Analysis of control rod drop accidents postulated in the Laguna Verde power plant

In this paper, the results of the simulation of the Control Rod Drop Accident (CRDA) using the Studsvik- Scandpower Fuel Management System (FMS) are presented. The simulation conditions were selected to represent three operational conditions of the reactor core at Laguna Verde Nuclear Power Station (CLV). To avoid unnecessary symmetry considerations the full reactor core is modeled with a fuel load formed with a blend of two assembly types namely 10 x 10 and 8 x 8 arrays. Control Rod Worth was calculated for each of the inserted control rods using a representation of a realistic BWR core configuration, 444 fuel assemblies, l 09 control rods. Individual control rod withdrawals were simulated in order to identify the largest control rod worth. As part of the description of the core configuration, nuclear data banks for cold/hot conditions were generated. Likewise, the burnup and relative power distributions were calculated to resemble the operational conditions of the fifth fuel cycle of CLV unit 2. The main analysis code for this simulation, FMS RAMONA-3, provides dynamic behavior of the neutronic thermal hydraulic BWR feedback adequate for the characteristics of this accident. Furthermore, using a parameterization of core conditions the response of hot-spot fuel-clad enthalpies and temperatures were calculated. For the most-severe core condition, from the neutronics standpoint, potential fuel damage is assessed either for a hypothetical 293 isothermal core condition (fuel and moderator) or for a more realistic operational startup condition. (Author)