Monte Carlo calculation of Na‐24, K‐42 and N‐16 isotopes in the coolant of VVER‐440 nuclear reactors
26th Symposium of AER on VVER Reactor Physics and Reactor Safety (2016, Helsinki, Finland)
Reactor dynamics and safety analysis
Abstract
MONTE CARLO CALCULATION OF 24NA, 42K AND 16N ISOTOPES IN THE COOLANT OF VVER-440 NUCLEAR REACTORSG. Radócz, A. Gerényi, I. SzalókiInstitute of Nuclear Techniques, Budapest University of Technology and Economics, Budapest, HungaryABSTRACTThe leaking condition of steam generators is a very important safety parameter for the commissioning of pressurized water reactors. As part of the monitoring of the operating parameters of steam generators the detection of leaking state of heat transfer tubes. The leaking state is crucial to avoid the decontamination of the secondary water circuit; therefore different monitoring systems are available to ensure the detection of the leakage of the primary coolant. Gross gamma detection systems of 16N isotope were installed by the beginning of the main steam collectors at the secondary loops. The main role of this measuring arrangement is to give warning signal when the calculated concentration of the 16N in the secondary loops reaches the limit of allowed leakage level.The revision of restrictions rules of the primary-secondary leakage in steam generators was performed in the framework of a R&D project in Paks NPP. The specific activity of the relevant isotopes (16N, 24Na, 42K) produced by neutron induced nuclear reactions in the primary coolant were determined by Monte Carlo burnup calculations for different reactor cores built from various enrichment fuel assemblies. The activities in the secondary loops caused by the primary-secondary leakage were calculated by dispersion model during normal operation. The activities calculated by MCNP6 simulation code were compared with the results of radiochemical measurements on coolant samples originated from the primary and the secondary loops to verify our model calculations. According to this comparative analysis the agreement between the measured and calculated specific activities was within the statistical errors.26th Symposium of AER on VVER Reactor Physics and Reactor Safety 44 10 – 14 October 2016, Helsinki, Finland