The Energy Department wants to stop processing materials for nuclear weapons at four plants in its weapons complex in the 1990s, according to a summary of a report to Congress. Recommended to be phased out or relocated are:

- The Fernald Feed Materials Production Center near Cincinnati, which would be shut down.- The Rocky Flats Plant near Denver, whose operations would be transferred elsewhere.

- Mound Nuclear Materials Operations in Miamisburg, Ohio, whose operations would be relocated.

- The Hanford Plant in eastern Washington State, whose nuclear materials production would be relocated.

Details of proposed relocation sites were not included in the summary.

DOE estimates the cost of cleaning up widespread contamination and upgrading the entire complex - including restarting three shut-down reactors at the Savannah River Plant in South Carolina - at $81 billion over the next 21 years. Of that figure, $29 billion would be devoted to environmental cleanup.

The figures mean the government would have to spend half again what it does now - up from about $8 billion to $12 billion each year - to maintain nuclear weapons production into the next century.

The U.S. nuclear arsenal has been stocked since the 1950s by more than 100 plants in 27 states.

The summary generally confirms previously reported DOE plans to modernize and consolidate its aging weapons facilities. Some plants have been contaminating their communities for decades, while some have become at least temporarily inoperable.

The "2010 report," which projects spending needs to that year, is based on the assumption that "nuclear weapons will remain a principal element of the security of the United States for the forseeable future," its summary says.

Decontamination and management of radioactive and hazardous wastes will go on long after upgrading and relocation of weapons plants are finished, the report notes, saying cleanup would "continue until completion."