International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators

4-8 May 2009, Vienna

Analyses of Transients for 400 MWth-Class EFIT Accelerator Driven Transmuter with the SIMMER–III Code

P. Liu¹, X.N. Chen¹, F. Gabrielli¹, M. Flad¹, W. Maschek¹, A. Rineiski¹, S. Wang¹, K. Morita², M.M. Rahman², and Y. Ege²

¹Forschungszentrum Karlsruhe GmbH, Institute for Nuclear and Energy Technologies (IKET), Karlsruhe, Germany
²Department of Applied Quantum Physics & Nuclear Engineering, Kyushu University Fukuoka, Japan

Corresponding Author: ping.liu@iket.fzk.de

European R&D for ADS design and fuel development is driven in the 6^th FP of the EU by the EUROTRANS Programme. In EUROTRANS, two ADS design routes are followed, the XT–ADS
and the EFIT. The XT–ADS is designed to provide the experimental demonstration of transmutation in an Accelerator Driven System. The longer-term EFIT development, the European Facility for Industrial Transmutation, aims at a generic conceptual design of a full transmuter. The EUROTRANS Domain DM1 (DESIGN) developed the conceptual reference design of the EFIT, a 400 MW_th ADT, loaded with a CERCER U-free fuel with an MgO matrix. For the cladding, the 9Cr1MoVNb T91 steel has been chosen. The core coolant is pure lead with inlet and outlet temperatures of 400 and 480°C. For the EFIT clad and structural materials, a surface treatment with a GESA type technique is foreseen to prevent the build-up of thermal conductivity reducing oxidation layers. The windowless target for the 800 MeV proton beam also contains pure lead. The EFIT concept is to be optimized towards: a good transmutation efficiency, high burnup, low reactivity swing, low power peaking, adequate subcriticality, reasonable beam requirements and a high level of safety. In the current paper the safety analyses performed with the SIMMER-III code are reported and discussed. In the framework of the SIMMER analyses additional calculations have performed with ERANOS, DANTSYS, and C4PTRAIN to check safety coefficients, burn-up behavior and decay heat.

Basically two different safety areas have been analyzed. Firstly, protected and unprotected transients which are initiated by a mismatch of power-to-flow or resulting from a beam disturbance or overpower situation. Secondly a stream generator tube rupture (SGTR) accident has been investigated with its potential impact on the core region. From the safety point of view all ADTs with a high load of Minor Actinides are characterized with a “zero” Doppler fuel feedback, a high void worth for lead and a very small beta-effective. In addition the massive Helium production from the transmutation process leads to high pressure potentials in the plena. Although the boiling point of Pb coolant is high, voiding may take place via two routes. It can be triggered either by a pin failure with gas release from the plena or the dragging in of steam into the core after a SGTR accident.

The transient scenarios presented here are mostly unprotected (beam-on scenarios): spurious beam trip (BT), unprotected transient overpower (UTOP), unprotected loss of flow (ULOF) and unprotected blockage accident (UBA). As the high temperature and transient behavior of the MgO based fuel and the T91 cladding is connected with large uncertainties, the unprotected accidents with the potential of fuel failure and gas release deserve special attention. Extensive investigations have been performed for the UBA as it represents a route into pin failure and a blockage accident has been reported in the past in a HLM cooled submarine. As fuel and clad might be swept out of the core region after an UBA the release of material and possible re-freezing or deposition on structures was also investigated experimentally, simultaneously validating the SIMMER code.

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