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WP2: Design of the Fast Spectrum Transmutation Experimental Facility (FASTEF) in sub-critical & critical mode (ANSALDO)

Objectives

After the analysis resulting from WP1, a definition of specification and design choices will be available as an input to this work package.
Taking into account the outcome of WP1, the design of the FASTEF operating in sub-critical mode is further detailed and complemented starting from the available MYRRHA/XT-ADS design studied in the framework of the FP6 IP_EUROTRANS project.
The consequences of FASTEF working in critical mode on the MYRRHA/XT-ADS design and on the overall safety and operational parameters will be implemented. Working in both operation modes will be incorporated from the very beginning.
Furthermore, progress of some specific accelerator design related issues will be made with regard to the status in MYRRHA/XT-ADS.
And finally, a clear definition and conceptual design of a limited set of experimental devices for the FASTEF (working in sub-critical or in critical mode) will be performed.

Description of work

This work-package will concentrate on the primary and secondary system (including DHR), spallation loop, experimental devices, safety, beam line transport and coupling of the accelerator with the reactor.
The starting point for CDT will be the design provided at the end of IP-EUROTRANS, where the design of a fast-spectrum facility, working in sub-critical mode coupled to a proton accelerator, has been well studied. In IP-EUROTRANS, the conceptual design of MYRRHA Draft-2 was taken as starting point and it was critically reviewed which led to some significant conceptual design modifications. Dedicated parts (the primary system, the core and the windowless target) were then further detailed to obtain an advanced design. Other components (the secondary system, the DHR by RVACS, the experimental devices, the in-vessel fuel manipulators, the in-vessel inspection & repair manipulators, reactor vessels & cover, the in-vessel LBE conditioning system and spallation loop) will only reach a conceptual design level at the end of IP-EUROTRANS. The purpose of this work package is to obtain an advanced level of design for all these components at the end of the project given the updated definition of specification and design choices resulting from WP1.
This work package is divided into five tasks, covering the FASTEF design (T2.1 and T2.2), safety analysis (T2.3), its coupling with the accelerator (T2.4) and the design of experimental devices (T2.5).

T 2.1. Review and extension of the MYRRHA/XT-ADS design to FASTEF in sub-critical mode (ANSALDO, SCK•CEN, ENEA, KIT, ITN, OTL, SENER,AREVA NP S.A.S., CIEMAT,CRS4,NRG)
The objective of this task is to obtain a coherent advanced design for the different components to be studied in this task, i.e.:

• core and core support structure;
• primary system;
• secondary system & DHR system;
• spallation target & loop & its integration in the reactor;
• in-vessel fuel manipulators;
• reactor vessels and cover;
• the lead-bismuth conditioning & control system;
• the in-service-inspection & repair systems.

Where for the core, the primary system and the spallation target already an advanced design will be present at the end of IP-EUROTRANS, other components will not have reached the same level. The aim is to bring all other main components design to the same advanced level.
Based on the outcome of WP1, a number of design option modifications will first be implemented. It is clear that the design options implemented in this task will need to be coherent with the global set of definition of specifications from WP1. Of course further (probably minor) adaptations of design options for all systems and components (including the core and primary system) will be implemented, based on:

• feedback from T2.2, T2.3, T2.4 and T2.5;
• updated available data on material characteristics (e.g. oxidation layer on HX's tubes, appropriate materials or coatings for impellers, influence of toughness of irradiated structure material on primary system temperature and consequently on secondary operating pressure, in-LBE bearing technologies, …);
• updated design rules (e.g. for LBE impeller pumps);
• remote handling compatibility (by employing the in IP-EUROTRANS introduced “Remote Handling Catalogue”);
• adequately selected codes and standards.

Thereby, a list or catalogue of unknown but nevertheless important material properties (toughness, creep, swelling, strength, …after irradiation) will be generated, which will be used as a guide for the selection of additional R&D activities.
At the end of the CDT, a coherent advanced design for these components will be obtained in order to be able to draw up the technical specifications that would enable the suppliers to make a quotation and a detailed engineering.

T 2.2. Design changes for the FASTEF to operate in a critical mode (ENEA, SCK•CEN, FZD, KIT, CIEMAT, ANSALDO, SENER, AREVA NP S.A.S., NRG)
In this task, the configuration of FASTEF in critical mode, as defined in WP1-T1.2 and WP1-T1.3, is studied. Neutronic calculations have to show if critical core loadings in the actual design with and without the spallation source are possible. The necessary control systems (e.g. control rods) and safety systems in accordance with the licensing needs (safety rods and a complementary system) have to be developed. The core design and the excess reactivity must permit a certain irradiation cycle duration. Further, an optimal reload strategy for the driver fuel has to be defined taking into account a maximal fuel burn-up, number of reshuffling operations, flux peaking factors and required performances of the experimental devices. In addition, the core power distribution and thermal-hydraulic limits have to be determined to prevent fuel element damage and the necessary mechanical changes must be implemented. From these neutronic, thermo-hydraulic and mechanical studies follows an optimal reactor design that will be further analysed. Some important studies are:

• the reactivity effects of this reactor without experimental rigs to check the controllability of this design;
• the evaluation of the neutron flux performance to check the ability of this design to meet the requirements of a modern fast spectrum material testing reactor;
• in relation to T2.3 the evaluation of accidental situations for the safety analysis;
• the performance of the core loaded with experiments defined in T2.5;

The implementation of the remarks of the mentioned studies will result in a usable core design for the critical fast-spectrum experimental facility.
Main design changes of the primary system configuration (e.g. the reactor cover plate), resulting from the suppression of the spallation loop, resulting from WP1 will be assessed and integrated.

T 2.3. Safety analysis of FASTEF in critical & sub-critical mode (KIT, SCK•CEN, ENEA, KIT, FZD, ANSALDO, AREVA NP S.A.S., UPM,UPV)
The MYRRHA/XT-ADS safety analysis, undertaken in the framework of IP_EUROTRANS, will be used as starting point for further analysis in sub-critical mode. A more thorough analysis of some Design-Based Conditions (DBC) accidents like sub-assembly blockages and heat exchanger tube ruptures will be performed. The safety analysis will also include Design Extended Conditions (DEC) accidents. Wherever reasonably feasible a probabilistic safety assessment will be undertaken with particular attention to human error aspects. However, for a LBE or lead cooled system estimates on a probabilistic basis become difficult due to the poor data base. In so far more qualitative approaches as the Defence-in-Depth strategy will be followed. The safety studies should also be extended to an evaluation of the radiological safety and a safety analysis of the confinement building.

A significant part of the 'sub-critical' safety analysis remains valid for the critical mode. To some degree working in critical mode would even simplify some aspects in the safety analysis performed for the ADS, since the spallation loop and the coupling with the accelerator will be removed. On the other hand, all events including reactivity variations and/or reactivity control around criticality should be analysed and might have an important impact on some design choices.

Therefore the task will consist in the identification of the main differences that the conversion from FASTEF as ADS to the critical system introduces from the safety point of view and will result in updating the list of initiating events to be considered for the safety analysis for the critical FASTEF. In addition, unintended events related to the operation of the test rig inserts will have a different importance once you operate the facility in a sub-critical and a critical mode and will thus be pointed out.

For the safety analysis of FASTEF working in critical mode, one can take benefit of the outcomes from the FP6 ELSY project. In this way, a preliminary safety analysis of FASTEF working in critical mode will be obtained without going to the same level of detailed analysis as for the case of subcritical mode operation.

T 2.4. Progress accelerator design related issues (CNRS, SCK•CEN, OTL, EA, ITN, SENER)
The purpose of this task within the work package would be to iterate between the calculations of accelerator shielding, the mechanical design of the beam line entry, the beam line path within the reactor building and the reactor roof height. Separate items exist already for the former FP5 PDS-XADS project (conceptual designs of reactor building and beam line) and the currently running FP6 EUROTRANS project (more advanced designs of reactor building, plant layout and beam line), but the integration between the separate items could not be totally performed yet.
Further, the design of the beam line must be optimised to ensure the accelerator and beam reliability.
The design of the beam dump located at the end of the accelerator building is to be looked at in more detail. An analysis has to be made on how the generated heat of nearly 2 MWth can be evacuated efficiently taking into account the different constraints in the reactor hall. Based on this analysis, a design of the beam dump and its integration in the overall plant lay-out will be made.

T 2.5. Design of experimental devices for both modes (SCK•CEN, ENEA, CIEMAT,OTL)
Goal of the experimental devices are:

• MA transmutation;
• radioisotope production;
• test and qualify material and fuel for future reactors (GenIV, fusion);
• Si-doping

The objectives of this task are:

• to set up specifications (irradiation conditions as T, coolant, flow, spectrum, fluence, ...) for and list of relevant In-Pile Sections (IPS) (the complexity of experimental devices may vary from simple sample holders directly immersed in the reactor coolant, to dedicated loops);
• the conceptual design of selected IPS;
• to give feedback to reactor design (T2.1& T2.2) in terms of the reactivity effects of these experiments on the core and the safety implications of these experiments on the reactor.
The CDT should keep in mind that future needs might differ from actually supposed; therefore the design should be as flexible as possible.

Deliverables

D2.1 FASTEF advanced design (ANSALDO) (M36)
D2.2 FASTEF design changes to operate in critical mode (ENEA) (M36)
D2.3 FASTEF safety analysis - critical & sub-critical mode (KIT) (M36)
D2.4 Accelerator design related issues (CNRS) (M24)
D2.5 Conceptual design of experimental devices for FASTEF (SCK•CEN) (M24)