Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: SATURDAY, November 26, 1994 TAG: 9411280036
SECTION: NATIONAL/INTERNATIONAL PAGE: A1 EDITION: METRO
SOURCE: ASSOCIATED PRESS
DATELINE: OAK RIDGE, TENN. LENGTH: Medium
Several pounds of weapons-grade uranium seeped from fuel storage at a long- dormant research reactor and collected in a filter pipe, where it could have created an uncontrolled chain reaction.
Crews at the Oak Ridge National Laboratory removed water from the area where the uranium was discovered earlier this year, to prevent it from getting into the pipe and possibly contributing to the start of a chain reaction.
The water ``was the alligator in the swamp, and we got that alligator out,'' said Clayton Gist of the Energy Department's Oak Ridge office.
Water in nuclear reactors helps slow flying subatomic particles called neutrons, making them more likely to smash into uranium atoms.
The incident involved the Molten Salt Reactor Experiment, which has been shut since 1969. A molten radioactive salt compound circulated through the reactor core, acting as both coolant and fuel.
The experiment was a high-profile project in the 1960s, intended to demonstrate a new concept for possible adaptation in commercial power reactors.
After the shutdown, workers didn't realize that chemical reactions inside storage tanks of the salt at the reactor facility were releasing uranium hexafluoride gas. Officials believe the uranium in the charcoal filter condensed from that gas.
Crews still have to remove the uranium and get rid of other radioactive remnants of the experiment.
``The system has been sitting here for nigh on 20-plus to 30 years with the salt in place,'' Gist told The Knoxville News-Sentinel. ``It was never designed to do that.''
Gist said workers were acting to seal all valves and prevent further migration of the uranium. He said it may be necessary to use remote-control technology to get the uranium out, to minimize workers' radiation exposure.
About six pounds of uranium 233 was found in the filter. The mass was sufficient to pose the threat of an uncontrolled nuclear chain reaction; employees in nearby offices were relocated as a precaution.
Asked what would have happened in case of such an event, Gist said it would have caused high radiation levels in an area within a few yards of the reaction.
``There would not have been an immediately lethal radiation release,'' Gist said. But he said that a person standing within that small area for an extended period could get a lethal dose of radiation.
by CNB