MYRRHA mechanical design: The spallation loop

The confinement vessel of the spallation loop (item 9) is located beside the sub-critical core (item 8). There are several reasons for this off-centre arrangement.

First, to achieve the required neutron flux in the sub-critical core, the central hole in the compact core must be very small and therefore it offers only space for the lead-bismuth eutectic (LBE) to follow a once through top-down path.

Secondly, as it is opted for a windowless spallation target, the spallation loop circulation pumps have to be located under the level of the target free surface and there is clearly no possibility to do that in the small central channel.

Thirdly, the off-centre arrangement limits the radiation damage of all the sensitive components of the spallation loop.

Finally, due to the large diameter of the spallation loop confinement vessel, locating the latter centrally above the core would close the door for easy access to the core for (un)loading the experimental rigs, jeopardising the flexibility of MYRRHA as a research irradiation facility.

 Reactor internals