The accident at the Three Mile Island nuclear power plant will hasten an intended lowering of the government's permissible radiation exposure level for most workers in the atomic industry, according to administration sources.

The controversial change will be the subject of Environmental Protection Agency hearings this summer and may be proposed as regulations by the end of the year, sources said.

Another EPA rule, to cut substantially radiation emitted from nuclear plants outside the plant boundaries, is already scheduled to go into effect Dec. 1.

Under this rule, facilities will be allowed to emit just 25 millirems a year, down from 500 millirems per year, which has been the standard since 1960.

The Three Mile Island plant operated by Metropolitan Edison Co. released 17 millirems in the three months before last week's accident. According to a company official, one off site monitoring device recorded at least 100 millirems during two days of the accident period near Harrisburg, Pa.

A White House task force is expected to propose a reorganization of federal management of nuclear radiation matters.

Under a draft plan circulating in the administration, the Department of Health, Education and Welfare will chair an interagency committee that will supervise all radiation health research programs. At present, almost 70 percent of such research is funded and directed by the Department of Energy, which is also charged with promoting nuclear weapons and power programs.

In addition, the EPA will be proposed to head another interagency group charged with coordinating nuclear radition-associated regulations. Currently, the Nuclear Regulatory Commission, Food and Drug Administration and to some extent DOE and EPA make regulations in this area.

Underlying the changes in radiation standards, the first in 20 years, is the controversy over the long-term health effects of low levels of radiation.

When the current standards were set, most scientists believed there was an almost risk-free level of radiation.

Recent health studies, however, have cast doubt on that belief. The new studies, which show increased leukemia and other cancers in exposed groups have been heavily criticized inside and outside the government. Nonetheless, they have moved the government's health and nuclear regulatory bodies to reassess the situation and make changes.

Furthermore, a new report is expected shortly from the National Academy of Sciences committee on biological effects of ionizing sadiation.

Its chairman, Dr. Edward P. Radford of the University of Pittsburgh, has stated he believes the occupational radiation standard should be cut tentold.

Since 1960, federal standards have allowed workers at nuclear plants to be exposed to 5,000 millirems per year and 3,000 millirems in a single quarter. In exceptional circumstances 12,000 millirems in a year were allowed.

A reexamination has led to a new conclusion that 5,000 millirems per year for an unlimited time represented "a pretty substantial risk," according to one EPA official. CAPTION: Picture, Lester Desenberg delivers milk as usual on his rounds at Goldsboro, Pa., near the Three Mile Island A-plant. AP