CALCULATION OF THE TRANSITION FUNCTIONS OF SELF-POWERED DETECTORS FOR VVER-1000 BY MEANS OF THE MCU-PD AND TVS-M CODES
29th Symposium of AER on VVER Reactor Physics and Reactor Safety (2019, Energoland, Mochovce NPP, Slovakia)
reactor physics experiments and code validation
For successful licensing and safe passage of pilot operation of a new type of fuel in the core of an operating VVER-1000 reactor, it is necessary to carry out a preliminary validation of design codes that are routinely used for developing fuel cycles, core safety analysis and calculating maintenance of power unit operation.
Validation matrix of the design codes includes the problem of calculating transition functions of self-powered neutron detector (SPND). The transition function of SPND is a relation between SPND current and average power of six fuel rods that surround SPND in the FA. Incore detectors are the main part of incore neutron flux monitoring system. They allow to estimate power density in the core.
The article presents the main results of validation of the TVS-M spectral code in relation to the calculation of the transition functions of SPND for VVER-1000 with the new type of fuel. Validation of TVS-M was carried out by comparing with the solutions of modeling tests obtained by means of the MCU-PD Monte-Carlo code. A set of modeling tests was developed, including more than 800 cases. Several types of fuel assemblies with different fuel enrichment, burnable absorber content and SPND location were considered. For each type of FA, various states were simulated, differing in fuel burnup (in the range from 0 to 70 MWd/kgHM), coolant temperature, the presence of control rods and other parameters. A comparative analysis of the results obtained by means of the TVS-M and MCU-PD codes is carried out. In addition, the effects of accounting of heterogeneous structure of SPND and rhodium burnup in the emitter on the transition function were evaluated.