Opinions differ on possible nuclear reactions
http://www.magicvalley.com/timesnews/news/index.asp?view=news5
By N.S. Nokkentved
Times-News writer

TWIN FALLS -- A small runaway nuclear reaction might have gone unnoticed years ago in radioactive waste buried willy-nilly in eastern Idaho, some experts suggest.

Federal energy officials assert that the risk of such an event is not credible.

"We have found no evidence of a criticality ever having occurred out there," INEEL spokesman Nick Nichols said.

Yet state and federal environmental regulators say they have seen no evidence that would rule out an accidental nuclear reaction -- known as a criticality -- in the buried waste, either in the past or in the future.

Recent concerns about a criticality were raised when data gathered from radioactive waste in INEEL's controversial Pit 9 suggested some barrels might contain enough plutonium to support a spontaneous nuclear reaction.

In a worst-case scenario, an uncontrolled criticality might release radioactive materials into the air. It also could ignite other radioactive waste, and the resulting fire might lead to additional radioactive releases.

Consultants to the EPA wrote in a May report that "no conclusive evidence has been presented to date that places the future risk of nuclear criticality in the (burial waste site) at an insignificant level."

In early December, Energy Department and regulatory officials met to discuss the issue of criticality risks in the waste buried at the INEEL's Subsurface Disposal Area. Following that meeting, one consultant wrote that the INEEL assertions that no criticality happened while the burial ground was flooded should be supported by calculations, and monitoring data from before, during and after the event.

Sue Stiger, head of environmental cleanup at INEEL, said monitoring was in place that would have showed the evidence of a nuclear reaction.

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

Plutonium-contaminated waste has been stored at INEEL for almost 50 years. More than 2 million cubic feet of such waste was dumped in pits and trenches -- including Pit 9 -- between 1954 and 1970.

INEEL officials are confident that the plutonium is spread out through the waste and doesn't present a risk of a spontaneous, uncontrolled nuclear reaction.

But that assertion is based on data from electronic probes sunk into Pit 9. That data is open to interpretation, said Wayne Pierre of the Seattle office of the Environmental Protection Agency and project manager for INEEL cleanup. Energy Department assertions about the waste are based on supposition, not on physical data, and the department has been reluctant to take actual physical samples, he said.

The possibility of a spontaneous, uncontrolled nuclear reaction becomes a regulatory concern when a barrel of waste has 267 grams of plutonium. And the sampling data suggests some barrels might have 200 to 1,000 grams of plutonium.

In a previous interview, Jerry Paulson, director of criticality safety at INEEL, said a nuclear criticality would require sufficient water in addition to the right amount of plutonium.

Water acts as a moderator, increasing the effectiveness and concentrating the reaction. Without the water, small amounts of plutonium are not likely to sustain a nuclear reaction, Paulson said.

But the buried waste pits and trenches at INEEL have flooded three times in the past, and those floods may have provided enough water.

The first flood was in February 1962, when two inches of rain fell on eight inches of snow in three days. With the topsoil still frozen, water collected in open waste pits and trenches.

Then in January 1969, snowdrifts blocked a drainage ditch dug following the earlier flood. Melting snow and rain once again filled open pits and trenches.

Again in 1982, flood waters inundated pits and trenches.

Chuck Broscious, head of the Environmental Defense Institute in Troy, suggests that two fires in a trench in 1966 and another fire in 1970 might have been the result of criticalities. Efforts to douse the third fire failed until a bulldozer operator covered the waste pile with dirt.

The fire was the result of spontaneous combustion of uranium waste, not a criticality, Stiger said.

INEEL's early decades of waste dumping are known for spotty record keeping. Inventories were incomplete, and radioactivity levels often were estimates rather than measurements.

Officials now have better records about what was actually sent to INEEL then they did a few years ago, Stigar said.

Criticality is something officials take very seriously, but officials at the December meeting agreed a criticality is not a concern at the INEEL radioactive waste disposal site, Stiger said.

Times-News writer N.S. Nokkentved can be reached at 733-0931, Ext. 237, or by e-mail niels@magicvalley.com

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.