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PART 1: OVERVIEW OF PREVIOUS NATIONAL
RESEARCH COUNCIL STUDIES ON WASTE AND
ENVIRONMENTAL MANAGEMENT
The National Research Council (NRC) has a long record of advising the federal
government on the management and cleanup of nuclear weapons-related wastes.6 The NRC
appointed its first study committee on radioactive waste management and disposal practices in
1955 to advise the Atomic Energy Commission (AEC). In its first two decades of operations,
this NRC committee published eight technical reports (NRC 1956, 1957, 1966, 1970a,b, 1972,
1974, 1975) and one individual paper (NRC 1958) that examined R&D activities and waste
management and disposal practices at the large AEC sites.7
Starting in 1976, NRC committees began a more intensive examination of disposal
practices at these sites, which were then being managed by the Energy Research and
Development Administration8 (ERDA) and later by DOE. A 1976 report focused on the shallow
land burial of wastes at ERDA sites (NRC 1976; see also NRC 1993). Later reports provided
reviews of waste management programs, plans, and practices at the Hanford (NRC 1978b,
1985a, 1992c), Idaho (NRC 1991b, 1994a), Savannah River (NRC 1981) and Oak Ridge
(NRC 1985b). In 1987, the NRC published reports on the management of buried low-level and
transuranic waste and contaminated soil (NRC 1987b) and also on management of uranium
mill tailings (NRC 1987c).
During that same time period, other NRC committees were established to advise DOE
on development of what was to become the Waste Isolation Pilot Plant (NRC 1979c,d,1980,
1983, 1984a, 1987a, 1988a,b, 1989b, 1991a, 1992b, 1996e, 2000c, 2001e,h, 2002b, 2004).
WIPP is now being used to dispose of defense transuranic waste that originated within DOE
and its predecessor agencies.
With the creation of DOE-EM in 1989, the focus of NRC work expanded to include
environmental cleanup. The first NRC report focusing almost exclusively on environmental
cleanup was published in 1989 (NRC 1989a). That report provided a review of a draft DOE
environmental restoration and waste management plan. Also in 1989, the NRC provided a
review of a draft DOE plan for applied research, development, demonstration, and testing to
support the cleanup program (NRC, 1989c).
In 1994, the NRC established a Committee on Environmental Management
Technologies to advise EM on technology development and use. This committee and its
successor committees produced a series of reports addressing technology development in five
“focus areas” identified by EM: Contaminant plumes, landfills, high-level wastes, mixed
6
A complete list of NRC reports on waste management and environmental cleanup of the nuclear
weapons complex is given in Appendix A.
7
Hanford, Oak Ridge, Savannah River, and the National Reactor Testing Station, the latter of which is
now part of Idaho National Laboratory.
8
The AEC was created by the Atomic Energy Act (1946) to control and promote the use of nuclear
power. The AEC was abolished by the Energy Reorganization Act (1974) and two new agencies were
created in its place: Energy Research and Development Administration (ERDA) and Nuclear Regulatory
Commission. A subsequent Energy Reorganization Act (1977) reorganized ERDA into the Department
of Energy.
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Part 1: Overview of Previous National Research Council Studies 7
wastes, and decontamination and decommissioning (NRC 1995b, 1996a, 1998e, 1999b,c,d,g).
During that same period, another NRC committee published a series of reports advising EM
on the management of buried and tank wastes and other related issues (NRC 1994a,b, 1995a,
1996b,c,d, 1997b, 1998b, 2000d).
In 1995, then-Assistant Secretary Grumbly also requested that the NRC establish a
committee to evaluate the science, engineering, and health basis for EM’s Environmental
Management Program. The report from that activity, Improving the Environment (NRC 1995c),
included an extensive discussion on the utilization of science, engineering, and technology in
the cleanup program. Subsequent NRC reports addressed technology development and
selection decision making (NRC 1998c, 1999e), R&D portfolio development and funding (NRC
2001g), and the use of peer review in technology development programs (NRC 1997d,
1999a). The 1999 peer review report was cited by the Office of Management and Budget in its
standards for agency peer reviews.
In 1995, Congress created the Environmental Management Science Program (EMSP)
to develop new knowledge and tools for the cleanup effort. The program was housed within
EM but was jointly managed with the DOE Office of Science. At the request of EM, the NRC
undertook a series of studies beginning in 1996 to advise on the implementation of this
program. The first three reports focused on the structure and management of the EMSP (NRC
1996g,h, 1997c). Later reports identified knowledge gaps and research needs on the following
topics:
Contaminated soil and groundwater (NRC 1998d, 2000a)
High-level waste (NRC 2000f, 2001d)
Deactivation and decommissioning (NRC 2000g, 2001c)
Transuranic and mixed waste (NRC 2002c)
Excess nuclear materials and spent fuel (NRC 2003a)
The recommendations in these reports were used by EM and the Office of Science to
develop the annual research solicitations for the EMSP. The EMSP was transferred to the
Office of Science in fiscal year 2003 and now focuses on primarily soil and groundwater
related research.
Over the past decade, the NRC has published several reports focused on specific site
cleanup problems. These include groundwater cleanup at Hanford (NRC 2001f) and the Los
Alamos National Laboratory (NRC 2006b), high-level waste processing at Idaho, Hanford, and
Savannah River (NRC 1999f,h, 2000e, 2001a,b; 2005d, 2006a), remediation of the Moab,
Utah mill tailings site (NRC 2002a), and long-term institutional management of early closure
sites (NRC 2003b). The NRC has also undertaken broader based examinations of technology
development and technology use in soil and groundwater cleanup (NRC 1994d, 1997e,
2000b). Other recent NRC reports have examined the use of risk analysis in cleanup decision
making (NRC 2005b) and opportunities for accelerating DOE’s cleanup efforts (NRC 2005c).
As illustrated by this summary, NRC studies have examined and reported on a
remarkable range of waste management, cleanup, and disposal issues over the past half
century. The thousands of pages of information, analyses, and discussions contained in these
reports continue to be a valuable resource for DOE managers, technical staff at DOE sites,
national laboratory staff, and Congress.
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Part 1: Overview of Previous National Research Council Studies 8
Although some of the older reports are outdated, they still provide an important
historical record of the federal government’s efforts to manage the environmental legacy of the
nation’s nuclear weapons production and testing programs. Many and perhaps most of these
reports still contain relevant information and advice that can help to inform future cleanup
efforts.
SYNTHESIS OF PREVIOUS NATIONAL RESEARCH COUNCIL
REPORTS ON SCIENCE AND TECHNOLOGY GAPS FOR DOE SITE
CLEANUP
This section provides a high-level synthesis of science and technology gaps derived
from previous NRC reports. Interested readers are encouraged to read the original reports to
obtain more details. Most of the reports published since 1994 can be read online (web
addresses for these reports are provided in Appendix A).
NRC reports identify science and technology gaps using a variety of labels: for
example, research needs, technology needs, cleanup challenges, and knowledge gaps. These
reports were also written for different audiences—basic researchers, technology program
managers, EM management, and Congress—and consequently these needs, challenges, and
gaps are written in different styles with different levels of supporting detail. In developing this
synthesis, these needs, challenges, and gaps have been combined, reordered, and in some
cases reworded to remove specialized jargon and provide a consistent level of supporting
detail.
The science and technology gaps were derived primarily from NRC reports on cleanup
challenges at the large DOE sites and therefore tend to be biased toward those sites’ research
and development needs. Some of the identified gaps will require basic research, whereas
others will require a combination of applied research and technology development. Some of
the gaps can probably be addressed in short time frames (1-5 years), whereas others will
require medium- (5-10 year) and longer-term (>10 year) efforts.
Science and technology gaps have been organized as follows:
High-level waste and tank cleanup
Facility9 cleanup
Groundwater and soil cleanup
Waste and contamination containment
Containment monitoring
These gaps were not prioritized in previous NRC reports, and there has been no attempt made
to prioritize them in Part 1. The comments from workshop panelists in Part 2 will serve to
update and extend these identified gaps.
To keep Part 1 to a reasonable length, no effort was made to include science and
technology gaps from NRC reports published before DOE-EM was established. Also, there is
no discussion of research gaps for transuranic and mixed waste, nuclear materials, and spent
nuclear fuel. These tend to be site- and waste-stream specific needs that are less important in
9
“Facilities” include built structures and the equipment contained within them.
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Part 1: Overview of Previous National Research Council Studies 9
terms of cost and schedule than the other cleanup problems. Additional information on
research gaps for these excluded wastes and materials can be found in NRC (2002c, 2003a).
High-Level Waste and Tank Cleanup
There are about 400 million liters (about 105 million gallons) of high-level radioactive
waste stored in 225 large underground tanks at the Hanford and Savannah River sites and
about 4400 cubic meters (160,000 cubic feet) of calcined high-level waste stored in bins at the
Idaho site.10,11 The Hanford Site is also storing over 1900 stainless steel capsules containing
about 130 million curies of cesium and strontium separated from high-level waste. Most of the
tank waste is a multiphase mixture of solids and liquids containing a variety of radionuclides
and hazardous chemicals. The tanks themselves are between about 40 and 65 years old, and
some have developed leaks. In 2000, DOE estimated that it would cost over $50 billion to
complete high-level waste and tank cleanup at its sites.12
Figure 3 provides a graphical illustration of DOE’s process for high-level waste cleanup
at the Savannah River Site.13 DOE plans to retrieve waste from the underground tanks the site
for treatment, immobilization, and disposal. The sludge waste (a precipitate of metal oxides
and hydroxides) will be processed and immobilized in glass for eventual disposal in a geologic
repository. The salt waste (a mixture of highly alkaline liquid and crystallized waste) will be
processed to remove cesium, strontium, and actinides, which will be immobilized in glass. The
remaining low-activity salt will be immobilized in grout and disposed of on site. The tanks,
including any residual waste, will be disposed of in place.
DOE is currently retrieving waste from tanks at Hanford and Savannah River, and the
sludge waste at Savannah River is currently being immobilized in glass. Several reports (NRC,
1999h, 2001d, 2003c,e, 2005d, 2006a) have identified opportunities to improve the technical
effectiveness and reduce the costs of high-level waste cleanup, as described below.
Waste Retrieval from Tanks
The high-level waste tanks at Hanford and Savannah River generally have small
access ports, and some tanks contain debris and (at Savannah River) cooling coils that further
inhibit access and waste retrieval. Many single-containment (also known as “single shell”)
tanks at Hanford have leaked waste into the environment, some double-containment (“double
shell”) tanks at Savannah River have leaked waste into the annulus between the tank walls,
and buried waste transfer lines and ancillary equipment (e.g., smaller tanks, valves, and
10
In addition, there is sodium-bearing liquid waste in the tanks at the Idaho Site. This waste is not
considered to be high-level waste. Its disposition is discussed in Part 2 of this report.
11
All of the high-level waste at the West Valley Site in New York has already been retrieved and
vitrified.
12
DOE. 2000. Status Report on Paths to Closure.
http://www.em.doe.gov/pdfs/StatusReportOnPathsToClosure.pdf. The cost estimate cited is
characterized in this report as a low-end estimate. DOE has not published an updated estimate since
2000.
13
A similar process is planned for the Hanford Site, except that the low-activity waste stream will be
vitrified for onsite disposal. DOE has not yet decided how it will process the solid calcine waste at the
Idaho Site. It might be dissolved and processed in a manner similar to that at Hanford and Savannah
River, or it might be processed in a solid state (NRC 1999h).
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Part 1: Overview of Previous National Research Council Studies 10
Figure 3 Simplified flow sheet for management of tank wastes at the Savannah River Site.
Low-level waste (LLW) will be disposed of onsite; high-level waste (HLW) will be stored onsite
and eventually disposed of in a geologic repository; a disposition pathway for failed melters
from the Defense Waste Processing facility (DWPF) has not yet been established; TRU =
transuranic isotopes. SOURCE: NRC (2001d).
pumps) may also contain waste. Many tanks also contain insoluble residual waste (referred to
as “heels”) that are difficult, time consuming, and costly to remove.
Residual waste retrieval from tanks and ancillary pipelines has been identified as an
important technology gap in three NRC reports (NRC 2001d, 2005d, 2006a; see also NRC
2003c). These reports recommended the development of physical and chemical cleaning
technologies to improve the effectiveness of residual waste removal in tanks, tank annuli, and
pipelines, especially technologies that reduce the risks of leakage of wastes to the
environment during the removal operations (e.g., by using little or no water to retrieve wastes).
Opportunities for expanding the use of robotics technologies for waste retrieval and tank
cleaning are discussed in NRC (2005d, 2006a).
The calcine waste at the Idaho Site is a powdered ceramic solid of various sizes and
compositions. It was transferred pneumatically to the bins for storage. DOE plans to retrieve
the calcine using the same process. However, pneumatic retrieval could be difficult if calcine
caking has occurred (e.g., from the addition of moisture to the bins or by particle sintering). A
previous NRC report (NRC, 1999h, p. 22) noted that there will probably be problems in
retrieving the calcine waste but that they could be handled. NRC (2006a) reached the same
conclusion.
Waste Characterization
High-level waste must be characterized prior to and at several points during
processing. Current processing approaches are generally expensive and labor and time
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Part 1: Overview of Previous National Research Council Studies 11
intensive. NRC (2001d) recommended that DOE develop innovative methods to achieve real-
time and, when practical, in situ physical, chemical, and radiological characterization of high-
level waste streams at all phases of processing.
Radionuclide Separations from Salt Waste
Finding reliable and robust high-throughput methods to separate cesium, strontium,
and actinides from salt wastes at Savannah River has been a significant science and
technology gap. Such separations processes will also be required at the Hanford Site and
possibly at the Idaho Site. Several NRC reports have recommended that DOE carry out
research to address this gap (NRC 1999h, 2000e, 2001d).
Immobilization of High-Activity Waste
DOE’s baseline approach for immobilizing the high-activity portion of its waste is
vitrification in borosilicate glass. While borosilicate glass can probably be used to immobilize
all of DOE’s high-level waste, there are opportunities to reduce waste volumes and costs
through the development of alternate waste forms that allow for higher waste loadings and
have less sensitivity to waste stream compositional variations (NRC 2001d; see also NRC
1996f). NRC (1999h) recommended that DOE examine a range of technical options for
immobilizing high-level waste calcine at the Idaho Site. NRC (2003a) recommended research
on the cesium and strontium capsules at Hanford to help ensure their continued safe storage,
to identify methods to convert the isotopes to stable glass or ceramic forms, and to understand
the long-term hazards of disposition options.
Tank Closure and Stabilization
DOE considers it impractical to dismantle and remove tanks after they have been
emptied because of costs and worker risks. Instead, DOE plans to characterize and stabilize
the residual waste in the tanks. NRC (2001d) identified methods for tank waste heel
characterization, especially to estimate radionuclide concentrations, as an important science
and technology gap.
Stabilization of this residual waste will be accomplished by filling the tanks with grout.
The grout serves several purposes: it encapsulates and stabilizes the residual waste, provides
structural support for the tank walls and roof, and acts as a barrier to water infiltration and
intruders. NRC (2006a) recommended focused research to improve the fundamental
understanding of tank fill materials, and also to improve DOE’s ability to tailor grout
formulations to specific tank tanks or groups of tanks.
Facility Cleanup
Over 20,000 facilities were constructed to support nuclear weapons production, testing,
and related activities, and DOE has identified over 5000 of these as surplus.14 Additional
facilities may be declared as surplus in the future. These surplus facilities include production
and test reactors; fuel and target fabrication facilities; chemical processing facilities; and
gaseous diffusion plants. Some of these facilities are the most massive reinforced concrete
14
DOE. 1997. Linking Legacies: Connecting the Cold War Nuclear Weapons Production Process to
Their Environmental Consequences. DOE/EM-0319.
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Part 1: Overview of Previous National Research Council Studies 12
structures ever built and are filled with heavily contaminated process equipment. It could take
decades for DOE to complete the cleanup of these facilities.15
DOE is following a two-phase cleanup strategy for facility cleanup: The first is to
deactivate the facility to reduce worker risks and maintenance costs. This includes shutting off
non-essential safety and security systems, flushing process lines and equipment, and
removing dangerous materials. The second is to decommission the facility. This includes
decontamination of the facility and equipment (i.e., removal of radioactive and hazardous
chemical contamination) and possibly dismantlement; the decommissioning end state will be
determined separately for each facility. DOE’s most recent low-end estimate of its deactivation
and decommissioning costs is about $10 billion (reference in footnote 12).
Facility cleanup will be technically challenging and expensive for several reasons (NRC
2001c, p. 24):
Personnel hazards in these facilities—penetrating radiation, airborne
contamination, and chemical and industrial hazards.
Number and size of facilities and bulk of concrete shielding walls.
Complex, crowded, and often retrofitted equipment arrangements.
Lack of knowledge concerning the history of operations and contamination.
Difficulty in identifying and quantifying many of the radioactive and chemical
contaminants.
Lack of decisions on the end states for many facilities.
NRC (2001c) concluded that the following DOE facilities will pose the most difficult
cleanup challenges:
Radiochemical separation facilities at Hanford and Savannah River and the
Chemical Processing Plant at Idaho.
Gaseous diffusion plants at Oak Ridge, Paducah, and Portsmouth (see NRC 1996i
for a detailed description of these facilities).
Plutonium processing plants and Hanford, Savannah River, and Los Alamos.16
Tritium processing facilities at Savannah River.
NRC (2001c) identified the following specific science and technology gaps.
Contaminant Characterization
Characterization describes the processes used to estimate the types and quantities of
contamination present in facilities and equipment that are undergoing deactivation and
decommissioning. Characterization is used to make the initial assessment of radioactive and
chemical contaminants to guide decommissioning planning. It is also used to monitor progress
in removing contamination during the decontamination process. When decontamination is
complete, characterization is again used to assess the effectiveness of decontamination and
determine the disposition pathways for wastes, surplus equipment, and possibly the facility
itself.
15
Notably, cleanup of the Rocky Flats facility was completed ahead of its original schedule with
substantial cost savings.
16
DOE has successfully decommissioned and dismantled the plutonium processing facilities at the
Rocky Flats Site.
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Part 1: Overview of Previous National Research Council Studies 13
Hundreds of thousands of individual measurements might be required during the
decontamination of a facility. Characterization as presently practiced requires workers to enter
facilities to collect samples and make measurements. This labor-intensive process exposes
workers to radiation and other hazards and is costly. In 2000, DOE estimated that
characterization consumed an estimated 15 to 25 percent of facility cleanup budgets (NRC
2001c, p. 50).
NRC (2001c) identified contaminant characterization for decommissioning as an
important science and technology gap. That report recommended that research be undertaken
to support the development of the following:
Devices for rapid characterization of low-levels of contamination (radionuclides and
Environmental Protection Agency-listed substances) on surfaces of construction
materials and equipment, including devices that can detect very-low-energy beta
emitters (e.g., tritium) and low-energy photon emitters (iodine-125).
Minimally invasive methods to characterize contaminant concentrations as a
function of depth in construction materials, especially concrete.
Instruments for remote mapping of radionuclide contamination at low levels that
can differentiate specific radionuclides, including beta and alpha emitters.
Materials Decontamination
Like characterization, decontamination is carried out at many stages of the
decommissioning process. Initially, it might be used to lower radiation levels to allow workers
to access a facility. It might also be used before equipment is disassembled or a facility is
dismantled to prevent the spread of contamination. The primary objective of decontamination
is to reduce the volume of contaminated waste that requires special handling and to allow the
bulk of waste material to be recycled or disposed of without special precautions.
Current decontamination processes are labor intensive and costly. These processes
also generate large volumes of secondary wastes and often leave behind unwanted residual
contamination. Because of its cost and hazards, cleanup contractors often choose to dispose
of contaminated equipment and construction materials rather than decontaminate and recycle
them.
NRC (2001c) identified decontamination as an important science and technology gap
and recommended specific areas of research needed to improve decontamination
technologies, including:
Research on the chemical and physical interactions between contaminants and
construction materials (e.g., steel and concrete) to gain a better understanding of
how contaminants bind to and penetrate these materials.
Research to support the development of biologically based decontamination
processes, such as bioleaching agents, biosurfactants, and biocatalysts.
Use of Robotics and Intelligent Machines for Decommissioning
DOE can probably complete its decommissioning program using current approaches,
which typically involve direct hands-on work in contaminated facilities. However, this approach
is costly and potentially hazardous to workers. The utilization of robotics and intelligent
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Part 1: Overview of Previous National Research Council Studies 14
machines in decommissioning could reduce worker exposures and might also reduce project
costs (NRC 1996i).
DOE is making limited use of some robotic technology, for example, as part of the
Glovebox Excavator Method used to demonstrate retrieval of some buried transuranic waste
at the Idaho Site (NRC 2005c, p. 43). NRC (2003a) recommended that DOE develop such
robotic technologies for retrieval and repackaging of buried waste. Such technologies could
potentially be applied to some facility cleanups.
NRC (2001c) recommended research to develop intelligent and adaptable robotic
systems that can be used for facility decommissioning. The specific need is to develop
actuators (the power component of robotic systems) that can provide real-time information on
position, velocity, and force of the robotic tool, as well as software that gives these systems a
more human-like ability to adapt to the variety of tasks that are likely to be encountered in
actual decommissioning projects. NRC (1996i) recommended that DOE undertake focused
demonstration of robotic decontamination technologies.
Long-Term Behavior of Contaminants in Construction Materials
NRC (2001c) noted that DOE must determine the final end state of a facility before the
decommissioning process can be completed. Possible end states range from complete
dismantlement of the facility to unrestricted release of an intact building for other uses. The
end state is usually established through a decision making process that is informed by risk
assessment and frequently involves negotiations with local parties. The general lack of
understanding of the long-term behavior of contaminants in construction materials like steel
and concrete may further limit end state choices. NRC (2001c) identified long-term
contaminant behavior as an important science and technology gap.
The report recommended research to provide an improved understanding of long-term
contaminant behavior in building construction materials. This includes understanding how the
physical and chemical forms of contaminants evolve with time and how they are affected by
decontamination activities. This research will help to improve knowledge of how such changes
might affect the eventual release of contaminants from building materials.
Groundwater and Soil Cleanup
Chemicals, metals, and radionuclides have been introduced into the environment at
DOE sites through accidental spills and leaks from storage tanks and waste transfer lines, and
also through intentional disposal via injection wells, disposal pits, and settling ponds. Releases
into the environment generally were not closely tracked, and many release sites were
unmarked and forgotten. Some of these sites are being rediscovered as DOE proceeds with
its cleanup program.
This environmental contamination occurs in two distinct settings:
Waste burial grounds. Waste was disposed of in pits, trenches, and auger holes at
all major DOE sites. These were unlined and frequently unmarked after closure.
There are major burial grounds at Hanford, Idaho, Oak Ridge and Savannah River,
and some of these are leaking contaminants to surface and groundwater.
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Part 1: Overview of Previous National Research Council Studies 15
Surface and subsurface contamination. Contamination of surface soils with metals,
radionuclides, and hazardous chemicals is a pervasive problem at DOE sites.
There is also extensive contamination of the subsurface with chemicals, metals,
and radionuclides at all of the major DOE sites.
Groundwater and soil are contaminated with dense non-aqueous phase liquids
(DNAPLs), toxic metals, and radionuclides. DOE (reference in footnote 12) estimates that its
sites contain some 6.4 billion cubic meters (230 billion cubic feet) of contaminated
groundwater and 40 million cubic meters (1.4 billion cubic feet) of contaminated soils and
debris. The majority of this contamination exists at the Hanford Site (1.4 billion cubic meters
[50 billion cubic feet]) and Idaho National Laboratory (4.7 billion cubic meters [170 billion cubic
feet]) (see NRC 2000a, Table 2.3), where liquid and solid wastes were dumped or buried or
pumped underground through injection wells. DOE’s most recent low-end estimate (reference
in footnote 12) for environmental restoration activities at its sites exceeds $10 billion.
The following science and technology gaps for soil and groundwater cleanup have
been identified in previous NRC reports.
Remediation Technologies
NRC reports (NRC 1994d, 1997e, 2000b) have examined the feasibility of active
remediation, such as pump-and-treat, for soil and groundwater cleanup. The overall
conclusion of these reports is that these remediation approaches have limited effectiveness.
One of these reports (NRC 1997e) recommended that additional work be undertaken to
assess the effectiveness of active remediation technologies, but these reports generally have
not recommended further research and development on remediation technologies themselves.
Several NRC reports (NRC 1994d, 1997e, 1999c, 2000b) have also examined passive
remediation technologies, for example monitored natural attenuation. Three reports (NRC
1994d, 1997e, 1999c) have recommended that additional work be undertaken on passive
remediation technologies, including reactive barriers and in situ bioremediation.
Locating and Characterizing Subsurface Contamination and Characterizing Subsurface
Properties
The challenges of locating subsurface contamination are magnified by the wide range
of contaminant types (e.g., mixtures of organic solvents, metals, and radionuclides) in the
subsurface at many DOE sites; the wide variety of geological and hydrological conditions at
these sites; and the wide range of spatial resolutions at which this contamination must be
located and characterized, from widely dispersed contamination in groundwater plumes to
small isolated hot spots in waste burial grounds. Three NRC reports (NRC 2000a, 2001f,
2002c) have identified characterization as an important science and technology gap. In
particular, these reports recommended that DOE support research to develop new or
improved capabilities to:
Characterize the physical, chemical, and biological properties, including
heterogeneity, of the subsurface, especially the unsaturated zone.
Measure contaminant migration in the subsurface.
Characterize buried waste in the subsurface, including waste container conditions.
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Modeling Contaminant Fate and Transport
Quantitative, or predictive, models are being increasingly utilized to estimate the long-
term fate of contaminants in the subsurface and to investigate the potential effectiveness of
potential remediation actions. Building such models requires a good knowledge of subsurface
characteristics and behavior of natural processes that control contaminant transport. This
assembled knowledge is referred to as a conceptual model of the subsurface. NRC (2000a)
noted that existing conceptual and predictive models have often proven ineffective for
predicting contaminant movement, especially at sites that have thick unsaturated zones or
complex subsurface characteristics (e.g., the Hanford and Idaho sites and Nevada Test Site).
NRC (2000a) identified conceptual model development as an important science and
technology gap. This report recommended basic research focused on the following topics to
improve model development capabilities:
New approaches for conceptual model development for complex subsurface
environments.
New approaches for incorporating subsurface heterogeneity into conceptual model
formulations at scales that dominate contaminant flow and transport behavior.
Development of coupled-process models that account for the physical, chemical,
and biological processes that govern contaminant fate and transport behavior.
Methods to integrate process knowledge from tests and observations into
conceptual model formulations, and methods for establishing bounds on the
accuracy of parameters and conceptual model estimates from field and
experimental data.
Waste and Contamination Containment
When DOE’s cleanup program is completed, many sites will still contain substantial
surface and near-surface contamination. These include waste burial sites, both historical sites
from weapons production activities and new sites developed specifically for onsite disposal of
waste from cleanup activities; stabilized underground tanks; abandoned facilities; and other
near-surface release sites.
DOE plans to stabilize17 and cover many of these waste sites with surface barriers, or
caps, to limit the contact of the waste with surface water. The potential need for such barriers
is enormous: there are potentially hundreds of near-surface sites (burial grounds, closed
underground tanks, and liquid discharge sites) that will need to be covered with barriers to limit
surface water infiltration. These sites occur in both arid and humid environments. The barriers
installed on these sites must function for many generations.
The current emphasis in barrier deployment at DOE sites is on low-permeability
engineered caps that are constructed of multiple layers of engineered and natural materials for
stability, intrusion prevention (especially by animals), and to limit infiltration. Subsurface
barriers are not yet in wide use at DOE sites (except in engineered landfill facilities) but may
17
The term “stabilize” has at least two meanings. It describes methods that are used to treat a waste to
make it less susceptible to leaching, for example, by producing a chemically resistant waste form. It also
describes methods for increasing the structural integrity of a closure system, for example, by in situ
grouting or compaction, to improve its long-term performance.
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receive increased attention in the future as DOE completes cleanup of tanks, burial sites, and
other waste sites. These could include horizontal or vertical layers of clay, grout, or frozen or
fused soil. DOE has experimented with reactive barriers to treat or retard contaminants in
contaminated groundwater. Some of these could in principle also be used for waste
containment.
Although there has been an increasing emphasis on and acceptance of waste
containment and stabilization as “final” corrective actions at DOE sites, both by DOE
management and regulatory agencies, there is relatively little understanding of the long-term
performance of containment and stabilization systems. Moreover, there is a general absence
of robust and cost-effective methods to validate that such systems are installed properly or
that they can provide effective long-term protection.
Several NRC studies have called for research to develop improved containment and
stabilization systems and to assess their effectiveness (NRC 1996c, 1999c, 2000a, 2001f; see
also NRC 1997b, 2000d, 2005c). The specific science and technology gaps that underpin the
development of these improved technologies include the following (NRC 2000a):
Better understanding of the mechanisms and kinetics of chemically and biologically
mediated reactions that can be exploited in containment systems. For example,
better understanding of reactions that can extend the use of reactive barriers to a
greater range of contaminant types found at DOE sites or that can be used to
understand the long-term reversibility of chemical and biological stabilization
methods.
The physical, chemical, and biological reactions that occur among contaminants,
soils, and barrier components so that more compatible and durable materials for
containment and stabilization systems can be developed.
The fluid transport behavior in conventional barrier systems to support the design of
more effective infiltration barrier systems.
The development of methods for assessing the long-term durability of containment
systems.
Containment Monitoring
Monitoring, defined broadly, refers to methods to used to plan for and demonstrate the
effectiveness of any remedial action, including waste containment. For example, monitoring is
used to collect information to support the development of conceptual and predictive models of
subsurface and contaminant behavior. It is also used to demonstrate the effectiveness of
efforts to remove, treat, or especially to contain contamination or to gain regulatory approval
for such actions.
Monitoring will be especially important to assess the long-term performance of the
containment systems that will likely be installed across DOE sites. Such monitoring could in
principle be used to assess the performance of containment barriers and provide an early
warning of contaminant releases. NRC (2006a, p. 84-90) identified the characteristics of a
good monitoring system; the report also noted that DOE sites have not yet developed plans for
post-closure monitoring of underground waste tank closures. This report also recommended
that DOE begin to plan now for post closure monitoring so that provisions can be built into
closure plans and designs.
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Many of DOE’s sites will not be cleaned-up sufficiently for unrestricted release after the
cleanup program is completed (see NRC, 2000d). Those sites (or portions of sites) that cannot
be released will be transferred to DOE’s Office of Legacy Management once cleanup activities
have ended; this office will be responsible for long-term site monitoring and maintenance.
DOE’s low end estimate (reference in footnote 12) for conducting these long-term stewardship
activities is almost $10 billion through 2070.
NRC reports have identified post closure monitoring as an important science and
technology gap for tank closure (NRC 2001d, 2006a). NRC (2001d) recommended the
development of in situ and non-invasive methods to monitor the near field environment within
and surrounding the tanks to detect the early degradation of barriers or the movement of
contaminants.
More generally, NRC reports (e,g, NRC 2000a; 2001f, 2002c, 2005c) have
recommended research to develop the following:
Monitoring methods that can provide measurements of current conditions and
detect changes in system behaviors, especially in the unsaturated zone and within
and beneath caps and barriers.
Methods to monitor fluid and gaseous fluxes through the unsaturated zone and
within and beneath caps and barriers, and for differentiating diurnal and seasonal
changes from longer-term changes.
Validation processes for modeling of containment systems, including determination
of the key measurements that are required to validate models, the spatial and
temporal resolutions at which such measurements must be obtained, and the
extent to which surrogate data (e.g., data from lab-scale testing facilities) can be
used in model validation efforts.
Remote sensing technology to replace point-to-point practices for sampling and
analyzing groundwater.
Such monitoring methods have potentially important application to engineered waste disposal
facilities like WIPP to help validate their long-term performance (see NRC 2000c, 2002c).
CLOSING THOUGHTS: IMPORTANCE OF SCIENCE AND
TECHNOLOGY FOR ENVIRONMENTAL CLEANUP
A recurring theme from many NRC reports published since the Environmental
Management Program was created in 1989 is the importance of science and technology
development for DOE’s site cleanup mission. This is perhaps best expressed in NRC (1995c,
p. 114):
Science and technology play a key role in virtually all the activities of EM [Office
of Environmental Management]. They help to determine priorities for site
cleanup by providing the basis for sound risk assessments, provide the tools for
achieving remediation goals, and provide the scientific rationale that reassures
stakeholders that the priorities and actions of the Department are in their best
interests.
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The identification of science and technology as a core continuing need in the cleanup
program was identified in the first NRC review of DOE’s plans for waste management and
environmental restoration (NRC 1989a, p. 2):
[DOE’s five-year waste management and environmental restoration] plan
should make explicit the need and intent to develop a balanced program of
basic and applied research, development, and training that embraces the entire
thirty-year span of its cleanup effort, not just the first five years.
Other NRC reports have highlighted the importance of science and technology
development for improving cleanup capabilities; understanding and reducing cleanup risks;
and reducing cleanup costs and schedules. These reports have generally taken a long-term
(decadal or longer) view of science and technology development and have encouraged DOE
not to ignore longer-term needs in the rush to meet short-term schedules. The following
excerpts illustrate many of these points:
In some circumstances, technologies and processes for safe and efficient
remediation or waste minimization do not exist. In other cases, the development
of a new technology and processes might substantially reduce the costs of, or
risks associated with, remediation and waste management. An effective
technology development program focused on such opportunities is an essential
element of an overall strategy for reducing the cost and speeding the pace of
the Environmental Management Program. (NRC 1995c, p. 6-7)
Many of EM’s cleanup problems cannot be solved or even managed efficiently
with current technologies, in part owing to their tremendous size and scope. …
[A] basic research program focused on EM’s most difficult clean-up problems
may have a significant long-term impact on the clean-up mission. … Simply put,
new technologies are required to deal with EM’s most difficult problems, and
new technologies demand new science. (NRC 1997c, p. 1-2)
DOE’s attempts to clean up contaminated groundwater and soil have been
limited in part by technological difficulties. … Because of such limitations, new
technologies are needed to enable DOE to achieve remediation requirements
for groundwater and soil at a reasonable cost. (NRC 1999c, p. 3)
[W]hile current D&D [deactivation and decommissioning] technologies probably
can be made to work in the D&D of [DOE] facilities, there are opportunities to
do the job more safely and effectively by developing and using new
technologies. … There are strong safety and economic incentives for
developing and using innovative D&D technologies that may be achieved
through scientific research. The long time frame for completing D&D (50 years
or more allows) for substantive research to be completed and applied. (NRC
2001c, p. 2-3)
[T]he closing of larger DOE sites will require decades. Problems that are not
foreseen or appreciated today are likely to be encountered in buried waste
retrievals. … Buried waste retrieval and monitoring of disposal facilities provide
opportunities for the long-term, breakthrough research envisioned by Congress
[when it created the EMSP], and these opportunities should not be overlooked
in DOE’s rush to meet short term needs. (NRC 2002c, p.9)
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Ten years or more is a realistic time frame for development, demonstration, and
deployment of truly innovative technologies. Such long-term efforts should
target both site-specific and complex-wide problems that are intractable or very
difficult (e.g., expensive) with current technologies. (NRC 1999g, p. 21)
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Representative terms from entire chapter:
savannah river
