Jules Horowitz takes shape

28 January 2015



The Jules Horowitz materials testing reactor is set to become a major scientific hub for nuclear research, radioisotope production and training. By Xavier Bravo and Gilles Bignan.


Over the last 50 years materials testing reactors have provided essential support for nuclear power programmes within the European Union. However, the majority of these facilities will reach 50 years old by 2020, leading to the increased probability of shutdowns. MTRs are key for the development and qualification of materials and fuels. They are used to optimise and demonstrate the safe operations of existing power reactors and to support future reactor design. In this context, the Jules Horowitz Reactor (JHR) has been identified on the European Commission's Research Infrastructures Roadmap since 2008.

The 100 MWt JHR material testing reactor is currently under construction at the CEA Cadarache research centre in the south of France.
Planned for completion by the end of this decade, JHR will offer modern irradiation experimental capabilities for the study of material and fuel behaviour under irradiation.

JHR is designed to provide high neutron flux (notably twice as much the French MTR Osiris, which is in operation today), to support advanced modelling and simulation, and to reproduce the environmental conditions (pressure, temperature, flux, coolant chemistry) of both light water reactors and future reactor systems.

As a modern research infrastructure, JHR will also contribute to the development of expertise and know-how, and to the training of the next generation of scientists and operators. JHR will also be used for medical isotope production.

Consortium approach

JHR, as a future international user facility, is funded and steered by an international consortium, which includes industry (utilities and fuel vendors) as well as public bodies (R&D centres, technical support organisations, and regulators).

The French Atomic Energy and Alternatives Energies Commission (CEA) is the owner and the operator of the nuclear facility, with all associated liabilities.

JHR consortium members are the owners of 'guaranteed access rights' to reactor experimental capacity. These rights are allocated based on the amount of financial commitment to the construction, and come with a proportional voting right on the consortium governing board.
A consortium member can use their access rights to implement proprietary R&D programmes and/or for participating in joint international programmes that are also open to nonmembers.

As of mid 2014, JHR consortium members included 11 organisations plus the European Commission under a specific status. JHR consortium membership is open to new members until completion of the reactor.

Facility description

The JHR facility comprises a reactor building and a nuclear auxiliary building. The reactor building has a diameter of 37 m and is constructed from reinforced concrete. The nuclear auxiliary building includes three storage pools for spent fuel and irradiated experimental devices as well as four hot cells for preparation, conditioning of experiments and nondestructive examination of irradiated samples. A transfer channel between the reactor building and the nuclear auxiliary building allows spent fuels and experimental devices to be moved between the two facilities.

Other supporting infrastructure includes buildings for cooling and for ventilation, two emergency diesel generator buildings, and a 'cold workshop' for assembly and testing of experimental devices before they enter the nuclear island.

When operating at full capacity of 100 MWt the JHR will produce a thermal neutron flux of up to 5.5x10^14 n/cm².s to study current and innovative nuclear fuels. The fast neutron flux in the core will range from to 5.5x10^14 n/cm².s for E > 1MeV up to 10^15 n/cm².s for E> 0.1 MeV.

For materials ageing testing the facility operates a maximum dose rate of 16 dpa/year - this is eight times the typical PWR flux on internal material.

JHR has six displacement systems for adjusting the fissile power and to study power transients. It has the ability to support power transients up to 600 W/cm for fuel limit and clad failure studies.

The JHR is designed to perform about 20 experiments simultaneously. It is expected to operate for ten cycles a year, representing about 260 equivalent full power days.

Notably, the reactor design incorporates improved online monitoring capabilities, including a fission product laboratory directly coupled to the experimental fuel sample under irradiation.

Construction update

AREVA group subsidiary AREVA-TA is responsible for engineering the JHR facility. It is also responsible for supervising the construction site and supply of key reactor components.

More than 20 other suppliers are involved in the JHR construction, through the supply of civil works, mechanics, heating, ventilation, air-conditioning and electrical components.

Preparation of the site for the Jules Horowitz reactor began in Spring 2007. Construction of the reactor building containment was initiated in July 2011, followed by the reactor cavity in December 2011. The reactor-building dome was installed in December 2013, marking a major milestone in the project.

Civil works are currently more than 80% complete and work on the electromechanical tasks is underway. Recent construction highlights have included the completion of polar crane tests, as well as the installation of the support structure for the pool liner.

The next key milestones will be the installation of primary circuit components in the reactor building, and the completion of the hot cell structures within the nuclear auxiliaries building.

In addition to physical construction, CEA and its partners are preparing the first experimental loops.

  • The MADISON loop for fuel investigation under normal situation (for PWR, BWR and VVER-type reactors)
  • The ADELINE loop for power transient studies allowing clad failure for up-to-limit situations (with support from EDF)
  • The LORELEI loop for safety loss of coolant accident studies for accidental scenarios (in collaboration with IAEC-Israel)
  • The MICA capsules-CALIPSO loop for material investigation under high fast neutron flux and high dpa rate
  • The MELODIE device for online bi-axial constraint analysis on material (in collaboration with VTT-Finland)
  • The CLOE loop for material corrosion studies under constraint (in collaboration with DAE India).

Apart from MICA capsules-CALIPSO loop (currently undergoing design optimisation), all these devices have entered or are well into the detailed design phase with an objective to go for manufacturing beyond detailed design.

The MELODIE loop has already been manufactured and will undergo qualification tests in the Osiris MTR by 2015.

Post-Fukushima safety reassessment

Following the Fukushima-Daiichi accident (March 2011), the French nuclear regulator asked CEA to perform complementary safety assessments at JHR. The CSAs evaluated the capacity of French nuclear facilities to withstand extreme situations beyond design basis assumptions with a particular focus on prevention of 'cliff edge' effects.

The complementary safety assessments essentially confirmed the sound design bases of the newly built JHR. A few selected needs for extra equipment were identified, and, as an answer to French nuclear regulator requirements, CEA proposed a set of 'hardened core' measures for JHR.

These included an ultimate recirculation pump for the reactor main cooling circuit; pipes and valves for ultimate pool water supply from outside the containment building; ultimate valve actuation on some ventilation lines; installation of dedicated sensors to independently measure pressure and radiation levels in the containment building and an ultimate power source for the equipment mentioned above.

This set of 'hardened core' measures was assessed by the technical support organisation IRSN and reviewed by the French nuclear regulator's standing advisory committee in April 2013.

International R&D

Parallel to the construction of the reactor, the preparation of an international community around JHR is continuing. This is an important topic because, as already indicated, building and gathering strong international support for MTR experiments is key for R&D in the nuclear energy field.
According to the consortium agreement, JHR aims to become an international user facility (similar to the OECD/Halden Reactor Project) for multinational projects and proprietary experiments.

The JHR consortium has setup an annual scientific seminar and three working groups (focused on fuel, material and technology) to identify R&D topics of common interests and to prepare the first international joint R&D programmes. These programmes are expected to address fuel and materials issues that are key for operating reactors and future nuclear plants. The fourth seminar was held in April 2014 and gathered about 80 participants.

The working groups identified the following R&D topics:

  • LWR fuel testing under normal, incidental and accidental conditions (including investigation of fuel element thermal-mechanical behaviour, fuel-to-cladding chemical interaction, fission gas and volatile fission products release and associated source term, and transient swelling).
  • Dose accumulation in low-alloyed steels for reactor pressure vessel and new cladding studies for accident tolerance.

Training in the field

The JHR experiment team at Cadarache is already welcoming scientists and engineers from various organisations and institutes.These secondees are integrated within the project team for a limited period (typically one year) to work on various projects, which can range from development of experimental devices (in the fields of neutron physics or thermohydraulics) to supporting the future reactor operator through instrumentation & control or safety analysis work.

The secondment programme is an important element for countries willing to invest in nuclear technology, and helps them to create and sustain key competencies.

It also provides a means of nuclear education 'in the field,' filling the gap between academic education and industrial training. This is fully compliant with the recent IAEA initiative to establish an International Centre based on Research Reactors (ICERR) in order to facilitate access to the reactors fleet worldwide and to harmonize operation and safety.

To summarise, JHR remains on track for completion by the end of the decade and open to international collaboration.


About the authors

Xavier Bravo is JHR Project leader and Gilles Bignan (gilles.bignan@cea.fr) is the User Facility Interface Manager at the French Atomic Energy and Alternatives Energies Commission (CEA)- Nuclear Energy Directorate Cadarache and Saclay Research Centres - France

Jules Horowitz reactor dome installation in December 2013 Jules Horowitz reactor dome installation in December 2013
Jules Horowitz reactor pool internal structures in April 2014 Jules Horowitz reactor pool internal structures in April 2014
Jules Horowitz auxiliary unit building in mid 2014 Jules Horowitz auxiliary unit building in mid 2014
Jules Horowitz reactor building in mid 2014 Jules Horowitz reactor building in mid 2014


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