Reducing the Risks of High-Level Radioactive Wastes at Hanford

60 Alvarez
that “few tests appear to be planned to verify safety parameters prior to
construction.” 87,88 NRC’s concluded that DOE and its contractors had sufficient
knowledge and capabilities to mitigate the likelihood probability to
1E-4. 89
“Further analysis” was required, however, to determine if melter risks could
meet probabilities acceptable under NRC regulations for reactors and fuel cycle
facilities (10 CFR 70). 90
Based on review of the nine high-level radioactive waste and several
low-level and mixed waste vitrification facilities throughout the world, NRCsponsored
research points out that “operating limits on chemical composition,
redox control, and glass properties such as viscosity, electrical resistivity, phase
separation and liquidious temperature should be established before start of the
radioactive process.” 91 Failure to meet these conditions have led to serious problems.
For instance, since 1991, there have been eight melter-related incidents
and failures in the DOE complex. 92 ,93 (See Table 3.)
On one instance, on 21 April 1996 pressurized steam vented rapidly through
the melted glass the Oak Ridge low-level, In Situ Vitrification (ISV) plant and
caused an explosion that expelled 20,000 kgs of glass, spewing hot fragments
over 100 meters from the melter site. 94
Of major concern to the NRC was that, proposed designs “do not consider
prevention and controls [and] do not include important auxiliary effects in the
analyses, such as common mode failures, operability, recoverability, and plant
habitability for operators” 95 The NRC concluded that “regulatory and safety
issues associated with a much larger facility do not appear to have been considered
... On many occasions, there was an implication that regulatory reviews
were not allowed to impact cost and schedule ... 96
However, since the NRC ended its relationship, DOE has taken steps to “reduce
conservatism” in its high-level waste safety controls at Hanford to “allow
work to be performed more quickly.” 97 As a result DOE and its contractors
have significantly curtailed safety analyses and oversight, reduced operational
safety procedures, and eliminated DOE approval of important changes in safety
analyses and subsequent construction decisions.
Efforts to “reduce conservatism” have now, however, proven to be costly
and time consuming. In 2003 the Defense Nuclear Facility Safety Board took
issue with the design assumptions about earthquakes stating that the Hanford
site could experience destructive seismic activity 15% greater than California
sites. 98 In March 2005, after subsequent testing, the Energy department was
compelled to suspend construction for facilities that would handle a preponderance
of wastes and to increase the design standard from 20 percent to 40
percent. 99
DOE’s preference for administrative over engineering controls, because
they cost less is also of concern. According to NRC, DOEs approach “appears
to rely extensively on operator actions to prevent or mitigate the