Hot Cell Laboratory

The JRC Hot Cell Laboratory is situated at the JRC Karlsruhe site, within the Unit Safety of the nuclear fuel cycle.

This unique infrastructure is an open access facility serving Europe and other international stakeholders and is essential for the implementation of the JRC’s programmes on nuclear safety and radioactive waste management. 

The facility

The laboratory consists of 24 shielded rooms known as “Hot Cells” where highly radioactive materials can be received, handled and examined with supporting techniques like microscopy and radionuclide assay methods.

There is a variety of hot cells, each equipped for different stages of nuclear research. This includes the hot cell where whole four-meter-long fuel rods can be handled, and which is equipped for non-destructive testing and cutting. Other hot cells contain specialised tools and equipment to analyse irradiated nuclear fuel and to study how radioactive waste behaves during long-term underground storage. In addition, dedicated contamination cells are used to safely manage waste, clean equipment, and refurbish internal components.

Read more on JRC Hot Cells

Activities and capabilities

The JRC Hot Cell Laboratory provides comprehensive post‑irradiation examination of nuclear fuels, evaluates the mechanical and aqueous behaviour of spent fuel, and investigates the properties of nuclear accident materials. Using a range of advanced destructive and non‑destructive techniques, the facility delivers data that support the full life‑cycle management of nuclear materials.

Post irradiation examination of nuclear fuel

Nuclear fuel changes during its entire life cycle, including during operation. To contribute to the safety assessment of the use of nuclear fuel, it is essential to understand its behaviour under different irradiation (reactor) conditions. For this purpose, the JRC Hot Cell Laboratory performs post-irradiation examination (PIE) on different types of nuclear fuel. 

Tools and techniques used during PIE include:

• Non-destructive testing (NDT)
• Fine microstructure examination
• Micro-mechanical properties testing 
• Micro-chemical analysis  
• Testing of coated gas-cooled reactor fuel 
• High-spatial-resolution isotope tracking
• Ultra-trace elemental and isotopic analysis 
• Advanced aerosol deposit analysis 

To perform these tests, our laboratories are equipped with a.o. SEM-EDX (scanning electron microscopy - energy-dispersive X-ray spectroscopy), TEM (transmission electron microscopy), FIB (focused ion beam), EPMA (electron probe microanalysis), µ-XRF (X Ray fluorescence spectrometry),  HR-ICP-MS (high-resolution inductively coupled plasma mass spectrometry) coupled with automated flow injection, a special annealing furnace (KÜFA, cold finger apparatus), a revaporisation facility, a high-temperature µ-indentation device, a μ-gamma scanning bench, alpha spectrometry, gamma spectrometry and liquid scintillation counting.

These studies allow to gain information about the behaviour and integrity of irradiated nuclear fuel on different levels, from complete fuel rod scale to microscopic and even molecular scale. 

Spent fuel characterisation in view of interim storage, transport and final disposal

The long-term safety of spent nuclear fuel management depends on understanding how irradiated fuel, cladding and fuel-rod systems evolve during interim storage, transport and final disposal. The JRC Hot Cell Laboratory investigates both the mechanical integrity of spent-fuel rods and the aqueous stability of irradiated fuel under conditions relevant to these different stages.

Mechanical behaviour and fuel-rod integrity

Tests are performed on irradiated fuel-rod segments, typically 250–300 mm long, to determine their response to bending and impact loads and to investigate fuel fragmentation, cladding failure and the potential release of fuel particles.

Current and developing capabilities include:

• Three-point bending tests on irradiated fuel-rod segments 
• Impact testing with high-speed imaging 
• Burst and creep testing of irradiated cladding 
• Ring-compression and small-punch testing 
• High-temperature mechanical testing 
• Nanoindentation and microscale tensile testing 
• Characterisation of released fuel fragments and particles 

These investigations generate experimental data needed to assess fuel-rod integrity and retrievability during prolonged storage, subsequent handling, and transport.

Aqueous stability of spent nuclear fuel

A scenario relevant to the long-term safety assessment of geological repositories is the behaviour of spent nuclear fuel when it comes into contact with ground water. Experiments at the JRC Hot Cell laboratory determine how fuel characteristics and environmental conditions influence alteration of the fuel matrix, and the possible release of various radionuclides.

Long-term experiments are conducted under static and dynamic conditions, as the experimental systems allow control and monitoring of temperature, pressure, gas composition and solution chemistry. 

The principal experimental capabilities include:

• Autoclave experiments under controlled oxidising or reducing atmospheres 
• Static and flow-through leaching systems 
• Online measurement of redox potential and other solution parameters 
• Analysis of uranium, plutonium, fission products and activation products in leachates 
• Investigation of the instant or fast release fraction of safety-relevant radionuclides 
• Measurement of long-term fuel-matrix dissolution rates 
• Surface and microstructural characterisation before and after leaching 
• Studies of conventional UO₂, high-burn-up fuel, MOX fuel and advanced fuel compositions 

Leachates are analysed using high-resolution ICP-MS and complementary radiometric techniques, while changes in the fuel surface and microstructure are examined by Raman spectroscopy, optical and electron microscopy, EPMA and other microanalytical methods.

The resulting data support the development and validation of mechanistic models and provide input for the safety assessments used by radioactive-waste management organisations.

Severe accident materials, corium and fuel-febris research

During severe nuclear accidents radioactive materials are generated, including corium, damaged fuel, fuel debris and deposited aerosols. The research performed on these materials at the JRC Hot Cell Laboratory improves understanding of accident progression, radionuclide mobilisation and the long-term behaviour of these accident-derived materials, for example when they come in contact with sea water or groundwater. 

Current research activities include:

• Chemical, mineralogical and microstructural characterisation of corium and fuel debris 
• Investigation of radionuclide release during corrosion and leaching 
• Comparison of oxidised and reduced severe-accident materials 
• Studies under fresh-water, borated-water, seawater and repository-relevant conditions 
• Surface-phase identification using Raman spectroscopy 
• Analysis of uranium, plutonium, caesium and other radionuclides released into solution 
• Characterisation of accident-generated particles and deposited aerosols
• Development of experimental systems for radioactive aerosol generation and transport studies 
• Participation in international round-robin exercises and benchmark programmes 

The laboratory combines destructive and non-destructive examination techniques to determine what happens to radionuclides in real and representative severe-accident materials. Investigations range from bulk-scale characterisation to micrometer- and nanometer-scale analyses using optical microscopy, SEM, EPMA, EBSD (electron backscatter diffraction), FIB, TEM, Raman spectroscopy and complementary radiometric and mass-spectrometric methods. The newest addition to the laboratory will be the implementation of RADES (RAdioactive Dispersion event Experimental Setup) in the Hot Cells environment, which enables to determine produced aerosols during a laser flash and the measurement of melting point.

This work supports severe-accident management, source-term assessment, post-accident remediation and the development of strategies for the retrieval, treatment, storage and eventual disposal of accident-derived radioactive materials.