Calculation of VVER-1000 reactor scaling factor for inference of core barrel motion

Highlights: • Scaling factors are calculated for the beginning of cycle (BOC) of VVER-1000 reactor using the direct and adjoint methods. • Space and energy dependent power density in core region is obtained from MCNP code. • Linearity assumption of relative detector response for small CBM is investigated. • It is shown that the direct method result is reliable for determining the CBM. - Abstract: To quantify the core barrel motion (CBM) in a pressurized water reactor, a scaling factor can be calculated to convert the Root Mean Square (RMS) value of the ex-core signals (%) to the core barrel motion amplitude (mil) (Thompson et al., 1980). In the current paper, a scaling factor is calculated using the direct and adjoint methods for a typical VVER-1000 reactor. The scaling factor is calculated using the perturbed parameters that result from CBM. The results show that the calculated scaling factors are not the same in one and two-dimensional modeling, and strongly depend on the ex-core detector location. The linearity assumption of relative detector response versus the small displacement of core barrel is investigated as well