MYRRHA engineering

Rationale for the MYRRHA design characteristics

MYRRHA is designed as a flexible fast spectrum irradiation facility. This means that a fast neutron spectrum is present at every location in the reactor and that in every fuel assembly position a dedicated experimental fuel assembly can be loaded. In this way, the entire reactor volume offers possibilities of loading experimental fuel assemblies in conditions similar to the reactor conditions, being a fast neutron spectrum, and in contact with the flowing liquid lead-bismuth at reactor operating temperatures.

As BR2, MYRRHA will be able to host at least 8 in-pile sections (IPS) (representing a total volume of 8 x 3700 cm³) with a core loading pattern optimised to obtain the most appropriate irradiation conditions in the IPS. In these usually double-walled IPS, a different coolant (Na, NaK, He, H_²O) can be present with temperature and pressure conditions optimised for the experimental fuel/material loaded in the IPS.

The IPS are usually instrumented to follow the irradiation conditions that have been optimised in the IPS by choosing the appropriate coolant (stagnant or loop-type) and a temperature independent from the MYRRHA environment. The content of some of these IPS can be loaded/unloaded during reactor operation. The presence of these IPS makes MYRRHA not only a fast spectrum irradiation facility, but also a very flexible one.