The Reagan administration didn't obliterate the Energy Department in its fiscal 1984 budget proposal as it did in last year's version, but it still requests deep cuts for the civilian side of the department.

This year's budget acknowledges the department once again, although Secretary Donald P. Hodel said that the figures for the management side of the agency assume some savings based on the Reagan administration's desire to fold it into the Commerce Department and other agencies.

"If nothing is forthcoming in the way of reorganizational activity," Hodel told a departmental budget briefing, "that will have to be a subsequent adjustment. But we have already proven at least once that we are capable of doing that."

The $101 million proposed for energy conservation is well above the $22 million that the administration sought a year ago, but still considerably less than the $279 million that Congress appropriated for fiscal 1983. The story is the same for the $102 million proposed for solar and other renewable forms of energy, and the $138 million proposed for fossil energy research and development.

On the other hand, the administration wants to increase department spending for "defense activities" by $1 billion to support full-scale production of a variety of nuclear warheads, including the Trident, Pershing and cruise missiles.

The budget also includes $270 million to start construction of the controversial Clinch River fast breeder reactor in Tennessee, which the House almost managed to kill during the lame-duck session of Congress late last year. Hodel acknowledged that unless the department turns up some private sector funding for the reactor, Congress is unlikely to support it this year.