EVALUASI PARAMETER DESAIN TERMOHIDROLIKA TERAS DAN SUB KANAL PLTN AP1000 PADA KONDISI TUNAK

Abstract

Verification and validation of core thermal-hydraulics parameter design of PWR 1000 nuclear power plants have been carried out. The calculation was done using the computer code CAUDVAP, COBRA-EN and RELAP5. The input data that used for CAUDVAP code are such as vessel and core geometry data (fuel elements, bypass, core barrel and core shroud) and the total flowrate, gave output such as the core and vessel pressure drop, coolant velocity and flowrate distribution in the core. The input data used for COBRA-EN such as the fuel element geometry, linear power, the effective flowrate and the fuel element thermal properties, and gave the otput such as active core and channel pressure drop, the distribution of enthalpy, fuel temperature, cladding temperature, coolant temperature, heat flux, heat transfer coefficient and DNBR. Whereas the input data used for RELAP5 was the fuel rod geometry, heat flux and flowrate, and gave the output such as the pressure drop along the channel, the cladding temperature and coolant temperature. The calculation using CAUDVAP gave results the pressure drop along the core vessel of 271.53 kPa (deviation of -1.26%), the distribution of flowrate through the active core of 48537.9 tons/h (deviation of 0.19%), through the guide thimble and core barrel of 2944.8 ton/h (deviation of - 3.05%) and through the core shroud of 283.2 ton/h (deviation of 9.98%). The calculation results of active core pressure drop using CAUDVAP, COBRA-EN and RELAP5 were found 76.01 kPa, 73.78 kPa and 73.3 kPa, respectively. The difference was caused by the change of core lower support area to active core area were not taken into account in calculation using RELAP5 and COBRA-EN codes. The calculated results using COBRA-EN code for core thermal-hydraulics (channel analysis) showed that the maximum meat temperature revolved by 507.95 – 945.45oC, the maximum cladding surface temperature revolved by 302.15 – 338.75oC, and the minimum DNBR revolved by 2.23 – 6.07. Whereas, the hot sub channel analysis using COBRA-EN and RELAP5 codes showed that the fluid outlet temperature were 329.42oC (deviation of 1.47%) and 324.51oC (dev. -0.05%), respectively, and the maximum heat fluxes were 1634.13 kW/m2 (dev. -0.04%) and 1601.0 kW/m2 (dev. -2.06%), respectively. The overall thermal-hydraulic parameters that obtained from the calculation compared to the design data showed no significant difference, so it could be concluded that the calculation using CAUDVAP, COBRA-EN and RELAP5 codes were valid.