Cold Water Addition

33ie time when cold water addition would produce a maximum reactivity increase is when the reactor is at equilibrium. Theairerage coolant density at operating conditions is about 0.82 gm/cm3 and the average temperature is about 230 C. An Increase to near unity density and near river tenperature in the coolant by the substitution of cold emergency cooling vater will produce a theoretical full-pile reactivity increase of about 3.6 per cent. 

Results of deialled studies on how fast cold water can be injected into the reactor have shown that in the case of a primary coolant system dusp cold raw water may start to reach the reactor in approximately 30 seconds and may fill all coolant channels in an additional 30 seconds. Thus the reactivity ranp during the time cold water is replacing the normal coolant in the reactor is about 0.12 per cent per second. 

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Humidification of the gas stream is the preferred method of keeping the filter bed moist. Gas moisture is usually added to the incoming gas stream downstream of the particulate removal APC equipment by either water sprays or steam. Adding moisture directly to the top of the bed in order to maintain filter media moisture is not recommended since this can result in (I) locahzed drying of the substrate, and (2) cold water addition will reduce the ac tivity of the microorganisms until the water becomes warmed to the steady-state filter ed temperature. 

Suppose a constant 362,000 Btu/h of heat is transferred into the jacket from the reactor, starting at time equal zero when the jacket is at 145 T. How long will it take the jacket water to reach 99 F if the cold water addition rate is constant at 416 pounds per minute ... 

Criterion 28 - Reactivity limits. The reactivity control systems shall be designed with appropriate limits on the potential amount and rate of reactivity increase to assure that the effects of postulated reactivity accidents can neither (1) result in damage to the reactor coolant pressure boundary greater than limited local 5uelding nor (2) sufficiently disturb the core, its support structures or other reactor pressure vessel internals to impair significantly the capability to cool the core. These postulated reactivity accidents shall include consideration of rod ejection (imless prevented by positive means), rod dropout, steam line rupture, changes in reactor coolant temperatme and pressure, and cold water addition. 

Toluene-/ sulplionamide is almost insolubb in cold water, but dissolves readily in sodium hydroxide solution (as the sodium derivative) aid is immediately reprecipitated on the addition of strong acids. To show the formation of the sodium derivative, dissolve about o-2 g. of metallic sodium in about 10 ml, of ethanol, cool the solution, and then add it to a solution of 1 g. of the sulphonamide in 20 ml. of cold edianol. On shaking the mixture, fine white crystals of the sodium derivative, CH,C,HjSO,NHNa, rapidly separate, and may be obtained pure by filtering at the pump, and washing firet with a few ml. of ethanol, and then with ether. 

If the amine is soluble in water, mix it with a slight excess (about 25 per cent.) of a saturated solution of picric acid in water (the solubility in cold water is about 1 per cent.). If the amine is insoluble in water, dissolve it by the addition of 2-3 drops of dilute hydrochloric acid (1 1) for each 2-3 ml. of water, then add a sUght excess of the reagent. If a heavy precipitate does not form immediately after the addition of the picric acid solution, allow the mixture to stand for some time and then shake vigorously. Filter off the precipitated picrate and recrystaUise it from boiling water, alcohol or dilute alcohol, boiUng 10 per cent, acetic acid, chloroform or, best, benzene. 

Conduct the preparation in the fume cupboard. Dissolve 250 g. of redistilled chloroacetic acid (Section 111,125) in 350 ml. of water contained in a 2 -5 litre round-bottomed flask. Warm the solution to about 50°, neutralise it by the cautious addition of 145 g. of anhydrous sodium carbonate in small portions cool the resulting solution to the laboratory temperature. Dissolve 150 g. of sodium cyanide powder (97-98 per cent. NaCN) in 375 ml. of water at 50-55°, cool to room temperature and add it to the sodium chloroacetate solution mix the solutions rapidly and cool in running water to prevent an appreciable rise in temperature. When all the sodium cyanide solution has been introduced, allow the temperature to rise when it reaches 95°, add 100 ml. of ice water and repeat the addition, if necessary, until the temperature no longer rises (1). Heat the solution on a water bath for an hour in order to complete the reaction. Cool the solution again to room temperature and slowly dis solve 120 g. of solid sodium hydroxide in it. Heat the solution on a water bath for 4 hours. Evolution of ammonia commences at 60-70° and becomes more vigorous as the temperature rises (2). Slowly add a solution of 300 g. of anhydrous calcium chloride in 900 ml. of water at 40° to the hot sodium malonate solution mix the solutions well after each addition. Allow the mixture to stand for 24 hours in order to convert the initial cheese-Uke precipitate of calcium malonate into a coarsely crystalline form. Decant the supernatant solution and wash the solid by decantation four times with 250 ml. portions of cold water. Filter at the pump. 

The filtrates from the decomposition of the brucine salts with dilute hydrochloride acid should be carefully preserved. The brucine Is recovered by the addition of an excess of dilute ammonia solution (1 4) if the solution becomes turbid before all the ammonia solution is added, introduce a little alcohol until the solution becomes clear. After several hours in an open beaker, filter oft the brucine, wash it well with cold water and dry it in the air. 

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