Neutrons for the Nation

A report by the APS Panel on Public Affairs

Report Committee

James Wells co-chair, University of Michigan

Julia Phillips co-chair, Sandia National Laboratories (retired)

William Barletta MIT

Robert Birgeneau University of California, Berkeley

Robert Dimeo NIST

Francesco Ganda Argonne National Laboratory

William Martin University of Michigan

John Sarrao Los Alamos National Laboratory

Antoinette Taylor Los Alamos National Laboratory

Norman Wagner University of Delaware

APS Staff

Francis Slakey APS Chief Government Affairs Officer

Jeanette Russo Manager of Operations

Allen Hu Policy Analyst

6/5/2019
Motivation for the report

• How important are neutron sources for science, engineering, and 

industry for the foreseeable future?

• What neutron source characteristics are important? How are such 

neutrons produced now and in the near future?

• What does the U.S. need to do to be a global player in neutron 

science, engineering, and applications in the coming decades?

• What policy issues need to be considered in designing and building 

future neutron sources?
Neutrons ARE important for science, 

engineering, and industry

• Neutron scattering – as one of an ensemble of techniques

• Physics of the neutron

• Materials testing

• Isotope production

• Transmutation

KEY FINDING

Investigations performed at neutron sources are essential 

components of R&D in numerous areas of science and engineering.
Neutron scattering is an essential component 

of an ensemble of research techniques

• Complementary techniques:

• Materials synthesis and “in lab” characterization

• Light sources

• Computational simulations

• NMR

• Advances in instrumentation at neutron sources have dramatically 

increased the capabilities of the facilities

KEY FINDING

Neutron scattering is often an essential part of a broader 

experimental study that uses a complementary suite of tools.
U.S. neutron R&D is vulnerable

Major neutron scattering facilities (2017)

• Significant world-wide activity in 

source (spallation and reactor) 

and instrument construction and 

commissioning

• Smaller facilities contribute to 

overall regional productivity

• US capacity (number of 

scattering instruments) peaked in 

1996

• No HPRR has been commissioned 

in the U.S. in 50 years

KEY FINDING

The U.S. has lost 

important capability in 

neutron R&D in the last 

2 decades and is no 

longer the world leader.
Need

High performance research reactors 

are important for neutron research, 

development, and production

Uniquely or especially suited for:

• Materials testing

• Isotope production

• Capacity to support many 

experiments

U.S.-based HPRRs use highly enriched 

uranium fuel* (HEU)

• HEU constitutes a proliferation risk.

• U.S. policy dictates eliminating HEU in 

civilian applications wherever possible.

• Converting existing U.S. HPRRs to low 

enriched uranium is not possible with 

existing fuel.

KEY FINDING

Current high performance research 

reactors (fueled by HEU) provide 

unique R&D capabilities relative to 

other neutron sources available today.

KEY FINDING

Reactor fuels containing highly enriched 

uranium represent a risk for 

proliferation, which should be 

considered when planning for the 

future infrastructure for neutron R&D.

*HEU – enriched 235U content > 20%

and Challenge
World-class neutron R&D currently requires 

three things

Spallation Sources:

• Peak pulse intensity

• Time-dependent 

measurements

• Accelerator-based (no 235U)

High-performance instrumentation

• Computing & data analytics

• Beamline instrumentation

Research Reactors:

• Capacity to support many experiments

• Higher time-averaged flux

• Larger irradiation area

• Spectrum characteristics

KEY FINDING:

World-class neutron science & engineering require

the complementary capabilities of spallation

facilities, research reactors, and highperformance instrumentation. While

there is some overlap in the capabilities of spallation and reactor

sources, each provides 

capabilities that cannot

now be duplicated

by the other 

type of

source.
The path forward - RECOMMENDATIONS

The U.S. should:

1. Continue to support a diversity of neutron R&D capabilities, including both 

research reactors and spallation sources 

and strike a balance between retaining/enhancing current neutron capabilities 

and reducing/eliminating use of HEU.

2. Sharply increase investment in neutron instrumentation development and 

deployment to leverage R&D capacity and capability and to complement 

continuing investments in complementary tools such as light sources and high- performance computing.

3. Reaffirm its commitment to the timely development and deployment of high- density LEU fuels for existing HPRRs.

4. Initiate an effort to competitively design and build a new generation of LEU- fueled HPRRs that would satisfy all needs that rely on current HPRRs.
Other considerations

• The lead time for commissioning a new HPRR (of 

any type) is very long.

• Development of very high density LEU fuels 

appropriate for converting existing HPRRs has 

taken MUCH longer than originally anticipated, 

and the timeline has moved out repeatedly.

• Can all of the uses of HPRRs be met without the 

use of HEU?

• Can/should all of the current uses of HPRRs be 

met in an single LEU-fueled HPRR?

• Are there other (non-HPRR-based) innovative 

approaches to satisfying all of the needs currently 

met by HEU-fueled HPRRs? Available at:

http://www.nap.edu/21818