THORIUM AS AN ENERGY SOURCE - Opportunities for Norway ...

Nuclear Reactors for Thorium
material selection for the internal core structures, the spallation target and fuel cladding
the sub-critical core design
obtaining nuclear data for achieving a reliable design
The need for an experimental ADS in Europe and its objectives: In order to develop and test the
technology for commercial deployment of accelerator driven systems, an experimental facility is
required. This facility should in pilot scale prove the feasibility of operating a sub-critical reactor
driven by a high intensity accelerator. It is needed to demonstrate the long-term applicability of
corrosion control in lead-bismuth cooled reactors. It should further provide the fast neutron
environment necessary for developing minor actinide based transmutation fuels. The availability
of a fast neutron spectrum will be mandatory for development of more irradiation resistant
structural materials that can increase the operational lifetime of commercial ADS or new
generation critical reactors to be deployed in the future.
The experimental ADS can also be conceived with less demanding working condition in terms of
facility rate availability (50 to 70 %) as compared to the one that would be envisaged for an
industrial transmuter (70 to 90 %). Such a reasonable, but nevertheless acceptable, availability
rate would allow accommodating the beam trips expected for the first-of-kind machine to be
deployed. This will then allow improving the accelerator performance progressively towards the
performances to be achieved for the industrial ADS.
The domain of interest of such experiment will be to show a reliable operation of the system, from
start-up to nominal power level, up to shutdown, in presence of thermal reactor feedback effects.
The presence of control rods in the system will allow verifying different modes of operation during
fuel irradiation and the determination and monitoring of reactivity levels with “ad-hoc”
techniques. The joint cooling of the target and of the sub-critical core will be demonstrated,
together with the solution of some practical engineering problems of generic interest for an ADS,
such as the configuration of the beam ingress into the core.
The possibility to run the experiment at different levels of sub-criticality and power ratings
(realised e.g. with appropriate fuel loading patterns), will allow to explore experimentally the
transition from an “external” source-dominated regime to a core thermal feedback-dominated
regime. This transition is relevant, in particular to understand the dynamic behaviour of an ADS,
which, in the future full scale demonstrations of transmutation, could have both a very low βeff
and very low Doppler reactivity effect.
One important project conducted at the Belgian Nuclear Research Centre (SCK-CEN) is the
MYRRHA project. It aims to serve as a basis for the European experimental demonstration of
transmutation in ADS and to provide protons and neutrons for various R&D applications. It
consists of a proton accelerator delivering a 600 MeV, 2.5 mA (or 350 MeV, 5 mA) proton beam to
a liquid Pb-Bi spallation target that in turn couples to a Pb-Bi cooled, subcritical fast nuclear
core. The project started in 1997 and the aim is to put MYRRHA in service in 2016 - 2018.
Additional information: [127], [128], [129], [130], [131], [132] and [133].
5.4.4.10 Roadmap for an Experimental ADS in Europe
The roadmap presented in April 2001 by the Extended (actually European) Technical Working
Group (ETWG): “A European Roadmap for Developing Accelerator Driven Systems for Nuclear
Waste Incineration”, assumes that a major financial investment made as early as 2003, which was
the scheduled year of the beginning of the FP6 (255 M€ over 4 years for R&D, engineering for the
Detailed Preliminary-Design and the beginning of construction). This financial investment has
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