MYRRHA subcritical core design

The sub-critical core consists of a lattice of 183 hexagonal channels of which, in a clean core configuration (no In-Pile-Positions loaded), 60 are loaded with fuel assemblies housing 35wt% Pu-enriched MOX fuel pins arranged in a triangular lattice. The total load of heavy metal is 680 kg at the beginning of life. The numerous extra channnels allow for flexibility needed to manage MYRRHA as an experimental machine. The main core characteristics at the beginning of life are a source multiplication factor of 0.95 and a total power of about 60 MW.

Core main parameters

Parameter	Unit	Value

Proton beam energy	MeV	600
Accelerator current	mA	2.5
Proton beam heating	MW	0.85
Spallation neutron yield	n/p	15.3
Neutron source intensity	10¹⁷ m/s	2.23

Initial fuel mixture	MOX	(U-Pu)O₂
Initial (HM) fuel mass	kg	680
Initial Pu-enrichment Pu/(U+Pu)	wt%	35
Initial Pu isotope vector (238/239/240/241/242)	wt%	2.33/56.87/27.00/6.10/7.69
keff		0.9552
ks		0.9600
MF = 1/(1-ks)		25.04
Source importance		1.10

Thermal power	MW	57
Specific power	kW/kgHM	66
Peak linear power (hottest pin)	W/cm	253
Average linear power (hottest pin)	W/cm	146

Max total flux in fast core	10¹⁵ n/cm²s	3.3
Max fast (> 1 MeV) flux in fast core	10¹⁵ n/cm²s	0.5
Max fast (> 0.75 MeV) flux in fast core	10¹⁵ n/cm²s	0.7