**Savannah River Site**

Following is a list of major programs at the Savannah River Site and
suggested possible research directions for EMSP investigators. For more
detailed information can be obtained by contacting the site
representatives identified in each of the categories.

[WASTE STORAGE AND RETRIEVAL]{.underline}

CONTACTS: P. D d'Entremont (<paul.dentremont@srs.gov>)

W. R. Wilmarth (<bill.wilmarth@srs.gov>)

Site activities focus on minimizing HLW volume and retrieving HLW from
noncompliant tanks (i.e., tanks that do not have complete secondary
containment) and moving the waste into compliant tanks and/or into waste
treatment facilities. Minimizing HLW volume is accomplished primarily
through concentration of supernates in evaporators that operate at
atmospheric pressure and elevated temperatures (100 -- 170 °C).
Efficient and continued use of existing evaporators as well as the
subsequent retrieval and processing of HLW requires increased
understanding of the complex chemistry in the highly alkaline and
concentrated salt media with particular emphasis on precipitation of the
various problematic solids \[e.g., sodium aluminosilicate scale\].
Improved sampling and characterization tools (e.g., on-line and at-line
sensors/instruments) for HLW are also of value. Waste retrieval needs
include improved mechanical and chemical methods for waste retrieval
that can be implemented with minimal infrastructure investment and
within a variety of tank environments. Introduction of new chemicals
into the HLW system requires extensive evaluation of the impact on
downstream operations such as vitrification in the Defense Waste
Processing Facility (DWPF), waste pretreatment in the Salt Waste
Processing Facility (SWPF) and disposal of low level waste in cement
(Saltstone).

[WASTE TREATMENT AND DISPOSAL]{.underline}

CONTACTS: S. D. Fink (<samuel.fink@srs.gov>)

> E. W. Holtzscheiter
> ([bill.holtzscheiter@srs.gov](../bill.holtzscheiter@srs.gov))

Major programs in support of HLW treatment and disposal at SRS include
salt processing, increased waste loadings in HLW glass and throughput in
the DWPF, and vitrification of excess plutonium.

Salt processing needs focus on developing alternative technologies for
the processing of SRS high-level waste salt that allow faster processing
without sacrificing the current cost savings and that will allow earlier
completion of the baseline approach. The technology initiatives take the
form of reducing the schedule for completing salt processing or reducing
overall costs for salt processing by demonstrating alternative
approaches that can be deployed as quickly as possible, utilizing
existing facilities whenever possible. Currently, the program includes
the following tasks.

-   Design and deployment of a small solvent extraction system to pilot
    the technology planned within the SWPF.

.

-   Design and deployment of an ion exchange system using crystalline
    silicotitanate for selective removal of radioactive cesium.

-   Development of an engineered form of monosodium titanate \[MST\] for
    removal of actinides and strontium from waste.

-   Development of an optimized form of MST or a replacement sorbent.

-   Development of an In Situ Mixed Iron Oxide process for precipitation
    of actinides and strontium from waste.

-   Evaluation of alternate filter media for removal of solids from
    waste.

-   Design, fabrication, and deployment of a rotary microfilter for
    removal of solids containing radionuclides from the waste. Prior
    demonstration shows the rotary filter offers a 6-10X improvement in
    throughput over the baseline technology, conventional cross-flow
    filtration, while requiring less space and costs.

-   Development of a process to dispose of legacy organic waste
    contained within Tank 48H. The tank contains 250,000 gallons of
    alkaline slurry with tetraphenylborate solids.

Increased waste loadings in HLW glass and processing rates in the DWPF
are major initiatives in accelerating cleanup at the SRS. Currently, the
DWPF is limited in throughput as the waste loading is increased.
Depending on feed composition, the practical limit on waste loading in
the current design is likely in the range of 40 to 45 weight percent
before gains are off-set by reduced throughput due to melt rate.
Changing rheological properties of HLW sludges can also impact
throughput in the DWPF. Development of alternate melter designs and
glass formulations that could accommodate higher waste loading at higher
throughput would significantly accelerate the cleanup schedule and
decrease program costs. Understanding factors that influence rheology,
air entrainment and foaming and changes in these properties that occur
during chemical processing ensures that the DWPF can increase waste
loading and maintain or improve processing rate.

There is a considerable quantity of EM-owned weapons-usable
plutonium-bearing materials that have no clear disposition path.
Vitrification appears to be a viable option for disposition of this
material that is not suitable for burning as a mixed oxide (MOX) fuel.
Additional glass chemistry efforts are needed to optimize the glass
formulation for the current plutonium feed streams. Testing to
demonstrate the vitrification process will also be necessary to
facilitate flowsheet development and equipment specification. Finally,
waste form characterization and performance testing will be necessary as
part of the waste acceptance process for disposition of this waste form
in the Federal Radioactive Waste Repository.

WASTE TANK CLOSURE

CONTACTS: P. D. d'Entremont (<paul.dentremont@srs.gov>)

> B. A. Hamm (<barbara.hamm@srs.gov>)

Tank closure program needs include improved methods to reduce the
quantity of residual materials in the tanks, development of tank fill
materials and improved models for evaluating releases from the closed
tanks as part of long-term performance assessments. Tank cleaning
methods include both mechanical and chemical methods. The use of
chemical agents to clean tanks requires extensive evaluation of the
impact on downstream operations such as vitrification in the DWPF, waste
pretreatment in the SWPF and disposal of low level waste in Saltstone.
Previously closed tanks at SRS utilized grout and consolidated low
strength materials to fill the tank interior spaces. New fill materials
that retard radionuclide and hazardous chemicals will likely be needed
so that the closed tank meets increasingly restrictive permit
requirements.