Reducing the Risks of High-Level Radioactive Wastes at Hanford

62 Alvarez
Table 3: Summary of melter-related incidents in the DOE. (Continued)
Incident Corrective action Lessons learned
Oak Ridge National
Laboratory A radioactive
waste In situ Vitrification
Plant experienced a
steam explosion which
resulted in the release of
off gas and an expulsion
of 20,000 kgs of molten
glass, spewing fragments
100 m from the melter
site. (1996)
Hanford A large-scale test
of In situ Vitrification on a
buried 6000-gal tank
resulted in a steam
explosion which raised
the off-gas hood 12 in.
from the ground and the
expulsion of molten soil.
(1991)
Recommended corrective
actions included diversion
of standing water around
the pit, installation of
flow-monitors and curved
vent pipes beneath the
melt to provide alternate
paths for steam, submelt
pressure measurement,
and video monitoring of
the melt surface.
The facility was shut down.
Melters should have
safeguards
designed to
account for not only
normal operating
conditions, but also
for abnormal
conditions such as
steam explosion.
The cause was
ascribed to sealing
of the walls of the
tank to the melt
body precluding
normal pathway for
dissipation of steam
from the melt.
Sources: Vijay Jain, Process Safety Issues Associated with Melter Operations During Vitrification
of Radioactive Wastes, Proceedings of the XVIII International Congress on Glass, 2000, and
ORNL/ER-371.
effects of chemical hazards.... The normally accepted practice and NRC
regulatory emphasis are minimization of the reliance upon administrative
controls.” 100
A key safety concern where engineering controls are important is fireproofing
and fire suppression. The Waste Treatment Plant will be handling large
quantities of flammable materials. However, DOE and its contractors are cutting
costs by reducing steel fireproofing and fire suppression requirements. In
2000, the NRC objected to this approach because it would “severely limit any
future modifications” and “lack of fire suppression capability along with lack of
steel protection in the same area makes administrative control of combustibles
the only defense measure . . .” 101
In April 2003, the Office of Environmental Management’s Director of for
Safety and Engineering at DOE’s Headquarters, reiterated the NRC’s concerns
regarding a decision made by ORP to reduce fire protection requirements at
the Waste Treatment Plant. 102 It was pointed out that one of the areas, which
was given a “low” combustible rating would have to withstand fires that are
“equivalent of 2,370 pounds of wood in an area the size of an individual office.”
Moreover, “the construction contractor has also proposed a combustible
decontamination coating in lieu of stainless steel on all surfaces which will
appreciably add to the combustible loading in these spaces.” 103
Like the NRC, the headquarters review found that “administrative controls
are not an approach that would be intentionally selected for new facilities