This is one in a series of articles on President Reagan's fiscal 1986 budget proposals.

President Reagan has requested $12.5 billion for the Energy Department in fiscal 1986, a slight increase over 1985 that would shift more than half a billion dollars out of civilian programs and into nuclear weapons production.

Spending for weapons research and production would go up about $584 million. Funding for programs to handle nuclear waste, both civilian and military, also would be increased. In total, funds for DOE programs oriented toward the military would increase by $700 million, roughly 10 percent.

The increase would be balanced with cutbacks in virtually all of DOE's other programs, from research to conservation.

While the research and development budget would remain relatively stable at $5.1 billion, the president has proposed to cut research funds for general science and energy conservation, as well as research aimed at nuclear, fossil, solar and renewable energy sources.

Those cuts would be balanced with increases in funding for weapons research, naval reactors and defense-oriented nuclear energy.

Although most agencies have proposed to pare their administrative expenses, in keeping with Reagan's goal of achieving a 10 percent across-the-board cut in such costs, the president requested an increase of nearly 20 percent in administrative expenses at DOE.

Under the president's proposal, DOE's largest contribution to deficit reduction would be a moratorium on filling the Strategic Petroleum Reserve, which was established a decade ago to reduce U.S. vulnerability to disruptions in the oil supply.

The $2 billion annual expense for filling the reserve is an off-budget item. Reagan has proposed to make it an on-budget item in 1986 and then not fund it. The reserve is expected to contain 489 million barrels at the end of fiscal 1985, about 260 million barrels short of the goal set by Congress. (A barrel of oil contains 42 gallons.)

The administration also proposed to increase federal receipts by about $1 billion by requiring the Bonneville Power Administration and four other power marketing administrations to pay back their debt to the Treasury more quickly and at higher interest rates.

The proposal follows the recommendations of the Grace Commission, a presidential advisory panel on cost-cutting, but is opposed by congressional representatives of the affected states because it would sharply increase utility rates.