Filters from bomb plant greatest potential for trouble

By N.S. Nokkentved
Times-News writer

Sunday, February 11, 2001

TWIN FALLS -- Perhaps the greatest risk of a spontaneous nuclear reaction in buried radioactive waste in Idaho is from air filters from a Colorado nuclear bomb factory.

Officials at the Idaho National Engineering and Environmental Laboratory say monitoring would have detected any spontaneous nuclear reactions in the buried waste. But documents obtained by The Times-News suggest no monitoring was done that would have detected such an event.

State and federal regulators met with Energy Department and INEEL officials from Dec. 6 to 8, 2000, to discuss the likelihood of a spontaneous nuclear reaction -- known as a criticality -- in plutonium-contaminated waste buried at the INEEL.

Such a criticality might not raise any immediate concern, but the possibility of such an event is a factor in deciding whether and how best to clean up the buried waste that threatens the Snake River Plain Aquifer.

INEEL officials denied a Freedom of Information Act request for minutes from that meeting, but The Times-News obtained the minutes elsewhere.

According to a draft of the minutes from Dec. 6, "There have not been any records identified to indicate that any monitoring for criticality was done during the flooding events."

INEEL spokesman Tim Jackson noted that the minutes say personnel were not contaminated during the flooding, and that shows personnel were monitored.

The monitoring has been a source of contention among federal and state agencies.

EPA officials suggest that a small spontaneous uncontrolled nuclear reaction might have gone undetected during one of three flooding events at the INEEL's burial ground.

Sue Stiger, head of environmental cleanup at INEEL, in December told The Times-News that monitoring was in place at the time that would have showed the evidence of a nuclear reaction.

"We would have been able to detect it," she said.

But EPA officials challenged the assertion that a past criticality would have been detected by the kind of monitoring done at the time. That conclusion could not be made without an evaluation of the personnel, their location and monitoring data from the time of the event, Wayne Pierre of the EPA's Seattle office said in his responses to the minutes.

With sufficient plutonium within a given space, water could act as a "moderator" during a flood and allow a nuclear reaction to occur. Without water, small amounts of plutonium are not likely to sustain a nuclear reaction.

The burial ground was flooded in 1962, 1969 and 1984. And officials agree that some waste containers potentially hold enough plutonium for such a reaction.

But INEEL officials assert that the material did not go critical during the flooding, the minutes say.

Not everyone at the meeting agreed, Pierre said.

"This issue is not closed," he said.

According to the minutes, based on what is known today, the Energy Department is not worried about a criticality risk.

But EPA officials are concerned, Pierre said. They are particularly concerned about air filters from the nuclear bomb plant at Rocky Flats, near Denver, Colo. The filters, most of them shipped to INEEL in wooden and cardboard boxes, were heavily loaded with plutonium.

Rocky Flats gave up trying to recover plutonium from the discarded filters.

The Rocky Flats Plant "aggressively tried to get the plutonium off the filters, but could not," retired plant supervisor Al Williams said in the minutes.

The filters were dumped in the burial ground pits along with the other waste. They may constitute the greatest risk of an accidental criticality, Pierre said. Yet information about the filters and the amount of plutonium they contain is uncertain.

Some data suggests that some drums of filters could contain more than one kilogram of plutonium distributed through the filters -- a favorable configuration for a potential criticality if water were present, Pierre said.

INEEL officials said the likelihood of finding such overloaded waste drums would be rare. But officials agreed to investigate the apparent gaps in information about filters.

From 1952 through 1970 plutonium-contaminated and other waste was dumped willy-nilly into pits and trenches at the 88-acre burial ground at INEEL -- a site now known as the Subsurface Disposal Area.

The waste came primarily from the nuclear bomb factory at Rocky Flats, near Denver.

What is a criticality?

A criticality is an uncontrolled nuclear reaction. In such an accident, nuclear materials sustain a reaction -- or "go critical," in the parlance of nuclear science. This is not the same as a nuclear explosion, but it releases energy, a characteristic blue glow and potentially lethal levels of radiation. The leftovers remain radioactive for many years.