Fuel load patterns

Also, stability is re-evaluated when a fuel loading pattern and/or an operating plan have been established in each operating cycle. 

Power flattening approach Use of burnable absorbers Selection of fuel loading pattern ... 

Channel power measurement from quality meters, coupled with a knowledge of fuel loading pattern and appropriate physics constants, could provide a complete map of the power distribution over the core and hence values for irradia-... 

ADJUSTMENTS TO EXPERIMENTAL FUEL LOADING PATTERN SAFETY CIRCUITS CHECKS. 

The high temperatore core without the critical heat flux criterion (i.e. the MDHFR) was designed in 1998 [12]. The two-dimensiraial R-Z model of the core cannot accurately predict bum-up of fuel rods. The three-dimensional coupled neutro-nic-thermal-hydraulic core calculation was developed in 2003 [18]. It is shown in Fig. 1.9. This calculation considered the control rod pattern and fuel loading pattern [19, 20] and was similar to the core calculation for BWRs. But the finite difference code SRAC [21] was used for the three-dimensional neutronic calculation instead of a nodal code. The core design of the Super FR also adopted the three dimensional neutronic and thermal hydraulic coupled core bum-up calculation. 

K. Kamei, A. Yamaji, Y. Ishiwatari, Y. Oka and J. Liu, Fuel and Core Design of Super Light Water Reactor with Low Leakage Fuel Loading Pattern, Journal of Nuclear Science and Technology, Vol. 43(2), 129-139 (2006)... 

These calculated results imply that with an appropriate core design, suitable radial core power distributions to achieve a high outlet temperature can be obtained. The design parameters of main concern here are the fuel loading patterns, the coolant flow rate distributions (orifice designs), and the control rod patterns. 

The relative fuel rod power inside the fuel assembly can be evaluated by combining the fuel assembly bumup calculations (ASMBURN, explained in Sect. 2.3.1) with the subchannel analyses (explained in Sect. 2.5). However, in such evaluations, the fuel assembly is assumed to be isolated in an infinitely large space with reflective boundary conditions. The effects of the fuel loading patterns or control rod patterns cannot be taken into account in these calculations. 

As for the fuel loading pattern, the low leakage loading pattern (LLLP) as shown in Fig. 2.73 [21] with the in-out refueling scheme of Fig. 2.74 [22] can be adopted with the outer core downward flow cooUng. When these design options are chosen, the neutron economy becomes better compared with the out-in loading patterns... 

S.5.2 Fuel Loading Pattern for Negative Void Reactivity... 

Table 7.29 [26] shows the fuel rod design results. The fuel rod diameter and P/D are 7.0 mm and 1.16, respectively. The rod arrangements in the seed and blanket assemblies are the same as those of the 1,000 MWe class design as shown in Fig. 7.57 [26]. The fuel loading pattern and flow distribution design are shown in Fig. 7.58 [26]. The distributions of the MCST calculated by single channel analyses and subchannel analyses are shown in Fig. 7.59 [26]. The highest value is kept well below the criterion of 650°C by modifying the subchannel shapes as introduced in Sect. 7.6. The core design results are summarized in Table 7.30 [26]. Based on the reference core design, two important performances are improved in Sects. 7.8.2 and 7.8.3.

Fig. 7.58 Fuel loading pattern and flow distribution design of reference 700 MWe class Super FR. (Taken from [26] and used with permission from Atomic Energy Society of Japan)...

Fig. 8.5 An example of a fuel loading pattern (taken from ref. [17] and used with permission from French Nuclear Energy Society)...

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