Fuel Assembly Design

The plant system of the Super LWR is a once-through direct cycle without recirculation in the core. The core flow rate is much lower than that of current 

LWRs (about 1/8 of that of a BWR with the same thermal output). The coolant enthalpy rise in the core is large and the coolant temperature and density changes are large. For inlet coolant temperature of 280°C and density of 0.8 g/cm, the average outlet coolant temperature is 500°C and density is less than 0.1 g/cm. Hence, fuel assembly design should be such that both the fuel rod cooling and neutron moderations are effectively achieved. 

From the viewpoint of effectively cooling the fuel rods with low coolant flow rate, the gap size between the fuel rods needs to be minimized to gain sufficient coolant flow velocity to increase the heat transfer coefficient. The minimum gap size is essentially limited by manufacturing capabilities of the spacers. Recently, thermal-hydraulic experiments under BWR conditions were carried out with a fuel rod gap size of around 1.0 mm [17]. Hence, the rod gap size of 1.0 mm is expected to be possible for the Super LWR fuel assembly. 

The hexagonal fuel assembly design also needs to be revised to improve the neutron economy. The neutron moderation provided by the water rods is not sufficient and the core designed with this fuel assembly is under-moderated. 

The square fuel assembly shown in Fig. 2.35 [9] is designed to overcome the problems encountered with the hexagonal fuel assembly. The design is intended to flatten the coolant outlet temperature distribution at the outlet of the assembly by using uniform subchannels and a lower local power peaking. The area of the water rods is also increased from the hexagonal fuel assembly to gain neutron moderations. 

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Hydrodynamic and structural test are being conducted to qualify the fuel assembly design. 

The pitdi of the fuel may be the same or gteat - that in CANDU, but the length of fuel bundle is the same. The fuel assembly design adopted is coming from CANDU6 fuel design tn iere in one bundle exists 37 rods of fuel, and each rod has the same outer dimensions. It is worth to mention here that the cladding thickness may be different... 

Fuel assembly design 17 X 17 XL Robust 17x17 17 X 17 XL Robust... 

Comparisons of fhe analytical models used wifh fuel assembly design details such as fuel-rod-to-fuel-rod and fuel-rod-to-fuel-assembly-channel clearances and spacer configurations have been made to ensure that the computer programs adequately represent the actual core and fuel design, and fhat design correlafions are applicable. 

The fuel assembly design is such that the moderator density reactivity coefficient of the water within the fuel channel is negative for all conditions of operation. The in-channel moderator coefficient is smallest at the cold, zero power condition. 

Fuel is standard (UO2 enriched up to 5 wt% U-235) and fuel assembly design (but... 

The fuel assembly design is shown in Fig. II-l 1. Burnable absorber rods (2) are used for axial and radial flattening of power density in the core and compensation of the reactivity margin throughout the operating life. 

The fuel assembly s cassette and suspension are joined by a thread and fixed by pins and welding. The suspension consists of a collet head and a tie tube of 50 mm diameter. The fuel assemblies are spaced by tail parts in the lower plate of the reactor removable screen and can move axially in the plate under thermal and radial expansion. The fuel assembly design includes the materials well proven in long-term operation and manufactured based on well-explored technologies, such as ... 

Fuel assembly design for VKR-MT Experimental Design Bureau OKBM, VNIIAM 2005-2006... 

The design of a core fuel assembly is shown in Fig. XVI-7. The fuel assembly design data are given in Table XVI-7. 

The core incorporates a system of control rods moving along the fuel assembly axis these form a triangular lattice of -224 mm pitch. The number of control rods and their design were selected to comply with the requirement of compensation of reactivity changes during the core lifetime. A cross section of the core with maximum number of control rods (37) is shown in Fig. XIX-13. The fuel assembly design is illustrated in Fig. XIX-14. 

Number of fissile fuel assemblies/bundles - for most reactors, the total number of fuel assemblies in the core. For RBMK and CANDU reactors this is the product of the number of pressure channels and the number of fuel assemblies per channel. For FBRs it is the number of fuel assemblies designed to maintain the fission chain reaction (heat and neutron production). 

In addition the fuel vendors are requested to improve the fuel assembly design to mitigate file problem. The remedies are the following ... 

A new design of the control rod, with approximately 30% greater weight to shorten the drop time, and a new fuel assembly design are being tested in WWER-1000 reactors. 

Fuel assembly design modifications have been implemented to mitigate fretting failure. 

The fuel rod and fuel assembly design bases and acceptance limits are described in the... 

The design and construction of an experimental fast reactor is the first engineering accomplishment of FBR development. It requires compromises with respect to core neutronics, thermohydraulics, fuel pin and fuel assembly design, materials, components... 

Related to fuel assembly design, hydrodynamic and structural tests are plarmed at two (low and high) pressure rigs... 

The fuel assembly design is that based on casing-free skeleton-structure fuel assemblies of the AFA-type, originally developed by OKBM for the VVER-1000 reactor [VII-11], Fig. VII-8. 

TABLE VIII-12. FUEL ASSEMBLY DESIGN DATA... 

The RBEC-M fuel assembly design differs essentially from designs of the traditional fast reactor subassemblies (e.g., sodium cooled reactors of the Russian BN-type) ... 

The use of wide fuel rod lattice and spacer grids allows the manufacture of a RBEC-M fuel assembly as a dismountable component, which could also facilitate implementation of the IAEA safeguards. In this case, there is an opportunity to secure all the fuel rods by measurements and to exclude the possibility of an undeclared replacement of intermediate fuel rod rows by pins with fertile materials. In the case of a non-dismountable fuel assembly design, the sensitivity of contemporary methods of measurement for nuclear materials allows measurements only of the external fuel rod rows and up to two internal fuel rod rows (if a guide tube for control in the fuel assembly center is available). 

FIG. XXIII-8. RBEC-M fuel assembly design (in the center there are tubes for CPS absorbing elements). 

Mainly due to the diversification of nuclear fuel suppliers, a call for a bid was issued by the Slovak power utility SE a.s in 1992. One of the fuel assembly designs for the VVER-440 nuclear reactor was TRICON 440, a nuclear fuel product from Siemens and FRAMATOME. The TRICON 440 fuel assembly is briefly presented in this... 

Specialized fuel assembly design for severe accident behavior (eg, sacrificial inner duct), and... 

Figure 8.10 Fuel assembly design for a reactor core with fast neutron spectrum (Oka et al.,...

An example of fuel assembly design of the Super LWR is shown in Fig. 1.13 [35]. An example Super LWR core and fuel characteristics are given in Table 1.4 [24]. The core coolant flow rate of the Super LWR is substantially lower than that of LWRs due to the high enthalpy rise in the core. The gap between fuel... 

The fuel and core design is the central issue for a nuclear power plant (NPP). This chapter describes the design concepts of the Super LWR core including the fuel rod and fuel assembly designs. The core characteristics are explained together with the design method, criteria, and the research and development subjects to comprehensively develop these concepts. 

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