Page 36 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Introduction to liquid metal cooled reactors 11

Fig. 1.4 MYRRHA primary
circuit.

1.5.3.1 Introduction
MYRRHA is an innovative multipurpose fast-spectrum research reactor currently
being developed at SCK CEN. The primary coolant is lead-bismuth eutectic.
l
MYRRHA is conceived as an accelerator-driven system (ADS) but, with the removal
of the spallation target and the insertion of control and safety rods, is also able to oper-
ate in critical mode.

1.5.3.2 Description of the primary cooling system

The driver of the MYRRHA ADS is the accelerator, which provides high-energy pro-
tons to the spallation target. This, in turn, creates primary neutrons that feed the sub-
critical core. The MYRRHA accelerator is a linear accelerator able to provide a beam
with energy of 600MeV and an average beam current of 3.2mA. At the present state
of design, the core of MYRRHA consists of MOX fuel pins. Fifty-five positions in the
core can be occupied by in-pile test sections, by the spallation target (the central
position in the subcritical configuration), or by control and safety rods (in the critical
configuration). This gives a large flexibility in the choice of the most suitable position
(wrt neutron flux) for each experiment.
MYRRHA is a pool-type ADS: the reactor vessel houses all the primary system
components. The vessel is closed by the reactor cover that supports all in-vessel com-
ponents. A diaphragm inside the vessel separates the hot and cold plena and supports
the in-vessel fuel storage. As the space above the core is occupied by penetrations for