WASHINGTON (AP) _ The Energy Department warns that aging atomic waste tanks at a nuclear reservation in Washington state could leak high-level radiation before safety problems are resolved after the turn of the century.

The DOE report to Congress Friday said it will take until the year 2000 to eliminate dangers of flammable gas generation in 23 tanks and 2004 to fully address the potential explosive mixtures of ferrocyanide in 24 tanks at the site in Richland, Wash.

In the meantime, the department is pursing ''near-term'' safety measures at the Hanford Nuclear Reservation including, among other things, ''emergency preparedness planning.''

''Resolution of all safety issues will probably take more than 10 years'' the report said.

Priority work will be done on the tanks that ''could lead to worker (onsite) or offsite radiation exposure through an uncontrolled release of radioactive waste,'' the DOE said.

Department officials briefed congressional staffers Friday about the status of Hanford's 177 underground storage tanks, which house about half of the nation's high-level nuclear waste.

An aide to Rep. Ron Wyden, D-Ore., provided a copy of the report to The Associated Press.

Congress requested the DOE assessment after the General Accounting Office determined last fall that too little is known about the waste to rule out the possibility of an explosion that could spread dangerous doses of contamination.

The new report maintains there is a ''low probability'' of an explosion because there are no known ignition sources in the tanks and temperatures are well below those required to initiate chemical reaction.

However, the DOE outlined a series of concerns about the ''degraded conditions'' of the 149 single-shelled tanks and 28 newer double-shelled tanks in the south-central Washington desert bordering the Columbia River.

''Sixty-six of the single-shelled tanks are either suspected or known to have leaked liquid radioactive waste to the ground and the remaining tanks can be expected to start leaking at any time in the future,'' DOE said.

Many of the tanks are nearly 50 years old, dating back to 1943 with production of plutonium for the nation's first nuclear bombs. The tank farm now contains 60 million gallons of radioactive liquid, sludge and saltcake.

DOE has identified 53 tanks ''that may have serious potential for release of high-level radioactive waste in the event of an uncontrolled temperature or pressure increase,'' the report said.

''Tank collapse scenarios, in particular as they relate to seismic events, could lead to significant onsite radiological releases and potentially significant offsite releases,'' the report said.

Most of the concerns are due to the age of the tanks as well as the shortage of money and technology to address the problems in a timely fashion, DOE said.

''The Hanford Site single-shelled tanks have exceeded their original design life and the early double-shelled tanks are fast approaching their technical specification life.

''The steel liners of approximately half of the single-shelled tanks have already leaked and all single-shelled tanks are considered potential leakers. No double-shelled tanks have leaked to date, but corrosion studies indicate that liners could start leaking as they exceed their design life, which could happen before solidification operation is completed,'' the report said.

The DOE said that because it previously assumed that disposal of the waste would begin in the 1990s, waste management funding for storage upgrades was phased down over the past two decades.

''This approach can no longer be tolerated,'' the report said.