MYRRHA accelerator

The accelerator acts as the engine of the ADS system. It provides the high energy protons that are used in the spallation target to create neutrons that in their turn feed the subcritical core. In the current reference design the proton beam energy and intensity are 600 MeV and 2.5 mA respectively. Both cyclotron and linear accelerator types are capable of providing these beams.

The proton beam delivered by the accelerator has to fulfill a number of possibly interlinked conditions. Some of these are rather obvious, others less so. Solving the accelerator problem comes down to selecting and designing a device that delivers a beam meeting all requirements in the most efficient way. This will also aid the initial selection of the accelerator type.

The conditions are :

• The right beam energy:
  The optimal beam energy is a compromise between different competing considerations.
• Sufficient beam intensity:
  The amount of neutrons produced in the spallation source is directly proportional to the beam intensity. Once the beam energy is fixed, intensity is matched to obtain the required neutron yield.
• Correct beam shape and profile:
  The beam profile must be optimised to yield an optimal influence on the spallation target.
• Maximum reliability and availability:
  Short (1 s) interruptions of the proton beam have a very negative effect on the ADS system because of the thermal shocks they initiate.
• Construction costs and operation costs:
  Obviously, since funding is always limited, the construction of the accelerator, including shielding should be as cost effective as possible. Operation costs are also an issue, in particular if an accelerator with a megawatt beam power is involved.

Based on the considerations above, a linear accelerator has been chosen for MYRRHA.