The barrel rotated as its innards were X-rayed.

Hoses. Tools. Clothes. Cans. Various contaminated odds and ends.

The screen in the control room overlooking the X-ray chamber in a Hanford 200 West Area building showed everything inside the barrel.

What the person watching the screen is looking for is a straight, horizontal line that wiggles as the barrel turns.

That means liquids are inside, and that's a no-no.

If a barrel is solid and tight -and dry inside - it's safe to permanently bury at Hanford or store at a federal site in New Mexico.

But if liquids are inside, they're probably contaminated - and pose environmental and health threats if the barrel cracks.

Any small containers holding liquids have to be removed from the barrels, and any fluids are drained into cans.

These barrels and boxes hold Hanford's "transuranic" and "mixed low-level" wastes - fancy terms for what is essentially radioactive junk collected from numerous Hanford projects and stashed inside drums.

Disposal of these substances recently has entered a pivotal time at Hanford.

The site is beginning to take care of these wastes faster than they are being produced - chipping away at Hanford's overall volume of tens of thousands of barrels stored in trenches and buildings along the 200 West Area's western edge.

But lurking in the background is a major problem: the barrels are deteriorating, and some are now to the point where their walls are thinner than desired. They could crack or break when moved.

This deterioration poses a potentially significant health threat to the workers handling those drums if those barrels crack or break, said Dick Wilde, vice president for waste management for Waste Management Federal Services of Hanford, the contractor in charge of this project.

Anywhere else, such vast amounts of transuranic and mixed-level wastes would be a high-profile problem.

But at Hanford, these wastes pale in comparison to much bigger headaches such as leak-prone water basins and underground tanks holding huge amounts of spent nuclear fuel and other high-level radioactive wastes, safety problems at a plutonium storage site and contaminated ground water.

"We don't have the uncertainty found in programs at (the tank farms) and the vadose zone. But we don't have the same urgency," Jay Augustenborg, the Department of Energy's deputy assistant manager for waste management.

Compared with other Hanford problems, transuranic and mixed low-level wastes are easy to deal with.

The barrels' contents are more or less known. And the cleanup plans don't require the extensive research and funding the tank waste and spent fuel projects need.

Although backlogs should be drastically reduced in the next few years, Hanford will keep producing these wastes for decades, which will keep the treatment and disposal programs running.

The fact Hanford has now reached a "plateau" where it is "treating" more mixed low-level wastes than it produces means Hanford should eliminate about 80 percent of its backlog by 2006, Wilde said.

The current backlog of mixed low-level wastes fills 8,000 55-gallon barrels, which are now stored in several buildings in the 200 West Area.

"Treating" means X-raying the barrels and boxes. Chemicals and some items are burned or encased in cement. If needed, weakened containers are put in stronger containers.

The transuranic wastes are expected to reach a similar "plateau" in 1999, and the backlog volume of those wastes also will start to shrink.

Transuranic wastes are now stored in the 200 West Area in barrels stacked in open trenches or in metal buildings. That waste could fill about 38,000 55-gallon drums.

Hanford plans to begin sending those barrels through a building dubbed the Waste Receiving and Packaging facility - or WRAP - in early 1998. In the WRAP, the barrels will be X-rayed and any liquids or liquid-filled containers removed.

Beginning in May 1999, the barrels are expected to be shipped to the Waste Isolation Pilot Project, a huge underground permanent storage site in New Mexico.

Wilde and Augustenborg estimate it will take until about 2031 for the WRAP to eventually ship all the transuranic wastes to the WIPP. That assumes modest annual budgets of about $12 million because this program is not a top Hanford priority.

But these wastes cannot totally be put on a back burner because old age is catching up with the barrels.

Wilde said the rule of thumb is that the integrity of a steel barrel of transuranic wastes becomes suspect when it corrodes to a thickness of less than 40 mils - or 0.04 inch as measured by an ultrasonic device.

From 1970 to 1972, the transuranic waste barrels had walls that were 50 mils thick, and 9,000 of these drums were buried directly in the soil. By now, most of these have deteriorated to less than 40 mils thick, according to Waste Management's calculations. Right now, barrels buried from 1973 to 1975 nearly are at the 40-mil mark. And drums buried from 1976 and 1980 could corrode and rust to an unsafe thickness anytime between 2000 and 2015.

In 1988, Hanford quit putting transuranic wastes into trenches altogether and started storing them in metal buildings.

But what about barrels buried in central Hanford before 1970?

That currently is an unanswered question because of all sorts of uncertainties over what exactly is in those drums - and how many there are.

The deadline for figuring out what to do with the pre-1970 transuranic wastes is 2008.