions of Americans.

Several years ago Congress decreed that Social Security also should get into the welfare business. In 1974 the agency began administering a Supplemental Security Income program. Immediately, it became embroiled in problems and controversy. Its offices were besieged with a new class of claimants. Its record of efficiency was shattered. Its morale deteriorated.

Two months ago a new administration came to power. In the process of its first attempt to reorganize the government - an effort to bring order out of disorder, to streamline the workings of the bureaucracy - Social Security was directly affected. The agency was given administrative oversight for still another segment of the huge welfare population - some 11 million parents and children receiving billions of dollars each year under the Aid to Families with Dependent Children program.

The news was a shock.

"This just says to us we're heading more and more into the welfare business," one employee said. "And that's not what we need."

Another was more explosive. "Christ, another program. Who needs it? Does anybody understand what's happening to us? The President doesn't understand? OMB (the Office of Management and Budget) doesn't understand.Hell, we've had it with reorganizations - illogical reorganizations that we don't understand, yet we're supposed to explain them to our people and make them understand and accept it."

Not everyone in Social Security reacted negatively. Some see it as a challenge that the agency will master. But the move reinforces a point that keeps being hammered home during these last months of exploring the world of government through the limited perspective of one of its agencies. As someone along the way remarked, "The system is corrupting itself."

He didn't mean corruption in the simple sense we write about in the newspapers - theft, bribery, fraud, greed.He meant government is growing out of control, all right, but not because of any single factor. It has become a victim of forces that inexorably propel it into greater and greater endeavors, creating greater and greater problems. "The whole society is involved in a rip-off, if you want to put it that way," he said.

The experience of Social Security would seem to bear that out. "We've been considerably frustrated at all levels," one of its managers says, "as public expectations about our role are continually being raised and we're continually being asked to perform tasks that we think we're not equipment to perform."

That doesn't take into account the reasons for the current reorganization, of which Social Security was only a part, nor the complexities in carrying it out.

The reasons are simple enough - the desire of new managers in a new administration to see if they can make the government work better. That was the pledge from Jimmy Carter on down. And the difficulties are clear enough, too - can anyone really make a difference?

The target, in this case, was not Social Security but the sprawling department that reaches into every corner of our lives. Social Security happens to be only one of that department's many tentacles.

As a symbol of the government, and the bureaucracy, the Department of Health, Education and Welfare stands alone.

"No enterprise that I know of, government or otherwise, has ever grown as fast and reached out into so many areas," says a bureaucrat who has watched HEW change from within since the 1950s. "That may be a reflection of something else, of what's happening in society generally.

"Life in America, and life in the Western world, has pust become very complex. The dynamics of change are very rapid, perhaps even overwhelming. HEW's a reflection of that. HEW today is now self-propelling. It has a motion and thrust all its own. You can change the leadership and the tempo will pick up. Its effort may pick up or decline, depending on the quality of its people, but there's a certain amount of activity that's inevitable now. It just propels itself along. That's true of the whole government, though.

"Look at the uncontrollability of the federal budget. Look at the Congress. The Congress is continually looking for new space. Its appetite for new offices is insatiable."

As Social Security Commissioner Bruce Cardwell pointed out in an article in Monday's Post, another change is affecting American society. It's changing attitudes about work itself, found in every coerner and segment of society today, in or out of government.

In that same period of HEW's growth, as more and more demands were placed on it with more and more bureaus created to oversee more and more programs, the obvious occurred. Morale declined, errors increased, service to the public suffered.

"I don't know how to get the bureaucracy back to where I used to recognize it, particularly in these big departments," says an HEW official.

"My general impression over the 25 years and various agencies I've been in is that the bureaucracy has gotten slower. They have reacted to what's happening in government by going into their holes. They're digging in hunkering down."

He has only one solution: "Unless you get cues down through the bureaucracy. And you've got to move fast."

That is what happened to HEW - and Social Security - in these early days of the Carter administration. How it was accomplished, and under what circumstances, tells a great deal about government today. And it raises as many questions as it answers.

When Joseph A. Califano Jr. took over as HEW Secretary two months ago he found many changes from the government he had known during his days in the Pentagon and the White House in the 1960s. The power of Congress had increased greatly, and the congressional staffs were vastly more influential. Government regulations had become unbelievably complex, and programs more intertwined and unmanageable. The bureaucracy was both dispirited and distrustful. And it was much more difficult to exercise authority. In his department along Congress had enacted thousands, of things that an HEW Secretary couldn't change. The only way to get change was through legislation. That meant asking Congress' permission. You were a pawn, a hostage, which ever way you moved.

Calfano was determined to move swiftly in carrying out the President's - and his own - public pledges to reorganize his department. He was confident, too, that by realigning and eliminating overlapping functions, better administration could be achieved at far less cost.

He had another concern: any attempt to change HEW's structure would have to be done under tightest secrecy.

It hadn't taken him long to learn that virtually everything he did leaked instantaneously from the bureaucracy to congressional sources, special-interest groups and the press.

"I have come to the conclusion that everything I sign is a public document within 24 hours of the time I sign it," he says. "The only things that may not be public documents that fast are the memoranda I send to the President, because we hold them so tightly here. But everything else - excerpts from letters I've written, memos out of my office - I have to assume will leak."

Califano wanted to make certain his plans for HEW were secure. As someone who worked with him on the project put it: "To be brutally frank, if you let it seep out of you you'll never get it done." He meant that various interest groups could combine with their respective allies on the Hill to throttle it.

The security surrounding Califano's reorganization move is a measure of how difficult it can be to change government today. There was 145,000 employees in HEW. Aside from Califano, only five persons in all of HEW knew what was being contemplated. They were pledged to tightest secrecy.

After extensive private meetings the reorganization plan was finally put together. Califano faced another problem. He had to have briefing papers and charts ready before presenting the idea to the President.

"I had no sense I could get copies of briefing papers, plus all those put together over here at HEW without having it leak all over hell," he recalls.

He went to Harold Brown, the new Secretary of Defense, whom he had known in his own Pentagon period. Brown agreed to have the charts and papers prepared at the Pentagon.

On March 2 Califano briefed the President at the White House. For more than an hour he went through the details before an audience composed of Carter, Vice President Mondale, OMB Director Bert Lance and presidential aides Jack Watson, Stuart Eizenstat and Harrison Welford.

The President was pleased, the plan was approved. Five days later Califano briefed the Cabinet and then announced the reorganization to the public as "the most far-reaching in the department's 24-year histroy."

Califano's first thoughts about his reorganization centered strongly on the Social Security Administration. He was thinking of moving two critical and controversial welfare programs - Medicaid and AFDC - into Social Security. The agency already had been given a federally subsidized welfare program for the nation's aged, disabled and blind (SSI). It also was administering Medicare.

One of his advisers objected: "I told him at that meeting, 'Hey, boss, you're putting 97 per cent of your money under the guy,'" he recalled. "'Do you really want to do that? When you do that's you're creating a super-super agency head.'"

In the end, Medicare was transferred from Social Security as part of the formation of a new health-care administration. Social Security administratively was given AFDC to go along with its other welfare benefits programs, SSI. That put HEW's cash-assistance programs under a single administrator, just as health-care functions were being placed together under a separate unit. It would eliminate fragmentation, Califano reasoned. It was logical. It should simplify management functions and save as much as $2 billion in the next two years.

It was also believed that putting the two programs under Social Security would lead to substantial reductions in error rates of SSI and AFDC. Social Security alone had been working intensively to cut errors, with marked success: rates in SSI have been cut at least in half. The cost had been high - a billion dollars in incorrect payments in its first two-year period - but about a third of that money has been recovered or settled. Still, error rates in both programs remained high. Latest figures for SSI show an 8 per cent payment error. FOr AFDC it's a 9.1 per cent rate.

The long-term impact of AFDC on Social Security is unclear, in part because the entire question of welfare reform is being studied within HEW. State and local governments still pass out their AFDC welfare payments in offices across the country. But Social Security now is assuming overall quality control as well as seeing that federal guidelines are carried out. If fraud exists, it's the ultimate responsibility of the federal government to root it out.

Probably the greatest concern within Social Security is that the AFDC program - with 11 million beneficiaries getting $9 billion a year - ultimately could turn into another SSI experience.

Califano and his top advisers had discussed the impact of these moves on Social Security.They had weighed morale and other factors. They were aware, as one said, that people there "generally felt the SSI experience was more than they ever wanted to fare again."

Califano says, "I guess I was not as aware of the problems with SSI." He had visited the agency's headquarters in Baltimore and come away with several strong impressions.

"My instinctive reaction was how incredibly big it is," he says, "with those 300 or more million people on those computer tapes, and how incredibly dreary some of that work must be for the individuals. I felt sorry for the people that were reading those micro-films.

"I've done my share of legal research, reading old documents on microfilm, and it's grim, tough. It sears your eyes. But I was impressed, I guess, that they've come a long way from a few years ago. Then you couldn't have a radio when you were sitting there. They've got much more frequent breaks now. They've learned that that pays off."

What has not been learned, it seems clear, is something more fundamental. Perhaps the HEW reorganization will turn out to be the model for the rest of government. Perhaps it will save billions of dollars, although that is doubtful. Perhaps it is a hopeful beginning, for Carter, Califano - and the country."

This reorganization does not touch, however, nor was it intended to, some of the deeper problems of government. It does not address questions of pressures from the top building on the workers below, on outside demands for more and more programs and more and more laws and more and more regulations, on complexities of declining morale and technological tangles.

It certainly does not address the personal frustrations felt by many people on the front line of government today.

"We're being asked to deal with things that a bureaucrat isn't really trained to do," says a government employee. "Look at the SSI program, for instance. [The federal welfare program for the aged, the blind and the disabled is now run by Social Security]. In California a federal bureaucrat out in a district office has to go and see if your aunt changed living arrangements from to month to determine if she stays on welfare or if her SSI benefits go up or down.We have to go in and ask her if her cooking arrangements are different from last month to next month. No way!"

"If we don't and we find out by our quality control that her cooking arrangements have changed and she should get less money, that's an error. I don't think anybody understands the complexity of that, I don't think anybody understands that the federal bureaucrats can't do that without errors. We'll never get those errors down, I think, below 15 per cent. That's almost an impossible situation."

Too often, employees react all too similarly. They do just enough to get by. "You don't get your psychic income out of the office," one says. "You do the best you can, and try not to get too frustrated. You get it out."

As we have been reporting these past three days, Social Security is an agency with a great record of public servive presently experiencing considerable strains. Some of its wounds are self-inflicted. Most are not. What makes it so signal a case is the irony of its dilemmas. One stands out sharpest of all. Social Security has become a victim of its own achievements.

"It's the rewards for success," says an HEW official who participated in shaping the current reorganization plans. "Every one of those programs that was given to Social Security was given not because it made so much logical sense to put them in there. In many cases it didn't. They were put there because of the fact that here was an organization that had a reputation of being able to get things done.

"Generally speaking, there was no problem you couldn't give Social Security. They brought medicare up from nothing to on board in a period of 18 months after the law was passed. That was an unbelievable administration task. I don't know of any other example of a new program getting off the ground like that. And when SSI was given to them, wasn't the decision based upon the fact that they could do it? That was the only place that could do it?"

Of course Social Security workers say that, precisely, was part of the problem. They speak about reaching - or overreaching - the saturation point in terms of programs, services and benefits. They speak of programs eventually turning inward and becoming self-destructive. They speak of struggling to simplify legislative flats affecting those programs. "I don't think Congress is interested in simplification," one person says wearily, "because the law is so filled with provisions that protect somebody. I really don't think anybody is interested."

From the top echelons at HEW the perspective differs. The most critical problem Social Security faces, you'll hear, lies with its computer systems technology. "My assessment of the problem of morale and the image of Social Security going downhill over the last five or six years," that same official says, "is that 90 per cent of it is tied to systems problems. And I don't think they recognize that, I think they blame it on overwork. But the overwork is because they haven't been able to get the systems to respond in time to do the work. So people end up having to do it."

Again, the irony: Social Security officials say so much of their time is spent on technology - on worrying more about machines than people - that its proudest traditions are in danger. It was Social Security's greatest source of pride to be thought of as the people's friend, the agency closest to the people's friend, the agency closest to the citizen. For a number of the reasons we've been suggesting, that public and personal role grows more difficult.

One more observation. In all the public talk about the excesses of government, a great deal of time and attention are spent on fraud and scandal in administering programs. Politicians seize on that. They pledge to remove welfare cheaters and reduce cost overruns. Fine enough. What doesn't receive as much attention is perhaps the greater corruption - the attempt to do more than is prudent or possible and the failure to account for the real costs of placing greater burdens on government.

This is a story without an end.

No final clarion message emerges from this glimpse into government. In months to come, other agencies and organizations will be examined. Perhaps other lessons will be learned. But Social Security alone provides disturbing evidence of government gone awry. And the words of one of its managers are worth pondering.

"My own personal conviction," says Robert Bynum, associate commissioner for program operations, "is that the President and Congress ought to be very, very careful about enacting new programs to take care of what is apparent as a need without very, very thoroughly and carefully looking at everything else that's already on the books that somebody else has responsibility for. And somehow in that process they must insist that you undo some things that have been done.

"If we don't do that, if this President and this Congress don't somehow get a grasp on how to do that over the next four years, then we are truly going to reach a chaotic kind of situation in this country."