Fuel cooling

The Hanford N Reactor. The Hanford N reactor was built in 1964 for purposes of plutonium production during the Cold War. It used graphite as moderator, pierced by over 1000 Zircaloy 2 tubes. These pressure tubes contained slightly enriched uranium fuel cooled by high temperature light water. The reactor also provided 800 MWe to the Washington PubHc Power Supply System. This reactor was shut down in 1992 because of age and concern for safety. The similarity to the Chemobyl-type reactors played a role in the decision. 

Fuel cooling last at least 1 hr. after shutdown 4.7E-4... 

Fuel cell vehicles, 73 800-801 Fuel cell voltage equation, 72 208 Fuel cell voltages, 72 206-209 versus current densities, 72 208 Fuel cooling, in pressurized water reactors, 77 544... 

The variable operating costs include the consumption of feed + fuel, cooling water and electricity. For their evaluation, it was taken into account that in the actual economic scenario the costs of such a scheme are mainly related to those of the natural gas and of the plant thermal efficiency. The evaluation is reported in Table 9.3. 

As previously discussed, the coefficient of expansion/contraction for petroleum products is dependent upon specific gravity. As fuels cool, their volume will be reduced. 

Low levels of water, up to approximately 50 to 75 ppm, can be solubilized into most middle distillate fuel at ambient temperature without causing the fuel to appear hazy. However, as fuels cool, dissolved water becomes visible as haze. Conversely, as fuels are heated, water haze disappears. 

At low temperatures, the wax in most distillate fuels can cause severe problems with fuel pumping and filtration. As diesel fuel cools, wax begins to crystallize and become visible. The temperature at which crystallized wax becomes visible is known as the cloud point. 

The fuel sample is cooled under the prescribed conditions and, at intervals of34°F (l°C),a vacuum of200 mm water gauge is applied to draw the fuel through a fine wire mesh filter. As the fuel cools below its cloud point, increasing amounts of wax crystals will be formed. These will cause the flow rate to decrease and eventually complete plugging of the filter will occur. 

Water contamination in diesel fuel is common. When diesel fuel cools, ice crystals may form in the fuel well before the fuel reaches its pour point. These ice crystals will settle to the bottom of fuel tanks and may result in fuel filter plugging and pumpability problems. 

Table 6.3 illustrates a typical material balance of a cumene plant using Dow-Kellog technology [3], The propylene may contain up to 40% propane, but without ethylene and butylene. Beside cumene, variable amounts of LPG can be obtained as subproducts. Energy is also exported as LP steam, although it is consumed as well as other utilities (fuel, cooling water, electricity). 

Figure 8. Estimated mean dose to the HDEHP solvent in the CTH process as a function of fuel cooling time...

Utilities (steam, eiectrlciiy, fuel, cooling water, process water,etc)... 

Utilities include steam, electricity, fuel, cooling water, process water, coirqjressed air, refrigeration, and waste treatment. Utility equipment is usually located outside of the process area and may supply several processes. We may consider each utility as a product, and estimate its cost according to the procedure outlined in Table 2.1. The cost of steam, electricity, and refrigeration depends mainly on fuel costs. Local utilities may give electric power costs, and the Federal Power Commission publishes rates for all public utihties in the United States. Table 2.3 lists approximate utility rates. 

Dissolution, described in Sec. 4.4, produces an aqueous solution of uranyl nitrate, plutonium(IV) nitrate, nitric acid, small concentrations of neptunium, americium, and curium nitrates, and almost all of the nonvolatile fission products in the fuel. With fuel cooled 150 days after bumup of 33,000 MWd/MT, the fission-product concentration is around 1700 Ci/liter. The fint step in the solvent extraction portion of the Purex process is primary decontamination, in which from 99 to 99.9 percent of these fission products are separated from the uranium and plutonium. Early removal of the fission products reduces the amount of required shielding, simplifies maintenance, and facilitates later process operations by reducing solvent degradation from radiolysis. 

Radiolysis. Radiation degrades both TBP and hydrocarbon diluent in Purex systems, with formation of molecular fragments, polymers, and nitration products. The main product, however, is the same as from hydrolysis, namely, DBP. The yield of DBP in radiolysis of TBP varies somewhat with the diluent used, water content, type of radiation, and dose rate. Baumgartner and Ochsenfeld [B6] cite production of 20 to 30 mg DBP/liter in 30-min exposure of 30 v/o TBP to 0.2 Wh/liter of radiation in mixer-settlers processing fuel cooled 240 days after 33,000 MWd/MT burnup. Because the density of DBP is 1065 g/liter, the volume percent DBP was... 

Fuel in the core of the LMFBR is operated at a specific power over three times that of the LWR. During the cooling period, the speciflc power of LMFBR core fuel from radioactive decay remains about three times that of LWR fuel cooled for the same length of time. This... 

To reduce the specific power somewhat in reprocessing, it is planned to combine irradiated fuel from the LMFBR core with irradiated fuel from the LMFBR blankets in proportion to the rates at which they are discharged from the reactor. Even so, the specific power of LMFBR fuel cooled ISO days is 1.4 times that of LWR fuel cooled the same length of time. 

More complete retention of iodine, if LMFBR fuel cooling time is reduced... 

The necessity for reliable and uninterrupted cooling of irradiated LMFBR fuel can be seen from its rate of adiabatic temperature rise owing to radioactive decay. From Table 10.20, the average specific power of core fuel cooled 150 days is 0.052 W/g HM. At a nominal specific heat of 0.08 cal/(g °C) for UO2 or PUO2, the adiabatic rate of temperature rise is... 

The analyses were finished in the middle of year 2000, and show that the acceptance criteria for DBA are met. These criteria are related to the fuel cooling and radiological consequences. Now the results of analyses are in process of licensing by the regulatory body (BNSA). 

The safety function fuel cooling during transients and accidents)) is ensured by provision of sufficient coolant inventory, by coolant injection, sufficient heat transfer, by circulation of the coolant, and by provision of an ultimate heat sink. Depending on the type of transient/accident, a subset of these function or all of them may be required. Various passive systems and components are proposed in V-392 design to fulfill these functions. 

Within the variable costs category, the most significant figures are fuel, cooling and process water and consumables such as catalyst, membranes, solvent, etc. Catalyst and membranes are included among consumables because they have a lifetime in the range of three to five years, thus several replacements are required during plant lifetime. 

ICVD Light amplifier for Cherenkov light Spent fuel (cooling time <10 years) Attribute... 

The system is also designed such that, in the very unlikely event of both the primary and secondary pool walls failing, the core remains covered by lead and fuel cooling is assured. 

A secondary control area is provided, remote from the control centre, with the capability of assuring reactor shutdown, fuel cooling and plant monitoring in the event that the control centre is for any reason nonfunctional or noninhabitable. 

If all pumps are lost, fuel cooling is maintained by thermosyphoning. 

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