Bismuth inventory

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... 

Economic optimization. The selection of parameters for a reference design must be based upon economics. An economic optimization was accomplished by computing relative energy costs based on those variable costs which depend upon the parameters selected. The costs which are dependent upon the nuclear parameters are (1) bismuth inventory, (2) fuel inventory, (3) fuel burnup, (4) thorium inventory, (5) thorium burnup, (6) reactor core and vessel, and (7) chemical processing costs. 

Bismuth inventory charges. The bismuth inventory is determined by the primar>- s stem volume external to the reactor vessel, the volume of bis-nuitli ill the core, the volume of bismuth external to the core but inside the reactor ves.sel, and the holdup external to the reactor system. The primary system external to the reactor vessel is made up of throe heat-exchanger loops containing a total volume of 1640 ft . The volume of bismuth in the core is... 

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. 

Bismuth Inventory in Reactor Vessel External to Core... 

The density of bismuth is taken as 9.83 g/cc, and the price is as.sumed to be 2.25/lb. Bismuth is a nondepreciating capital investment with a 12% annual amortization rate. The annual bismuth inventory charges may be represented by the equation... 

Fuel costs. The fuel costs as presented in this report include (1) bismuth inventory, (2) fuel inventory, (.3) fuel burnup, (4) thorium... 

Overall, however, the release of refractory fission products from Windscale was less than the release of volatile elements by two or three orders of magnitude, relative to the inventories in the reactor fuel (Table 2.4). Alpha activity on the stack filters and environmental filters was mainly 210Po, derived from the bismuth irradiated in the isotope channels (Crouch Swainbank, 1958 Crooks et al., 1959). The 210Po/137Cs ratio on the environmental filters was about 0.2, with no significant change with distance, suggesting that both activities were carried on the same fume particles. 

The world-wide production of Bi is -4000 t/a at a cost of 12 per kg, its explored reserves as of 1972 being -160 000 tons (coolant inventory of IGW(e) reactor is 15.000 tons). Respective data for lead is 4 xlO t/a and -100x10 tons. Bismuth is expensive, its resources being limited. It is possible that its use could be confined to a limited number of reactors. 

Inventory of lead or lead-bismuth from the decommissioned reactor can be used as the coolant of a new reactor. 

The LMFR readily lends itself to a wide variety of designs and arrangements. The concepts proposed to date may be classified according to type as being internally or externally cooled and either compact or open arrangement of cycle. Such classification has been brought about in an attempt to present designs which minimize bismuth and uranium inventories. 

Since the cost of bismuth as a primary coolant is between ) ,000,000 and. 84,000,000, the inventory charges are a significant fraction of the total fuel costs. One case was calculated using lead as a coolant in order to compare the increase in inventory charges due to the use of bismuth with the loss in conversion ratio due to the absorptions in the lead. 

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%. 

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