Statistical Thermal Design

The goal of the Super LWR is to achieve safe, reliable, and economical operation. Since the coolant temperature and its density change greatly within the Super LWR fuel assemblies, it is important to effectively evaluate the thermal-hydraulic performance and all associated uncertainties, given that this performance is a critical component of the overall core design. 

The impact of various thermal conditions for a typical core is shown in Fig. 2.85. The design tasks can be divided into three main parts consideration of the power distribution, the engineering uncertainty, and the transient uncertainty [26]. The power distribution considers the effects of the radial, axial and, local heat flux distributions. The transient uncertainty takes into account the uncertainties in 

Various methods have been developed and utilized successfully to evaluate and combine the engineering uncertainties for most types of nuclear reactors other than the Super LWR. These methods treat the uncertainties by using values directly or by using dimensionless factors and they combine all the uncertainties by different methods, including the deterministic, semistatistical, and statistical methods. 

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Single channel thermal hydraulics (SPROD), 3D coupled core neutronic/thermal-hydraulic (SRAC-SPROD), Coupled subchannel analysis, Statistical thermal design method. Fuel rod behavior (FEMAXI-6), Data base of heat transfer coefficients of supercritical water (Oka-Koshizuka correlation)... 

J. Yang, Y. Oka, J. Liu, Y. Ishiwatari and A. Yamaji, Development on Statistical Thermal Design Procedure for Super LWR, Proc. Global 2005, Tsukuba, Japan, October 9-13, 2005 Paper 555 (2005)... 

F. 2.87 Statistical thermal design procedure for the Super LWR. (Taken from [27] and used with permission liom Atomic Energy Society of Japan)... 

The statistical thermal design procedure for the Super LWR was developed by using a purely statistical Monte Carlo method to effectively evaluate the engineering uncertainty of the Super LWR. 

The relatively large temperature rises calculated by the subchannel analyses and statistical thermal design shown that these analyses are essential in determining the maximum peak cladding temperature of the Super LWR core. 

Statistical thermal design +32°C from the nominal peak... 

Statistical thermal design uncertainty was evaluated by a Monte Carlo sampling technique combined with the subchannel analysis code. The engineering imcer-tainty of the Super LWR is evaluated as 31.88°C based oti the Monte Carlo Statistical Thermal Design Procedure. 

MCSTDP Monte Carlo Statistical Thermal Design Procedure... 

J. Roheyns, E. Parmentier and G. Peelers, Application of a Statistical Thermal Design Procedure to Evaluate the PWR DNBR Safety Analysis Limits, Proc. ICONE 9, Nice, Erance, April 8-12, 2001, ICONE-9091 (2001)... 

Mass flux and enthalpy distribution Influence of coolant channel heterogeneity Influence of local power Statistical thermal design uncertainty... 

In order to investigate fuel rod integrity during normal operation and abnormal conditiOTis, the MCST is evaluated in consideration of the engineering uncertainties by using an approach similar to the Monte Carlo Statistical Thermal Design Procedure (MCSTDP) introduced in Chap. 2. 

Table 7.20 Nominal conditions of hot assemblies in statistical thermal design procedure of the Super FR...

Table 7.27 Results of statistical thermal design and comparison with RTDP results. (Taken from [1])...

Chapter 2 covers design and analysis of the core and fuel. It includes core and fuel design, coupled neutronic and thermal hydraulic core calculations, subchannel analysis, statistical thermal design methods, fuel rod design, and fuel rod behavior and integrity during transients. 

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