Fuel inventory systems

The honeycomb critical assembly is a universal split table machine containing a 1.83-m ( ft>cubical matrix of 76-mm (3 in.)-square aluminum tub It is deagned to serve as a flexible system for initial mbckup studies for basic critical parameter investigations. Fuel inventory consists of various Assile species such as 330 kg of O.OS-mm-thick U(93) foils with widths and lengths appropriate to the aluminum matrix tubes. Control and safety rods utilize sections of the core or reflector materials for their flmction and major disassembly is provided by the movable section of the table. Honeycomb is presently stacked with a UOrMo (core). Be (reflector) mockup of a space powa reactor. 

Besides the thermal environmental impact by wasted heat production in the thermal cycle and dissipation in the internal power circulation system, the power density and the configuration will also have an influence on the environmentally relevant parameters fuel inventory and activation. 

The function of the fission product confinement system is to minimize the release of fission paroducts to the environs during all credible accidents These credible accidents range from the partial oxidation of a single fuel element to meltdown of the significant part of the reactor fuel Inventory ... 

Life cycle assessment of SOFC technology is still uncommon due to the relatively early stage in technical development. However, several studies have been performed since the end of the 1990s. Since there is a lack of standard commercial equipment that could serve as a basis and reference point for analysis, LCA studies mostly refer to hypothetical concepts and/or extrapolate from laboratory and early market prototypes to commercial units. While the first studies had only little access to operation data at aU (for the fuel cell system itself but also for production processes), the main effort was set in the assessment of inventory data using assumptions, simplifications, and correlations [79, 80]. The main outcomes of these studies were the identification of weak points and the setting of benchmarks for further development. With more information about fuel cells available today and a simultaneous advancement in LCA methodology, the studies became more reliable and detailed, regarding system description [81] as well as the assessment of environmental impacts coimected with inputs and outputs [82]. Especially the extensive data of these two studies found their way to commercial databases for LCA [83] and thereby became available to LCA practitioners. In 2005, the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU)... 

Rolls-Royce Fuel Cell Systems Limited (2008) Life cycle inventory analysis of the IP-SOFC stack concept. Real-SOFC Project, Realising reliable, durable energy efficient and cost effective SOFC systems. Integrated EU project nnder the 6th framework programme... 

The spent fuel storage system are to be designed so that prevention of excessive decrease of cooling water inventory in the storage system and proper leakage detection shall be possible. 

Keoleian GA, Spatari S, Beal RT, Stephens RD, Williams RE. Application of hfe cycle inventory analysis to fuel tank system design. Int J Life Cycle Assess 1998 3(1) 18-28. 

The fertile-material concentrations and reactor diameters have essentially the same effects on coiu crsion ratio and fuel inventory for one-region uraiiiurn-plutonium. systems as they do for thorium breeder sy.stems however, since the rj s for and are lower than for it is more... 

The open-cycle arrangement may also be employed in an internally cooled LMFR to reduce fuel inventory, but it introduces those problems peculiar to internally cooled systems. 

Bisnmth inventory. The primary system volumes for PB/Pt = 0.HS and 0.50 are ha. ed on a six-loop capsule design. Each loop contains a bismuth inventory of 245 ft . If 50% of the power is generated in the blanket, three loops contain blanket slurry and three contain U-Bi core solution. If niie-third of the power originates in the blanket, two loops are devoted to the l>lanket. system and four to the core system. If only 10% of the total I)uu er is generated in the blanket, a three-loop design is assumed for the cure sy-rem. and two small loops of 125 ft each are used for the blanket. The real tor holdup has been estimated from the reactor drawing in Fig. 24-4 Fuel inventory volumes are summarized in Table 24-3. 

Ilf optimization. The bismuth inventory is slightly greater for the ca.se of Pb Pt = 0.10 than for the other two cases, because of the added primary. system volume. Fuel inventory charges are not very sensitive to... 

Xo additional holdup is included to account for temperature expansion (luring startup, fuel feed system, and other sources of bismuth inventory. Tlie assumption used throughout this study that the volume of bismuth is etiual to the volume of slurry accounts for an additional 3 to 10% excess bismuth due to the Th02 content of the slurry. 

The buildup of fission products and uranium isotopes as a function of time was calculated to determine the fuel concentration necessary for criticality after various time periods of operation. Since the solubility of uranium in bismuth is limited to 6560 ppm at 965°F, the lowest fuel temperature in the LMF-GCR, the reactor fuel must be replaced or processed after the poisons build up to such a level that this solubility limit is exceeded by criticality requirements. With the total fuel inventory in the system equal to 1.2 times the fuel in the core, the fuel lifetime will be 220 megawatt-t ears. This corresponds to an operating period of 4.8 years with a plant utilization factor of 80%. 

Safety. A large inventory of radioactive fission products is present in any reactor fuel where the reactor has been operated for times on the order of months. In steady state, radioactive decay heat amounts to about 5% of fission heat, and continues after a reactor is shut down. If cooling is not provided, decay heat can melt fuel rods, causing release of the contents. Protection against a loss-of-coolant accident (LOCA), eg, a primary coolant pipe break, is required. Power reactors have an emergency core cooling system (ECCS) that comes into play upon initiation of a LOCA. 

A first attempt to estimate the potential consequences from severe LWRs accidents was the BNL report WASH-740 (1957). The authors of WASH-740, to overcome the lack of information and methods, estimated "Hazard States based on the core state, radioactive inventory, fuel cladding, reactor coolant system, and containment conditions. 

Fuel cannot be completely eliminated, though the inventory of combustible fuels can be kept to a minimum. Oil and gas will be present in any production facility, and either an oil spill or escaping gas can provide the fuel needed. Escaping gas can result from rupture, opening a closed system, or gas that is normally vented. The amount of fuel present can be minimized by preventing oil spills and gas leaks. 

For ESD isolation valves (i.e., EIVs) a fail safe mode is normally defined as fail closed in order to prevent the continued flow of fuel to the incident. Blowdown or depressurization valves would be specified as fail open to allow inventories to be disposed of during an incident. Special circumstances may require the use of a foil steady valve for operational or performance reasons. These applications are usually at isolation valves at components, i.e., individual vessels, pumps, etc., where a backup EIV is provided at the battery limits that is specified as fail closed. The fail safe mode can be defined by the action that is taken when the ESD system is activated. Since the function of the ESD system is to place the facility in its safest mode, by definition the ESD activation mode is the foil safe mode. 

We also can generally state that major temperature control problems can and often do occur when the reactions are both exothermic and irreversible. These systems are not inherently self-regulatory because an increase in temperature increases the reaction rate, which increases temperature even further. The potential for reactor runaways is particularly high if the reactor is operating at a low level of conversion. The large inventory of reactant provides plenty of fuel for reaction runaway. These concepts will be quantitatively studied in later chapters. 

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