Mandate of the
WPFC Expert Group on Liquid Metal (LM) Technology
Chair:
TBD
Members:
All NEA member countries
Date of creation:
June 2015
Date of expiration:
June 2017
Observer (International Organisation): International Atomic Energy Agency (IAEA) (By agreement)
Mandate:
Approved at the 26th meeting of the Nuclear Science Committee in June
2015 [NEA/SEN/NSC(2015)X]
Introduction
The Expert Group on Heavy Liquid Metal (HLM) technology has been active for several years. Its main
objective up to now was to issue a handbook with a collection of theoretical approaches and
experimental data in order to deliver recommendations relevant for the design of HLM nuclear systems.
Since the second version of the handbook is ready for publication, the EG has re-discussed its scope and
future related activities. In particular, as suggested by the Working Party on Scientific Issues of the Fuel
Cycle (WPFC), it has been decided to include liquid Na activities in the future work plan of the EG.
Secondly, the EG will aim to take the next step in the assessment of available data to bring it closer to
application in design, construction and licensing issues on the one hand and operation, In-Service
Inspection, handling and maintenance on the other hand. After the discussion the EG proposes to
formulate its objectives as follows.
Objectives & Scope
Under the guidance of the Working Party on Scientific Issues of the Fuel Cycle (WPFC), the expert group
will undertake activities with the goal to "translate" fundamental scientific understanding to application
in support of (1)Development of construction codes used for design (design rules), (2) Key technical issues
for licensing, (3) Recommendations for Operation, Inspection and Handling.
The topical areas and objectives of the expert group are:

Environmental conditions and factors that affect materials behaviour relevant for the structural
integrity of confinement barriers and components. These include the impact on mechanical
properties from the environment such as irradiation effects and liquid metal embrittlement as
well as environmental assisted property effects like corrosion.


The objective is to assess the environmental effects relevant for construction standards
via a fundamental understanding of materials behaviour (corrosion and mechanical
properties in the liquid metals and under irradiation). The possibility of experimental
data sharing among participants and analyses is to be investigated.
Coolant and cover gas issues. The focus is placed on issues relevant for radiological impact
assessment, operation, including maintenance, inspection and handling, etc. Topics to be
addressed are the chemistry, radiochemistry and physics of the coolant, its interaction with the
cover gas, the impact of irradiation, the influence of corrosion, transport of radionuclides in the
coolant, etc.
The objective is to answer key technical issues to address radiological impact, operation,
handling, maintenance and inspection as relevant for licensing.
Thermal-hydraulics for Liquid metals. Thermal hydraulic behaviour of the coolant is a crucial
factor in the sense that it essentially determines a large part of the environmental conditions for
materials and the cooling such as the flow distribution and mixing, temperatures distribution,
stratification and instabilities, pressure variations, coolant structure interactions, etc.:
The objective is to collect and assess experimental data in order to improve knowledge
of the environmental conditions for materials and the coolant behaviour.
Working Methods
Two taskforces (Na and HLM) will be established. To improve efficiency the taskforces will meet in
parallel. At each meeting one plenary session will be organised to discuss and compare results in order
to identify potential commonalities and synergies.
Activities
 Survey current fundamental knowledge on the effect of liquid metal environment on material
behaviour
 Assess data management requirements with regards to the type of data, type of test and access
conditions
 Compile and assess data on the effect of liquid metal environment on material behaviour
 Survey and compare existing methodologies to understand the underlying degradation
mechanisms
 Identify further R&D needs to complement experimental databases and improve the modelling
methodologies
 Generate status report on liquid metal environmental effects (on materials)
 Compile and assess data for operation, inspection, handling, and maintenance of liquid metal
reactors, with due account to operating experience feedback
 Identify keys technical issues and lessons learned for safe and reliable operation, inspection,
handling, and maintenance in support to reactor and system design and future operation.
 Compile and assess data on liquid metal thermal hydraulics (for Na the analysis will focus on
data related to environmental conditions for materials)
 Provide assessment of thermal-hydraulic experiments and identify further R&D needs to
improve knowledge of the environmental conditions for materials
 Code-to-code, code-to-experiment benchmark studies
Deliverables

State-of-the-art report on the liquid metal environmental effects on materials (2017)



Report on data management requirements for structural materials and thermal-hydraulic (2017)
Report on key technical issues and lessons learned for safe and reliable operation, inspection,
handling, maintenance, decommissioning and waste management of liquid metal cooled
reactors. (2017)
Report on liquid metal thermal hydraulics (2017)
Links
The expert group will liaise closely with other NEA working groups, especially the Expert on Innovative Structural
Materials and those operating under the guidance and the Committee on the Safety of Nuclear Installations (CSNI)
in order to ensure the respective work programmes are complementary and to provide advice and support where
required and undertake common work where appropriate.
The expert group will also work in co-operation with the IAEA Nuclear Power Technology Development Section and
in particular the Technical Working Group on Fast Reactors (TWG-FR) and NAPRO (Sodium properties and safe
operation of experimental facilities in support of the development and deployment of Sodium Cooled Fast
Reactors). Key sources of experimental data to be reviewed include (but are not limited to) output from NAPRO,
MatDB, etc.