The Department of Energy is preparing to announce a massive government-financed study of the long-term health effects of low-level radiation just as a White House task force is about to criticize the department and its predecessors for failure to investigate the problem.

One government official familiar with the study said DOE was moving "precipitously" to blunt the criticism and was ignoring suggestions to DOE officials that the contract for the study be delayed until after the task force report.

Among the alternatives being proposed by the task force, sources said, is transfer of radiation health studies from DOE on the grounds that the department seems to have a conflict of interest in undertaking such work.

The DOE study will be run by the Johns Hopkins School of Hygiene and Public Health. It will focus on 250,000 current and former workers who built and repaired nuclear submarines and ships at seven yards.

Some of the shipyard construction goes back more than 20 years.

The study is initially planned to take at least five years. Funding for the first year will be $1.5 million, with the remaining four years expected to cost $2 million each.

It will take from three to five years, sources said, just to get the individuals, their radiation doses and medical records into computers.

DOE officials said yesterday they were aware the White House task force was planning to suggest research programs be run by another agency but decided to go ahead with this study "because we felt it should not be delayed."

"We need this information for ourselves," one DOE aide said yesterday.

A government official who is a DOE critic in this matter called the impending contract award "terrible," adding, "It's part of the bureaucratic warfare."

The new program is a direct outgrowth of a private study done last year by a Massachusetts doctor with the assistance of The Boston Globe. It found increased cancer deaths among former workers at the Portsmouth, N.H., Navy shipyard -- a finding that was criticized by Adm. H. G. Rickover, head of the Navy nuclear program.

The only comparable major low-level radiation studies DOE financed in the past were of its own workers at the Hanford nuclear facility in Washington state and the Oak Ridge National Laboratory in Tennessee.

Some 130,000 employes were covered in those reviews.

The hanford inquiry has been the subject of major controversy. The original contractor, Dr. David Mancuso of the University of Pittsburgh, was replaced last year after running the study for over 10 years.

Mancuso claimed he was fired because his study was beginning to show that an increased risk of cancer occurred at lower dosages.

His DOE employers claimed the contract was concluded because Mancuso had shown no results at all.

The Mancuso controversy was only one of several recent events to raise questions about the health effects of low-level radiation. Eight servicemen who participated in the 1957 Nevada nuclear test called Smoky have turned up with leukemia -- more than twice what government scientists now say should have been expected.

Additional cases of leukemia have developed among inhabitants of towns in Utah downwind from the Nevada test sites -- towns that on occasion received radiation from fallout created by the atmospheric explosions.

Public and congressional concern last year caused President Carter to establish a task force to look into the low-level radiation question.

Although scientists have shown high doses of radiation cause leukemia and other cancer, there is sharp disagreement as to whether the same effect occurs at lower radiation levels.

Until the past few years, most government scientists agreed that there was little risk of increased cancer among individuals exposed to lower doses.

The White House-appointed task force, directed by Department of Health, Education and Welfare general counsel Peter F. Libassi and composed of all agencies involved with nuclear matters, has been reviewing the government and private research programs to determine what more is needed to clear up questions that have emerged.

Because of continuing disagreements within the group, the task force report has been delayed several times and now is promised next week.

One of their findings, however, relates to the appearance of conflict of interest that goes with the Department of Energy doing health studies.

On the one hand, according to task force sources, DOE is in business to develop nuclear material for weapons and energy uses; on the other it is studying whether low-level radiation had any adverse health effects.

One DOE official, defending his agency's decision to go ahead, said there was no guarantee that the White House and the Congress would go along with any new organization setup.