[Column] Is Tepco injecting liquid nitrogen into reactor1 ?

Since the end of September, Fukushima Diary has been reporting the repetitive increase of the temperature inside of reactor1 PCV.

(cf. PCV temperature picked up in reactor1 again)

It had been stable at 56℃, but it jumped up and down between 60℃ and 70℃.

Though there was no official announcement about this phenomena, Fukushima Diary reported the connection between the RPV water level and PCV temperature.

(cf. Reactor1 losing water and temperature is in increasing trend)

From the end of September, the water level in RPV has been the lowest level since this July. On the day when the RPV water level was low, the PCV temperature went up.

Tepco hasn’t given any announcement about this either.

However, the temperature turned to be in decreasing trend since 10/23/2012 as you see by the blue line on the graph below. [Link]

On 10/23/2012, Tepco started injecting nitrogen gas into reactor1. The reason is supposed to control density of hydrogen gas, but whether it was expected or not, the PCV temperature is decreasing. They are injecting nitrogen gas into suppression chamber and also RPV.

(cf. To avoid the risk of explosion, Tepco is to inject nitrogen gas to suppression chamber of reactor1 for a month)

However, the RPV water level is decreasing more than ever. Since 10/23/2012, it has been decreasing from -1.64m to -1.81m.

This is not the first time that you see this strange connection between PCV temperature and nitrogen gas injection.

In Earlier 2012, Tepco had one of the nitrogen gas injection equipment stopped by strong wind.

They were injecting nitrogen gas to avoid the risk of hydrogen gas explosion, but the temperature increased by 6.4℃ only within 90 minutes while the nitrogen gas injection was stopped.

(cf. Reactor 1 goes over 100℃ within 8 hours without nitrogen injection)

Why does it get cooled down when they inject nitrogen gas ?

In this April, Fukushima Diary asked a freelance journalist to give the query to Tepco.

In the daily press conference, Tepco answered it was because the thermometer is located near the jet of nitrogen gas.

They explain, the jet makes the thermometer indicate it as if the temperature was going down like you feel cool in front of a fan or an air-conditioner. (I shall find out the ustream video when they were explaining it by using a white board.)

The temperature of the nitrogen gas is supposed to be as hot/cold as outside air.

Anyway, the nitrogen gas seems to cool down the thermometer of PCV.

In Chernobyl, Soviet union injected liquid nitrogen for coolant material. [Wikipedia]

With the bubbler pool gone, a meltdown was less likely to produce a powerful steam explosion. To do so, the molten core would now have to reach the water table below the reactor. To reduce the likelihood of this, it was decided to freeze the earth beneath the reactor, which would also stabilize the foundations. Using oil drilling equipment, the injection of liquid nitrogen began on 4 May. It was estimated that 25 metric tons of liquid nitrogen per day would be required to keep the soil frozen at −100 °C.[18]:59 This idea[67] was soon scrapped and the bottom room where the cooling system would have been installed was filled with concrete.

By the way, if nitrogen gas injection manipulates the thermometer of reactor1, it is another problem because we can’t tell how much it is actually heated.

Iori Mochizuki

 

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Italiano:

[Editoriale] La Tepco sta iniettando liquido nitrogeno nel reattore 1?

Dalla fine di Settembre, Fukushima Diary ha riportato il ripetitivo incremento della temperatura all’interno del PCV reattore 1.
(cf. PCV temperature picked up in reactor1 again)
E’ rimasta stabile a 56°C ma poi è balzata su e giù tra i 60°C e 70°C
Anche se non c’è stata alcuna comunicazione ufficiale su questo fenomeno, Fukushima Diary ha riportato la connessione tra il livello dell’acqua dell’RPV e la temperatura del PCV.
(cf. Reactor1 losing water and temperature is in increasing trend)
Dalla fine di Settembre il livello dell’acqua nell’RPV è stato il più basso da questo Luglio. La Tepco non ha dato alcuna comunicazione nemmeno su questo.
Comunque, la temperatura ha ricominciato a scendere dal 23/10/2012 come potete vedere nel grafico.

Il 23/10/2012 la Tepco ha iniziato iniettare gas nitrogeno nel reattore 1. Il motivo dovrebbe essere quello di controllare la densità del gas idrogeno ma, che fosse previsto o meno, la temperatura del PVC sta scendendo. Stanno iniettando gas nitrogeno nella camera di soppressione e nella RPV.
(cf. Per evitare il rischio di esplosione, la Tepco inietterà gas nitrogeno nella camera di soppressione del reattore 1 per un mese)
Comunque il livello dell’acqua dell’RPV sta scendendo più che mai. Dal 23/10/2012 è sceso da -1.64m a -1.81m

Non è la prima volta che vediamo questa strana connessione tra la temperatura del PCV e l’iniezione di gas nitrogeno.
All’inizio del 2012 la Tepco ha dovuto interrompere un iniezione di gas nitrogeno a causa del forte vento.
Stavano iniettando gas nitrogeno per evitare il rischio di un’esplosione di gas idrogeno ma la temperatura è aumentata di 6.4°C solo nei 90 minuti in cui l’iniezione di gas nitrogeno è stata interrotta.
(cf. Reactor 1 goes over 100℃ within 8 hours without nitrogen injection)
Perchè si raffredda con l’immissione di gas nitrogeno?
Questo Aprile Fukushima Diary ha chiesto a un giornalista freelance di porre la domanda alla Tepco.
Nella confenza stampa la Tepco ha risposto che accadeva perchè il termometro è posizionato accanto al getto di gas nitrogeno.
Hanno spiegato che il getto fa indicare al termometro una temperatura più bassa come se ci si posizionasse di fronte a un ventilatore o all’aria condizionata. (Devo trovare il video in cui lo spiegano utilizzando una lavagna bianca).
La temperatura del gas nitrogeno dovrebbe essere calda/fredda come l’aria esterna.
In ogni caso il gas nitrogeno sempre raffreddare il termometro della PCV.

A Chernobyl l’Unione Sovietica ha iniettato liqido nitrogeno come materiale raffreddante  [Wikipedia]

With the bubbler pool gone, a meltdown was less likely to produce a powerful steam explosion. To do so, the molten core would now have to reach the water table below the reactor. To reduce the likelihood of this, it was decided to freeze the earth beneath the reactor, which would also stabilize the foundations. Using oil drilling equipment, the injection of liquid nitrogen began on 4 May. It was estimated that 25 metric tons of liquid nitrogen per day would be required to keep the soil frozen at −100 °C.[18]:59 This idea[67] was soon scrapped and the bottom room where the cooling system would have been installed was filled with concrete.

Comunque sia, se effettivamente il gas nitrogeno modifica la temperatura del reattore, è un altro problema perchè non possiamo sapere quanto effettivamente questo sia surriscaldato.

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