Unused Fuel

The gas turbine compressor is the means of heating the SOFC to ion conduction operating temperature, a considerable advantage, amplified in Section 4.1.9. 

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Congress has decided that reprocessing will not be practiced in this country so that we will not be in the plutonium production business. This seems like a safe thing to do since this action will minimize terrorism threats. Reprocessing generates chemi cal wastes but greatly reduces the volume of the highly radioactive waste. It also isolates plutonium and unused fuel for possible use as new fuel. 

Our body, like any machine, requires a source of fuel. We talk, we breathe, we eat, and sometimes we even think. All of it requires energy, and this we get from burning food. Not in a furnace, but in our cells. As the food burns — that is, as it converts to carbon dioxide and water — it releases energy to maintain body temperature and to power all of our activities. If, on the one hand, we eat but aren t very active, the unused fuel piles up, and we put on weight. If, on the other hand, we don t take in enough fuel, the body switches to burning its stored supplies, and we lose weight. Pretty simple. 

Appendix A shows that for equilibrium fuel cells, high-temperature operation offers no advantage, but indeed a theoretical disadvantage. However, in a practical non-equilibrium set-up, where unused fuel and unconsumed oxygen are features and these have to be combusted in a gas turbine, the high-temperature fuel cell is likely to be at an advantage. Further discussion appears on this point in Chapters 4 and 5, in respect of the SOFC and the MCFC. The PEFC (Chapter 6) must, for... 

Siemens Westinghouse is advanced in its pursuit of gas turbine integration. High-temperature depleted air and unused fuel from the fuel cell cannot be discarded, and are best used in a gas turbine, as outlined in Baozhen Li etal. (2001), the Siemens patent for a Single Module Pressurised Fuel Cell Turbine Generator System (pp. 974-979). The effect... 

Heated fuel and water are reformed and isothermally oxidised at the MCFC anode. The unused fuel and depleted air from the anode are burnt with added air in a catalytic oxidiser, the output of which heats the cathode and supplies it with oxygen. The cathode exhaust heats the incoming fuel and water in a heat exchanger. The latter exhausts to desired users, for example steam generation or thermal process. 

In Figure A.6, an indication is given of the nature of a practical plant for the isothermal oxidation of methane from natural gas. The heavy hydrocarbons are removed from the natural gas and sent to the combustion chamber of a gas turbine, to be burnt in air with the hot mixed exhaust from the fuel cell of unused fuel, steam and carbon dioxide. 

Neutralization number (ASTM D-974, IP 139 IP 182) is a measure of the inorganic and total acidity of the unused fuel and indicates its tendency to corrode metals with which it may come into contact. 

Some of the stringent requirements on the storage pools are eff < 0.95 (even if unused fuel elements are introduced), earthquake safety, no possible water loss, water level automatically kept constant, adequate leakage and radiation monitoring systems, water tenqjerature < 65°C, acceptably low radiation level in working areas, etc. 

A fuel mixture comprising 600.0 g of NH4CIO4 and 400.0 g of A1 is used in a test of a laboratory scale mock-up of a shuttle engine. When the engine stops burning, some unused fuel remains. What substance is this unburned fuel, and what mass of it should be found ... 

Another less commonly applied method is to use some type of device, such as a membrane separator, that will separate the CO2 from the anode exit gas and will allow it to be transferred to the cathode inlet gas (a CO2 transfer device ). The advantage of this method is that any unused fuel gas can be recycled to the anode inlet or used for other purposes. Another alternative to both these methods is that the CO2 could be supplied from an external source, and this may be appropriate where a ready supply of CO2 is available. 

TEPCo has since replaced the cover over the reactor building and reinforced suspect areas. It has finished the process of removing the spent fuel assemblies from the Unit 4 s spent fuel pool, along with 202 unused fuel assemblies. The spent fuel assemblies have been removed from the spent fuel pool and are now located in a large commonly shared spent fuel pool on the Fukushima Daiichi site. The removal... 

In all commercial fuel cells, provision must be made for residual fuel effluent recovery. Fuel utilization is not 100% due to concentration polarization limitation on performance discussed in Chapters 3 and 4, so that unused fuel in the anode exhaust stream is always present and must be actively recycled, utilized, or converted prior to exhaust to the environment. Potential effluent management schemes include the use of recycling pumps, condensers (for Uquid fuel), secondary burners, catalytic converters, or dead-end anode designs. 

Reactant Storage, Delivery, and Recycling This includes the pumps and blowers required to supply the stack with prescribed flow rates of fuel and oxidizer and to recycle unused fuel back into the anode inlet stream. Typically only fuel storage and recycling are needed as air is used as the oxidant. 

Fuel cell mass balance requires that the sum of all mass inputs must be equal to the sum of all mass outputs. The inputs are the flows of fuel and oxidant plus water vapor present in those gases. The outputs are the flows of unused fuel and oxidant, plus water vapor present in those gases, plus any liquid water present in either fuel or oxidant exhaust. 

Another possibility to improve fuel utilisation using a simple planar stack design is a series-parallel gas flow system that utilises two different stacks, with the gas flowing through a standard Ni-YSZ based cell stack first, with a reasonable, but safe utilisation, followed by an oxide based ceU stack to extract the last of the unused fuel from the exhaust. 

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