Description of condition at one stuck rod HTR-10 viewed from the shutdown margin value

Neutronic simulation of HTR-10 has been performed with MVP (Monte Carlo Visual Program) code by JAERI. This code is chosen because it is the most simple to draw up reactor geometry inputs. The MVP code library data is JENDL-3.3, which is filled on the reactor geometry that has been arranged. HTR-10 is a type of a pebble bed reactor, containing uranium oxide spherical ball (UO₂) with 17 % enrichment, covered by a layer of TRISO. HTR-10 is modeled using graphite as a moderator and reflector material, helium gas as a coolant material, and control rod is a boron carbide material. HTR-10 is operated at a power of 10 MW with average temperature of helium inlet and outlet is 250 °C and 700 °C, the diameter of core is 1.8 m and the height of core is 1.97 m, containing about 27000 pebbles. This simulation is focused on the variation of control rod position, which at one stuck rod of the 10 control rods is found on the HTR-10. The simulation result is is k_eff value, so it can be calculated the value of reactivity, ρ and shutdown margin (SDM). The simulation result show that the OSR is obtained by positive reactivity and SDM $1.9215 ± 0.0009. Since the minimum value of SDM is $0.7, according the theoretical of HTR-10 is safe to be shutdown OSR case. (author)