All television soap operas thrive on family discord, quietly revel in mental anguish, and efficiently and unashamedly offer their discarded performers tragic departures worthy of opera of a grander sort. All do, that is, except for one.

The exception to that time-tested, unwritten rule is the recently-introduced "Lovers and Friends," now undoubtedly the only show of its kind in which no one has been killed in an accident or died of natural causes, whether prolonged or sudden. That, however, doesn't mean the cast hasn't already died a thousand deaths.

"When my time was up on 'Another World,' I died," sighed Nancy Marchand, who is perhaps best known for her role as the aristocratic Mrs. Lassiter on the ill-fated series, "Beacon Hill." "Oh, I had to die, you see. I had heart failure sitting in a wheel chair on a terrace signing 'Bye Bye Blackbird.'"

While she was going from "Another World" to another world, Stephen Joyce was experiencing less tranquil transitions. More recently he was uncremoniously blown out of the "Search for Tomorrow" script by a Mafia bomb planted in his car. Earlier, he was mugged brutally during a walk through a park on the set of "Where The Heart Is."

"That last one was messy," he says now during his latest reincarnation as George Kimball, the labor lawyer married to Eleanor> one of two daughters of Lester Saxton, an alcholic managing a warehouse for an electronics firm, who has moved with his wife and four other grown children to a wealthy suburb of Chicago where their next door neighbors are the wealthy Cushings who . . .

"I lingered five days in a coma with all sorts of tubes in me and people crying over my hospital bed. It was a horrible way to die, of course."

Of course. And, just as of course, no one associated with this fledging effort has any thoughts of letting death overtake either members of the cast or the show itself. This, they all hope, is one soap opera - or continuing daytime serial -d that will live a long and heart-rending life. But for whom?

Well, according to surveys, millions of people are addicted to the televised melodramas. In fact, "Lovers and Friends" notwithstanding, there are a total of 13 other "legitimate soaps" currently enjoying runs on the three major networks. Fourteen shows, all fighting for the attention of those housewives out there, those house-husbands out there, the unemployed, the night workers, the infirm, the ones who watch television while at work and the ones who tape it for viewing when the come home.

That fight takes money (no one at NBC will say how much), time (plenty) and talent. Not surprisingly the talert is high caliber. After all, the pay is excellent, the work is steadier than just about anything in show business excluding a Broadway hit, and the challenge stands by itself.

And so, every weekday, the actors and the crew gather at 7 a.m. in a huge warehouse of a studio center somewhere off Videoland's Main Street in Brooklyn. Their eyes are often bloodshot (several perform in plays until the late evening) and their hands cling to steaming containers of hot coffee as if to life itself. And, at that hour of the morning, perhaps they are.

The eight-hour day is long, dotted and dashed with rehearsals, costume changes, visits to the hairdresser and make-up, more rehearsals, directorial critiques, script alternations and one "live" taping. But it is worth it, they say; especially because it is a new program.

"I love the idea of being in from the very beginning," says Rod Arrants who plays Austin Cushing, a heavy-drinking guitar-strumming, disillusioned landscape painter. "It's a lovely sensation. I love it much better than either joining a show in progress as a new character or as a replacement for someone else who has been doing it a long time.

"I think that's harder on the new actor and very hard on the ensemble which has lived with a whole series of expectations. Now you're a foot taller, and you don't sound the same, and you don't have the same impulses. But starting fresh with everyone in the same boat is very exciting."

LIke his colleagues, Arrants, who is 32 and bears a striking resemblance to actor Richard Chamberlain, is not the soap opera automaton some critics suggest - a bit actor whose only half-way sensible thoughts roll slowly before him on the yellow sheets of the nearest TelePrompter.

Instead, he approaches his role analytically and with obvious thought. "I finally got used to the idea that there was a way to play Austin and to make him human and sympathetic," says Arrants, who was "run out of town on a rail" as a nasty character on "The Young and the Restless" serial and whose non-soap acting credits are impressive.

"Inside the character, I think there's failed purpose. I saw Richard Burton interviewed a couple of weeks ago and his favorite character is the kind who has lost his center but not his integrity. He still has an ethical sense and a caring. He's got a hole where he lives, and he's trying to fill it with liquor."

The same elements that make his fellow actors and actresses more than superficial also provide them with differing perspectives.

"I think you're taking a lot more chances coming onto a new show," Nancy Marchand tells you as she adjusts the black, fur-collared suit she has just picked up from the wardrobe department. "When you study and work on your part, you are responsible for setting up some kind of interest whereas if you come into something that's already established, you are told what you are there for and it's all written for you around you. You sort of have to fit into a mold. Here, we're trying to make a mold. You have to say 'I hope this is going to work.'"

This is John Heffernan's first soap opera role. By night, the 42-year-old actor exudes physical as well as theatrical energy as a featured member of the cast of Broadway's "Sly Fox" starring George C. Scott. Because that job devours evenings Tuesdays through Sundays, he is locked into a sevenday-and-night week.

"If I had one job like any sane person, it would be all right," he concedes with a weariness that clearly transcends his "Lovers and Friends" role. "In that case, I would find this very, very pleasurable. Right now it is an effort.

"Since this happens to be my first soap, my basis of comparison with others is limited, through I imagine our scripts are as thick with portent as they are precisely because it is a new show. We have to keep repeating over and over again people's names. I'm telling my wife what our own children's names are. It doesn't make for the most exciting kind of theatrics. Once the plots get thicker and there are more and more characters and we start spinning off one another, it will be more exciting."

While he's waiting for the excitement Heffernan - who betrays an impishly dry sense of humor - has already informed his soap family that he can't drive a car. "That way," he says with a ruler-straight face, "I can't drive off a cliff. They still may give me a terminal illness, I suppose, but we have to be optimistic about these things."

Flora Plumb, who portrays 27-year-old Eleanor (nee Saxton) Kimball, views the effort in much the same light. "The pressure is at its worst doing soap," she says, making a comparison with her guest appearances on a wide variety of nighttime television series. "It's much harder than any other kind of acting. Of course, it's worth it. It's a wonderful experience."

Ron Randall, who manages to mask his "Bermudian-British accent" in the important role of Richard Cushing, is perhaps the most recognizable of the show's male actors with a career ranging from London to Hollywood. This, however, is his first soap, too.

"The trauman I went through at the beginning wasn't so much getting the lines down as getting up in the morning," he recalls with a laugh after pausing to toy with the prop department's gold wedding band he wears on his left hand. "I rehearsed for about three or four days getting up at five. My neighbors didn't appreciate it at all, my banging around the flat."

"You always hear people kick the floor and nod their heads and say 'aw, geez, I'm doing a soap. What can I tell you?" Richard Backus tells you. "I don't really feel that anymore. Now that I'm doing one, I know that the energy and the craft that goes into it is really stupendous."

That energy and craft imposes on the cast the daily need to cope with what's new - new lines, new plot twists.

The new lines are being provided by Emmy award-winning soap writer Harding Lemay. He won the award in 1975 for "Another World," and also wrote for the ill-fated "How to Survive a Marriage."

The responsibility for coordinating all that newness rests across the hall from the studio in the office of executive producer Paul Rauch. This is no greenhorn. This man has been around. Before taking on his duties for "Lovers and Friends" and earlier "Another World" he was - among other things - vice president for East Coast programming for CBS.

"Soap operas have changed," he says with low-key intensity. "It's a more responsible medium than it was in the past. Back in the early '30s, there was even a serial in which a woman was kidnapped by a gorilla. That idea was probably stolen from 'King Kong.'

"Today, things are different. I work very closely with the writer to try to make sure we present the best possible show to the public. That creative part is the hardest aspect. It's not easy to expose and delineate character. The start of a new show is difficult because it's difficult to be expository and yet show movement . . . if we want this one to be a success, it's important to pull back, watch the show on the air and see how it comes back at you."

Right now, everything seems to be coming back nicely. The plots and sub-plots are falling into place, the actors are adjusting to their roles and their hours, and (as yet) no one is terminally ill or faced with a fatal accident.

It's enough to make a soap opera lover cry.