GUARDYAN (GPU Assisted Reactor Dynamic Analysis) is a continuous energy Monte Carlo neutron transport code being developed at the institute. It targets to solve time-dependent problems related to fission reactors with the main focus on simulating and analyzing short transients. The key idea of GUARDYAN is a massively parallel execution structure making use of advanced programming possibilities available on CUDA (Compute Unified Device Architecture) enabled GPUs (Graphics Processing Units).

Even for simplified problems the solution diverges unless sophisticated variance reduction techniques are used. Novel variance reduction techniques have been developed to handle the problem.

The code has been validated against simulation results of MCNP with success using about half a million data point. Transient simulation was compared to measurements at the Training Reactor.

Main publications:

B. Molnar, G. Tolnai, D. Legrady: "A GPU based direct Monte Carlo simulation of time dependence in nuclear reactors", Annals of Nuclear Energy 132 (2019) 46–63 DOI

B. Molnar, G. Tolnai, D. Legrady: "Variance reduction and optimization strategies in a biased Woodcock particle tracking framework", Nuclear Science and Engineering 190 (2018) 56-72 ​DOI

The code website can be found here. Further related publications are available here.