17    TRANSPORTATION OF A
40-YEAR-OLD REACTIVE MIXED WASTE
Charles G. Dietz, Staff Engineer/Scientist
Idaho National Engineering Laboratory
Idaho Falls, Idaho 83415
INTRODUCTION
Now a national landmark. Experimental Breeder Reactor-I was the world's first nuclear reactor
to produce a usable amount of commercial electricity in 1951. It is located on the Arco desert in
Eastern Idaho at the Idaho National Engineering Laboratory (INEL). In 1955, the reactor experienced a cooling accident that resulted in core damage and a partial meltdown of the reactor,
which left a serious cleanup challenge that had not been addressed until recently.
The EBR-I reactor used liquid metal sodium-potassium (NaK) as a coolant because it is eutec-
tic; that is, it remains a liquid at the lowest possible temperature and was a very effective
coolant. NaK looks very much like mercury out of a thermometer. However, NaK is reactive and
will burn in the presence of air (absorbing moisture from it) and is extremely reactive in direct
contact with water, producing hydrogen. Furthermore, this highly reactive coolant was radioac-
tively contaminated from the accident.
Most of the radioactively contaminated NaK was processed and disposed of in 1955. However,
approximately 180 gal of residual contaminated NaK remained because of the possibility it contained ten 1-gram foils of plutonium, which were in the reactor core at the time of the meltdown.
This NaK was stored in four containers: two 55-gallon stainless steel transportation drums, one
60-gallon carbon steel container (used as a transfer vessel), and one 10-gallon carbon steel container (used to store radioactively contaminated water).
Contaminatd NaK at the INEL for 20 Years
The INEL decided not to treat the waste in the four containers, and so it was stored at the
EBR-I reactor site until 1974, when EBR-I was decontaminated and decommissioned. A new
storage location was needed, so a remote bunker was selected, the Army Reentry Vehicle Site
Facility (ARVFS), left from the days when the Army was conducting a study of radiation effects
on reentry vehicle components. Until an option for treating the NaK could be identified, the four
containers were placed in a typical sheet metal dumpster with sand beneath and around each container, and the dumpster was placed in the bunker, which was 3 feet below the desert surface.
The bunker had a steel plate tack-welded across its opening, and drains were constructed to prevent water from entering the bunker. In 1979, the bunker was opened and the dumpster was removed so the waste containers could be inspected. Some rust was apparent on the carbon steel
containers, so the sand was removed and replaced with vermiculite, which absorbs less moisture
and has the ability to suppress any NaK fire that might occur.
RCRA Compliance Concerns
During the 20 years the NaK was in the ARVFS bunker, environmental laws developed and
legal requirements concerning storage of the NaK changed dramatically. The Resource Conservation and Recovery Act (RCRA) now required weekly inspections of individual waste containers. However, 2 feet of vermiculite, a steel plate welded shut, and a reactive radioactively contaminated waste of uncertain nature, possibly contaminated with plutonium, did not lend itself to
weekly inspections. The INEL was clearly out of compliance with RCRA and needed to resolve
51st Purdue Industrial Waste Conference Proceedings, 1996, Ann Arbor Press, Inc.. Chelsea, Michigan 48118.
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