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TABLE OF CONTENTS 

Acronyms and Initialisms............................................................................................................ iii

Executive Summary ...................................................................................................................... 1

1. Introduction ............................................................................................................................. 9

1.1 Overview .......................................................................................................................... 9

1.2 Background .................................................................................................................... 10

1.3 Breakout Sessions .......................................................................................................... 12

2. Plenary ................................................................................................................................... 15

2.1 Keynote Address ............................................................................................................ 15

2.2 DOE Office Missions ..................................................................................................... 16

2.2.1 Office of Nuclear Energy ................................................................................................ 16

2.2.2 Office of Environmental Management............................................................................ 16

2.2.3 National Nuclear Security Administration...................................................................... 17

2.3 Nuclear Separations Program Overviews ...................................................................... 18

2.3.1 Office of Nuclear Energy ................................................................................................ 18

2.3.2 Office of Environmental Management............................................................................ 18

2.3.3 National Nuclear Security Administration...................................................................... 18

2.4 Closing Remarks ............................................................................................................ 19

3. Breakout Sessions.................................................................................................................. 21

3.1 Chemistry and Speciation of the Actinides and Key Fission Products (Cs, Tc, I) ......... 21

3.1.1 Background Information ................................................................................................. 21

3.1.2 Grand Challenges............................................................................................................ 22

3.1.3 Proposed Solutions.......................................................................................................... 23

3.2 Design of Molecules and Materials with Selective Separation Properties ..................... 25

3.2.1 Background Information ................................................................................................. 25

3.2.2 Grand Challenges (including identified capability gaps)................................................ 26

3.2.3 Proposed Solutions.......................................................................................................... 29

3.3 Scale-up of Separation Processes from Bench-Top to Plant .......................................... 31

3.3.1 Background Information ................................................................................................. 31

3.3.2 Grand Challenges............................................................................................................ 32

3.3.3 Proposed Solutions.......................................................................................................... 34

3.3.4 Overall Findings and Recommendations ........................................................................ 37

3.4 Interface Issues between Separations and Waste Forms/Fuel Fabrication .................... 38

3.4.1 Background Information.................................................................................................... 38

3.4.2 Grand Challenges .............................................................................................................. 39

3.4.3 Proposed Solutions............................................................................................................ 39
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4. Crosscutting Results ............................................................................................................. 43

4.1 Overarching Themes ...................................................................................................... 43

4.1.1 Summary-Level Program Office Needs.......................................................................... 43

4.1.2 Need for a Comprehensive Vision of and Approach to Separations RD&D—Informed 

by Modeling and Simulation ................................................................................................. 44

4.1.3 Need for Ready Access to Appropriately Scaled and Capable Facilities........................ 45

4.1.4 The Need for Contributions from a Broad Spectrum of Disciplines............................... 45

4.2 Shared Disciplines/Areas of Interest .............................................................................. 46

4.2.1 Computational Modeling and Simulation ...................................................................... 46

4.2.2 Experimental Validation ................................................................................................. 46

4.2.3 Radiochemical Diversity................................................................................................. 46

4.2.4 Challenging Environments.............................................................................................. 46

4.2.5 National Policy, Regulatory Requirements and Other Considerations........................... 47

4.2.6 Nonproliferation.............................................................................................................. 47

4.3 Advantages of a Center of Knowledge for Nuclear Separations Technologies ............. 47

4.3.1 Definition of RD&D Needs............................................................................................... 47

4.3.2 Coordination and Integration of Separations RD&D ........................................................ 48

4.3.3 Establishment of a Scientific User Facility for Separations RD&D.................................. 48

References .................................................................................................................................... 54

Appendix A. Breakout Session Report: Chemistry and Speciation of the Actinides 

and Key Fission Products

Appendix B. Breakout Session Report: Design of Molecules and Materials with 

Selective Separation Properties

Appendix C. Breakout Session Report: Scale-up of Separation Processes from 

Bench-Top to Plant

Appendix D. Breakout Session Report: Interface Issues between Separations and 

Waste Forms/Fuel Fabrication

Appendix E. Workshop Sponsors

Appendix F. Agenda

Appendix G. Participant List
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ACRONYMS AND INITIALISMS 

μm Micrometer(s)

μM Micromolar

3D Three-Dimensional 

Al Aluminum

Am Americium

AMEX Amine Extraction

ASTM ASTM International, formerly 

the American Society for 

Testing and Materials

ATR Advanced Test Reactor 

Be Beryllium

BRC Blue Ribbon Commission on 

America’s Nuclear Future

BTP Bis-Triazinyl-Pyridine

C Carbon 

Ca Calcium

CaDTPA Calcium 

Diethylenetriaminepentaacetate 

Complex

CEA Commissariat à l’energie 

atomique 

CFD Computational Fluid 

Dynamics 

CFR Code of Federal Regulations 

Cl Chlorine 

Cm Curium 

Co Cobalt 

CRESP Consortium for Risk 

Evaluation with Stakeholder 

Participation

Cs Cesium

CSEX Cesium Extraction

CSSX Caustic-Side Solvent 

Extraction

CST Crystalline Silicotitanate (ion 

exchange) 

DoD Department of Defense

DOE Department of Energy 

DTPA Diethylenetriaminepentaacetic

Acid

DWPF Defense Waste Processing 

Facility

EM Office of Environmental 

Management

FCR&D Fuel Cycle Research and 

Development (program)

FCT Fuel Cycle Technologies

FP Fission Product 

GDP Gaseous Diffusion Plant 

GPO Government Printing Office 

GTRI Global Threat Reduction 

Initiative

H Hydrogen 

HEU Highly Enriched Uranium 

HLW High-Level Waste

HM Heavy Metal

HOPO Hydroxypyridinonate 

I Iodine 

IAEA International Atomic Energy 

Agency 

IL Ionic Liquid

In Indium 

Ir Iridium

ITP In-Tank Precipitation Process

IX Ion Exchange 

kg Kilogram(s)

Kr Krypton 

LAW Low-Activity Waste

LEU Low-Enriched Uranium 

LLW Low-Level Waste

LWR Light Water Reactor
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M Molar

MD Molecular Dynamics 

mm Millimeter(s)

mM Millimolar

Mo Molybdenum 

MOX Mixed Oxide 

Na Sodium 

NA-10 Defense Programs (NNSA)

NA-20 Office of Defense Nuclear 

Nonproliferation 

NAS National Academy of Sciences

NE Office of Nuclear Energy

NIH National Institutes of Health

NIS Office of Nonproliferation and 

International Security

nm Nanometer(s)

NNSA National Nuclear Security 

Administration

Np Neptunium 

NRC Nuclear Regulatory 

Commission

NSF National Science Foundation 

NSUF National Scientific User 

Facility

O Oxygen 

PJM Pulse Jet Mixers

Pd Palladium

pM Picomolar

Po Polonium 

POM Polyoxometalate 

Pu Plutonium 

PUREX Plutonium/Uranium Refining 

by Extraction

QSAR Quantitative Structure-Activity 

Relationship

Ra Radium 

R&D Research and Development 

RD&D Research, Development and 

Demonstration 

RDD Radiological Dispersal Device

(e.g., dirty bomb) 

REDOX Oxidation Reduction 

S Sulfur 

SC Office of Science

SCN- Thiocyanate 

SNF Spent Nuclear Fuel (as used in 

this report, equivalent to used 

nuclear fuel) 

Sr Strontium

SREX Strontium Extraction

SS&T Separation Science and 

Technology 

SX Solvent Extraction

TALSPEAK Trivalent Actinide–Lanthanide 

Separation by Phosphorus 

Reagent Extraction from 

Aqueous Complexes 

TBP Tri-N-Butyl Phosphate

Tc Technetium 

THORP Thermal Oxide Reprocessing 

Plant 

TRA Technology Readiness 

Assessment

TRL Technology Readiness Level

TRU Transuranic

TRUEX Transuranic Element 

Extraction

U Uranium 

UNF Used Nuclear Fuel

UREX+ Uranium Extraction Plus

WIPP Waste Isolation Pilot Plant

WTP Waste Treatment Plant

Xe Xenon 

Y Yttrium

Zr Zirconium 
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Figure 1. The workshop supported 

Goal 3 of the DOE Strategic Plan.

EXECUTIVE SUMMARY 

The Department of Energy (DOE) sponsored a workshop on nuclear separations technologies in 

Bethesda, Maryland, on July 27 and 28, 2011, to (1) identify common needs and potential 

requirements in separations technologies and opportunities for program partnerships, and 

(2) evaluate the need for a DOE nuclear separations center of knowledge to improve crossprogram collaboration in separations technology. The workshop supported Goal 3 of the DOE 

Strategic Plan1

The workshop included four breakout sessions with 

program-related topical areas covering a broad range of 

separations activities. The topics also span the range of 

DOE-defined Technical Readiness Levels (TRLs)

 to enhance nuclear security through defense, nonproliferation, and environmental 

management. The Office of Environmental Management 

(EM), Office of Nuclear Energy (NE), and National 

Nuclear Security Administration (NNSA) jointly 

sponsored the workshop. The Office of Science (SC), 

which performs fundamental research in relevant areas, 

also participated. The workshop attracted 133 attendees

from national laboratories, academia, industry, DOE 

oversight and advisory organizations, sponsoring offices 

and the international community. 

2

• Chemistry and Speciation of the Actinides and Key Fission Products (Cs, Tc, I)

where the lower readiness levels are less mature 

technology (more basic research and development 

[R&D]) and the higher numbers are more mature (more 

deployable) technology (see Figure 2). The breakout 

session topics were as follows:

• Design of Molecules and Materials with Selective Separation Properties

• Scale-up of Separation Processes from Bench-Top to Plant 

• Interface Synergies between Separations, Waste Management, and Fuel Fabrication

Role of Nuclear Separations 

Within DOE and its predecessor agencies, there has been a continuing need for new nuclear 

separations technologies over the past 70 years. DOE has multiple responsibilities that require 

the ability to separate nuclear materials for their direct use, future reuse or disposition: 

 

1

 U.S. Department of Energy. Strategic Plan. Washington: GPO, May 2011. 2 ---. DOE Guide 413.3-4A, Technology Readiness Assessment Guide, September 15, 2011. 
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NUCLEAR SEPARATIONS TECHNOLOGIES WORKSHOP REPORT November 7, 2011

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DOE nuclear separations 

challenges include:

• Meeting our national needs

• Sustaining specialized 

capabilities/facilities

• Training and developing the 

workforce of the future 

(1) nuclear weapons manufacture and maintenance, (2) technical aspects of nuclear 

nonproliferation, (3) cleanup of legacy defense-related nuclear facilities, (4) disposition of excess 

weapons plutonium, (5) research on advanced commercial fuel cycles, and (6) treatment and 

disposal of radioactive wastes 

including spent nuclear fuel 

(SNF). Of special interest in 

nuclear separations technologies 

are those related to capturing 

elements such as uranium and 

plutonium, other actinides such 

as americium, and selected 

fission products (FPs) such as 

technetium, iodine, and cesium.

Significant advances in 

separations technologies can be 

derived from industrial 

applications, as separations technologies are the backbone of the pharmaceutical, chemical, metal 

production, and fossil fuel industries. However, research, development and demonstration 

(RD&D) of nuclear separations technologies faces different challenges, such as the following: 

(1) In the absence of a large commercial domestic market in nuclear separations, responsibility 

for developing these technologies falls to DOE. DOE should be capable of taking the 

necessary steps in behalf of our national interests to assure the technical capabilities exist to 

meet current and future nuclear separations needs.

(2) Nuclear separations RD&D requires highly specialized facilities, as many of the important 

species are radioactive and/or entail extensive safeguards and security. Preserving or 

developing specialized facilities for RD&D, 

and maintaining internal centers of 

excellence, will ensure required capabilities 

are available. 

(3) The U.S. reservoir of trained professionals

outside the DOE complex is small. 

Developing the next generation of young 

professionals to replace retiring staff is 

essential to maintain U.S. technical expertise 

in this important technology. 

Opportunities for Program Partnerships 

Nuclear separations R&D addresses needs and requirements that cut across multiple DOE 

offices, as they share a common interest in the chemistries of actinides and FPs. For example, 

Figure 2. The workshop included four breakout 

sessions with program-related topical areas. 
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NUCLEAR SEPARATIONS TECHNOLOGIES WORKSHOP REPORT November 7, 2011

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understanding radionuclides’ transport in the environment and their subsequent recovery is 

normally considered part of the EM mission; however, NNSA needs similar chemistry to detect 

nuclear weapons activities, as does NE to model transport of radioactivity from disposal sites—

including geological repositories. 

Scientific breakthroughs have been successfully transferred from one DOE program to another; 

examples include the well-known transuranic element extraction (TRUEX) process for actinide 

separations and, for cesium removal from tank waste, the caustic-side solvent extraction (CSSX) 

and crystalline silicotitanate (CST) ion exchange processes. All three processes were based on 

scientific insights developed through DOE 

basic science programs, and the methods were 

applied in environmental cleanup of the 

weapons complex and development of 

advanced fuel cycle technology. 

In order to capitalize on opportunities for 

program partnerships, breakout session 

participants identified common needs and 

potential requirements in nuclear separations 

technologies. Recognizing the different mission 

requirements of the sponsoring programs, 

participants were able to identify areas with 

common uses and related applications, as 

discussed below. 

Chemistry and Speciation of the Actinides and Key Fission Products (Cs, Tc, I)

Understanding the underlying physical and chemical properties of given materials is the basis for 

all separations. In addition, the area of nuclear separations involves the need to understand how 

these properties change in the presence of a radioactive environment. Also of great importance is

understanding the properties of actinides which, relative to most other elements, have complex 

chemistries that are less well explored and more difficult to model.

Of benefit to the sponsoring programs is understanding chemical properties, such as oxidation 

states and coordination environments, which can be adjusted to optimize partitioning and 

separation in multi-radionuclide systems. Better understanding actinide and FP chemistry will 

impact a variety of challenges facing DOE, such as monitoring actinides during processing and 

technetium volatilization in waste treatment. To help predict process performance and behavior, 

understanding the fundamental effects of radiolysis on solvents, ligands and other separations 

molecules will enable development of advanced models of radiation resistance, decomposition, 

and formation of radicals. In addition, advanced tools are needed to predict the molecular 

structure of actinides and FPs in extreme systems, ranging from ultra-low-concentration 

contaminants to complex environments at high temperatures. 

Figure 3. The CSSX ion exchange process, 

an innovation based on new molecules, 

resulted from cooperation across DOE 

offices. 
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Design of molecules with selective nuclear separations capability 

The development of nuclear separations technologies has historically involved the empirical 

screening of chemical compounds for their ability to perform separations. The last decade has 

seen a maturity in the technology to synthesize molecules and materials for a specific function. 

Improved predictive science that couples experimentation with modeling and theory allows 

researchers to design molecules and materials that precisely target particular nuclear separations 

requirements. Breakthroughs of this type require a full-cycle, systematic approach by teams with 

diverse capabilities from molecular design to synthesis to chemical engineering (see Figure 4). 

Advancing this design approach supports multiple DOE separations needs. 

While many nuclear separations processes are project-specific, others have applicability across 

the Department, such as selective co-separation of fissile and fertile materials. Current 

commercial SNF recycling processes allow for the separation of pure plutonium. Customdesigned molecules could make possible 

the co-separation of given mixtures of 

actinides while making production of pure 

plutonium difficult, changing the diversion 

risks encountered in these processes. Such 

separation systems could also be more 

economical because the product is suitable 

for direct fuel fabrication. In addition, to 

address nuclear accidents and radiological 

terrorist incidents more effectively, there is 

a need for the removal of radionuclides 

from a variety of host matrices, such as 

soils, concrete, and the human body. 

Scale-up to industrial capabilities

The history of transitioning nuclear separations processes from the laboratory to an industrial 

scale includes a number of failures and setbacks due to the unforecasted effects of radiation. 

Radiation affects the behavior of separations agents with time. Equally important, modifying a 

nuclear separations facility after it has begun operations requires time and money an order of 

magnitude greater than for a comparable non-nuclear chemical plant. Therefore, it is essential to 

recognize, and account for, the hazards throughout the process when scaling up nuclear 

separations facilities operated under high levels of radiation. All of the sponsoring programs will 

face these hazards when developing technology from the bench scale to the industrial scale. In 

order to ensure certainty in taking a technology from bench to industrial scale, programs will 

have to analyze and address the technology risks associated with each step in the scale-up 

process. An effective risk analysis calls for understanding the key physical and chemical 

properties affected, and the appropriate number of scale-up steps necessary, in order to properly 

consider risk, cost, and expected performance. 

Figure 4. Recent separations research, such as 

computer-aided ligand development, is largely 

aimed at design of molecules and materials and 

requires teams with diverse capabilities. 

 
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Figure 5: Faster scale-up is possible 

with advances in modeling, such as 

this computer simulation of a solvent 

extraction separations process using 

a centrifugal contactor. 

There is a need to develop methods to increase 

confidence when scaling up nuclear separations 

technology. Fundamental understanding of science 

coupled with advanced computational capabilities (see 

Figure 5) may increase the efficiency of scale-up testing, 

providing methods that supplement the traditional multistep process (e.g., 1/1000 scale to 1/100 scale, 1/100 

scale to 1/10 scale, etc.) to reduce risk, lower costs, and 

increase certainty. Collaboration with foreign partners 

with more recent experience in scale-up may also

provide useful input and insight. Ultimately, reducing 

program risk in process scale-up will provide tangible 

benefits to the sponsoring programs. 

Interface synergies between nuclear separations, waste 

management, and fuel fabrication 

Whether separating the contents of a high-level waste (HLW) tank for stabilization and 

disposition or separating SNF for fuel material recycling, the interface between the different 

processes and the waste forms that they produce is a critical consideration when reducing costs 

and optimizing the overall operation. Efficiencies in one area may lead to complications in other 

areas. A systems analysis approach is therefore essential to guide R&D. 

Tools that capture functions and requirements of a process must be developed to improve synergies 

between the separations process and follow-on processes. For example, developing a separations 

technology commonly involves chemicals that function as complexing agents, such as iron. If 

subsequent steps in this process entail using borosilicate glass for waste disposal, the presence of 

iron will limit the ability to maximize waste loading, reducing efficiency and ultimately increasing 

the overall costs. Understanding the impact that each step has on the overall process and capturing 

interface synergies will result in improved overall performance and reduced costs. 

Advantages of a Nuclear Separations Center of Knowledge 

The participants of the workshop acknowledged that the focus of separations research has shifted

from a primary mission involving weapons to supporting multiple DOE offices with potentially 

competing priorities. Scattering DOE resources among various R&D paths can dilute DOE’s 

potential to achieve its missions. Expanded and multiple emphases also make it more difficult for 

DOE to maintain a skilled workforce. Since the cold war, the NNSA production complex has 

downsized as missions have evolved, resulting in an aging workforce that is declining in 

numbers. In addition, it is more expensive to maintain facilities with radiological capabilities to 

support multiple missions.
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A DOE center of knowledge for nuclear separations can:

• Improve coordination across DOE programs

• Maximize the use of existing capabilities and facilities 

to best use available funding and resources

• Facilitate training researchers of the future

Establishing a center of knowledge 

for nuclear separations can initially 

be a virtual network connecting 

common work between programs

To address these needs, a center of knowledge is proposed. Such an entity could assist DOE in 

taking full advantage of the synergies between programs, as well as fully exploiting resources—

including technical expertise and experimental capabilities—across national laboratories, 

academia, and industry. In addition, establishing a center could contribute to developing a future 

skilled technical workforce. Such a center may be created initially as a coordinated virtual 

network of existing national assets, then evolve over time as experience informs a changing 

portfolio of functions and capabilities. Given the nature of this technology and the potential for 

multinational interactions, the center should account for international safeguards agreements and 

export control requirements. 

Benefit

For DOE, going from one initial primary goal (weapons production) to multiple research, 

energy-production, and cleanup goals has resulted in a multi-dimensional set of technology 

needs. Those needs are defined by various offices and documented in dozens of different reports. 

There is no single big picture of needs, but there are significant overlaps representing important 

opportunities for research with broad impacts. Therefore, coordinated efforts can help weave 

seemingly disparate—even competing—needs into a coherent effort. Short-, medium-, and longterm needs and interface requirements should be concisely defined and assembled in a way that 

allows researchers and program managers to match needs with capabilities, identify solutions, 

enable synergies, and share changes as requirements evolve. 

A DOE center of knowledge for nuclear 

separations technologies can: 

(1) Improve coordination across 

multiple DOE programs, facilitating 

collaboration and technology 

synergies. 

(2) Maximize the use of existing capabilities and facilities to ensure efficient and effective use of 

available funding and resources. 

(3) Facilitate coordinated plans for developing and training the needed researchers and operators 

of the future to ensure the United States maintains a knowledge edge in expertise and 

experience.
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Establishing a center of knowledge for nuclear separations technology and networking user 

facilities for R&D purposes will require detailed proposals and an implementation plan, as 

determined by the sponsoring programs. 

Next Steps 

The Nuclear Separations Technologies Workshop established a foundation of cooperation in this 

important area between EM, NE, NNSA and SC. More discussions and broad participation will 

be needed to advance the concepts and ideas introduced during the workshop and to ensure 

inclusive research scope. 

Next steps resulting 

from this workshop are 

to be broken into three 

phases: 

(1) Startup

(2) Growth

(3) Sustainable 

Program 

The Startup phase 

includes preparation of 

a nuclear separations 

roadmap that would 

discuss technical issues, 

programs, and 

collaborations in the 

areas of separations necessary to achieve the goals of DOE program offices. Specifically, the 

nuclear separations roadmap will: 

(1) Establish the plans and strategies necessary to develop the cooperation initiated at this 

workshop into a sustainable collaboration between the sponsoring programs, including the 

estimated scope, schedule, and costs associated with the Growth and Sustainable Program 

phases.

(2) Support the coordinated DOE response to the Blue Ribbon Commission on America’s 

Nuclear Future (BRC) recommendations, expected in January 2012, as they relate to 

nuclear separations technologies. 

(3) Refine the concept of a nuclear separations center of knowledge that responds to DOE 

needs, improves program partnerships, and supports the effective use of available funding 

and resources.

Figure 6. The workshop found that partnership opportunities 

exist for all separations-related technologies.
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A nuclear separations center of knowledge may be a candidate for DOE's portfolio of new 

research efforts, such as the Innovation Hubs. A center would provide a mechanism to 

integrate multiple phases of nuclear separations RD&D across DOE offices and address the 

boundaries between science, engineering, and technology development.
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1. INTRODUCTION 

1.1 Overview 

On July 27 and 28, 2011, DOE hosted a workshop to bring together scientists and engineers from 

the national laboratories, academia, and industry to set a course for moving from where we are to 

where we want to be in nuclear separations technologies. The technical goals of the workshop 

were to determine the path necessary to address the following technical challenges within the 

next three to five years:

• Enable the responsible deployment of civilian nuclear power and fuel cycle management 

by developing used fuel recycling technologies that are alternatives to plutonium/ 

uranium refining by extraction (PUREX) and that support waste minimization. 

• Support environmental remediation of our legacy and active sites by developing nextgeneration waste treatment technologies that increase performance and reduce cost.

• Reduce global threats from nuclear materials by supporting technologies that reduce the 

risks of proliferation, such as alternative methods of medical isotope production that do 

not use highly enriched uranium (HEU). 

The workshop presented two overarching programmatic objectives that support optimizing the 

path to resolve these technical challenges: 

• Identify common needs and potential requirements in nuclear separations technology and 

opportunities for program partnerships. 

• Evaluate the need for a DOE nuclear separations center of knowledge. 

The workshop directly supported Goal 3 of DOE’s recently revised Strategic Plan: Enhance 

nuclear security through defense, nonproliferation, and environmental efforts.3 Three DOE 

organizations jointly hosted the workshop: EM, NE, and NNSA. SC, which establishes basic 

research needs and funds fundamental science programs in relevant areas of actinide separations, 

also played an active collaborative role. More about these workshop sponsors can be found in 

Appendix E. 

To ensure an appropriate mix of subject matter experts, participants were solicited through two 

methods: 1) DOE reached out to specific individuals to serve in appropriate breakout sessions, 

and 2) a broader invitation was issued encouraging interested parties to attend (contingent upon 

DOE approval). The workshop attracted 133 attendees including representatives from 8 national 

laboratories and 22 academic institutions. Also represented were industry partners, the Nuclear 

Energy Advisory Committee’s Subcommittee for Fuel Cycle Research and Development, the 

 

3 U.S. Department of Energy, Strategic Plan. Washington: GPO, May 2011. 
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Nuclear Waste Technical Review Board, and three international organizations: the French 

Embassy, the French Commissariat à l’energie atomique (CEA), and the U.K.’s National Nuclear 

Laboratory. 

The two-day workshop began with an introductory plenary session, summarized in Section 2 of 

this report, in which executives presented information about their respective organizations’ 

backgrounds and viewpoints regarding separations issues. Workshop participants then divided 

into four breakout sessions organized to address specific technical challenges in the following 

areas:

• Chemistry and Speciation of the Actinides and Key Fission Products (Cs, Tc, I)

• Design of Molecules and Materials with Selective Separation Properties

• Scale-up of Separation Processes from Bench-Top to Plant 

• Interface Synergies between Separations, Waste Management, and Fuel Fabrication

The workshop concluded with a summary plenary session in which each program breakout group 

reported session outcomes, including analyses and recommendations. The results of the breakout 

sessions are summarized in Section 3 of this report, with full session reports included in 

Appendices A through D. Appendices to this report also provide the workshop agenda and a 

complete participant list.

To prepare participants, advance reading materials were posted to the workshop website. The 

general reading list included agency plans and roadmaps, a report from the Massachusetts 

Institute of Technology on the nuclear fuel cycle, an EM document on separations technology 

challenges, and the executive summary from the Nuclear Regulatory Commission (NRC) white 

paper on SNF recycle facilities (NUREG 1909). These and other references directly related to 

the subject of RD&D associated with nuclear separations are found at the end of this report. 

1.2 Background 

As DOE’s Strategic Plan articulates, the growing global demand for energy, coupled with 

increasing concerns about climate change, has accelerated deployment of nuclear power plants 

and fuel cycle facilities despite recent events overseas. Meeting this need, however, requires that 

a number of technological hurdles associated with the nuclear fuel cycle be addressed. Basic and 

applied research by the Department’s predecessor agencies in the mid-20th century laid the 

foundation for modern nuclear power and fuel cycle technologies. A key element of nuclear fuel 

cycles is the use of separations technologies such as used fuel recycling, material stabilization, 

waste treatment, and isotope development and production. The need to develop these nuclear 

separations technologies cuts across a number of important Department organizations: EM, NE, 

NNSA, and SC. Therefore, these offices joined forces to host a workshop to set a course for 

moving from where we are to where we want to be in nuclear separations technologies. 
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The need for advances in this area is increasingly pressing. As EM notes in a recent report,4 fifty 

years of nuclear weapons production, combined with activities supporting nuclear energy, have 

already left the United States with millions of gallons of highly radioactive waste, thousands of 

tons of SNF and special nuclear material, and enormous quantities of contaminated soil, water, 

and facilities. The cleanup effort currently covers over a million acres in thirteen states. The EM 

cleanup program, which has already been under way for twenty years, estimates several decades 

for completion. As energy demand grows, nuclear power will expand; and as nuclear power 

expands, SNF and HLW inventories will grow. The Nuclear Waste Policy Act of 1982 gave the 

U.S. government the mission to safely manage the SNF and HLW from these nuclear power 

plants. The responsibilities under this mission are science- and technology-intensive; several 

recent efforts have identified ongoing technical challenges.

5,6

RD&D of sustainable nuclear fuel cycles and waste management activities is critical both to 

address existing inventories of SNF and HLW and to ensure a continued role for nuclear energy 

in the nation’s clean energy portfolio. NE is currently supporting RD&D of three fuel cycles: 

once-through, modified open, and closed. For the current fleet of nuclear reactors, a oncethrough or “open” nuclear fuel cycle is employed. Used fuel from commercial light water 

reactors (LWRs) in the United States is currently stored at the reactor sites. The Nuclear Waste 

Disposal Act of 1987 mandated that the disposition for this used fuel was direct disposal in a 

geologic repository, which would complete the once-through cycle. Although minimal

separations technologies are required, this cycle entails the greatest need to manage SNF and 

HLW. A modified open cycle entails some separations and fuel processing, reusing components 

of the initial discharged fuel to utilize more energy from the same amount of nuclear material 

while reducing the quantity of long-lived radiotoxic elements. DOE is also evaluating prospects 

for a cost-effective sustainable closed fuel cycle that eliminates much of the HLW, reclaiming 

the energy from used fuel by recycling the long-lived actinide elements continually through a 

nuclear reactor. In a full recycle (closed cycle) system, only waste products require disposal, not 

used fuel. A closed cycle would require extensive use of separations technologies. The present 

NE approach to RD&D has been described in a recent report to Congress.7 

NNSA also has interest in separations to support its mission areas of nuclear nonproliferation and 

safeguards and security and for ongoing weapons complex operations. The NE RD&D roadmap8

 

4 U.S. Department of Energy, Office of Environmental Management. “Environmental Management Separations 

Technology Challenges,” July 21, 2011. 

acknowledges the importance of minimizing the risks of nuclear proliferation and terrorism and 

5 National Academy of Sciences. Waste Forms Technology and Performance: Final Report, Washington, DC: 

National Academies Press, 2011. 6 

---. “Advice on the DOE’s Cleanup Technology Roadmap,” Washington, DC: National Academies Press, 2009. 

7

U.S. Department of Energy, Office of Nuclear Energy. Nuclear Energy Research and Development Roadmap: 

Report to Congress, April 2010. 8 U.S. Department of Energy, Office of Nuclear Energy. Nuclear Energy Research and Development Roadmap: 

Report to Congress, April 2010.
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commits to working with organizations such as the NNSA, the Department of State, and the 

NRC in an integrated approach to assessing and implementing domestic fuel cycle technology. 

The Department supports the President’s call to work with other nations to “build a new 

framework for civil nuclear cooperation...so that countries can access peaceful power without 

increasing the risks of proliferation.” 9 Technical aspects of this challenge are described in a 2009 

National Academy of Sciences (NAS) report on the growing international character of the 

nuclear fuel cycle.

10 

Recognizing the critical need for clean energy and, hence, for solutions to nuclear fuel cycle 

challenges, the Administration recently established the BRC to guide decisions regarding nuclear 

energy waste management. Coincident with this workshop, the BRC issued a draft report. The 

report supported continued nuclear fuel cycle RD&D and reiterated the need for U.S. leadership 

in international efforts to address safety, waste management, nonproliferation, and security 

concerns.

11 These draft observations are consistent with the planning and deliberations of this 

workshop. 

The Department is also implementing Secretary Chu's vision of using science to provide 

technological breakthroughs to solve all of the United States' grand challenges. DOE offices, 

including NE and EM, aim to utilize high-risk–high-payoff R&D, seeking revolutionary and 

transformational breakthroughs to accomplish agency objectives and, in this case, address 

difficulties inherent in the nuclear fuel cycle. 

The Nuclear Separations Technologies Workshop is both result and forerunner of these 

commitments. As noted above, several offices joined to engage expertise across not only 

government offices but also U.S. industry, national laboratories, and universities. Together, these

participants helped identify high-level R&D needed for innovative solutions to some of the most 

complex, pressing energy challenges facing our country: improving energy production and the 

use of nuclear fuel; assuring that safeguards and security needs are fully met; and reducing the 

volume, toxicity, and lifetime of waste streams. 

1.3 Breakout Sessions 

The above background dictates a need for a fundamental understanding of the separations 

chemistry of the contaminants of concern. At the fundamental chemistry level, challenges run the 

gamut of nearly infinitely dilute solutions to molten inorganic salts. Engineering and scale-up 

pose equivalent complications. As some elements must ultimately be disposed even after 

 

9 The White House. Remarks by President Barack Obama. Hradcany Square, Prague, Czech Republic, April 5, 2009. 

10 National Academy of Sciences, Internationalization of the Nuclear Fuel Cycle: Goals, Strategies and Challenges,

Washington, DC: National Academies Press, 2009. 11 Blue Ribbon Commission for America’s Nuclear Future, Draft Report to the Secretary of Energy, July 29, 2011. 
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successful separations, managing waste is inherently tied to other fuel cycle elements and 

presents comparable challenges. Breakthroughs in separations chemistry and engineering can 

effect significant improvements across the board: costs, schedules, environmental protection,

resource management, and safety and security.

Successfully utilizing separations techniques necessitates a holistic vision of the fuel cycle; put 

simply, the front and back ends must inform each other. Workshop session topics were selected 

to examine the natural progression of the fuel cycle, ranging from fundamental science studies 

(actinide chemistry and speciation, and molecule/material design) to coordination and industrial 

implementation of these technologies (scale-up), as well as interfaces between processes. 

For each session, DOE designated a chair, co-chair, organizer and federal coordinator. With their 

input, DOE also invited panelists and helped ensure diverse participant representation from 

laboratories, universities, and institutes. The preparatory reading posted to the workshop website 

included sets of questions developed jointly by the chairs and panelists that later served to drive 

discussion during the sessions. 

Once the breakouts were under way, panelists provided relevant presentations in their areas of 

expertise, followed by discussion of the subject matter’s relevance to the session’s overarching 

questions. Chairs also dedicated portions of the sessions to soliciting input to the two 

overarching workshop objectives. Participants first identified crosscutting areas of research and 

program interest, noting that carefully coordinating research activities in these identified areas 

would leverage limited federal resources to maximize benefits. Facilitating such synergistic 

efforts and tracking results could be crucial functions of a separations center of knowledge. To 

achieve the final workshop objective, breakout session participants examined this concept, 

discussing its viability, roles, benefits, and features. Section 4 of this report provides session 

findings that evaluate and define a center of knowledge and indicate areas of interest that cut 

across disciplines, DOE programs, and federal agencies.
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2. PLENARY 

2.1 Keynote Address 

Deputy Secretary Daniel Poneman gave the keynote address, describing this workshop as a first 

step towards overcoming “stovepipes” within the DOE complex, improving communication and 

cooperation between the offices involved in nuclear separations. 

Since President Eisenhower’s “Atoms for Peace” program, U.S. nuclear nonproliferation policy 

has undergone several periods of change. For example, significant changes in U.S. policy 

followed India’s 1974 explosion of a nuclear device, which had been developed with technology 

acquired in Canada and the United States. In April 2009, President Obama outlined a new 

framework for international cooperation to support peaceful uses of nuclear energy. Among 

other changes, the Administration shifted program emphasis from near-term deployment of 

commercial-scale reprocessing facilities in favor of further research. A critical R&D area is 

separations technology, which is essential for developing alternatives to PUREX and to HEU for 

production of medical isotopes. 

Advanced separations technologies are also critical for disposing of weapons-related material, as 

well as material from the back end of the nuclear fuel cycle. The tremendous scale of 

environmental cleanup at Hanford and Savannah River pose particular challenges, necessitating 

development of next-generation waste processing technologies to appreciably reduce the cost of 

cleanup. EM is further challenged by $25 billion liability and technical issues with dispositioning 

actinides in tank waste. 

Additional challenges for separations (and other crosscutting) programs are posed by DOE’s 

annual budgeting process, which is focused on individual offices. Multi-year funding can provide 

greater continuity with the certainty that a project is funded for the long term.

The goal of this workshop was to propose viable, cost-effective solutions for the back end of the 

nuclear fuel cycle. Mr. Poneman noted that doing so is an imperative for the planet, adding that 

we have not inherited the Earth from our parents but are borrowing it from our children. 

A question was raised regarding restrictions nuclear supplier nations impose on handling used 

fuel that was irradiated in other countries. Mr. Poneman said that it is incumbent on each supplier 

country to develop waste disposal methodology with sufficient provisions to support processing 

a relatively small additional amount for countries with less developed capabilities. 

Commercialization of the fuel cycle’s back end will provide another major incentive for 

development “once the ice is effectively broken.” 
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2.2 DOE Office Missions 

2.2.1 Office of Nuclear Energy

Dr. Peter Lyons, Assistant Secretary, noted that as separations technologies are encountered 

throughout the nuclear fuel cycle, development of nuclear technology can greatly benefit from 

advancement in nuclear separations. He expected the workshop to influence U.S. separations 

research by identifying crosscutting technology needs across DOE and leveraging R&D to speed 

development. 

The BRC’s work has been heavily impacted by the events at Fukushima, highlighting in 

particular the need for interim storage facilities. The BRC draft report is intended to define a 

publicly acceptable national strategy for managing the back end of the nuclear fuel cycle that 

will guide DOE’s overall fuel cycle R&D strategy. The report focuses on near-term 

improvements to LWR safety, including technologies for storage and disposal of SNF and HLW, 

and long-term efforts to develop “game-changing” fuel cycle technologies. 

DOE’s approach towards 

separations will rely heavily 

on modeling and simulation 

and small-scale 

experimentation, with systems 

engineering principles guiding 

technology selection. By the 

year 2013, NE expects to 

complete a systems 

engineering evaluation of 

three nuclear fuel cycle 

approaches: once-through

cycle, modified open cycle, 

and full recycle. The most promising set of technologies will be researched, followed by 

engineering-scale experiments to enable deployment by mid-century. Grand challenges to 

overcome include development of interim storage facilities, fuel conditioning processes, and the 

full recycle methodology. The ultimate goal is to develop technologies that are superior 

alternatives to the PUREX process. 

2.2.2 Office of Environmental Management

Chief Operations Officer Cynthia Anderson presented EM’s mission: to safely transform the 

environmental legacy of the Cold War into useful assets by completing quality cleanup on 

schedule and within cost. At the start of the cleanup project in 1989, there were 110 legacy sites 

in 35 states occupying a total of 3,125 square miles. This year, the contaminated area will be 

only 350 square miles and, by 2015, only 90 square miles. An important lesson learned from 

Figure 7. Isotopic distribution of used nuclear fuel 

From Dr. Lyons’ presentation: Figure can be found in the 2010 NE R&D Roadmap.
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DOE’s experience is to consider how to dispose of waste from the start of a project, e.g., tailings 

from mining and milling operations in countries developing uranium mines. Key challenges 

facing EM are 1) treatment of 90 million gallons and 600 million curies of tank waste remaining 

at three sites, 2) reduction of the lifecycle costs and legacy footprint, and 3) disposition of the 

remaining 52,000 cubic meters of transuranic waste. 

EM faces a number of separations challenges, including technetium removal and immobilization, 

radionuclide removal from tanks, separation of non-radioactive compounds from HLW, mercury 

and chromium remediation, and sub-surface contamination. Addressing these challenges requires 

developing mature technologies from today’s R&D programs within the next five to ten years. 

Ms. Anderson expected the workshop to help identify needed laboratory R&D, noting that a 

DOE roadmap for separations would help in carrying out workshop objectives. 

2.2.3 National Nuclear Security Administration

Mr. Mark Whitney, Acting Principal Assistant Deputy Administrator for NNSA’s Office of

Defense Nuclear Nonproliferation (NA-20), described the three offices within NA-20 that deal 

with separations technologies: the Global Threat Reduction Initiative (GTRI), the Office of 

Nonproliferation Research and Development (R&D), and the Office of Nonproliferation and 

International Security (NIS). GTRI is responsible for reducing the risk of HEU in civil 

applications (medical isotopes and research reactors), while the Nonproliferation R&D office and 

NIS develop sensors to detect proliferation. NIS works closely with NE to carry out its mission 

of curbing the spread of sensitive fuel cycle technology and would both evaluate threats and 

implement safeguard measures for a separations facility. Factors to consider in developing 

safeguards for this facility include the nature and volume of material streams. However, 

quantifying proliferation risk is challenging. 

Figure 8. Scale-up progression from R&D to deployment 
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2.3 Nuclear Separations Program Overviews 

2.3.1 Office of Nuclear Energy 

Dr. Monica Regalbuto, Deputy Assistant Secretary for Fuel Cycle Technologies, identified the

following challenges: accelerated worldwide deployment of reactor and fuel cycle facilities, 

continuing build-up of nuclear waste from both commercial reactors and DOE, and lack of a 

comprehensive waste management strategy. NE has learned a key lesson from U.S. separations 

history and is incorporating waste management into the development process, which was not 

done for decades after pioneering the development of PUREX separations. 

NE is working towards an integrated, science-based approach that will address the entire fuel 

cycle, optimized through systems analysis and engineering. Criteria are being developed to 

address waste management, resources, proliferation, safety, security, economics, and the 

environment. Improved management of SNF is the near-term goal, while better resource 

utilization is being pursued for the long term. NE seeks partnerships with other agencies and the 

international community to develop and down select fuel cycle alternatives. 

2.3.2 Office of Environmental Management 

Dr. Mary Neu, Chief Scientist for EM, described the centrality of separations to nuclear areas, 

including EM’s mission. Cleaning up the legacy of the Manhattan project, the cold war nuclear 

build up, and nuclear research to the 1980s involves separations and partitioning. Restoring sites 

and processing enormous amounts of materials and waste can be more effectively completed by 

innovation and developing new technologies. EM has successes that used the technology 

development pipeline to provide separations solutions, from fundamental research begun in SC 

through applied research and technology concepts in EM, and technology maturation at sites in 

partnership with national laboratories and federal contractors. EM’s remaining portfolio is 

technologically demanding. Separations and partitioning advances are needed, for example, in 

the following: technetium in waste, groundwater, and soil; non-radioactive species in HLW; and 

mercury in groundwater and soil. EM sees multi-office and agency partnership opportunities to 

meet crosscutting research needs, including stabilization, reuse and disposition of nuclear 

materials, under effective safeguards and security measures and in a manner that minimizes 

waste. Dr. Neu states that the desired outcomes of this workshop were 1) to identify applied 

research for further development into useful technology and 2) to provide the foundations of a 

DOE separations roadmap.

2.3.3 National Nuclear Security Administration 

Dr. Marc Humphrey, Physical Scientist for the Office of Nonproliferation and International 

Security, identified two hypothetical proliferation paths: 1) diversion, in which a host state 

removes small amounts of material over time, and 2) facility misuse, in which a host state 

modifies a declared facility (either clandestinely or overtly after abrogating treaties) to produce 

separated plutonium. Challenges are present in protective actions: material accountancy, process 
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monitoring, surveillance to prevent 

tampering, and verification/detection of 

clandestine misuse. Advanced technologies 

are being developed for accurate accounting 

of plutonium and transuranics in SNF and 

reprocessing plant streams. Development of 

vastly improved separations technologies 

requires corresponding improvements in 

measurement capabilities. Electrochemical 

separations (non-aqueous methods) requires 

an entirely different safeguards approach, as 

those for traditional aqueous methods are not 

applicable to pyroprocessing. A feasibility 

study is under way to use H-Canyon at Savannah River, the only operational industrial-scale 

separations facility in the United States, as a test bed for emerging safeguards technologies. 

Dr. Humphrey stressed that since any separations processes will ultimately need to be under 

safeguards, new processes should be developed with safeguards considerations in mind. 

2.4 Closing Remarks 

In closing, Dr. Regalbuto noted that limited resources require cooperation between the agencies. 

Workshop results, as documented in this report, should serve as a catalyst for future funding, as 

the workshop sends a strong message advocating for separations technology. Moving forward 

requires articulating a plan for the future, developing a budget, identifying key problems, and 

formulating a plan to address those problems. She challenged participants to think beyond their 

own organizations in developing these next steps. 

Dr. Steven Schneider of EM reiterated Dr. Poneman’s charge to break down internal DOE 

stovepipes. By working together, investments can be effectively leveraged towards a common 

separations program goal. This workshop set DOE on the right track and achieved the desired 

outcomes. 

Figure 9. H-Canyon Separations Facility at 

Savannah River 
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3. BREAKOUT SESSIONS 

3.1 Chemistry and Speciation of the Actinides and Key Fission 

Products (Cs, Tc, I) 

CHAIR: Wolfgang Runde, Los Alamos National Laboratory 

CO-CHAIR: Ken Czerwinski, University of Nevada, Las Vegas

FEDERAL COORDINATOR: Jim Bresee, Office of Nuclear Energy

ORGANIZER: Al Sattelberger, Argonne National Laboratory 

3.1.1 Background Information 

Early efforts at separating plutonium and other actinides from irradiated nuclear fuel focused on 

acidic conditions for the fuel’s dissolution and the recovery of uranium and plutonium. PUREX 

uses nitric acid and separates radionuclides by exploiting the differences in the actinide and FP 

chemistries without detailed knowledge of their speciation. Although significant improvements 

in process efficiency, safety, and cost reduction have been achieved, a detailed understanding of 

actinide and FP chemistry and speciation has not been fully integrated. New separations 

processes have been developed using ion exchange, precipitations, and solvent extraction to 

separate radionuclides under high-pH, high-ionic-strength conditions. 

Large-scale separations of plutonium from irradiated nuclear fuel have left behind enormous 

volumes of legacy wastes; Hanford and Savannah River contain the majority of DOE tank waste 

inventory with over 90 million gallons of highly alkaline supernates, saltcake, and precipitated 

solids. A large number of inorganic and organic constituents combine to form a high volume of 

waste with diverse radioactive elements, high radiation fields, and complex chemistry, posing 

significant cleanup challenges. Past waste management policies are unacceptable by modern 

standards, with leakage releasing waste to the environment at both Hanford and Savannah River. 

Speciation under environmental conditions, with lower concentrations and near-neutral pH 

conditions, occurs mainly via ion exchange or sorption onto natural surfaces or by 

precipitation—noticeably different from aqueous-based fuel separations processes.

Disposition of legacy waste requires incorporation into durable forms such as borosilicate glass. 

Understanding and controlling the radionuclide chemistry during these processes can produce 

efficiencies and cost reductions that would greatly enhance DOE’s ability to remediate and close 

sites. 

Throughout the different compositions—from acidic PUREX solutions to near-neutral natural 

environments to alkaline tank wastes—the valence state is the key property that governs the 

behavior, speciation, and coordination chemistry of radionuclides in solution, solid state, and the 
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gas phase. The actinide elements uranium 

through americium can exist in multiple 

oxidation states that dictate their chemical 

behavior, a property that has been 

exploited for separation. Some FPs also 

exhibit significantly different behavior 

when changing oxidation states. 

Understanding and predicting the 

speciation, coordination, and chemistry of 

the actinides and FPs are paramount to 

fully utilizing existing separations and 

developing new processes. Advanced 

technologies need to take advantage of 

scientific discoveries made during the last 

fifty years and may include non-acidic 

aqueous processes, novel solvents 

(organic or ionic liquids), volatility, or 

designer ligands to target individual 

radionuclides or to enable group 

separations. 

3.1.2 Grand Challenges 

Key to improving all separations efforts is accurately understanding the targeted radionuclide 

species’ oxidation states and coordination environments. Likewise, a detailed understanding of 

the speciation of the key radionuclides in waste forms is essential for building a convincing and 

defensible basis for their long-term immobilization. Three principal grand challenges have been 

identified: 

• Molecular chemistry of actinides and FPs in media of inherent complexity

• Effects of radiation chemistry in separations processes

• Advanced analytical and computational tools 

Molecular chemistry in complex media

While complexation of actinides and FPs in PUREX is limited to a few ligands, tank waste is 

inherently complex with a multitude of inorganic and organic ligands. Understanding these 

reactions and exploiting the resulting product species would be extremely valuable. The species 

found in tank wastes have not been extensively investigated and would be expected to be quite 

different from those in near-neutral or acidic conditions. Thermodynamic properties are not 

available for elevated temperatures and complex salt mixtures, and high concentrations of nonradioactive metal cations (aluminum, sodium) can alter composition and stability, leading to poor 

predictive capabilities.

Figure 10. Strategy for reduction of pertechnetate, 99TcO4-, in An-polyoxometalate (POM) 

 
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Effects of radiation chemistry

An intense radiation field can profoundly alter speciation and chemistry of solutions and solid 

phases by attacking chemical bonds, degrading molecules and forming new species. The ability 

to accurately predict speciation requires a detailed understanding of such radiation-induced 

reactions as metal ion reduction, decomposition of solvents and organic ligands, radiolysis in 

aqueous systems, and alteration of solid phases. 

 

Advanced analytical and computational tools 

Present models cannot accurately predict the speciation of radionuclides in highly non-ideal 

systems such as high-level nuclear waste tanks or the multiphase systems present in solvent 

extraction. The imprecision causes significant problems for the treatment and partitioning of 

wastes into high- and low-activity waste streams. Access to advanced speciation tools is vital to 

the scientific communities working with radioactive materials. DOE synchrotron radiation light 

source user facilities have revolutionized the speciation of radioactive materials and have 

become an essential investigational tool. However, access to experimental time and expert 

infrastructure is insufficient. 

It should also be understood that the complex interactions implicit in nuclear fuels processing 

and waste management must be broadly considered: at the molecular and supramolecular levels

and from static (limits of thermodynamic stability) and dynamic (rates and mechanisms) 

perspectives. A broad array of analytical methods must be available for application to address 

these complex interactions. Because many of the species of concern are radioactive, facilities 

with key functions (e.g., nuclear magnetic resonance or mass spectrometry) must be readily 

accessible in locations suited to their applications. The Atalante facility at Marcoule, France, 

provides an example whose design could be considered in the context of advanced analytical 

chemistry. 

Advanced analytical and spectroscopic methods have enabled analysis of speciation on a 

molecular scale. X-ray-related spectroscopic methods, for example, have directly revealed the 

coordination environments of actinide complexes, while advances in x-ray scattering techniques 

probe the dimensions of colloidal species in solution. Development of new analytical 

technologies is critical to detect, speciate and monitor actinides and FPs in such extreme 

environments as nuclear fuel and waste streams.

3.1.3 Proposed Solutions

Molecular chemistry of actinides and FPs in media of inherent complexity: Transition from 

binary mixtures to complex multi-component systems

There is a critical need to comprehend the nature and properties of actinide and FP species in 

extreme environments—high radiation, concentrated salt mixtures, extremes of pH, multiradionuclide and multi-ligand systems—and to be able to predict behavior of these species. 

Chemical properties such as oxidation states and coordination environments can be adjusted to 
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optimize partitioning and separation from multi-radionuclide systems. Solvation and innersphere complexation can be tuned to design organic molecules that target specific radionuclides. 

Similarly, understanding the structural factors of ion exchange materials that lead to site 

specificity will guide the production of new materials with increased selectivity. The open 

literature provides thermodynamic data of actinides and FPs in complex mixtures; evaluating 

these data will help identify additional needs for experimental studies and model development in 

concentrated electrolytes. 

Understanding actinide and FP chemistry will impact a variety of challenges that both EM and 

NE are facing:

• How can actinides be monitored during processing in complex mixtures? (NE) 

• Why does 237

• How can technetium volatilization be minimized, prevented, or otherwise exploited? 

(EM, NE)

Np not partition in solvent extraction steps as predicted in UREX+? (NE) 

• What are the technetium species in Hanford tank wastes, and how can they be partitioned 

in-tank to minimize volatilization of technetium during vitrification in waste treatment 

plants? (EM)

Effect of radiation chemistry on speciation and separation efficiency

Understanding radiolysis’ fundamental effects on solvent, ligands and other separations 

molecules will enable development of advanced models of radiation resistance, decomposition, 

and the formation of radicals to predict process performance. Radiolysis in highly complex 

mixtures must be understood to enable the design of radiation-resistant, selective molecules to 

achieve tailored separations. Isotopes with different half-lives and radiation fields must be 

available to enable radiation studies. Finally, it is essential to train the next generation of experts 

in radiation chemistry and regain U.S. expertise in this field. 

Advanced analytical tools to meet the challenge of measurement and detection

Advanced tools are needed to speciate actinides and FPs in extreme systems, ranging from lowconcentration contaminants to complex environments at elevated temperatures. Direct 

determination of speciation at picomolar (pM) concentrations is needed, along with advanced 

capabilities to determine the speciation of radionuclides in high-radioactive matrices at moderate 

concentrations (mM to μM) in the presence of closely related chemical elements. These new 

tools can also be applied to the direct, real-time measurement of radionuclide concentration and 

speciation for process control and nonproliferation monitoring. 

Expanded synchrotron radiation capability is essential, along with nuclear scientists to provide 

front-line user support and develop new methodologies and techniques. Broader use and 

application of advanced spectroscopic tools could be fostered by transitioning speciation tools 

from rare, large facilities (light sources, neutron sources) to laboratory-based devices. 
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Radiological facilities equipped with more conventional analytical measurement devices must 

also be maintained. 

Development of rapid throughput combinatorial methods would meaningfully assist in 

evaluation of actinide and FP speciation under a range of conditions. 

3.2 Design of Molecules and Materials with Selective Separation 

Properties 

CHAIR AND ORGANIZER: Bruce Moyer, Oak Ridge National Laboratory 

CO-CHAIR: Kenneth Nash, Washington State University

FEDERAL COORDINATOR: Stephen Kung, Office of Nuclear Energy

3.2.1 Background Information 

Advanced processing of irradiated nuclear fuels will require a new stream of separation agents 

that enable solutions to a variety of technical problems that stand in the way of maximizing the 

safety, security, reliability, and performance of nuclear technologies (from electricity production 

to weapons stockpiles to Navy nuclear propulsion), while at the same time reducing the 

possibility of nuclear terrorism. Managing radioactive waste and cleaning up environmental 

contamination pose significant obstacles to the expanded application of nuclear power, leaving 

significant opportunity for expanded R&D and implementation and demonstration efforts. 

Advanced processing of irradiated nuclear fuels will require a new stream of separation agents 

that enable solutions to these diverse challenges while at the same time reducing the possibility 

of nuclear terrorism.

There is a substantial need for new molecules and materials in nuclear separations technologies. 

A variety of methodologies for radionuclide separations in select applications have been 

developed over the course of the last century. More than 50 years of research and process 

experience have produced robust and familiar hydrometallurgical processes such as AMEX 

(AMine EXtraction) for uranium extraction from ore leach liquors using simple fatty amines and 

PUREX for aqueous reprocessing of irradiated uranium and SNF using tributylphosphate (TBP). 

However, when separations goals move beyond recycling uranium and plutonium, new 

molecules and materials to capture and detect target species must be developed. A new 

generation of materials and molecules will offer acceptable and cost-effective technical solutions 

for the wide range of separations needs in both the nuclear fuel cycle and the clean-up of legacy 

sites.

In finding alternative methods or in moving beyond recycling uranium and plutonium, new 

molecules and materials to capture and detect target species must be developed. New 

applications and increasing demand for selective separations drives a new generation of 

research—a new generation of materials and molecules—that will offer acceptable and cost-
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effective technical solutions for the wide range of separations needs in both the nuclear fuel 

cycle and the cleanup of legacy sites. 

Advanced processes will target the recovery of actinides individually or as a group and will 

reinvent the disposition and disposal of currently problematic fission products like 135,137Cs, 90Sr, 

99Tc, 129I, noble gases (Xe and Kr) and the lanthanides. For example, new separation processes 

will allow species such as the minor actinides to be fabricated into targets and recycled to a 

reactor and the lanthanides to be dispositioned. Isolation and transmutation of actinide elements 

significantly reduces the overall hazards of the remaining material.

3.2.2 Grand Challenges (including identified capability gaps)

Confounding advances and improvements are a variety of technical challenges that will require 

innovative solutions (summarized in Section 3.2.3). Several significant challenges are 

summarized below. Solving these, among other, issues will enable the development of new 

separations technologies applicable to a wider range of nuclear fuel cycle and waste management 

applications.

Molecular modeling and simulation and other prediction approaches: Realize the vision of 

molecular-designed separations processes

The ability to predict chemical and physical parameters as a function of composition and 

operating conditions has the potential to dramatically decrease development costs for new 

separations systems, while also optimizing system performance and reducing technical risk. As 

such, a grand challenge is to develop high-throughput screening systems that can predict the 

chemical and physical selectivity characteristics of materials or molecules in order to efficiently 

identify and rank highly selective molecules/materials for use in targeted separations or detection 

schemes. Computational tools must evolve to draw together molecule generation capabilities on 

computers, scoring algorithms, code development, and experimental data. Significantly 

improved modeling and simulation capabilities will enable more efficient molecular design and 

optimal property prediction and will streamline and shorten the R&D timeline across the basic 

discovery, development, and implementation phases of new separations applications. 

Improvements need to be made in scoring or ranking candidate molecules/materials with better 

methods, including using molecular modeling to understand binding affinities, selectivities, and 

macroscopic properties such as the physical properties of the phases (e.g., viscosity, heat 

capacity, vapor pressure) and the distribution of species between phases. Understanding the 

molecular dynamic processes of separation, including solvation at the quantum level and 

transport processes at interfaces, will also be required to make possible the deliberate design of 

processes using separating agents with desired chemical and physical properties. It is important 

that modeling progress in connection with synthesis and experimental characterization studies, 

enabling validation of both computational methodologies and performance of ideal compounds 

and materials.
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Actinide-lanthanide separation: Develop efficient transmutation processes to achieve 

significant reduction in long-term radiotoxicity of fission residues

The three options for managing byproduct wastes of nuclear fission (open, modified open, and 

closed fuel cycles) offer very different time scales for geologic isolation of the radiotoxic 

byproducts and for composition of the disposal package. The closed fuel cycle option seeks 

primarily to minimize the potential impact of long-term radiotoxicity through transmutation of 

minor actinides in fast reactors. This option would offer advantages versus subnational threats if 

the fissile material is sufficiently diluted. The breakout session panel primarily addressed 

separations to support actinide burning of long-lived radionuclides. However, advanced actinide–

lanthanide separations may also enable separate disposal of long-lived radionuclides (minor 

actinides, americium, curium, neptunium) by borehole or other techniques while creating a 

closed fuel cycle without pure plutonium. (It should be noted that the BRC draft report—which 

was issued the day after this workshop took place—included recommendations relevant to 

actinide–lanthanide separations.

12) 

This “ultimate” (transmutation) solution to transuranic management is most efficiently 

accomplished in the absence of lanthanides. Decades of research on this subject have produced 

several wet and dry options for accomplishing this separation, but no clear technology that is 

considered ready for industrial-scale application. Separating the minor actinides from the 

lanthanides involves some of the most difficult challenges in separation science13: chemical 

similarity of americium/curium to FP lanthanides; high specific activity of americium, curium 

and select lanthanides; high neutron capture cross sections of several important lanthanides that 

interfere with actinide transmutation efficiency. It has been established that this group separation 

is most efficiently accomplished through the application of ligand donor systems containing Nor S-donor chelating agents or other soft donor anions (Cl-

, SCN-). A decade-long ligand design 

effort conducted largely in Europe has produced new extractants through multiple investigator 

studies involving most of the European Community. In the United States, this separation has 

been addressed primarily through characterization and modification of the TALSPEAK process, 

in which the actinide-selective soft donor reagent is water-soluble. 

As this separation has not been resolved, the system is a natural target for focus in the 

computationally linked ligand design effort. This system would also be significantly assisted by 

development of new actinide speciation tools described in the speciation breakout panel section

of this report (see Appendix A). Another potential ligand design option for actinide–lanthanide 

separations would be to develop reagents that promote creation of a master blend of plutonium, 

uranium, and possibly other radionuclides for recycling plutonium back into reactors. A 

separations agent that could be used to create a multi-actinide transmutation target while 

 

12 BRC. Draft Report to the Secretary of Energy. July 29, 2011. 13 D. R. Peterman, et al. “Separation of Minor Actinides from Lanthanides by Dithiophosphinic Acid Extractants,” 

Report No. INL/CON-07-13474. Idaho Falls, ID: Idaho National Laboratory, September 2008. 
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rejecting lanthanides and other FPs could provide advantages versus subnational threats while 

reducing associated costs.

Such advanced separations could open pathways to two waste management options. The process 

could provide the feed to fuel fabrication plants to efficiently recycle and transmute transuranic 

isotopes, thereby reducing the proportion of long-lived radioactive isotopes, thus reducing the 

toxicity, that fission residues contain. Alternatively, selected transuranic radionuclides could be 

disposed of via advanced technologies such as borehole disposal,14 which is several kilometers 

deeper than traditional repository disposal, providing potentially superior waste isolation 

capability. This advanced technology would impose restrictions on waste volumes and thus is 

best utilized only after targeted separations have isolated products for long-term disposal.

Interface properties: Understand the properties of interfacial systems to address interfacial 

problems that deter scale-up

In addition to the kinetics and selectivity problems often caused by the transfer of mass to or 

across phase boundaries during separations, interfacial problems contribute to the fouling 

phenomena that, despite the best attempts at design, can deter or halt progress in scaling up 

chemistry in process equipment. Understanding the unique transport, reactivity, and structural 

properties of fluid–solid interface and fluid–fluid interface systems will be required to overcome 

the challenges posed by interfacial phenomena. New experimental techniques and computational 

methods will enable quantitative, fully dynamic, and chemically realistic descriptions of the 

interactions of electrons, atoms, and molecules that give rise to macroscopic interfacial 

properties. This new information will encourage progress in a range of separations science 

applications such as solvent extraction, crystallization of mineral phases from supersaturated 

solutions, selective sorption of ions or gases on solid surfaces, selective transport of ionic and 

molecular species, and controlled formation of large molecular clusters, ions, and particles for 

separation. 

Other major challenges

• Environmentally mobile and volatile species: Overcome the challenge of capturing 

gaseous/volatile FPs using advanced separation agents and stable waste forms for longterm disposal. The separation and containment of gaseous and volatile FP species (such 

as iodine, xenon, krypton and technetium isotopes) from fission residues represent a 

unique challenge. These species are highly mobile and prone to easy dispersal and may 

be difficult to contain owing to the natural dilution associated with the solid–liquid–gas 

phase transfer process, and complicated by the low- to non-reactive nature of select target 

species (e.g., noble gases).

Developing suitable processes to capture and contain these species in stable waste forms 

will allow removal of isotopes of comparatively low specific activity, reduce long-term 

 

14 BRC. Draft Report to the Secretary of Energy. July 29, 2011.
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radiotoxicity of radioactive wastes, and enhance predictability of repository performance, 

thereby improving safety margins.

• Fission products 90Sr and 137Cs: Develop new methods for separation of these species in 

a variety of types of media including tanks, soil, groundwater, and building materials.

Binding agents and solid-ion exchange materials have successfully been used in 

straightforward separations of the fission products 90Sr and 137Cs. However, the 

emergence of new problems (e.g., soil contamination in Japan) has revealed a need for 

more efficient methods that can be used in a range of media types. 

• Decorporation agents: Design new effective, selective, orally active, non-toxic, and costeffective decorporation agents for removing internally deposited radionuclides.

Accidental or inadvertent intake of radionuclides from occupational/environmental 

exposure represents a significant health risk and, as such, is a clear area of emphasis for

EM, NE, and NNSA. To date, only a few standard treatments are available for certain 

radionuclide intakes. New interventional therapies to mitigate the health effects of 

exposure to radionuclides are needed to increase the range and effectiveness of the 

United States' ability to protect humans from radiation effects associated with internally 

deposited transuranic radionuclides. 

Advanced therapies will address the current barrier of prolonged treatments, such as 

chelation therapy using pentetate calcium trisodium (CaDTPA), resulting in depletion of 

biological metal ions and other toxicity side effects, while at the same time achieving 

minimum levels of efficacy, including high levels in immediate post-contamination 

treatment. 

3.2.3 Proposed Solutions

A range of separations issues drives discovery and development of new processes and materials. 

A number of proposed solutions to FP separations were put forward during the workshop. A 

summary of these solutions follows. 

Inorganic ion-exchange materials: Develop inorganic ion-exchange materials with high 

selectivity that result in economical processing into durable waste forms. 

Inorganic crystalline oxide materials (e.g., zeolites, molecular sieves, clays) have chemical, 

mechanical, and thermal stability characteristics that support their widespread use in products to 

be used in environmental cleanup, commercial fuel reprocessing and detection/sensing systems 

for NNSA applications. Examples of target ions and molecules include cesium, strontium, 

volatile FPs (129I2, 85Kr, 14CO2, 3

H) and minor actinides. Understanding structure–property 

relationships in nanoporous materials that are selective for certain ions and molecules will enable 

development of materials that have high selectivity with high capacity. Such materials would 

likely also have high repository performance (i.e., durability) as waste forms (e.g., natural 

mineral analogs).
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Inorganic membrane materials: Design a high-flux–high-selectivity membrane for separation 

of radiological ions from aqueous ion mixtures. 

New technologies with high flux and high selectivity for ion separations in aqueous solutions 

will allow cost-effective separation of radiological ions from ion mixtures in commercial 

processes. Research on inorganic zeolite and/or clay membranes may yield efficient and 

improved membranes with ion selectivity in water with a wide range of salt concentrations that 

also have good thermal and mechanical stability, chemical inertness, and shape tunability—

characteristics that are highly desirable for long-term separations applications. 

Polymer-supported complexants: Design and synthesize ion-selective polymers that can be 

applied in highly dilute metal ion separations applications. 

Achieving targeted separation of 

actinides and rare earths in large scale 

or highly dilute solutions requires ionselective agents and effective 

platforms to deploy them. Polymersupported metal ion complexants offer 

a potential solution to this problem. 

Ion-selective ligands are bound onto 

polymer supports; these ion-exchange 

resins—cross-linked polymer 

networks—are insoluble during 

remediation. After contact with the 

ion-containing solution, the resin—

now selectively loaded with metal 

ions—is separated by filtration. Once 

loaded, it is highly desirable that the polymer be easily stripped of its metal ions using an 

aqueous-based eluent. This characteristic would ensure that the polymer-supported complexant is 

regenerable, re-usable, and environmentally compatible. 

To design materials with rapid loading rates that meet DOE needs for targeted separations in 

select environments, new ligands and platforms to deploy the final polymer must be identified. 

The ligands must be easy to prepare; using diphosphonic acids as ion-selective ligands should be 

explored. New platforms (such as devising novel methods of functionalizing polypropylene) 

must not alter the binding of the target species.

Neoteric media: Develop extractants that do not display decreased utility in large-scale 

aqueous two-phase system separations processes. 

There has been growing recent interest in using separations processes exhibiting both high 

efficiency and selectivity and minimal environmental impact—a combination of characteristics 

not readily obtained with traditional extraction systems, which are frequently characterized by 

Figure 11. Metal ion extraction by ionic liquids 
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the use of toxic, volatile, or flammable diluents. Neoteric solvents, specifically supercritical 

fluids such as SC-CO2, and ionic liquids offer a non-traditional approach to actinide FP

separations.

In order to be viable at a large scale, these solvents must achieve adequate solubility of 

extractants and extracted metal complexes, while at same time maintaining reasonable process 

characteristics (e.g., temperatures or pressures). Developing novel extractants with attractive 

extraction efficiencies and manageable system complexities will require understanding 1) the 

solubilization mechanism of metals into supercritical fluids, 2) the behavior and performance of 

ionic liquids as separations media, and 3) interactions between extractants and surfaces.

Decorporation agents: Perform research to understand metal ion transport in biological 

systems and use knowledge to improve design and selection of decorporation agents with high 

selectivity for the species of interest and high stability under biological conditions. 

Molecules that typically survive in biological systems are extremely complex, as are the systems 

in which they operate. Therefore, a more complete understanding of mechanisms of metal ion 

transport phenomena in biological systems will be required to improve the design of desirable 

and successful decorporation agents. Areas of study comprise quantification of binding affinities 

and selectivities, behavior and stability of metal ion radionuclides in living organisms—

including absorption rates, solubility in biological fluids, and transport by blood to organs—and 

other characteristics of potential chelation agents (metabolites of such agents). The information 

gained from these studies will enable more accurate prediction of agent toxicity and design of 

successful decorporation agents. 

3.3 Scale-up of Separation Processes from Bench-Top to Plant 

CHAIR: Robert Jubin, Oak Ridge National Laboratory 

CO-CHAIR: Raymond Wymer, Vanderbilt University

FEDERAL COORDINATOR: Nicholas Machara, Office of Environmental Management

ORGANIZER: Terry Todd, Idaho National Laboratory 

3.3.1 Background Information

NE, EM, and NNSA face a variety of scale-up issues as they advance separations technology 

from the laboratory “bench-top” to plant scale in order to achieve their mission goals. 

Conceptually, scale-up is relatively simple: engineering principles are applied to a chemical or 

physical process to increase its throughput to achieve a desired plant capacity. However, these 

organizations deal with very complex chemical matrices and physical processes that are not all

yet fully understood. Further, new technologies coupled with existing technologies may result in 

unexpected behaviors in the interaction from one process to the next. 
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As a result, scale-up presents itself as a very complex process that must be tailored to a specific 

situation, where no one standard approach fits every application. This section outlines the 

various challenges that the organizations face in regards to scale-up, as well as proposed 

solutions in order to move towards accomplishing their mission goals. Table 1 below provides an 

overview of separations technology scale-up needs by each of the three DOE organizations. 

Table 1. Overview of Separations Technology Scale-up Interests 

Technology NE NNSA EM 

Mixing X X 

Melter X X

Solid / Liquid Separations X X X

Off-Gas Separations X X X

Extraction Processes X X X

Liquid / Solid Transfer X X X

Testing Sensors on Scaled System X X X

Instrumentation, Analytical X X 

3.3.2 Grand Challenges

Office of Nuclear Energy

NE’s Fuel Cycle Research and Development (FCR&D) 

program focuses on science-based, engineering-driven 

research to better understand potential separation 

processes and identify transformational technologies 

that could potentially reduce the cost and complexity of 

advanced processing facilities. The FCR&D program is 

looking towards a long-term solution for recycling 

SNF, perhaps a decade or two in the future. As such, 

there is currently little effort focusing on equipment 

scale-up until some reference processes are identified, 

with the anticipation for greater future scale-up testing. 

Thus, the main issue is that the processes and 

equipment that will be used are somewhat unknown at 

this point. Nevertheless, as advanced separation 

technologies are developed, the scale-up of specific 

processes will be required. For example, there is a 

certain likelihood that future used-fuel separations 

Separations Progression 

Process development 

 Lab-scale tests of 

chemical/physical behavior

 Chemical models

 Equipment design and testing

Process demonstration 

 Extended tests of flowsheets 

and instrumentation

Simulation and modeling 

 Extraction and E-chem 

processes

 Unit operations 

 Interfacial and molecular-level 

Engineering-scale 

 Equipment design and testing 

 Process implementation

 Control systems 
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facilities to process LWR fuel will incorporate solvent extraction processes to some degree, 

necessitating appropriate scale-up, regardless of whether pulsed columns, mixer-settlers, or 

centrifugal contactors are chosen. Further, prototypic equipment and processes with less 

industrial experience, such as voloxidation, will require specific equipment scale-up testing. 

National Nuclear Security Administration

Rather than scale-up, the stockpile mission of NNSA may be more impacted by scale-down 

issues affecting component refurbishment and dispositioning tasks. Scale-down is reflected not 

only in downsizing existing equipment and facilities, but also in converting continuous processes 

to batch operation—and in the need to address potential changes in performance (particularly 

separations) that may result. Thus, the problem is essentially the same as that of scale-up, only 

solved in reverse. The need is still the ability to determine or predict the transferability of 

performance data between facilities of two specific scales.

In safeguarding any process development activities at engineering scale or above, avoiding 

nuclear criticality and protecting fissile material such as plutonium or HEU are very important 

considerations. Sensors, data acquisition and interpretation systems, and computer modeling are 

essential for material accountancy. In terms of nonproliferation and safeguards missions, key 

components include detection of fissile material processing activities, evaluation of 

unconventional (non-industrial) technologies and processing pathways, and characterization of 

materials generated by these alternative technologies. These include speciation of products, 

formation of byproducts, interaction of reagents and products with process and environmental 

contaminants, and transient behavior.

Figure 12. Scale-up process 
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Office of Environmental Management

EM is focused on near-term implementation of separations technologies to support cleanup of 

their facilities, even though these technologies will be employed over subsequent decades. Many

processes and equipment pieces require testing and scale-up, with some at several levels of scaleup. Further, as EM’s facilities are first-of-a-kind, there is less opportunity for learning from 

previous plants, and each tends to be somewhat unique with different waste streams based on the 

specific site history. The scale-up needs are confounded by the wide variety of materials and 

physical and chemical properties that must be addressed. This makes designing processes and 

scaling them up complex because of the wide variability in the streams to be processed and the 

potential need to test more variations for feeds in the lab in order to simulate what is going to 

happen. Consequently, meeting scale-up needs will require a very ambitious program. For the 

present purpose, no attempt has been made to address the very large programmatic 

commitments, time involved, and budget requirements for meeting the scale-up needs. 

3.3.3 Proposed Solutions

Office of Nuclear Energy

In dealing with the scale-up of solvent extraction processes, data relative to throughput, 

efficiency, and hydrodynamic behavior of the solutions will be required using engineering-scale 

equipment, at a minimum. Specific scale-up testing of prototypic equipment and processes could 

involve engineering-scale testing with simulants and/or actual solutions, as well as mockup 

testing of full-scale equipment. Implementing transformational technologies, significantly 

different from current processing technologies, will likely require a more rigorous effort to 

evaluate and understand scale-up issues. Ultimate implementation relies on an industry that leans 

toward conservatism, deploying evolutionary improvements to proven technologies. Industry’s 

adoption of any new and innovative approach is only likely once a compelling business case can 

be made based on sound research, development, and successful scaled-up demonstrations. 

National Nuclear Security Administration

To avoid nuclear criticality and protect fissile material, it is essential to incorporate, test, and 

establish adequacy of sensing equipment and computer data acquisition and interpretation steps 

in scaled-down operations. Aspects of material accountability are well established, but bringing 

new and perhaps radically different processes on-line may necessitate re-evaluating existing 

safeguards approaches, systems and equipment. Computer modeling of the systems, with respect 

to both individual process steps and integrated systems, is an essential and well-established 

approach to maintaining accountancy.

As for scale-down efforts for nuclear nonproliferation and safeguard missions, the chief 

consideration to be applied is the same as that for any chemical process: a reduced-scale process 

must produce results that are representative of the facility of concern. Therefore, issues to be 

considered in scaling include fidelity of materials transfer operations (e.g., hydraulics), chemical 
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reaction kinetics (including mass transfer operations involving speciation), and use of materials 

(reagents, materials of construction, and likely contaminant sources) identical to those present in 

the facility of concern. Owing to the wide variety of chemistries and the range of possible 

equipment types involved, determination of scale is a function of both the specific unit operation 

and type of data desired. 

Office of Environmental Management

Several processes that require scale-up are under consideration for use in EM’s cleanup effort: 

pulse jet mixing, next-generation melters, solids filtration, pretreatment plant processes, and 

transfer line plugging. Pulse jet mixing has been used elsewhere for mobilization wastes that 

include heavy sludges. In these sludges, avoiding selective sedimentation of suspended solids is 

of special importance because selective sedimentation of plutonium oxide could pose a criticality 

problem. Therefore, it is important to carry out tests at adequate scale on representative solids. 

Current melters could be replaced by next-generation melters of different types and/or sizes, 

requiring their testing and scale-up. Cross-flow filtration is proposed for the filtration of a very 

wide variety of solid suspensions because of its resistance to plugging and fouling. Testing on 

several scales on solids representative of the solids to be filtered will be required. In pretreatment 

plants, testing at several scales of the individual process steps and of the processes integrated to 

study process interactions will be required. Examples of processes include removal of aluminum 

and separations of actinides. Finally, methods of unplugging transfer lines between waste tanks, 

process tanks, and process equipment will need to be studied in prototypic systems at several 

scales using appropriate simulants to test for transfer characteristics and adequacy in 

representative pumping and piping equipment. 

Recent Experience – International and Domestic

The breakout session participants discussed scale-up processes used for several foreign and 

domestic nuclear chemical processing facilities, along with insights from the Technology 

Readiness Assessment 

(TRA) process used to 

evaluate the maturity of 

technologies prior to 

deployment. 

• CEA presented the 

following steps in 

their development 

process: basic and 

applied laboratory 

studies (scale 

1/100000), 

laboratory-scale 

scientific feasibility 

Figure 13. Centrifugal contactors qualified by CEA at La 

Hague 
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(scale 1/10000), engineering-scale technical feasibility (scale 1/1000), pilot-scale 

demonstration (scale 1/100 to 1/10), and industrial-scale test (scale 1). Detailed discussion 

was provided of the nature of data that were collected at each stage, how they supported 

later development stages, and the nature of their impact on the design effort. The group 

introduced insights from recent CEA design, development and construction efforts, 

including installation of centrifugal contactors in the plutonium purification cycle at the 

LaHague plant. Not all steps would necessarily have to be used; for example, for 

adaptations to existing flowsheets, fewer steps would be utilized. 

• An example of a project that was an adaptation of a previous flowsheet (PUREX) is the 

design, development and construction of THORP; during the entire design–build cycle, 

another processing plant was operating at industrial scale on the same site, so significant 

process knowledge could be transferred. The THORP development work was divided 

into “hot,” “warm” and “cold” efforts. Hot testing was reserved for very small-scale 

efforts to maximize flexibility, enabling flowsheet changes. The principal “hot” rig was 

the highly active miniature pilot plant with processing throughput capability of 1 

kg(HM)/day irradiated fuel (1/6250 compared to THORP). It confirmed the complete 

chemical flowsheets for several fuel types. For the full chemical separations flowsheet 

and controls, the majority of R&D experimental work was performed using miniature and 

engineering-scale pulse column equipment with various “warm” feeds (e.g., uranium, 

HNO3, TBP/OK and/or selected components of neptunium, plutonium, technetium, nonradioactive FP simulants). This work—supported by hot testing but still uncertain for full 

scale—was carried out iteratively in conjunction with modeling studies. Mechanical 

components and subsystems were “cold” tested.

• Development of the caustic-side solvent extraction (CSSX) process started with basic 

laboratory-scale testing using simulants. This led to batch contact testing using actual 

solutions in the proposed salt flowsheet under extraction, scrub and stripping conditions. 

Radiolysis testing was then performed using a five-centimeter centrifugal contactor with 

cesium-spiked solution. The following complete flowsheet testing with actual waste used

laboratory-scale (two-centimeter) centrifugal contactors. Performing the tests with 

laboratory-scale contactors minimized the amount of feed solutions needed and the 

amount of waste generated. These tests resulted in construction and operation of a pilotscale separation process for operation of the CSSX process with actual tank waste 

solution; the scale of this pilot plant was determined by an actual mission need to process 

a certain type and volume of HLW. The breakout session group also discussed lessons 

learned from the use of a one-third-scale, non-radioactive melter system in the design and 

development effort for the Defense Waste Processing Facility (DWPF).

• DOE has adopted the TRA process to evaluate the maturity of technologies prior to 

deployment. The TRA process uses descriptions of development stages similar to those 

discussed by the CEA (above), in part, to provide definitions of the technology readiness 

levels (TRLs) that are determined/defined as part of TRAs. As part of the TRA process, 
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however, it is understood that different types of technologies may require adjustments to 

definitions and questions used in TRA evaluations of TRLs. EM has tailored and used the 

TRA process to evaluate nuclear waste processing technologies, and work has been 

performed previously to tailor the TRA process to NE’s needs.

3.3.4 Overall Findings and Recommendations

The scale-up methods used in several foreign and domestic nuclear chemical processing facilities 

can serve as models in development of separations scale-up processes and are generally 

consistent with DOE’s TRA process.

The following is a summary of common scale-up considerations applicable across the EM, NE 

and NNSA. The full report (Appendix C) provides more in-depth discussion. 

• Common process improvements to explore in the near term include: 

o Solid–liquid separations processes

o Off-gas systems

o Evaporation systems 

o De-nitration systems

o Melter/immobilization/stabilization systems

• Scale-up—whether of unit operations, integrated processes, engineering demonstrations, 

pilot plants, or full-scale demonstrations—must be considered very carefully with respect 

to scale-up goals. Goals may be of the following types: 

o Demonstrate unit operations on the appropriate scale, which can be a fraction of full 

scale or, when necessary, at full scale.

o Demonstrate that integrating a separation process’ component parts can be functional 

and seamless.

o Demonstrate that a scaled version of an 

engineering process is of an adequate 

size to meet not only the immediate 

process objective but also the goals of 

other programs that may rely on output 

from the process demonstration. 

o Establish the utility of simulants or 

surrogates to reproduce the desired 

characteristics of feeds to the process 

being investigated.15

 

15 ASTM International. Standard ASTM C1750 - 11 "Standard Guide for Simulant Development, Approval, Validation, and 

Documentation," West Conshohocken, PA.

Figure 14. Pilot-scale integration testing 

for CSSX flowsheet scale-up 
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o Demonstrate appropriateness and efficacy of process monitoring and control 

instrumentation. 

o Demonstrate the validity of fissile materials accountancy instrumentation or other 

equipment related to recording, evaluating, and informing fissile material flow and 

handling irregularities.

o Provide verification and needed improvement to computer models of the process. 

• As the scale-up cycle progresses, ensure that the development team carefully considers 

specific scale-up goals that are reflected in design specifications for construction of test 

equipment at each step of the scale-up process.

• Provide for flexibility in the scaled-up process to study process upsets and off-normal 

events, as well as accommodating unexpected difficulties.

• Within the DOE complex exists a significant body of knowledge, expertise, and 

separations capabilities that must be preserved. An effort should be undertaken to define 

the appropriate functions of a possible center for separations knowledge, as well as 

inventorying the facilities that could be used to support separations scale-up over the next 

five to twenty years. 

• Ancillary issues include the need for a broad-based, solid foundation to maintain and 

advance these issues in the United States. 

3.4 Interface Issues between Separations and Waste Forms/Fuel 

Fabrication 

CHAIR: David Kosson, Vanderbilt University

CO-CHAIR: Bob Sindelar, Savannah River National Laboratory

FEDERAL COORDINATOR: Jim Marra, Office of Environmental Management

ORGANIZER: Bill Wilmarth, Savannah River National Laboratory 

3.4.1 Background Information

Crucial to all nuclear fuel cycles—whether closed, open, or modified—are the interfaces of 

separations processes. In a closed nuclear fuel cycle, considerations regarding the need for waste 

forms involve radioactive wastes generated from the start of uranium mining through its 

conversion and enrichment, fuel fabrication and conditioning, as well as those wastes from postseparations waste streams associated with potential fuel recycling options. Fuel fabrication in a 

closed cycle considers purities of recycled uranium and the need to include burnable actinides 

either as an integral part of the fuel or as a separate target in a reactor core. A modified open fuel 

cycle would also require waste forms and disposal pathways for actinides and FPs removed 

during the minimal reprocessing (see Section 1.2 of this report for a brief discussion of the three 

fuel cycles under DOE-supported study). While the fuel cycle for nuclear power dominates 
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separations R&D discussions, it is also important to plan for disposition of materials and wastes 

generated from other reactor cycles, such as the production of molybdenum-99 for medical uses. 

Therefore, a holistic vision must be given to any nuclear fuel cycle to ensure that the selected 

alternatives for each of the major parts of the cycle would mesh with each other prior to their 

specification. This section presents a listing of the various challenges involved with addressing 

interfaces of separations to waste forms/fuel fabrication in the nuclear fuel cycle, as well as 

recommended solutions. 

3.4.2 Grand Challenges

To identify transformational technology opportunities, fuel cycle components—fuel design, 

waste form specification, repository selection, etc.—should be considered comprehensively and 

with an eye towards the present U.S. reactor fleet and near-term additions to the fleet with 

advanced LWR designs. The following are specific challenges and capability gaps that need to 

be addressed when considering separations interfaces in the nuclear fuel cycle:

1. Establish a baseline fuel cycle(s) with well-defined meshed fuel cycle components. 

2. Establish an approach to down select fuel cycle components. 

3. Establish a prioritization for technology development for an overall “weak” component 

of the nuclear fuel cycle (e.g., waste form for a volatile species) and for further 

technology development among the leading candidates (e.g., “zeolite 1” versus “zeolite 2”

for the volatile species waste form). 

4. Develop technology with low programmatic risk, which necessitates that demonstration 

facilities be available for an RD&D approach to development and ultimate deployment. 

5. Identify management strategies for used fuel storage to allow for radioactive decay, etc.

6. Strengthen the nuclear workforce in the United States.

7. Better define the separation/waste form and then waste form/repository interfaces. 

8. Cultivate a broad base of support, as necessary and appropriate, for facilities in the 

nuclear fuel cycle (e.g., a separations facility). 

9. Strengthen approaches for safeguarding and securing nuclear material, especially in 

separations systems. 

10. Obtain NRC licenses for facilities for commercial nuclear fuel cycle components.

3.4.3 Proposed Solutions

With respect to interfaces between separations and fuel fabrication and used fuel management, 

the overarching conclusion is the need for a systems analysis approach to guide needed R&D. 

Such an approach must be cognizant of and inform essential national policy decisions regarding 

fuel cycle configurations to be developed (i.e., open, closed or modified), the role and 

timeframes for used fuel storage, and repository selection for final waste disposal. In regards to 
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Figure 15. Proposed combination of backend nuclear fuel cycle facilities 

fuel cycle components, development of specific technologies should follow a prioritized 

approach that considers alternatives under the systems approach so as to enable selection of the 

“best” cycle(s) that are risk-informed, with explicit cost-benefit information. For example, 

development and implementation of a risk-informed waste classification system is central to 

defining radionuclide and materials segregation strategies, waste disposition pathways, and waste 

forms. The following presents proposed focused studies that specifically parallel the ten 

identified challenges described above (Section 3.4.2): 

1. For a baseline fuel cycle, a reference set of plausible fuel cycle configurations should be 

established based on major driving criteria (economics, safety, environment, etc.). 

Included would be high-level definitions of timeframes and primary options for each 

stage of each selected fuel cycle, including reactor type, fuel form, storage of used fuel, 

extent of recycling, waste forms, and waste disposition environments. 

2. For the down selection of fuel cycle components, systems models should be developed 

for each selected fuel cycle option that include initial estimates of mass and energy 

balances, considering both existing and to-be-generated SNF. All major primary and 

secondary waste streams should be identified. The potential benefits and risks of colocating major backend components of the fuel cycle (i.e., storage, recycling, fuel 

fabrication, and disposal) should also be evaluated. These systems models should serve as 

the basis for identifying major knowledge gaps and what research will have the greatest 

impact on decision making. The systems evaluation should include development of 

implementation models that define options for private sector participation: roles and 
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economic drivers. Caution must be exercised in the use of “bounding” assumptions and 

models to prevent today’s assumptions from becoming future constraints that are orders 

of magnitude too limiting compared to evolving science and engineering knowledge. The 

commercial nuclear industry, for example, is taking advantage of greatly improved 

analytical techniques by removing excess conservatism from safety analyses, thereby

gaining hundreds of megawatts of additional generating capacity through power uprating 

of existing plants. 

3. Prioritization in technology development should be driven by a process that is transparent 

to interested parties, with a defined set of published objectives, and informed by the 

outcomes of systems modeling. Recognizing timeframes for implementing potential fuel 

cycle options is important for distinguishing urgency in basic and applied research, as 

well as the demonstration of different components of fuel cycle options. A joint national 

laboratory, university, and industry advisory committee would ensure consideration of 

the full development pipeline, from basic research through full implementation. Research 

planning should also leverage international partnerships and investments.

4. Test beds, including cold and hot facilities from bench to engineering demonstration 

scale, will be essential to the success of separations R&D. Pathways and funding for 

access to hot experimentation by university researchers need to be established. Potentially 

available and needed facilities (e.g., glove boxes, hot cells, flexible engineering-scale 

demonstration facilities) should also be identified. Implementation of hot testing should 

be timely in the R&D cycle of the waste form (if implemented too early in the R&D 

process, negative data results may inhibit materials optimization or improvement). Early 

use of the facilities should consider NE, EM, and NNSA needs. 

5. Regarding fuel storage management, further evaluation is needed for the potential role of 

used fuel conditioning prior to storage that includes separation of major components and 

constituents. This is a new concept in response to the potential for intermediate storage 

options prior to subsequent recycling or permanent disposal, which may be needed to 

maintain materials stability for 100–200 years and facilitate later (and potential unknown) 

management options. 

6. In terms of strengthening the nuclear workforce, the existing NE university program 

should be expanded to include subject areas of nuclear chemical engineering, nuclear 

environmental engineering, nuclear chemistry, radiochemistry, actinide chemistry and 

materials sciences. These are essential components to the future of nuclear energy, yet 

they have almost been extinguished because of the lack of investment necessary to 

sustain the necessary academic programs, faculty engagement, and student interest. 

Nuclear energy must realize that it is competing with other exciting, high-tech fields for 

the best and brightest available minds. DOE and NRC should provide greater assistance 

in establishing (or re-establishing) nuclear engineering programs in U.S. universities.
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7. When defining the waste form/repository interface, development and maturation is 

needed for new and alternative waste forms that can be used to manage the full range of 

recycling waste streams (liquid, solid, and gas) and are consistent with planned disposal 

environments. 

8. Research on the social science and communications aspects of implementing future 

nuclear fuel cycles should be a component of the emerging R&D plan. Ultimately, public 

and policymaker understanding and engagement will be central to future decision making 

and the selected path forward. 

9. Safeguards and verification needs, as well as monitoring and instrumentation needed for 

process control, require research that should evolve in concert with process development. 

(Note: There is a similarity of needs for remote observation with respect to environmental 

remediation.)

10. Part of the planning process should involve NRC’s evaluation of R&D needed to for

licensing and oversight evaluations. 

An overarching paradigm for prioritization of recommended programs and activities is that LWR 

technologies are near-term (vis-à-vis the advanced burner reactor). In addition to DOE and 

NNSA programs, common needs and program information sharing with international partners is 

recognized as critical to enable cost-effective, technically sound selection of nuclear fuel cycle 

components that serve U.S. energy needs. 
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4. CROSSCUTTING RESULTS 

As noted in the introduction to this report, the workshop provided participants with two 

overarching programmatic objectives:

• Identify common needs and potential requirements in separations technology and 

opportunities for program partnerships. 

• Evaluate the need for a DOE nuclear separations center of knowledge. 

While Section 3 provided breakout session findings specific to their respective topics, this 

section focuses on crosscutting results that support these objectives.

4.1 Overarching Themes 

During the broad range of technical discussions that occurred during the workshop, several 

themes were consistent across the various sessions. These themes were based on the participants’ 

understanding of DOE separations needs as presented by the sponsoring program offices. 

Therefore, a logical place to begin the dialogue concerning overarching themes is a short 

summary of these needs. 

4.1.1 Summary-Level Program Office Needs

The needs of the various program offices build on the same fundamental separation sciences;

however, the offices have what can be described as differing mission timeframes and scales: 

• To support their near-term mission of environmental cleanup, EM has large-scale and 

near-term needs, especially in the area of waste processing; there is the potential for 

longer-term efforts to support the area of groundwater and soils remediation. 

• NE is looking towards a long-term solution to the recycle of SNF, demonstrating 

technology by the middle of the next decade with commercialization by mid-century. The

challenge is that the specific processes that will be used may be fundamentally different 

from current technology. 

• While NNSA has near-term and long-term needs and has taken actions to transform their 

Defense Program (NA-10) infrastructure to meet program needs, NNSA faces many

challenges in terms of processes and equipment development. These challenges include 

making the best use of existing R&D infrastructure, converting continuous processes to 

batch processes, working with the smaller amounts of materials associated with forensics 

and monitoring functions, and evaluating sensors or remote monitoring tools for 

scenarios that might be encountered in undeclared or misused facilities.
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Because of these differing foci, the offices may identify different priorities in the advancement of 

separations science, technologies and projects. The processes put in place to implement the 

insights gained through this workshop will need to be sensitive to these differing program foci. 

Roadmap strategies, for example, should be inclusive and flexible enough to account for 

alternate R&D pathways within a topic area. As discussed below, the approach to separations 

R&D must be comprehensive in scope, covering not only various program needs but also all 

phases and aspects of the fuel cycle.

Table 2. Target species for separations processes 

Area of Interest* 

Program

EM NE NNSA DOD SC

Actinides: U, Np, Pu, Am, Cm X X X

Volatiles: I, Tc, Cs, Xe, Kr, C, 3H X X X

Human body contaminants: U, Pu, Ra, 90Sr, 129,131I, 137Cs, 60Co X X X

Pyroprocessing/molten salt: U, TRUs, FPs X X X

99Tc and 129I as ubiquitous contaminants/risk drivers X X X

Mercury in groundwater, soil, building materials X X

Cr(VI) in groundwater X 

137Cs, 90Sr in tanks, soil, groundwater, building materials, off-gas X X

Non-rads Al, Na, S, Cr, HNO3, Be, Zr, Pd X X

60Co in groundwater, equipment, RDD cleanup X X 

*Note: After the workshop, gallium was also identified during the report development as a possible area of 

interest.

4.1.2 Need for a Comprehensive Vision of and Approach to Separations RD&D—

Informed by Modeling and Simulation

The sessions dedicated to actinide chemistry and molecule design both described a need to 

develop understandings that spanned the range from atomic-/molecular-scale insights to 

processing system improvements. For example, in discussing interfacial systems, it was noted 

that new techniques will enable quantitative, fully dynamic, and chemically realistic descriptions 

of the interactions of electrons, atoms, and molecules that give rise to the macroscopic interfacial

properties. Additional dialogue centered on the need to understand the properties and behavior of 

materials and reagents in the extreme environments associated with SNF and HLW. The need for 

in-depth understanding of important phenomena, and the environments in which those 

phenomena occur, exists side by side with the need for systems-level models that describe the 

entire nuclear fuel cycle—from mining to placement in appropriate waste disposal facilities—in 

addition to the need for improved subsystem models of separation processes. A holistic vision 
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must be given to any nuclear fuel cycle to ensure that selected alternatives work well in tandem

prior to their implementation. These challenges will require development and continued 

refinement of modern modeling tools to simulate and analyze important problems. 

4.1.3 Need for Ready Access to Appropriately Scaled and Capable Facilities

Workshop participants described the need for both larger- and smaller-scale facilities for 

RD&D—paralleling NNSA’s programmatic needs for smaller-scale solutions and EM’s largerscale requirements. Two examples of smaller-scale needs are the transition of synchrotron 

radiation light sources from large facilities to laboratory-based devices and pathways for access 

to hot experimentation by university researchers. One breakout session group received detailed 

briefings on how staged development of separations processes—from bench scale to engineering 

scale—in the United Kingdom, France, and the United States had substantially contributed to the 

successful implementation of new separation processes over the past two decades. Consistent 

with the above discussion of a comprehensive vision and approach, this discussion of facility 

scale was complemented with dialogue regarding the need to match project or experimental 

goals and objectives to the design and specification of apparatus, regardless of size. 

4.1.4 The Need for Contributions from a Broad Spectrum of Disciplines

Throughout the dialogue at the workshop, there was an understanding that the progress in 

separations science and technology would require the contribution of a broad spectrum of 

disciplines. Clearly traditional technical skill sets are crucial—from radiochemistry through 

nuclear chemical engineering—but the social sciences can also provide insights. On the topic of 

technical areas of expertise, concern was expressed regarding the continued challenges that exist 

in attracting and retaining quality people in the areas of nuclear chemistry, radiochemistry, 

nuclear materials science and nuclear chemical engineering. Several workshop participants 

voiced the importance of training the next generation of experts and strengthening the U.S. 

nuclear workforce, especially to develop the next generation of separations science discoveries. 

DOE is likely to achieve the best results working in concert with universities and national 

laboratories, with possible industry input. Consistent recognition of the need for environmentally 

acceptable options was also evident. For example, one session noted that polymer-supported 

metal ion complexants should be designed to be not only effective but also regenerable, reusable 

and environmentally acceptable. One session identified the need for a more complete 

understanding of metal ion transport phenomena in biological systems. Participants also noted 

that separations solutions needed to be developed with an eye towards compliance with NRC 

regulations. Such insights point to the need for a broad spectrum of experts assisting in the 

development and execution of separations RD&D. 
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4.2 Shared Disciplines/Areas of Interest 

The following sections highlight RD&D disciplines and areas of interest that cut across the four 

breakout session topic areas. Although each topic area is characterized by its own barriers and 

requires its own solutions, commonalities extend across a variety of research efforts. 

4.2.1 Computational Modeling and Simulation

Across the different areas of separations RD&D exists the common need for advances in 

computational modeling and simulation. For example, for scale-up of separation processes, these 

tools can help to design and optimize separations processes and equipment; elucidate scale-up 

issues; and provide information on product and waste stream volumes, radioactivity content, and 

nuclear criticality potential. On a more fundamental level, modeling can predict actinide and FP

speciation, guide separations agent design, predict chemical and physical selectivity 

characteristics, and enable methods to efficiently identify and rank highly selective molecules/

materials for use in targeted separations or detection schemes. Sophisticated modeling and 

simulation methods make it possible to streamline and shorten the R&D timeline across the basic 

discovery, development and implementation scale-up phases of new separations applications. 

4.2.2 Experimental Validation

Currently available predictive capabilities do not always agree well with actual behaviors in realworld settings. For example, the composition of tank wastes affects actinide oxidation state 

stability and solubility; in these environments, predictions may be less accurate or unreliable.

Therefore, in addition to advances in computer models, appropriate experimental validation 

across a range of levels of applications is also needed. Appropriate facilities and easy access to 

such facilities will be required to gather the necessary data to support computer model code 

development, validation, and implementation. 

4.2.3 Radiochemical Diversity

The diversity of radionuclides of potential concern complicates efforts to understand speciation, 

design separations agents, scale up processes, and understand interfaces between waste forms 

and the fuel cycle. Chemical elements may be closely related or may occur in disproportionate 

levels—e.g., small amounts of transuranic elements in the presence of a large excess of uranium. 

New tools will be needed to provide real-time measurement of radionuclide concentrations and 

speciation; and consideration of these diverse elements incorporated into separations process 

development and scale-up methods. 

4.2.4 Challenging Environments

Actinides and FPs are found in a range of environmental conditions. These environments may be 

characterized by low concentrations of radionuclides, high or low ionic strengths, extreme 

temperatures, complex chemistries, large volumes, high radiation fields, etc., which complicate 

theory, experimental approaches, and model development—not to mention design and 
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maintenance of RD&D facilities. To ensure that advances lead to a range of real-world 

applications, RD&D planning needs to provide appropriate attention to the challenges presented 

by environmental conditions. 

4.2.5 National Policy, Regulatory Requirements and Other Considerations

Regulatory and national policy risks invariably affect the future success and impact of new 

technological advances. As an example, methods to prioritize new and further technology 

development among leading candidate materials or processes should be made with respect to the 

best available knowledge of planned disposal environments. To better plan and carry out new 

research, dedicated efforts should be made to understand the most plausible set of realities based 

on current and pending policies and major policy-driving criteria (e.g., economics, safety, 

environment). 

4.2.6 Nonproliferation

A commonality across separations RD&D is the need to prioritize safeguards and security

concerns and insights. For example, research on monitoring and instrumentation is needed not 

only for process control, criticality safety, and waste management, but also for material 

accountancy, safeguards, and remote detection needs. Research supporting safeguards and 

security concerns should be pursued in concert with that supporting process development and 

waste management. 

4.3 Advantages of a Center of Knowledge for Nuclear 

Separations Technologies 

The participants in this workshop were asked to identify the attributes that they deemed desirable 

in a center of knowledge for nuclear separations technology, if established. Their thoughts and 

comments can be broadly grouped as follows. 

4.3.1 Definition of RD&D Needs

Participants identified several attributes of a potential center of knowledge that support the 

identification and further refinement of RD&D needs. 

• Information sharing system: A virtual information system or platform will offer a range 

of information, help minimize duplicative efforts and support the definition of RD&D 

needs. Examples of knowledge that should be captured include: 

o Information and data: Open literature, formal reports and studies, non-classified 

government reports 

o Demonstration projects and other experiential lessons learned: Experience from 

demonstrations that resulted in critical advances in capabilities, such as those with

value as test beds for future scale-up operations and those addressing training new 

personnel 
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o Knowledge management: Capturing, retaining, and sharing past experience and 

existing expertise to ensure its availability for future generations 

o International resources: Links to other resources, including work done by 

international organizations (e.g., Actinet, Japan Atomic Energy Agency, IAEA) 

• Inventory of facilities to support separations scale-up: Efforts should be made to 

identify promising facilities that can support implementation and demonstration of new 

scale-up processes over the next five to ten years. As the scale-up design process 

progresses for a given new process, identifying candidate facilities will streamline the 

design cycle. 

• Resources to build the workforce: Building a workforce of qualified individuals, 

mainly PhDs and scientists, will require opportunities for research funding, access to the 

facilities and information a center could provide, and a communication structure that 

facilitates information sharing and profitable linkages between DOE lab centers, 

academia, and industrial partners. Sample capabilities of the center could include: 

o Mentoring program: Such a program could draw promising candidates into the field 

and compete for the brightest minds available. 

o Training for process engineering, radiochemistry, nuclear chemical engineering, etc.:

Although such opportunities do exist at universities, they are difficult to find and 

often not well promoted. The expertise at the center could provide a platform for 

furthering such training. 

4.3.2 Coordination and Integration of Separations RD&D

One strength of a center of knowledge will come from the coordination of activities, involvement 

of both industry and academia, and clear methods to evaluate and prioritize research 

opportunities. In addition, the center should preserve the knowledge, experience, and lessons 

learned during demonstrations and implementation processes. The participants summarized their 

desired attributes as follows:

System for prioritizing and evaluating separations technology R&D activities: An 

efficient pooling of resources and expertise requires a clear system for prioritizing and 

evaluating R&D needs. This evaluation process will enable optimal synergy in research 

efforts for the strongest possible impact. The process must be detailed with a mechanism for 

application and buy-in across DOE programs and researchers.

4.3.3 Establishment of a Scientific User Facility for Separations RD&D 

A number of comments addressed the need for facilities to perform RD&D on radiochemical and 

nuclear chemistry topics—a facility that could provide access to researchers from academia and 

potentially industry. While it is recognized that program funding constraints would limit 

development in this area, the ideas discussed are summarized below.
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• Improved/upgraded test bed facilities for validating approaches: Appropriate 

facilities for handling radioactive materials and testing approaches could provide the 

experimental data required for validating results of computational modeling. A range of 

conditions (e.g., a wide range of concentrations, hot-cell facilities, etc.) will need to be 

tested; appropriate facilities will enable such testing and validation of advanced methods. 

Related activities include:

o Coordinating access to facilities from the bench to engineering demonstration scale. 

o Identifying needed facilities and equipment (e.g., glove boxes, hot cells, flexible 

engineering-scale demonstration facilities). 

• Connection to the academic community: Rapid advances have been made in such 

fields as molecular modeling, while the number of U.S. PhD graduates in relevant fields 

is increasingly limited. Therefore, the center would be most beneficial if it had a clear tie 

to the academic community. 

• A cadre of nuclear scientists closely associated with the center: A select group of 

scientists with specific expertise needs to be available (i.e., associated with the center) to 

serve as domain scientists and provide front-line user support to aid in efforts around the 

world to develop new methodologies and techniques. 

It should be noted that the last three attributes address a core problem. DOE is presently the 

primary customer of actinide and FP separations; thus, there is not the complement of university 

and industrial research normally found in other areas of science and technology (where there are 

large commercial applications). If DOE wishes to take advantage of university and industrial 

research capabilities, a new mechanism, such as a scientific user facility, is a method that has 

been used by the Department in the past. There are several models on which to build. Within 

DOE, NE has established a scientific user facility, centered at the Advanced Test Reactor, that 

focuses on research requiring reactor, post-irradiation examination or “beamline” (i.e., particle, 

synchrotron, x-ray radiation) facilities. Internationally, experience can be drawn from the 

Institute of Transuranic Research operated by the European Community. 

It is envisioned that a scientific user facility for separations would support development of 

trained manpower and more fully utilize university and private resources by removing a major 

barrier: the paucity of laboratory facilities, especially glove boxes and hot cells—facilities with 

the capability to handle high contamination and high radiation environments. The national 

laboratories have such facilities, but these are dedicated to specific missions—including defense 

missions with restricted access. The experience is that such facilities do not provide the easy, 

assured access required to support university graduate programs or industry. It should also be 

understood that radiotracer studies represent a viable pathway to development of new materials 

and processes, enabling advances in this technology that are not hindered by the absence of “hot" 

facilities; such investigations are readily enabled in an academic environment with considerable 

economy and minimal penalty in information gained. The NNSA decision to identify “Centers of 
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Excellence” in plutonium and uranium to retain proper capability (including nuclear separations 

competence) as part of its nuclear weapons complex transformation should be examined for 

lessons learned.

16

 

16 DOE/EIS-0236, National Nuclear Security Administration, Final Complex Transformation Supplemental 

Programmatic Environmental Impact Statement, Complex Transformation, Volume II, Chapters 5-15 and 

Appendices A-G, October 2008. 
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5. CONCLUSIONS AND NEXT STEPS 

The July 2011 workshop was successful in establishing a foundation of cooperation between

EM, NE and NNSA in nuclear separations technologies. Examples of common areas of 

programmatic cooperation include molecular design targeting specific material separation and 

stabilization, scale-up methods for the rapid deployment of technology with reduced risk, and 

improved understanding of nuclear separations approaches and their relationship with related 

waste form production. 

The workshop also highlighted opportunities for improved technology maturation. SC may 

identify specific separations technologies, explored in the field of basic science, that may be 

ready for development in the applied programs of EM, NE, and NNSA. Better cross-program 

integration and communication will support improved technology “hand-off” between DOE 

offices. 

Such interconnection could be facilitated through a nuclear separations center of knowledge, 

which workshop participants concurred was a candidate for DOE's portfolio of new research 

efforts, such as the Innovation Hubs. A center would provide a mechanism to integrate multiple 

phases of nuclear separations RD&D across DOE offices and address the boundaries between 

science, engineering, and technology development. 

Next steps will build on the foundation established during the workshop to initiate these 

advances in integration and communication. Appropriate actions need to establish this

cooperation in practice, and follow-on actions will optimize available resources and grow the 

programmatic relationships in a manner that accomplishes the greatest good in the shortest time. 

The path forward should initially emphasize high-probability activities that establish the 

organizational relationships. The established network can then mature in parallel with the scope 

and complexity of activities that advance nuclear separations technologies.

The progression of activities to initiate and develop this collaboration is broken into three phases: 

Startup, Growth, and Sustainable Program. 

Startup Phase

Within the first month of the approval of this report, EM, NE, and NNSA will conduct a 

programmatic summit to: 

• Identify specific initial scope for cooperation in FY 2012. 

• Identify initial funding levels. 

• Establish lead staff and national laboratory assignment of roles and responsibilities. 
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• Establish initial functions of a nuclear separations center of knowledge and a path 

forward for a possible national user facility.

Within three months, follow-on workshop(s) will be scheduled to explore additional areas or 

dive deeper into specific subjects identified during the July 2011 workshop. These areas may 

include: 

• Near-term EM and NE interests concerning technetium and iodine recovery and 

stabilization. 

• NE and NNSA interests concerning process instrumentation. 

• Developing advanced modeling capabilities in common support of near-term and longerterm interests of EM, NE, NNSA, and SC.

This phase would also involve preliminary planning for a DOE separations roadmap that would 

discuss technical issues, programs, and collaborations in the areas of separations necessary to 

achieve the goals of DOE program offices. Specifically, the nuclear separations roadmap will: 

• Establish the plans and strategies necessary to develop the cooperation initiated at this 

workshop into a sustainable collaboration between the sponsoring programs, including 

the estimated scope, schedule, and costs associated with the Growth and Sustainable 

Program phases.

• Support the coordinated DOE response to the Blue Ribbon Commission on America’s 

Nuclear Future (BRC) recommendations, expected in January 2012, as they relate to 

nuclear separations technologies. 

• Refine the concept of a nuclear separations center of knowledge that responds to DOE 

needs, improves program partnerships, and supports the effective use of available funding 

and resources.

Establishing a center of excellence for separations technology and an associated user facility for 

R&D purposes will require a detailed proposal and implementation plan. As the facility might be 

open to foreign researchers and cooperating foreign parties, the proposal/plan must ensure that 

the implementation approach will be consistent with and meet the requirements of all applicable 

U.S. nonproliferation-related policies, laws, treaties and agreements, and export control 

regulations.17

 

17 These include, inter alia, the Atomic Energy Act, United States Agreements for Cooperation in the Peaceful Uses 

of Atomic Energy (Section 123 agreements) with foreign State partners, applicable U.S. government export control 

laws and regulations (including DOE controls on the transfer of nuclear technology in 10 CFR 810), and the United 

States-IAEA Agreement on the Application of Safeguards in the United States (INFCIRC/288) (and the Additional 

Protocol).
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Growth Phase

This phase will include confidence-building actions that begin in FY 2013 and continue for

approximately five years (as determined by the roadmap) to expand the scope, increase the 

complexity, and maximize the impact on the applied programs of EM, NE, and NNSA. Growth 

Phase steps will:

• Determine the process to identify new scope (e.g., focused solicitation, proposal 

development, programmatic review).

• Initiate activities that support objectives as established in the DOE separations roadmap. 

• Consider expanded or adjusted DOE staff and national laboratory roles and 

responsibilities. 

• Consider evolving functions of a nuclear separations center of knowledge. 

Sustainable Program Phase

The steps in this phase will depend upon the preceding actions taken to form and build the crossprogram cooperation. Sustainable Program Phase activities will be tailored toward balancing the 

resources available with continued beneficial cooperation for the foreseeable future. 
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REFERENCES 

ASTM International. Standard ASTM C1750 - 11 "Standard Guide for Simulant Development, Approval, 

Validation, and Documentation," West Conshohocken, PA.

National Academy of Sciences. Advice on the DOE’s Cleanup Technology Roadmap. Washington, DC: 

National Academies Press, 2009. 

---. Internationalization of the Nuclear Fuel Cycle: Goals, Strategies and Challenges. Washington, DC: 

National Academies Press, 2009. 

---. Waste Forms Technology and Performance: Final Report. Washington, DC: National Academies

Press, 2011. 

Peterman, D. R., et al. “Separation of Minor Actinides from Lanthanides by Dithiophosphinic Acid 

Extractants,” Report No. INL/CON-07-13474. Idaho Falls, ID: Idaho National Laboratory, September 

2008, http://www.inl.gov/technicalpublications/Documents/4074904.pdf. 

U.S. Department of Energy. Strategic Plan. Washington, DC: GPO, May 2011. 

http://energy.gov/sites/prod/files/edg/news/documents/DOE_StrategicPlan.pdf

---, National Nuclear Security Administration. DOE/EIS-0236, Final Complex Transformation 

Supplemental Programmatic Environmental Impact Statement, Complex Transformation, Volume Ii, 

Chapters 5-15 and Appendices A-G, October 2008.

---, Office of Environmental Management. “Environmental Management Separations Technology 

Challenges,” July 21, 2011. 

http://events.energetics.com/NuclearSeparationsTechnologyWorkshop/pdfs/EM_Separation_Technol

ogy_Challenges_7_21_11.pdf

---, ---. Environmental Management Technology and Innovation Program Plan: Report to Congress, June 

2010. 

http://www.em.doe.gov/pdfs/Final%20Signed%20TDD%20Report%206-21-10.pdf

---, Office of Nuclear Energy. Nuclear Energy Research and Development Roadmap: Report to Congress, 

April 2010. http://www.nuclear.energy.gov/pdfFiles/NuclearEnergy_Roadmap_Final.pdf

---, Office of Science. The Path to Sustainable Nuclear Energy: Basic and Applied Research and 

Development Opportunities for Advanced Nuclear Fuel Cycles, September 2005. 

http://hrcweb.lv-hrc.nevada.edu/rsatg/atw/pdffiles/SCRptonAFCISep05.pdf

U.S. Government, Blue Ribbon Commission on America’s Nuclear Future. Draft Report to the Secretary 

of Energy. July 29, 2011. 

http://brc.gov/sites/default/files/documents/brc_draft_report_29jul2011_0.pdf

The White House. Remarks by President Barack Obama. Hradcany Square, Prague, Czech Republic, 

April 5, 2009. 

http://www.whitehouse.gov/the_press_office/Remarks-By-President-Barack-Obama-In-Prague-AsDelivered/ 
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Appendix A. Breakout Session Report: Chemistry 

and Speciation of the Actinides and Key 

Fission Products 

CHAIR: Wolfgang Runde, Los Alamos National Laboratory

CO-CHAIR: Ken Czerwinski, University of Nevada, Las Vegas

FEDERAL COORDINATOR: Jim Bresee, Office of Nuclear Energy

ORGANIZER: Al Sattelberger, Argonne National Laboratory 

PANELISTS: 

Bruce Bursten, University of Tennessee

Rebecca Chamberlin, Los Alamos National Laboratory

David Clark, Los Alamos National Laboratory

Andrew Felmy, Pacific Northwest National Laboratory

Lynn Francesconi, Hunter College of the City University of New York

David Hobbs, Savannah River National Laboratory

Wayne Lukens, Lawrence Berkeley National Laboratory

Heino Nitsche, University of California, Berkeley

Patricia Paviet-Hartmann, Idaho National Laboratory

David Shuh, Lawrence Berkeley National Laboratory

Peter Zalupski, Idaho National Laboratory

Introduction 

Since the 1940s, plutonium (Pu) and other actinides and fission products (FPs) have been 

separated from irradiated nuclear fuel using a variety of methods including precipitation, solvent 

extraction, electrochemistry, and ion exchange. In early days of actinide science, research and 

technology development efforts focused on acidic conditions appropriate for the dissolution of 

irradiated nuclear fuels and the recovery of uranium and plutonium. The commonly used largescale PUREX separations process dissolves used fuel in hot, concentrated nitric acid; separations 

of radionuclides are achieved by exploiting the differences in the chemistries of the actinides and 

FPs. Solvent extractions are utilized in the PUREX process without detailed knowledge of the 

speciation of actinides and FPs. Understanding chemistry at the molecular level within the 

process was not necessary to achieve target processing/production goals. Process difficulties and 

conditions that could result in process disruption, such as third phase formation, were overcome 

through engineering modifications, typically using an Edisonian—or trial and error—approach. 

Oxidation and reduction reactions control valence state, complexation, and solubility, and hence 

play a central role in the separations. Over time, incremental changes/modifications have led to 

significant improvements in process efficiency, safety, and cost reduction. However, a detailed 
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understanding of actinide and FP chemistry and speciation has not been fully integrated to 

optimize and further improve separations. 

The historic large-scale separations of plutonium from irradiated nuclear fuel have left behind 

enormous volumes of legacy wastes at several DOE sites. The underground tank farms at the 

Savannah River Site and at the Hanford Reservations contain the majority of the DOE tank waste 

inventory, with over 90 million gallons of highly alkaline waste stored as concentrated 

supernates, saltcake, and precipitated solids—referred to as sludges. Tank wastes are complex 

alkaline mixtures containing a large number of inorganic and organic constituents that can affect 

the chemistry and speciation of actinides and FPs in solution and in the precipitated solids. 

Cleanup of the tank waste inventory is a grand challenge because of the large volume, diversity 

of radioactive elements, high radiation fields, and complex chemistry of the wastes. The 

disposition strategy for the tank waste is to separate the major remaining radionuclides from the 

bulk of the waste and incorporate the separated nuclides into a durable waste form such as 

borosilicate glass. New separations processes have been developed using ion exchange, 

precipitations, and solvent extraction to separate radionuclides under high-pH, high-ionicstrength conditions. 

Past waste management policies allowed for radioactive waste disposal practices that are 

unacceptable by modern standards. Leaks in the storage tanks released waste to the environment 

at both the Hanford Site and the Savannah River Site. The radionuclide and hazardous metal 

speciation under environmental conditions, with lower concentrations and near-neutral pH 

conditions, noticeably differs from those occurring under aqueous-based fuel separations and 

pretreatment of tank wastes. In the environment, separations of radioactive contaminants can

occur naturally or be fostered by engineered barriers. Natural retention and separation of actinide 

and FP species occurs mainly via ion exchange or sorption onto natural surfaces or precipitation. 

Engineered barriers can be injected into soil and sediment fractures, relying on those principles 

for contaminant separation from the aquifers. 

Disposition of the legacy DOE high-level waste (HLW), as well as residues from nuclear fuel 

separations, requires incorporation into durable waste forms such as borosilicate glass. The 

behavior of actinides and FPs during waste form processing (e.g., removal of water and high 

temperatures) will be different from that during pretreatment of tank waste and spent fuel 

processing. For example, vitrification of radioactive waste occurs at about 1200 ̊C, conditions 

where the speciation of actinides and FPs remains relatively unexplored. Understanding and 

controlling the radionuclide chemistry during these processes can produce efficiencies and cost 

reductions that would greatly benefit the DOE’s ability to remediate and close sites.

Despite the different compositions of waste and processing streams—from acidic PUREX 

solutions to near-neutral natural environments to alkaline tank wastes—some properties and 

reaction mechanisms are common drivers for the behavior of radionuclides. Separations 

processes rely on small differences in the chemical characteristics of radionuclide properties to 
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achieve successful partitioning and separation. The key property that governs the behavior, 

speciation, and coordination chemistry of radionuclides in solution, solid state, and the gas phase 

is the valence state. In particular, the actinide elements uranium through americium can exist in 

multiple oxidation states, and their chemical behavior is dictated by the oxidation states and 

coordination environments around the metal ion. Trivalent and especially tetravalent actinides 

have markedly lower solubilities than the highly oxidized forms of the actinides in their 

hexavalent and particularly the pentavalent oxidation states. The different chemical behavior of 

actinides in their different oxidation states has been exploited for separations. As an example, the 

redox control of plutonium in the PUREX process accounts for the extraction of Pu(IV) into the 

organic phase and back extraction of Pu(III) into the aqueous phase. 

Some FPs also exhibit significantly different behavior when changing oxidation states. As one of 

the most problematic FPs in Hanford tank waste, technetium (Tc) can be extremely soluble and 

mobile as TcO4-, yet is insoluble as TcO2; the volatile binary oxide Tc2O7 is generated under 

processing conditions which causes about 75 percent of technetium to escape retention in lowactivity waste (LAW) glass which then must be captured in the off-gas. In their different 

oxidation states, the actinides and FPs demonstrate quite different coordination chemistries. 

While the actinides in their III, IV and VI oxidation states show a great affinity to complexation 

with hard donor ligands even at low pH, complexation of pentavalant actinides is less 

pronounced and requires higher pH or higher ligand concentration. The coordination of actinides 

can result in the precipitation of low-solubility phases, but can also lead to increasing solubility 

or the stabilization of actinides in solution. As an example, hydroxides of Pu(IV) have 

solubilities below 10-10 M, while the presence of carbonate, sulfate, or nitrate can significantly 

raise the soluble concentration by the formation of inner-sphere complexes. Understanding and 

predicting the speciation, coordination, and chemistry of the actinides and FPs are paramount to 

fully utilizing existing separations and developing new processes. 

Separation and partitioning of actinides and FPs are central to a variety of technologies ranging 

from intentional separation of radionuclides in irradiated nuclear fuel and partitioning of targeted 

radionuclides in tank waste, to the natural or engineered retention of contaminants in sediments 

and mineral fractures. The speciation of actinides and FPs provides the scientific basis to any 

separation process and can be tuned to take full advantage of the chemical differences for best 

separation performance. Ion exchange, solvent extraction and precipitation are common 

separation processes in natural environments, and engineered technologies and the nature of 

solution and surface complexes and solid phases will determine separation efficiencies. There are 

great opportunities to improve the performances of currently used separations technologies and 

to develop the next generation of advanced separations technologies to meet future challenges. 

Advanced technologies need to take advantage of scientific discoveries during the last fifty years 

and may include non-acidic aqueous processes, novel solvents (organic or ionic liquids), 

volatility, or designer ligands to target individual radionuclides or to enable group separations. 
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1.0 Grand Challenges 

Key to improving all separations efforts is the critical need to understand accurately the nature of 

the targeted radionuclide species. Despite the large differences in characteristics, the 

fundamental separations mechanisms rely on common principles that utilize the different 

chemical properties of the actinides and FPs. Whether the separation involves used nuclear fuel, 

tank waste, or environmental contamination, improving processes in a rational manner requires a 

detailed description of the oxidation states and coordination environments of the key 

radionuclides. Likewise, a detailed understanding of the speciation of the key radionuclides in 

waste forms is essential for building a convincing and defensible basis for their long-term 

immobilization.

Although the chemical behavior and speciation of actinides and FPs is determining the 

performance of any separations technology, three principal grand challenges have been 

identified: 

• Molecular chemistry of actinides and FPs in media of inherent complexity

• Effect of radiation chemistry in separations processes

• Advanced analytical and computational tools 

The chemistry of inherently complex process and waste streams must be understood to advance 

the current state of knowledge and technology. The fundamental chemical reactions in bulk 

(complexation, precipitation) or on surfaces (ion exchange, sorption) occur based on the 

preponderant chemical conditions. These reactions are dictated by temperature, solution 

characteristics, surface chemistry, radiation levels, and presence of ligands. Dissolved actinides 

and FPs can coordinate with ligands to form soluble or insoluble species during separation and in 

waste and process streams. While complexation of actinides and FPs in the acidic solutions of 

PUREX is limited to few ligands, tank waste is of inherent complexity with a multitude of 

inorganic and organic ligands present in the various waste types. Historically, the behavior and 

speciation of actinides in solution and solid phases has been developed with simplistic, wellcharacterized systems with a single actinide and one or two complexing ligands. The synergistic 

effects of multi-ligand, multi-actinide, alkaline systems of high ionic strength remain ambiguous. 

Understanding these reactions and exploiting the behavior of the resulting actinide and FP

species would be extremely valuable for fully exploiting current separations and developing 

next-generation tunable, selective separations methods.

While complexes most important to the near-neutral conditions of natural settings have been 

reasonably well characterized, speciation of actinides and FPs relevant to the different steps of 

the PUREX process remains poorly understood. In addition, the species found in tank wastes 

have not been extensively investigated and would be expected to be quite different compared to 

those in near-neutral and acidic conditions. Under near-neutral conditions, the behavior of 

actinides is largely explained with binary species; the large concentrations of inorganic salts in 
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tank wastes likely cause the actinides to coordinate with multiple ligands to form ternary 

complexes. Thermodynamic properties of actinides and FPs are available for binary complexes 

with very limited extension to elevated temperatures and complex salt mixtures. In addition, high 

concentrations of non-radioactive metal cations (e.g., aluminum [Al] and sodium [Na]) can alter 

the composition and stability of solid actinide phases with different solubility behavior. The 

composition of tank wastes affects actinide oxidation state stability and solubility and, 

consequently, soluble concentrations do not always agree well with currently available predictive 

capabilities. 

The presence of a multitude of highly radioactive isotopes in solutions of dissolved used nuclear 

fuel and tank wastes creates an intense radiation field. The radiation can have a profound impact 

and alter speciation and chemistry of solutions and solid phases, attacking chemical bonds, 

degrading molecules, and forming new species. Common chemical reactions induced by 

radiation are metal ion reduction, decomposition of solvents and organic ligands, radiolysis in 

aqueous systems, and alteration of solid phases. The ability to accurately predict speciation in 

these systems requires a detailed understanding of radiation interactions. Radiation chemistry, 

the study of the chemical effects induced by radiation, is a critical part of any evaluation of 

actinide and FP speciation in separations processes.

 

Modeling efforts for understanding actinide and FP speciation, chemistry, and coordination need 

to be improved for separations. For a given oxidation state, current thermodynamic modeling is 

effective for predicting actinide and FP speciation in aqueous solutions, to some degree as a 

function of ionic strength. These models are also useful for understanding surface complexation, 

which limits migration of radionuclides in the environment. Similar processes occur at the solid–

liquid interfaces during ion exchange. At present, these models cannot accurately predict the 

speciation of radionuclides in highly non-ideal systems, such as high-level nuclear waste tanks or 

the multiphase systems present in solvent extraction. This lack of knowledge hampers 

development of new separations schemes as well as the rational improvement of existing ones. In 

addition, the inability to accurately predict when an actinide or FP species is present in tank 

waste has caused significant problems for the treatment and partitioning of these wastes into 

high- and low-activity waste streams. Furthermore, the coupling of advanced computations on 

the molecular and electronic levels with relevant actinide and FP speciation is lacking. Modeling 

improvements are expected to benefit existing and future separations. 

Access to advanced speciation tools is vital to the scientific communities working with 

radioactive materials. Knowledge of fundamental speciation is a key tenet for the development 

and implementation of rational processes, from basic research to the evaluation of a final 

separations process and for the accurate assessment of environmental consequences. A major set 

of capabilities and tools that has led to a revolution in the speciation of radioactive materials, and 

in fact has become an essential component of many contemporary investigations, has been 

developed at and made available by DOE synchrotron radiation light source user facilities. 

However, the momentum established more than a decade ago has been blunted as access to 
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experimental time and expert infrastructure supporting experiments at these facilities for frontline speciation is insufficient to support world-class efforts necessary to address current 

challenges. Furthermore, the development and implementation of new speciation techniques 

relevant to this field at light sources has decreased in the United States, resulting in a loss of 

leadership in this area. 

The development of advanced analytical and spectroscopic methods to probe highly radioactive 

systems has enabled significant progress to analyze the speciation of actinides on a molecular 

scale. As an example, time-resolved fluorescence spectroscopy can measure the spectroscopic 

features of a few actinides in selective oxidation states (U(VI), Cm(III)) at low concentration 

levels. With the availability of x-ray-related spectroscopic methods to study radioactive 

materials, the coordination environments of actinide complexes in solution, solid state or at 

interfaces have been revealed directly. More recently, advances in x-ray scattering techniques 

enabled scientists to probe the dimensions of colloidal species in solution. Continuous 

development of advanced analytical technologies at the frontier of science is critical to provide 

the analytical tools to detect, speciate, and monitor actinides and FPs in extreme environments 

such as nuclear fuel and waste processing streams.

2.0 Proposed Solutions 

A separations technology program must advance the current understanding of actinide and FP

behavior in extreme environments and develop the next generation of analytical tools to probe 

species under these challenging environments, such as low concentrations, high and low ionic 

strengths, and high radiation fields. Developing the speciation of key radionuclides and 

identifying and characterizing the dominant reaction paths will take time. Concerted, short-term 

and long-term speciation efforts will support and drive tank waste processing, separations 

developments and remediation efforts over the next decades. A set of short-term and long-term 

goals will bridge this time gap and will be beneficial to users and stakeholders. Advanced 

computational tools will better predict the behavior of actinides and FPs in waste and process 

streams. Expertise in actinide and FP speciation exists across the DOE complex and at various 

universities. Teaming of users, stakeholders, experimentalists, and theorists is essential to 

accelerate progress on high-priority objectives in advanced speciation and to support grand 

scientific challenges beyond the current rate.

1. Molecular chemistry of actinides and FPs in media of inherent complexity: Transition 

from binary mixtures to complex multi-component systems

The inherent complexity of environment, fuel processing, or tank waste makes it very 

difficult to obtain a complete understanding of all chemical species and reaction 

pathways associated with the separation and incorporation of radionuclides. However, 

understanding this complexity is essential for the optimization of current processes and 

development of the next generation of advanced separations processes. Comprehending 
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the nature and properties and the ability to predict the behavior of actinide and FP species 

in extreme environments of high radiation, concentrated salt mixtures, multi-radionuclide 

and multi-ligand systems is a great challenge and critical to this endeavor. As an 

example, the design of organic molecules to coordinate with actinides and FPs for 

separation is based on the nature (molecule size, charge) of the targeted (charged or 

neutral) species. Solvation and inner-sphere complexation can be tuned to meet the need 

for a separation designed to target specific radionuclides. Similarly, understanding the 

structural factors of ion exchange materials that lead to site specificity will guide 

chemists and material scientists to produce new materials with increased selectivity.

Information on the behavior of actinides and FPs in complex mixtures will enable 

scientists to improve predictive capabilities extending the thermodynamic database from 

binary complexes to ternary complexes (and beyond) in highly concentrated systems. As 

an ultimate outcome, the gained information will bridge the gap from electronic structure 

to thermodynamics of species in complex systems. A robust and critical evaluation of 

thermodynamic data available in the open literature will identify additional needs for 

experimental studies and model development in concentrated electrolytes. 

Understanding the chemistry of actinides and FPs will impact a variety of challenges 

facing both the DOE Office of Environmental Management (EM) and the Office of 

Nuclear Energy (NE):

• How can actinides be monitored during processing in complex mixtures? (NE) 

• Why does 237Np not partition in solvent extraction steps as predicted in UREX+? 

(NE)

• How can technetium volatilization be minimized, prevented, or otherwise 

exploited? (EM, NE) 

• What are the technetium species in Hanford tank wastes, and how can they be 

partitioned in-tank to minimize volatilization of technetium during vitrification in 

the waste treatment plant? (EM)

Non-conventional separations technologies can be developed only by understanding 

oxidation state stabilities, coordination environments, or electrochemical properties. 

Chemical properties such as oxidation states and coordination environments can be tuned 

to optimize partitioning and separation from multi-radionuclide systems. It is imperative 

that a separations technology program advance the current understanding of actinide and 

FP behavior in extreme environments and develop the next generation of analytical tools 

to enable scientists to probe species under these extreme environments.
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2. Effect of radiation chemistry on speciation and separation efficiency

In order to predict the efficiency of separations processes in high radiation fields, the 

effects of radiation on actinide and FP speciation must be understood. Understanding the 

fundamental radiolysis effects on solvents, ligands, and other separation molecules will 

enable development of an advanced modeling capability to predict process performance. 

Radiation resistance, decomposition, and formation of radicals can be modeled. 

Radiolysis in highly complex mixtures must be understood to enable design of radiationresistant, selective molecules and exploit the resulting chemistry to achieve tailored 

separations. Isotopes with different half-lives and suitable external radiation fields must 

be made available to enable radiation studies. This implies access not only to equipment 

but also to suitable isotopes, which would greatly benefit the actinide research 

community. Understanding and predicting radiation-induced changes in speciation are of 

great importance for any advanced technology using non-conventional solvents to 

dissolve or separate the actinides and FPs.

Studies on the radiation chemistry in separations-related systems were performed early 

on to assist in development of the PUREX process. Radiation studies involved organic 

solvents, extractants, and actinide oxidation state stability. With an aging workforce, the 

knowledge in radiation chemistry is disappearing, which will create a problem in the near 

term. It is essential to emphasize the scientific research needed in radiation chemistry and 

regain the expertise by training the next generation of experts. The development of nextgeneration separations technologies will enable us to evaluate the radiation resistance of 

solvents and solutions to be applied in future separations technologies.

3. Advanced analytical tools to meet the challenge of measurement and detection

Analytical and spectroscopic methods are the tools to characterize actinides and FPs in 

environment and process/waste streams. Some of the most important needs that would 

have great impact on specific scientific objectives and priorities require advanced tools to 

speciate actinides and FPs in extreme systems, ranging from low-concentration 

contaminants to complex environments at elevated temperatures. Currently, low 

concentrations of radionuclides limit speciation in the environment or in cleaned tanks, 

and analytical capabilities need to be improved to enable the direct determination of 

speciation of radionuclides at relevant concentrations down to picomolar (pM) 

concentrations. The presence of a multitude of radionuclides complicate speciation in 

processing and waste streams, and advanced capabilities could determine the speciation 

of radionuclides in high-radioactive matrices at moderate concentrations (millimolar 

[mM] to micromolar [μM]) in the presence of closely related chemical elements. This 

will enable speciation of small amounts of transuranic elements in the presence of a large 

excess of uranium. These new tools can also be applied to the direct, real-time 
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measurement of radionuclide concentration and speciation for process control and 

nonproliferation monitoring. 

Re-establishing and supporting a larger world-class synchrotron radiation capability and 

infrastructure for this field is essential to provide access to advanced speciation tools that 

span the activities in the nuclear separations community. A cadre of nuclear scientists at 

and/or closely associated with the user facilities needs to be available that can serve as 

domain scientists to develop new methodologies and techniques with an explicit mission 

of supporting the prioritized efforts of the scientific community and to provide front-line 

user support. These efforts should be accompanied by a similar emphasis on and support 

of complementary specific laboratory-based capabilities.

To successfully make advanced tools and capabilities available to this scientific 

community on a regular basis and to ensure solid scientific foundations based on 

speciation while regaining preeminence in the field, selective major re-investment in the 

infrastructure that makes current and future advanced speciation of highly radioactive 

materials possible is required. For development of rapid throughput, combinatorial 

methods would meaningfully assist in evaluation of actinide and FP speciation under a 

range of conditions. Broader use and application of advanced spectroscopic tools could 

be fostered by transitioning speciation tools from rare, large facilities (light sources, 

neutron sources) to laboratory-based devices. Although such laboratory-based 

instruments most likely will not reach the power of the larger synchrotron facility, they 

can be a venue to study more concentrated actinide and FP materials.
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Appendix B. Breakout Session Report: Design of 

Molecules and Materials with Selective 

Separation Properties 

CHAIR AND ORGANIZER: Bruce Moyer, Oak Ridge National Laboratory 

CO-CHAIR: Kenneth Nash, Washington State University

FEDERAL COORDINATOR: Stephen Kung, Office of Nuclear Energy

PANELISTS: 

Spiro Alexandratos, Hunter College of the City University of New York 

Joseph Birdwell, Oak Ridge National Laboratory 

Abraham Clearfield, Texas A&M University

David DePaoli, Oak Ridge National Laboratory 

Mark Dietz, University of Wisconsin, Milwaukee

Gordon Jarvinen, Los Alamos National Laboratory 

Daniel Kaplan, Savannah River National Laboratory 

Tatiana Levitskaia, Pacific Northwest National Laboratory

Tina Nenoff, Sandia National Laboratories 

Bill Wilmarth, Savannah River National Laboratory

1. INTRODUCTION AND BACKGROUND 

1.1 Why do we need new molecules and materials in nuclear 

separations technologies? 

In over a century of accomplishment in the development of methodologies for radionuclide 

separations, the steady progress in this field has been enabled by a stream of new separation 

agents. New separations materials have specifically enabled solutions to many types of 

problems—from isolating radionuclides from ores through separations of actinides from 

irradiated nuclear fuels to the daunting challenges of defense waste treatment, environmental 

restoration, and contaminant immobilization.1,2

 

1 Choppin, G. R., M. K. Khankhasayev (Editors) 1998. “Chemical Separation Technologies and Related Methods of 

Nuclear Waste Management: Applications, Problems, and Research Needs.” NATO Environmental Security – 

Volume 53. Klumer Academic Publishers, Dordrecht, The Netherlands.

At first, simple materials were used, including 

readily available neat solvents and natural ion-exchange materials, but the appearance of 

2 NAS, 1999. “Groundwater and Soil Cleanup: Improving Management of Persistent Contaminants.” Commission 

on Geosciences, Environment and Resources (CGER). The National Academies Press, Washington.
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selective solvent extraction (SX) reagents from analytical laboratories and synthetic ion 

exchange (IX) resins from industry opened the door to a range of new separations technologies 

and problem solving. In the mid-20th century, the exploding demand for selective separations 

arising both from the Cold War and the burgeoning nuclear industry drove innovation of many 

new materials and methods. A host of now-familiar processes were developed, such as AMEX 

(amine extraction) to extract uranium from ore leach liquors using simple fatty amines and 

PUREX (plutonium–uranium reduction extraction) for aqueous reprocessing of irradiated 

uranium and used nuclear fuel using tributylphosphate (TBP). Chelating extractants and resins 

provided further progress, as discovered mainly through enlightened empirical research. The 

advent of macrocyclic extractants and the corresponding era of molecular recognition in the 

1970s created a new paradigm for the design of new molecules and materials, enabling solutions 

to previously intractable problems in separations of f-elements and fission products (FPs).3,4,5,6

While a few processes, such as PUREX, have been deployed on an industrial scale, the 

continuing development of separation agents has yielded a number of new processes that either 

have been successfully deployed for specific tasks or have been developed to the point of 

readiness in advanced nuclear fuel cycles (e.g., TALSPEAK for separation of trivalent actinides 

and lanthanides7,8) and for cleanup of legacy sites (e.g., caustic-side solvent extraction for 

cesium removal from tank waste9

 

3 Waste Forms Technology and Performance: Final Report ISBN 978-0-309-18733-6, The National Academies 

Press, Washington, D.C. 2011. 

). While many separation materials developed in the past 

decades have proven economical and powerful for their varied purposes, the current generation 

of materials has not yet enabled the solution to more challenging separation problems posed by 

needs for closing the nuclear fuel cycle, cleaning up environmental contamination, treating Cold 

War wastes, and enhancing national security. Based on the record outlined above, it is projected

that new molecules and materials will open new doors to addressing these persistent issues, as 

strongly echoed by a number of predecessor workshop reports and independent 

4 Wilmarth, W.R., G.J. Lumetta, M.E. Johnson, M.R. Poirier, M.C. Thompson, P.C. Suggs, and N.P. Machara. 

“Waste Pretreatment Technologies for Remediation of Legacy Defense Nuclear Wastes,” Solvent Extr. Ion Exch.,

29(1), 1–49 (2011). 5 Choppin, G. R., M. K. Khankhasayev (Editors) 1998. Chemical Separation Technologies and Related Methods of 

Nuclear Waste Management. Applications, Problems, and Research Needs. NATO Environmental Security – 

Volume 53. Klumer Academic Publishers, Dordrecht, The Netherlands. 6 NAS, 1999. “Groundwater and Soil Cleanup: Improving Management of Persistent Contaminants.” Commission 

on Geosciences, Environment and Resources (CGER). The National Academies Press, Washington.

7 Weaver, B., F.A. Kappelmann.”Preferential extraction of lanthanides over trivalent actinides by monoacidic 

organophosphates from carboxylic acids and from mixtures of carboxylic and aminopolyacetic acids.” J. Inorg. 

Nucl. Chem., 1968, 30, 263-272. 8 Nilsson, M., K. L. Nash. Review Article: “A Review of the Development and Operational Characteristics of the 

TALSPEAK Process.” Solvent Extr. Ion Exch. 25(6), 665-701 (2007). 9 Moyer, B. A.; J.F. Birdwell, Jr., P.V. Bonnesen, L.H. Delmau. “Use of Macrocycles in Nuclear-Waste Cleanup: A 

Real-World Application of a Calixcrown in Technology for the Separation of Cesium.” Macrocyclic Chemistry—

Current Trends and Future; Gloe, K., Ed. Springer: Dordrecht, 2005: pp 383–405. 
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assessments.10,11,12,13,14,15,16,17,18 However, it is also clear that most if not all of the “low-hanging 

fruit” has already been gathered and that new techniques for designing new molecules and 

materials, synthesizing them, and predicting their properties will be needed. 

This appendix addresses the specific needs for new molecules and materials and the challenges 

and questions that must be addressed in future research. Parallels are drawn and overlaps in 

programmatic needs identified to help uncover potential program partnerships within the 

Department of Energy (DOE) and with outside entities. Finally, this appendix presents 

suggestions for proposed solutions to designing new molecules and materials in a sustained 

program referred to as a DOE center of knowledge. 

1.2 What molecules and materials are of interest for selective 

separations? 

Although SX and IX have been the workhorses in the nuclear industry for selective separations 

and are likely to remain strong in this capacity, new molecules and materials are needed in a far 

greater range of separations techniques. To identify where new opportunities for design lie, types 

of molecules and materials relevant to effecting selective separations may be categorized for 

discussion purposes as ligands, reactive solids, media, reagents, and catalysts. Ligands can be, 

for example, SX reagents, aqueous complexants, decorporation agents, functional groups 

tethered to resin backbones, functionalized linkers in 3D metal-organic frameworks, precipitation

agents, flotation agents, and membrane carriers. Reactive solids include solid sorbents, inorganic 

and organic ion exchangers, membranes, and electrodes. Media are fluid phases such as solvents, 

supercritical fluids, gases, and ionic liquids (ILs); they can also be structured fluids such as 

emulsions. Reagents are all types of molecular species added to enhance or enable separations, 

for example, solvent modifiers, filter aids, coagulants, and de-emulsifiers. Catalysts are needed 

 

10 Noble, R. D., and R. Agrawal. “Separations Research Needs for the 21st Century,” Ind. Eng. Chem. Res., 2005, 44, 

2887-2892. 11 Robinson, S., J.S. Watson, J. Harness, D. Melamide, I. Tasker. “Separations Technology Roadmap For DOE 

Environmental Management,” Proc. WM 2003 Conference, February 23-27, 2003, Tucson, AZ. 12 Bredt, P.R., A.R. Felmy, P.A. Gauglitz, D. Hobbs, S. Krahn, N. Machara, M. McIlwain, B.A. Moyer, A.P.

Poloski, K. Subramanian, J.D. Vienna, B. Wilmarth. “Scientific Opportunities to Reduce Risk in Nuclear Process 

Science,” PNNL-17699; July 2008. 13 DOE-EM. Engineering & Technology Roadmap Reducing Technical Risk and Uncertainty in the EM Program; 

March 2008.

14 DOE BES. Technology and Applied R&D Needs for Advanced Nuclear Energy Systems: Proceedings from 

Workshop on Basic Research Needs for Advanced Nuclear Energy Systems, July 31 – Aug 2, 2006. June 2006. 15 DOE. “The Path to Sustainable Nuclear Energy: Basic and Applied Research Opportunities for Advanced Fuel 

Cycles,” Sept 2005. 16 ORNL. Basic Research Needs To Assure a Secure Energy Future, Feb. 2003. 17 Sandia National Laboratories. “Proceedings of the Basic Research Needs for Countering Terrorism Workshop.”

Gaithersburg, MD, Feb 28 – Mar 1, 2002. 18 National Research Council. “Research Needs for High-Level Waste Stored in Tanks and Bins at U.S. Department 

of Energy Sites,” Environmental Management Science Program. National Academics Press, 2001.
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for kinetic enhancements to many processes, which could include crystallization, phase transfer 

in SX, and redox at electrode surfaces. 

Table 1 shows the applicability of these molecules and materials in various separations 

techniques organized by the phases involved. The table serves to emphasize the breadth of 

potential impact of design of new molecules and materials not only for nuclear separation 

technologies, but also across the spectrum of industrial separations. 

Table 1. Role of new molecules and materials in selective separations 

Phases Method

Applicable molecules and materials

Ligands

Reactive 

Solids Media Catalysts Reagents

Solid–liquid Filtration × × × ×

Crystallization/precipitation × × × ×

Dissolution/leaching × × ×

Ion exchange × × × ×

Membranes × × × ×

Zone refining

Electrochemical separations × × × × ×

Magnetic filtration × ×

Gas–solid Adsorption × × ×

Membranes × × ×

Volatilization/sublimation ×

Liquid–

liquid

Solvent extraction

× × × ×

Liquid membranes × × × ×

Extraction chromatography × × × ×

Gas-–liquid Flotation × ×

Distillation ×

Evaporation ×

Sorption × × ×
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1.3 What is meant by "design" of molecules and materials? 

While the word “design” describes many types of human creative endeavor, chemists and 

chemical engineers have enthusiastically appropriated the term not only for development of new 

chemical processes, but also for the materials on which the new processes depend. Judging by 

tens of thousands of publications annually, newly synthesized molecules and materials are more 

often than not said to be “designed.” Although the wondrous molecular structures emerging from 

the realm of supramolecular chemistry19,20 lend credence to such pretensions that chemists have 

a degree of mastery over matter, methods of molecular design in fact remain fairly primitive. 

Often design amounts to logical extensions of new synthetic reactions and resulting families of 

new chemical structures, and there is some truth to the saying that such molecules “go looking 

for a purpose.” In the present context, the purpose in the end lies in new chemical separation 

processes to fill technology gaps, which will be described in the next section. In fact, the 

molecular design must target a conceptual process whose desired characteristics may already be 

known, and thus, molecular design and process design are closely linked. 

Working backward from process needs, designed materials must fulfill a set of specific 

properties, the most important of which are collected in Table 2. The table shows that the 

selective binding of a new separation agent is only the starting consideration of design, in 

harmony with Lehn’s definition of molecular recognition as binding combined with function.21A 

candidate separation agent will fail if it does not bind rapidly enough, for example, or if it does 

not release the bound species efficiently. Separation materials must also be reasonably stable and 

resistant to fouling, and the technology must be compatible with up- and downstream processing, 

minimize secondary waste, and be easy and safe to use. Design therefore implies predictability of 

a multitude of performance characteristics. The goal is that diverse molecular properties of

candidate molecular structures resulting from design can be reliably and quantitatively forecast 

from molecular to bulk scales. 

Based on the assumption that selectivity resides in selective binding of guest species by a host 

structure, present methodology has only begun to address relative affinities. Given that 

thermodynamics of chemical processes are still predictable only in the gas phase, it is clear that 

the full meaning of design remains more of an aspiration than a reality. Methods toward pursuing 

this aspiration will be addressed in the final sections of this appendix. 

 

19 Long, J.R., and O.M. Yaghi. Chem. Soc. Rev. 2009, 38, 1213. 

20 Lee, J., O.K. Farha, J. Roberts, K.A. Scheidt, S.T. Nguyen, J.T. Hupp. Chem. Soc. Rev. 2009, 38, 1450.

21 Lehn, J.M. “Design of Organic Complexing Agents. Strategies Towards Properties,” Alkali Metal Complexes with 

Organic Ligands; Dunitz, J. D., Eds. Springer-Verlag: New York, Vol. 16, pp. 1-69, 1973.
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Table 2. Technical requirements for successful separations agent development 

Category Required Property

Basic functionality Adequate selectivity

Adequate strength (affinity)

Solubility

High capacity

Rapid kinetics (throughput)

Reversibility, recyclability

Technology viability Good stability

Low loss rate

Resists fouling, easy recovery

Phase integrity

Good interfacial behavior

Robust to feed variation

Predictable behavior

Equipment-compatible

Availability

Minor components manageable

Industrial suitability Low cost

Real and perceived risk minimal

Upstream/downstream compatible

Standard equipment

Ease of operation

Safe

Little secondary waste

Environmentally friendly
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1.4 Technology Needs for New Molecules and Materials in DOE 

Applied Programs 

1.4.1 Office of Nuclear Energy

The development of closed-loop nuclear fuel cycles had its origins in the Manhattan Project 

nearly 70 years ago. Activities at the Hanford site in Washington State came into operation in an 

incredibly short period of time and resulted in the first large-scale production of man-made 

elements and ultimately in the site cleanup challenges left behind. The first hydrometallurgical 

separation in this application was based on co-precipitation of the target plutonium with BiPO4, a 

process that was developed in the lab on the few micrograms of the isotope that was then 

available. The process was sufficiently robust to allow the isolation of kilogram amounts of 

plutonium from the complex matrix of irradiated nuclear fuel within a period of less than three 

years from the first ground-breaking at Hanford. 

In the post-World War II environment that ultimately evolved into the Cold War, the advantages 

offered by liquid–liquid contacting led to SX as the preferred method for plutonium production. 

It was thereby possible to recycle uranium, increase throughput, increase quality of the final 

product and reduce the volume (and complexity) of waste byproducts. 

The BiPO4 process was supplanted first by the REDOX process in which plutonium and uranium 

were extracted by methyl(isobutyl)ketone (a.k.a., hexone) from Al(NO3)3 solutions with 

adjustment of oxidation states. The third iteration for plutonium production in the U.S. weapons 

program was the shift from the REDOX process to the PUREX process. In PUREX, the hexone 

extractant solution was replaced by a solution of TBP in odorless kerosene. Today, PUREX is 

used for commercial fuel reprocessing in France, the United Kingdom, Japan, and Russia and is 

continuously being improved. At each stage of this evolution, waste volume and complexity 

decreased. Because the priority during the Cold War was producing plutonium for weapons, 

waste management procedures were given less emphasis, and a system of subsurface waste tanks 

for storage of (predominantly) alkaline residues was established as the most expeditious strategy 

for managing byproducts. 

At the beginning of the 21st century, the nuclear energy and weapons landscape changed. There 

are currently at least nine nuclear weapons nations, though the possibility of nuclear terrorism 

may have become a greater threat than that of a nuclear exchange between nations. More than 

400 nuclear electricity generating units are in operation globally, generating approximately 17% 

of the total electricity that is consumed planet-wide. Though a geologic repository operates in the 

United States for defense wastes contaminated with transuranic elements (the Waste Isolation 

Pilot Plant [WIPP]), there are no operational geologic repositories for the permanent disposal of 

either used nuclear fuel or high-level wastes from reprocessing anywhere in the world. Concerns 

about the global climate have arisen, spurring demand for energy production approaches that 
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release smaller amounts of greenhouse gases into the atmosphere (for which fission-based 

nuclear power is well suited). Demands for primary energy by rapidly industrializing/

modernizing countries like China, India, Brazil, and Russia are increasing. Each of these factors 

is a central consideration in establishing future directions for fuel cycle development. 

The still incompletely resolved issue of managing radioactive waste is a significant obstacle to 

the expanded application of nuclear power. Upon removal of used fuel from the reactor, the 

short-lived FP radioactivity dominates the dose for the first decade or so. The isotopes that 

represent the longer-term risk for radiotoxicity include alpha-emitting transuranic elements 

(neptunium, americium, plutonium), intermediate-lived FPs like 137Cs and 90Sr and mobile 

species like the moderately long-lived 99Tc, 135Cs, and 129I isotopes. Radiotoxicity of used fuel is 

dominated from a few years after discharge from the reactor until about 300 years by 137Cs and 

90Sr. From 300 to about 4,000 years, the radiotoxicity of intact fuel is dominated by 241Am, from 

4,000 to 70,000 years by plutonium isotopes, and from 70,000 to about 2,100,000 years by 237Np. 

In a closed fuel cycle in which plutonium is recycled (removing it from the waste stream), the 

toxicity of the high-level wastes is dominated by 241,243Am isotopes from several hundred to 

70,000 years and by 237Np from 70,000 to at least 2,000,000 years. If all transuranic elements are 

removed and transmuted, the radiotoxicity of the residue returns to that of uranium ore when the 

137Cs and 90Sr have decayed to benign levels (300 years). A significant “advantage” gained in the 

full-recycle approach is increased confidence in prediction of repository performance. Keeping 

the actinides in the fuel cycle with transmutation accrues advantages against subnational threats

while extending the energy potential through recycle of fissile materials.

Today, France, China, the United Kingdom, Japan, and Russia use the PUREX process in 

closed-loop recycling (in DOE parlance, current recycling has most in common with the 

“modified open” fuel cycle). The recovered reactor-grade plutonium is recycled once as mixed 

oxide (MOX) fuel through a light water reactor. The PUREX process is robust, has enjoyed the 

benefit of more than 50 years of research and process experience, and undergoes continued 

refinement. If the goal of fuel processing remains recycling uranium and plutonium, PUREX (or 

a PUREX-like replacement that does not produce a pure plutonium stream) will suffice as an 

acceptable technological solution. However, nuclear fuel cycle reprocessing research being 

conducted around the world is addressing various possible options for advanced processing of 

irradiated nuclear fuels. Advanced processes specifically target several options for recovery of 

actinides individually or as a group. Problematic FPs such as 135,137Cs, 90Sr, 99Tc, 129I, noble 

gases (xenon and krypton), and the lanthanides are targets for developing separations processes 

to aid in their disposition and disposal (or in the disposition and disposal of actinides). 

During the past several decades, the separations research effort in the United States has focused 

on developing processes and reagents to support cleanup of the former weapons complex. This 

focus has led to the development of the SREX (strontium extraction), CSEX (cesium extraction), 

and TRUEX (transuranic element extraction) processes and reagents that enable them; isotopespecific solid sorbents have also been developed. During the same period, the French-led 
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European program has focused on the development of CHON (carbon, hydrogen, oxygen, 

nitrogen) reagents for actinide management in advanced fuel processing. This research has led to 

the development of diamide extractants (and the DIAMEX) process, a class of compounds based 

on bis-triazinyl pyridine and bipyridine ligands. New dithiophosphinic acid extractant molecules 

and approaches to their use have also been proposed. 

Each of these research efforts has been enabled by the search for new reagents and material 

design. 

Following are several separation issues that still drive the discovery of new processes:

• Recovery and recycle of fissile/fertile components (uranium/plutonium isotopes) without 

producing a pure plutonium product. The challenges arise from the multiplicity of 

“stable” plutonium oxidation states that enable easy chemical manipulation to isolate 

plutonium if desired. The opportunity

•

 is to keep plutonium in the fuel cycle, either 

producing energy or being associated with FPs.

Minor actinide (neptunium, americium, curium) management, which in a closed loop 

recycling system with transmutation requires isolation of americium/curium from the FP

mixture (or even better, selective isolation of americium) with moderately efficient 

separation of americium/curium from FP lanthanides. A variety of options exist for 

neptunium management within a dedicated uranium/neptunium/plutonium recycle system 

(it should be noted that neptunium is also a potentially valuable byproduct as source 

material for 238Pu production for space applications). The challenges arise for 

americium/curium/lanthanides from the chemical similarity of the two classes of 

elements; the high specific activity of americium, curium, and selected lanthanides; the 

high neutron capture cross sections of all members (which interferes with transmutation 

efficiency of americium/curium); and the elevated spontaneous fission half-lives of some 

curium isotopes. The opportunity

•

that drives interest in this separation is considerable 

reduction in radiotoxicity of fission residues that is gained by transmuting americium). 

Prevention of the release of gaseous/potentially volatile species (iodine, xenon, krypton, 

technetium isotopes). The challenge arises from the ease of dispersal and difficulty of 

containment of volatile radioactive species and the non-reactive nature of noble gases. 

The opportunity

•

 is that the containment of these isotopes removes comparatively low 

specific activity, environmentally mobile radioactive components from effluents and so 

improves safety margins.

The development of suitable waste forms for ultimate disposal of environmentally mobile 

byproducts, neptunium, technetium, iodine, xenon. The challenge arises from the low 

charge of neptunium and technetium oxidized species, iodine in all oxidations states, and 

the non-reactivity of xenon. The opportunities driving the development of new materials 

for these targets are reduced long-term radiotoxicity of radioactive wastes and increased 

predictability of repository performance. 
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While progress has been made in global research efforts to address some of these problems, this 

work continues, as preferred solutions have not yet emerged, though strong candidates exist in 

some areas. 

1.4.2 Office of Environmental Management

The DOE clean-up inventory22 includes 90 million gallons of radioactive waste, safely stored in 

230 tanks; 1.7 trillion gallons of contaminated groundwater; and over 3,000 excess contaminated 

nuclear facilities with significant quantities of curies as hold-up in process equipment and miles 

of pipelines. In addition, billions of cubic meters of contaminated soil and debris exist at the 

sites. Estimated life cycle costs of the EM cleanup approach $350 billion and could take an 

additional 50 years to complete. At the apex of these clean-up efforts lies a need for a 

fundamental understanding of the separations chemistry of the contaminants of concern. The 

challenge at the fundamental chemistry level runs the gamut from nearly infinite dilute solutions 

to molten inorganic salts. The engineering and scale-up challenges are just as enormous. 

Significant breakthroughs in separation chemistry and engineering as well as development of 

suitable waste forms23

 

 can effect significant improvements to reducing the technical risks 

involved in the EM cleanup and significantly reduce life cycle costs and schedules. 

The radiological risk drivers at the various low-level and high-level waste disposal (LLW and 

HLW, respectively) sites across the DOE complex are remarkably similar even though their 

inventories, site conditions, mode of immobilization, and modeling assumptions vary 

considerably. Table 3 presents the key risk drivers calculated from performance assessments for 

a wide range of different radiological facilities. Note that 99Tc, 129I, and 237Np are common 

drivers for LLW, tanks, and HLW. 

Table 3. Risk drivers identified for a wide range of different radiological facilities 

Site Facility Risk Driver Source

Hanford LLW Integrated 

Disposal Facility

99Tc, 129I, U, 126Sn, 

237Np

Mann, F. M., R. J. Puigh, S. H. Finfrock, R. 

Khaleel, M. J. Wood. “Integrated Disposal 

Facility Risk Assessment.” RPP-15834. 

CH2M Hill Hanford Group, Inc., Richland, 

WA, 2003.

SRS E-Area LLW Facility 99Tc, 129I, 14C, 3H Washington Savannah River Company. “EArea Low-Level Waste Facility DOE 435.1 

Performance Assessment, Volume 1.” 

 

22 DOE-EM. “Report to Congress: Status of Environmental Management Initiatives to Accelerate the Reduction of 

Environmental Risks and Challenges Posed by the Legacy of the Cold War,” DOE/EM-0001, Washington, DC, 

2009.

23 NAS. “Waste Forms Technology and Performance: Final Report ISBN 978-0-309-18733-6.” The National 

Academies Press, Washington, DC, 2011.
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Site Facility Risk Driver Source

WSRC-STI-2007-00306, Rev. 0. Aiken, 

SC, 2008.

SRS Tank 19 99Tc, 129I, 237Np Department of Energy – Savannah River.

Section 3116: “Determination for Closure 

of Tank 19 and Tank 18 at the Savannah 

River Site,” DOE-WD-2005-002, Rev. 0. 

Aiken, SC, 2005.

SRS Tank 18 237Np Ibid

INL Remote HandlerLLW Facility

99Tc, 129I, 14C, 238U, 

226Ra 

Idaho National Laboratory. “Assessment of 

System Wide Features Incorporated into 

the RH-LLW Disposal Facility Providing 

Protection of Human Health and the 

Environment (Draft).” INL/EXT-10-19385, 

2011.

YM Yucca Mountain 99Tc, 129I, 237Np and 

Pu

Hornberger, G. M. “Total System 

Performance Assessment – Site 

Recommendation.” Letter to Richard A. 

Meserve. NRC. 2001. 

http://www.nrc.gov/reading-rm/doccollections/acnw/letters/2001/1290175.html

Examples of separations research areas related to the EM mission where new molecules and 

materials have potential for significant impact are described below.

Technetium chemistry, removal, and immobilization: The complex chemical behavior of 

technetium in tank waste and subsurface environments, limited incorporation in mid- to hightemperature immobilization processes (i.e., vitrification, steam reformation, etc.), and high 

mobility in subsurface environments makes technetium one of the most difficult contaminants to 

address in the DOE complex. There are critical needs for technetium separation and materials 

development at several steps within the nuclear cycle, many of which have unique chemical 

environments. Some of these needs are as follows.

Technetium is primarily present in alkaline tank waste at the Hanford and Savannah River sites. 

A substantial portion of the technetium in tank wastes will partition into low-level activity waste. 

Technetium in the process systems/pipelines of the Gaseous Diffusion Plant (GDP) at East 

Tennessee Technology Park (ETTP in Oak Ridge) has resulted in significant time delays and 

additional expenses. Similar issues may be present at the GDPs at Portsmouth and Paducah. 

Procedures and materials are needed to clean up these process systems/pipelines. Also, 

understanding the chemical adsorption or desorption and separation processes are needed for 
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technetium on metal waste streams. Technetium is a key contaminant in meeting regulatory 

requirements for near-surface land disposal performance, including reducing cementitious 

materials, owing to the large inventory of technetium to be disposed in low-activity or secondary 

waste streams. Within the DOE complex, there are 16 subsurface technetium plumes.24 An 

acceptable baseline technology for remediating technetium in subsurface environments does not 

exist. There is a need for a sorbent that is inexpensive and will remain effective for an extended 

duration that can be used in the vadose zone. 

Fundamental studies that enable understanding of the chemistry occurring across the range of 

conditions described above, along with comparisons of non-radioactive surrogates (e.g., ReO4

-

), 

would expand the ability to perform large-scale experiments and further improve behavior 

predictions. Potential technologies that could be applied include inorganic sequestering agents, 

additives, or techniques and improved selective absorbents. These materials could conceptually 

be deployed in a variety of in situ and ex situ configurations, such as active barriers, grout 

additives, subsurface fixatives, and waste stream treatment or pump-and-treat facilities. 

Development of improved IX media or precipitation agents could enable substantially simplified 

removal processes.

 

Mercury chemistry, removal, and immobilization: Historic uses of mercury at Oak Ridge have 

resulted in extensive environmental contamination. Remedial actions have reduced mercury 

input to a local creek by more than 90%, but stream water and fish remain impacted, primarily as 

a result of dynamic mercury methylation/demethylation processes and other complex ecological 

and bio-geochemical interactions. Additionally, deactivation and decommissioning activities at 

Oak Ridge are expected to result in physical disturbances that may release additional mercury to 

soil, groundwater, and surface water. While mercury contamination is an impending issue at Oak 

Ridge, mercury contamination is or will be problematic throughout the complex. 

 

Cost-effective technical solutions are needed for waterborne mercury remediation and soil 

treatment. Waterborne mercury can be addressed through the development and demonstration of 

innovative methods that utilize specialized resins, unique nanomaterials, or chemical addition to 

transform, absorb, and/or remove mercury. Both in situ and ex situ soil treatment methods are 

needed for removing mercury or stabilizing it within environmental matrices. The development 

of effective treatment methods for mercury depends on a sound understanding of mercury 

speciation, reactivity and association with minerals and materials, as well as technical 

approaches for separating mercury from a variety of matrices. 

Hexavalent chromium detoxification and removal: Chromium was released to groundwater and 

soil at DOE sites as a consequence of leakage or disposal practices. At the Hanford site, for 

example, hexavalent chromium was used in reactor cooling water to prevent corrosion and for 

 

24 Hazen, T. C., B. Faybishenko, and P. Jordan. “Complexity of groundwater contaminants at DOE sites.” LBNL4117E. Lawrence Berkeley National Laboratory, Berkeley, CA, 2008. 
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plutonium oxidation state adjustment in the REDOX process. Hanford, Oak Ridge, and other 

DOE sites also possess groundwater and soil contaminated with chromium above regulatory 

limits. Refinements to chromium separation processes are needed to reduce dependence on 

current pump-and-treat approaches that will pose a long-term expense for treating high-volume, 

low-concentration waste streams.

Radioactive iodine chemistry, removal, and immobilization: Iodine-129 is one of the most 

difficult contaminants to address in the DOE complex because of its complex chemical behavior 

(including volatility), limited long-term retention in immobilization processes, and high mobility 

in subsurface environments. There is limited understanding of the behavior, speciation, and 

mobility of iodine in sedimentary environments associated with past co-disposal of waste 

streams and the impacts on environmental remediation. Improved remediation technologies for 

groundwater are needed to provide long-term solutions. Potential technologies that could be 

applied include organic sequestering agents, inorganic sequestering agents (including silverbased), additives, or selective absorbents. Development of selective IX media or precipitation 

agents could enable subsequent development of new removal processes. These materials could 

conceptually be deployed in a variety of in situ and ex situ configurations, such as active barriers, 

grout additives, subsurface fixatives, and waste stream treatment or pump-and-treat facilities. 

Development of waste forms or additives to current waste forms with long-term retention 

properties would be beneficial to improve the sites’ performance assessments. 

Removal of non-radioactive species from high-level waste: Non-radioactive constituents in tank 

sludge waste limit the amount of waste that can be incorporated into the final glass waste form at 

both Hanford and Savannah River. The primary limiting constituents are aluminum, sodium, 

chromium, and sulfur. Improving removal of these constituents from the sludge and partitioning 

them into the aqueous waste would reduce the volume of HLW glass produced. Furthermore, 

although aluminum is removed by caustic addition, the amount of caustic needed to maintain its 

solubility in downstream processes causes an enormous increase in the waste processing duration 

and low activity waste form volume. A related challenge is phosphate at the Hanford Waste 

Treatment Plant. 

Materials are needed to achieve a more effective separation of constituents by 1) removing 

species that limit waste loading in high-level glass, 2) removing constituents that may limit or 

bound the operating conditions of other processes (e.g., phosphate), and 3) developing additives 

to stabilize aluminum solubility or developing improved prediction tools and control of 

aluminum solubility. Aluminum solubility is a very significant cost and schedule driver, 

especially at Hanford. Establishing reliable methods to maintain and predict aluminum solubility 

to ensure it does not plug the cesium IX process at Hanford or the SX system at Savannah River 

would reduce the amount of sodium hydroxide added. Therefore, it would be helpful to develop 

materials that would either enhance aluminum solubility or prevent aluminum species from 

precipitating at an inappropriate process point.
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Removal of key radionuclides for tank closure: Tank closure is currently achieved by filling the 

emptied and cleaned tanks with grout. Determining the readiness of the emptied tank for closure 

is not straightforward from technical and regulatory perspectives. Significant cost and schedule 

savings can be achieved through a combination of new separation technologies and methods to 

efficiently empty tanks to the maximum extent practical. Improving chemical cleaning methods 

that target key radionuclides and eliminate generating secondary waste could provide substantial 

benefits. Conversely, developing sequestration materials and methods to inhibit migration of key 

radionuclides from residues in closed tanks could also result in significant cost and schedule 

savings and minimize subsequent downstream impacts of secondary wastes.

Integrated subsurface remedial strategies for site closure: Many of the subsurface contamination 

problems at legacy nuclear weapons sites currently have no practical remedy. Left untreated, 

contaminants will migrate to groundwater or surface water, presenting a long-term risk to 

environmental resources, human health, and the environment. The current treatment approach for 

groundwater is pumping and treating, but many active pump-and-treat systems are inefficient in 

extracting contaminants from the subsurface and do not achieve cleanup goals within reasonable 

timeframes and costs. 

 

Strategies are needed to transition active physical removal of contaminants to more effective and 

efficient monitored attenuation remedies. Both natural and enhanced attenuation can be thought 

of as in situ separation processes. Separation of contaminants is achieved by diminishing their 

migration, either through naturally occurring physical, biological, or geochemical reactions or 

via the addition of amendments designed to retard mobility. There is a particular need for 

inexpensive sorbent materials to remove groundwater technetium that is not based on REDOX 

transformations and would last hundreds to thousands of years. 

A key issue related to long-term stewardship of radiological disposal sites is: How does 

deterioration of the waste package influence rate of release? Laboratory, pilot-scale studies, and 

analogue field studies are needed to develop conceptual and input values for models.25,26 A 

specific example demonstrating this question would be: What is the process by which slagcontaining cements re-oxidize? 

Contaminants of concern during demolition and disposal: Current decommissioning methods are 

costly, with significant potential risk to personnel. New in situ approaches, such as entombment, 

are being investigated to facilitate decommissioning. A scientific basis for entombment is needed 

not only in the development of these new approaches but also in the fate of decommissioned 

facilities. There is a need for new decontamination agents that can extract contaminants from 

 

25 Miller, W., R. Alexander, N. Chapman, I. McKinley, J. Smellie. “Natural Analogue Studies in the Geological 

Disposal of Radioactive Wastes, Studies in Environmental Science.” 57, Elsevier, Amsterdam, 1994. 26 Wang, L., E. Martens, D. Jacques, P. DeCanniere, J. Berry, D. Mallants. “Review of sorption values for the 

cementitious near field of a near surface radioactive waste disposal facility.” 2009.
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pores and cracks in the materials or treat the materials in situ. Additional options may be to 

develop bio- and nanomaterials for decontamination. The new agents and materials would then 

be integrated with equipment and techniques for remote application and removal of 

decontamination agents. 

1.4. DOE National Nuclear Security Administration

The mission of the National Nuclear Security Administration (NNSA) comprises four 

components: 

1) To maintain and enhance the safety, security, reliability, and performance of the U.S. 

nuclear weapons stockpile without nuclear testing. 

2) To reduce the global danger from weapons of mass destruction. 

3) To provide the U.S. Navy with safe and effective nuclear propulsion. 

4) To respond to nuclear and radiological emergencies in the United States and abroad. 

Separations needs in the performance of each of these mission areas vary significantly. The 

processes used in the performance of weapons production and refurbishment are well established 

and highly developed. The conversion of 34 metric tons of excess weapons plutonium to MOX 

fuel in the plant under construction at the Savannah River site will require a head-end 

purification operation that is based on PUREX chemistry. Due to the value and relative scarcity 

of the materials involved, stringent product specifications and safety requirements, and the large 

capital investments that have been made in existing plants (or those under construction), changes 

to these separation processes require large advantages to justify to DOE and the facility 

operators. In spite of this, changes to separation processes can result in substantial improvements 

that are implemented. For example, the conversion to calcium chloride (from NaCl-KCl 

mixtures) for electrorefining operations at Los Alamos will reduce operational and waste costs. 

Also, new separations operations are under consideration such as re-establishment of 238Pu 

production, 241Am recovery for use in neutron sources for industry, and 234U recovery from 238Pu 

operations. 

With respect to nuclear proliferation concerns, there are several mission needs that require 

detailed knowledge of separations technology or would benefit from design of molecules and 

materials to capture and detect target species. The first mission need is the detection of nuclear 

separations operations performed using known processes or closely related processes and 

established chemistries. This includes detection of degradation products and emissions generated 

during operations. A closely related aspect is the evaluation of safeguards for advanced fuel 

cycle separations. A second need requires the capture of species of interest that may be present at 

extremely low concentrations. This application calls for separations media that have strong 

affinities for target species and high selectivity for them. Collection media that are also designed 

to signal uptake of a target species (through fluorescence, for example) would be of particular 

value. Very high reliability for a positive signal is a key concern. As deployment may be in 
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remote locations and for long exposure times, durability of the separation material and platform 

are important. A third area of interest is the design of chemical markers for tagging chemicals 

that could be used in materials processing or in weapons components, as a means of tracking 

supply chains. Finally, improved separations technology is under development to provide 

economic alternatives to the use of highly enriched uranium in research reactors for medical 

isotope production. The goal is to allow conversion of all research reactors from highly enriched 

uranium to low-enriched uranium. 

An additional need that is not specific to NNSA activities is the development of separations 

systems for the decontamination of surface waters, infrastructure, surfaces (such as soils, 

buildings, etc.) and personnel in the aftermath of an accidental or intentional dispersal event, be 

it chemical, biological, radiological, or nuclear. Effectiveness, ease of disposal, and the ability to 

manufacture large quantities of the decontamination system at reasonable cost are key factors.

2. TECHNICAL CHALLENGES, GAPS, AND QUESTIONS 

2.1 Challenges in the Design of Separation Materials for DOE 

Technology Needs 

Towards addressing the technology needs for selective separations in DOE programs, new 

molecules and materials are expected to lay the foundation for the processes of the future. The 

corresponding grand challenge is the question of design itself. Namely, what basic science and 

tools are required for the design of new molecules and materials, and how can they be applied to 

real problems? For given types of separation methods, what are the specific technical gaps that 

stand in the way of progress? This section explores these cross-cutting questions in greater detail, 

in turn suggesting opportunities for productive program partnerships to be presented in a 

subsequent section. 

2.2 The Grand Challenge—Learning How to Design Separation 

Materials 

Current experimental approaches to process development starting from molecular concepts 

consume 15–20 years in basic discovery, development, and implementation phases. Nearly half 

that time involves risky, empirical, expensive testing of many candidate separating agents, and 

progress tends to stop with the first usable candidate rather than the optimum one. Further, 

unanticipated deficiencies in the molecular system as discovered in scale-up or pilot testing are 

often mitigated with inefficient work-arounds adopted under schedule pressure vs. finding more 

functional molecular alternatives. The result is a long, expensive R&D timeline and (the path to a 

successful plant has many potential pitfalls) a plant that is unnecessarily, and possibly 

prohibitively, expensive to build and operate. Thus, there is incentive to improve both the 
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discovery and selection of candidate separation materials and the prediction of their various 

properties that determine their performance under complex and even extreme conditions. 

The magnitude of this challenge can be appreciated by the number of disparate properties and 

performance characteristics that must be anticipated in the development of a new separation 

agent and corresponding process, as listed in Table 2. Given that none of the required properties 

currently can be predicted except qualitatively, the challenge of predicting the overall 

performance of a candidate separation agent is staggering. The real problem is further 

compounded by the essence of design in being the identification of an optimal molecular 

structure from an initially specified set of target properties. Thus, the challenge qualifies as 

“grand” and may be stated as follows: How can highly selective separation materials be designed 

with predicted characteristics that can be applied to targeted separations and detection schemes?

Opportunity: Predicting the chemistry associated with separations represents an area where 

modeling and simulation, conducted in concert with focused experimental development, have 

potential for a large return on investment. When coupled with large molecular databases 

(cheminformatics) or in silico molecular generators (de novo design), the ability to predict 

chemical and physical parameters as a function of composition and operating conditions provides 

the means for identifying new separating agent candidates on the computer prior to any synthesis 

and testing. This capability would dramatically decrease development costs for new separations 

systems, optimizing performance and reducing technical risk. 

Where we are: The ability to predict chemical and physical properties makes possible the 

deliberate design of separating agents with desired chemical and physical properties. Computer 

screening of candidate molecules through electronic structure and force-field models has been 

validated by experiment and has been highly valuable in significantly reducing the experimental 

effort needed.27 Candidates for screening can be derived from chemical intuition or from 

databases of known molecules. 

The past decade has seen the development of computer-aided design software, in which 

candidate separating agents are generated on the computer from molecular fragment libraries and 

then ranked using high-throughput screening methods.28,29,30

 

27 Lumetta, G. J., B. M. Rapko, B. P. Hay, R. D. Gilbertson, T. J. R. Weakly, J. E. Hutchison. “Deliberate design of 

ligand architecture yields dramatic enhancement of metal ion affinity,” J. Am. Chem. Soc., 124, 2002: 5644-5655. 

This software is currently used to 

facilitate the discovery of host molecules in projects currently supported by the DOE Office of 

28 Hay, B. P., and T. K. Firman. “HostDesigner: a program for the de novo structure-based design of molecular 

receptors with binding sites that complement metal ion guests,” Inorg. Chem. 41, 2002: 5502–5512. 29 Hay, B. P., A. A. Oliferenko, J. Uddin, C. Zhang, T. K. Firman. “Search for improved host architectures: 

application of de novo structure-based design and high throughput screening methods to identify optimal building

blocks for multidentate ethers.” J. Am. Chem. Soc. 127, 2005: 17043–17053. 30 Hay, B. P., T.K. Firman, G.J. Lumetta, B.M. Rapko, P.A. Garza, S.I. Sinkov, J.E. Hutchison. “Toward the 

computer-aided design of metal ion sequestering agents.” J. Alloys Comp., 374, 2004: 416-419.
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Basic Energy Sciences (receptors for anions and contact ion pairs, building blocks for selfassembled anion receptors), the Defense Threat Reduction Agency (receptors for chemical 

warfare agents), and the DOE Office of Nuclear Energy (receptors for An(III)/Ln(III) separation, 

receptors for uranyl from sea water). The software has recently been parallelized for use on highperformance computers. 

Molecular modeling and simulation can be used in scoring by calculating binding affinities, 

selectivities, and macroscopic properties such as the physical properties of the phases (e.g., 

viscosity, heat capacity, and vapor pressure) and the distribution of species between phases.

Continuum solvation models, incorporated in electronic structure codes, allow the accurate 

prediction of free energies of solvation for a wide variety of solutes and solvents, providing an 

approach for predicting partitioning equilibria between phases. Molecular dynamics (MD) 

simulations predict properties, such as viscosity and vapor pressure, to within experimental 

accuracy for a variety of neat solvents. There is also precedent for the use of MD simulations to 

predict solute free energies and complexation equilibrium constants. Grand canonical Monte 

Carlo simulations have been shown to be effective in screening metal–organic frameworks for 

selective separations in complex gas mixtures relevant to off-gas streams from nuclear 

processes.31

In addition to molecular modeling approaches, QSAR (Quantitative Structure-Activity 

Relationship) methods, widely used in the pharmaceutical industry, can often be adapted for 

property prediction. These methods quantitatively correlate calculated physicochemical 

properties for a molecule (volume, density, dipole moment, surface area, etc.) with known 

chemical reactivity or physical properties. Well-known examples include boiling point 

prediction, pKa prediction, the Hammett equation, and the Taft equation. When experimental 

data are lacking, molecular modeling, either with electronic structure or force-field methods, can 

be used to obtain the physicochemical properties for such correlations.

What needs to be done: Computer-aided molecular design involves generating possible 

molecular structures followed by high-throughput screening to rank them with respect to a 

targeted property. Although much progress has been made, further research is needed to attain 

molecule-generating algorithms that achieve a complete coverage of synthetically accessible 

chemical space for small (≤ 200-atom) compounds. Accurate ranking of computer-generated 

molecules with respect to a given property will require improved property prediction. Scoring 

capability must be prioritized based on need and cost effectiveness, identifying areas where 

modeling and simulation can now make useful predictions and areas where further theoretical 

development is needed. 

 

31 Sava, D.F., M.A. Rodriguez, K.W. Chapman, P.J. Chupas, J.A. Greathouse, P.S. Crozier, T.M. Nenoff. "Capture 

of volatile iodine, a gaseous FP, by zeolitic imidazolate framework-8," J. Amer. Chem. Soc., 2011, 133 (32), 12398–

12401.
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Molecular Modeling Improves Design of Selective Sequestering Agents

The earliest study (1994–1996; EM-50 funding) using molecular modeling methods for 

design of sequestering agents focused on optimizing the performance of the SREX 

reagent. The reagent, di-t-butyl-dicyclohexano-18-crown-6, exists as two regioisomers, 

and each form has six chiral centers. All 40 possible isomers were evaluated for Sr2+

binding affinity and Sr2+/Ca2+ selectivity to identify the most effective Sr2+ getters. 

Purification of individual isomers and testing in solvent extraction systems has 

confirmed these rankings.

Another design goal was to modify the CSEX reagent to achieve enhanced Cs+/K+ 

selectivity. The effort (1997; EMSP) led to the discovery of a new class of calix[4]crown 

ethers, derived from 1,3-dideoxygenated calix[4]arene. Experimental surveys 

demonstrated that the new calix[4]arene architectures display Cs/Na selectivities 

exceeding 106 and Cs/K selectivities exceeding 103, tenfold improvements over 

previously studied calix[4]arene crown ethers. Modification of the CSEX reagent

architecture by removal of two alkoxy groups yields a cavity predicted to have enhanced 

Cs+/K+ selectivity. This prediction was confirmed by experimental measurement.

A final example is provided by diamide extractants for trivalent f-block cations. Structural 

evaluation of conventional malonamide extractants developed for use in the DIAMEX 

process revealed the O-donor atoms in these architectures to be poorly organized for 

complexation. Using structural design criteria obtained from theoretical and 

experimental data regarding the conformations of amides and metal-amide complexes, 

an alternative bicyclic architecture was designed and tested. Liquid-liquid extraction 

measurements with hydrophobic analogs revealed the designed extractant gave a 

spectacular performance enhancement, exhibiting Eu(III) and Am(III) distribution 

coefficients 10 million times larger than obtained using the best engineered malonamide 

extractant under identical experimental conditions. Aqueous formation constant 

measurements confirm that the performance enhancement is due to an increase in metalbinding affinity.
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As with drug design, current scoring algorithms rely on structure-function relationships, taking 

advantage of the fact that certain easily computed or measurable candidate properties correlate 

with the property of interest that may be impossible to calculate with experimental accuracy. 

Examples include speciation, reaction mechanism, equilibrium constants, separation factors, 

interphase transport and equilibria, precipitation from solution, micellization, third-phase 

formation, hydrolysis, radiolysis, and oxidation states. Long-term research toward solving these 

problems will ultimately entail the development of novel methods and the software to implement 

them.

2.3 Technical Gaps 

Following is a description of the technical gaps and other challenges identified for current 

separation methods, interfacial systems, and new molecules and materials, including actinidelanthanide separation, interfacial phenomena, inorganic ion-exchange materials, inorganic 

membrane materials, polymer-supported complexants, neoteric media, and decorporation agents. 

2.3.1 Actinide–Lanthanide Separation

Statement of the problem: Minimization of the long-term radiotoxicity of radioactive byproducts 

of uranium-based nuclear fission depends most significantly on strategies to recycle and 

transmute transuranic isotopes, most importantly plutonium, neptunium, and americium. Though 

it is always possible to improve the performance envelope of separation systems, several options 

are suitable for industrial application to facilitate the management of plutonium and neptunium. 

Americium isotopes (241/243Am) represent a more difficult separation challenge. The chemical 

similarity between americium, curium, and FP lanthanides is the problem. Though americium

offers an intriguing redox opportunity, the upper oxidation states are each strongly oxidizing, 

hence suffer stability limitations. As a result, group separations (americium/curium from 

lanthanides) rely mainly on the presence of ligand donor atoms softer than oxygen (nitrogen, 

sulfur, Cl-

) for preferential bonding with actinides. Both SX and IX methods have been 

developed, but the continuing global research effort dedicated to this separation attests to the 

absence of a fully acceptable solution to the problem. In essence, the fundamental feature needed 

to accomplish this separation is known. A strategy for implementing this chemistry at the 

production scale remains elusive (though there are some well-developed candidate separations, 

e.g., SANEX, TALSPEAK, that have potential). 

Why this approach is difficult: Several factors contribute to the challenge of accomplishing this 

separation using soft donor complexants/extractants: 

• Because the bonding in most coordination compounds of f-elements is predominantly 

ionic, soft donor atoms interact weakly with these cations under most conditions, though 

more strongly with actinides than lanthanides. 
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• Because the interactions are weak and differences between lanthanides and actinides are 

subtle, complexants/complexes must incorporate multiple soft donor atoms for adequate 

separations to be attained. 

• Incorporating multiple soft donors results in complex structures that can be expensive and 

difficult to synthesize. 

• The cations are relatively large and so demand a larger binding cavity than most dtransition elements. 

• Because the valence orbitals are core-like in their spatial extension, cation-directed 

valence effects are practically nonexistent—the coordination geometry in complexes is 

defined mainly by steric effects and coulombic attraction (thus the metal ion cannot assist 

in defining coordination geometry). 

• Both classes of metal ions are strongly hydrated, moderately susceptible to hydrolysis 

(and so to precipitation of metal hydroxides); thus either aqueous complexants must be 

used and/or acidic conditions must be maintained. 

• Radiation fields can be high, thus consideration of the potential for reagent degradation is 

essential. 

• For SX applications, ligand design must balance sometimes conflicting requirements: 

phase compatibility, the need for interfacial activity, maintaining rapid phase transfer 

kinetics, the need for reversibility.

Successful separations have been developed around soft donors in aqueous and organic media— 

there are potential advantages to either approach. To date, none has been put into practice, 

though some have been tested at the pilot scale. 

Why pursue such a difficult challenge? 

• Partitioning and transmutation of the transplutonium actinides reduces the long-term 

radiotoxicity of the waste from advanced fuel cycles. 

• Reduced radiotoxicity increases design safety margins for repositories. 

• The alternative redox approach to separating americium from curium and lanthanides is 

equally challenging scientifically. 

• The pyrometallurgical approach has unresolved waste management challenges and is best 

suited to a fuel cycle based on fast reactors. 

What is the science-based approach to development of such reagents?: The science-based 

approach is to combine lab-scale efforts in organic synthesis with lab-scale studies of 

separations/coordination chemistry involving trivalent lanthanide and actinide metal ions. 

Studies with surrogate metal ions can provide valuable information, but the metal ion 

partitioning studies must be done with representative species. Computational chemistry tools 

should be employed for the design of appropriate ligand architectures to promote rapid progress 
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toward viable candidate ligands. Characterization studies are based on monophasic and biphasic 

solution thermodynamics and kinetics investigations complemented by structural studies to 

establish design criteria for computer modeling of molecular interactions through multi-molecule 

system performance. As basic studies progress and the properties of new reagents are improved, 

feedback from process designers should be integrated and reagents/conditions adjusted to 

develop reagents and processes most suitable for scale-up to application levels. This approach 

parallels that taken in the extensive European program that has developed the malonamide, BTP, 

and BTBP extractants and potential SX processes using these extractants. This program still 

continues to search for improved alternatives to the current best systems. 

This approach could be used to examine, prepare, and evaluate a range of complexing agents 

suggested by past experimental work and augmented by molecular-mechanics-based 

computational design. The complexing agents could be soluble in aqueous solution, used as 

phase modifiers, phase transfer catalysts, organic extractants, or specialized reagents suitable for 

application in neoteric solvents. The basic design criteria can also be employed in the 

development of cation receptors for polymer-based resin materials. Besides developing 

extraction ability and selectivity in reagent design, adjusting phase compatibility/solubility 

control and methods for improving radiation stability should also be considered. Appropriate 

ligand architectures can also find application in analysis for process control or nuclear materials 

accountability applications.

2.3.2 Interfacial Phenomena

The transfer of mass to or across phase boundaries is ubiquitous in separations science, 

controlling kinetics, and often selectivity. In addition, a host of so-called interfacial problems lie 

at the heart of fouling phenomena that, despite the best attempts at design, can deter or halt 

progress in scaling-up chemistry in process equipment. Important phase interfaces are listed in 

Table 1 (Section 1.2 of this appendix). Their atomic/nanoscale reactivity, structures, and 

transport properties are in general poorly understood, and the lack of fundamental molecularlevel understanding of interfacial phenomena has often led to Edisonian approaches to resolving

technological challenges related to chemical separations. 

The unique properties of fluid–solid interface systems emerge from a complex interplay of shortand long-range forces and reactions among the molecular fluid components, solutes, and 

substrates. Potential gradients (chemical, electrical, etc.) can be highly nonlinear at the 

Ångstrom-nanometer scale, leading to unexpected behavior. The finite size, shape, directional 

bonding, charge distribution, and polarizability of solvent and solute fluid components are 

convoluted with their ability to reorient, “unmix,” and react with one another and the substrate. 

The truncated solid surface exposes under-coordinated atoms that drive dynamic interactions 

with the adjacent fluid by local bond relaxation, charge redistribution, dissolution, precipitation, 

sorption, and porosity development/destruction. 
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Following are processes of potential interest that would benefit from a more in-depth probe of 

fundamental fluid–solid properties in separation science:

• Crystallization of pure mineral phases from supersaturated solutions—a non-energyintensive separations technology, where solution composition, temperature, pressure, and 

other environmental parameters can be manipulated to control nucleation and growth 

rates (e.g., radium sequestration through incorporation as an impurity in a nucleated solid 

phase).32

• Selective sorption of ions onto solid surfaces via control of substrate pore size, surface 

potential, ion solvation and complexation in solution (e.g., molecular modeling and 

electrochemical studies indicate that inorganic cations and anions in aqueous solutions 

show a wide range of diffusion rates in carbon nanopores, and one could conceive of a 

tailored series of electrochemical capacitor anode/cathode couples that could separate 

product streams enriched in specific salts)

• Selective transport of ionic and molecular species through nanopores by control of pore 

size, pore shape, surface functionalization, and manipulation of solvophobic/solvophilic 

properties of the solvent and substrate (e.g., mesoporous carbon and ceramic films 

tailored for selective transport of gaseous and/or dissolved species in a wide range of 

solvents) 

• Mobilization and separation of selected species via controlled formation of large 

molecular clusters, polyatomic ions and colloidal particles, or crystalline nanoparticles, 

wherein the stability of the macroatomic entities, their morphologies, densities, magnetic 

and electronic properties, and their transport properties in porous solid substrates can be 

manipulated by controlling the environmental conditions and/or the substrate/solvent/

cluster interactions (e.g., the well-known Al13 “Keggin” ion is a more efficient coagulant 

for water filtration than the more commonly used ferric chloride or aluminum sulfate by 

up to three orders of magnitude33

To better address these challenges, a paradigm shift is needed in the conventional understanding 

of the fluid–solid interface, away from continuum-solvent descriptions and hypothetical 

interfacial structures, toward a quantitative, fully dynamic, and chemically realistic description of 

the interactions of electrons, atoms, and molecules that give rise to macroscopic fluid/solid 

interfacial properties. New experimental (e.g., high-intensity neutron scattering34

 

32 Curti, E., K. Fujiwara, K. Iijima, J. Tits, C. Cuesta, A. Kitamura, M.A. Glaus, W. Müller. “Radium uptake during 

barite recrystallization at 23 ± 2 °C as a function of solution composition: An experimental 133Ba and 226Ra tracer 

study.” Geochim. Cosmochim. Acta, 74, 2010: 3553-3570.

) and 

33 Stewart, T. A., D.E. Trudell, T.M. Alam, C.A. Ohlin, C. Lawler, W.H. Casey, S. Jett, M. Nyman. “Enhance water 

purification: A single atom makes a difference.” Environ. Sci. Technol., 43, 2009: 5416-5422. 34 Kumar, N, P.R.C. Kent, A.V. Bandura, J.D. Kubicki, D.J. Wesolowski, D.R. Cole, J.O. Sofo. “Faster proton 

transfer dynamics of water on SnO2 compared to TiO2.” J. Chem. Phys., 134, 044706. 
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computational (e.g., metadynamics35) techniques of fluid–solid interfaces put this paradigm shift 

within sight. 

However, there is a critical need to address the fundamental gaps in our current understanding of 

interfacial systems and answer these questions of high importance to future energy technologies: 

• How does the interfacial region differ in structure, dynamics, and reactivity from the bulk 

properties of the fluid and solid phases? 

• How do these altered properties couple with complex interfacial textures to influence 

chemical reactions, ionic and molecular transport, and charge transfer within and across 

the interface? 

• How can we control and manipulate interfacial phenomena by informed selection of 

fluid- and solid-phase components, interfacial geometries, field gradients, temperature, 

pressure, and other environmental parameters? 

These questions, some of which also pertain to liquid–liquid interfaces, permeate the 

fundamental science needed to solve our nation’s long-term energy production, storage, and 

utilization needs, as described in nearly all of the DOE/BES Basic Research Needs and Grand 

Challenge reports. 

2.3.3 Inorganic Ion-Exchange Materials

Inorganic crystalline oxide materials (e.g., zeolites, molecular sieves, clays, etc.) have chemical, 

mechanical, and thermal stability that is essential for a number of nuclear-related separation 

applications. In general terms, separation selectivity is determined by a combination of ion or 

molecule sorption to pore, chemical bonding inside of pore, and surface interactions between 

ion/molecule and solvent (e.g., water). Undertaking structure-property relationship studies on 

nanoporous materials that are selective for ions or molecules provides information as to why 

their bulk selectivity works. This information is then utilized to tune or design novel, optimized, 

and improved separations materials that have high selectivity with high capacity. Additional 

challenges arise in tailoring materials for stability and functionality in aggressive media, such as 

at the extremes of acidity or alkalinity. Moreover, pore structure holds the key to design of 

materials with adequate kinetics, down to nanometer dimensions. 

This is a technical area that can scientifically support fundamental to applied research and the 

commercialization of products to be used in environmental cleanup, commercial fuel 

reprocessing, and detection/sensing systems for NNSA applications. Target ions and molecules 

of interest for EM, NE, and NNSA are very similar, such as cesium, strontium, volatile FPs 

(

129I2, 85Kr, 14C[CO2], 3

H), and lesser actinides. 

 

35 Stack, A. G., P. Raiteri, J.D. Gale. “Accurate rates of the complex mechanisms for growth and dissolution of 

mineral using a combination of rare-event theories.” J. Am. Chem. Soc., Published on Web, July 1, 2011. 
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The ability to design a separation material for high selectivity, but also for easy processing, into a 

durable waste form is highly valuable for NE and EM applications. Targeting waste forms as 

natural mineral analogs allows for predictive extrapolation of waste form durability. Therefore, 

advanced planning from the separations stage helps plan for waste form and possible repository 

needs. Examples of successes in this area are seen in CST for Cs+ conversion to pollucite,36 and 

Sandia octahedral molecular sieves (SOMS) for Sr2+ to perovskite37 and iodate/iodide (aq) to BiO-I minerals.38

2.3.4 Inorganic Membrane Materials

The synthesis and testing of inorganic zeolite membranes have been intensely studied because of 

their potential applications in the domains of gas separation, pervaporation, and reverse osmosis, 

as well as in the development of chemical sensors and catalytic membranes.

39,40,41,42,43

Specifically, researchers are developing new technologies, such as zeolite membranes, for ion 

separations in aqueous solutions. A successful membrane for the separation of radiological ions

from ion mixtures must have both high flux and high selectivity. Inorganic membranes, which 

have good thermal stability and chemical inertness, are highly attractive. Distinctively, zeolite 

membranes combine pore size and shape tunability with the inherent mechanical, thermal, and 

chemical stability necessary for long-term separations. The effective pore size distribution, and 

hence the separation performance, of a defect-free zeolite membrane is intrinsically governed by 

the choice of the zeolitic phase.

44,45,46,47

Membrane development for EM, NE and even NNSA needs might include 1) development of 

microporous zeolite and clay membranes for efficient ion selectivity in water with a wide range 

of salt concentrations, 2) understanding of the mechanisms of ion transport in the membranes 

and the effects of microstructure and material properties on separation performance for guiding 

membrane improvement and process optimization, 3) evaluation of the membranes for treating 

 

36 Balmer, M.L.; Bunker, B. C. “Waste Forms Based on Cs-Loaded Silicotitanates”, Pacific Northwest Laboratory, 

PNL-SA-26071, 1995. 37 Nyman, M., A. Tripathi, J.B. Parise, R.S. Maxwell, T.M. Nenoff. “Sandia Octahedral Molecular Sieves (SOMS): 

Structural Effects of Charge-Balancing the Heteroatomic-Substituted Framework.” J. Amer. Chem. Soc., 124(3), 

2002: 1704-1713. 38 Krumhansl, J.L. and T.M. Nenoff. “Hydrotalcite-like Layered Bismuth-Iodine-Oxides as Waste Forms.” Applied 

Geochemistry, 26(1), 2011: 57-64. 39 Armor, J. N. J. Membr. Sci. 1998: 147, 217. 

40 Caro, J., M. Noack, P. Kolsch, R. Schafer. Microp. Mesop. Mat. 2000: 38, 3. 41 Nenoff, T. M., C.M. Aberg, R.J. Spontak. MRS Bulletin: Membranes for H2 Purification, 31(10), 2006: 735-741. 42 Ockwig, N.W. and T.M. Nenoff. Chem. Rev., 107, 2007: 4078-4110.

43 Snyder, M. A. and M. Tsapatsis. Angew. Chem. Int. Ed. 46, 2007: 7560-7573. 44 Vroon, Z.A.E.P., K. Keizer, M.J. Gilde, H. Verweij, A.J.J. Burggraaf. Membr. Sci., 113, 1996: 293.

45 Geus, E.R., M.J. DenExter, H.J. van Bekkum. Chem. Soc. Faraday Trans. 88, 1992: 3101.

46 Bakker, W. J. W., F. Kapteijn, J. Poppe, J.A. Moulijn. J. Membr. Sci. 117, 1996: 57. 47 Bai, C., M.D. Jia, J.L. Falconer, R.D. Noble. J. Membr. Sci. 105, 1995: 79.7.
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O

N N

O

radioactive water ion mixtures, and 4) ability to grow selective membranes on sensor platforms 

(fiber optics, surface acoustic wave [SAW] devices, etc.) for selective, ultra-sensitive and highly 

accurate responses. 

2.3.5 Polymer-Supported Complexants

Structural nature: The application of IX resins to metal ion separations is well known. However, 

the polymers now being developed for metal ion separations operate with mechanisms that are 

not solely IX; therefore, the more general term “polymer-supported complexants” is recommended. 

The polymers are often crosslinked and so may be used in continuous operations within columns; 

they may also be uncrosslinked in order to be water-soluble, and separations are then achieved 

when their use is coupled to ultra-filtration membranes. The chemistry of the functional group, 

and hence the separations achieved, is identical in both methodologies. This discussion will 

focus on issues involving crosslinked polymers, since they offer a simple mode of operation. 

The organic materials that form the basis of polymer-supported reagents are, most often, 

polystyrene or poly(glycidyl methacrylate), with the former being more versatile than the latter. 

Phenol-formaldehyde polymers can be used but under more limited conditions. Polypropylene 

has been underutilized but offers a distinct advantage in achieving rapid rates of loading. A 

principal reason for the importance of polystyrene is that it can be prepared in the form of beads 

of a size appropriate for loading into a column for largescale separations. Its formation from styrene via 

suspension polymerization is a well-known industrial 

process. The polymers are crosslinked with 

divinylbenzene in order to maintain insolubility in the 

functionalization reactions and the final application. The 

functionalization reactions covalently bond the ionselective ligand onto the polymer support. The choice of 

the ligand is central to achieving the targeted separation. 

Once loaded with metal ions, the polymer beads can be stripped with an aqueous-based eluent, 

thus making the polymer-supported complexant regenerable, re-usable, and environmentally 

compatible. Additionally, polystyrene is not limited to being utilized as beads: the 

immobilization chemistry remains the same when polystyrene is grafted onto another polymer, 

such as polypropylene, that can be fabricated as a membrane. 

Polymer-supported complexants: A wide array of ligands has been immobilized onto polymer 

supports and their metal ion affinities quantified through their distribution coefficients. The 

examples that follow illustrate only a few of the functional groups being studied for actinide and 

lanthanide separations.48

 

48 The examples presented are from a review: Yang, Y. and S.D. Alexandratos. “Affinity of Polymer-Supported 

Reagents for Lanthanides as a Function of Donor Atom Polarizability.” Ind. Eng. Chem. Res, 48, 2009: 6173–6187. 

All references may be found therein.

Bulky tetraalkylmalonamides have a greater affinity for U(VI) than 
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N

H

N

OH

Th(IV) due to hindrance from the alkyl chains towards complexation of Th(NO3)4. Organophosphorus 

acids play a central role in SX chemistry, and they have important properties once immobilized onto 

polystyrene. In one example, high affinity for U(VI) was obtained at low acidities due to a dual cation 

exchange/chelating mechanism: phosphoryl and carbonyl moieties chelate the uranyl ion, while the 

phosphinic acid stabilizes the complex through IX. Carbamoylmethylphosphonates and 

carbamoylmethylphosphine oxides, coordinating complexants known to extract transuranic elements in 

the TRUEX process, have been immobilized and shown to have affinity for Ce(III), Eu(III), and 

Yb(III). Polyamino/ polycarboxylic acids such as diethylenetriamine-pentaacetic acid, hydroxamic 

acids, and hydroxyquinolines form stable chelates with trivalent lanthanides and actinides and are 

examples of ligands with oxygen and nitrogen donor atoms. 

Quinoline-8-ol, in which the pyridyl nitrogen and phenolic –

OH groups chelate metal ions, has been bound to polystyrene 

and found to have a high affinity for U(VI) over Th(IV) and 

La(III).

Uranium from seawater: The problem of recovering uranium from seawater is an important 

targeted application that encapsulates all of the issues relevant to metal ion separations. The 

solution is highly dilute; there is a large excess of competing ions; and the uranyl ion is present 

in the form of a complex with a high stability constant, all of which limit the choice of functional 

groups to one that is highly selective for UO2

2+. Additionally, its removal from a huge body of 

water makes the final form in which the ion-selective polymer will be applied particularly 

challenging, as does the fact that the process must be completely compatible with the 

environment. Attention has been focused on the amidoxime ligand, which is easily prepared 

from polyacrylonitrile. However, despite decades of research and impressive progress, a process 

has not yet been developed that is ready for routine operation. Research is needed into additional 

ligands and new platforms to deploy the final polymer. The most promising avenues to be 

explored include diphosphonic acids as the ion-selective ligand and novel methods of 

functionalizing polypropylene since it can be utilized as a mesh that will operate passively within 

the ocean currents. Additionally, what is learned here will be applicable to a wide range of 

separations, including those in environmental remediation. 

Issues to be addressed in designing ion-selective polymers for DOE-relevant separations: 

Through an analysis of metal ion distribution coefficients from research with both soluble and 

immobilized complexants, four factors have been identified that affect ion–ligand affinities most 

significantly: 1) the basicity or polarizability of the ligand as compared to the acidity or 

polarizability of the ion, 2) the solution pH and its effect on protonation of the ligand, 

3) association of the metal ion with counterions in solution, and 4) the affinity of the ion for its 

waters of hydration. 

In designing a program with organic materials that will meet DOE needs for targeted separations 

involving actinides (and the rare earths as well as environmental remediation), the general issue 
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that must be addressed is the need for ligands that are relatively easy to prepare on polymers that 

achieve rapid rates of loading. 

The data suggest that polystyrene-based organophosphorus acids offer the greatest potential for 

the design of ion-selective resins because of the following characteristics: 

• They are readily immobilized on polystyrene. 

• They can be prepared proximate to a variety of auxiliary groups that influence 

polarizability and hence tune their affinity toward the targeted separation. 

• The diphosphonates are excellent chelants with high affinities for hexavalent ions over a 

wide range of solution pH values. 

• They can be prepared proximate to a sulfonic acid ligand that enhances the polymer’s 

hydrophilicity and leads to rapid rates of metal ion complexation since the ion does not 

need to lose its waters of hydration in order to enter the polymer microenvironment. 

Moreover, expanding the program to include optimization of grafting reactions onto 

polypropylene broadens the applications to membranes that can be prepared with high surface 

areas and thus rapid rates of loading. 

2.3.6 Neoteric Media

Despite the demonstrated effectiveness of SX processes employing conventional organic diluents 

in nuclear fuel reprocessing and nuclear waste treatment,49,50 there has been a growing interest in 

the possibilities afforded by less conventional alternatives. In large measure, this interest has 

been driven by the increasing appeal of processes exhibiting both high efficiency and selectivity 

and minimal environmental impact, a combination of characteristics not readily obtained with 

traditional extraction systems, which are frequently characterized by the use of toxic, volatile, or 

flammable diluents. Nash51 and others52 have noted that any of several “unconventional” 

systems, in particular aqueous biphases,53 solid sorbents incorporating supported extractants,54

 

49 Horwitz, E.P., W.W. Schulz. “Solvent extraction in the treatment of acidic high-level liquid waste: Where do we 

stand?” Metal Ion Separation and Preconcentration: Progress and Opportunities. A.H. Bond, M.L. Dietz, and R.D. 

Rogers, Eds. American Chemical Society, Washington, DC, 1999: 20-50. 50 Dietz, M.L. and E.P. Horwitz. “Combining solvent extraction processes for actinide and fission product 

separations.” Science and Technology for Disposal of Radioactive Tank Waste. W.W. Schulz and N.J. Lombardo, 

Eds. Plenum Press, New York, 1998: 231-243. 51 Nash, K.L., G.J. Lumetta, S.B. Clark, J. Friese. “Significance of the nuclear fuel cycle in the 21st century.” 

Separations for the Nuclear Fuel Cycle in the 21st Century. G. J. Lumetta, K. L. Nash., S. B. Clark, and J. I. Friese, 

Eds. American Chemical Society, Washington, DC, 2006: 3-20. 52 Wai, C.M., A.S. Gopalan, H.K. Jacobs. “An introduction to separations and processes using supercritical carbon 

dioxide.” Supercritical Carbon Dioxide: Separations and Processes. A. S. Gopalan, C. M. Wai, and H. K. Jacobs, 

Eds. American Chemical Society, Washington, DC, 2003: 2-8. 53 Huddleston, J.G., S.T. Griffin, J. Zhang, H.D. Willauer, R.D. Rogers. “Metal ion separations in aqueous biphasic 

systems and using aqueous biphasic extraction chromatography.” Metal Ion Separation and Preconcentration: 

Progress and Opportunities. A.H. Bond, M.L. Dietz, and R.D. Rogers, Eds. American Chemical Society, 

Washington, DC, 1999: 79-100.
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supercritical fluids (particularly supercritical carbon dioxide, SC-CO2),55 or ionic liquids (ILs),56

may ultimately provide a viable alternative to traditional, aqueous-based actinide and FP 

separations. At present, however, the need for high salt concentrations to generate a biphase, 

while acceptable in analytical applications, argues against the utility of aqueous two-phase 

systems for many large-scale separations.57 Similarly, despite attempts to improve the physical 

stability of solid-supported extractants,58,59 their suitability for process-scale applications 

remains questionable. In contrast, both SC-CO2 and ILs, certain drawbacks notwithstanding, 

appear to offer promise as the basis for new separation schemes for actinides and FPs.

Of these two classes of so-called “neoteric”60 solvents, supercritical fluids by far constitute the 

more thoroughly explored “non-traditional” approach to actinide and FP separations, both in 

terms of the development of workable technology and an examination of the underlying 

chemistry. It has been known for nearly two decades, in fact, that under appropriate conditions, 

complexes of various metal ions, including those of interest in nuclear applications, can be 

extracted into SC-CO2.

61

• Does fluorination represent the most effective strategy for ensuring adequate solubility of 

extractants and extracted metal complexes in SC-CO

 In spite of this, a number of important fundamental and applied 

questions regarding their use remain unanswered, among which are the following: 

2

• Does the introduction of silicon-based functional groups into an extractant, which has 

been demonstrated as a means of improving the SC-CO

? 

2 solubility of one class of 

extractants (i.e., alkylenediphosphonic acids),62

• Might increased attention to the design and use of phase modifiers obviate the need for 

extractant functionalization?

represent a “generic” alternative?

 54 Dietz, M. L. “Recent progress in the development of extraction chromatographic methods for radionuclide 

separation and preconcentration.” Radioanalytical Methods at the Frontier of Interdisciplinary Science. C. Laue and 

K. Nash, Eds. American Chemical Society, Washington, DC, 2004: 161-176. 55 Wai, C. M., B. Waller. Ind. Eng. Chem. Res. 39, 2000 : 4837. 56 Dietz, M. L. Sep. Sci. Technol. 41, 2006 : 2047.

57 Nash, K.L. “Twenty-first century approaches to actinide partitioning.” Separations for the Nuclear Fuel Cycle in

the 21st Century. G. J. Lumetta, K. L. Nash, S. B. Clark, and J. I. Friese, Eds. American Chemical Society, 

Washington, DC, 2006: 21-40. 58 Alexandratos, S.D. and K.P. Ripperger. Ind. Eng. Chem. Res. 37, 2998: 4756.

59 Dietz, M.L., E.P. Horwitz, A.H. Bond. “Extraction chromatography: Progress and opportunities.” Metal Ion 

Separation and Preconcentration: Progress and Opportunities. A.H. Bond, M.L. Dietz, and R.D. Rogers, Eds. 

American Chemical Society, Washington, DC, 1999: 234-250. 60 Seddon, K. R. Kinetics and Catalysis 37, 1996: 693. 61 Laintz, K.E., C.M. Wai, C.R. Yonker, R.D. Smith. J. Supercrit. Fluids, 4, 1991: 194. 62 Dietz, M.L., D.R. McAlister, D. Stepinski, P.R. Zalupski, J.A. Dzielawa, R.E. Barrans, Jr., J.N. Hess, A.V. Rubas, 

R. Chiarizia, C. Lubbers, A.M. Scurto, J.F. Brennecke, A.W. Herlinger. :Recent Progress in the Development of 

Supercritical Carbon Dioxide-Soluble Metal Ion Extractants: Solubility Enhancement through Silicon 

Functionalization.” Nuclear Waste Management: Accomplishments of the Environmental Management Sciences 

Program, T. Zachry, Ed. American Chemical Society, Washington, DC, 2006: 250-267.
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• Given that the stated purpose of employing SC-CO2

• Is any process for nuclear separations requiring that high pressures (e.g., 72.9 atm. in the 

case of SC-CO

 as a substitute for a conventional 

organic solvent is to devise nuclear separation processes that are more environmentally 

benign, can the ancillary processes associated with its use (e.g., extractant recycle) also 

be rendered “greener”?

2) be maintained really viable? 

Fundamental questions remain unanswered to an even greater extent for ILs, a relatively new 

and, in many respects, remarkable class of solvents that have attracted enormous recent interest 

in a variety of applications, among them nuclear separations.8

 Consideration of the unique 

physicochemical properties of these solvents, which typically include a near-absence of vapor 

pressure, the ability to dissolve a wide variety of solutes, and an extraordinary degree of thermal 

stability, make their appeal in this application readily apparent. Adding to their attractiveness as 

prospective extraction solvents is the observation that under certain conditions, they can provide 

extraction efficiencies far exceeding those seen with conventional organic solvents.63 A number 

of recent investigations, however, have shown that this increased efficiency frequently comes at 

the cost of added system complexity. When a neutral extractant is employed with a conventional 

organic diluent, for example, the extent of extraction of the metal ion of interest is readily 

controlled simply by changing the aqueous phase anion concentration, as partitioning of a neutral 

metal complex represents the pathway by which extraction occurs. This is frequently not the case 

for the same extractants in ILs, however, which have been found to function as liquid cation-64 or 

anion-exchangers65 in addition to process solvents, thereby complicating the recovery of 

extracted metal ions. Adding to the difficulties in applying ILs as extraction solvents is the 

recognition that complexes not observed in conventional systems may predominate in ILs, 

further complicating the development of extraction processes based upon them. 

Such observations raise a number of significant questions that must be addressed if ILs are ever 

to provide a basis for viable large-scale separations, among which are the following: 

• What processes are involved in the transfer of a metal ion from an aqueous phase into an 

IL in the presence of various types of extractants, and how can the balance among these 

processes be controlled?

• To what extent can the behavior of ILs as separations media be understood on the basis of 

the behavior of conventional separation systems? 

• How are the various structural features of ILs related to their performance and utility as 

media for separations?

 

63 Dai, S., Y.H. Ju, C.E. Barnes. J. Chem. Soc., Dalton Trans. 1999: 1201.

64 Dietz, M. L. and J.A. Dzielawa. Chem. Commun. 2001: 2124. 65 Jensen, M. P., J. Neuefeind, J.V. Beitz, S. Skanthakumar, L. Soderholm. J. Am. Chem. Soc. 125, 2003: 15466.
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• Is it possible to develop guiding principles for the rational design of IL-based separation

systems?

All of these questions, as well as those posed for supercritical fluids, touch upon a number of 

broader issues, which constitute “grand challenges.” Most notable among these are the 

following: 

• Can molecules and materials (here, solvents) be designed to have predictable properties? 

• What is the nature of the interactions of the matrix components with the species of 

interest in a separation?

• Can the structure of complexes and the thermodynamics of complexation processes 

involving small donor molecules be predicted in these new media?

Only by answering such questions will the full potential of novel media such as supercritical 

fluids and ionic liquids in nuclear separations be realized. 

2.3.7 Decorporation Agents

Accidental or inadvertent intake of radionuclides from occupational exposure or environmental 

exposure is a primary DOE concern. The recent Fukushima Daiichi nuclear disaster, the largest 

nuclear accident since Chernobyl, resulted in the release of large amounts of radioactive 

materials into the environment. It highlighted the pressing need for the interventional therapies to 

mitigate the health effects of the internal contamination potentially with multiple radioisotopes. 

In addition, acknowledged threats involving the potential deliberate release of radionuclides into 

local environments by terrorists now prompt new concerns and the need for improved methods 

of removing internally deposited radionuclides; these include chelation therapy, blocking uptake, 

and accelerating the clearance of ingested or inhaled radionuclides from the body. Effective 

chelation therapy after internal contamination has been shown to reduce the radiation dose, 

radiation effect consequences, and in some cases the chemical toxicity associated with internally 

deposited radionuclides. To date, only a few standard treatments are available for certain 

radionuclide intakes. Intelligent design of the new decorporation agents will address the 

DOE/Department of Homeland Security/Department of Defense/Department of Health and 

Human Services need for effective, selective, orally active, non-toxic, and cost-efficient 

sequestering agents. 

The radionuclides likely associated with nuclear accident and terrorist activities exhibit 

drastically different chemical and biological properties, depending on their nature, and can be 

categorized as follows:

• Group 1. Alkali metal ions: 137

• Group 2. Alkaline earth metal ions: 

Cs

90Sr and 226

• Group 3. Transition metals: 

Ra

60Co, 90Y, and 192Ir
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• Group 4. Actinide metals: 241Am, 238/239Pu, and 238/235/234

• Group 5. Metalloids and mon-metals: 

U 

210Po, 32P, and 129/131I 

Radioactive elements of military concern include enriched and depleted uranium, plutonium, 

tritium, and radium. In addition, misuse or overdose of the nuclear medicine diagnostic agents, 

such as 99m Tc, 99Mo, 111In, and 125/131I, is of concern. 

Effective chelation therapy using diethylenetriaminepentaacetic acid (DTPA) has been shown to 

reduce the consequences of radiation effects associated with internally deposited transuranic 

radionuclides. Properties of the DTPA sequestering agents are summarized in Table 4. Even 

though CaDTPA has demonstrated high efficacy when administered intravenously within a few 

hours of actinide intake, it cannot be used for prolonged treatments because it depletes essential 

biological metal ions from the patients. ZnDTPA has lower toxicity and can be administered 

over long periods of time at small doses, but is less effective as an immediate post-contamination 

treatment. DTPA agents have short residence time in the human body and are quickly excreted, 

exhibit limited biokinetics, and do not access intracellular and bone deposits of actinides. 

Similarly, hydroxypyridinonate (HOPO) ligands have been shown to be potent chelators for 

plutonium decorporation.66

http://www.fda.gov/Drugs/EmergencyPreparedness/BioterrorismandDrugPreparedness/ucm0638

07.htm

 To this end, a number of HOPO ligands have been tested in vivo, and 

selected candidates are currently in pre-clinical studies. Only a few other standard treatments are 

available, such as potassium iodide for 131I and Prussian Blue (ferric hexacyanoferrate (II)) for

137Cs. Details of these drug therapies for radiation emergencies can be found at 

. 

To date, no effective therapies are known for other radionuclides, although it is apparent that 

different groups of radionuclides will require different synthetic receptors possessing specific 

functional groups. Often chelators with demonstrated strong in vitro affinity to the specific metal 

ions are unsuitable for the in vivo applications due to the high toxicity, fast metabolism, inability 

to effectively remove a radionuclide from the target organ, or other reason. To this end, 

availability of decorporation agent design methodology targeting the in vivo chelators that not 

only exhibit high decorporation efficacy but also possess properties compatible with the living 

organism is of paramount importance to accelerate development of intervention therapies for 

internal contamination.

Regardless of the route of radionuclide uptake (inhalation, ingestion, or wound), the radionuclide 

is systemically absorbed at a rate that depends upon the physicochemical form of radionuclide 

and its solubility in biological fluids, and transported by blood to the target organs (e.g., bone, 

kidney, liver, etc.). The behavior of a radionuclide in a living organism is controlled by the 

kinetics and thermodynamics of equilibrium processes, such as the interaction of the 

 

66 Gorden, A.E.V., J. Xu, K.N. Raymond, and P. Durbin. “Rational Design of Sequestering Agents for Plutonium 

and Other Actinides.” Chem. Rev., 103, 2003: 4207-4282.
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Table 4. Overview of DTPA decorporation properties 

a. Gerber, G.B. and RG Thomas. "Guidebook for the Treatment of Accidental Internal Radionuclide Contamination 

of Workers." Chapter 6, Methods of Treatment. Radiat Prot Dosimetry, 41, 1992: 27-36.

b. Gorden, A.E.V., J. Xu, K.N. Raymond, and P. Durbin. “Rational Design of Sequestering Agents for Plutonium 

and Other Actinides.” Chem. Rev., 103, 2003: 4207-4282.

c. Guilmette, RA, A. Hakimi, P.W. Durbin, J. Xu, and K.N. Raymond. “Competitive binding of Pu and Am with 

bone mineral and novel chelating agents.” Radiat. Prot. Dosimetry, 105, 2003: 527-534.

d. Ramounet B., S. Matton, G. Grillon, J.L. Poncy, and P. Fritsch. “Efficacy of Localised DTPA Treatment for 

Decorporation of Np Injected Intramuscularly as Np(IV) or Np(V).” Radiat. Prot. Dosimetry, 79, 1998: 463-465.

e. Taylor, D. M., G. N. Stradling and F. Menetrier. “Biokinetics of radionuclides and treatment of accidental 

intakes.” Radiat. Prot. Dosimetry, 105(1-4), 2003: 637-640.

radionuclide with the biological ligands. Understanding the speciation and solution chemistry of 

the radionuclide in vivo is the critical pre-requisite to predict toxicity and to design a successful 

decorporation agent. For computing binding affinities and dominant speciation of the 

radionuclide, in vivo thermodynamic constants are needed for its complexation with inorganic 

Property DTPA

Mode of action Chelation

Chemical functionality Polyaminocarboxylic acid

Biological properties N/A

Toxicity Toxic, toxicity reduces in order DTPA > CaDTPA > ZnDTPA, DTPA being 

acutely toxic.b

Target radionuclides Soluble species of tri- and tetravalent actinides and lanthanides, Co, Mn, Zr, 

Ru. Cannot be used for uranium contamination.a Does not bind Np(V).c Not 

strong enough to solubilize and bind hydrolyzed transuranic elements and 

subsequently formed colloids and polymers.

Efficacy Overall high for isotopes of Pu, Am, Cf, Cm. Very efficient when administered 

within minutes of radionuclide intake. Efficacy rapidly drops within few days 

after the event of internal contamination.

Length of treatment CaDTPA can be used only in early treatment up to few days because of its 

toxicity. ZnDTPA can be systemically used for several years.

Biokinetics Does not penetrate intestinal epithelium. Being highly hydrophilic, DTPA agents 

distribute only in extracellular water and cannot interact with intracellular 

actinide deposits.e Unable to remove radionuclides from the bone.c 

Administration Intravenous injection, infusion, or inhalation. Local infiltration in wounds. Oral 

administration is inefficient and is considered only for long-term ZnDTPA 

treatment.d

Contraindications Kidney, liver, intestinal, haemopoietic disorders. Pregnancy. Not recommended 

for children.

Availability Commercially available. Distributed through the national stockpile. Not 

generally available, particularly in large quantities.
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ligands (e.g., hydroxide, carbonate, phosphate), small organic chelators (e.g., lactate, citrate, 

etc.), and large biological molecules such as amino acids, proteins, carbohydrates, peptides, and 

other. In addition, the design of the decorporation agents should incorporate consideration of 

toxicity and overall safety. Briefly, requirements for an effective emergency decorporation agent 

include the following:67

• High affinity and selectivity toward target multiple radionuclides 

• Low toxicity 

• High oral activity

• Ability to permeate cell membranes to achieve effective concentration at the site of 

radionuclide deposition in the target organ 

• Ability of metabolites of the chelation agent to retain binding capacity for the 

radionuclides 

• Availability for safe, convenient, and rapid distribution in large quantities to the general 

public 

• Application for both medical mitigation and prophylactic purposes in the event of a 

nuclear emergency: no additional harm induced 

3. OPPORTUNITIES FOR CROSSCUTTING RESEARCH AND 

PROGRAM PARTNERSHIPS 

3.1 Summary of Opportunities for Program Partnerships and 

Role of Science 

Program partnerships: Drawing from the discussion of technology needs (Section 1.4 of this 

breakout session report), this section identifies key overlaps among EM, NE, and NNSA 

programs to find potential opportunities for program partnerships. Due to the challenges in 

developing new technologies, success will depend on a partnership between fundamental science 

conducted by the DOE Office of Science (SC) and applied science 

conducted within EM, NE, NNSA, and other agencies both internal and 

external to DOE. 

DOE has recently adopted a model for technology maturation from 

discovery science through a series of “gates” to higher technology 

readiness levels.68

 

67 Taylor, D. M., G. N. Stradling and F. Menetrier. “Biokinetics of radionuclides and treatment of accidental 

intakes.” Radiat. Prot. Dosimetry, 105(1-4), 2003: 637-640.

 Although this model has proven to be a valuable tool 

68 DOE. “Technology Readiness Assessment Guide,” DOE G 413.3-4, 2009.
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in evaluating actual technology readiness for deployment or for advancing to the next stage of 

development, its linearity is not a useful construct for the purpose of visualizing and managing 

the essential interplay between fundamental science and technology development. Rather, in 

addressing the myriad diverse technical hurdles summarized in Table 2, applied technology 

development must continually employ fundamental understanding and often create new 

fundamental understanding. As the system complexity increases during scale-up, system 

integration, and demonstration with real process solutions, the chance for discovery and 

corresponding role for science actually increases. Therefore, the formula for success is a strong 

and continuing presence of science throughout the technology-maturation process.

In view of the real role of science in technology development, the graphic below summarizes 

eight areas for potential program partnerships drawing from a core of fundamental science. At 

the core is theory, modeling, and simulation, entailing both use of and development of directed 

computational design tools, which is a major opportunity for program partnership in itself. These 

tools are then used in a design method that must satisfy a series of process needs for optimal 

molecular or material properties, such as selectivity, rapid kinetics, and stability (see Table 2). 

In the rest of Section 3, the elements of the identified opportunities for program partnerships in 

the figure below are discussed in greater detail.

Opportunities for program partnerships incorporating a central role for science in the 

design of molecules and materials for the development of new separation processes 
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 Table 5. Table of matrices of interest in nuclear separations 

Area of Interest Program

EM NE NNSA DoD DHS

Human body X X X X

Soil and groundwater X

Building materials X X X

Gas streams X X X

Tank waste X

HLW/aqueous X X X

Low-level solid waste X X

UNF X X X

Molten salts X X X

Ore X X

Seawater X X

3.2 Overlaps in Programmatic Needs Related to Design of 

Molecules and Materials 

Overlaps in programmatic needs can be identified by examining common matrices that must be 

treated in the separation process or by examining the common species that are targeted for 

separation. Table 5 lists the various media of interest in separations or in analysis. The media 

range from the human body to used nuclear fuel (UNF) to specific types of wastes, off-gas, 

process media, ore, and soils. For each matrix, the programs are listed that have significant stake 

in technology 

development. Some 

matrices, such as tank 

waste or soils, are 

primarily of interest to EM, 

while others, such as gas 

streams, reprocessing 

streams (e.g., HLW), and 

UNF, have broad 

overlapping interest. 

Similarly, Table 6 (next 

page) identifies program 

overlaps in species targeted 

for separation, as gleaned 

from Section 4 of the main 

body of this report. It is 

presumed that SC has 

underlying fundamental 

impact on, and interest in, 

all of the matrices and 

targeted species identified 

in the two tables. 

3.3 Crosscutting Computational Tools for Design of Molecules 

and Materials 

To advance modeling and simulation capabilities to the point where they can provide maximum 

benefit toward development of highly selective separations processes, sustained and coordinated 

efforts are needed that couple molecule generation on the computer, scoring algorithms, code 

development, and experimental data. Existing computational tools and methods should be 

evaluated for their applicability in deriving structure–function relationships that will allow for 

rapid screening to identify candidates with desired properties. The focus should be on enabling 
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the selection for experimental development and testing of candidate agents with characteristics 

that can be applied to separations and detection schemes of interest to EM, NE, and NNSA. 

Table 6. Table of target species for separations 

Area of Interest Program

EM NE NNSA DoD DHS SC

Actinides: U, Np, Pu, Am, Cm X X X

Volatiles: I, Tc, Cs, Xe, Kr, C, 3H X X X

Human body contaminants: U, Pu, Ra, 90Sr, 129,131I, 137Cs, 60Co X X X X 

Pyroprocessing/molten salt: U, TRUs, FPs X X X

99Tc and 129I as ubiquitous contaminants/risk drivers X X X

Mercury in groundwater, soil, building materials X X X

Cr(VI) in groundwater X

137Cs, 90Sr in tanks, soil, groundwater, building materials, off-gas X X X

Non-rads Al, Na, S, Cr, HNO3, Be, Zr, Pd X X

60Co in groundwater, equipment, RDD cleanup X X X 

Program partnerships could include the following relevant contributions:

Office of Science:

• Basic Energy Sciences 

o Relationship between molecular structure and physicochemical property

o Fundamental studies of interfacial phenomena, including transport 

o Fundamental studies of radiation stability 

o Self-assembly as an approach to molecular recognition

• Advanced Scientific Computing Research

o Translation of new approaches and algorithms for modeling and simulation of 

complex systems of interest (e.g., scaling, incorporation of quantum calculations) 

Office of Nuclear Energy/Office of Environmental Management: 

• Agent design improved by computational quantum chemistry and computational 

thermochemistry

• Applicability of MD simulations for preferential gas sorption, ion exchange predictions, 

molecular interfacial transport, speciation, and complexation thermodynamics

• Scaling of molecular models for macroscopic predictions of separation kinetics 

• Studies of relevant mechanisms in processes
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3.4 Opportunities for Crosscutting Research 

3.4.1 Design of Process Materials for Technetium and Iodine Capture

As highly mobile, long-lived FPs either as anions or gaseous species, 99Tc and 129I often occur 

together and contribute to long-term risk in similar ways. Therefore, they represent a dual 

problem for separation and analysis in many contexts. An opportunity exists to treat the two 

radionuclides in a program partnership, especially as they might be separated or analyzed 

together. It is envisioned that the partnership would seek first in a fundamental sense to 

understand the speciation of the radionuclides, as they can take on different oxidation states, and 

then to delineate appropriate principles for separations from common types of media (e.g., 

aqueous, gas, and surfaces). From these considerations, existing separation or analytical agents 

could be improved upon, or design methodology could create entirely new candidate materials. 

3.4.2 Separation Agents for Fission Products 90Sr and 137Cs

Like the dual problem of 99Tc and 129I, separations and analysis of the FPs 90Sr and 137Cs occur 

together in many contexts and thereby represent another opportunity for a program partnership. 

Unlike technetium and iodine, however, strontium and cesium exist as well-defined species in 

most cases (with notable exceptions, such as colloids). Thus, the approaches to separation and 

analysis may more often be similar; therefore, corresponding design methods for molecules and 

materials more straightforward. As an example of using a common binding agent, separation 

from HLW aqueous streams can be accomplished by crown ethers or calix-crowns as molecular 

binding agents in SX, whereas solid ion-exchange materials can be designed with the same 

crown ethers or calix-crowns as pendant functionalities. Although efficient separation methods 

exist for 90Sr and 137Cs in many types of media, the continued emergence of new problems (e.g., 

soil contamination in Japan) and the need for more efficient methods will drive research and 

development worldwide for decades to come. Both radionuclides are thought to be tempting for 

use in RDDs, making their detection and removal from building materials an important problem 

for future research. In general for NNSA applications, the opportunity reflects the simple need 

for detection ability with approaching 100% reliability. Finally, another driver lies in the 

expected efficiency gain in combined separations, either to separate just these two radionuclides 

or remove them with other radionuclides. 

3.4.3 Design of Decorporation Agents

A clear area of emphasis relevant to EM, NE, and NNSA is developing new reagents and 

materials for decorporation of radionuclides from personnel. The requirements for such reagents 

are high selectivity for the species of interest, high stability under biological conditions (which 

include media of approximately 0.5 M ionic strength, 37oC, and potentially pH ranging from 2 to 

10, though most of the important chemistry occurs near pH 7). The target species of concern 

include all of the most important radionuclides identified above plus selected nonradioactive 

materials (e.g., mercury). Due to the complexity of molecules that typically survive in biological 

systems and the systems in which they operate, the molecular design challenge is amplified by 
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the incomplete understanding of mechanisms of metal ion transport phenomena in biological 

systems. At the same time, there are clear linkages between the sorts of phase transfer 

phenomena that govern metal transport in biological systems, environmental media, and SX 

transport systems. Thus, any and all research will be crosscutting. 

3.4.4 Design of Binding/Transduction Agents for Detector/Sensing/Analysis

Development of improved materials for analysis, detection, or sensing applications is a major 

need common to the missions of EM, NE, and NNSA. A selective agent can be deployed to preconcentrate a solute to increase the sensitivity of an analytical method, or the selective agent can 

be coupled with a transduction method to directly provide a measure of the concentration of the 

solute. The applications range from “traditional” analytical chemistry methods, to on-line 

process monitoring for process control or safeguards, to rapid measurements in the field for 

environmental or personnel contamination and forensic determinations. 

Computational design of more selective separation agents is generally relevant in this 

crosscutting area, wherein molecular design must couple binding with a transduction function to 

directly signal the presence of target species. In some cases, this can be rather straightforward, as 

in the use of colorimetric agents to bind metal ions; and computational methodology can assist, 

for example, by predicting spectra of metal ions bound to a receptor site. In other cases, the 

attempt to develop a signal from a host-target system can be problematic. For example, 

chemically attaching a selective agent to a solid to allow a more convenient and robust platform 

for analysis can significantly alter the binding of a target species to the agent. 

3.4.5 Design of Separations Materials for Capture of Gaseous Species

Gaseous/volatile FPs (principally xenon, krypton, bromine, iodine, tritium, radiocarbon, and 

under some conditions technetium, cesium) represent a unique hazard in processing of UNF, as 

these species may be difficult to contain (due to low/no reactivity and the natural dilution 

associated with the solid-liquid-gas phase transfer process). Separation materials for gaseous 

species focus principally on sorbents that can selectively capture the targets from a multicomponent vapor phase. The potential environmental mobility of such species makes the 

identification of a stable waste form for long-term disposal a high priority. For some of these 

species, a combination of oxidation state manipulation, chemical reactivity, and size selectivity 

offers some promise for sequestration. The low chemical reactivity of the noble gases represents 

a more difficult challenge. Some of these species are similarly challenging waste management 

problems in pyrometallurgical processing of used fuel. 

3.4.6 Effects of Radiation and Design of Materials for High-Dose Conditions

Radiation damage is an unavoidable feature of any manipulation of radioactive materials. 

Molecular/materials design can contribute to the creation of more radiation-stable molecular 

arrangements, but because the energy deposited is typically adequate to break many bonds, it is 

not possible to design materials that are immune to radiation damage. Research on fundamental 

effects of ionizing radiation on the properties of complexing agents and separation materials has 
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been done to support the development of new separation processes as a feature of process 

optimization activities. Identified needs include systematic efforts that include data mining from 

existing resources, new experimental studies dedicated to process development and to increased 

fundamental understanding, and computational modeling to provide a robust understanding of 

mechanistic features. Improvement in this capabilities base will substantially aid reagent/material 

effectiveness and process applicability. Developing materials that have the potential to be selfhealing (or to “spontaneously” reverse the effects of free radical induced degradation) are 

interesting areas for investigation. Since radiation damage is a universal feature, these issues 

crosscut the interests of all DOE offices responsible for monitoring or handling radioactive 

materials. 

3.4.7 Separation Agents for Non-Radioactive Species

The suite of nonradioactive species relevant to DOE interests (aluminum, sodium, chromium, 

mercury, sulfur, phosphorus) must be considered to focus primarily on species of primary 

concern to EM. The unique chemistries associated with the separation of these species present a 

variety of uniquely challenging problems, as has been noted in the technology needs discussion 

of this document (Section 1.4.2, EM, Removal of non-radioactive species from high-level 

waste). As the interests of NNSA must address issues of misuse of radioactive materials in 

general, these species may be of some concern to this organization as well. In imagined 

application of chemical separations in advanced nuclear fuels cycles (of interest to NE), the 

species in this list of the greatest potential concern would be phosphate, which can exist in 

process effluents, though typically at much lower concentrations than are seen in EM tank 

wastes. Actinide-bearing waste forms based on phosphate have been suggested as potential waste 

forms for managing some wastes from advanced reprocessing schemes. 

3.5 DOE Center of Knowledge 

Although separation science and technology (SS&T) remains the foundation for energy 

technology development in the DOE complex, it is perhaps surprising that there is no current 

mechanism for DOE programs to coordinate and gain synergy from their similar but separate 

SS&T research activities. Supposing that common problems specifically associated with 

designing molecules and materials for selective separations could be addressed by pooling 

resources and expertise, it is expected that an overall more productive and efficient research 

enterprise would result. At present, any coordination that exists is happenstance, depending 

primarily on individual investigators seeking impact across programmatic lines on their own 

initiative. Further, no particular system for evaluating SS&T needs in a sustained manner exists 

within any DOE program. A litany of “research needs” documents produced in an ad hoc manner 

for at least two decades points to real programmatic needs and shows that there is a recurring, 

though fragmented, desire to evaluate these needs within individual programs. The next step that 

is needed is to coordinate this evaluation process, provide for a mechanism for sustaining it, and 

seek synergy in research efforts for the strongest possible impact through a DOE center of 

knowledge in “Molecular Design for Radioactive Material Separations.”
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In some respects, such a center of knowledge represents a “Back to the Future” movement, as 

there was once just such a virtual center of knowledge (arguably a center of genius, considering 

what was accomplished) in nuclear science and technology at the DOE national laboratories in 

this country. For a revitalization to occur, a virtual center of excellence that recognizes and 

expands upon the capabilities and talents within the DOE laboratory complex represents a 

rational approach. The computational resources that have been developed in recent years have 

advanced considerably, and although plant-scale molecular modeling is not yet possible, 

important capabilities are in place. Given the limited numbers of Ph.D. graduates being produced 

in this field in the United States, it is probably also important that the center of knowledge 

include a clear connection to, and involvement by, the academic community. 

For a successful re-invigoration of this field to occur, it is critically important that facilities for 

the handling of radioactive materials be maintained, improved/upgraded, and expanded. 

Molecular/material design can only proceed productively with closely coupled computational 

and experimental programs operating, sometimes in lock step, sometimes at cross-purposes 

(modeling activities should always be guided to some degree by the skeptics). Without 

experimental data, computational modeling can follow unproductive, unrealistic, or incorrect 

pathways that are not consistent with physical science/engineering technology. Molecular/

material design may be validated in some cases, at least initially utilizing nonradioactive analog 

systems (e.g., rhenium for technetium, lanthanides for trivalent actinides), but the ultimate 

validation requires experimental work with “the real stuff.” In this case, the real stuff is 

radioactive and so by definition demanding of special facilities like those existing at the national 

laboratories and a few select universities. This includes not just large-instrument “user facilities” 

but also laboratories wherein it is possible to work with radioactive materials at a wide range of 

concentrations, up to and including hot-cell facilities.

The primary vision for a DOE center of knowledge in molecular design is almost certainly a 

virtual center, located across the laboratory complex and including participants from academia 

and, as appropriate, from industry. A central “node” in this virtual center could possibly house 

centralized facilities and coordinating expertise to integrate activities across the complex. 

However, the strength of the virtual center is to enable the vast resources with the DOE complex 

and its affiliated research institutes to be brought to bear on the diverse needs for new molecules 

and materials for separations. This virtual center will thus include facilities and equipment 

dedicated to work with the radioactive materials, including but not limited to DOE user facilities 

and computational resources, but will focus most importantly on the scientific and technological 

interests of experts in the science and technology that supports the objectives of molecular 

design. The recovery of information “mined” from the open literature and non-classified 

government research reports maintained in an accessible database would minimize the loss of 

productive effort repeating quality work—and would represent a valuable resource. Many (but 

not all) of the large-scale resources (user facilities) are operated by the Office of Science; 

therefore, this Office’s participation in the center is a rational connection to be made. To the 
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extent practical, it may be advisable for the center to be in communication with international 

organizations similarly engaged, e.g., Europe’s Integrated Infrastructure Initiative for Actinide 

Science (Actinet), the Japan Atomic Energy Agency, and the International Atomic Energy 

Agency (IAEA). 

Building tomorrow’s workforce must also be a high priority, through the support of both 

academic institutions contributing to development of “isotope experts” and retraining Ph.D. 

scientists with explicit training in complementary fields but no direct experience with radioactive 

materials. Funding for sustained research projects commensurate with the typical duration of a 

Ph.D. thesis is needed to solve the current difficulty in involving academic research participation 

with short-term project funding. Access to the facilities of the center must be readily accessible. 

Establishment of an appropriate communication structure should also be a part of the plan. One 

opportunity for profitable linkages between the DOE laboratory centers and academic/industrial 

partners will arise in the area of organic/inorganic synthesis, neither of which is represented in 

depth within the existing DOE complex. Such activities do not necessarily demand direct access 

to radioactive materials handling facilities; they thus offer an opportunity for synthesis activities 

to be pursued without the considerable overhead represented by federal laboratory facilities. 

In summary, a center of knowledge is envisioned to provide a vehicle for solving real DOE 

separation problems in the most efficient manner possible, drawing upon the common interests 

and resources of diverse DOE programs. In terms of design of molecules and materials, the 

vision shown in the figure in Section 3.1 seeks to bring the tools of science to bear upon definite 

opportunities for program partnerships. The strength of the center concept lies in its instituted 

ability to coordinate, direct, and integrate materials design research and development into these 

opportunity areas.
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Appendix C. Breakout Session Report: Scale-up of 

Separation Processes from Bench-Top 

to Plant 

CHAIR: Robert Jubin, Oak Ridge National Laboratory 

CO-CHAIR: Raymond Wymer, Vanderbilt University

FEDERAL COORDINATOR: Nicholas Machara, Office of Environmental Management 

ORGANIZER: Terry Todd, Idaho National Laboratory 

PANELISTS:

Joseph Birdwell, Oak Ridge National Laboratory 

Phil Gauglitz, Pacific Northwest National Laboratory

Jack Law, Idaho National Laboratory 

John Marra, Savannah River National Laboratory 

Manuel Miguirditchian, Commissariat à l'énergie atomique

Candido Pereira, Argonne National Laboratory 

Tom Pfeiffer, Idaho Nuclear Laboratory 

Richard Taylor, National Nuclear Laboratory 

Mark Williamson, Argonne National Laboratory 

1.0 Introduction 

This working group focused on the scale-up issues facing the U.S. Department of Energy (DOE) 

Office of Nuclear Energy (NE), the DOE Office of Environmental Management (EM), and the 

National Nuclear Security Administration (NNSA) as they advance separations technology from 

the laboratory to plant scale to achieve their mission goals. This group attempted to identify areas 

of common need in terms of processes and time frames. In doing so, the group attempted to draw 

from past successes and lessons from across the DOE complex and from international nuclear 

industrial experience. The working group addressed certain key questions, including the 

following: 

• “What are the appropriate demonstration levels that must be considered?” 

• “What is learned at each step of the scale-up process?” 

• “What are the roles of modeling and simulation, and how and when can simulants be 

used?”
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Numerous areas of commonality were identified and potential opportunities for leveraging were 

noted, along with a need for the preservation of significant bodies of knowledge, expertise, and 

capabilities from across the DOE complex.

2.0 Needs 

2.1 NE Scale-up Needs

It is anticipated that a great deal of scale-up testing will be required to support NE fuel cycle 

separations in the future. The current focus of the Fuel Cycle Research and Development 

(FCR&D) Program is science-based, engineering-driven research to better understand potential 

separation processes as well as identify transformational technologies that could potentially 

reduce the cost and complexity of advanced processing facilities. As such, there is currently little 

effort focused on equipment scale-up to support NE. 

It is likely that one option for future used fuel separations facilities that process light water 

reactor (LWR) fuel will incorporate solvent extraction processes to some degree. Much of the 

equipment associated with solvent extraction processes in the nuclear industry is well understood 

with regards to scale-up as a result of the decades of experience operating the plutonium–

uranium extraction (PUREX) process in the United States and internationally. As advanced 

separation technologies are developed, however, the scale-up of these specific processes in 

solvent extraction equipment will be required. This is true regardless of whether pulsed columns, 

mixer-settlers, or centrifugal contactors are chosen. Data relative to throughput, efficiency, and 

hydrodynamic behavior of the solutions will be required and must be acquired using 

engineering-scale equipment, at a minimum. 

Processes that have not been implemented industrially, such as voloxidation and electrochemical 

systems, will require development of specific prototypic equipment and scale-up testing. This 

could involve engineering-scale testing with simulants and/or material derived from actual used 

fuel as well as mockup testing of full-scale equipment. The approach taken should build on past 

experience here in the United States, and international experience and approaches to scale-up of 

equipment and processes have been demonstrated to be relatively successful; the approach taken 

should build upon this experience, both positive and negative. If transformational technologies 

significantly different than current processing technologies are implemented, it is expected that a 

more rigorous effort to evaluate and understand scale-up issues will be required.

With regards to common areas of interest within NE, EM, and NNSA, there are challenges 

related to differences in the time frame planned for implementation of process equipment. EM is 

focused on short-term implementation to support cleanup, whereas NE FCR&D is focused on a 

long-term solution to the build-up of used nuclear fuel (UNF), perhaps a decade or two in the 

future. Nonetheless, there are several areas of potentially common interest, including centrifugal 

contactor design and operation, feed clarification, melter design and operation, and evaporator 

development. Modeling and simulation is also a common area of interest. For example, 
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computational fluid dynamics (CFD) modeling of centrifugal contactors is supporting centrifugal 

contactor design for NE and EM. Process modeling tools are also being used by NE, EM, and 

NNSA to support flowsheet development and material accountability studies. 

2.2 NNSA Scale-up Needs

Stated broadly, the mission of NNSA has four primary components (prior to transfer of the EM–

to-NNSA oversight): 

1. Management of the nation’s nuclear weapons stockpile 

2. Operation of the naval reactor program 

3. Nuclear nonproliferation and safeguards 

4. Oversight and coordination of the safe transport of weapons components 

Issues related to separations differ greatly between these focus areas. The fourth area (safe 

transport of weapons components) does not have the same kind of scaling issues as the other 

areas, inasmuch as it does not involve chemical processing. 

Rather than facing scale-up issues, the stockpile mission of NNSA may be more impacted by 

scale-down issues affecting component refurbishment and dispositioning tasks. This reflects 

decreases in required throughput due to the shift in mission from production in support of large 

(and sometimes expanding) inventories to treaty-mandated stockpile reduction (e.g., 

downblending and/or preparation for safe, monitored storage). Scale-down in these applications 

is reflected not only in the downsizing of existing equipment and facilities, but also in the 

conversion of continuous processes to batch operation, and in the need to address potential 

changes in performance (particularly separations) that may result. The problem is essentially the 

same as that of scale-up, only solved in reverse. The need is still the ability to determine or 

predict the transferability of performance data between facilities of two specific scales.

The avoidance of nuclear criticality and the protection of fissile material are very important 

considerations in safeguarding any process development activities, at engineering scale or above, 

that involve fissile material such as plutonium or highly enriched uranium. Consequently, it is 

essential to incorporate and test sensing equipment and computer data acquisition and 

interpretation in scaled operations to establish their adequacy. Further, it is necessary to maintain 

fissile material accountancy both for process control and for detection of unauthorized diversion 

of fissile material.

Although aspects of this type of material accountability are well established, when new and 

perhaps radically different processes are brought online, it will be necessary to reevaluate 

existing sensor materials by using related equipment. Computer modeling of the systems, both 

with respect to individual process steps and integrated systems, is an essential and wellestablished approach to maintaining accountancy. 
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Nuclear nonproliferation and safeguards missions raise distinctly different issues. Key 

components of nonproliferation include detection of clandestine fissile material processing 

facilities, evaluation of unconventional (nonindustrial) technologies and processing pathways, 

and characterization of materials generated by these alternative technologies. These tasks include 

detection of activities directed toward pursuit of a long-term weapons capability in International 

Atomic Energy Agency (IAEA) declared or undeclared facilities operated by nation or state 

actors, and detection of materials processing in very small (bench- or pilot-scale) installations 

intended for short-term, small-production use. The most cost-effective means for establishing 

signatures and demonstrating detection capabilities is testing that utilizes full-scale, fully 

operating facilities. In reality, the number of processes of potential interest to proliferators is too 

large, and access to operating facilities may be too limited to permit this approach. 

Consequently, the evaluation of processes at some reduced scale is generally required. 

The chief consideration to be applied in this context is the same as that for any chemical process; 

the reduced-scale process must produce results that are representative of the facility of concern. 

Nonproliferation interests include speciation of products, formation of by-products, interaction of 

reagents and products with process and environmental contaminants, and transient behavior. 

Therefore, issues to be considered in scaling include fidelity of materials transfer operations 

(e.g., hydraulics), chemical reaction kinetics (including mass transfer operations involving 

speciation), and use of materials (reagents, materials of construction, and likely contaminant 

sources) identical to those present in the facility of concern. Due to the wide variety of 

chemistries involved and the range of equipment types that could be used, determination of scale 

is a function of both the specific unit operation and type of data that is desired. For example, if 

the desire is to determine equilibrium speciation of nuclear materials free of chemical 

contaminants, any experiment conducted at the appropriate stoichiometry, temperature, pressure, 

and atmosphere will suffice. If transient behavior including speciation effects from chemical 

contaminants is of interest, great care must be exercised to perform testing under conditions 

identical to those at the scale of concern. 

2.3 EM Scale-up Needs

The EM program has many engineering process scale-up needs. Scaling up the processes will be 

constrained by timing and budgetary considerations. Notwithstanding these considerations, there 

are a large number of processes and equipment pieces that require testing and scale-up, some at 

several levels of scale-up. EM is dealing largely with first-of-a-kind plants, limiting availability 

of lessons learned from previous plants. Each tends to be somewhat unique, with different waste 

streams based on the site history. The scale-up needs are confounded by the wide variety of tank 

waste materials and uncertainty in their physical and chemical properties. Designing processes 

and scaling them up is complex because of the wide variability in the streams to be processed 

and the potential need to test many compositional variations of feeds in the laboratory to 

accurately simulate what is going to happen in-process. Consequently, a very ambitious program 

would be required to meet the scale-up needs. For the present workshop, no attempt will be made 
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to address the very large programmatic commitments, time constraints involved, and budget 

requirements for meeting the scale-up needs. 

The following is a discussion of examples of important scale-up requirements for some of the 

processes under consideration for use. In particular, site scale-up requirements for the Hanford 

site are addressed.

 

Storage Tanks 

The waste storage tanks contain a mixture of soluble salt solids, insoluble sludge solids, and 

aqueous solutions. The solids depth ranges from inches to several feet, and the solids include 

particles and agglomerates with a wide range of sizes and densities. When wastes from different 

tanks are blended before transfer to the vitrification plant, new solids may precipitate, some 

immediately, some over a period of time. Historically, such processes as dissolution with hot 

water or acid, mixing with in-tank horizontal jets, and sluicing have been used, although this is 

not an exhaustive list. Avoiding selective sedimentation of heavy solids is important because 

local accumulations of plutonium oxide could pose a criticality problem. In addition, radiolysis 

and chemical reactions produce hydrogen and other gases, so flammable gas risks may be 

present both before and during waste transfer and mixing. 

The primary need is to assess the adequacy of mixing and mobilization; secondarily, there is a 

need to evaluate the potential for additional solids being contributed by precipitation in blended 

wastes and for flammable gas release during mobilization. Important physical phenomena and 

properties include particle settling under mixed and unmixed conditions, particle agglomeration 

rates, multiphase flow under transient conditions (rotating jets, active sluicing), and rate of 

mobilization of solids beds under those same conditions. Laboratory-scale tests can provide 

information on (for example) particle settling under simple, easily defined conditions, the 

solubility of species in blended wastes, the kinetics of precipitation, and the shear stress required 

to mobilize solids. Translating these properties into predictions of full-scale mixing and 

mobilization is likely to require tests at more than one scale. Computer simulations that account 

for the phenomena could reduce the number of different scales that require testing. Because it is 

difficult to design simulants to simultaneously represent all waste properties, tests that use actual 

tank waste in small-scale processes could produce significantly more meaningful results 

(particularly for settling) than would simulants.

Vitrification Plant 

After wastes are transferred to the vitrification plant, the solids of greatest concern are typically 

sludges. The key process steps are keeping the slurry mixed, taking representative samples to 

support processing decisions and assess possible criticality issues, transferring sludge slurries 

within the plant, and being able to re-mobilize cohesive and non-cohesive sludge layers in tanks 

after postulated off-normal mixer shutdowns. Pulse-jet mixing has been chosen as the primary 

mixing and mobilization process, with air sparging also being planned for mixing in tanks that 
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are expected to contain the more non-Newtonian sludges. As in the Hanford waste tanks, it is 

important to avoid conditions that allow selective sedimentation of heavy solids, retention of 

flammable gas, and plugging of lines and equipment. Conditions that produce corrosion of 

vessels, equipment, and lines and shorten plant lifetime must also be avoided.

Scale-up testing and/or simulation are needed to evaluate the potential for flammable gas 

retention and rapid release in sludge wastes, assess the adequacy of mixing and mobilization, 

confirm representativeness of sampling, and define the measurements needed for process control. 

Important physical phenomena and properties may include corrosion chemistry and kinetics, 

particle settling under both mixed and unmixed conditions, multiphase flow under transient 

conditions (pulse-jet mixing), non-Newtonian rheological properties of slurries, mobilization of 

solids beds using jets (possibly of non-Newtonian fluids), and solids cohesive properties that 

contribute to plug formation. As for the waste storage tanks, a combination of multi-scale testing, 

simulations, and small-scale testing with actual waste would be the most effective approach.

K-Basin Storage 

In the K-Basin, uranium-containing sludges are stored in containers. Hydrogen is produced in the 

stored sludge, with potential accumulation in vessel-spanning bubbles that could rapidly release 

hydrogen and produce flammable concentrations in the vessels. Fins on the vessel walls have 

been proposed as a way to direct gas to the surface as it is generated, preventing accumulation. 

Scale-up testing and/or simulation are needed to evaluate the potential for flammable gas 

retention and rapid release in the sludge in the vessels. Important physical phenomena and 

properties include movement of gas in pores and gas percolation through channels and waste 

mechanical behavior as gas accumulates in pockets or layers. 

Next-Generation Melters 

As the first-generation waste melters reach the end of their useful lives, they will be replaced by 

new melters. These new melters may not be the same type or size as the melters they replace. 

New melter types and sizes will require scale-up testing and/or simulation. 

Solids Filtration 

Filtration of a very wide variety of solid suspensions will be required. Cross-flow filtration is 

proposed for this operation because of its resistance to plugging and fouling. This type of 

filtration will need to be tested on several scales on solids representative of the solids to be 

filtered. At Hanford, a pretreatment engineering platform (at 1/4.5 scale) was constructed that

employed cross-flow filters to pilot the operation of the Waste Treatment Plant (WTP) using a 

single simulant. Over the course of the mission, the plant will process waste tanks with a wide 

spectrum of solids composition and rheological behaviors. These tanks contain multiple layers of 

various wastes, and some have not been sampled. Therefore the need to anticipate issues, at 

scale, before they are encountered by the WTP will persist throughout the WTP mission. 
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Pretreatment Plant Processes 

Several different separations processes will be carried out in pretreatment facilities. Testing at 

several scales of the individual process steps and of the processes integrated to study process 

interactions will be required. Examples of processes include the removal of aluminum, removal 

of chromium, and separations of actinides.

Transfer Line Plugging 

Slurries of mobilized solids will need to be transferred from waste tanks to process feed tanks 

and from there to process equipment. The possibility exists that the solids may settle out in 

transfer lines, causing line plugging and requiring extensive, expensive, and time-consuming line 

clean-out. Certain solids can produce gels that contribute to line plugging. Appropriate simulants 

will need to be developed and tested for transfer characteristics and adequacy in representative 

pumping and piping equipment. Methods of unplugging transfer lines will need to be tested in 

prototypic systems at several scales to be employed in the various transfer lines.

Common Scale-up Needs 

Common to all of these mission needs is the requirement to move technology from the laboratory 

to plant scale. The specifics of the separations technology being developed to meet the mission 

needs will be described in other sections of this report. These technologies may be evolutionary 

or revolutionary in nature. Table 1 provides an overview of the types of technology needs that 

exist and are being developed to support the mission needs of EM, NE and NNSA. 

Table 1. Overview of Separations Technology Scale-Up Needs 

Technology NE NNSA EM

Mixing X X 

Melter X X

Solid/Liquid Separations X X X

Off-Gas Separations X X X

Extraction Processes X X X

Liquid/Solid Transfer X X

Testing Sensors on Scaled System X X X

Instrumentation, Analytical X X 

Electrochemical Systems X X

Conceptually, scale-up is relatively simple. Engineering principles are applied to a chemical or 

physical process to increase its throughput to achieve a desired plant capacity. However, we are 

dealing with very complex chemical matrices and with phenomena that are not yet fully 

understood in all cases. For example, the design of the Defense Waste Processing Facility 
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(DWPF) began with small-scale melters and went on to the one-third-scale Integrated Defense

Melter System (IDMS) to test phenomena that would not be manifest in smaller-scale testing. In 

particular, noble metal particles would accumulate at the bottom of the melter and short out the 

melter at larger scale but not at small scale. Phenomena such as these are best identified when 

there is a clear mission need and a well-defined flow sheet. 

In general, the practical process problems are affected by multiple physical phenomena that scale 

differently and that must be understood individually before their combination can be understood. 

In any given test, only one or two phenomena at a time can be considered. This was the case, for 

example, in the Hanford pretreatment engineering platform testing. As a further practical point, 

the use of simulants is generally necessary, but the scaling of their properties is difficult, as is 

finding and combining constituents to produce the desired properties.

Finally, in many cases, new technologies are being coupled with existing technologies and may 

result in some unexpected behaviors. As a result of all these factors, the scale-up process is very 

complex and must be tailored to a specific situation; no single standard approach fits every 

application. 

2.4 What are the Appropriate Scale-up and Demonstration Levels?

Discussion: It is very important to first determine what the scale-up goals are. For example, it 

may be important to have a pilot plant or demonstration plant that is large enough to provide 

material that may be needed for other parts of fuel cycle development. For example, if it is 

desired to obtain enough actinide elements to produce targets useful for determining nuclear 

physics data needed for actinide burn-up calculations, then a different scale of operation may be 

needed than that required for demonstrating new separations processes or product purity. One 

should establish scale-up goals that will meet as many aspects as practicable of the entire fuel 

cycle’s needs so as to avoid unnecessarily duplicative activity. This activity may be greatly 

enhanced by appropriate modeling (see discussion below). 

Scale-up is not a series of well-defined steps. Rather, it is a continuum with overlaps between 

one scale and the next. Demonstration of some processes and equipment at a small scale may be 

adequate for the design and construction of the largest plant. With this in mind, scale-up should 

be performed at the smallest scale in which the needed data can be obtained. 

The scales needed are quite specific to the particular set of processes that are being developed. 

Voloxidation is a good example. In terms of overall process performance and fission gas release, 

only limited data can be obtained from non-radioactive testing; tests must be run with irradiated 

fuel. Full scale is not required to develop a gas-release thermal profile, so an intermediate scale 

can be used for process development. But there are other areas that require full-scale testing with 

inactive materials, such as the temperature profile across the unit at full gas flow. Generally fullscale tests are not done with fully active materials because flexibility is drastically reduced. 

Physical changes are difficult to make because of contamination or safety controls, criticality can 
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become a factor because of the presence of fissile materials, and significant quantities of 

radioactive waste are typically generated. While there are exceptions, generally a larger-scale 

active test should not be conducted until the process has been fully defined. 

2.5 Sequencing of Scale-up

Discussion: The scale-up strategy must be consistent with the type of data that is desired. The 

data is situational; it depends heavily on the flowsheet and the plans for operation (the safety 

basis). Therefore, providing any general guidance is very difficult. Generally speaking, scale-up 

proceeds from laboratory (or bench) scale, to pilot (or engineering) scale, to demonstration (or 

prototypic) scale, to full scale (when a final large-scale plant is envisioned). Other possible ways 

to define scale are relative to final throughput of the facility. Laboratory scale may be regarded 

as 1/100,000 to 1/10,000 scale; pilot scale may be 1/1,000 to 1/100 scale; and demonstration may 

be 1/100 to 1/1 scale. This is a prudent sequence of scale-up when a very large plant is 

envisioned that helps guard against unpleasant surprises and expensive retrofitting. 

But there really is no one-size-fits-all approach to scale-up. If applicable scale-up information is 

available from elsewhere, then it may be possible to skip or simplify one or more scale-up steps. 

It is best to carefully determine the number of scale-up steps needed to ensure successful scaleup based on already available scale-up information and on process complexity and novelty. The 

number of scale-up steps depends strongly on the goals established for each level of scale-up. 

The more goals addressed at each scale-up, the fewer scale-up steps are likely to be needed. 

What data are needed for the scale-up of each specific unit operation is going to vary. Based on 

chemical engineering experience, it is known that some things scale better than others. There are 

many factors that come into play; for example, kinetics becomes very important in some of the 

more novel separations, particularly for liquid–liquid extraction in a centrifugal contactor rather 

than a mixer-settler.

2.6 How Many Steps of Scale-up Are Needed?

Discussion: As already noted, several scale-up steps may be required, depending to a significant 

extent on the anticipated size of the large-scale plant relative to the size of the pilot plant or the 

demonstration plant, as well as the complexity and novelty of the processes. If the processes use 

separations reagents (e.g., extractants that have never been used in large plants on a continuous 

operating basis), then several stages of scale-up may be needed to unearth subtle but important 

factors such as reagent consumption or radiation damage leading to adverse chemical reactions 

in the process, problems in recycle, or excessive waste volume. Smaller-scale plants should be 

operated for a sufficient time period (as determined by the process) for subtle adverse effects to 

become apparent.

2.7 Process Considerations/Issues

Discussion: There are issues that arise with full-scale plants that do not necessarily show up 

during the operation of pilot plants or demonstration plants because of the smaller amounts of 

material being handled in these plants. This is due to a variety of factors, such as shorter 
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operating times and differences in materials used (for example, use of simulants). Issues such as 

crud formation, process upsets, solvent and reagent recycle, and inappropriate inter-stage surge 

capacity have all been observed to cause problems in large plants in the past. These potential 

issues arising from scale make the selection of an appropriate scale-up factor very important. 

Large plant operating experience should be used as a guide in selection of the proper scale-up 

factor for the smaller plants so that the problems noted above will be apparent and solutions for 

them can be built into plant operation. 

The duration of pilot plant testing also depends somewhat on the history of the process being 

developed. If it is an evolutionary process, a modification to an operational industrial plant, then 

the need for long-term testing is less. If it is a revolutionary (transformational) process, then the 

need for long-term testing is much greater. Even in the case of well-established and understood 

processes such as PUREX, issues still arise with process changes, and operational knowledge is 

still being gained. For most new processes, aside from generally applicable plant design 

experience, there is no industrial process basis.

There is a distinct advantage to active testing at a smaller scale: off-normal events can 

deliberately and safely be induced to examine potential excursion in concentration, pressure, or 

temperature—something that would not be allowed at a larger scale. 

The duration of tests is a key factor in the scale-up process. Large-scale operations facilities face 

both acute and chronic problems. Chronic problems include third-phase build up, cruds, wear, 

erosion, fatigue, and corrosion. Often, scale-up is focused on acute problems. But it is the 

chronic problems that usually impact plant operations. Extended tests are required to learn what 

long-term issues come up from routine operations and how the system responds to changes, 

upsets, and multiple cycles. In an extraction or ion exchange process, for example, solvent or ion 

exchange resin degradation in a radiation field can significantly impact separation efficiency; 

similarly, conditions under which formation of precipitates in pipes and tanks occurs can be 

determined best through term operations. The entire process, with all 

recycle lines, must be operated on a continuous basis long enough to 

see these effects because they may determine long-term performance. 

Improvement to long-term scale-up testing capabilities would be of 

benefit. While there are accepted methods for certain types of 

accelerated testing (e.g., accelerated corrosion tests and accelerated 

radiation stability tests), not all degradation processes can be 

effectively accelerated with current methods. This is particularly true 

for combined effect.

2.8 Use of Simulants

Discussion: Simulants in laboratory studies, in engineering-scale tests, in pilot plants, and in cold 

testing of large plants can be useful when the process or operation being simulated is not 

Large-scale 

operations 

facilities face 

both acute and 

chronic 

problems 
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critically dependent on specific chemical or physical properties of the simulants vis-à-vis those 

properties of the real material. On the other hand, there are many separations processes and 

operations in which simulants may give poor or misleading results. Scale is important in this 

regard, as is test duration. Factors such as radiation damage to solvents or hydrolysis may be 

very important. While radiation damage and hydrolysis on uranium or most fission product 

extraction, or on hydrodynamics, can be simulated fairly well with a gamma irradiation loop 

(such as the MARCEL loop in France or the irradiation loop at INL), the impacts of degradation 

products on some specific elements (e.g., neptunium and technetium) are difficult to simulate

because they produce effects that are not seen when using cold stimulants. There is no good way 

to simulate the behavior of neptunium in the PUREX process; lanthanide separation from 

actinides similarly cannot be simulated; and rhenium is a poor simulant for technetium in some 

valence states; the chemistry of ruthenium is very complex in the spent fuel. 

There are also a number of potential issues that can be readily evaluated with cold simulants: 

hydraulics, heat transfer, weight, stress, mechanical, altering of solids. For certain key process 

behaviors, a simulant will be sufficient. In plants at all scales, it is possible to use un-irradiated 

uranium as a simulant for used or spent fuel when studying hydraulic and equipment behavior. 

No matter how good the simulants are, there are always unknown issues that arise. Often, there 

are unexpected interactions simply because there are components in feed that were not put into 

the simulant either because their presence was not known or they were considered relatively 

unimportant. They are later shown to be important. The use of simulants is valuable and costeffective, but the limit and underlying assumptions used in the simulants must be understood 

when extrapolating the results. 

An example where issues arose is the in-tank precipitation process (ITP) at Savannah River Site. 

Scale-up was done on very small scales with simulants that did not adequately represent the real 

materials. The filtration process was “successfully” developed and demonstrated at a small scale, 

but when it was run in a cold-type test at a larger scale, there was a reaction that created tar that 

fouled filters nearly beyond recovery. Other issues arose from the separate development of the 

cesium precipitation process using sodium tetraphenylborate, separate development of the 

monosodium titanate sorbent for strontium, and the coupling with the filtration process. 

Ultimately the ITP process was abandoned in 1998 because of the production of a larger volume 

of flammable benzene than was expected.

1

2.9 Modeling and Simulation

 Running these coupled tests is best, as the interfaces 

between unit operations can pose chemical or hydraulic problems, etc. 

Discussion: With the introduction of very sophisticated modeling and simulation computer models, 

it is possible to calculate mass and energy balances, to simulate time-dependent phenomena, and to 

provide visual representations of separations processes. These very powerful tools can help to 

 

1 Alternatives for High-Level Waste Salt Processing at the Savannah River Site. Washington, DC: National 

Academies Press, 2000. <http://www.nap.edu/catalog/9959.html>
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design and optimize separations processes and equipment; elucidate scale-up issues; and provide 

information on product and waste stream volumes, radioactivity content, and nuclear criticality 

potential. On a more fundamental level, modeling can guide separations reagent design and 

efficacy. Continued development of new and better computer models and simulation codes is 

needed. A comprehensive and vigorous experimental program should be established to provide the 

necessary data for computer model code development, validation, and implementation. The 

importance of strengthening these capabilities has been shown in France; in well-understood 

situations, these capabilities have allowed a step in scale-up to be skipped. The Advisory 

Committee on Nuclear Waste and Materials of the Nuclear Regulatory Commission2

• Knowledge of the split of each chemical species in each process step in the plant (the 

separation factors), especially concerning tritium, iodine, technetium, neptunium, and 

radioactive material associated with the cladding. 

identified the 

following research needs relevant to modeling and simulation of reprocessing systems:

• Developing a model that simulates the interconnected equipment in a facility flowsheet 

using the separation factors to determine the radionuclide concentrations and inventory. 

Such models need to accommodate complexation, colloids, internal recycle streams, and 

important conditions in bulk fluids (e.g., temperature, acidity, radiolysis). 

• Understanding stability of organic extractants, solvents, and ion exchange materials and 

the safety implications of degradation product. 

A 2006 workshop co-sponsored by NE and the Office of Science’s Advanced Scientific 

Computing Research3

• Plant-scale simulation

 program focused on modeling and simulation related to advanced nuclear 

energy systems. The workshop identified the following challenges: 

– Integrated tool set to enable full-scale simulation of a plant—chemistry, mass 

transport, energy input, and physical layout 

– Dynamic plant models 

• Computational fluid dynamics 

– Multiple fluid phases, fully developed turbulence, non-Newtonian flows, interfacial 

phenomena, and radical chemical processes due to the presence of ionizing radiation

• Predictive methods for thermodynamics and kinetics data as input to process simulators 

– Extend currently limited thermodynamics data reliably into broader parameter ranges 

– Incorporate limited experimental data and use computational chemistry 

 

2 Offices of Nuclear Energy, Office of Advanced Scientific Computing Research, and U.S. Department of Energy, 

Workshop on Simulation and Modeling for Advanced Nuclear Energy Systems. Washington, DC: U.S. Department 

of Energy, 2006. <http://www-fp.mcs.anl.gov/anes/SMANES/gnep06-final.pdf>

3 Croff, A. G., R. G. Wymer, L. L. Tavlarides, J. H. Flack, and H. G. Larson. Background, Status, and Issues 

Related to the Regulation of Advanced Spent Nuclear Fuel Recycle Facilities—Advisory Committee on Nuclear 

Waste and Materials White Paper, NUREG-1909. Washington, DC: U.S. Nuclear Regulatory Commission, 2008. 

<http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1909/index.html> 
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• Rational design of the separations system from first-principles physics and chemistry

– Predict what molecules will have the desired properties and can be synthesized

– Reliably predict the properties of liquids, solvation, and kinetics in solution

• Connecting/crossing time and length scales, with uncertainty quantification 

– Access longer times without dramatic changes in theoretical and algorithmic approaches

– Span spatial regimes; critical regime is the mesoscale (1 nanometer [nm]– 

1 micrometer [μm]) 

• Data management and visualization

– Capture, manage, integrate, and mine data from a wide range of sources to enable the 

optimal design and operation of separation processes 

Simulants and simulation both allow the selection of certain phenomena and the drawing of 

insights to guide design and experiment. Comparison of model/simulant results with data from 

actual materials may indicate good agreement, but often these do not agree completely. When 

this happens, it is critical to understand what was causing the different behavior. This can lead to 

improved models and simulants and a better understanding of the 

process itself. A recent MIT report4 pointed out that “ultimately there is 

no substitute for testing to validate or disprove the conclusions of 

simulations. The testing time frames are long and thus the need for 

long-term research programs with appropriate irradiation facilities.”

In addition to process modeling of the plant chemistry models, systems 

models can aid in understanding interplay of the specific facility with 

the rest of the complex in which it functions. Often local changes to a 

process or facility to optimize performance or a specific output can have a detrimental effect on 

the operation of other processes or facilities in the overall system. For example, introduction of a 

sulfur-bearing reagent to aid extraction can reduce the durability of a waste form produced from 

the effluent. Models can be used to evaluate these interactions, for very complicated systems 

where impacts are not direct or obvious. 

2.10 Scale-up and Risk Reduction

The purpose of scale-up testing is to provide additional technical information to reduce project 

risk and mature a technology to a point where design information can be provided or the 

technology can be transferred to a commercial entity for implementation. “Technical readiness 

levels” is a methodology adapted by DOE from a National Aeronautics and Aviation 

Administration (NASA) methodology to assess the relative technical maturity of a technology. In 

very general terms, technology readiness levels (TRLs) of 1–3 reflect the development of 

technical concepts (or research phase), TRLs of 4–6 reflect proof-of-principle testing (or 

development phase), and TRLs of 7–9 reflect proof of process performance (or demonstration 

 

4 Massachusetts Institute of Technology, The Future of the Nuclear Fuel Cycle. Boston: Massachusetts Institute of 

Technology, 2011. <http://web.mit.edu/mitei/research/studies/nuclear-fuel-cycle.shtml> 

“ All models 

are wrong, 

but some are 

useful.” 

 

George Box 
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phase). A TRL of 9 implies full-scale demonstration/implementation of a technology using 

actual feed materials. A TRL of about 7 is required to have sufficient detail on a technology to 

enable design activities as well as reduce technical risk to a level where commercialization by 

industry would be appropriate. As stated previously, there is no one-size-fits-all approach to 

scale-up, and technical risk can differ for technologies based on past experience. For example, 

scale-up of a new solvent extraction process, which takes into account over 60 years of 

industrial-scale equipment development and operational experience, would be much different 

than scale-up of a novel transformational technology that has no historical experience base. In 

the case of the latter, more testing would be required at prototypic or pilot scale, for longer 

periods of time and with actual feed materials, than for the former. 

Table 2 gives some general principles of TRLs for separation processes, up to where the 

technology would be ready to support design activities or commercialization (i.e., TRL 7). Scaleup attributes include research transition from simple simulants to actual materials, from 

laboratory testing (glassware) to full-scale equipment testing, from testing single-unit operations 

to integrated testing, and from testing of short duration to testing (of at least some aspects of the 

technology) for extended time periods. It should be noted that the TRL levels are not welldefined, discrete steps, but rather a continuum of levels with some overlap. They are intended to 

represent general development stages and are somewhat subjective.

2.11 Mechanical Aspects of Scale-up 

In the later stages of equipment scale-up, the integration of remote maintenance aspects must be 

considered. There is a considerable amount of this specialized knowledge to draw upon within 

the DOE complex that has been developed first in the defense processing facilities and later 

applied to DOE, NASA, and other DOE facilities, such as the Spallation Neutron Source (SNS), 

and fusion facilities. Remote maintenance capabilities facilities and systems should include: 

• Improved remote viewing (cameras in hot cell) 

• Computer-controlled remote handling systems (cranes and manipulators) 

• Standardized equipment module design to facilitate replacement, repair, and 

reconfiguration of process equipment 

• Dedicated support areas for remote maintenance of both process and handling systems 

• Dedicated mock-up area for new equipment testing (both operational and maintenance) 

3-D virtual design aides should be considered for the interface of the facility and process 

equipment. Studies can be conducted with these models to better understand both operational and 

maintenance attributes. NE should draw on the experience of EM staff for the backend cleanup 

of reprocessing facilities (and similar plants) and the wastes generated as well as waste disposal 

requirements (configuration, storage, etc). NNSA experience on proliferation issues, systems, 

and resistance configuration requirements should also be integrated into remote design concepts. 
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Table 2. Relationships of Scaling and Technology Readiness Levels (TRLs) 

TRL Descriptive 

Terms from TRA 

Standarda

Scaleb of 

Testing or 

Demonstration 

Implied by TRA 

Standard

Level of 

Integration of 

Components

Simulants vs. 

Real 

Radioactive 

Materials

Type of Data 

Expected

Length of 

Testing and or 

Process “Run”

c

1 “basic technology” 

and “process 

principles”

Paper and 

laboratory scale 

(i.e., test tube)

None Simulantsd Chemical 

performance 

Short tests in 

laboratory

2 “equipment and 

process concept”

Laboratory scale

(batch testing)

None Simulants with 

tracers

Chemical 

performance

Short tests in 

laboratory

3 “equipment and 

process analysis,” 

“proof of concept 

in a simulated 

environment”

Laboratory scale

(batch and 

limited 

continuous)

Single-unit 

operations

Simulants with 

tracers 

Chemical 

performance, 

laboratoryscale 

equipment and 

process 

Short tests in 

equipment

4 “lab-scale testing 

of similar 

equipment,” “in a 

relevant 

environment”

Laboratory scale 

(continuous)

Single-unit 

operations

Simulants to 

limited testing 

with actual 

materials 

(laboratory)

Equipment 

performance 

and process 

refinement

Equipment tests 

of short to 

medium duration

5 “bench scale 

equipment” 

“process testing,” 

“demonstration in 

a relevant 

environment”

Laboratory scale 

to engineering 

scale 

(continuous)

Single-unit 

operations to 

coupled 

(integrated) 

unit operations

Simulants at 

engineering 

scale plus actual 

feed materials at 

bench scale

Equipment 

and process 

integration and 

operational 

Equipment tests 

of medium 

duration with 

targeted testing 

on long-term 

effects

6 “prototypical 

engineering scale 

equipment,” 

“process testing in 

a relevant 

environment”

Engineering 

(pilot scale) to 

prototypical 

scale 

(continuous)

Coupled-unit 

operations

Simulants at 

engineering 

scale plus actual 

feed materials at 

bench scale

Process 

performance 

and 

operational

Equipment tests 

of longer duration 

to begin to define 

operational 

parameters

7 “full-scale, 

prototypical 

system,” “in a 

relevant 

environment”

Full scale 

continuous

Coupled-unit 

operations

Simulants at full 

scale plus actual 

feed materials at 

bench to 

engineeringscale

Operational 

performance 

and 

procedures, 

safety basis

Equipment tests 

of sufficient 

length to fully 

define 

operational 

parameters

a. Scaling and testing terms taken from the description of the TRL, in DOE Guide 413.3-4.

b. There was significant discussion of how to determine scale, when the final size of a facility may well be 

unknown; thus, some parameter other than equipment size may need to be used, such as throughput or batch size.

c. Length of time at various stages may be dependent, in part, on the level of “novelness” of the process being 

developed and the variability of feed expected, along with whether flexible outputs are anticipated. It can also 

depend on the time period you have to develop your answer.

d. Simulants refers to both chemical and physical property simulation. Simulants depend on the thermodynamic, 

kinetic, and hydrodynamic data needed; early stages may use a number in different tests, while process-based tests 

may require more complex simulants covering a broader spectrum of attributes. Also, if feed material for a process 

is variable, more simulants may be required.
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3.0 International Aqueous Separation Scale-up Experience 

There is a great deal of international experience relative to the scale-up of solvent extractionbased separations processes. This includes scale-up of the PUREX process to support the 

Thermal Oxide Reprocessing Plant (THORP) separations facility in the United Kingdom and the 

approach utilized by the French Alternative Energies and Atomic Energy Commission (CEA) for 

the scale-up of PUREX and other novel solvent extraction processes being developed in France. 

These approaches have been demonstrated to be successful and serve as guide for scale-up 

testing requirements for advanced separation facilities designed and constructed in the United 

States. A description of the processes utilized in the United Kingdom and France are provided 

below.

3.1 CEA, France

The CEA Marcoule design approach relative to scale-up is based on back-and-forth iterations 

between modeling and basic laboratory studies, integration active tests in hot cell facilities, 

inactive tests, and characterization of industrial equipment in order to build simulation codes that

allow a correct scale-up of the process from the test tube to the plant. As shown in Figure 1 from 

CEA, the development of a new process should undergo the following steps (and the 

corresponding approximate scales): 

• Basic and applied laboratory studies (scale 1/100,000) 

• Laboratory-scale scientific feasibility (scale 1/10,000) 

• Engineering-scale technical feasibility (scale 1/1,000) 

• Pilot-scale demonstration (scale 1/100 to 1/10) 

• Industrial-scale test (scale 1)

After selecting the appropriate extracting system, accurate and parametric experimental data 

(thermodynamics, kinetics, physical properties, and solvent degradation) must be acquired at 

laboratory scale (batch test tube) to develop a first model which is used to design process 

flowsheets. Counter-current tests are then performed on surrogate and genuine solutions, in 

laboratory-scale mixer-settlers, in order to demonstrate the validity of this model and the 

feasibility of the concept (in terms of recovery and purification performances). Then, continuous 

contactors (pulsed columns) are used to check the compatibility of the extracting system with the 

continuous equipment in terms of hydrodynamic and transfer kinetics. At Marcoule (AtlananteCBP facility), 15-mm pulsed columns can be used to perform the test on a high-level waste 

(HLW) solution and demonstrate the technical feasibility at the engineering scale.

The scale-up of the contactor (from the Φ15 mm to the Φ900 mm industrial size, in the case of 

pulsed column) is an important step and needs a full characterization of the equipment and of the 
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Figure 1. Typical scale-up sequence 

emulsion in this equipment (drop size, phase transfer efficiency, dispersion coefficient, and so 

on) in order to correctly model the scale-up. Moreover, intermediate tests can be carried out on a 

section of the industrial column on an inactive or uranium surrogate solution to validate the 

hydrodynamic behaviour at scale 1. However, depending on the confidence level of the 

simulation and the knowledge, expertise and industrial feedback on this equipment, this 

intermediate step could be skipped. The scale-up of the centrifugal contactors used in the 

plutonium purification cycle at UP2-800/R4 (La Hague plant) is a good example to illustrate the 

method. Several tests were performed in the Atalante facility on laboratory-scale centrifugal 

contactors; thanks to a good modeling of the phase transfer efficiency and the physical 

characteristics of the phases in the laboratory-scale contactors, these tests enable reaching a scale 

factor of 100 from Atalante to La Hague plant. Figures 2 and 3, provided by CEA, show the 

types of data collected at various levels of scale-up.

In dealing with nuclear materials, the impact of the radiolysis on the solvent must also be 

carefully studied, understood and scaled up. Assessment of the long-term solvent behaviour in an 

irradiation loop (MARCEL loop) is very useful to check the resistance of the solvent under a 

continuous run of hydrolysis and radiolysis and to evaluate the performance of the solvent 

cleanup and the potential impact of the degradation products on the hydrodynamic and recovery 

performances. The degradation products and their behaviour in the plant must be identified and 

quantified. The impact of the water-soluble degradation products on the fission products’ 
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concentration must be carefully studied at a representative scale with regard to the safety of the 

process. The impact of new complexing agents (added at the stripping steps in particular) on the 

actinide conversion, or the possibility of destroying them prior to vitrification, should also be 

taken into account in the demonstration of the overall process. 

Finally, the synthesis of a large quantity of extracting (or complexing) reagents and the 

adaptation of online analysis for new processes (pH, for example, for actinide/lanthanide 

[An/Ln] separation processes) are other key points to consider in the industrialization process. 

The recent experience in France with the development and installation of the cold crucible 

induction melter at La Hague showed the benefit of using a team with a combination of 

scientists, technologists, operators, and maintainers all involved from the beginning. Technology 

was developed with operators engaged; when they did the scale up, the team running the 

program ended up installing and running the technology in the La Hague plant. 

3.2 THORP Separations Facility, United Kingdom

In conducting research, development, and demonstration work for the United Kingdom THORP 

project, British Nuclear Fuels Limited performed a large scientific and engineering development 

program against defined plant requirements across very wide subject areas in a progressive 

manner to optimize project and operational costs and minimize risks. Scientific data, trials, and 

results of mechanistic and process modeling were required to support design, confirm 

operability, and underpin safety cases. 

Most THORP development work was “warm” (chemical separations) or “cold” (mechanical). 

The principal “hot” rig was the “highly active miniature pilot plant,” with a processing capability 

of 1 kg heavy metal (HM)/day of irradiated LWR or advanced gas-cooled reactor fuel. This 

bench-scale facility (10-mm diameter pulse columns, 2-m height, plus small mixer-settlers) had a 

throughput scaled down by 1/6,250 compared to THORP. It confirmed the complete chemical 

flowsheets for several fuel types but did not demonstrate process integration and control. It 

possessed a relatively low TRL. There was a similar “warm” rig that did not use active fission 

products. 

For the chemical separations flowsheet, the majority of research and development experimental 

work was performed using miniature and engineering-scale pulse column equipment with 

“warm” (e.g. U, HNO3, TBP/OK and/or selected components of neptunium, plutonium, 

technetium, nonradioactive fission product simulants at various concentrations with low 

penetrating dose) feeds. This was carried out iteratively in conjunction with modeling studies and 

supported by existing know-how and engineering assessments. This commenced early in the 

development cycle and extended over most of the cycle because of technical “surprises.” It was 

combined with very limited “hot” (i.e., high active using spent nuclear fuel) miniature flowsheet 

confirmation tests. Some testing was “cold” (i.e., using nonradioactive process simulants).
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Figure 2. Scale-up from engineering technical feasibility scale to pilot or industrial scale

 

Figure 3. Scale-up from fundamental laboratory to feasibility studies
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Chemical separations process equipment and control was developed and tested using uranium 

active pulse column engineering-scale systems. Effects of deviation from flowsheet conditions 

and recovery were investigated to support preparation of safety case and operating 

documentation. The strategy sought to separate engineering, hydrodynamics, and mass transfer 

effects of major “warm” species from the chemical interactions of minor fission product “hot” 

species with each other and process reagents such as reductants. Mechanical equipment units in 

THORP, generally, were “cold” tested (i.e., using nonradioactive simulants), developed, and 

finalized using full-scale items. The onus is then on development of realistic simulants using 

post-irradiation examination, modeling, sample irradiations, and laboratory-scale radioactive 

tests. However, this full-scale work was plant-specific and performed in the later part of the plant 

development cycle. No full-plant integrated mock-up engineering facilities were used prior to the 

construction of the full production plant, although many key equipment areas were tested at full 

scale or engineering scale.

In a 15-year program for THORP development, the use of “hot” (high active using spent nuclear 

fuel) testing of full-scale or engineering-scale equipment was avoided on engineering, economic, 

and regulatory grounds. (The exception was active trials of the monitoring of intact spent nuclear 

fuel assemblies within pond.) However, the selected process flowsheet chemistry was an 

advancement of existing PUREX and operational know-how, and applicable experience was 

available from ongoing commercial reprocessing plants in the United Kingdom and France. 

Development activities were not undertaken within a production plant, although operational data 

and experience were analyzed and used.

For THORP, extensive cold testing of full-scale industrial units against clear and optimized 

commercially based reliability requirements was essential. The lack of reprocessing plant 

standardization, long chains of operations, complexity of individual operations, and zeromaintenance design for high active solvent extraction created the imperative for high equipment 

dependability. High-integrity engineering design for nuclear and nonnuclear systems is 

fundamental to reaching the target reprocessing throughputs, given the likely extreme outages for 

equipment rectification or replacement and the integral effects of failures in tightly coupled 

nonnuclear support systems. 

A 1/6,250-scale fully active “hot” pilot plant was built and operated, supported by a separate 

“warm” 1/250-scale facility that scaled up the process chemistry from the hot plant and carried 

out unit operations. Most scale-up was associated with unit operations and full-scale work with 

uranium. The extensive background that already existed with the PUREX process was very 

useful in helping determine what scale-up was required. A similar background does not exist for 

the new processes being considered by EM.

Figure 4 presents a summary of the general approach to flowsheet and equipment development 

and scale-up as provided by Energy Solutions. 
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Figure 4. Approach to scale-up at THORP separation facility in the United Kingdom

The necessity for fully active demonstration was influenced by a number of factors: 

• The plant was supported by a wealth of technical experience gained from the operation of 

historical commercial reprocessing facilities on the site. 

• The PUREX process upon which the plant was based was already understood. 

• Most scale-up issues were associated with the engineering performance of the unit 

operations that could be replaced by full-scale inactive or uranium-active rigs.

The challenge faced in the United States to provide a 21st century recycle facility is compounded 

by the absence of the first two of the above factors. There is very limited commercial-scale civil 

recycle heritage in the United States, and any nonproliferating, partitioning flowsheet is both 

more complex and less proven than the standard PUREX technology. These issues are likely to 

result in an enhanced need for fully active demonstrations for a U.S. deployment—possibly at 

significant scale, depending on the technology adopted. Throughputs and decontamination 

factors will have to be confirmed and experience gained through the operation of such 

representative pilot facilities before full-scale deployment is attempted. 
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Based on its experience in scale-up, France would not change its

methodology. The PUREX process is working quite well. If France

built another plant with the same technology once equipment is 

proven at the engineering scale it could move directly to the 

industrial scale. On the process side, they might do technetium 

scrubbing differently. In the current plants, France had not seen that 

there was an extraction of technetium with zirconium in the 

scrubbing section. This was observed later during pilot plant testing. 

But by the time it was understood, it was too late into plant 

construction, so they implemented an alternate solution using another 

process to provide improved scrubbing for technetium. This was implemented at both La Hague 

and Rokkasho. 

The United Kingdom would potentially have conducted more scale-up trials. Their facilities 

contain a high inventory of material, and with advances in online monitoring and spectrometry, 

there ought to be wiggle room to reduce the inventory size at the plant (and hence the costs), but 

these must be demonstrated. The United Kingdom also expressed caution about the need to 

beware of making adjustments to what are thought to be well-known processes. The United 

Kingdom experienced trouble in areas in which slight adjustments to well-known processes were 

made, but no additional R&D was performed on the modified process. More often than not, the 

adjustments had deleterious unintended consequences that far outweighed the intended 

improvements. 

4.0 Recent U.S. Scale-up Experiences 

The caustic side solvent extraction (CSSX) process is currently being implemented by EM for 

separation of cesium from salt waste at the Savannah River Site. Development of the CSSX 

process started with basic laboratory-scale testing using simulants. This led to batch contact 

testing using actual solutions in the proposed salt flowsheet under extraction, scrub, and stripping 

conditions. Radiolysis testing was then performed using a five-centimeter (cm) centrifugal 

contactor with a cesium-spiked solution. Complete flowsheet testing with actual waste was then 

performed using laboratory-scale 2-cm centrifugal contactors. Performing the tests with 

laboratory-scale contactors was necessary in order to minimize the amount of feed solutions 

needed and the amount of waste generated, both of which would have provided serious handling 

issues. These tests resulted in construction and operation of a pilot-scale separation process for 

operation of the CSSX process with actual tank waste solution. It should be noted that the goal of 

this pilot-scale testing included the operational goal of processing solution from several tanks to 

generate needed space. This was the primary driver in building a “hot” pilot-scale process prior 

to construction of the full-scale facility.

The importance of performing pilot-scale work using a combination of simulants and “real” 

materials has been illustrated several times within EM. The DWPF at the Savannah River Site 

Beware of 

making 

adjustments 

to what are 

thought to be 

well-known 

processes 
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was a first-of-a-kind facility that began radioactive operations in 1996. This operation was 

preceded by about five years of start-up testing of structures, systems, and components. The 

start-up testing was preceded by a decade of testing at the Savannah River National Laboratory 

on systems of various size and complexity, including operation of a 1/3-scale nonradioactive 

melter system known as the IDMS. The IDMS ran for a period in excess of five years during 

construction of the DWPF and provided an important platform for testing and design concept 

verification. Examples of some of the data collected include system qualification data in support 

of the following: 

• Tank mixing and sampling 

• Glass flow and mixing in the melter

• Canister welding and decontamination 

• Overall process flowsheet development and demonstration 

The operation of the IDMS led to several important discoveries that were factored into the design 

process for the DWPF and were essential to the successful start-up testing program and operation 

of the DWPF. These included the following:

• Determination that hydrogen modifications were needed in the facility prior to 

radioactive start-up that would have been significantly more costly after start-up and/or 

led to operational safety issues 

• Data related to melter off-gas flammability calculations that was collected during melter 

pilot testing and serves as the technical basis for the facility documented safety analysis 

The large integrated pilot capability provided by the IDMS was dismantled after start-up and has 

been replaced by a number of smaller unit operations that are less costly than integrated pilot 

capabilities but still offer the benefits of larger-scale systems when integrated with bench-scale 

and real-waste testing.

A second key example that clearly points to the need for extensive scale-up testing and proper 

simulants involves the WTP at Hanford and the use of pulse jet mixers (PJM). “Issues were 

identified related to mixing system designs that will result in insufficient mixing and/or extended 

mixing times. These issues include a design basis that discounts the effects of large particles and 

of rapidly settling Newtonian slurries. There is also insufficient testing of the selected designs.” 5

 

A recent review by the Consortium for Risk Evaluation with Stakeholder Participation (CRESP)

points out that “uncertainty will remain about PJM performance until extensive experience has 

been gained through testing of full-scale or near full-scale prototypic PJM vessels and actual 

operation of the WTP. The current absence of full-scale or near full-scale testing presents a 

 

5 Massachusetts Institute of Technology, Comprehensive Review of the Hanford Waste Treatment Plant Flowsheet 

and Throughput, CCN 132846, v. <http://www.em.doe.gov/pdfs/final_ert_review_of_eac.pdf>
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large risk for the WTP program. A second large source of uncertainty that will impact WTP 

performance are the characteristics of the actual waste feed to WTP.” 6

4.1 Center of Separations Knowledge

There currently exists a significant body of knowledge and expertise within the DOE complex 

that must be preserved in order to support the long-term mission needs of the Department. This 

includes not only the information and data captured in formal reports but a wealth of knowledge, 

experience, and lessons learned during the development of isotope recovery processes and 

nuclear operations that reside in the collective knowledge of current and retired staff. The latter 

has proven to be particularly difficult to capture and is best developed through actual hands-on 

experience and learning. In addition to the data and experience that exists, a number of critical 

demonstration capabilities should also be preserved because of their value as test beds for future 

scale-up operations and for training new personnel. 

Any center created is more likely to be virtual than a brick-and-mortar type institution. The 

distributed model makes sense because of the different capabilities and expertise that exist at 

various institutions within the Department, within industry, within academia, and internationally. 

The appropriate functions of the center need to be defined in detail, but issues to consider 

include: 

• Facilities and capabilities that need to be preserved for scale-up activities in the future

(dependent on the technologies to be scaled) 

• Facilities integral to ongoing operations of the Department (where possible, these 

ongoing operations should be leveraged against data needs and requirements to generate 

data and experience that will advance future Department missions) 

• Institutionalization of systems and processes that help “pass on” the experiential 

knowledge in the nuclear processing community 

• A very strong connection to the university programs to preserve the needed disciplines of 

radiochemistry, process engineering, and “radiochemical engineering” that are currently 

struggling in today’s university environment 

• A mentoring program to get people into the field

The Nuclear Stockpile Stewardship program is a possible model for the center. What helped 

make the Nuclear Stockpile Stewardship program work was that all interested stakeholders were 

involved in scoping the solution and a model was developed that “forced” organizations into a 

collaborative mode.

 

6 The Consortium for Risk Evaluation with Stakeholder Participation III, CRESP Review Team Letter Report 7 – 

PJM Vessels. Nashville, TN: CRESP, July1, 2010. 

<http://www.cresp.org/CRESPIII_reports/CRESP_Review_Letter_Report_7_Final%20_%207-1-2010.pdf> 
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5.0 Findings and Recommendations

1) There are a number of specific common areas between NE, EM, and NNSA to explore in the 

near term. These include the following: improving solid–liquid separations processes, off-gas 

systems, evaporation systems, de-nitration systems, and melter/immobilization/stabilization 

systems. 

2) Scale-up, whether of unit operations, integrated processes, engineering demonstrations, pilot 

plants, or full-scale demonstrations must be very carefully considered with respect to scaleup goals. Goals may be of the following types: 

 Demonstrate unit operations on the appropriate scale, which can be a fraction of full scale 

or, when necessary, full scale.

 Demonstrate that integration of the component parts of a separation process can be 

functional and seamlessly integrated.

 Demonstrate that a scaled version of an engineering process is of an adequate size to 

meet not only the immediate process objective but also the goals of other programs that 

may rely on output from the process demonstration. 

 Establish the utility of simulant or surrogates to reproduce the desired characteristics of 

feeds to the process being investigated. 

 Demonstrate the appropriateness and efficacy of process monitoring and control 

instrumentation. 

 Demonstrate the validity of fissile materials accountancy instrumentation or other 

equipment related to recording, evaluating, and informing fissile material flow and 

handling irregularities.

 Provide verification and needed improvement to computer models of the process. 

3) As the scale-up cycle progresses (see Figure 5), ensure that the development team has 

carefully considered specific scale-up goals and that these goals are reflected in design 

specifications for construction of test equipment at each step of the scale-up process. Also 

ensure that the contractor that builds the equipment fully understands the functional 

requirements of the equipment and the need for adhering to design specifications. 

4) Scale-up operations can provide both data and experience for larger-scale future facilities and 

operations while also addressing a current mission need. For example, the operation of the 

Modular Caustic-Side Solvent Extraction Unit at Savannah River Site is accomplishing an 

important mission need (i.e., generating tank space) while providing a radioactive test bed 

and data for the design and construction of the larger-scale Salt Waste Processing Facility.

5) Provide for flexibility in the scaled-up process. This will allow process upsets and 

unexpected process difficulties requiring some process changes to be accommodated. 
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6) There currently exists a significant body of knowledge, expertise, and separations capabilities 

within the DOE complex that must be preserved. An effort should be undertaken to define 

the appropriate functions of a possible center for separations knowledge, as well as

inventorying the facilities that could be used to support separations scale-up over the next

five to twenty years. 

7) Advancing the capability to conduct small-scale, integrated radiochemical processing with 

actual material will be beneficial, and this would likely involve improved process monitoring 

and control that could be applied in the actual plant. 

8) An opportunity and technical challenge for improving the capability to do process scale-up 

with less experimental testing and at smaller scales is to develop improved modeling 

capabilities for common and essential process physics and chemistry where scale-up issues 

are known to be difficult. 

9) Ancillary issues include the need for a broad-based, bi-partisan solid foundation to maintain 

and advance these issues in the United States. 

Figure 5. Scale-up cycle
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Appendix D. Breakout Session Report: Interface 

Issues between Separations and Waste 

Forms/Fuel Fabrication 

CHAIR: David Kosson, Vanderbilt University

CO-CHAIR: Bob Sindelar, Savannah River National Laboratory

FEDERAL COORDINATOR: James Marra, Office of Environmental Management 

ORGANIZER: Bill Wilmarth, Savannah River National Laboratory 

PANELISTS:

Ken Bateman, Idaho National Laboratory 

Charles Forsberg, Massachusetts Institute of Technology 

Werner Lutze, The Catholic University of America

Tina Nenoff, Sandia National Laboratories 

Eric Shaber, Idaho National Laboratory – Battelle Energy Alliance 

George Vandegrift, Argonne National Laboratory 

1.0 Background Information 

The interfaces of nuclear fuel separations processes to the production of waste forms and to fuel 

fabrication should be considered within an even broader context of the entire nuclear fuel cycle 

for nuclear power production. Radioactive wastes are generated from uranium mining, 

conversion and enrichment, fuel fabrication and conditioning, and fuel recycling. Past waste 

management practices have produced additional technical challenges, such as the need for pretreatment of tank wastes prior to further processing. Wastes from post-separations streams pose 

challenges to any closed nuclear fuel cycles, along with the purity of recycled uranium and 

burnable actinides either as an integral part of the fuel or as a separate target in a reactor core. A 

modified open fuel fabrication cycle requires waste forms and disposal pathways for actinides 

and fission products removed during the minimal reprocessing (see Section 1.2 of this report for 

a brief discussion of the three fuel cycles under DOE-supported study). 

While the fuel cycle for nuclear power is a dominant concern, disposition should also be 

considered, including stabilization for disposal and potential recycle of materials and wastes 

generated from other reactor cycles, such as the production of molybdenum-99 (Mo-99) for 

medical uses using low-enriched uranium (LEU) fuel. Therefore, a holistic vision must be given 

to any nuclear fuel cycle to ensure that the selected alternatives for each of the major parts of the 

nuclear fuel cycle (see Figure 1) would mesh with each other prior to their specification. 
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Furthermore, the system should be designed in a flexible manner so as to enable incorporation of 

novel materials, methods and processes from research institutions such as national labs and 

universities in real-world settings post-engineering development and/or infrastructure 

construction completion. In this regard, an overarching systems analysis is a foundation from 

which the interfaces are well identified.

Fuel cycle selection for the present U.S. reactor fleet (104 operating reactors with 65,000 MTHM 

used nuclear fuel in storage) and for near-term additions to the fleet with advanced light water 

reactor (LWR) designs is sufficiently mature to facilitate identification of transformational 

technology opportunities in fuel design, waste form specification, repository selection, and other 

fuel cycle component considerations. Further development of specific fuel cycle component 

technologies will provide alternatives for consideration; subsequent systems analyses will enable 

risk-informed selection of the “best” cycle(s) with explicit cost–benefit information. Risks 

include safety and security considerations and programmatic risks or risks in achieving stated 

goals (e.g., development of a single glass waste form for sequestering multiple waste species 

must be evaluated against multiple sets of waste forms optimized for waste volume loading and 

durability, but would require additional separations processing and associated risks). “Waste 

Figure 1. Nuclear fuel cycle for power reactors showing direct linkages of (proposed) 

spent fuel reprocessing or separations with fuel fabrication and waste forms destined 

for final disposition [reproduced from BRC report, figure A1]

**Note that the recycled uranium may be enriched as precursor to fuel fabrication. Also, transuranic (TRU) waste (with longlived actinides) would likely be part of the stream for fuel fabrication to enable their burn-up in reactor.
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Forms Development and Technology,” published by the National Academies of Science, 

supports this point and recommends reevaluation of the one-glass waste form, recommending a 

“good as glass” approach (see below). 

 

U.S. Department of Energy and National Nuclear Security Administration 

Programs 

The U.S. Department of Energy (DOE) Office of Nuclear Energy (NE) Fuel Cycle Technology 

(FCT) program investigates fuel cycle components for commercial reactors. NE identified many 

program needs in common with the DOE Office of Environmental Management (EM), including 

interim to long-term storage and the ultimate disposition of spent nuclear fuel and orphan legacy 

materials (e.g., U-233). Repatriation of enriched uranium and other materials to the United States 

by the National Nuclear Security Administration (NNSA) carries attendant storage and 

disposition needs. Furthermore, critical medical isotope production (e.g. Mo-99) also presents 

program needs.1

1. The FCT Separations Campaign Implementation Plan

 All these nuclear materials are subject to monitoring and security functions. 

Publicly available documents detail DOE and NNSA program activities:

2

2. The Waste Forms Campaign Implementation Plan

 provides an overview of the 

campaign activities plan: “Develop the next generation of fuel cycle separation 

technologies that enable a sustainable fuel cycle, with minimal processing, waste 

generation, and potential for material diversion.” 

3

3. Tank Waste Retrieval, Processing, and On-Site Disposal at DOE-EM 

describes the affiliated campaign for 

development of waste forms from the waste streams that would emanate from the 

separations processes and would be subject to repository disposal. This campaign seeks 

to produce high-waste-volume-loading forms that are highly durable in, and tuned to, 

specific repository environments.

4

4. The Technology of Waste Forms

provides an 

overview of the remaining technical challenges involved in, predominantly, processing 

and immobilizing HLW, describes the need to better understand the chemistry of HLW 

stored in tanks and DOE sites, and notes that there are still substantial opportunities to 

use science and technology to improve the processing and immobilization methods to be 

used by the Department. 

5 picks up where the above report and several others left 

off.6

 

1 Medical Isotope Production Without Highly Enriched Uranium, National Research Council of the National 

Academies, the National Academies Press, 2009.

 This report provides a detailed description of the basic science and technology of 

2 Todd, T.A. FCRD-SEPA-2010-000042, Separations Campaign Implementation Plan, March 2010. 3 Vienna, J.D. FCRD-WAST-2010-000043, Waste Forms Campaign Implementation Plan, March 2010.

4 “Tank Waste Retrieval, Processing, and On-Site Disposal at Three Department of Energy Sites,” National Research 

Council of the National Academies, the National Academy Press, 2006. 

5 “Waste Forms Technology and Performance,” The National Academies Press, 2011. 
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HLW forms. It notes that there are substantial opportunities to use scientific and technical 

advances to improve processing and immobilization processes and urges a risk-informed, 

systems approach to decision making regarding processing and immobilization processes 

and, by implication, R&D. 

5. Waste Forms for an Advanced Fuel Cycle7

6. Reactors and Fuels

 provides a brief summary of the definitions 

and present regulations, requirements, and standards along with performance of waste 

forms and engineered barrier systems in the disposal environment that drive their 

development. Radioactive wastes are classified, primarily based on origin, as high-level 

waste (HLW), low-level waste (LLW) including greater than Class C, and mixed waste. 

This origin-based classification system impedes efficient waste management and 

environmental protection, as well as limiting development of new waste forms. For 

example, borosilicate glass, the waste form developed by EM and used in production for 

defense programs’ HLW for the past 15 years, is the only mature HLW form available in 

the United States. Future waste forms that are close to equilibrium with the disposal 

environment would simplify disposal facility design with respect to need for engineered 

barriers. Waste form design should consider geologically stable materials and use natural 

analogues as part of long-term durability assessment. 

8

7. Fuels Campaign Report

 notes the present design and advancing future fuel designs are 

directly tied to reactor design, and there are typically tight purity limits on feed (e.g. from 

recycled uranium) materials.

9 discusses fuel for actinide burners and advanced fuels of metal, 

oxide, and particle designs being considered in the fuels campaign of the FCT program. 

Nuclear Separations Technologies Workshop Presentations 

The following sections summarize the principal points of panelist presentations and the ensuing 

discussions from the two-day workshop (presentations are available on the NE website: 

http://www.ne.doe.gov/).

 6 For example, “Advice on the Department of Energy’s Cleanup Technology Roadmap: Gaps and Bridges.” National 

Research Council of the National Academy, National Academy Press, 2009. 7 Vienna, J.D. “Waste Forms for an Advanced Fuel Cycle,” monograph from CRESP short course “Advanced 

Introduction to Nuclear Chemistry and Fuel Cycle Separations,” to be published by Vanderbilt University Press, 

2011.

8 Croff, A.G. “Reactors and Fuels,” monograph from CRESP short course “Advanced Introduction to Nuclear 

Chemistry and Fuel Cycle Separations,” to be published by Vanderbilt University Press, 2011.

9 Pasamehmetoglu, Kemal. Advanced Fuels Campaign Execution Plan, INL/EXT-10-18954, October 2010.
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Commercial Fuel Cycle Interfaces: Fabrication and Waste Management—

Interfaces Drive Separations Requirements 

PRESENTER: Charles Forsberg

This presentation and discussion identified grand challenges for the interfaces of fuel fabrication 

and waste management: 

• Capital separations costs are small (<10%) compared to other components in a 

reprocessing plant (e.g., HLW storage). 

• Uranium (U)/plutonium (Pu) ratio blend and purity needs of the fuel drive cost, not the 

separations technology needs. Nonproliferation concerns drive towards lower 

concentration of Pu blend. 

• Traditional reprocessing/disposal system uses separate facilities and locations. A colocated single facility for interim storage, reprocessing, fuel fabrication, and waste 

disposal represents a transformational paradigm (see Figure 2). 

• Improve waste form and repository performance through low waste loadings. There is an 

option to terminate repository safeguards by lowering the fissile content of any wastes 

below the IAEA safeguards termination threshold. There is also an option to improve the 

performance of solubility-limited waste forms by adding nonradioactive isotopes of 

radioactive species to reduce the radionuclide release rate from the waste form (as 

applicable). 

Figure 2. Benefits of Co-Located Nuclear Fuel Cycle Component Facilities [ref. Forsberg]
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Waste Streams from Aqueous and Advanced Separations Processes 

PRESENTER: George Vandegrift 

This presentation and discussion identified several pitfalls for the interfaces of fuel fabrication 

and waste management.

• Reactors and fuel cycles for NE, EM, and NNSA must consider power reactors and 

research reactors. 

• Radiopharmaceutical production presents additional challenges, including reactor/fuel 

system optimization (e.g., to produce uranium–molybdenum LEU fuel for research 

reactors) and waste stream challenges in fuel development and isotope recovery from the 

targets. 

• Radioactive waste generation and waste form interfaces are not limited to backend 

processes but should include the front-end steps of mining, enrichment, etc; look at all 

waste streams. 

• Expediency to produce materials (e.g., weapons-grade materials) did not consider waste 

generation and disposition at the time. 

 

Pyroprocessing 

PRESENTER: Ken Bateman 

This presentation and discussion focused on pyroprocessing technology, its technical maturity, 

and the concomitant waste streams/waste forms.

• Non-aqueous process using molten metals and molten salts with electrochemical methods 

to cause separation of actinides from fission products, cladding, etc. 

• Not designed to recover plutonium, in contrast to plutonium–uranium extraction 

(PUREX)

• Successfully applied to EBR-II fuel reprocessing

• Metal waste form is a stainless steel and zirconium alloy that is highly corrosion-resistant 

and would be expected to be highly durable in repository settings 

• Metallic sodium transformed to sodium chloride

• Vacuum distillation of salts from the claddings

• Salt is captured on zeolite and then is mixed with glass to form sodalite/glass waste form

 
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Fuels and Interfaces with Separations and Waste Forms—Overview 

PRESENTER: Eric Shaber

• Fuel fabrication must meet reactor fuel requirements. 

• Input feed has to allow the fuel fabricator to meet reactor fuel specifications.

• Material composition/purity determines safeguards requirements. 

• Transportation requirements on feed materials that must be shipped are incompatible with 

the feed material forms needed for fabrication; Department of Transportation transport 

between separations and fuel fabrication should be eliminated. 

• Direct oxide reduction processing for metal fuel feed needs to be developed. 

• Improvement is needed with the purity of recycled separations products at present. 

• The modified open cycle is a major challenge for fuel fabrication and reactors; some 

approaches will result in fission product separations during fuel fabrication. 

Waste Forms for the Future 

PRESENTER: Werner Lutze

• Use natural analogs and local conditions of a proposed repository to determine the 

thermodynamically stable material systems. 

• A good record of the waste for waste forms achieved, being developed, and still needed 

include the Hench Panel work,

10,11 the volume edited by Lutze and Ewing,12 and the 

National Academies 2011 waste forms report.

13

• Special waste forms may not be needed—charge to revisit the definitions of waste 

categories. 

• Look at encapsulation as part of waste form development processes. 

• Let nuclides and, if long-term durability is needed, nature guide waste form development. 

• Use modern material science and modeling tools; but in the end, it is nature. 

• Interfaces of separations to waste forms must address the waste form/disposal system. 

 

 

10 DOE, “A Method for Product Performance Evaluation of Candidate Waste Forms for Immobilization of HLW,” 

Report DOE/TIC-11612. DOE Interface Working Group on HLW Form Selection Factors, 1982; available from 

NTIS, Springfield, VA. 11 Hench, L.L., D.E. Clark, and J. Campbell. “HLW immobilization forms,” Nucl. Chem. Waste Management, vol. 5, 

1984: 149.

12 “Radioactive waste forms for the future,” W. Lutze and R. C. Ewing, Eds. North Holland, 1988. 13 Waste Forms Technology and Performance: Final Report ISBN 978-0-309-18733-6, The National Academies 

Press, Washington, D.C. 2011.
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NNSA Needs/Opportunities and Inorganic Materials 

PRESENTER: Tina Nenoff

• Integrated synthesis, characterization, and modeling are recommended to achieve robust 

separations and waste forms. 

• Volatiles, gases, long-lived fission products can be effectively separated and isolated onto 

sensors for detection methods (for NNSA) and/or separated and treated to produce robust 

waste forms with crystalline nanoporous materials, e.g., zeolites, metal–organic 

frameworks, molecular sieves (for NE).

14

• High selectivity paired with high sorption capacity allows for numerous applications in 

waste forms. 

• Research towards metrics and goals is mostly focused on complete separation, isolation, 

and storage. 

• Differing metrics should be determined by needs (e.g., NNSA may have extreme 

sensitivity but not high sorption capacity needs, while NE has high sensitivity with high 

sorption capacity needs). 

• Let nuclides and, if long-term durability is needed, natural analogs guide waste form 

development.15

• A life-cycle (collaborative) approach is needed in designing separations materials so as to 

link as seamlessly as possible with the corresponding waste forms and eventual 

repository needs. 

The following list compiles challenges identified by the expert panel and participants in the 

breakout session. 

1. Establish a baseline fuel cycle with well-defined meshed fuel cycle components. 

2. Establish an approach to down-select fuel cycle components. 

3. Prioritize technology development for an overall “weak” component of the nuclear fuel 

cycle (e.g., a waste form for volatile species) and for further technology development 

among the leading candidates (e.g., “zeolite 1” vs. “zeolite 2” for the volatile species 

waste form). 

4. Develop technologies with low programmatic risk. 

5. Develop management strategies for used fuel storage to allow for radioactive decay, etc.

6. Strengthen the nuclear workforce in the United States. 

 

14 Garino, T.J., T.M. Nenoff, J.L. Krumhansl, D. Rademacher. “Low-Temperature Sintering Bi-Si-Zn Oxide Glasses 

For Use in Either Glass Composite Materials or Core/Shell 129I Waste Forms”, J. Amer. Ceram. Soc., 94(8), 2011: 

2412–2419. 15 Weber, William J., Alexandra Navrotsky, Sergey Stefanovsky, Eric R. Vance, and Etienne Vernaz, MRS Bulletin,

34, January 2009: 46-53. 
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7. Devise a better definition for the waste form/repository interface. 

8. Cultivate buy-in for facilities in the nuclear fuel cycle (e.g., a separations facility). 

9. Strengthen nonproliferation approaches in fuel storage and separations systems. 

10. Obtain Nuclear Regulatory Commission (NRC) licenses for nuclear fuel cycle component 

facilities. 

2.0 Challenges & Proposed Solutions 

The overarching conclusion with respect to interfaces between separations and fuel fabrication 

and used fuel management is the need for a systems approach to guide needed research and 

development that is cognizant of and informs essential national policy decisions regarding fuel 

cycle configurations to be developed (i.e., open, closed or modified), the role and time frames for 

storage of used fuel, the potential for additional processing steps (e.g., fuel “conditioning,” pretreatment of high-level tank waste), and the selection of repositories for disposal of final wastes. 

Development and implementation of a risk-informed waste classification system is central to 

defining radionuclide and materials segregation strategies, waste disposition pathways and waste 

forms. Early down selection of fuel cycle options to a limited set of plausible configurations and 

implementation time frames is central to maintaining efficient progress. The following list 

compiles the proposed solutions, under each respective challenge, in the form of recommended 

programs/activities identified by the expert panel and participants in the breakout session. 

1. Establish a baseline fuel cycle with meshed fuel cycle components well defined. 

Establish a reference set of plausible fuel cycle configurations based on the major driving 

criteria (e.g., economics, safety, environment) that includes high-level definitions of the 

time frames and primary options for each stage of each selected fuel cycle, including 

reactor type, fuel form, storage of used fuel, extent of recycling, waste forms, and waste 

disposition environments. 

2. Establish approach to down select fuel cycle components. 

Develop systems models for each selected fuel cycle option that include initial estimates 

of mass and energy balances, and consider used nuclear fuel currently in storage and to 

be generated. All major primary and secondary waste streams should be identified. The 

potential benefits and risks of co-locating major backend components of the fuel cycle 

(i.e., storage, recycling, fuel fabrication, disposal) should be evaluated. These systems 

models should serve as the basis for identifying major knowledge gaps and what research 

offers the greatest impact on the decision-making process. 

Developing implementation models that define options for the roles and economic drivers 

for private-sector participation should be part of systems evaluation. Caution must be 

exercised in the use of “bounding” assumptions and models to prevent today’s bounding 

assumptions from becoming future constraints that are orders of magnitude too limiting 

compared to evolving science and engineering knowledge. 
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3. Prioritize technology development for an overall “weak” component of the nuclear fuel 

cycle (e.g., waste form for volatile species) and for further technology development 

among the leading candidates (e.g. “zeolite 1” vs. “zeolite 2” for the volatile species 

waste form). 

Prioritize research through a transparent process and set of objectives informed by the 

outcomes of systems modeling. Recognition of the time frames for implementing 

potential fuel cycle options is important for distinguishing urgency for basic and applied 

research and demonstration of different components of fuel cycle options. A joint 

national laboratory, university, and industry advisory committee is recommended to 

ensure consideration of the full development pipeline from basic research through full 

implementation. Research planning should also leverage international partnerships and 

investments.

4. Develop technologies with low programmatic risk. 

Technology development with low programmatic risk necessitates demonstration 

facilities for technology development and deployment. Test beds, including cold and hot 

facilities from bench to engineering demonstration scale, will be essential to the success 

of separations research and development. Pathways and funding for access to hot 

experimentation by university researchers need to be established. Identify potentially 

available and needed facilities (e.g., glove boxes, hot cells, flexible engineering-scale 

demonstration facilities). Implementation of hot testing should be timely in the research 

and development cycle of the waste form (i.e., if implemented too early in 

research/development process, negative data results may inhibit materials optimization or 

improvement). Early use of the facilities should consider EM, NE, and NNSA needs. 

5. Develop management strategies for used fuel storage to allow for radioactive decay, 

etc.

Evaluate the potential role of used fuel conditioning prior to storage, including separation 

of major components and constituents. This is a new concept in response to the potential 

for longer-term storage prior to subsequent recycling or disposal, and may be needed to 

maintain materials stability and facilitate later (and potential unknown) management 

options. 

6. Strengthen the nuclear workforce in the United States. 

Expand the existing NE university program to include nuclear chemical engineering, 

nuclear environmental engineering, and material sciences. These essential components to 

the future of nuclear energy have almost been extinguished owing to the lack of 

investment, faculty engagement, and student interest. Nuclear energy is competing with 

other exciting, hi-tech fields for the best and brightest available minds. DOE and NRC 

should provide programmatic aid in establishing or re-establishing nuclear engineering 

departments in U.S. universities.
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7. Devise a better definition for the waste form/repository interface. 

Develop new and alternative waste forms that can be used to manage the full range of 

recycling waste streams (liquid, solid and gas) and are consistent with planned disposal 

environments. 

8. Cultivate buy-in for facilities supporting the nuclear fuel cycle (e.g., a separations 

facility). 

Conduct research on the social science and communications aspects of implementing 

future nuclear fuel cycles as a component of the emerging research and development 

plan. Ultimately, the public’s and policymakers’ understanding and engagement will be 

central to future decision making and the selected path forward. 

9. Strengthen nonproliferation approaches in fuel storage and separations systems. 

Conduct research on monitoring and instrumentation technologies needed for process 

control and to meet nonproliferation monitoring and remote detection needs. These 

should evolve in concert with process development (note: there is a similarity of needs 

for remote observation with respect to both nonproliferation and environmental 

remediation).

10. Obtain NRC licenses for nuclear fuel cycle component facilities. 

Collect data to support licensing and evaluations by the NRC as part of the planning 

process.

11. Develop a flexible life-cycle system. 

Enable the incorporation of novel materials, methods, and processes from research 

institutions such as national laboratories and universities to be implemented into postengineering development plans and/or infrastructure construction completion. 

An overarching paradigm for prioritization of recommended programs/activities is that LWR 

technologies are near-term vis-à-vis advanced burner reactors. In addition to the DOE and NNSA 

programs, common needs and program information-sharing with international partners is critical 

to enable cost-effective, technically sound selection of the components of the nuclear fuel 

cycle(s) for the U.S. energy needs. 

The conclusion, with respect to interfaces between separations and fuel fabrication and used fuel 

management, is the need for a systems approach to guide research and development that is 

cognizant of and informs essential national policy decisions regarding fuel cycle configurations 

to be developed (i.e., open, closed or modified), the role and time frames for storage of used fuel, 

and the selection of repositories for disposal of final wastes. Development and implementation of 

a risk-informed waste classification system is central to defining radionuclide and materials 

segregation strategies, waste disposition pathways, and waste forms.
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This easily can become a “which comes first: the chicken or the egg?” dilemma. Early down 

selection of fuel cycle options to a set of plausible configurations and implementation time 

frames is central to maintaining efficient progress and avoiding paralysis. NE has initiated a 

process to achieve recommendations on such a down selection in FY 2013. 

Bibliography for Interfaces 

Croff, Allan G. “Reactors and Fuels,” monograph from CRESP short course “Advanced 

Introduction to Nuclear Chemistry and Fuel Cycle Separations,” to be published by 

Vanderbilt University Press, 2011. 

Ewing, Rodney C. “The Design And Evaluation Of Nuclear-Waste Forms: Clues From 

Mineralogy.” The Canadian Mineralogist, Vol. 39, 2001: 697-715. 

Ewing, Rodney C. “Nuclear waste forms for actinides,” Colloquium Paper. Proc. Natl. Acad. 

Sci. USA, Vol. 96, March 1999: 3432-3439. 

Ewing, R.C. and M.T. Peters. “A science-based approach to understanding waste form durability 

in open and closed nuclear fuel cycles.” Journal of Nuclear Materials, 362, 2007: 395-

401. 

National Research Council: Committee on Waste Forms Technology and Performance. “Waste 

Forms Technology and Performance: Final Report.” The National Academies Press, 

2011. 

< http://www.nap.edu/catalog.php?record_id=13100> 

Todd, Terry, prepared for DOE. “Separations Campaign Implementation Plan: Fuel Cycle 

Research and Development.” FCRD-SEPA-2010-000042. March 26, 2010. 

Vienna, John, prepared for DOE. “Waste Forms Campaign Implementation Plan: Fuel Cycle 

Research and Development.” FCRD-WAST-2010-000043. March 26, 2010. 

Vienna, John. “Waste Forms for an Advanced Fuel Cycle,” monograph from CRESP short 

course “Introduction to Nuclear Chemistry and Fuel Cycle Separations.” August 4, 2009. 

Additional Questions and Discussions from the Interface Breakout Session 

The breakout session organizers and chairs prepared a set of questions and initial discussion 

“answers” to solicit needs and challenges, along with proposed resolutions, to topics in the 

session. This information is captured below. 

1. What are the advantages/disadvantages of immobilizing separated versus combined 

streams?

Overall waste disposal strategies have much greater flexibility with separated streams. 

The advantages include producing tailored waste forms targeted to species and hazard 

level, enabling thermal management of high-activity species, enabling radiological 

management of high-activity species, and volume reduction. However, process costs 

(separations process development, waste form development, facilities to execute the 
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separations and waste form production) and risks associated with these process steps are 

the disadvantages.

Additional discussion points: 

1. It would be more advantageous to co-location, including the safeguards aspect. 

Convert HLW from separations into heat waste and store to reduce heat. Examine 

concepts for fuel conditioning. 

2. Plutonium is not allowed in facilities licensed to make fuel. 

3. Calcine waste at ID could not be put in YMP; it was not in the TSPA analysis. 

4. Head-end cycle to separate iodine and technetium can help in waste management

(also cesium and strontium). 

5. Think about advantages for separations. 

6. Certain things in PA need waste forms. Doing that requires clean fuel and bad 

actor species separated.

7. The safety basis is easier to deal with. It could be demonstrated with a cross-over 

point in the analysis where that need to separate occurs.

2. What separations processes and conditions adversely affect or facilitate waste form 

chemistry and processing?

The attendant radiation of the radioisotopes in the irradiated fuel is one clear example of 

a challenge to waste form chemistry and processing. Separations and concentration of 

radionuclides can lead to radiolysis effects and highly radioactive process solutions that 

can complicate waste form processing. Furthermore, high radiation levels can damage 

and reduce the performance of resins and similar ion exchange and separations media. 

The solution chemistries themselves—including aqueous solutions and solvents, and the 

chemical species introduced into the stream to facilitate separations—can dramatically 

impact waste form chemistry and its processing. A clear example is sulfur that becomes 

part of the raffinate in the TRUEX process. The relatively low solubility of sulfur in 

traditional waste forms creates challenges. Such chemical challenges have historically led 

to the need for additional processing of HLW (i.e., pre-treatment) and reinforce the need 

for integration between separations and immobilization R&D efforts.

3. What new advances in waste form chemistry and processing can be applied to an 

advanced fuel cycle or other challenging wastes? 

Borosilicate glass is the current world-wide standard for immobilization of high-level 

radioactive waste resulting from reprocessing. Lower-activity wastes have been primarily 

immobilized in grout and similar matrices. Although there has been significant work in 

evaluating alternative waste forms over the years, few of these developments have gone 

into practice. Can a “good as glass” performance policy be implemented that allows for 

HLW to be stored in novel, non-borosilicate glass waste forms? Advances in chemistry 

including nanomaterials and functionalized materials could lead to transformational 
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advances in waste form development. For example, ligands tailored to bind species have 

the potential to optimize waste species capture and sequestration.

Advanced separations processes including ionic liquids and gaseous separations using 

fluoride chemistry have potential for highly selective separations and non-aqueous, lowvolume waste streams. The impacts (positive or negative) of these types of separations 

methods on waste form chemistry and fabrication is not known. 

4. What fundamental waste stream characteristics need to be known to select and develop 

waste forms?

The inventory and chemical form of species in the waste stream solids and solutions of 

course provide important waste stream characteristics needed to develop the waste form. 

Perhaps, more subtly, the matrices containing the radionuclides can have significant 

impacts on waste processing. For example, rheological properties of waste streams—

those that are not easily mimicked using simulants—can cause significant issues with 

waste processing. Radionuclide types and concentrations can cause wide variations in 

thermal heat loads and radiation doses. All these factors are important considerations in 

the selection of separations and waste form production processes and the interplay 

between these areas. It is important to know the limitations of use of simulants in 

separations and waste form research and development; while it is vital to advance the 

knowledge base and research, it is important in the end to be able to test with real/hot 

radionuclides for ultimate performance evaluation.

5. What advances in fuel technology can facilitate reprocessing?

To date, the development of fuel with a direct consideration to backend separations and 

waste form conditions is weak at best. Typically, considerations were made to optimizing 

fuel reactor performance and integrity in both normal operations and accident scenarios. 

To truly develop an integrated approach for the fuel cycle from fuel production to waste 

management, a systematic approach must be undertaken throughout the fuel cycle 

process.

Additional discussion points: 

1. Different reactor designs require specific fuel. Do we need multiple separations 

facilities for the various metal, oxide, etc., fuel design, or can we have one feed fit 

all?

2. For what type of reactor are we trying to design fuel? 

3. We are trying to open reactor designs up to higher enrichments. Maybe one can 

tolerate higher impurities.

4. The fuels program is looking at oxide, metal and particle fuel. MOX fuel with an 

actinide target would simplify assumptions. 

5. Higher and higher burnups are desired. 
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6. Is there a compromise interim option entailing storing U3O8 that would allow 

offshoots down the road—; perhaps MOX is good interim fuel cycle type (other 

actinides and enrichments uncertain). Remote fabrication of fuel with actinides 

would be needed. Straight metal fuel is very simple to make in a hot cell.

6. How does fuel design impact reprocessing strategies (open cycle, modified open cycle, 

closed cycle)?

High-integrity fuel that can withstand long service and accident demands lends itself to 

an open fuel cycle because of resistance of the cladding to breakdown. It is obvious, 

however, that high-integrity fuel would make fuel reprocessing in modified open or 

closed fuel cycles more difficult. It is evident that fuel design optimization must also take 

into account specific reprocessing strategies and/or the need to incorporate flexibility into 

fuel designs. 

7. What are the needs and how can modeling and simulation tools be used to support fuel 

and waste form development and optimization?

Advances in high-power computing can help speed scientific discovery if appropriately 

harnessed. The current NE Nuclear Energy Advanced Modeling and Simulation 

(NEAMS) and EM Advanced Simulation Capability for Environmental Management 

(ASCEM) programs are establishing advanced computing capabilities to support NE and 

EM program needs. The use of these tools for fuel and waste form development and 

optimization, specifically as they relate to the integrated fuel cycle, could help speed 

development by supplementing experimental and development activities. 

8. What are the political and economic considerations that must be accounted for in fuel/

separations/waste form interfaces?

Nuclear processes and facilities are complex and, thus, typically expensive to design, 

construct and operate. Additionally, safety systems associated with nuclear facilities are 

expected to be robust. Public and political views on the cost and safety of nuclear 

facilities and processes vary significantly. The recent incident at the Fukushima Daiichi 

nuclear power plant in Japan has only increased the disparity of these views. These 

political and socio-economic factors must be considered in considering an integrated fuel 

cycle. Specifically, the disposition of used fuels and wastes, and safeguards associated 

with handling and processing nuclear materials, must be all be considered collectively 

and systematically in formulating informed and defensible decisions on fuel cycle 

options. 

Additional discussion points: 

1. A systems study is needed. We need to expedite R&D and deployment. 

Integration needs to be more along sloshing than linear, but needs focus. 

2. The question needs to consider disposal too. UFD is looking at salt and clay. Risk 

in Belgium is from fission products, not actinides. 
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3. Consider a joint EM and NE and international glass corrosion program. Check 

against, salt, clay, tuff, granite. We need more of that kind of thinking for 

disposal. 

4. The disposal system has to be risk-informed. 

5. Glass models should not be overly conservative. 

6. The near field is critical. We must know what the glass response is in each 

environment. 

7. Do we consider the waste package when we think of waste form? Reducing 

environment keeps technetium and neptunium immobilized. 

8. We should encourage thinking of enabling fuel cycle options. Look at the whole 

cycle to make sure all parts have alternatives.

9. We have not resolved what to do with our waste and should show the public we 

are working on it. 

10. Swiss looked at overpack and waste form interactions. 

11. There are risks and significant costs associated with the current approach of doing 

nothing while researching to find the perfect solution set. 

9. What are the future workforce needs and challenges associated with fuel and waste 

form development areas?

The present workforce with experience in fuel and waste form development is “graying,” 

similar to most other nuclear-related disciplines. Research work in these areas in the 

United States was generally limited and sporadic from the early 1990s through about 

2008. Over the past few years, there has been an increase in research work in these areas 

with the resurging interest in nuclear energy. Throughout these periods, the experience 

base was definitely impacted because of retirements and reassignment of personnel. On a 

positive note, skill sets of recent graduates appear to be adequate with appropriate 

mentoring to fill personnel needs. It is expected that there will be a continued need for 

material scientists, chemists, physicists, nuclear engineers, chemical engineers and 

mechanical engineers to support fuel and waste form development activities. Experience 

with nuclear materials would expedite indoctrination of new employees. As noted above, 

modeling and simulation expertise may be extremely beneficial for future development 

work. Furthermore, owing to the complex nature of the nuclear fuel processes and need 

for integration of fuels, separations and waste processing functions, expertise in systems 

engineering and decision-making processes may be crucial in identification, evaluation 

and selection of the future fuel cycle alternatives. Related DOE agencies and NRC should 

help establish or re-establish new nuclear engineering undergraduate and graduate 

programs at universities in the United States, in a timely manner.
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Additional questions:

1. Which radionuclides should be grouped together or managed separately as a 

result of separations processes for most effective waste management?

2. Which constituents are most likely to limit waste loading into waste forms? What 

separation approaches can be taken to reduce these limitations?

3. What are the disposition pathways for all used fuel components (not just 

radionuclides) and chemicals and components used as part of advanced fuel 

cycle separations? Which present the greatest challenges?

4. How can constituent immobilization be factored into design of separations 

processes?

Additional discussion points: 

1. Joint EM and NE glass corrosion. This would give us corrosion law. Borosilicate 

glass is used. 

2. Fundamentally, for high-level waste, phosphate glass gives us high-waste loading. 

Reduced volume would result. 

3. EM work on advanced silicate glasses is important too. 

4. Should also look at other glass systems.

5. Need to take a “systems look” at glass.

6. People are unable to move forward because decision makers are unwilling to 

commit to any path. Beyond-bench-scale R&D is needed. NEED DEMO 

FACILITY FOR BACK END FUEL CYCLE. Most efforts could be started right 

now, including capture. 

7. Everyone likes waste loading high. But need to look at simplicity and stability of 

materials in proposed repository settings. For example, Swedes have package and 

clay that is simple and would last a long time. That is what we need to do. Native 

copper in Sweden is convincing as a stable barrier material.

8. Make case for simplified waste form.

9. Make case for re-classification of waste to manage waste streams.

10. Lack of places for students to work quickly with uranium, etc. Need places to do 

research. Need glovebox, hotcell, user facilities for universities to use. 

11. ITU in Karlsruhe is a “hang out” for gloveboxes. 

12. Process modeling and monitoring needs attention. Pu mass balance needs to be 

monitored. Am-243 and Np-239 are mother/daughter pair that should stay 

together. Need science-based models, need smart process controls. 

13. Good, clear communication on safety basis for repository disposal of waste forms 

is paramount. 
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14. Glass waste forms in near field have a good base, but not on waste package in 

equilibrium with environment. 

15. Waste loading and fuel. 230,000 used assemblies to date. The United States has 

unique gas release regulations. Need to determine what fuel could be recycled in 

the United States and then determine waste form. 

16. Repository accommodation of heat load, etc., dictates.

17. Even with ventilation, have near-term Cs/Sr challenges with heat load. 

18. Look at YMP 96°C mid-fill is T-controlled. Look at T drivers. 

19. Risk-informed PA should be considered. 

20. Advanced separations funding: should it be industry or government? If industry, 

how will use incentivize industry to separate out actinides? MOC is looking at 

advanced separations. In long-term ionic liquids (IL), molten salts have a lot of 

research interest. From engineering in short term, look at head end—gases and 

cladding clean up. If you have time, room-temperature solvent extraction would 

be good to have developed. Give needs on waste form and fuel to separations guys.

21. Need to give lessons learned and other informed needs to separations. Take out 

aluminum before or as part of processing, for example. 

22. Question on EM for H-canyon at SRS. DNFSB says we should continue Hcanyon. Need for test bed and H-canyon would serve that purpose. 

23. Nuclear industry moves in small steps by adapting technology. Need near-term 

generic goals. Iodine capture, zirconium recovery.

24. Need for balanced university–lab–industry panel as advisors.

25. New exciting separations will occur. Supercritical liquids is exciting, but large 

pressurized cells are not amenable to quick demo.

26. IL are not readily handled.

27. Separations community has lack of direction. Maybe BRC will help. Need to 

ensure that this report will not be just another committee report thrown in trash.

28. We do want to produce a report that identifies common needs. Pace of program 

dependent on funding, but we want to do the right things when the time comes. 

We want to refer back to this document for ideas. 

29. Look at adaptive strategy—interim storage and adaptive processing. Look at offroads rather than endpoints.
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Appendix E. Workshop Sponsors 

Office of Nuclear Energy (NE) – NE is evaluating next-generation fuel recycling technologies 

that are alternatives to PUREX. Safety and security concerns surrounding civilian nuclear power 

must be successfully addressed in the United States and globally. By taking a leading position in 

helping to craft the international nuclear technology “rules-of-the-road” and providing a sound 

technology base for their implementation and enforcement, the Department can facilitate safe 

and environmentally acceptable approaches to recycling nuclear fuel while reducing greenhouse 

gas emissions and maintaining public confidence. NE’s mission includes research and 

development in search of fuel-cycle technologies that improve resource utilization while 

reducing the risk of proliferation. 

Office of Environmental Management (EM) – EM is conducting the world’s largest nuclear 

clean up of the environmental legacy of nuclear weapons production and government-sponsored 

nuclear energy research, which has been vital to our Nation’s security. To complete this mission, 

EM is developing next-generation technologies for waste treatment, groundwater and soil 

restoration, nuclear materials stabilization and disposition, and facility decommissioning. EM 

will enable nuclear futures by expertly and safely managing nuclear materials and waste, 

developing a skilled nuclear workforce, and supporting the creation of technologies that can be 

transferred, refined or retooled for energy, defense or security applications. 

National Nuclear Security Administration (NNSA) – In support of national nonproliferation 

objectives, we are examining new approaches and technologies to dispose of surplus weapons 

grade materials and advance other national security missions. U.S. commitments to dispose of 

surplus weapon-grade plutonium to ensure it cannot be used again for nuclear weapons require a 

safe, secure, transparent, and effective disposal process. 

Office of Science (SC) – SC enables new technologies that support the Department’s energy, 

environment, and security missions. These basic research programs address fundamental 

questions. Enabling activities in support of Goal 3 include the development and exploration of a 

broad spectrum of new materials and chemical processes that are radiation-resistant and 

withstand extreme temperatures and pressures.
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Appendix F. Agenda 
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Appendix G. Participant List 
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