Calculating V-1000 Core Model With Serpent 2: HEXTRAN Code Sequence

Continuous-energy Monte Carlo reactor physics code Serpent 2 was used to model the critical steady state conditions measured in V-1000 zero-power critical facility at the present day NRC “Kurchatov Institute”, Moscow in 1990-1992. The Serpent 2 results were compared to measurements and Serpent 2
was used to generate group constants and albedo boundary conditions for two-group nodal diffusion reactor dynamics code HEXTRAN. The results of a HEXTRAN calculation of the steady state were compared to Serpent 2. Initial 3D Serpent 2 calculation produced an effective multiplication factor of k_eff = 1.01480 for the critical steady state. Subsequent calculations showed that adding the stainless steel spacer grids of the V-1000 core to the Serpent 2 model lowered this overestimation by 660 pcm. Furthermore, it was found that the soluble boron concentration of the steady state has the potential to shift the effective multiplication factor by up to 577 pcm while still staying within its experimental accuracy. When the soluble boron concentration was set to
the highest allowable concentration within its experimental accuracy and the spacer grids were taken into account, Serpent 2 produced a k_eff = 1.00243 for the critical steady state. HEXTRAN produced an effective multiplication factor within 521 pcm of the corresponding full core Serpent 2 calculation. There was a tilt in the HEXTRAN solution relative to Serpent 2 such that the relative powers in the middle of the core were significantly underestimated.