Nine years ago, the U.S. government told the Bikini islanders it was safe to return to their atoll, once the site of nuclear weapons tests in the Pacific. Some of the islanders went home.

But now the government has found that it was wrong. According to tests last year, the ground water in Bikini is still too radioactive for human consumption. So are coconuts and fruits and vegetables grown in the still-contaminated soil.

So the Interior Department has very quietly asked Congress for $15 million to move the islanders to another location.

"It is now clear," Interior told a House Apprporiations subcommittee last week, "that for the foreseeable future the island of Bikini in the atoll should not be used for agricultural purposes, particularly for local consumption, and should not be considered a residential area."

The approximately 100 Bikinians now living on the island "are being carefully monitored," Interior said. "A feeding program has been provided for them and they are not consuming locally grown food."

Higher than normal concentrations of radioactive elements taken into the human body in food or water over long periods have been associated with the occurrence of leukemia and other cancers.

None of the present Bikini residents, according to Interior officials, appears yet to have become ill from living on the island.

Nonetheless, the Bikini situation will take its place as part of the continuing inside and outside the government on the long-term health effects of low-level radiation.

It has a further significance: the high residual radiation levels in the soil, and its uptake by plants 23 years after exposure, may influence military planners as they explore the prospects of using tactical nuclear weapons in even a limited manner in western Europe.

Interior officials who manage the U.S. Trust Territories in the South Pacific, which includes Bikini, are asking Congress for $6 million in fiscal 1979 to begin a proposed $15 million program to try again to relocate the Bikinians who were moved off their atoll 32 years ago to make way for the nuclear weapons tests.

Some $3 million has been spent on bringing them back to Bikini. The entire island was plowed up, topsoil removed, 50,000 coconut trees planted and 40 homes built.

"All that will be abandoned," Ruth Van Cleve, Interior's director of territorial affairs, said last Monday.

On March 1, 1954, the United States exploded a 15-megaton hydrogen bomb nicknamed Bravo on a spit of coral off Nanu, a tiny island at the northwest corner of Bikini atoll.

The enormous explosion blew a mile-wide hole in the coral reef and sucked radioactive debris up into the mushroom cloud.

Winds carried that fallout over Bikini island, 18 miles southwest of ground zero.

Altogether, 23 nuclear tests were carried out at Bikini atoll, but the 1954 Bravo shot caused almost all the radioactive contamination now on Bikini, according to the Interior's congressional presentation.

In August 1968, President Johnson announced Bikini atoll would be cleaned up, rehabilitated and returned to its original inhabitants who by that time were living on Kili, a tiny island almost 400 miles away.

A year later, the Atomic Energy Commission surveyed Bikini island and, according to published reports, an official said he found radioactivity there "less than Denver, Colo."

"There is virtually no radiation left," the AEC official was quoted as saying, "and we can find no discernible effect on either plant or animal life."

Bikinians in 1970 had approved a rehabilitation plan, and worked started in 1971.

By 1974 some problems had cropped up. The natives wanted to move additional new houses away from the lagoon and into the island interior. A new ground radiological survey in 1975 found the interior portion of the island too radioactive for safe occupancy. It also discovered that breadfruit and pandanas, two food staples of the area grown on trees, contained too much radioactivity.

Coconuts, during the 1975 survey, were found to be safe.

These findings troubled the Bikinians, both those living on the island and the 400 more who wanted to return.

They asked the U.S. government to make a more complete analysis.

In 1977, the government-run Lawrence Livermore Laboratory in California conducted a new study.

It turned up a strontium 90 level in the well water that exceeded U.S. standards.

The radiation level in coconuts was so high that the Bikinians were told they could only eat one a day.Eventually, even coconuts, a mainstay for the natives, were placed on the restricted list.

Early this year, Interior decided the food situation on the island was such that an alternative had to be found.

Since the marine life in Bikini lagoon and the ocean surrounding it has tested safe, Interior is studying whether a new village can be constructed on Enyu, a smaller Bikini atoll island 10 miles away which was outside the 1954 fallout pattern.

Meanwhile, Bikini island, itself, will continue to be a living laboratory for scientists to explore the continuing new problems caused by radiation.