| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1998: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1997: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
Sodium and lithium are useful coolants, but catch a serious accident fire when it leaks out at the high temperature into the air.An experiment of the sodium and lithium (though it was a small quantity) was done with the various conditions to get knowledge about combustion condition and repression of a fire.
I.Sodium combustion
When it burns, the fluidity of the sodium is good for becoming a liquid (melting point 97.8ﾟC), and a combustion direction becomes more drastic combustion than extent by the slope of a combustion floors.But solification temperature of the combustion formation thing is high, and obstructs the flowing diffusion of the liquid sodium.The sodium of about 50g was put on the combustion plate, and heated from the bottom part, and was caught fire.A heater is cut after catching fire and it is made burn itself.The controlled humidity and oxygen concentration were supplied and the fire was observed.
1. Natural cumbustion in the atomosphere : The sodium catches fire with 250-4O0
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ﾟC.The highest temperature was 800ﾟC.Remnants are soft with the sponge-shaped of yellow.
2. Repression combustion by the limited fresh air : It did not extinguish the fire that burned at 1.5% of open rates of the combustion room.
3. The oxygen concentration adjustment combustion : Though combustion becomes gentle when oxygen concentration falls down, it does not extinguish the fire in oxygen concentration 5%.
4. Nitrogenous gas extinguishing : It exitinguishes the fire when nitrogenous gas is fully put out in the combustion room.
5. Nitrogenous liquid putting out the fire : The flame vanishes in a moment.But it burns again when new air flows in if temperature is not less than 250ﾟC.
II.Lithium combustion :
Even if lithium is thrown into the water, a tremendous reaction like sodium does not have it by the solid which is close to the globular form.It is a surface foams.But a reaction with the drastic explosion is started in the time when it becomes thin foil.The melting point is high (180ﾟC) and it takes a long time to reach combustion.It becomes more than 1100ﾟC as soon as it takes fire.It can not extinguished the fire with the nitrogenous gas like sodium.The fire is strengthened.
1. Natural combustion in the atmosphere : Catching fire temperature is more than 450ﾟC, and combustion starts in a moment.The white smoke of lithium oxide is given to it violently, and it becomes the high temperature of 1150ﾟC, and the stainless steel of the combustion container is made to rot.Thermocouples of sheath manufactured by stainless steel or inconel damage sheath because of the oxidation and corrosion, therefore an inside insulation disappears.When oxygen concentration is made to decrease, combustion becomes quiet, and temperature reach about less than 800ﾟC.Remnants become the spores-shaped of the gray mold, and it swells, and soft.
2. Nitrogenous gas reaction : The smoke of lithium oxide decreases rapidly the violence of the combustion when nitrogenous gas is blow with the ventilator after it becomes enough combustion condition in the atmosphere.But lithium temperature becomes fixed in about 700ﾟC, and it is clear that lithium and the nitrogeneous gas reacts.Because there is a little reactive gas, a comparatively quiet melting surface is observed.Putting out the fire can not be done.
3. Putting out the fire by argon gas : Argon gas was blown after the atmosphere combustion became sufficient.It cut down the fire in a moment, and temperature decreased, too. Putting out the fire can be done. Less
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