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Impact of local property variations of reactor coolant on cladding temperature distribution in supercritical water reactors

Zhong J., Antal S. P., Podowski M. Z.

Journal of Power Technologies

2014

Vol. 94, nr 5

51--60

Fluids at supercritical pressures are considered to be very promising as coolants for Generation IV reactor systems, including the supercritical water cooled reactor (SCWR), the CO2-cooled reactor (SCCO2R) and the Brayton cycle as a secondary system in sodium-cooled fast reactors. The operating conditions of such reactors allow for a significant thermodynamic efficiency increase of the respective power plants. On the other hand, several unresolved issues must still be addressed in order to develop a viable design of supercritical fluid nuclear systems. Examples include: in-core heat transfer in SCWRs, heat exchangers in the S-CO2 Brayton cycle, and flows in complex geometries of SCO2 compressors. It has been shown before that the understanding of the effect of fluid property variations on turbulence is a major factor in our ability to predict the combined fluid mechanics and heat convection in systems and components using supercritical fluids. The objective of this paper is to present the results of analysis on the effect of local multidimensional flow and heat transfer phenomena on the temperature distribution inside future SCWRs. Two proposed SCWR designs have been considered: a single-pass and a two-pass coolant flow configurations through the reactor core. It should be noted that a preliminary documentation of the results of the current work has been included in the materials of the NURETH-15 conference.

Determination of the mass fraction of 10B in boric acid by the measurement of thermal neutron flux depression

Bolewski Jr A., Ciechanowski M., Kreft A.

Nukleonika

2012

Vol. 57, No. 4

537-544

A thermal neutron absorption technique has been improved with the aid of Monte Carlo N-particle (MCNP) modelling and used for the determination of the mass fraction of 10B in boric acid. A relative standard deviation of that determination has been estimated to be below 0.12%. Owing to the good precision and simplicity, the presented technique could be helpful in nuclear plants with pressurized water reactors, where boric acid is added to the primary circuit coolant to control the chain reaction. Possible applications include the checking of the actual mass fraction of 10B in lots of boric acid delivered to nuclear power plants as well as calibration of instruments used for on-line monitoring the content of 10B in reactor coolants.