# Report of the Topical Group on Neutrino Applications for Snowmass 2021
Submitted to the Proceedings of the US Community Study on the Future of
Particle Physics (Snowmass 2021)

N. S. Bowden  Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
J. M. Link  Center for Neutrino Physics, Virginia Tech, Blacksburg, Virginia
24061, USA  W. Wang  Sun Yat-Sen (Zhongshan) University, Guangzhou, China
on behalf of the NF07 Applications Topical Group Community

###### Contents

  1. Executive Summary
  2. 1 Introduction and Motivation
  3. 2 Applications of Neutrino Physics and Supporting Technologies
    1. 2.1 Application of Technologies Developed for Neutrino Physics
      1. 2.1.1 Isotope Extraction and Enrichment
      2. 2.1.2 Accelerator Technology
      3. 2.1.3 Radiation Detection Technology
    2. 2.2 Direct Application of Neutrinos to Nuclear Security and Nuclear Energy
      1. 2.2.1 Fissile material production monitoring
      2. 2.2.2 Reactor discovery and exclusion
      3. 2.2.3 Monitoring of spent fuel and reprocessing waste
  4. 3 Nuclear Security and Nuclear Energy Applications – An End-User Perspective
    1. 3.1 The Nu Tools Study
    2. 3.2 Use Cases with Potential User Interest
      1. 3.2.1 Advanced Reactor Safeguards
      2. 3.2.2 Future Nuclear Deals
      3. 3.2.3 Spent Nuclear Fuel
      4. 3.2.4 Post-Accident Response
    3. 3.3 Use Cases with Limited User Interest
      1. 3.3.1 Current International Atomic Energy Agency (IAEA) Safeguards
      2. 3.3.2 Reactor Operations
      3. 3.3.3 Non-Cooperative Reactor Monitoring or Discovery
  5. 4 Synergies with Particle Physics
    1. 4.1 Prediction of the Reactor Flux and Spectrum Source Term and Related Nuclear Data
    2. 4.2 Physics topics accessible using Near-field Inverse Beta Detectors
    3. 4.3 Physics topics accessible using CEvNS and Reactor Neutrinos
    4. 4.4 Physics topics accessible using Mid & Far-field Inverse Beta Decay Detectors
    5. 4.5 Detector Technology Development Topics with Mutual Benefit to Particle Physics and Nuclear Security
    6. 4.6 Workforce Development for the Particle Physics and Nuclear Security Communities
    7. 4.7 Facilities
  6. 5 Conclusions and Next Steps
    1. 5.1 Inter-agency Coordination
    2. 5.2 End-user Engagement
    3. 5.3 Current Application-oriented Technology Development Efforts
  7. 6 Acknowledgements

## Executive Summary

In addition to the pursuit of fundamental knowledge, investment in scientific
discovery is also motivated by the development of technologies and the
training of a skilled workforce that can benefit society in other ways. In the
case of Neutrino Physics, there are many instances of this dynamic playing
out. But somewhat surprisingly, given the inherent difficulty of neutrino
detection, the direct application of neutrinos to advance other fields of
research or solve societal problems is also a possibility. Examples of direct
neutrino applications include monitoring of nuclear reactors for safeguards
and nonproliferation and the probing the Earth’s interior via it’s neutrino
emissions and tomography.

There are strong synergies between the neutrino physics topics of community
interest developed through this Snowmass process and direct neutrino
applications. These synergies can take the form of overlapping needs in terms
of technology development, workforce capabilities, facilities, and underlying
scientific knowledge. Specific examples of synergies highlighted during
Snowmass include:

  * •

Improved knowledge of the reactor neutrino emissions (flux and spectrum) is
needed for reactor monitoring applications and would enable reactors neutrinos
to continue to be a tool for discovery;

  * •

Neutrino detectors using the inverse beta decay or CEvNS channels with
improved background suppression operating close to reactors can help to
address neutrino anomalies, probe BSM physics, and provide versatile
monitoring capabilities;

  * •

Technologies that could reduce the cost and improve the performance of large
inverse beta decay neutrino detectors could provide reactor monitoring at
larger distances and address a wide range of neutrino physics topics;

  * •

Projects at the intersection of neutrino physics and neutrino applications can
provide broad training opportunities for community members while also opening
new career pathways.

The fact that technologies and workforce capabilities developed by the field
of Neutrino Physics can have benefits in many other areas of science and
society provides an additional motivation for societal investmen. To further
advance our field in this respect, it is important that community members have
such possibilities in mind and actively seek opportunities to highlight the
broader impact of their research. It is also critical to note that the full
impact of neutrino applications can only be realized through early and
attentive engagement with experts from potential end user communities.

Given the strong synergies between neutrino physics and neutrino applications
noted above, it is apparent that stakeholders from both communities would
benefit from further coordination. This could take the form of joint
investment in detector R&D efforts, measurements to improve our knowledge of
reactor emissions, and/or reactor-based experiments and demonstrations.

##  1 Introduction and Motivation

The pursuit of science is a great endeavour, that in addition to creating new
fundamental knowledge, improves our well-being through education and by
enabling new technologies [1]. In this Topical Group Report on Applications of
Neutrino Physics, we explore these latter two functions of our collective
endeavour. Here, we will explore and develop the overlap between applications
and active fields of research within the neutrino community, while also
highlighting areas where stronger connections could be developed with other
disciplines, user communities, and sponsor agencies.

Since the technology and skills that neutrino physicists develop are often
pushing the boundaries of what can be achieved, it is natural that they might
also solve problems beyond our specific discipline. Furthermore, as our
knowledge of the underlying neutrino physics continues to improve in concert
with detector technology, the door has opened to using the unique nature of
the neutrino to access information where it is otherwise difficult or
impossible.

This report is structured as follows. Section 2 begins with descriptions of
several areas where Neutrino Physics and it’s supporting technologies find
actual or potential application to other areas. Particular emphasis is given
to the possible direct use of neutrinos to solve problems in Nuclear Security
and Nuclear Energy. An active sub-field has grown around the idea using
electron antineutrinos released as a by-product of nuclear fission for this
purpose. Section 2 concludes with a description of potential capabilities
conceived primarily by neutrino physicists, after which Section 3 gives the
perspective of potential end-users of what would be a rather novel
technological approach.

A central theme of community input and this report is that Neutrino Physics
and potential Applications can mutually benefit from continued engagement and
investment. Section 4 develops this theme by examining synergies between
scientific and application topics. This report concludes in Section 5 with an
examination on Next Steps that we as a community can take to fully realize
these synergies, advance both the fundamental and applied aspects of our field
and continue to benefit society in the broadest possible way.

##  2 Applications of Neutrino Physics and Supporting Technologies

Applications of Neutrino Physics can be approximately grouped into two
categories: (1) areas that benefit from technologies and skills developed in
the pursuit of neutrino physics and (2) areas where neutrinos themselves can
be used to address a need, which in turn requires an understanding of neutrino
production and neutrino properties, plus the ability to detect neutrinos. In
this section we give several examples of category (1), but by no means
identify all such applications. The consistent theme that we wish to highlight
with these examples is that the pursuit of new neutrino knowledge requires
physicists to develop new and improved technologies, which can also redefine
what is possible in other areas. And of course, the converse is also true
where advances developed for other purposes open new lines of pursuit in
Neutrino Physics.

The second category, use of neutrinos to address needs in other fields, is a
relatively recent development, the small size of the weak interaction and the
consequent difficulty of neutrino detection limit the opportunities for direct
application. Several direct applications have emerged in recent years. The use
of ‘geoneutrinos’ to probe the inner structure of the Earth will be covered by
the NF04 ‘Neutrinos from Natural Sources’ Topical Group. Neutrinos from a
variety of sources could also be used for tomography of the Earths interior
[2, 3]. Technically conceivable applications of the electron antineutrinos
emitted as a by-product of nuclear fission, e.g. in reactors, to problems in
Nuclear Security and Nuclear Energy was the subject of several community
submissions to Snowmass and will be covered here.

###  2.1 Application of Technologies Developed for Neutrino Physics

####  2.1.1 Isotope Extraction and Enrichment

Planning for the next generation of neutrinoless double beta decay
($0\nu\beta\beta$) experiments beyond the tonscale is already underway. Such
experiments would need very large quantities of $0\nu\beta\beta$ isotopes,
which will require new approaches to enrichment in order to be logistically
and economically feasible. To take the specific example of xenon, Metal-
Organic Frameworks (MOFs) for extracting xenon efficiently from enormous
quantities of atmospheric air is one approach that is under development [4].
Such technologies could be applied to atmospheric sampling for radio-xenon
detection in the context of the Comprehensive Test Ban Treaty (CTBT) [5].
Additionally, xenon use in applications is severely limited by its high cost.
Greater availability would have the potential for large societal impact, e.g.
in medicine for anesthesia and medical imaging, and space applications for use
in ion thrusters for satellite stationkeeping [6].

####  2.1.2 Accelerator Technology

Cyclotrons can be an important source of radioactive isotopes needed for
medical imaging, like 68Ge, and cancer treatments, like 225Ac [7]. The IsoDAR
project [8] is developing a high powered cyclotron to produce an intense
neutron beam from 8Li beta decay-at-rest. Due to its high power, the IsoDAR
cyclotron would represent an order of magnitude improvement over the current
state of the art in cyclotron-based medical isotope production.

####  2.1.3 Radiation Detection Technology

There is a long history of detection techniques developed for particle physics
being used for more general radiation detection purposes. Advances in
materials, DAQ, and detection concepts are all potentially relevant to
improving detection capabilities for a wide range of applications like nuclear
nonproliferation, homeland security, and industry. Particle physicists are an
important workforce pipeline into these fields. Here we give a handful of
specific examples of how very sensitive detectors developed for neutrino
physics have been applied elsewhere, and vice versa.

  * •

Over more than a decade, a new germanium diode detector geometry, the P-type
Point Contact (PPC) detector, has been developed to enable high energy
resolution and high efficiency combined with large detector mass. This is
achieved by careful design of internal electric fields and gradient impurities
within the Ge. Detection of low energy recoils from the CEvNS process were a
strong motivation for this development effort (e.g. [9]). This technology
forms the basis for ’Broad Energy Germaninum’ (BEGe) detectors that are now a
standard commercially available product [10]. The very good energy resolution
over a wide energy range and high efficiency of the BEGe geometry is
advantageous for many nuclear counting and spectroscopy applications.

  * •

The basis for the Project8 direct neutrino mass measurement experiment is the
newly invented technique of Cyclotron Radiation Emission Spectroscopy (CRES)
[11]. Here, the energy of a single beta-decay electron is determined with very
high resolution from its cyclotron radio frequency emissions as it propagates
in a strong magnetic field. This technique is already being adapted for high-
precision beta-decay shape measurements for nuclear physics studies [12] and
as a high resolution x-ray spectroscopy technique with application to nuclear
nonproliferation [13].

By way of contrast, very sensitive detectors primarily developed for
applications or other areas of science can enable new neutrino physics
experiments, with a handful described here.

  * •

Superconducting tunnel junctions (STJs) are cryogenic radiation detectors with
ultra-high energy resolution for measurements of low-energy radiation.
Initially developed for X-ray astrophysics and high-resolution soft X-ray
spectroscopy in biophysics and material science, STJs are increasingly also
used in nuclear and particle physics. This includes the characterization of
nuclear recoils and low-energy transitions, e.g. for the development of
nuclear clocks [14]. STJs also enable the search for physics beyond the
standard model, e.g. the BeEST sterile neutrino search [15, 16]. Among
cryogenic detector technologies, STJs are distinguished by their relatively
high count rate capabilities of several 1000 counts/s per pixel.

  * •

Magnetic microcalorimeters (MMCs), also known as metallic magnetic
calorimeters, are cryogenic detectors whose ultra-high energy resolution is
based on measuring changes in magnetization due to the absorption of
radiation. They have been used for high-resolution X-ray, gamma-ray and alpha
spectroscopy. MMCs have also been adapted for decay energy spectroscopy by
fully embedding isotopes of interest into the detector, e.g. to measure the
neutrino mass [17] and to search for the neutrino-less double beta decay [18].
Among cryogenic detector technologies, MMCs are known for relatively fast
detector response with large detector materials [19], which makes it suitable
for low background dark matter and neutrino experiments via phonon pulse shape
discrimination technique [20, 21].

###  2.2 Direct Application of Neutrinos to Nuclear Security and Nuclear
Energy

There is an active community primarily comprised of neutrino physicists and
nuclear engineers that seeks to explore direct use of reactor neutrino
detection in nuclear security and nuclear energy. The regular Applied
Antineutrino Physics (AAP) Workshop series [22, 23, 24, 25, 26], held since
2003, has been a forum for discussion of capability demonstrations, technical
developments, use case studies, and occasional interaction with experts from
the nonproliferation community.

A comprehensive review of use of neutrinos for nuclear security applications
can be found in Ref. [27]. Interest in such applications derives from the fact
that electron antineutrinos are an inevitable by-product of nuclear fission
via beta decay of fission daughter products or neutron activation of stable
nuclei found in the structure of nuclear energy systems. Neutrinos are a
potentially appealing fission signature since they will be emitted from a
facility effectively unattenuated, which allows non-intrusive monitoring via a
detection system placed some distance away with no direct connection.
Conversely, this same property makes neutrino detection difficult, especially
at larger standoff (baseline) distances which places significant practical
constraints on monitoring capabilities.

Following the treatment of Ref. [27], there are three primary areas where
neutrino-based approaches might provide a technical capability: fissile
material production monitoring, reactor discovery and exclusion, and
monitoring of spent fuel and reprocessing waste. These are described briefly
here in a technical context, while an end-user perspective on the utility of
these approaches is discussed in Section 3.

####  2.2.1 Fissile material production monitoring

Besides the expected proportional variation with power, the total flux and
energy spectrum of neutrinos emitted by a reactor also varies with fuel
composition (see Ref. [27] and references therein). This is because the
fission of different isotopes populates different daughter product
distributions. Neutrino observables like rate, energy spectrum, and the time
evolution of those quantities can therefore provide information on the
consumption and production of fissile material in a reactor. It is important
to note that neutrino measurements represent an average over the reactor core,
whereas conventional nuclear safeguards procedures are largely performed on
discrete items like fuel assemblies. There are many studies that asses the
ability of neutrino measurements to access quantities relevant to monitoring
applications, many of which are summarized in Ref. [27]. These include
examples of verifying expected operations, distinguishing different operating
modes, and sensitivity to changes in reactor fuel composition.

Neutrino physics and application-oriented experiments have demonstrated
relevant detection capabilities, as also summarized in Ref. [27]. These
include “near-field” demonstrations using ton-scale detectors within 10s of
meters of a reactor (e.g. [28, 29, 30, 31, 32, 33, 34, 35]) and “mid-field”
demonstrations using 10 ton scale detectors within 100-1000 m of reactor
complexes (e.g. [36, 37, 38, 39, 40]). Recent demonstrations of near-field
detection without overburden add a potentially important capability that
allows more flexibility in system placement for monitoring applications [33,
34].

####  2.2.2 Reactor discovery and exclusion

The ability to travel long distances without interacting allows the
possibility to detect neutrinos emitted from a reactor at large standoff, with
KamLAND representing a demonstration of this capability [41] . It follows that
a neutrino detector could provide the capability to discover the operation of
an unknown reactor within a surrounding geographical area, or conversely
exclude the presence of a such a facility. Verifying the absence of undeclared
facilities is a component of international safeguards agreements. The primary
challenges for discovery and exclusion concepts are the large required
detector size, the background antineutrino flux from known operating reactors,
and cosmogenic backgrounds that can only be reduced by underground deployment.

The ability to discover the presence of a 50 MWth reactor within a dwell time
of 1 year has been used as a scenario for describing the sensitivity of “far-
field” discovery and exclusion concepts. Estimates presented in Ref. [27]
indicate that under favorable background conditions (no cosmogenic background
and low reactor background typical of the Southern Hemisphere), the presence
of a 50 MWth reactor could be established ($3\sigma$) within 1 year using a
water-based detector with 1,000 kt fiducial mass at a range of 200 km. Under
less favorable background conditions (no cosmogenics, but reactor backgrounds
consistent with Central Europe), that same very large detector would have
similar sensitivity out to 50 km standoff. Recent work studying Gd-doped water
Cherenkov detectors incorporating cosmogenic backgrounds and instrumental
effects indicates that the practical range limit for this approach varies
between $20-35$ km depending on the reactor background conditions [42]. This
is achieved with a detector size of $\approx 50$ kt ($25$ kt fiducial), and
beyond that scale there is little gain in sensitivity, absent further detector
R&D. For context, the area excluded by a 200 km radius is comparable to that
of the U.S. state of Pennsylvania, while that excluded by a 35 km radius is
comparable to the area of Rhode Island.

####  2.2.3 Monitoring of spent fuel and reprocessing waste

The potential use of neutrinos for monitoring and quantification of spent
nuclear fuel (SNF) and reprocessing waste (RW) is described in detail in Refs
[43] and [27]. Both waste forms are highly radioactive and since the bulk of
that activity occurs via beta decay they are neutrino sources. However, there
are only a limited number of fission daughter products that generate neutrinos
above the inverse beta decay threshold with an associated half-life relevant
to long term SNF and RW monitoring, the most useful of which is the 90Sr/Y
decay chain. Detecting neutrinos from SNF in dry cask storage for use in
inventory verification appears possible, but very technically challenging due
to low signal rates and the need for very good background rejection. Similar
considerations apply to the potential use of neutrinos to quantify the amount
or locations of RW. Large underground detectors at the 100-1000 ton scale
could potentially be used to verify inventory of long-term geological
repositories for SNF.

##  3 Nuclear Security and Nuclear Energy Applications – An End-User
Perspective

###  3.1 The Nu Tools Study

The Nu Tools study [44] was commissioned by the DOE National Nuclear Security
Administration (NNSA) Office of Defence Nuclear Nonproliferation Research and
Development (DNN R&D) to provide a user-derived perspective on the potential
utility of neutrino detection for nuclear security and nuclear energy
applications. Since most earlier studies have focused on characterizing
neutrino signals and detection technologies, one important goal of this
utility-focused study was adding practical context that could help to guide
current and future technology development. The major product of the study is
the Nu Tools Final Report [45], which has been submitted as a contribution to
Snowmass and is summarized here.

The Nu Tools Study was conducted by a 14 person Executive group whose
membership comprised a mixture of nuclear engineers and physicists drawn from
academia and U.S. government laboratories. Input to the study was obtained by
broad engagement with relevant user communities. This was accomplished through
interviews with 41 experts with expertise in Nuclear Security and Safeguards,
Reactor Design and Engineering, and Neutrino Physics and Technology, as well
as a dedicated mini-workshop. Consistent with the focus on utility and end-
user input, interviewees were selected with an emphasis on experts outside the
physics research community, including international and domestic safeguards
practitioners, nuclear reactor vendors and operators, and nuclear policy
experts with experience in government agencies and non-governmental
organizations.

Through synthesis of the engagement outcomes, the Nu Tools study developed a
number of Cross Cutting Findings that apply across all potential capabilities
and use cases. These findings reveal features of end user thought and practice
that will be important to incorporate into technology development efforts if
they are be responsive to user need and move towards real world use. Brief
summaries of the Cross Cutting Findings, adapted from the full text of Ref.
[45], are given here. More detail explaining each finding can be found in that
document.

  * •

End User Engagement. The neutrino technology R&D community is only beginning
to engage attentively with end-users, and further coordinated exchange is
necessary to explore and develop potential use cases.

Some end users see potential in neutrino technologies, but there is not a
compelling use case that justifies their adoption at this time. To date,
potential use cases have mostly been developed in the technical community with
a focus on signals and detection, an approach that has not established
enduring end-user connection or credibility. Systematic and sustained two-way
exchange will be necessary to develop mutual understanding between the
technical and end user communities and identify use cases responsive to user
needs.

  * •

Technical Readiness. The incorporation of new technologies into the nuclear
energy or security toolbox is a methodical process, requiring a novel system
such as a neutrino detector to demonstrate sufficient technical readiness.

The Technical Readiness Level (TRL) required by specific use cases will vary,
but will generally be higher than currently demonstrated neutrino monitoring
systems. Safeguards end-users will generally expect demonstration at TRL 7-8,
i.e. full-scale demonstration in operationally relevant environment.
Demonstrations at this fidelity are important to demonstrate to users that a
technology is sufficiently mature to provide the basis for safeguards
determinations and provide user familiarity. As development of a neutrino
technology proceeds through successively higher TRLs, end-user input should be
an integral part of the process to ensure that it has features and performance
required to meet user needs and implementation constraints.

  * •

Neutrino System Siting. Siting of a neutrino-based system requires a balance
between intrusiveness concerns and technical considerations, where the latter
favor a siting as close as possible.

Non-intrusiveness is viewed as a key advantage of neutrino-based monitoring
approaches. Neutrino-based monitoring can assuage intrusiveness concerns,
since no connection to facility process components is required to access a
neutrino signal. Intrusiveness considerations could lead a cooperatively
monitored party to prefer sites far from the reactor of interest. However, a
very strong impetus to negotiate the closest possible deployment site derives
from implementation constraints related to neutrino detector size, cost, and
construction timeline.

To evaluate the potential of use cases, the Nu Tools Utility Framework was
developed. During the expert engagement process of the study, common themes
emerged that were synthesized into the following four criteria:

  1. 1.

Capability need for specific detection and/or monitoring capabilitiesis
expressed by the end user community. Such capabilities might not be presently
available or they may be less effective than needed. Since cooperative
nonproliferation activities are often conducted under tight resource
constraints the expressed user need for a capability often considers the cost
and effort associated with it. Potentially desirable capabilities may no
longer meet user need beyond a certain cost, while on the other hand some
capabilities may be perceived to have little associated value even at modest
cost.

  2. 2.

Existence of a neutrino signal is evaluated by the neutrino technology
community using well known physics and details of a specific use case.

  3. 3.

Availability of a detector technology is determined by the neutrino technology
community considering whether a neutrino signal can be detected and
backgrounds sufficiently controlled.

  4. 4.

Implementation constraints are expressed by the user community and include
factors like cost, workforce requirements (e.g. number of personnel and
training), measurement timeliness, lead time to deployment, intrusiveness, and
general logistical constraints.

Notably, expertise on capability need and implementation constraints primarily
resides in the nuclear security and nuclear engineering communities. Therefore
engagement with these communities formed the basis for use case evaluation in
the Nu Tools study. As described in the Cross-Cutting Findings, continued
engagement of this type will continue to be important for advancing neutrino
technologies from the laboratory to real world use.

###  3.2 Use Cases with Potential User Interest

Applying the Utility Framework, the following use cases were found to have
potential. All require further engagement, study, and definition, but can
already provide important guidance to neutrino technology efforts. Brief
summaries adapted from the full text of Ref. [45] are given here. More detail
explaining each finding can be found in that document.

####  3.2.1 Advanced Reactor Safeguards

Advanced reactors present novel safeguards challenges which represent possible
use cases for neutrino monitoring.

In contrast to safeguards for the current reactor fleet (described below), the
Nu Tools engagement phase found a need being expressed for new safeguards
methods being needed for some advanced reactor systems. In particular,
advanced reactor concepts where the concept of item accountancy no longer
applies were identified as an area where neutrino detection could provide a
useful capability. There are many advanced reactor types under development,
and the potential for a neutrino detector system to be developed largely
independently since no physical connection to a facility is required may also
be an attractive feature. Further detailed study is needed to understand
parameters of interest and how well neutrino detection can address these.
Similar to other findings, end user implementation constraints like system
cost remain a concern.

####  3.2.2 Future Nuclear Deals

There is interest in the policy community in neutrino detection as a possible
element of future nuclear deals.

During the Nu Tools engagement phase, some experts expressed the view that
neutrino detection warrants further consideration in the context of new
treaties and agreements, with a greater likelihood of relevance for those
involving a small number of countries. Reasons for this potential interest are
that verification of new agreements may require novel capabilities and that a
new treaty involving relatively few parties may have fewer constraints on
verification approaches and be more open to negotiation compared to large
established treaties. Also, agreements with relatively limited scope and a
foundation in mutual confidence building are more amenable to the introduction
of novel verification technologies. The possibility of combining verification
functions with scientific cooperation between participating nations was
highlighted as an attractive possibility by some experts.

Implementation constraints related to cost and technical readiness are also a
concern in the context of future nuclear deals. As discussed above,
considerations including cost favor siting as close as reasonably achievable
to an individual reactor facility of interest, consistent with any
intrusiveness concerns being addressed.

####  3.2.3 Spent Nuclear Fuel

Non-destructive assay of dry casks is a capability need which could
potentially be met by neutrino technology, whereas long-term geological
repositories are unlikely to present a use case.

The growing inventory of spent nuclear fuel in dry cask storage is primarily
maintained under safeguards through a continuity of knowledge approach based
on seals and video surveillance. The Nu Tools engagement phase found that non-
destructive assay of dry cask contents is a presently unmet capability need,
and neutrino signatures potentially contain sufficient information for this
task. However, the weak neutrino emissions of spent fuel (relative to
operating reactors) present a very significant detection challenge.

The more permanent approach of spent nuclear fuel storage in geological
repositories is still under development, as are approaches for safeguarding
such facilities. In principle, neutrino detectors could supplement planned
Containment and Surveillance methods. However, implementation challenges
deriving from the low neutrino emissions and consequent requirement for large
detectors likely outweigh the possible monitoring value.

####  3.2.4 Post-Accident Response

Determining the status of core assemblies and spent fuel is a capability need
for post-accident response, but the applicability of neutrino detectors to
these applications requires further study.

The response to the nuclear power accidents at Three Mile Island, Chernobyl,
and Fukushima Daiichi was hampered by a lack of knowledge regarding the
configuration and criticality status of the reactor fuel. The Nu Tools
engagement process found that a capability need exists for instruments able to
provide information of this type. In principle, neutrino detection could
provide information on the presence of ongoing fission reactions in an
accident scenario. However, little is presently known about fission power
sensitivity requirements and any detector would have to operate in a very
challenging post-accident environment. Further engagement and study will be
required to better understand whether neutrino detection can provide a useful
capability.

###  3.3 Use Cases with Limited User Interest

Applying the Utility Framework, the following use cases, while technically
possible in principle, were found to have limited end user interest. Brief
summaries adapted from the full text of Ref. [45] are given here. More detail
explaining each finding can be found in that document.

####  3.3.1 Current International Atomic Energy Agency (IAEA) Safeguards

For the vast majority of reactors under current IAEA safeguards, the
safeguards community is satisfied with the existing toolset and does not see a
specific role for neutrinos.

The current reactor safeguards approach largely relies on containment,
surveillance, and item accountancy, and the Nu Tools engagement phase
identified no significant capability gaps. These approaches suffice because
the fuel in these reactors comes in the form of discrete, countable units.
Interest from safeguards practitioners in new technologies is guided by
operational ease and time savings without a significant increase in cost,
which are criteria that current neutrino detection technologies do not meet.

Neutrino detectors can provide power and/or fuel burn-up measurements, but
these quantities are rarely measured directly under current safeguards
practice. Where measurements are made it is unclear that neutrino detectors
would provide any benefits over existing tools, particularly given the current
cost comparison. That is, neutrino detectors offer capabilities which are
either a more expensive duplicate of existing capabilities, such as power
measurements at research reactors, or which have no established role and are
not seen as a need in the current IAEA practices, such as in situ burn-up
measurements.

####  3.3.2 Reactor Operations

Utility of neutrino detectors as a component of instrumentation and control
systems at existing reactors would be limited.

Current reactor designs have accumulated many decades of operational
experience and have a mature suite of instrumentation to guide operators, both
in safety-related functions and overall performance monitoring. Neutrino
detection rates imply that the time required to determine a change in reactor
state is long compared to what is needed for safety-critical instrumentation.
Given these circumstances, the Nu Tools engagement phase identified no
potential role for neutrinos as part of the operational infrastructure of
nuclear reactors.

####  3.3.3 Non-Cooperative Reactor Monitoring or Discovery

Implementation constraints related to required detector size, dwell time,
distance, and backgrounds preclude consideration of neutrino detectors for
non-cooperative monitoring.

This finding applies across all detector size scales and operational ranges.
Non-cooperative monitoring using smaller detectors at close-range is
infeasible since the required detector mass and dwell time are not compatible
with a covert operation.

Considering longer standoff distances, large neutrino detectors can in
principle be used to discover an operating clandestine reactor within a radius
of $\sim 100$ km, with the detector size at that range being similar to the
largest under development by the neutrino physics community. An activity with
the explicit goal of “reactor discovery” would be inherently non-cooperative,
occurring from beyond the borders of a country of interest. This is because it
is difficult to conceive of a host nation entering into a cooperative
agreement that presumes the existence of undeclared facilities on its
soil111Note that while the concept of “reactor exclusion” necessarily requires
a reactor discovery capability, this is a goal distinct from discovery that is
compatible with cooperative agreements.. During the Nu Tools engagement phase,
some experts expressed interest in such intelligence-gathering capabilities as
a part of national technical means, e.g. to monitor states that do not grant
access to international inspectors, while others considered this need
fulfilled by existing capabilities like satellites. Similar considerations
apply to the case of non-cooperative cross-border monitoring of a known
facility.

However, general agreement was found that the practical challenges of long-
range non-cooperative reactor monitoring outweigh the potential benefit it
might provide. The major impediment is the required detector size to achieve
sensitivity at long range, which confronts multiple implementation constraints
in the end-user community. These include construction and operation costs,
construction timeline, and the potential political drawbacks resulting from a
country conspicuously monitoring its neighbor. The combination of feasible
range and the requirement for cross-border operation would also limit the
locations such a capability could be applied to.

##  4 Synergies with Particle Physics

Several Whitepapers [46, 47, 48, 49, 50] and Letters of Interest [51, 52, 53,
54, 55, 56, 57, 58] submitted to the Snowmass process describe the mutual
benefits that the neutrino physics and application communities could enjoy
from strong and enduring engagement. In this section, the major topical areas
in which synergies exist are discussed.

###  4.1 Prediction of the Reactor Flux and Spectrum Source Term and Related
Nuclear Data

The topic which probably has the strongest scientific overlap between neutrino
physics and direct neutrino applications is accurate prediction of reactor
neutrino emissions. As discussed in detail in Ref. [46] and the NF09 Neutrinos
from Artificial Sources Topical Group Report, there are persistent
discrepancies between reactor flux and spectrum predictions and measurements.
Resolution of these “reactor anomalies” is a very active multidisciplinary
area of investigation. For example, a Letter of Interest on the topic [52] was
endorsed by 17 collaborations and a number of individuals.

The motivations for this activity are clear. Accurate reactor neutrino flux
and spectrum predictions would have the following benefits:

  * •

Neutrino physics would benefit since the enormous reactor flux could continue
to be a tool for discovery (Sections 4.2, 4.3, & 4.4).

  * •

Neutrino applications would benefit since the ability to monitor and verify
reactor operations and draw safeguards determinations will depend upon having
a reliable and trusted understanding of the flux and spectrum that should be
emitted by a reactor under specified operating conditions.

  * •

All communities would benefit from the improvements in underlying nuclear data
and modelling tools that will be be needed to produce accurate flux and
spectrum predictions.

The steps required to improve our knowledge and ability to predict reactor
flux and spectrum have been the subject of several dedicated meetings and
workshops:

  * •

The Technical Meeting on Nuclear Data for Anti-neutrino Spectra and Their
Applications was hosted by the IAEA Nuclear Data Section in 2019 [59].

  * •

The Workshop on Nuclear Data for Reactor Antineutrino Measurements (WoNDRAM)
was held under the auspices of the Nuclear Data Inter-Agency Working Group
(NDIAWG) in 2021 [60].

The recommendations of these two activities have strong overlap with each
other and Ref. [52], suggesting a high degree of community consensus as to
important steps to take. The highest priority recommendations related to
reactor flux and spectrum of the most recent workshop, WoNDRAM [60] are
summarized here:

  1. 1.

Perform new electron spectra measurements following the neutron-induced
fission of 235,238U and 239,241Pu.

  2. 2.

Perform correlated high-statistics antineutrino measurements at U.S.-based LEU
and HEU reactors with a common high-precision detector; alternatively, perform
an improved high-statistics 235U antineutrino flux and spectrum measurement at
the accessible and high-power ORNL or NIST HEU research reactors.

  3. 3.

Perform an updated sensitivity study of the reactor source term to include
fission yields as a function of reactor neutron spectra, fission product decay
and capture cross sections, contributions from production and decay of minor
actinides and capture on detector materials.

Recommendation (1) would provide modern data with which to perform
“conversion” predictions and provide an additional test of the hypothesis that
the historical integral beta spectrum measurements of 235U suffers from a
normalization error [46]. Recommendation (2) would provide benchmark neutrino
spectra from the major fissile isotopes with strongly correlated systematic
uncertainties for use as a direct reference in scientific and application
studies and for validating other prediction approaches. Recommendation (3)
would improve our understanding of the fidelity of reactor simulation inputs
to neutrino flux and spectrum predictions (e.g. time evolution of fission
daughter inventories) and provide guidance as to which underlying nuclear data
could be improved.

Another notable recommendation that is consistent across the IAEA and WoNDRAM
meetings relates to  establishing standardized evaluations of reactor
antineutrino datasets and predictions in a centralized, publicly accessible
domain [60]. As is the case across all of particle physics, deliberate data
standardization and stewardship is an essential best practice to enable long-
term community access and to facilitate the rapid advancement of the field.
Establishing data standards and an open software framework for flux and
spectrum predictions by all commonly used methods would greatly facilitate
progress by allowing meaningful inter-comparison between results,
straightforward updates based on new data, and reduce barriers to entry for
end-users from the particle physics, nuclear data, and neutrino applications
communities.

Several Snowmass contributions describe efforts that seek to measure reference
neutrino spectra that would fully or partially address WoNDRAM recommendation
(2):

  * •

JUNO-TAO will measure the time-evolving spectrum of a single commercial power
reactor with unprecedented energy resolution [61].

  * •

PROSPECT-II is a proposed upgrade to the PROSPECT experiment [62] based on a
6Li-doped liquid scintillator technology. Built as a relocatable detector, HEU
(near pure 235U) and LEU spectra would be collected from the HFIR research
reactor and a commercial power reactor respectively. Since this upgrade builds
upon successful elements of PROSPECT it can proceed rapidly, with data
collection commencing about 1 year after project start.

  * •

Two efforts are proposing readily mobile detector systems based on segmented
plastic scintillator detector designs that incorporate 6Li (CHANDLER [55] and
ROADSTR [57]). A mobile capability of this type would clearly facilitate
collection of systematics correlated reference spectra.

Aside from the synergistic need for an accurate reactor flux and spectrum
prediction capability, these measurement efforts themselves represent a
synergy between neutrino physics and neutrino applications, as described in
Snowmass LOI contributions from CHANDLER [55], PROSPECT [56] and ROADSTR [57].
These measurements occur in the “near-field” close to reactors and inherently
demonstrate measurement capabilities relevant to applications. The recent
demonstrations of above-ground reactor neutrino detection by PROSPECT [33] and
CHANDLER [34] are especially notable in this regard, since they enable a much
greater range of deployment locations and the concept of a readily mobile
detection system that requires only utility support from a facility. The
CHANDLER [55] and ROADSTR [57] efforts have as an explicit goal development of
application-appropriate readily mobile systems that can operate without
overburden or other infrastructure support.

###  4.2 Physics topics accessible using Near-field Inverse Beta Detectors

Reactor neutrino detection in the near-field has seen overlap between physics
experiments and reactor monitoring demonstrations for several decades. Current
physics topics that motivate continued development of near-field technology
include:

  * •

NF02: Understanding Experimental Neutrino Anomalies: Reactor short-baseline
experiments are well suited to search for electron antineutrino disappearance
consistent with the hints of a $\mathcal{O}(1\,{\rm eV})$ sterile neutrino
[63, 64]. This remains an important topic of research for ongoing detector
projects such as PROSPECT [56] and CHANDLER [55]. In particular, reactor
sterile searches are enhanced by the use of segmented detectors, which is a
specific near-field applications detector design choice that helps to suppress
the surface-level background rates. When paired with a compact research
reactor, detector segmentation creates a range of baselines in a single, fixed
detector module.

  * •

NF09 Neutrinos from Artificial Sources: As discussed in Section 4.1, knowledge
of the reactor flux is critical to both applications and basic science.
Further, there are significant and persistent discrepancies between the
measured reactor flux [65] and theoretical models [66, 67], in both the
absolute rate and spectral shape. Precision direct measurements of the reactor
flux with a range of fuel compositions would inform the theoretical models and
may highlight gaps in the nuclear data. This work is best done with with high
resolution detectors, operating in the near-field, where the effects of three
neutrino mixing are negligible.

The physics case for near-field detectors is discussed in detail in other
reports [46, 64]. Current, planned, and proposed neutrino physics experiments
at relevant baselines with contributions to Snowmass include CHANDLER [55],
PROSPECT [56, 62], and LiquidO [68]. These experimental efforts will continue
to demonstrate important detection capabilities relevant to near-field
applications across a range of target media and detector concepts.

###  4.3 Physics topics accessible using CEvNS and Reactor Neutrinos

While CEvNS detection, with its large cross section, holds promise as a
neutrino detection channel for future applications in reactor monitoring and
nuclear security, in the near term, the R&D needed to accomplish these far
reaching goals has great overlap with the science goals of particle physics
[46, 69]. These topics include:

  * •

NF02: Understanding Experimental Neutrino Anomalies: CEvNS scattering could be
used to perform a direct test of the sterile neutrino oscillation hypothesis
through total neutral current disappearance.

  * •

NF03: Beyond Standard Model Physics: The CEvNS scattering cross section and
detected event rates are potentially sensitive to effects from non-standard
interactions, neutrino magnetic moments and other electromagnetic properties.

  * •

NF04 Neutrinos from Natural Sources: Reactor CEvNS detectors would also be
sensitive to neutrinos from other sources, including supernovae, geoneutrinos
and solar neutrinos.

Current, planned, and proposed CEvNS experiments at reactors are also
discussed in Refs. [46, 69].

###  4.4 Physics topics accessible using Mid & Far-field Inverse Beta Decay
Detectors

The large underground neutrino detectors needed for Mid- and Far-field
neutrino applications are also central to important physics topics of interest
to the community [47, 46]. Chooz[37], Palo Verde [70], KamLAND [41], Daya Bay
[71], Double Chooz [72], and RENO [73] have measured reactor antineutrinos in
the mid- and far-field thereby providing important capability demonstrations
in addition to providing fundamental knowledge of neutrino physics needed to
consider neutrino applications.

The physics topics accessible with detectors at the size scale needed for mid-
and far-field applications are discussed in more detail in the relevant
Neutrino Frontier Topical Group Reports and several cases that use reactor
neutrinos are summarized in Ref. [46]. These topics include:

  * •

NF01 Neutrino Oscillations: The physics of neutrino oscillations in the three-
flavor paradigm, including mixing angles, the mass hierarchy, and CP-
violation.

  * •

NF04 Neutrinos from Natural Sources: Neutrinos from solar, atmospheric,
supernova, and geological sources being used to probe those objects and as a
source for other physics goals.

  * •

NF05 Neutrino Properties: Searching for neutrinoless double beta decay.

Current, planned, and proposed neutrino physics experiments at the relevant
size scale with contributions to Snowmass include Super-K [74] (Gd-doped
water), SNO+ [75] (water and liquid scintillator), Hyper-K [76] (water), JUNO
[77] (liquid scintillator), Theia [49, 78] (water-based liquid scintillator),
and LiquidO [68] (opaque liquid scintillator). In addition to the existing
measurements listed above, these new experiments will continue to demonstrate
important capabilities relevant to mid- and far-field applications across a
range of target media, detector sizes, and standoff (baseline) distances.

The potential DUNE “Module of Opportunity” [79] represents a connection
between experiments of this type and the U.S. long-baseline neutrino program.
Large hydrogen-bearing liquid detectors would have distinct systematic
uncertainties compared to Liquid Argon TPCs for the major long-baseline
accelerator neutrino physics goals of DUNE. Additionally, they would enable
complementary physics goals like some of those mentioned above.

###  4.5 Detector Technology Development Topics with Mutual Benefit to
Particle Physics and Nuclear Security

Since neutrino detection lies at the heart of experimental neutrino physics
and direct neutrino applications, it is natural that there are many synergies
between these two endeavors. As already noted elsewhere, neutrino physics
experiments have often developed neutrino detectors and performed neutrino
measurements that serve as fundamental capability demonstrations for potential
applications. As the field of neutrino applications has developed there are
also opportunities for the converse to be true and for joint development
activities.

Detailed description of the many ongoing detector technology development
efforts is beyond the scope of this report, and can be found in that of the
NF10 Neutrino Detectors Topical Group and associated white papers.
Nonetheless, it is worthwhile to enumerate broad classes of detector
development activities and the associated synergies between neutrino physics
and applications.

Historically, reactor antineutrino detection via Inverse Beta Decay has been
based on scintillators and photo-detectors. Much work continues to expand and
improve reactor antineutrino detection capabilities through development of new
detection media, photon collection and sensing schemes, and detector
geometries. Areas of active development are described in the NF10 Future
Advances in Photon-Based Neutrino Detectors white paper [50], while some
topics specific to reactor antineutrinos are summarized in Refs. [46] and
[47]. Examples with contributions to Snowmass include:

  * •

Detection media: Water-based Liquid Scintillators [49, 80, 50], scintillators
with long-decay constants [50], Gd-doping of water [81], 6Li-doping of organic
scintillators [53, 57, 50], opaque scintillators [68, 50], and additively
manufactured scintillators [82, 50].

  * •

Photon collection and sensing: Large Area Picosecond Photodetectors (LAPPDs)
[50], Multi-wavelength-discriminating sensors such as dichroicons [50],
modular encapsulation of PMTs modules [83], and wavelength shifting optical
collectors [47].

  * •

Physically or virtually segmented geometries for improved event
reconstruction, background rejection, and/or event directionality: CHANDLER
[55], LiquidO [68, 50], NuLAT [84], PROSPECT [62, 50], and SANDD [85].

These technologies can variously improve the detection performance,
affordability, and deployability of photon-based reactor antineutrino
detectors across all size scales. All of these parameters are of great mutual
interest to efforts pursuing neutrino physics and neutrino application goals.
As described in more detail in Sec. 5.3, a suite of projects primarily
supported by NNSA Defense Nuclear Nonproliferation R&D (the proposed Advanced
Instrumentation Testbed (AIT) [58, 81, 80, 83], Eos [50], the BNL 30 ton
Demonstrator [50], and the Mobile Antineutrino Demonstrator), are noteworthy
since they are developing technologies for neutrino applications that have
strong synergies with the needs of neutrino physics experiments.

A newer area of detector development with potential relevance to neutrino
applications is CE$\nu$NS detection. Motivated by potential benefits of a
higher interaction cross section and threshold-free interaction channel,
CE$\nu$NS detection at reactors must overcome challenges related to the
relatively small size of the single scattering energy deposition and
potentially large environmental and instrumental backgrounds at low energies.
Multiple approaches are being actively developed with the synergistic
motivations of neutrino physics and applications. Detailed descriptions can be
found in a dedicated CE$\nu$NS whitepaper [cevns-snowmass] with summaries
relevant to reactor antineutrino detection again given in Ref. [46]. Examples
with contributions to Snowmass include:

  * •

Phonon-based detectors: Cryogenic bolometers (Mi$\nu$er) [86] and Magnetic
Microcalorimeters [21]

  * •

Noble liquid-based detectors: TPCs [87] and bubble chambers [88]

  * •

Other approaches: Meta-stable water [89] and crystal damage measurements via
color center production [48].

PALEOCCENE [48] is noteworthy for having introduced a passive detection
concept that, if proven to be feasible, would be well suited to nuclear
security inspection and verification activities. The ability to hand-carry and
install a detection element with no power supply requirements would be highly
valued by inspectors. That this detection concept also has potential neutrino
and dark matter physics applications is yet another example of the strong
synergies that exist between potential neutrino applications and these areas
of physics that require very sensitive and selective detector technologies.

###  4.6 Workforce Development for the Particle Physics and Nuclear Security
Communities

Training and mentoring a creative and diverse new generation of scientists and
engineers is essential to the long-term success of the High Energy Physics and
nuclear security communities. Projects at the intersection of neutrino physics
and neutrino applications have unique features that provide excellent training
and education opportunities for early career community members while also
adding a wider breadth of experience and opening new career pathways.

For example, relatively small neutrino physics and applications oriented
projects offer young scientists the opportunity to be involved from the idea
and design stage to data taking and analysis [54, 46]. Experiments of order of
5 years duration offer invaluable training opportunities matched to the
research timescale of postdocs (3 years) and graduate students (4-6 years). In
addition, the relatively smaller size of collaborations of these experiments
offer supportive and nurturing environments that are complementary to the
opportunities found in large, international collaborations and reduce the
threshold for early career scientists to get involved in multiple aspects of
the projects.

More broadly, neutrino applications offer a unique opportunity for
collaborative engagement between applications-focused and neutrino science-
focused community members [51, 47, 46]. This will broaden the experience and
expertise of early career community members, e.g. by providing an opportunity
to learn about nuclear security policy and associated technical needs. This
provides an additional non-traditional career pathway for neutrino physicists
in US National Laboratories and industry. Conversely, projects that combine
applications and science could be be a way to introduce people from a broader
set of backgrounds and interest to neutrino physics, helping to further
diversify the field. Investments from the National Nuclear Security Agency
Office of Defence Nuclear Nonproliferation in Academic Consortia [90, 91, 92,
93] are one example of how interaction between these communities can be
facilitated.

###  4.7 Facilities

There are many facilities in the US that are being used for research that
supports neutrino detection technology development and neutrino physics
studies. For CEvNS research the Spallation Neutron Source (SNS), at Oak Ridge
National Laboratory [94] (ORNL) has and will continue to be an important
resource. U.S. research reactors that are being used in detector development,
flux measurements, and/or short baseline oscillation physics include the High
Flux Isotope Reactor (HFIR) at ORNL [56, 94], and the Texas A&M TRIGA reactor
[86]. Research reactors at the National Institute of Standards and Technology
(NIST) and the Idaho National Laboratory also have relevant characteristics
and capabilities in this regard [95]. Many commercial reactors are also being
used for these studies [55, 58, 96].

##  5 Conclusions and Next Steps

From community discussion and submissions to Snowmass it is clear that
technologies and workforce capabilities developed by the field of Neutrino
Physics can have benefits in many other areas of science and society. This
provides an additional motivation for societal investment in the field and
pursue the scientific goals of the community. It is important that community
members have such possibilities in mind and actively seek opportunities to
highlight the broader impact of their research.

To enable continued progress on the development and adoption of neutrino
applications will require coordinated support from government agencies, and
engagement with end-user communities, as has been discussed in the Nu Tools
report [45] and community submissions to Snowmass [51, 46, 47].

###  5.1 Inter-agency Coordination

As was pointed out in Section 4, there is a great deal of overlap between the
objectives of applications and security oriented agencies and and those of
basic science. So, it makes sense that these agencies should coordinate their
funding to support technology development efforts that maximize the benefits
to both science and applications. Beyond that, DOE Office of Science and NSF
funded researchers have valuable expertise on detector technologies and in
calculating sensitivity to measurable quantities that may be relevant for
applications. Their guidance can be a real asset to program managers
considering a role for neutrino detection in applications and security, even
in the absence of an overlapping scientific motivation. The Nu Tools Study,
which was commissioned by the National Nuclear Security Agency (NNSA) to
explore practical roles for neutrinos in nuclear energy and security, is an
excellent example of the neutrino science community providing guidance to a
security agency.

Going forward, we as the neutrino science community need to capitalize on the
success of projects like the Nu Tools study to strengthen the connections
between all federal agencies interested in neutrino technologies and neutrino
science, and encourage greater coordination in the funding of projects that
span the interface of science and applications.

###  5.2 End-user Engagement

One of the cross-cutting finds of the Nu Tools report identified coordinated
and attentive end-user engagement as a critical step in the development of
neutrino applications with real-world relevance. The report goes on to note
the dangers of poorly managed or haphazard engagement with a potential end-
user community. In particular, “neutrino technology developers advocating for
a specific approach without developing a deep understanding of the significant
real-world goals and constraints," has lead to a wariness among some potential
end-users and hindered collaboration with end-users on the exploration of some
use cases.

Going forward, we as the neutrino science community would do well to conduct
our end-user engagement with a coordinated approach, while recognizing that we
do not yet possess a full understanding of the needs and constraints of
potential end users. The Applied Antineutrino Physics (AAP) workshop series
[22] is one venue where this could occur, but opportunities to engage with
end-users in forums more strongly associated with their own communities should
also be pursued.

###  5.3 Current Application-oriented Technology Development Efforts

There are a number of ongoing efforts in application-oriented technology
development with support from U.S. agencies outside the basic sciences. These
are briefly described here to give the neutrino physics community an awareness
of the breadth of such activities and their goals. In a handful of cases,
these efforts also have support from basic science agencies thereby
representing an “existence proof” of the possibility and value of such
coordination.

The NNSA’s Office for Defence Nuclear Nonproliferation R&D (DNN R&D) currently
supports four neutrino detection technology research efforts. Three of these
relate to technology development in support of large detectors for mid- and
far-field concepts and are pursued with some degree of coordination with the
Office of Science HEP Advanced Detector R&D program:

  * •

The Advanced Instrumentation Testbed (AIT) is a proposed underground kiloton-
scale detector testbed for reactor monitoring and technology demonstrations
[58]. Possible target materials of interest for experiments at AIT are Gd-
doped water [81] and water-based liquid scintillator [80].

  * •

The Eos reconstruction and characterization demonstrator [50] is a 3-year
program at LBNL that will test performance parameters of WbLS using a several
ton-scale detector. The primary goal of Eos is to validate performance
predictions for large-scale hybrid neutrino detectors by performing a data-
driven demonstration of low-energy event reconstruction leveraging both
Cherenkov and scintillation light simultaneously.

  * •

The BNL 30 ton Deployment Demonstrator [50] is a 3 year program that will test
large-scale deployment of different WbLS formulas without or with loading of
metallic ions (i.e. Gd). The main goals are to retire risks in support of the
potential deployment and operation of a kiloton-scale WbLS detectors by
establishing the feasibility of and requirements for in-situ WbLS purification
schemes, testing detector cleanliness and material compatibility, and
confirming optical stability and light collection performance.

DNN R&D has recently established the Mobile Antineutrino Demonstrator program.
This 3 year effort was motivated in part by the recent above-ground detection
demonstrations by PROSPECT and CHANDLER, plus near-field use cases with
potential end-user interest identified by the Nu Tools Study. The goal of the
program is to develop and construct a readily mobile ton-scale antineutrino
detector system that requires no infrastructure support beyond electrical
power and space for deployment. Requirements for the system will be defined
with the End-User Engagement and Technical Readiness findings of the Nu Tools
Study in mind, so as to advance near-field systems of this type closer to
real-world adoption. Detection technology options under consideration are the
3D segmented CHANDLER approach [55] and 2D geometries using 6Li-doped PSD
plastic scintillator [50] developed under the ROADSTR program [57].

DNN R&D also co-sponsors a number of nuclear data efforts seeking to improve
reactor flux and spectrum predictions. These were selected and supported under
the Nuclear Data Inter-Agency Working Group (NDIAWG) FOAs.

The Defense Advanced Research Projects Agency (DARPA) supports two efforts
seeking to develop detectors capable of observing CEvNS at reactors. NCC-1701
[96, 46, 69] is based on mechanically cooled High Purity Ge diodes and has
been deployed in a compact shielding package at a commercial reactor. The
NCC-1701 effort also receives support from NSF [96]. NUXE [46, 69] is based
upon a low-threshold liquid xenon TPC.

Upgrades to the MiniCHANDLER [55, 34] prototype are being supported by the NSF
Innovative Industrial Partnership program.

##  6 Acknowledgements

The topical group would like to thank all the community members who
contributed submissions to the Snowmass process and provided feedback on this
report.

This work was performed in part under the auspices of the U.S. Department of
Energy by Lawrence Livermore National Laboratory under Contract DE-
AC52-07NA27344. LLNL-TR-836071

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