# Nonproliferation and fusion power plants

Michael Y. Hua  Department of Radiation Safety and Nuclear Science, Helion
Energy, Everett, WA  Sachin S. Desai  Office of the General Counsel, Helion
Energy, Everett, WA  Amy C. Roma  Global Energy Practice, Hogan Lovells,
Washington, D.C.  Angela Di Fulvio  Department of Nuclear, Plasma &
Radiological Engineering, University of Illinois Urbana-Champaign, Champaign,
IL  Craig J. Mundie  Mundie & Associates, Seattle, WA  Sara A. Pozzi
Department of Nuclear Engineering & Radiological Sciences, University of
Michigan, Ann Arbor, MI

## Abstract

As fusion energy progresses towards commercial deployment, the question has
arisen as to the role of the Treaty on the Non Proliferation of Nuclear
Weapons (NPT) with respect to fusion, including whether the nuclear
nonproliferation regime includes – or should be extended to include – future
fusion plants.

The paper first addresses the current nonproliferation regime and its
application to fusion. This regime, solidified in and based on the NPT, is
designed to ensure that certain types of radioactive material and technology
are used only for peaceful purposes and not nuclear weapons purposes.
Specifically, the NPT expressly controls the transfer of source material
(i.e., unenriched uranium and thorium); special fissionable material (i.e.,
enriched uranium (U-235), uranium-233, and plutonium-239); and equipment that
is “especially designed or prepared for processing, use, or production of
special fissionable material.”

As spelled out in the plain language of the NPT and in the NPT’s implementing
documents, the scope of the NPT-based nonproliferation regime – with its focus
on safeguards – is limited to fission-related technology, including fission
reactors and the fission nuclear fuel cycle technologies (e.g., enrichment and
conversion facilities). As fusion does not use source or special fissionable
material or the fission nuclear fuel cycle, commercial fusion applications
prima facie fall outside the current NPT nonproliferation regime and
implementing documents.

This paper then addresses options to consider for fusion, including whether
fusion power plants should be included within the NPT and associated
safeguards framework, or whether other frameworks – particularly the existing
global, dual-use export control framework – are more appropriate to control
the technology. Including fusion power plants within the NPT would requirement
amendment of the treaty, which is largely a geopolitical issue and attaining
the required global consensus is likely not feasible. In any event, a
technical analysis of fusion is considered.

Based on a technical analysis explained herein, and as applied to the existing
legal framework, this paper concludes that commercial fusion facilities should
continue to fall outside the NPT. Including fusion and applying safeguards is
not warranted considering that the nonproliferation risks associated with
traditional nuclear fission just do not exist for fusion and would be beyond
the “extent necessary to ensure its use only for peaceful purposes.” Rather,
this paper concludes that fusion facilities as they are “especially designed
or prepared” have very limited significance to the development of special
fissionable material for weapons purposes or nuclear weapons themselves. Any
potential, malicious misuse of the fusion technology from a nonproliferation
perspective would require significant material changes to the underlying
technology and apparatus. Additionally, adding fusion to the NPT would not
provide a gain commensurate with the incredible work required to amend the NPT
and the associated implementing documents.

In the alternative, this paper concludes that the current dual-use export
control regime is an appropriate path to look to for fusion, in large part
because any potentially significant malicious misuse of the fusion technology
from a nonproliferation perspective would require significant material changes
to the underlying technology by rogue actors. Applying and modifying a dual-
use export controls approach as necessary alongside the NPT –- including
potentially developing a “controls by design” usage-based controls regime for
fusion – can more effectively support the safe deployment of this essential
technology rather than applying the ill-fit, fission-specific nonproliferation
regime.

##  1 Introduction

Research and development for fusion power plants has accelerated in recent
years, and there has been a significant increase in private funding. This
progress has been made possible by significant advancements in enabling
technologies like modeling, power electronics, and magnet technology. Multiple
companies are seeking to demonstrate net energy (and in at least one case,
even net electricity) from fusion within the next few years, with first power
plants to follow [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13].

As fusion energy progresses towards near-term commercial deployment, the
question arises as to the role of the Treaty on the Non Proliferation of
Nuclear Weapons (NPT) with respect to fusion, and whether (i) the nuclear
nonproliferation regime includes, or (ii) should be extended to include,
future fusion plants. Note that there exist some fusion-fission hybrid
technologies, but these are out of the scope of this paper and not considered
fusion power plants as they are still dependent on fission. In any event,
their fission applications would be subject to the existing NPT framework.

This paper analyses those two questions under the outline as follows.

  * •

Section 2 addresses the current application of the NPT and global
nonproliferation regime to fusion. To that end, it explains the historical and
legal landscape for the global nonproliferation regime and analyzes the NPT’s
scope, IAEA safeguards agreements and supporting instruments, and the broader
export control framework that sits alongside the NPT.

    * –

Section 2.1 provides historical background information from World War II
leading to the NPT

    * –

Section 2.2 provides an overview of the NPT

    * –

Section 2.3 explains role of the IAEA, safeguards agreements and supporting
instruments

    * –

Section 2.4 provides an overview of the export control framework

    * –

Section 2.5 applies fusion to the NPT, IAEA and safeguards agreements, and the
export control framework

  * •

Section 3 evaluates, given the understanding that the global nonproliferation
regime as is does not apply to fusion, whether it should be amended to apply
to fusion or if another approach (such as turning to export controls) would be
more appropriate. To that end, this section evaluates the different
theoretical risks that have been identified related to fusion, their
connection to nuclear proliferation, and what are the best tools to address
those risks. These theoretical risks include:

    * –

Section 3.1: use of fusion devices as a neutron source to create fissile
material,

    * –

Section 3.2: leveraging research into ignited, inertially confined plasmas
towards nuclear weapons development, and

    * –

Section 3.3: diversion of tritium from fusion facilities to boost nuclear
weapons.

The analysis in Section 3 demonstrates that these theoretical concerns do not
raise a material practical risk of nuclear weapons proliferation, and thus do
not warrant extending a fission-focused nonproliferation regime (including
safeguards) to fusion. Instead, an approach focused on export controls appears
more appropriate. Note that diversion of tritium from fusion facilities
towards a radiological dispersion device (RDD or “dirty bomb”) is ancillary to
this discussion and addressed in Appendix A.

  * •

Section 4 concludes this paper.

##  2 Background: historical and legal landscape

###  2.1 Historical context

The dawn of the nuclear age at the end of the World War II introduced to the
world two things: nuclear weapons, and soon thereafter nuclear power for
peaceful use. When the United Nations was formed, shortly after the US
deployed two nuclear weapons in Japan, its first order of business was to
address the issues of preventing the spread of nuclear weapons while ensuring
the peaceful use of nuclear technology. The first UN resolution was to
establish a commission to handle atomic energy [14], and set forth the general
global consensus that nations (i) share scientific findings related to atomic
energy, (ii) eliminate weapon of mass destruction arsenals, (iii) use
safeguards to protect compliant states from the hazards of noncompliance, and
(iv) have “control of atomic energy to the extent necessary to ensure its use
only for peaceful purposes” [14].

In the subsequent couple decades post-World War II, particularly the 1950s and
1960s, the world saw a number of developments on both the nuclear weapons and
peaceful use front. On the weapons side, a number of countries, in addition to
the US, successfully tested nuclear weapons, including the then-USSR, the
United Kingdom, France, and China [15]. The first thermonuclear weapon, a
second-generation nuclear weapon that uses a combination fission and fusion
system, was tested in the early 1950s, and soon thereafter widely under
development by nuclear weapons states. Notably, however, these weapons
intrinsically rely on a fission process [16, 17, 18].

On the peaceful-use side, the first electricity production from a fission
reactor occurred in 1951. In 1953 President Dwight Eisenhower delivered his
“Atoms for Peace” speech to the United States, under which the US agreed to
share nuclear technology with the rest of the world, in exchange for the rest
of the world foregoing the development of nuclear weapons. In 1957, the first
reactor to connect with the grid became operational. Soon therefore, civilian
nuclear technology spread around the world, and dozens of countries have
hundreds of nuclear reactors for peaceful uses, including power generation,
medical use, and research and development [19].

Fusion research and development was around at this time as well. By the World
War II timeframe, just before the middle of the 20th century, the theoretical
framework for fusion had been established, and fundamental science was still
being explored. Fusion applications were being explored broadly in the US,
Russia, and UK, while Japan, France, and Sweden were looking at developing
fusion power plants. Whereas fission is the splitting of large nuclei
($\approx$240 atomic mass units), fusion is the combining of small nuclei
($\approx$2 atomic mass units). The domains of these reactions are on opposite
ends of the periodic table: the uranium of fission is the last stable element,
whereas the hydrogen of fusion is the first. Fission assemblies support self-
sustaining chain reactions to produce energy, whereas fusion power plants do
not use chain reactions to generate energy.

Given these developments, the global community needed to develop a global
framework to prevent the spread of nuclear weapons, while enabling peaceful
uses – which the world wanted. This is the foundation of the NPT, the
cornerstone of the global nonproliferation regime [20].

In 1952, the General Assembly created what is now known as United Nations
Disarmament Commission (UNDC) under the Security Council with a mandate to
prepare proposals for a treaty for the regulation, limitation, and balanced
reduction of, among other things, nuclear weapons [21]. While only meeting
occasionally in its early years, an earlier version of the UNDC, the Eighteen-
Nation Disarmament Committee (ENDC), was formed in 1962. The ENDC was a
committee that would ultimately negotiate the NPT111The UNDC undertook a few
evolutions, with earlier versions including the ENCD, until it ultimately
settled in its current form, the UNDC, in 1968. The UN General Assembly
accepted the decision of the major powers to create the Eighteen Nation
Committee on Disarmament (ENCD) through resolution 1722 (XVI) on December 21,
1961. [22].

The ENCD, was made up of 18 nations: Canada, France (in a non-official
capacity), United Kingdom, Italy, United States, Bulgaria, Czechoslovakia,
Poland, Romania, Soviet Union, Brazil, Burma, Ethiopia, India, Mexico,
Nigeria, Sweden, and the United Arab Republic (UAR). The ENCD began work in
1962 and, before it was reconstituted in 1979 as the UNDC, met over 430 times
[22].

The result of those meetings was the NPT, which opened for signature in 1968,
and entered into force in 1970. A total of 191 States have joined the Treaty,
including the five nuclear-weapon states recognized by the NPT. More countries
have ratified the NPT than any other arms limitation and disarmament
agreement, underscoring its global significance.

###  2.2 Scope of the NPT

The concept of nuclear nonproliferation is intrinsically tied to the NPT and
refers to a specific risk to global security –- the risk of creating nuclear
warheads. The three pillars of the NPT are to (1) prevent the spread of
nuclear weapons and weapons technology, (2) promote cooperation in the
peaceful uses of nuclear energy, and (3) further the goal of achieving nuclear
disarmament and general and complete disarmament. [20].

Under the NPT, parties that are non-nuclear-weapon states have committed to
not manufacture or otherwise acquire nuclear weapons or other nuclear
explosive devices, while parties that are nuclear-weapon states have committed
not to in any way assist, encourage, or induce any non-nuclear-weapon state
party to manufacture or otherwise acquire nuclear weapons or other nuclear
explosive devices. A “nuclear-weapon state” party under the NPT means a state
that manufactured and exploded a nuclear weapon or other nuclear explosive
device before 01 January 1967. The NPT further requires non-nuclear-weapon
state parties to enter into safeguards agreements with the IAEA, to verify
compliance under the NPT (as discussed in more detail in Section 2.3) [20].

With respect to the restrictions applicable to sharing nuclear material,
equipment, or underlying technology, the NPT is carefully drafted to establish
controls over only “(a) source or special fissionable material, or (b)
equipment or material especially designed or prepared for the processing, use
or production of special fissionable material” [20]. The choice of NPT scope
was carefully negotiated such that, considering both nuclear weapons and
peaceful uses of nuclear technology, controls should be only implemented to
“the extent necessary” to ensure peaceful use.

Source or special fissionable material are specific terms well understood
around the world. Source material means unenriched uranium or thorium, and
special fissionable material means material enriched in uranium (U-235),
uranium-233, and plutonium-239 [23]. Uranium, thorium, and plutonium are the
large-atomic-mass elements that can themselves undergo (or be bred/configured
to undergo) self-sustaining chain reactions: the fissioning of one nucleus
leading to fissioning of multiple other nuclei. These rapidly growing fission
chain reactions are the foundation for all nuclear weapons.

The phrase “equipment especially designed or prepared for the processing, use
or production of special fissionable material” is also well-established and
specific. It refers to (i) equipment “especially designed or prepared for”
creating or isolating special fissile materials, that is, the so-called
nuclear fuel cycle, such as nuclear enrichment facilities (which can isolate
fissile uranium-235); and (ii) nuclear fission reactors (which inherently
process and use special fissionable material, and also create fissile
plutonium or uranium-233 from uranium or thorium, even under normal
operation).

The phrase “especially designed or prepared for” plays an important role in
clarifying the scope of equipment and technology brought under the
nonproliferation regime. Everything from fiber optics to steel to screws can
play a role in the construction of a nuclear weapon. But under the NPT, only
that equipment “especially designed or prepared for” playing a role in the
direct nuclear fuel cycle is included, allowing the global nonproliferation
framework, and the implementing network of domestic law and regulations that
implement it, to focus on those elements of key concern.

The long-standing list of key equipment determined to be “especially designed
or prepared for” the production or use of special fissionable material, and
thus captured within the nuclear nonproliferation regime, is found in the
“Trigger List” established by the Zangger Committee (also known as the “NPT
Exporters Committee”), a 39-member coalition that is a key interpreter for
what constitutes “especially designed or prepared material” under Article
III.2 of the NPT [20, 24]. This list includes nuclear reactors, fissile fuel
fabrication facilities, reprocessing plants, enrichment facilities, heavy
water facilities, conversion facilities, and key components and materials
[24]. Each of these supports a nuclear end use – an end use related to
processing, using, or producing special fissionable material as required by
the NPT. A very similar Trigger List was also established by the Nuclear
Suppliers Group (NSG) to also reflect those components “especially designed or
prepared for” nuclear end use, and which should directly be subject to
safeguards under the NPT.222A key example of this distinction lies around the
nuclear nonproliferation regime’s treatment of deuterium. The Trigger List
extends to deuterium specifically for nuclear end use (as heavy water -– water
enriched in deuterium -– can be used to breed special fissionable material).
However, deuterium not destined for a nuclear reactor falls outside of the
Trigger Lists and the NPT. “The guiding question for listing items on the
Trigger List is ‘do the items meet the EDP [especially designed or prepared]
criteria for the processing, use, or production of special fissionable
material?’”

The Trigger Lists play a very important role in interpreting the scope of
facilities covered under the NPT. Critically, they explicitly exclude fusion
from the scope of these lists. Both state in their note under nuclear
reactors, for example, “this entry does not control fusion reactors.” Both
Trigger Lists also exclude tritium and tritium production technologies
(although they feature on a separate list focused on dual-use333Dual-use
technologies are those technologies that are designed or suitable for both
civilian and military, terrorism, or weapons of mass destruction-related
applications. export controls).

Even as the global nuclear nonproliferation regime has aged, it has remained
steadfastly focused on the production chain and fuel cycle for fissile nuclear
materials, including as implemented by the IAEA through its safeguards
program.

###  2.3 IAEA safeguards

The signature feature of the NPT-based nonproliferation regime is safeguards.
In practice, safeguards is monitoring and accounting of source and special
fissionable material – taking the form for example of IAEA inspectors
routinely using detectors to measure the amount of (fissionable) nuclear
material at various declared sites around the world and affirming that the
measured quantity matches the declared amount [25, 26, 27, 28]. The
International Atomic Energy Agency (IAEA), a global United Nations body based
in Vienna, Austria, is entrusted with the key verification responsibilities
under the NPT.

Under the NPT, Article III, each non-nuclear-weapon state party is required to
conclude a comprehensive safeguards agreement (CSA) with the IAEA to enable
the IAEA to verify the fulfillment of their obligation under the NPT, with the
goal of preventing diversion of nuclear material from peaceful uses to nuclear
weapons or other nuclear explosive devices. Under a CSA, the IAEA ensures that
safeguards are applied on nuclear material in the territory, jurisdiction or
control of the state for the purpose of verifying that such material is not
diverted to nuclear weapons or other nuclear explosive devices. As of
September 2021, 178 non-nuclear-weapon state parties to the NPT have brought
into force CSAs required by the NPT [20, 29, 30].

In addition to a CSA, there are three other types of safeguards agreements.
The five nuclear-weapon states party to the NPT have voluntarily entered into
safeguards agreements under which the IAEA applies safeguards to nuclear
material in facilities that the state has voluntarily offered and the IAEA has
selected for the application of safeguards. Safeguards are also implemented in
three countries that are not party to the NPT – India, Pakistan, and Israel –
on the basis of item-specific agreements they have concluded with the IAEA to
ensure safeguarded facilities and materials are not used for nuclear weapons
proliferation [30, 31, 32, 33, 34, 35, 36]. Additionally, the Small Quantities
Protocol (SQP) is a protocol available to states with limited nuclear material
and holds in abeyance many procedures in Part II of a CSA. The purpose of an
SQP is to reduce safeguards implementation burdens in states with limited
nuclear activities, while retaining the integrity of the broader safeguards
system [37]. Safeguards generally apply to facilities and activities covered
by the Zannger Committee and NSG Trigger Lists (see Annex II of the Model
Additional Protocol) [24, 38]

In 1997, the Model Additional Protocol [38, 39] was created to enhance IAEA
inspection capabilities following the discovery of clandestine weapons
programs in the 1990s. The Model Additional Protocol extended the scope of the
NPT regime to undeclared “nuclear fuel cycle activities” including nuclear
fission reactors, as well as broadened the ability of the IAEA to conduct
environmental inspections of non-nuclear sites upon IAEA request. However, it
still maintains a focus on only applying safeguards to those activities
specifically related to the production or possession of special fissionable
material, tied to the Trigger Lists discussed above. For example, although
tritium (hydrogen-3) by this time was commonplace in nuclear weapons as a
booster, the Additional Protocol intentionally did not extend safeguards
requirements to tritium. Moreover, it maintained the definition of “nuclear
reactor” to those devices “capable of operation so as to maintain a controlled
self-sustaining fission chain reaction,” excluding fusion.444The long-standing
clarifications in the Model Additional Protocol and Trigger Lists as to the
definition of nuclear reactor gives significant weight to a conclusion that
the definition of “nuclear reactor” in the IAEA statute also excludes fusion
devices (e.g., as used in Article XII, concerning safeguards). This long-
standing focus on source and special fissionable materials and fission
process, even in updates to the global regime, reflects the NPT’s intent to
control the use of atomic energy specifically “to the extent necessary” to
ensure its peaceful use.

###  2.4 Export control framework

International trade is subject to a network of export controls to protect each
country’s national security interests, promote foreign policy objectives, and
leverage economic interests and opportunities. There is a robust framework of
export control regimes to prevent the proliferation of weapons of mass
destruction and prevent destabilizing accumulations of conventional weapons
and related material. Some of this framework is derived from international
nonproliferation obligations under the NPT, while other elements of this
framework (particularly the dual-use export controls framework) more broadly
police other international and domestic obligations and agendas.

####  2.4.1 Nuclear-specific export controls implementing the NPT

For example, after IAEA safeguards, countries implement their NPT treaty
obligations into their domestic law. For example, in implementing the NPT in
the US, Congress among other things passed the Nuclear Non-Proliferation Act
of 1978 [40] and Atomic Energy Act of 1954 [41], which gave the US Nuclear
Regulatory Commission and US Department of Energy stronger authority to
regulate exports of source and special nuclear material (the US analog of
“special fissionable material”) and those technologies “especially designed or
prepared for” producing or using special nuclear materials – i.e., those items
and technologies falling under the NPT. See Refs. [42] and [43] explaining how
the Nuclear Non-Proliferation Act gave the NRC jurisdiction over exports of
“nuclear facility components and other nuclear items and substances having
possible significance for nuclear explosive uses” in 10 CFR Part 110 [44], and
Ref. [45] explaining how the Atomic Energy Act and Nuclear Non-Proliferation
Act give the Department of Energy jurisdiction over exports of nuclear
technology that poses a nuclear proliferation hazard because it can produce
special nuclear material in 10 CFR Part 810 [46]. These are generally seen as
strict export controls, and for example typically require license or
notification for any export, regardless of destination or use. The
technologies and materials captured under these nuclear-specific export
controls tie to the Trigger List, and a general requirement for export
licensing is that the destination applies safeguards to this regime, including
appropriate reporting to the IAEA under the Additional Protocol.

####  2.4.2 Dual-use export controls

Beyond nuclear-specific export controls that directly implement the NPT, a
broader level of export controls exists across multiple countries that police
exports of technology, material, or ancillary equipment including when they
have a dual use, which could tangentially relate to nuclear end use and
proliferation. Specifically, “dual use” refers to items that have both
commercial and some military or proliferation applications, but are not
“especially designed or prepared” for nuclear end use.555As explained by the
IAEA, in the nuclear context “dual use items are items that can be used either
for a nuclear or for another purpose, or for a variety of non-nuclear
purposes, and hence do not fall within the scope of Article III.2 of the NPT
which relates only to ‘equipment or material especially designed or prepared
for the processing, use or production of special fissionable material’
[emphasis added].”

This division between application of NPT safeguards and nuclear-specific
export controls on source and special fissionable material and the nuclear
fuel cycle (captured in the Trigger Lists), and export controls for dual-use
technology that may have a nuclear misuse concern, is not simply happenstance
but is well understood. The concept of applying dual-use export controls to
non-NPT dual-use technologies and materials appeared early on, with the NSG
issuance of additional guidance separate and beyond the Trigger List on dual-
use exports (the NSG Part 2 Guidelines) in INFCIRC/254 in 1992. Despite
formally recognizing in the early 1990s that there are technologies that if
misused could have an impact on proliferation, the Additional Protocol was not
expanded to capture those technologies under safeguards. The IAEA instead
appeared content on letting such technology be managed by export controls. One
of the key goals of the dual-use export control regime is thus to ensure that
there is not diversion of the technology to nuclear weapon applications.
Although discussed more below, fusion related technologies such as tritium
development systems are already captured under this regime.

In the US, these broader export controls are found in the Department of
Commerce’s Export Administration Regulations, EAR, found at 15 CFR Part
730-744 [47]. These regulations (save certain limited export reporting
obligations) largely find their authority not in the NPT, but in domestic
laws, such as in the US the Export Administration Act of 1979 [48] (as updated
by the Export Control Reform Act of 2018 [49]).

The Department of Commerce dual-use export controls (15 CFR Parts 730-744) sit
outside the purview of the NPT and what is commonly understood as the nuclear
nonproliferation regime (although there is some coordination [42]), and cover
beyond what is “to the extent necessary” for the NPT to cover under
safeguards. For example, while the NRC and US Department of Energy (DOE)
regulate the export of nuclear fission reactors under 10 CFR 110 and 810 (as
they process and produce special nuclear material), the Department of Commerce
regulates the exports of equipment apart from the central nuclear island at a
nuclear fission plant (e.g., ECCN 2A2901 and 2A291 [50]), such as radiation
monitors, simulators, and backup diesel generators. Such items or “balance of
plant” components are those that help a nuclear power plant run but are not
themselves part of the nuclear fuel cycle.

Said another way, the nuclear-specific export controls by the NRC and DOE
exist when the item being exported has direct significance to nuclear
proliferation (like the nuclear fuel cycle), while the Department of Commerce
regime covers those exports of technologies that themselves have limited risk,
but if abused or misused could create a proliferation concern. This
distinction between the role of the NRC and DOE as to policing core
proliferation concerns, versus the Department of Commerce as a backstop dual
use regulator, is seen most clearly in a recent action by the NRC to clarify
that the NRC export control regulations did not apply to deuterium exported
for non-nuclear end uses. This decision was made on the grounds “that
deuterium for non-nuclear end use is not an item or substance that is
‘especially relevant from the standpoint of [the Nuclear Non-Proliferation
Act] export control because of [its] significance for nuclear explosive
purposes’” and therefore better suited for control by the US Department of
Commerce [51].

The Department of Commerce export regime explicitly balances economic and
national security interests (see Section 2 of the Export Administration Act of
1979 [48]). Thus, dual-use export controls may touch on a number of ancillary
technologies that may – if misused – have an impact on proliferation, but have
a much more proportionate hand. For example, exports of nuclear balance of
plant components only as a general rule need a license when exported to a
specific set of countries, with some exceptions (See the Commerce Country
Chart, Ref. [52]). Tighter controls can exist for certain equipment or
materials, but licensing can often be prompt, and there is more regulatory
flexibility. That being said, the regime is still quite strict. As described
in the NSG Guidelines, countries should not permit exports of dual use items:

  * •

for use in a non-nuclear-weapon state in a nuclear explosive activity or an
unsafeguarded nuclear fuel-cycle activity,

  * •

in general, when there is an unacceptable risk of diversion to such an
activity, or when the transfers are contrary to the objective of averting the
proliferation of nuclear weapons, or

  * •

when there is an unacceptable risk of diversion to acts of nuclear terrorism.

####  2.4.3 Summary of the export control framework

A schematic of the agencies, tools (i.e., safeguards and export controls),
focus of the tools, and connection to treaties and acts discussed in this
section is shown in Figure 1.

Figure 1: Simplified overview schematic of the security and control agencies,
tools, focus of the tools, and sources of legal authority specific to the US
as discussed in the legal background section. The portion above the dashed
line focuses on special fissionable material, fuel cycle and nuclear fission
reactors, whereas the portion below the line is “non-nuclear”.

###  2.5 Applying fusion to the NPT, IAEA safeguards, and export control
framework

On its face, fusion does not fall under the NPT. As noted, the plain language
of the NPT is expressly limited in scope to source or special fissionable
material, or such related “equipment” that is “especially designed or prepared
for processing, use or production of special fissionable material.” The NPT
regulates source material because it can be enriched into special fissionable
material; it regulates special fissionable material because it is or can be
enriched into material for use in nuclear weapons; and it regulates certain
specific underlying equipment because such equipment “is especially designed
or prepared” to make, use, or further refine special fissionable material. NPT
implementing documents, set forth in IAEA safeguards agreements and protocols
to the agreement are likewise limited to this same type of equipment and
material. For example, fusion is not included in the safeguards agreements,
Additional Protocol, or the Trigger List.

A review of the history of the NPT also confirms that not including fusion
appears to be intentional. To this point, the US Permanent Representative to
the United Nations said on 15 May 1968 regarding the NPT that “controlled
thermonuclear fusion technology will not be affected by the treaty” [53, 54],
an intent that was recognized and mirrored by the depository notes provided by
other nations. For example, Germany again quotes that its interpretation of
the NPT was that “controlled thermonuclear fusion technology will not be
affected by the Treaty,” [55, 56] and Japan considered that “thermonuclear
fusion reactors should not come under the prohibitions of the NPT” [57].

Current US treatment of fusion technologies echoes this categorization of
fusion outside of the NPT. The US implementation of the NPT takes the form of
safeguards that applies to nuclear reactors and nuclear materials (see, for
example, the NRC’s regulations in 10 CFR Part 74 that set forth materials
control and accounting requirements for special nuclear material, those in 10
CFR Part 73 that set forth physical security requirements [58, 59], and those
in 10 CFR Part 75 that apply additional IAEA safeguards requirements, none of
which apply to fusion).

Even if outside the NPT, under international trade laws, the existing export
control framework still applies to fusion. And this is one familiar with
fusion, especially with the development of the ITER fusion facility, which is
a 35-country fusion research and development project in Southern France. Not
only is the equipment and underlying technology exporting to France, but each
ITER collaborator is entitled to access each other’s technologies and export
controls come into play.

##  3 Evaluation of fusion against proliferation risks

Given that fusion currently falls outside of the NPT regime and safeguards,
two options exist for evaluation. First is the active addition of fusion into
the NPT regime. Given the long-standing exclusion, this would require at a
minimum modification of various international agreements if not the NPT
itself. An alternative is to turn to the dual-use export control regime that
currently polices misuse of technologies that could, if misused, produce
special fissionable material or support weapons production. Adopting fusion
into this regime (which in large part has already occurred), would require
less fundamental change to the overall nonproliferation framework.

The technical case plays a key role in choosing between these options. In
order to evaluate these options, this section evaluates the theoretical
nonproliferation risks that have been identified related to fusion: use of
neutrons to create fissile material (see Section 3.1), leveraging research of
ignited, inertially confined plasmas for thermonuclear weapon development (see
Section 3.2), and diversion of tritium to boost nuclear weapons (see Section
3.3). Note that the ancillary risk of diversion of material towards a
radiological dispersion device is separately addressed (see Appendix A). The
risks are evaluated in light of whether they create an inherent and immediate
special fissionable material proliferation risk that warrants safeguards, or a
more indirect risk of abuse that is appropriately addressed via dual use
export controls. Figure 2 summarizes these risks and the corresponding,
existing mitigation measures discussed in this section.

Figure 2: Overview of the potential proliferation risks associated with fusion
power plants and the already existing tools that can be used to mitigate the
risks.

###  3.1 Use of neutrons to breed special fissionable material

Fusion power plants can produce substantial neutron fluxes, and these neutrons
can theoretically be used to breed significant quantities of special
fissionable material (e.g., plutonium, enriched uranium, and U-233) from
source material (e.g., depleted/natural uranium and thorium). The IAEA has
defined significant quantities as “the approximate amount of nuclear material
for which the possibility of manufacturing a nuclear explosive device cannot
be excluded” [23]. The significant quantity for plutonium (containing less
than 80% Pu-238) or U-233 is 8 kg, and for highly enriched uranium (greater
than 20% U-235) it is 25 kg. Significant quantities are also defined for
indirect use nuclear material and are 20 ton for thorium, 10 ton for natural
uranium, 20 ton for depleted uranium, and 75 kg of uranium-235 in any uranium
that is less than 20% U-235 [23].

Prior works have investigated fission-fusion hybrid systems designed to breed
fuel for fission reactors from fusion neutrons [60]. Although fission-fusion
hybrids are beyond the scope of this paper (and already receive distinct
treatment because of the inherent fission from the outset), the idea that
fusion power plants could be abused to breed special fissionable material is
considered. Prior works have investigated this misuse, notably Refs. [61, 62],
and their work is summarized and further discussed in this section. Three
scenarios are analyzed, which are considered comprehensive:

  1. A.

Clandestine production of special fissionable material (action at an unknown
facility),

  2. B.

Covert production of special fissionable material (unknown action at a known
facility), and

  3. C.

Known production of special fissionable material (known action at a known
facility, akin to a so-called “breakout scenario” where a state openly uses
the technology to produce special fissionable material).

####  3.1.1 Clandestine production: action at unknown facility

Clandestine production of special fissionable material requires an unknown
facility, tons of source material, and a sufficiently small footprint to avoid
detection – if detected, this clandestine production either stops, or becomes
the known production scenario discussed further below. Thus, the feasibility
of an unknown, undeclared facility is examined.

A ‘smallest device possible’ case is considered (because smaller devices are
more likely to avoid detection). Studies such as those by Kuteev et al. have
been conducted to determine the minimum size fusion device that can emulate
the production of fusion neutrons (see Ref. [63] and other concepts e.g., in
Ref. [64]). Based on optimistic extrapolations of plasma physics, device
engineering, and fusion technology according to Ref. [62], a theoretical
device could draw 40 MW of continuous grid power to produce 1.8 MW of
continuous fusion power. Assuming an 85% duty factor and that 80% of neutrons
are captured in a breeding blanket (containing uranium or thorium), this
device could hypothetically produce 3.5 kg of plutonium or U-233 per year
[62]. This production rate is consistent with legacy fission-fusion hybrid
analyses that estimate the production of 0.64 plutonium or U-233 atoms per
14.1 MeV neutron (from deuterium-tritium fusion), or 2.85 kg of plutonium per
MW-year of DT fusion power generation. Note that lower energy neutrons (e.g.,
2.45 MeV neutrons from deuterium-deuterium fusion) create fewer plutonium and
U-233 atoms since, for one, there is less neutron multiplication.

A facility housing and operating such a device would be easily visible due to
the required subsystems. Reference [62] notes that the 40 MW of continuous
input power and the necessary cooling require large electrical supply lines,
large power conversion buildings, and a significant cooling facility.
Additionally, the device would require a substantial shielding structure, a
remote operating facility, and, in the case of the concept proposed in Ref.
[63], large neutral beam injection systems that are used to heat the plasma.

A facility housing and operating such a device would also have detectable
radiological signatures in the environment, for which monitoring tools exist
under the IAEA Additional Protocol that the international community can
leverage. Sample environmental monitoring data from the Tokamak Fusion Test
Reactor (TFTR) and National Spherical Torus Experiment (NSTX) at the Princeton
Plasma Physics Laboratory are shown in Tab. 1; TFTR operated from 1995-1997,
1998 was a transitional year from TFTR to NSTX, NSTX operated from 1999-2008,
and TFTR underwent decommissioning activities between 1999-2002 [65, 66, 67,
68, 69, 70, 71, 72, 73]. Note that data are skewed and do not correct for rain
and groundwater interactions, nor do they include the distinction between
elemental tritium (HT) and tritiated water (HTO) releases. Further note that
the levels are much lower than the US Environmental Protection Agency’s
tritium concentration limit for drinking water (20,000 pCi/L) [74]. The data
do demonstrate that even trace levels of tritium lost from the facility are
detectable in environmental sampling, particularly the trends from 1995-1997.
Beyond tritium sampling, the fertile (uranium and thorium) and fissile
material leave environmental signatures.

Table 1: Data from annual site environment reports at the Plasma Princeton Physics Laboratory for the TFTR and NSTX experiments. The effective dose equivalent (EDE) is at the site boundary and due only to tritium, onsite surface means maximum tritium concentration in onsite surface water, and onsite soil means maximum tritium concentration in offsite soil samples. Year | Airborne T Released [Ci] | EDE [mrem] | Onsite Surface [pCi/L] | Offsite Soil [pCi/L]
---|---|---|---|---
1995 | - | 0.097 | 789 | 790
1996 | - | 0.320 | 1288 | 2845
1997 | - | 0.430 | 2472 | -
1998 | 592 | 0.120 | 1441 | -
1999 | 348 | 0.156 | 1041 | -
2000 | 728 | 0.211 | 1104 | -
2001 | 184 | 0.618 | 3109 | -
2002 | 2090 | 0.251 | 479 | -
2003 | 451 | 0.089 | 225 | -
2004 | 353 | 0.057 | 502 | -
2005 | 219 | 0.011 | 365 | -
2006 | 514 | 0.014 | 236 | -
2007 | 234 | 0.016 | 257 | -
2008 | 171 | 0.007 | 5473 | -

Lastly, the fertile material, which is itself controlled, would need to be
covertly diverted from a safeguarded nuclear fuel cycle or itself be
clandestinely produced. Taken together, clandestine production of special
fissionable material is not credible since the source material is controlled,
the holistic footprint would be readily visible, and the production would
inherently leave detectable environmental signatures.

####  3.1.2 Covert production: unknown action at known facility

Covert production, where nefarious activity is performed at a known facility,
is not restricted to the small-as-possible fusion device of the previous
subsection on clandestine production since the facility need not be hidden.
Thus, Glaser and Goldston (Ref. [62]) consider a 2500 MWth, 2660 MW plasma
power device with an incident neutron rate of $9.42\times 10^{20}$ n/s. For
simplicity, this paper will consider the same device; however, it is noted
that (i) there is a breadth of commercial fusion concepts that range from a
few MW to a few GW [1, 2], (ii) there are different energy recovery concepts
that change the fusion reactions per MWe, and (iii) there are different fuel
types that change neutrons per MW and neutron energy. All of these
considerations will ultimately change hypothetical production rates of special
fissionable material in a reconfigured device.

Before discussing the theoretical production rates of plutonium and U-233, it
is important to note that the quantity of fertile material injected would need
to be on the order of 500 tons to maximize fissile-material production. Thus,
the quantity of fertile material may already constitute a significant
quantity. This fertile material, especially at this order of magnitude, is
also already controlled.

Assuming the fusion device and quantity of fertile material above, Glaser and
Goldston estimate that a maximum of 20 kg of plutonium or U-233 could be
produced per week (2.5 significant quantities). The limiting factor for
plutonium production is heat loading considerations. The limiting factor for
U-233 production is running out of fuel, i.e., not consuming more tritium than
is produced (since neutrons captured in thorium are hence not being captured
to produced tritium). If the device does not require a closed fuel cycle due
to other sources of tritium, the U-233 production rate could theoretically be
increased to 28.85 kg per week.

Covert operation in a known facility, such as a regulated facility in the
United States, would be practically impossible. The process of breeding
special fissionable material entails introducing and exposing source material
(itself controlled material) to fusion neutrons and then extracting the
material after irradiation (e.g., reprocessing and enrichment). While source
material could be introduced in the coolant or tritium-producing lithium
blanket, detecting these materials is straightforward with existing
capabilities; the detection timescales are on the order of seconds to minutes
for direct measurement or inspection. These capabilities include:

  * •

Easy visual observation of dramatic device changes.

  * •

Detection from general environmental sampling for radiological signatures of
fertile and fissile material since fusion devices do not require
uranium666Some fusion facilities may use uranium getterbeds to store tritium.
However, these getterbeds would generally not be located close to the device
in a large neutron flux. In addition, uranium getterbeds are not required and
titanium, zirconium-iron, or other materials can be used instead. nor thorium
and should not possess these near the device (let alone hundreds of tons);
and,

  * •

Simple tools like portal monitors and metal detectors (currently used at
border crossings and airports, for example) at the entrance and exit that can
be used to detect source or special fissionable material entering or exiting
these facilities.

Thus, covert production of special fissionable material at a fusion power
plant is not a credible threat. These tools can be captured in the licensing
basis of US facilities, and indeed facilities are likely to have pertinent
detectors anyway to ensure proper device operation. These tools can also be
requirements to meet export control approval thresholds – export controls are
discussed in greater detail in Section 2.4 and 3.1.3. Physical security
protocols of the type envisioned in the NRC’s 10 CFR Part 73 safeguards regime
are not applicable here, as those protocols are designed around protecting a
significant quantity of special nuclear material that already exists. For
fusion power plants, there should be no such material and as soon as any is
detected, authorities would be alerted. Once authorities are alerted, this
covert production scenario if continued becomes the known production scenario
discussed in Section 3.1.3.

####  3.1.3 Known production: known action at known facility

This final scenario is breakout, wherein a state openly abuses a fusion power
plant to produce special fissionable material. The timescale to produce
relevant quantities of material depends on the power density of the fusion
device and can range from months to years. It is important to recognize that a
core focus of the nonproliferation regime is on detecting improper use of
nuclear materials – it is not designed to solve a breakout scenario that
occurs. Indeed, the early detection of a breakout scenario is itself a success
of this regime, as it enables states to then bring multiple tools to bear to
isolate and coerce a bad actor into compliance.

Although solving a breakout scenario is beyond the scope of the current
nonproliferation requirements, it is worth noting that fusion offers many
benefits that aid in resolving such scenarios. First and foremost, a clarion
distinction between breakout at a fission power plant and breakout at a fusion
plant is that the fission plant already contains uranium, plutonium, and spent
nuclear fuel. This characteristic of fission plants raises an availability
challenge and also a policy challenge – “as was seen in North Korea, little
can be done short of invasion to prevent a determined sovereign nation from
processing its own Pu for use in nuclear weapons. Massive bombing of the spent
fuel in Yongbyon would have resulted in widespread contamination, an
unacceptable consequence. More limited bombing would have required frequent
repetition to prevent access to the fuel buried in the rubble – also an
unacceptable consequence” [61]. In stark contrast, a fusion facility does not
contain fissile material at the time of breakout and options exist to prevent
operation without risk of contamination. In addition, most commercial-scale
fusion concepts have advertised not requiring post-shutdown cooling [75],
whereas most fission facilities do require such cooling to avoid disaster.
Thus, fusion power plants can generally be immediately shut down with few
repercussions and many subsystems, such as power electronics and magnet
cooling, can be disabled with minimal risk of contamination.

To the extent that limited risks may exist in regard to improper use of a
fusion device, it is in the form of improper modification of commercial
technology and devices. A commercial fusion device would not be designed to
physically accommodate a special fissionable material program. The process of
breeding special fissionable material entails introducing and exposing source
material to fusion neutrons in a specific manner, and then extracting and
purifying the material after irradiation. These facilities do not exist in a
commercial fusion device, and the existing equipment (e.g., pumps, tritium-
producing blanket) would require substantial modification. Such modifications
would likely have deleterious effects on the fusion device operation,
particularly on the fuel cycle in a way that would require additional,
external fuel sources. Thus, the risks above extend to devices that must be
especially designed or substantially modified to be misused. In fact, Glaser
and Goldston note that a 1-2 month period could produce one significant
quantity of special fissionable material and that the majority of this time is
dominated by the time required to reconfigure and restart the facility [62].
This is a critical distinction from fission power, where operation of the
fission reactor as intended creates special fissionable material that can be
used to create a nuclear warhead.

This lesser risk for fusion is thus fundamentally addressable and addressed by
the dual-use export control regime that applies to everything from computer
chips to high-end metals – items that in themselves are not dangerous unless
modified and/or misused by an improper actor (the concern Congress outlined in
Ref. [42]). For all scenarios above and the two sections that follow
(including thermonuclear knowledge and tritium), the existing export control
regime provides protection against the transfer of relevant technology (along
with many other non-fusion technologies) to bad actors – particularly those
known to be at risk of diverting technology across the spectrum for improper
purposes. In the US for example, Supplement 1 to 10 CFR Part 740 of the US
Export Administration Regulations identifies a small selection of
approximately 10 destinations (particularly the Country Group D:2 “nuclear”
destinations) that have already been evaluated as high risk from a diversion
perspective, and for which exports of fusion technology can be restricted. Not
much would need to change in practice. As discussed above, the NSG already
envisioned application of dual-use export control to such fusion technologies,
including certain neutron generators, key technologies and materials, and
tritium breeding systems. Fusion technology as a category need not be subject
to a categorical export control, while those components that may be prone to
abuse would remain incorporated in the dual-use export control regime. See 15
CFR 742.3(a) [76].

The already robust nonproliferation case for fusion can be potentially
enhanced by exploring defense-in-depth via a controls-by-design approach.
Fusion devices – particularly those geared for global deployment – can be
engineered at the outset to include controls to (i) enable remote shutoff,
(ii) force obsolescence without routine maintenance or component replacement
on time scales shorter than those to produce a significant quantity of special
fissionable material (e.g., copy-resistant semiconductors that inherently fail
after some amount of neutron irradiation), and/or (iii) force digital planned
obsolescence. These are technologies in use today, as demonstrated by the
simple example of remote lockout of John Deere tractors pilfered by Russian
forces in Ukraine [77]. Ideally, as fusion devices implement a controls-by-
design approach, the number of destinations that require a license can be
reduced, potentially eventually reaching “EAR99” level of control.

Additionally, longer-term usage-based controls could be implemented to secure
fusion devices from misuse through, for example, a sensor network that
evaluates (a variety of information carriers including) the presence of
special fissionable material and deactivates the machine upon detection.
Usage-based monitoring and controls have been well analyzed. For example, an
analysis by Microsoft and OpenAI explains how “foundational technologies are
also best regulated by restrictions on the end users that can have access to
them, and the end uses to which they can be put” [78]. This analysis includes
user and use verification control, tamper-proof hardware and secure
infrastructure, and AI-enabled identification of problematic uses and users
[78]. Limited reform of the existing export control regime can incentivize
companies to implement these enhanced protections or usage-based controls in
order to reduce or eliminate certain licensing requirements. Further research
and discussion can be conducted in this area to determine how such a regime
could enhance global security while still enabling prompt deployment of fusion
once it is commercialized in the near term.

Lastly, the Additional Protocol’s enhanced tools such as broad environmental
sampling and related inspection of non-nuclear sites and activities can be
leveraged to mitigate any concerns about fusion systems without broadly
incorporating fusion writ large into the nuclear fuel cycle. As discussed
above, use of fusion to breed special fissionable material requires source
material (which is controlled under the NPT), and would be easy to detect
given that a fusion device should have no source or special fissionable
material at all within the facility. Thus, the same way that current
Additional Protocol’s broad sampling tools could be used to enable
verification that covert or undeclared industrial or research facilities are
not being abused to harbor a covert program, these tools can be applied to
help ensure fusion devices are not being so abused.

Taken together, scenarios involving covert and clandestine abuse of fusion
facilities to produce fissile and/or special fissionable material are not
credible. Breakout scenarios nominally are credible, but (i) are themselves
conditional signs of success of the nonproliferation regime to prevent covert
actions, (ii) are less difficult to address for fusion facilities than for
fission reactors, and (iii) can be prevented through application of existing
dual-use export controls and in the future a controls-by-design concept.

###  3.2 Transfer of thermonuclear knowledge

Inertial confinement fusion (ICF) concepts (but not magnetic confinement
fusion concepts777Plasmas are naturally unstable and must be confined. The
amount of fusion in the plasma scales as the product of density and
confinement time. Magnetic confinement fusion uses magnetic fields to confine
a plasma for long periods of time, whereas inertial confinement fusion
compresses a plasma to high densities for a short period of time.) strive to
maximize fusion ignition to achieve very high fusion gains. Some of the
knowledge associated with achieving such high fusion gains may be transferable
to thermonuclear, two-stage (both fission and fusion) weapon development. In
such weapons, the fission core ignites888Ignition is the fusion operating
regime where the energetic, charged particle products are trapped in the
plasma long enough to maintain the plasma’s temperature at fusion conditions
without further, external input energy. and compresses a deuterium-tritium
plasma to fusion conditions (including a very high density), and the core’s
inertia confines the fusing plasma such that large yields are achieved. This
similarity is limited to only those concepts based on ICF using ignited
plasmas and particularly the subset using indirect-drive targets as opposed to
direct-drive targets [79].

Note that a commercial fusion facility or net-electricity device is not
required to perform ICF studies. Current research is performed around the
world at facilities like the National Ignition Facility and the Z-Machine at
Sandia National Laboratory [80, 81, 82, 83]. In fact, A US National Academy of
Sciences report concludes that such research laboratories likely pose greater
risk than a commercial power plant [79]. US laboratory research on ICF has
been largely funded by the nuclear weapons program because valuable
information can be obtained from ICF experiments that can otherwise only be
learned from nuclear testing. A moratorium on such testing by the US was
announced in 1992 by President George H.W. Bush, extended by the Clinton
administration, and remains in effect. The moratorium was reinforced in 1996
when the US signed the Comprehensive Nuclear Test Ban Treaty (CTBT, though it
has not been ratified by the US Senate). The Clinton administration took the
position that ICF is not a prohibited activity under the CTBT, and the NPT
does allow for laser fusion experiments based on an unopposed, US unilateral
statement at the 1975 NPT Review Conference [79, 84, 85].

Initially (1960s), all US ICF research was classified. Declassification began
in the 1970s; for example, essentially all work on direct drive ICF was
declassified by 1974. By the mid 1990s, nearly all information on laboratory
ICF experiments was declassified [79, 86]. The notable exceptions are some
aspects of computer codes, certain target designs, and some historical
experiments related to ICF (particularly the Centurion-Halite program). As
computational power increases, and as plasma physics knowledge accumulates in
accessible literature, many proliferation concerns associated with ICF become
less relevant. Under these circumstances, computer codes would be classified
based on their direct application to and/or calibration from nuclear weapons,
not according to the physics modeled by the code [79]. Thus, the significance
of thermonuclear knowledge to nuclear weapons proliferation is diminishing.

It is important to recognize as well that the risk of thermonuclear knowledge
transfer does not involve the production or transfer of any materials, but
instead the transfer of knowledge to bad actors, generally abroad in rogue
states. Thus, the traditional safeguards regime is less relevant to addressing
this concern and in its stead exists an already-robust export controls regime
that polices such exchanges. A number of export controls already apply to
thermonuclear knowledge, such as the following:

  * •

ECCN 0D999, which includes software for neutron calculation/modeling, software
for radiation transport calculations/modeling, and software for hydrodynamic
calculations/modeling.

  * •

The general end-use prohibition in 15 CFR 744.2, which prohibits any direct or
indirect export of technology that facilitates nuclear weapons development,
including research and design.

For example, export controls are applied to simulation codes like the Monte
Carlo N-Particle (MCNP) code developed by Los Alamos National Laboratory [87].
Taken together, fusion power plants do not pose a novel risk regarding
thermonuclear weapons physics and the risk posed by a subset of concepts can
be treated with already existing export controls.

###  3.3 Use of tritium in nuclear weapons

Nuclear weapons use neutron chain reactions to quickly induce fission in
special fissionable material and generate large amounts of energy [16]. The
primary element of all nuclear weapons – even advanced thermonuclear “hydrogen
bombs” – is the fission core, as it is the only material capable of self-
inducing and sustaining a chain reaction. Tritium and other neutron-rich
elements, however, can be added to nuclear weapons to substantially boost
their performance. In such “boosted” devices, the fission component acts as an
initiator to achieve and inertially confine a burning plasma wherein deuterium
and tritium fuse. This fusion creates more energy and 14.1-MeV neutrons that
are themselves damaging or that can induce further fissions in uranium-238,
for example. Thermonuclear weapons rely on this fission-fusion-fission cycle
[16, 17, 18].

Therefore, tritium has been discussed as a potential proliferation concern
because of its use as a booster. However, tritium is only seen as a vertical
risk, in that it may enhance a nuclear weapon already in existence – it does
not enable a nuclear weapon to come into being999Horizontal proliferation
refers to a state obtaining nuclear weapon capability, whereas vertical
proliferation refers to the advancement of an existing capability.. The
nuclear nonproliferation regime has consistently declined to apply safeguards
to vertical proliferation concerns, strongly indicating a lower level of
concern with these technologies and practical issues with applying strict NPT-
style controls to a vague and expansive group of technologies. The underlying
treaties declined to extend to such components, including the Additional
Protocol in the 1990s declining to add tritium as a concern, creating a
substantial burden to now add tritium [38]. As well, nations have licensed
facilities that produce substantial quantities of tritium without raising
proliferation challenges.

A key driver for this lower level of concern is that vertical proliferation is
only a practical concern for those countries that have already mastered
nuclear weapons technology and, in such cases, access to booster materials is
not a challenge. The US Department of Energy published “the amount of tritium
in a [warhead] reservoir is typically less than 20 g” [88], and “if we
consider the neutron economy of a fission reactor used to produce Pu
[plutonium] and T [tritium],… any nation that is producing Pu for weapons use
can, with relatively minor perturbation, produce adequate T to “boost” these
weapons, even taking into account the $\approx$5% loss of T per year through
radioactive decay” [61, 62]. For example, the US has partnered with Tennessee
Valley Authority’s (TVA’s) Watts Bar Nuclear Plant and Sequoyah Nuclear Plant
to insert tritium-producing burnable absorber rods (TPBARs) that are then
processed to extract the tritium [89].

Furthermore, tritium has a 12.3-year half-life and requires replacement as
part of stockpile stewardship. This technical challenge is somewhat addressed
in modern weapons that use solid lithium deuteride as fuel in place of some of
the tritium: neutrons interact with the lithium-6 and create tritium in situ
[17, 18]. The current treatment of lithium, which can be commonly procured
with no known risk to common defense and security, supports an appropriately
low level of concern with vertical proliferation triggers.

To the extent proliferation concerns exist with tritium (or lithium) as a
nuclear weapons booster, or more particularly, the system that would be
responsible for managing or breeding these materials that would be part of a
fusion device, this does not mean that a fusion device itself creates a
significant proliferation risk requiring application of safeguards or other
issues. Instead, the risk is primarily that foreign bad actors abuse this
material or underlying breeding technology. Therefore, the materials can be
themselves independently secured through export controls. Indeed, both tritium
and lithium-6 are subject to strict dual-use export controls administered by
the U.S. Department of Commerce, including but not limited to [50, 44]:

  * •

Export Control Classification Number (ECCN) 1C235, “Tritium, tritium
compounds, mixtures containing tritium in which the ratio of tritium to
hydrogen atoms exceeds 1 part in 1,000, and products or devices containing any
of the foregoing,”101010Tritium that is produced specifically in a nuclear
reactor is currently controlled by the US NRC in its regulations set forth in
10 CFR Part 110. See ECCN 1C235 note; 10 CFR 110.9(c). The basis for NRC
regulation is because the NRC as a general matter regulates the export of any
byproduct material produced in a nuclear reactor (including everything from
tritium to cesium) regardless if it carries a proliferation concern. See 42
USC 2111, 2112. Indeed, tritium produced through other mechanisms (e.g.,
particle accelerators) would appear to remain regulated by the Department of
Commerce. See ECCN 1C235 note.

  * •

ECCN 1A231, “Target assemblies and components for the production of tritium,”
and

  * •

ECCN 1C233, “Lithium enriched in the lithium-6 (6Li) isotope to greater than
its natural isotopic abundance, and products or devices containing enriched
lithium, as follows: elemental lithium, alloys, compounds, mixtures containing
lithium, manufactures thereof, and waste or scrap of any of the foregoing.”

These material-based export control protocols are already in place and ready
to control the global distribution of tritium and other theoretical boosters
when fusion is commercialized. This paper discusses how these controls can be
updated to reflect a usage-based “controls-by-design” approach that provides a
high level of assurance that these items cannot be exported to bad actors that
will abuse the materials.

In summary, tritium material does not contribute to the horizontal
proliferation of nuclear weapons, but has some potential to contribute to
vertical proliferation. That said, vertical proliferation has historically
been treated as a lower concern, with multiple sites in the United States
containing tritium licensed without any indication of or reference to
proliferation risk. Moreover, the vertical proliferation risk posed by fusion
is not particularly novel nor more-enabling than a state already capable of
producing, for example, plutonium. To the extent a concern is identified,
already existing export controls can control the distribution of these
materials.

##  4 Conclusion

Understanding that fusion falls outside the NPT and IAEA safeguards framework,
as explained in section 2, this paper in section 3 evaluates whether fusion
raises a nonproliferation risk substantial enough to warrant amending that
framework, or if addressing fusion through dual use export controls is more
appropriate.

Based on the evaluation in this paper, it does not appear that amendment of
the NPT is warranted in light of the fundamental differences between the
intended use of the fusion technology and its potential contribution to
proliferation – underscored by the fundamental differences between fission and
fusion from a nonproliferation standpoint. Additionally, amending the NPT is
largely a geopolitical issue and would require extensive global consensus,
which is not an easy task and likely infeasible.

With that said, certain components and materials related to fusion are and
should continue to be regulated as “dual-use” items, in alignment with the NSG
Part 2 Guidelines, due to their potential use for commercial and misuse for
proliferation purposes. And fusion developers should continue to look to ways
to incorporate “controls by design” into their device design, and engaging in
discussions with the nonproliferation community in doing so. Additional work
can be done as the technology matures to develop a right-sized export controls
framework for fusion.

Taken together, these measures are and will be sufficient to ensuring only
peaceful uses of fusion energy that contribute to global peace, security, and
prosperity.

## References

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##  Appendix A Use of tritium in radiological dispersal devices

A potential concern raised with fusion is the use of certain associated
radioactive materials in radiological dispersal devices (RDDs). These RDDs or,
“dirty bombs,” are different from nuclear weapons: instead of utilizing
nuclear reactions to achieve large detonation power, a conventional explosive
is used to spread radioactive material across a populated area. All
radioactive materials, such as cobalt-60, are potentially usable in an RDD. In
the fusion context, tritium (T) – a fusion fuel or byproduct for most designs
– could theoretically be included in an RDD in the form of tritiated water
(HTO), directly, or in the elemental form of HT if the explosive device causes
the HT to oxidize to HTO111111The dose consequences/health effects of HTO are
$\approx$10,000 greater than that of HT. Additionally, HT rises much like a
helium-filled balloon, whereas HTO does not and has a higher probability of
entering the ecosystem.. Note that RDDs are not considered a proliferation
concern (rather a broader security concern), and is included here for
completeness.

Note that fusion facilities produce neutrons that may activate (make
radioactive) materials via neutron interactions, and these materials may reach
quantities and concentrations relevant to RDD risk. Quantity and concentration
depend on the fusion power plant design (materials to be activated and their
proximity to the fusion), the power level (amount of neutrons), and fuel type
(amount of neutrons and neutron energy – higher-energy neutrons, such as those
from deuterium-tritium fusion (14.1 MeV) compared to those from deuterium-
deuterium fusion (2.5 MeV), have more ways to activate material). Since (i)
the treatment of activated materials would be equivalent to that of tritium,
and (ii) the range of materials is specific to power plants, specific analysis
is omitted in this paper.

The use of radioactive materials in RDDs is not a novel concern, nor does it
raise nuclear weapon proliferation issues given that the materials used cannot
themselves be used as the core of a nuclear weapon. Defense against RDDs is a
matter of (physical) security rather than safeguards. The current
countermeasures (for over 80,000 sources [90]) in the US are set forth by the
Nuclear Regulatory Commission (NRC) via its regulations in 10 CFR Part 37:
Physical Protection of Category 1 and Category 2 Quantities of Radioactive
Material [91]. Part 37 provides “requirements for the physical protection
program for any licensee that possesses an aggregated category 1 or category 2
quantity of radioactive material,” with specific radioactive materials of
concern delineated in an appendix to the regulations. Category 1 and 2
materials are classified as follows, where $A$ is activity and $D$ is an
isotope-specific danger metric:

  * •

Category 1 sources, if not safely managed or securely protected, would likely
cause permanent injury to a person in contact with them for more than a few
minutes. It would likely be fatal to be close to this amount of unshielded
material for a period of a few minutes to an hour. The activity ratio (A/D) is
$\geq$ 1000\. These sources are typically used in radiothermal generators,
irradiators, and radiation teletherapy [91, 92].

  * •

Category 2 sources, if not safely managed or securely protected, could cause
permanent injury to a person in contact with them for a short time (minutes to
hours). It could be fatal to be close to this amount of unshielded radioactive
material for a period of hours to days. The activity ratio is 1000 $>$ (A/D)
$\geq$ 10\. These sources are typically used in industrial gamma radiography,
high- and medium-dose rate brachytherapy, and radiography [91, 92].

The thresholds for category 1 and category 2 are based on the IAEA Code of
Conduct titled “Code of Conduct on the Safety and Security of Radioactive
Sources” [93, 92]. This code reflects the findings produced by the
International Conference on Security of Radioactive Sources held in Vienna in
March 2003 (the Hofburg Conference). The G-8 annual summit (of “the Heads of
State and Government of the eight major industrialised democracies and the
Representatives of the European Union”) then issued a statement on “non
proliferation of weapons of mass destruction – securing radioactive sources”
wherein it encouraged all countries to observe the Code of Conduct by
strengthening controls on radioactive sources [94].

The NRC has determined that its regulations, based off of the IAEA Code of
Conduct, are sufficient to provide reasonable protection against RDDs by
“protecting these materials from theft or diversion” [91]. Note that plutonium
is included in the category listing. Part 37 contains a robust set of security
protections, including access controls, monitoring and detection,
establishment of security zones, and coordination with local law enforcement.
Additional protections exist for the transport of radioactive materials.

Currently, tritium is not listed in the NRC’s listing of category 1 and
category 2 materials, but inserting tritium would not be difficult. Tritium
was left out of the listing because it was considered “never available in
sufficient quantities at one location to be of use in an RDD” [95]. Thus, if
the advent of fusion energy sufficiently changes this assumption on the
abundance of tritium, it is appropriate and sufficient (insofar as RDDs) to
maintain the security of tritium via Part 37.

Tritium-specific threshold values for category 1 and category 2 would be based
on D-values that define a dangerous source, i.e., “a source that could, if not
under control, give rise to exposure sufficient to cause severe deterministic
effects.” IAEA TECDOC-1344 derives the D-values [96] and also “provides the
underlying methodology that could be applied to radionuclides not listed”
[92]. Tritium is listed in Table I.2 of TECDOC-1344. Based on these values
(and assuming a tritium specific activity of 9640 Ci/g), the category 1
threshold for tritium would be $2\times 10^{6}$ TBq ($\approx 5\times 10^{7}$
Ci, $\approx$5.6 kg) and the threshold for category 2 would be $2\times
10^{4}$ TBq ($\approx 5\times 10^{5}$ Ci, $\approx$56 g). Note that isotope
thresholds are smaller when combined with other radioactive materials and the
levels are determined by a sum of fractions law (e.g., if a site possesses 25%
of the cobalt-60 threshold and no other radioisotopes, the tritium threshold
would be 75% of the aforementioned values).

Taken together, while the presence of tritium in significant quantities poses
a security risk by way of RDDs, it is not a nuclear weapon proliferation risk.
The US regulatory regime via 10 CFR Part 37 addresses existing RDD risks
through physical security and monitoring measures in place for category 1 and
category 2 quantities of radioactive material. The tritium RDD risk can be
handled by augmenting Part 37, particularly Table 1 in Appendix A, with the
appropriate quantity thresholds for tritium: 56 g for category 2 and 5.6 kg
for category 1.