Nuclear Safety Technology and Regulation
2024

Summary and Main
Outcomes of the NEA
Nuclear Safety Research
Joint Projects Week
Success Stories and Opportunities for
Future Developments

Summary and main outcomes of the NEA nuclear
safety research joint projects week: Success stories
and opportunities for future developments
For over 65 years, the Nuclear Energy Agency (NEA) has served as a flexible and powerful platform for
multinational research co-operation, particularly in areas related to nuclear safety. The projects conductedunder the NEA auspices have enabled nuclear safety regulators, technical support organisations (TSOs), thenuclear industry and research organisations to share research costs and results and develop expertise. This,in turn, has supported safety regulations and practices and facilitated their harmonisation around the world.
The safety research projects include experiments that address a particular safety issue and close aknowledge gap; creating and maintaining shared event, system and component databases that can be used
to identify operational issues and good practices; or benchmarking
safety models. They have contributed to the preservation of essential
research facilities, to the development of expertise and to training andProjects have played a
education by involving students and young professionals. With an eye
tremendous role to help us
to the future, special attention is also paid to ensuring the projects’
harmonise and have a common
data can be accessed and used in the long term.
understanding … of science and“

The NEA held a Nuclear Safety Research Joint Projects Week
virtual event (NEA, 2023a) from 9 to 13 January 2023 to review theaccomplishments of NEA Joint Nuclear Safety Projects (NEA, 2023b)
over the last four decades and to discuss future perspectives. Througha series of webinars, leaders in the sector and research project
operators discussed the outcomes of close to fifty nuclear safety
projects (see Figure 1) and examined how the established frameworks,
research platforms and networks could effectively support future
developments in nuclear energy.
05technology issues affecting thesafe operation of nuclear facilities… there are so many things thatcan be done together even in acompetitive environment
William D. Magwood, IV
NEA Director-General

”
10

15

Fuel performance and safety
Thermal-hydraulics in circuits
Severe accident (SA): Containment
SA: Progression in and ex-vessel
SA: Source term
SA: Major accidents
Structural integrity and LTO
Fire research
Human technology and organisation
Risk assessment
High temperature gas reactor

Figure 1. The safety technical areas covered by the NEA joint nuclear safety research projects

SUMMARY AND MAIN OUTCOMES OF THE NEA NUCLEAR SAFETY RESEARCH JOINT PROJECTS WEEK, © OECD 2024

1

Around 450 experts from 59 countries and several international organisations attended the webinars.
Participants highlighted the benefits of the NEA projects to nuclear safety stakeholders and theirimportance for building research platforms and the competencies needed to develop the nuclear sector.
A key point of discussion was related to the challenges ahead, in particular the effectiveness and efficiencyof these activities, but also how they might better serve the development and maintenance of key skills
and research infrastructures in the future.

OFFICIAL USE ONLY / À USAGE EXCLUSIFIn addition, participants explored new ways of encouraging public and private stakeholders to contributeto the funding of future safety research joint projects. Several additional objectives, listed below, werediscussed and are being addressed (see also Figure 2).

PIRTs forinnovative designs
and phenomena
related to LTO
issuesOrganise an R&D
and databases
framework
model

Establish asafety researchboard - roadmap

Engaging with
policy making
bodiesFigure 2. Proposed path forward for enhancing project frameworks and defining research plans

 Regarding the joint projects’ frameworks:−© 2023 OECD/NEA

Promoting a more integrated approach in safety research around sets of experimental platforms
www.oecd-nea.org
1
in the main safety technical areas, whereappropriate, e.g. in the thermal-hydraulic area;−

Engaging with policy-making bodies, efficiently recruiting stakeholders and growing the funding
base;

−

Contributing more broadly to education, training and knowledge dissemination;−

Securing the quality assurance (QA), preservation and dissemination of the project results forthe benefit of the nuclear safety community and organising, where needed, database framework
models;−Increasing interaction between joint research projects and relevant NEA working groups tobroaden as much as possible the insights into the projects as well as the communities
supporting them.

 Regarding research plans:−

Establishing a safety research roadmap, prioritising work globally and by safety technical area,
so as to balance the needs of currently operating and future reactors1;−

Developing Phenomena Identification and Ranking Tables (PIRTs) for innovative reactor designs
and phenomena related to long-term operation (LTO) issues.

The following report sets out in more detail the main conclusions and recommendations of the event.

1. In this document, “future reactors” refers to Generation III, III+ and IV reactors as well as light water (LW) and non-LW small
modular reactors (SMRs).

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SUMMARY AND MAIN OUTCOMES OF THE NEA NUCLEAR SAFETY RESEARCH JOINT PROJECTS WEEK, © OECD 2024

Objectives for NEA Nuclear Safety Research Joint Projects
Frameworks
International co-operation in nuclear safety research is vital and participants of the Nuclear Safety Research
Joint Projects Week highlighted how the NEA plays a key role and has long-standing experience inestablishing fora for joint research projects, standard agreements, and best practices (e.g. in export control)
as well as data preservation and distribution through the NEA Data Bank. The current frameworks proposedby the NEA are considered to be pragmatic and efficient for managing collaborative research with a rangeof organisations sharing interests and funding. They enable dynamic research to be managed, for example
by investigating new issues and phenomena identified during a project, dealing with unexpected results, or
discussing the application of results on a reactor scale. However, participants proposed several directions
to improve the sustainability, efficiency and benefits of nuclear safety research joint projects.
Although only nuclear safety research joined projects were discussed at the event, some of the directions
proposed may be relevant for NEA projects developed in other fields (e.g. in nuclear science, radioactive
waste management and radiological protection).

To propose more integrated frameworks to better preserve and develop
fundamental research capabilities and expertise in nuclear safety
While it is not the primary mission of NEA safety joint projects to help develop and maintain core nuclear
safety research capabilities, experts highlighted how they have effectively contributed to this over theyears (NEA, 2021). These unique experimental infrastructures, state-of-the-art instrumentation andanalytical techniques remain key for the development and sustainability of the nuclear sector, for thesafe long-term operation of existing nuclear plants and the licensing and deployment of future reactors.
At the same time, these activities largely support the development of expertise in several nuclear safety
technical areas, including nuclear fuel performance and safety, thermal-hydraulics, severe accident andcontainment phenomena, structural integrity and long-term operation (LTO), fire risk management andhuman-technology organisational (HTO) factors.
Despite periodic reviews under the auspices of the Committee on the Safety of Nuclear Installations(CSNI) to identify core nuclear safety research facilities that need to be maintained (see the 2021 updateof Nuclear Safety Research Support Facilities for Existing and Advanced Reactors [NEA, 2021]), some corefacilities have been lost or are still at risk of being lost in key nuclear safety areas, particularly in the studyof potential accidental situations and the effectiveness of safety approaches and systems to deal with them.
One should bear in mind the loss of capabilities to carry out irradiation experiments (e.g. the closure of
the Norwegian Halden reactor in 2018 and more recently the loss of access to the Russian MIR reactor forinternational collaboration) but also the planned loss of large-scale experimental capabilities for thermalhydraulic investigations (e.g. the foreseen closure of the German PKL facility in 2024 and of the Japanese
LSTF facility in the near future and the recent loss of access to the Russian PSB-VVER facility). The closureof these facilities also entails the risk of losing highly qualified expertise specific to the experimental
activities in the nuclear sector.
The main risk of losing capabilities is related to financial reasons. The high costs to develop, operate andmaintain, upgrade, or adapt the facilities for evolving needs2 have been highlighted. This is particularly
true for nuclear research reactors. Long-term commitments are needed at the international level to provide
financial support for most research infrastructures in the field of nuclear safety. Establishing stronger
2. For example, state-of-the-art instrumentation to provide data to validate advanced multi-dimensional, multi-physics models,
and the versatility of the facilities to address a variety of advanced designs.

SUMMARY AND MAIN OUTCOMES OF THE NEA NUCLEAR SAFETY RESEARCH JOINT PROJECTS WEEK, © OECD 20243

collaboration in key nuclear safety areas around experimental platforms, encompassing state-of-the-art
facilities in various countries with a mechanism for cost-sharing, could help develop and maintain coreresearch capabilities. For reasons of cost-effectiveness, the complementarity of facilities from different
organisations should also be considered to a greater extent than in the past. Indeed, to address different
technologies, design boundary conditions and scales, it would be beneficial to collaborate around sets ofmulti-purpose facilities able to address new questions and covering a wider range of interests.
For example, experimental reactors providing for transient irradiation testing capabilities have been
considered essential to support nuclear fuel design, validation and performance. This is why the NEA
Second Framework for Irradiation Experiment (FIDES-II) (NEA, 2023c) and related Joint ExpErimental
Programmes (JEEPS) have been launched with the support of a large community. This framework is
considered an essential and effective step in maintaining irradiation capabilities. However, continued
attention should be given to smaller and unique facilities at risk which provide for out-of-pile testing.
In the same vein, it is recommended that the development of similar research frameworks in other key
nuclear safety technical areas be considered. The objective would be to define sets of complementary
experimental facilities with mechanisms to maintain and develop capabilities to address a wide range
of interests, to develop and extend a strong partnership, to support facilities’ operating agents and to
maximise the value of acquired knowledge. In addition, consolidating co-operation between various
facilities and experimenters contributes to the development of solid technical expertise.
Thermal-hydraulics is considered a priority technical field. A number of core facilities will be closed in thenear future. New facilities dedicated to future reactors and related safety systems, including passive safetysystems, may become available for collaborative research in the coming years and several safety issues
both for operating and future reactors are already identified and need to be addressed. Other options
need to be explored to address questions related to structural integrity and long-term operation (LTO), in
particular how to establish co-operation on “harvesting activities” and related research, as well as newissues related to severe accident and containment phenomena.
A first step could be to organise fora of critical facility owners in key technical areas. This would identify
the core facilities that will be open to collaborative research in the short and long term, as well as thesafety topics that can be addressed in these facilities. International joint projects could thus be judiciously
organised in conjunction and complementarity with national projects to provide additional support for
operating agents.

TREAT reactor.

Individual TRISO fuel particles at 100 µm scale.

Idaho National Laboratory, United States

Idaho National Laboratory (CC BY 2.0)

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To involve more stakeholders to broaden the projects’ partnership andfunding baseDifferent stakeholders in the nuclear sector with various responsibilities and interests (regulators, technicalsupport organisations [TSOs], research institutions and laboratories, industry including both utilities andvendors), have joined NEA nuclear safety joint research projects over the years. The experience showsthat it is essential to have all stakeholders involved at a very early stage in defining a project if they are
to derive maximum benefit from it. In addition, preparatory discussions are essential to convince a wide
range of potential partners to become involved in the project to increase its added value. Mechanisms
should be set to have appropriate upstream discussions to get stakeholders on board in due time.
The number and type of members in a project will affect its robustness
and sustainability. Having more members makes it possible to sharethe costs and risks of the project, facilitating the performance ofexperiments. There are several advantages to recruiting new members:
increasing the budget or reducing the cost burden on members and theparticipation of a larger set of experts, mixing different skills and adding
insight into experiment design and analysis, ultimately increasing thevalue of the experiments. Strengthening the networking opportunities
is a good way to attract more organisations to projects. Fora, open
seminars valorising the safety applications of project results, andco-operation frameworks with external scientific communities in areas
not specific to the nuclear sector (e.g. human-technology organisation[HTO], fire risks, cybersecurity, external events, application of digitaltechnologies and artificial intelligence [AI]) could help motivate newparties. In addition, establishing common understanding between
different stakeholders should ultimately facilitate discussions related
to licensing between independent stakeholders.
It is also essential to broaden the funding bases if there is a need tocover a wider range of interests. Some governmental organisations
currently fund most of the NEA’s joint research projects on nuclear
safety and these organisations have expressed concern that they will
not be able to participate in additional projects requiring more funding
than they are currently investing.

“

NEA projects allow EPRI toleverage our members’ researchdollars, connect to a global
network of peers, and accelerate
deployment of technology
Jean Smith
EPRI

“

”

For newcoming countries in the
nuclear field, the co-operationand the partnership is very
important to have sustainablesafe nuclear programmeRaoul Awad
FANR”

Recruiting more industry partners to share the funding allocated to a country could broaden the fundingbase for projects. For example, projects addressing issues that would facilitate the licensing process could
be of great interest to industry and utilities. At the same time, as the industrial landscape in the nuclear
sector evolves, including with newcomers and smaller companies, it may be interesting but challenging
to find adequate mechanisms to attract these newcomers. Setting up the appropriate frameworks andagreements to conduct collaborative research in the best interest of all stakeholders will require particularattention to issues such as balanced discussions with all stakeholders, conflicts of interest and the challenges
of disclosing scientific data. It would be interesting to plan more information meetings to make industry
decision makers and the research laboratories that support industry aware of any proposed joint projects
and to assess how these could be designed to also meet some of the priority research needs not coveredfrom the industry sector perspective. This initiative can be discussed under the auspices of the CSNI.
Recruiting partners from nuclear countries currently not involved or with low involvement in joint projects is
another way of broadening the funding bases. Efforts could be undertaken to make these countries aware of
the opportunities offered by the current framework of joint projects. Furthermore, mechanisms could be put
in place to facilitate access for “new” nuclear countries to support capabilities building in these countries.
In some cases, export control issues may limit the possibilities of adding new members to some projects.
These limitations should be addressed during upstream discussions related to project development.

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To make a wider contribution to education, training and dissemination ofknowledge
In general, knowledge, data and expertise gathered through nuclear safety joint projects enrich the bodyof scientific knowledge underpinning nuclear safety. Joint projects contribute to nuclear safety capability
building in the participating countries. Conversely, the communities involved in the projects have a
responsibility to share the knowledge gained more widely for the benefit of the nuclear safety community
as a whole. Projects should help to create a safety culture and expertise in nuclear developing countries
and to maintain or strengthen it in nuclear countries, where necessary.

“

A major challenge is to attract
young students in the nuclear
sector; research done in the joint
projects is international top levelresearch with a lot of potentials to
attract young talents
Katharina Stummeyer
GRS

”

“

Halden secondees have become
technical experts in member
countries
Toyoshi Fuketa
NRA

The projects generally involve the active participation of young
scientists (PhDs, post-docs.) in experimental and analytical activities,
mainly from participating organisations with research activities.
Often, students from universities collaborating with participatingorganisations have also been involved in joint project activities.
While the interest of young researchers in the nuclear sector declined
after the Fukushima Daiichi Nuclear Power Plant accident, thetrend seems to be reversing, with increased interest linked to thedevelopment of new technologies such as SMRs.
Including strong co-operation with major universities in a project
is of great value. Universities and research laboratories have madeand continue to make very valuable contributions to some projects,
providing access to complementary smaller-scale testing capabilities
and resources devoted to the development and validation of
fundamental models. These added capabilities benefit the projectcommunities overall. Project members should be encouraged
to consider academic institutions’ involvement in the design,development and execution of joint projects.

Conversely, a joint project can be an opportunity to develop
educational tasks, as was done e.g. in FIDES-II, HALDEN, HYMERES,TAF-ID and TCOFF. Training and education should be offered to project
members and, where appropriate, non-members. This can be done,for example, by organising summer schools or seconding trainees
to facilities. The current framework allows for personal secondments to facilities, which in the past wase.g. efficiently used at Halden, with secondees who became recognised fuel safety experts and it would bevaluable to make greater use of this possibility to supervise and train new experts in nuclear safety.

”

In the future, it would be beneficial to dedicate in all new safety research projects resources and a part ofproject budgets to support training and education tasks.
A partnership with the NEA Nuclear Education, Skills and Technology (NEST) framework (NEA, 2023d)
could also be envisaged, as it has been implemented, for example, for the HYMERES safety project.
Systematic sharing of project outcomes contributes to the dissemination of “safety knowledge”. Projectcommunities should consider organising extended workshops (involving non-members or other related
communities) during the project. The participation in major conferences (with, for example, dedicatedproject sessions) in key safety technical areas should be considered more systematically. Past positive
experiences in this respect should be used to implement, as far as possible, such dissemination activities
in all ongoing and future projects.

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To preserve and disseminate high quality data produced by the joint
projects
Most projects, after a period of non-disclosure, deliver data packages to the NEA Data Bank (NEA, 2023e) forpreservation and distribution to NEA members on request. The NEA Data Bank has extensive experience inthe preservation and dissemination of data. The crucial role of the NEA Data Bank as a central, secure, anddurable repository for key datasets relevant to nuclear safety applications is well recognised.
Having a common database for safety applications, with legacy data sharable and available, brings greatvalue to the safety community and is seen as cost-effective.
Ensuring a high level of quality for the data used to develop andvalidate physical models of safety codes is essential for risk assessment(through probabilistic safety analyses [PSA] and reliability analyses)
and the evaluation of safety margins. Having high quality data as partof the joint project helps to build confidence in safety assessments.
Durably preserving data and providing users with reliable informationon their quality insurance (QA) is considered essential.
The NEA and the project communities have a common interestin guaranteeing the quality and completeness of the data madeavailable to member countries. These data should include as much as
possible raw and processed data, as well as explanatory documents(e.g. technical reports) in order to be usable. They can thus be usedover the long term in a safe and sustainable manner. Though there may
be proprietary or export control issues in some cases, data collection
should prevail in all cases, with appropriate distribution schemes
and distribution agreements in place with data owners. The NEA has
for instance engaged substantial efforts to collect the Halden project(NEA, 2023b) legacy database, which is a unique resource compilingthe results of 65 years of research on fuel performance and safety, andto propose appropriate distribution schemes.

“

Data preservation in (an) efficientand easy-to-use manner is avery urgent issue because many
experts are retiring. A qualified
documentation of the data is as
important as data production
Ki-Yong Choi
KAERI

”
“

The preservation of key facilities,
skills, high-quality data isessential (for the nuclear industry)
Manuel Carrasco
EDF”

Processing key data sets, as part of more collaborative activities
such as International Standard Problems (ISPs) and benchmarks, isan efficient tool for assessing data completeness and QA for safety
applications, although such activities generally require significant
resources. Selected data sets from most, perhaps all, projects have been processed through ISPs or
benchmarks, including blind and open phases, with generally documented results. Some projects, such as
RBHT (NEA, 2021), have been specifically designed for benchmarking codes with co-ordinated blind andopen benchmarks for all generated data sets and detailed uncertainties evaluations for a selection of data
sets. More systematic approaches to exercise data should be implemented in all projects with collective
engagement of project members. This way, members get better value from projects with qualified dataand enhanced codes.

In addition, it is important to have appropriate tools to easily search and find data in large databases(e.g. for comparative analyses of test series or counterpart tests). Current databases do not necessarily
provide appropriate search tools. It could be useful, in that respect, to assess the cost-benefit ratio ofmodern technologies such as artificial intelligence. The NEA Data Bank could assess the potential benefitsof using modern tools to query large databases.
Nevertheless, managing and keeping alive large databases (making them updated, with information on
data QA, and durable) requires significant manpower and is costly. This is why the NEA identified two

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major actions: 1) to summarise best practices in data preservation and dissemination and recommend
enhancements; and 2) to prioritise the effort on databases which will undoubtedly be used extensively
in the future. The Senior Expert Group on Preservation of Key Experimental data sets, which operates
under the CSNI, in relation with the Nuclear Science Committee (NSC) and the Management Board for theDevelopment, Application and Validation of Nuclear Data and Codes (MBDAV), will provide conclusions
and recommendations on efforts needed and best practices in 2024.
In parallel, a number of activities have been proposed to specify the priority data needs in the nuclear fueland the thermal-hydraulic fields3 and for databases supporting LTO, such as material ageing databases.
The nuclear fuel and the thermal-hydraulic database will be used to assess the safety of future light water
reactors (LWRs) with use of current and near-term new fuels and claddings4, and will be possibly extended,or specific databases created, to address non-LWR technologies and advanced fuels4. Following these
specification activities, building the databases themselves will require substantial expert manpower
and funds which could be appropriately set through joint projects. A broad commitment from nuclear
stakeholders to support future joint projects on safety databases for nuclear fuel, thermal-hydraulics and
LTO would benefit the nuclear sector and be cost-effective.

To benefit from closer co-operation between joint projects and relevant NEA
CSNI working groups as well as between the joint projects themselves
Increased networking is a good way of advertising projects and ensuring that their development is
supported by the widest possible community.
It is useful to put in place mechanisms to allow experts from CSNI working groups in given technical areas
to contribute with as many points of view as possible when developing projects and evaluating project
results. Such mechanisms are already in place in some CSNI working groups and appear to have been
efficient. They comprise:
 Systematic presentations of joint project proposals by operating agents in working group meetingsand collection of insights from experts;
 Systematic presentations of projects outcomes with focus on applications by operating agents;
 The organisation, with the approval of projects members, of analytical activities (e.g. International

Standard Problems [ISPs], benchmarks) accessible to non-members to further assess key project
data sets.
Other meetings, such as expert groups to review the scope of project proposals or final project workshopswith wider participation (beyond members) usually jointly organised by the NEA and the operating agents,
should be systematically advertised in the relevant working groups under relevant standing technicalcommittees, in particular the CSNI.
Working groups’ “strategic” documents (see for instance NEA [2023f], recently released by the Working
Group on Analysis and Management of Accidents, or WGAMA) as well as state-of-the-art reports, ISPs,
benchmarks and workshop conclusions can effectively inspire the development of project proposals,
as they generally highlight research gaps. An example is e.g. reports released by the Working Group on
Fuel Safety which highlighted research gaps in Reactivity Initiated Accidents (RIA) which are addressed

3. In these two areas, the NEA has launched activities to work on specifications for databases, under the Working Group on
Fuel Safety and FIDES-II for fuel safety and under the Working Group on Analysis and Management of Accidents for thermalhydraulics, starting from the past CSNI Code Validation Matrix effort (NEA, 2014).
4. The same definition is used here as in Table 1 of the FIDES-II strategic plan document (NEA, 2023c).

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SUMMARY AND MAIN OUTCOMES OF THE NEA NUCLEAR SAFETY RESEARCH JOINT PROJECTS WEEK, © OECD 2024

in the ongoing CABRI International Project (CIP) and FIDES-II HERA (NEA, 2022). Other documents, suchas working group discussions and country reports in working groups can also be the source of project
opportunities. It may be recommended for working group members to invite project operating agents toparticipate in working groups meetings and activities and to share the findings and recommendations ofthese activities more widely in their country.
The CSNI Programme Review Group (PRG) and the CSNI are informed of project proposals and projectsummary reports at an early stage. CSNI members are advised to make their organisations and networks
aware of project proposals.
Co-operation between relevant projects could be enhanced by organising counterpart testing, joint
workshop or joint benchmark activity. This has already been the case in the past, for example between
thermal-hydraulics projects (ROSA, PKL, ATLAS) with counterpart tests, joint benchmarks and analyticalworkshops or fire projects (PRISME, FIRE) with common benchmarks. It could be applied in other technicalareas, such as between HALDEN, SCIP and FIDES-II regarding loss-of-coolant accidents (LOCA), between
PANDA and THEMIS regarding containment and safety systems issues, or between ESTER and THEMIS
regarding source term issues. See (NEA, 2023b) for information on above-listed nuclear safety joint projects.

View of the ATLAS experimental loop.
KAERI, Korea

Top view of the PKL facility.
Framatome, Germany

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Research perspectives
Establish priorities and provide guidance for the development of convincing
project proposals for decision makers
Several new reactor and fuel concepts are currently being considered for deployment, and the ability of
regulators and TSOs to respond in a timely manner remains a challenge. An increasingly wide range ofconcepts (for example, reactor designs including Generation III+ and IV, SMRs with LWR and non-LWR
technologies and, possibly, non-electric applications, near-term new fuels and claddings and advanced
ones4, advanced materials, and passive safety systems) could have an impact on safety assessment
methods. At the same time, questions remain concerning large LWRs in operation, in particular to ensure
long-term sustainable operation beyond 60 years and modernisation5.

“

Nuclear safety research shouldlook ahead and help us being
ready for the future with licence
renewal for existing reactors andnew reactors applications (lightwater, non-light waters, SMRs)
Ray Furstenau
US NRC”“The NEA could play a key rolein setting up the internationalsafety research agenda and define
priorities for research projects
Jean-Christophs Niel
IRSN”

It is necessary to prioritise and concentrate efforts on the main nuclear
safety issues for technologies whose deployment is envisioned in the
short term and for those that must be maintained in operation. The
challenge could be to find the best funding balance to support these
two types of needs and associated core research infrastructures.
With the support of the CSNI, creating a comprehensive high-levelroadmap for prioritising nuclear safety research needs and identifying
major gaps and capabilities requirements would help research facility
operators develop appropriate joint project proposals. The roadmap
should determine whether current and planned research capabilities
are sufficient to meet regulators’ needs in their independent safetyassessment.
This roadmap must use input from previous NEA initiatives. The
NEA is developing The NEA Small Modular Reactor Dashboard(NEA, 2023g) to characterise nuclear technology development andeconomic perspectives. It has also put in place, under the CSNI, theExpert Group on Small Modular Reactors (EGSMR), which has recently
provided the CSNI with research recommendations to support the safe
development of SMRs (NEA, 2023h). One of the challenges is that the
research is currently focused on deployment and technology needs
rather than identifying the R&D issues that should be addressed tobuild confidence in the robustness of these technologies with respect
to safety goals and requirements, for instance investigations related
to demonstrating the effectiveness of the management of potential
accidents in new concepts.

The other challenge is that there is currently a lack of design-specific data in the public domain to support
the safety assessment of reactor designs under development, such as SMRs. There is a need to establish aconsensus on which generic phenomena should be given priority.

5. For instance, accident tolerance of high power reactors, management of severe accident with core melt, limiting further
radiological consequences for potential accidents, use of new technologies like digital I&C, cybersecurity, artificial intelligence.

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High-temperature
Engineering Test
Reactor (HTTR).
Japan Atomic Energy
Agency (JAEA)

Moreover, a number of research facilities that have been developed to support the design of future reactors,
including SMRs, are not open to collaborative research. An IAEA-NEA joint effort has been launched under
the Nuclear Harmonization and Standardization Initiative (or NHSI, an IAEA complementary initiative thataims to advance the harmonisation and standardisation of SMR design, construction, and regulatory
and industrial approaches) to create by mid-2024 a booklet listing the facilities available for collaborative
research. More generally, synergies between the NEA, IAEA and European Commission joint research
projects could also be beneficial in some areas.
Based on this roadmap, the CSNI should assess the need to extend the expertise of its groups totechnologies other than LWRs and to advanced fuels and claddings, and to advanced materials6. In the
short term, it is important to achieve a timely rebalancing of R&D programmes, which currently focus
mostly on large LWRs and conventional fuels and claddings. This could be achieved by organising
Phenomena Identification and Ranking Table (PIRT) exercises to identify major gaps and pressing issues.
Such exercises would certainly help to define project proposals to meet these priority needs.
CSNI working groups could also consider assessing the potential applicability of existing knowledge anddata to different technologies, for instance to LWR SMRs; some may be applicable, others not. It would
also be useful to identify data to support code verification and validation (V&V) for SMR safety assessment
applications.
The next paragraphs summarise points of discussion developed during the joint projects week regarding
research perspectives in different safety technical areas.
6. For instance, SiC cladding, TRISO-SiC composite pellets and high density fuels.

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11Perspectives in fuel safety research
Advanced fuel and reactor developments represent good opportunities for the nuclear sector but also
challenges to address all possible envisioned options. Needs for fuel safety research are expanding withplans to soon deploy near-term new fuels and claddings and, in the medium term, advanced fuels andcladdings (NEA, 2023c). To progress in the Technology and Licensing Readiness Levels (TRLs and LRLs)
of new fuels and claddings, different testing steps are usually conducted before full-scale assemblies areused in the commercial operation of nuclear power plants, starting with the determination of fundamental
properties, out-of-pile testing, in-pile testing in representative operating conditions (in material test
reactors [MTRs] or at limited scale in commercial reactors), in-pile testing in transient and/or off-normal
conditions (in MTRs), and testing in commercial reactors in real operating conditions (lead test rods or test
assemblies). The relation between the concept of TRLs and the testing stages has been discussed in (NEA,
2023c).
At the event, it was said that FIDES-II provides the right approach to supporting MTR testing but is facing a
number of challenges. The main challenge is that currently available testing capacities are not at the levelof those offered in the past, with the recent closure or unavailability of a number of MTRs (such as Halden
and MIR). Capacities in operating MTRs (such as TREAT at INL, BR2 in Belgium, LVR-15 in Czechia, and
NSRR in Japan) are limited in comparison, for example, to what Halden was offering, or in some cases
have yet to be established for representative testing. As the capacities are limited, there is a much greaterneed to plan and design the most valuable tests. Co-operation upfront with all stakeholders is important,even more so when it comes to designing experiments with limited capacities. Further, the few MTRs thatare operational are old. It was said that the CSNI WGFS and FIDES-II should identify long-term researchneeds and the next generation of MTRs, as in-pile transient testing is essential for safety assessment andlicensing process.
Establishing research priorities in the fuel safety area is all the more important with expanding needs andlimited in-pile testing capacities.
Unless there is strong co-operation between all stakeholders, including vendors and utilities, to support
the development of additional capacities, using at best complementarities between MTRs, commercial
reactors and, where relevant, out-of-pile testing, prototypic testing might not be achievable in due time
to demonstrate the safety of all envisioned near-term and advanced fuels and claddings. One additional
challenge is that not all nuclear countries are pushing to investigate near-term new fuels and advanced
fuels. Some countries have expressed the need to design long-term collaborative research (for instancefor TRISO fuel) as there would be more possibilities to collaborate with fuel developers upfront, as longas TRLs are low or intermediate. It may become more challenging when TRLs are high as, when vendors
come close to sell their materials, it becomes more challenging to exchange data due to proprietary rights.
The development of joint projects around MTRs (named JEEPS in FIDES-II) needs an operator to maintainand operate the MTR, industry to provide fuel irradiated in commercial reactors, organisations to support
projects and end-users to identify open safety issues and valorise the project results. The community
would clearly benefit from vendors and utilities co-operating to provide irradiated material with several
years of irradiation for transient testing and the related data and information. This is clearly a challenge foradvanced fuel to be used in non-LWR reactors as there are currently no commercial reactors to provide
long-term base irradiation under prototypic conditions.
It would be beneficial to have more vendors and utilities contributing to collaborative research,e.g. participating in FIDES-II, and providing material of interest for testing. Identifying material that can bemade available for testing and creating a schedule for such testing could help establish priorities.
Regarding LOCA testing, it could be beneficial to review and use at best complementarities between in-pile
testing (for instance Halden, testing planned in FIDES-II) and out-of-pile testing (for instance hot cell LOCA

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tests at Studsvik done as part of the SCIP project). Further collaboration between HALDEN, FIDES-II and
SCIP projects on LOCA with, for example, “counterpart” testing and/or common benchmarking exercises
would be beneficial to prioritise needed testing.

Perspectives in safety thermal-hydraulic research
As highlighted above, with the planned closure of a number of facilities that were involved in joint projects,
thermal-hydraulics is an area where the development of frameworks around sets of complementary
experimental facilities is seen as a proper way to address needs for both operating and future reactors.
This would consolidate collaborations and synergies between facility operators and related joint projectcommunities in the area. Actions would need to be launched to discuss how to establish such frameworks.
This was discussed at the joint ATLAS-3/ETHARINUS analytical workshop held in November 2023 inBarcelona with potentials for establishing more integrated approaches around reactor coolant system andcontainment facilities. The organisation of joint analytical workshops or benchmarks could also be envisaged
for containment research facilities around, for example, the German THAI+ and Swiss PANDA facilities.
The NEA could also foster discussions with operating agents or organise operating agents’ fora to identify
the core facilities that will be open for collaborative research in the near and longer term and the safetyissues that may be addressed in these facilities both for operating and future reactors. These reviews
would involve operating agents with facilities that are already involved in collaborative research, but also
operating agents with facilities that are planned to be open for collaboration in the near future.

The PANDA reactor
pressure vessel.
Paul Scherrer Institute,
Switzerland

Scheme of the
THAI+ facility.
Becker Technologies,
Germany

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There is also a need to agree on which generic phenomena to address as a priority. It has been
recommended to organise PIRTs in WGAMA related to LWR SMRs and eventually non-LWR reactors,
including SMRs. Phenomena such as heat removal in large water bodies by natural convection areof specific interest to address the efficiency of passive heat removal systems, which are more widely
considered in future LWR reactors, including SMRs. The thermal-hydraulics of passive safety systems
warrants further research to reach consensus on the efficiency and reliability of such systems. Modellingsuch systems is a challenge for thermal-hydraulic codes and the systems used in SMRs are not planned
to function with the same boundary conditions as for large LWRs.
Scaling still needs to be addressed, in particular for SMR applications. Although methodologies to address
scaling issues have been established, counterpart testing in complementary facilities at different scales
is irreplaceable to validate scaling approaches. Developing frameworks around sets of complementary
experimental facilities, as proposed, also offers opportunities to validate the scaling of models for small
and large reactor applications.
There is a need to assess how the extended thermal-hydraulic database established for large LWRs isapplicable to SMRs, with no operation experience in the public domain to rely on for SMRs. The NEA, andin particular the WGAMA, have taken action to review the current status of thermal-hydraulic databases,
based on experience of the containment code validation matrix CCVM (NEA, 2014). The WGAMA is leading
an activity for the harmonisation of methodologies for system thermal-hydraulics’ experimental metadata
preservation (called THEMpo), which is a precursor to developing a thermal-hydraulics database that will
be used in the future for both operating and future LWR reactors. As such a development will requirelarge resources and will be more efficiently addressed through collaboration, it has been suggested toaddress the effort in the future as a joint project with shared funding. All stakeholders in the nuclear
sector should see an interest in contributing to this effort as it would support the licensing of future LWR
reactors.

Perspectives in severe accident research
There are still immense challenges ahead related to the Fukushima Daiichi accident. International
collaboration should continue, first through the ongoing FACE project (NEA, 2023b) to inform
decommissioning and to make better use of the insights from the accident analyses for severe accident
management for operating and future reactors. With respect to that, a workshop on future research
to enhance accident management in operating and future reactors informed by Fukushima Daiichi
insights is planned for the end of September 2024. The workshop objectives are to get regulator andindustry views on the application of the Fukushima Daiichi accident insights to accident management
and to evaluate the remaining research needs in the area. Technical sessions are planned with potential
operating agents of future projects offering research capabilities for further enhancements of accident
management in operating and new reactors. The aim is to establish recommendations on future
directions for collaborative research in the area, including recommendations on needed capabilities, andto help maintain core research facilities at risk and develop new ones, as necessary, after the completionin 2024 and 2025 of seven NEA projects (ATLAS-3, ETHARINUS, QUENCH-ATF, THEMIS, ESTER, PANDA,ROSAU) related to investigations of Fukushima Daiichi issues.
Regarding severe accidents extending to core melt, modelling all phenomena in detail is known tobe very challenging. Related research involves unique facilities and a long-term built expertise, forinstance for prototypical corium, hydrogen combustion and chemistry studies of fission products(related to source term) and is costly. There is a need to focus the research in this area, considering
the remaining major gaps from the viewpoints of industry, regulators and researchers. It was said that
it is important to continue working on the demonstration of the efficiency and reliability of accident
mitigation systems in prototypic geometries and boundary conditions both for operating and future

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reactors. Investigations performed for large LWRs
and related accident scenarios are not necessarily
applicable to LWR SMRs. The demonstrationof the efficiency of approaches and systems toprevent or mitigate severe accidents in future
reactors, including SMRs, needs to be supported
on technical grounds. A stronger involvement ofreactor vendors and utilities in research supporting
the demonstration of the validity of severe accident
management approaches for new designs would
certainly increase confidence in their deployment.
There are some pending issues related to theaccident tolerance of near-term new fuels andcladdings, including so-called accident-tolerantmaterials, and of more advanced fuels. Researchin this area should continue beyond the current
QUENCH-ATF project, which addresses accidenttolerant claddings.

Test facility for ROSAU corium melts spreading tests.
Argonne National Laboratory (ANL), United States

There is a need to preserve beyond 2024 capabilities developed for corium and source term
investigations, e.g. through the ROSAU, THEMIS and ESTER projects, to alleviate uncertainties related
to the ability to cool and isolate degraded fuel-containing material and keep radioactive releases to theenvironment under appropriate limits. This is key for demonstrating that accident management measuresand emergency planning are appropriate for future reactors, including for SMRs. However, it is also
required to design an effective approach to prioritise the needs for future reactors, possibly throughdedicated PIRTS and associated validation matrices, and to get more support from industry.
Finally, it was suggested that new activities be considered to assess the benefits of using AI and machinelearning (ML) techniques to increase the effectiveness of accident analyses.

CHIP experimental facility to study fission product transport and deposition in the primary circuit.
IRSN, France

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Perspectives in LTO research
Ageing related to the irradiation of structural materials is planned to be investigated in the near future in
the FIDES-II framework in MTRs. The strategic objectives in this area are described in NEA (2023c). The
FIDES-II INCREASE JEEP has recently been launched to establish capabilities in the area. Research needs
for structural material ageing under irradiation are listed in NEA (2023c). There is clearly a need to prioritisesafety research needs related to LTO beyond 60 to 80 years, which is now planned in a number of countries
for operating nuclear power plants. Further, operation beyond 80 to 100 years is envisioned for future
reactors and research to establish such potentials should as well be designed. An activity has recently
been launched under the CSNI Working Group on Integrity and Ageing of Components and Structures(WGIAGE) to identify major gaps and research needs related to LTO beyond 60 years. This activity will
provide directions for collaborative research.
As a number of nuclear power plants have recently been shut down worldwide (retirement after longterm operation or closure) and are being decommissioned, unique opportunities exist for harvestingmaterial aged under actual operating conditions, including material with long operation histories of up to
30 years of full operation. Harvesting material in plants is valuable with respect to providing prototypicalmaterials (when compared to material artificially aged in laboratories) that can be used to develop ageing
management strategies to support extended reactor operation periods of 60 years and more. However,
harvesting is a costly proposition that requires the strong involvement and close co-operation of all
stakeholders (regulators, researchers, utilities and companies in charge of plant decommissioning).
The NEA SMILE joint project (NEA, 2023b) conducted by Studsvik in Sweden provides a first-of-a-kindlarge collaborative effort around aged metal material harvested in Swedish plants being decommissioned.
In Sweden, all stakeholders involved in plant decommissioning, in the harvesting of aged material andin research on harvested material work jointly for the success of the research project, with the supportof organisations from other countries. Such a project offers a unique opportunity for stakeholders in a
number of countries to discuss aspects such as the challenges related to harvesting material on-site,
performing on-site measurements, collecting historical information and data on harvested material,
calculating environmental loads on materials during their in-service life, and collecting and preparing themost prototypic samples for further characterisation and testing. It is also a unique opportunity to shareexperience and good practices and optimise characterisation and testing methods.

Studsvik pool facility for storage and inspectionof SMILE materials.
Studsvik, Sweden

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The safety community would benefit from a more integrated approach to collaborative research on
material harvested in plants in the future, extending beyond the current scope of SMILE, considering
material of interest harvested worldwide and materials other than metal (for instance concrete andelectrical cables) for the interest of a wider range of countries/organisations. SMILE’s access to a numberof reactors at various stages of decommissioning and dismantling already provides for a large stream ofsamples and test results from various source materials that are applicable to BWRs, PWRs or VVERs but
other sources of material would be beneficial to extend the knowledge base.
Conducting an exercise to compile in a library which material is currently available for collaborative
research would be of interest for the development of future joint projects proposals. The library would
include materials that can be offered for international research, with good historical records and matchingpriority needs for LTO.
At the same time, the prioritisation of research needs that have been initiated for metal components
through the US NRC-NEA International Harvesting Workshops held in 2020 and in 2022, and theidentification of target material to address priority needs, should continue with a broader participation ofinterested stakeholders.
Nuclear regulators could more clearly endorse harvesting as an important, technically-robust approach tomaterials’ characterisation for long-term operation and consider how to engage more utilities in harvesting
activities for the benefit of long-term operation and nuclear safety. Relevant standing NEA committees,
the Committee on Nuclear Regulatory Activities (CNRA) and the CSNI could engage further to promote
harvesting research activities. At this stage, there is no regulatory leverage to encourage harvesting.

Perspectives for HTO research
Key topics in this area, such as human interactions with technological evolutions (including more
automation and new plant configurations such as multi-SMR units), are investigated in the Halden HTO
project. It could be interesting to develop co-operation frameworks with external scientific communities
in sectors other than the nuclear sector. Strengthening networking could be a good way to attract moreorganisations to the Halden HTO project, to gain additional insights from experts in other sectors and to
identify other research capabilities.

Perspectives in fire researchExperience shows that fire is one of the greatest risks in nuclear facilities. Future research could
consider investigations into fire risks in nuclear power plants under decommissioning, in research anddemonstration reactors and in future reactors, including SMRs. Considering the wide range of possible
topics, with different fire sources and configurations to investigate, it is necessary to establish research
priorities in this area. As in the HTO area, it would be of interest to develop co-operation frameworks withexternal scientific communities in sectors other than the nuclear sector. Strengthening networking could
be a good way to attract more organisations to fire research projects, to gain additional insights fromexperts in other sectors and to identify other research capabilities.

Perspectives for event database projects
Databases compiling international operating experience (e.g. CODAP, FIRE, ICDE [NEA, 2023b]) should
be continued under the NEA as they provide high value data and information to the community. Suchprojects usually face the challenge that utilities may be reluctant to share data widely.
Increasing the membership of event database projects, with a larger participation by utilities, would be
beneficial to the safety community.

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References
NEA (2023a), NEA website, “NEA Nuclear Safety Research Joint Projects Week: Success Stories andOpportunities for Future Developments”, www.oecd-nea.org/jcms/pl_72839 (accessed 27 November 2023).
NEA (2023b), NEA website, “NEA Nuclear Safety Research Joint Projects”, www.oecd-nea.org/jcms/
pl_72332 (accessed 27 November 2023).
NEA (2023c), FIDES-II Strategic Plan, www.oecd-nea.org/jcms/390976_Media/strategic-plan-final-2023.
NEA (2023d), NEA website, “NEA Nuclear Education, Skills and Technology (NEST) framework”, www.oecdnea.org/jcms/pl_21786 (accessed 27 November 2023).
NEA (2023e), NEA website, “NEA Data Bank”, www.oecd-nea.org/jcms/rni_6525 (accessed 27 November2023).
NEA (2023f), CSNI Status Report and Perspectives, Advances in the Analysis and Management of Accidents
and Future Challenges, NEA N°7658, OECD Publishing, Paris, www.oecd-nea.org/jcms/pl_86410.
NEA (2023g), The NEA Small Modular Reactor Dashboard, NEA N°7650, OECD Publishing, Paris, www.
oecd-nea.org/jcms/pl_78743.
NEA (2023h), CSNI Technical Opinion Paper N°21, Research Recommendations to Support the Safe
Deployment of Small Modular Reactors, NEA N°7660, OECD Publishing, Paris, www.oecd-nea.org/jcms/
pl_85956.
NEA (2022), Progress in reactivity-initiated accident research, www.oecd-nea.org/jcms/pl_76140 (accessed
27 November 2023).
NEA (2021), Nuclear Safety Research Support Facilities for Existing and Advanced Reactors: 2021 Update,
NEA N° 7565, OECD Publishing, Paris, www.oecd-nea.org/jcms/pl_60542.
NEA (2014), Containment Code Validation Matrix, OECD Publishing, Paris, www.oecd-nea.org/jcms/pl_19413.

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NEA publications and information
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offers free downloads of hundreds of technical and policy-oriented reports.
An NEA monthly electronic bulletin is distributed free of charge to subscribers, providing
updates of new results, events and publications. Sign up at https://oe.cd/nea-sub.
Visit us on LinkedIn at www.linkedin.com/company/oecd-nuclear-energy-agency or follow us
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Cover photos: Dmitriy Rybin/Shutterstock; View of the ATLAS experimental loop (KAERI, Korea); High-temperature Engineering Test Reactor (Japan Atomic Energy Agency); The PANDA reactor pressure vessel (Paul Scherrer Institute, Switzerland); Studsvik pool facility forstorage and inspection of SMILE materials (Studsvik).