Fuel element, design

The last two characteristics are primarily due to the unique HTGR fuel element design and the rather innocuous environment of the core. Table I Illustrates this point with a comparison of HTGR effluents with those from Bolling Water Reactors (BWR) and Pressurized Water Reactors (PWR). 

In the subsequent sections, more attention will be given to the considerations affecting the choice of the coolant, moderator, and fuel element design for gas-cooled reactors. Developments in plant equipment will be discussed in greater detail. The choice of the fuel cycle and its effect on economics and the utilization of nuclear resources will be discussed. Finally, future trends in gas-cooled reactor designs will be indicated. 

There are, of course, other requirements on fuel element design. In general, the following considerations are important in the design ... 

Fig. 9. Effect of fuel exposure lifetime on HTGR conversion ratio for two fuel element designs.

Fuel The fuel and fuel element design is derived from that of the MHGR, and illustrated in Figure 3. The TRISO fuel is protected from the lead by the graphite fuel element structure. However, there is no chemical reaction between molten lead and the silica-carbide coating of the TRISO fuel particles, and the solubility of silica-carbide in lead is negligible. 

The fuel element design also imposes some constrains ... 

The core is composed of 109 hexagonal fiiel assemblies (FAs) of 238 mm width across flats with active fuel length of 2.5 m. The core equivalent diameter is 2.7 m. This results in low core power density (36 MW/m ). The fuel element design is based on the well developed technology of VVER-fuel. 

MacDonald, R.D. and Hastings, I.J. 1984. Graphite Disk UO2 Fuel Elements Designed for Extended Burnups at High Powers, Atomic Energy of Canada Limited Report, AECL-8814, November. 

Each cluster of the control group of control rods replaces 91 fuel elements in the core. Each cluster of the shutdown group of control rods replaces 19 fuel elements in the core. The fuel element design for a first-of-a-kind BN GT is similar to that of the BN-600 reactor [XVm-11], including the materials used. 

The fuel pins themselves are now full length rather than segmented, prepressurized with helium to minimize the compressive stresses in the cladding and reduce creep induced by the coolant pressure. Allowance for the buildup of gaseous fission products takes the form of an end plenum. As a result of the improvements in fuel element design, the standard burn-up is 33,000 MW d/tonne for the PWR and 27,000 MW d/tonne for the BWR. The limit to the desirable burn-up level is now set by economic rather than material limitation considerations. 

The fuel element design is similar to that used in the WER reactors. The fuel element cladding has a 9.1 mm outer diameter and a 7.73 mm inner diameter. The fuel cladding material is E-110 or E-635 zirconium alloy. 

Development work on materials, manufacture, fuel pin design and fuel element design and associated Irradiation testing are described. 

Future trends in fuel element design and materials are considered and details are given of the extensive experimental fuel programme Included In the first core of the Wlnfrlth SGHWR and the longer term developments on which work has started. 

Main details of a natural SGHWR fuel element design... 

The production costs of a MZFR type fuel element which also apply to the fuel of the Atucha reactor amount at the present to approximately 55 of the total costs, with the balance of 4-5 for uranium and Zlrcaloy. It is thought that a significant reduction In future production costs is possible by rationalized manufacturing methods and standardized test procedures which go hand in hand with Increased production capacities. The uranium costs may be assumed to remain constant in the period under review. In the long run it is therefore advisable to choose that fuel element design which will benefit most by the expected production cost reduction. 

The aforementioned requirements for reactor and fuel element design shall also be maintained in the event of changes in fuel management strategy or in operational states over the operational lifetime of the plant. 

A series of five different fuel element designs proposed for EBR-II have been analyzed from the standpoint of thermal performance. 

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