Application of the Dynamic Rod Worth Measurement Method on WWER

The dynamic rod worth measurement method, which is used widely for PWR with square geometry lattices, is applied on WWER type reactor with hexagonal geometry lattices. RTNP code is developed to calculate the static spatial factors (SSF) and the dynamic spatial factors (DSF) through simulating the 3D space-time neutron dynamics and the response of excore detector during the measurement process. The improved quasi-static method is used for temporal discretization. The time-dependent shape equation is then transferred to a fixed source problem through backward Euler formula. And Multi-group Monte Carlo method is used to solve this fixed source problem. Four tests on Tianwan nuclear power plant (NPP) units 1&2 have been done since 2015. The measured results agree well with the predicted values. It takes about half hour per bank and 5 hours to measure all banks worth. The conventional boron dilution was used for rod worth measurement of Tianwan NPP units 1&2. It took at least 2 hours per bank and produced lots of boron wastes. The boron dilution has been replaced with this method for Tianwan NPP units 1&2.