At a recent hearing with survivors of the Hiroshima bombing, Sen. Paul E. Tsongas (D-Mass.) gave it as his opinion that Mr. T.K. Jones "ought to be committed" and invited witnesses to comment.

One of the frail Japanese women before him said timidly, "Excuse me, senator, I do not know who is this Mr. T.K. Jones."

As a matter of fact, the senators had difficulty finding out who he is, since Mr. T.K. Jones had stubbornly declined their several invitations to come and explain certain cavalier observations about nuclear survivability he had delivered in interviews and in frequent appearances around the country.

It took the threat of a subpoena to bring T.K. Jones into a crowded hearing room yesterday before a Foreign Relations subcommittee chaired by Larry Pressler (R-S.D.). His testimony only disclosed that there are two T.K. Joneses, one of whom bears absolutely no resemblance to the person who told the Los Angeles Times that surviving a nuclear war was really a piece of cake. "Just dig a hole, cover it with a couple of doors and then throw three feet of dirt on top," he said.

The T.K. Jones of the belated hearing does not talk in such earthy terms. Here's his cleaned-up Capitol Hill lingo: "Soviet civil defenses are but one element of a synergistic multilayered protective posture."

The Pentagon has booked Mr. Jones far and wide and arranged for him to utter his indiscretions to reporters. In his official capacity as deputy undersecretary of defense for strategic and theater nuclear forces he has been giving the upbeat view that the United States could recover from all-out nuclear attack in four or five years. He may have played well in Peoria, but the Defense Department discovered early that on Capitol Hill, T.K. Jones is highly radioactive.

Only after Sen. Charles H. Percy (R-Ill.), mild chairman of the Foreign Relations Committee, announced his intention to send the sergeant at arms to round up Jones did the Pentagon deliver Jones in person.

They sent with him about 30 aides and handlers and again tried to run in Richard N. Perle, assistant secretary of defense for international security policy, as a substitute, a ploy that failed in recent weeks. Perle, inventor of the term "Protestant angst" to explain Europe's otherwise unaccountable objection to nuclear incineration, was incensed when the senators refused to let him speak first.

"I protest. I want the record to show . . . I had an agreement with the chairman," he sputtered, but Pressler stood firm. The subcommittee wanted to hear T.K. Jones.

He was scarcely audible. Jones looks like your uncle who ran away to sea and came home with tales beyond verification. He has wavy gray hair and a kind of duckbill mouth and was at great pains to prove, although he is retained as a technician of vast capacity, that he really doesn't know much about anything, except the Soviet civil defense program. Mary McGrory FINALLY -----

To tell the truth, he doesn't know a great deal about that. When asked by Tsongas how the Soviets, who cannot feed their people in ordinary times, could feed them in the event of a nuclear war and a massive evacuation, Jones wandered off into an arcane reference to 1976, tried to pass the question to one of his protectors, a general, and then limped to the conclusion that the Soviets "wouldn't starve themselves."

U.S. civil defense planning, he said chastely, is the concern of the Federal Emergency Management Agency. But he said he believes in the program because the wicked Soviets, who believe that a nuclear war is winnable, will be deterred by our preparations.

U.S. civil defense plans have for the most part set off more tremors at home than in the Kremlin. Upon hearing that they are to leave their cities, armed with lunches, shovels, credit cards and the promise of free change-of-address cards from the post office, many Americans have reacted like the Duke of Wellington to the sight of his troops: "I do not know if they frighten the enemy, but by God, sir, they frighten me."

Under the pleading prodding of Percy, who was hastily sent for as a peacemaker, Jones disavowed his statement about rapid recovery from nuclear attack and said he never said it.

Perle was finally allowed to read his statement, a masterly piece of condescension, in which he said he knew "that this subcommittee would never deliberately propagate confusion or misunderstanding in the public record."

And besides, he said grandly, Jones' statements were "his own and not necessarily those of the Department of Defense."

If Jones talked out of turn, shouldn't he have been fired? The answer is that he didn't. Not everyone in the administration talks that way, but they think that way. Else why is T.K. Jones still at the Pentagon and available to Capitol Hill only under a threat to send the cops? You think they'd be that nice to some official who came out, during office hours, for the nuclear freeze?