Reducing the Risks of High-Level Radioactive Wastes at Hanford

72 Alvarez
melter vessel, allowing molten glass to leak/drop out of the melter, uncontrolled
off gas from the melter, failure of the joule-heating system, and plugging of the
glass pour drain.” 157
The Hanford vitrification plant will have the largest melters in the world—
two for high-level wastes and the other for low-activity wastes. Initially the
TWRS program was to begin with a relatively small, pilot plant that would
process between 6 to 13 percent of Hanford’s tank waste. This would have
allowed verification of design and technical approaches with minimal economic,
programmatic, and safety risk.
For instance, according to NRC-sponsored research the use of surrogate
wastes, as is the case with current Hanford melter tests, may prove inadequate
because “actual Hanford wastes may be more reactive.” 158 But the pilot plant
was scrapped, despite recommendations by the NAS, NRC, GAO and DOE’s
construction contractor. 159 Instead the Energy department has decided to concurrently
design and construct a full industrial-scale operation based on the
concept of “learn by doing.” 160
As noted in 2001 by a DOE- sponsored review of nuclear waste vitrification
melters: “Construction costs, although important, are not major determinants
in life-cycle cost...., High-level waste operating cost savings from
increased waste loading or throughput may not be attainable without corresponding
throughput improvements (or additional facilities) in retrieval, pretreatment,
and low-level waste vitrification.” 161 DOE’s approach is already
facing “potentially large cost and schedule overruns and performance shortfalls,”
predicted two years ago by the National Research Council. 162 For instance,
in February 2004, it was discovered that an already installed waste
processing tank did not meet safety inspection requirements after seven similar
vessels were more than 94 percent fabricated, with similar flaws. Dozens
of the welds in other waste processing tanks were also found to be “undersized
or undercut, or have inadequate contouring.” Apparently Bechtel and
the fabricator did not check to see if tank construction comported with design
drawings. 163 As a result of problems like these, estimated construction costs for
the treatment plant have grown by more than 25 percent, from $4.35 Billion to
$5.78 Billion. 164
In the absence of pilot operations using actual Hanford Wastes, DOE faces
several major challenges:
Pretreatment. This involves separation of radionuclides from soluble
wastes, and chemical washing of insoluble tank sludges, prior to making feed for
the melter. According to DOE, pretreatment “represents a significant portion
of the HLW management costs and of the technical risk.” 165 At Hanford, processes
to remove corrosive metals, such as chromium, from tank sludge “are not
effective.” 166 ,167 The inability to remove sulfate adversely impacts low-activity
waste glass production, which remains an important concern. Moreover, DOE
has not been able to demonstrate that large-scale decontamination of soluble