Thursday, April 14, 2011

#Fukushima I Nuke Plant: Reactor 2's RPV Temperature Is Minus 116.3 Degrees Celsius

The Reactor 2's Reactor Pressure Vessel (RPV)'s temperature at the bottom was -116.3 degrees Celsius on April 14, according to Nuclear and Industrial Safety Agency of METI.

That same temperature was 183 degrees Celsius on April 13.

Also, the temperature of the Reactor 2's Spent Fuel Pool on April 14 was 71 degrees Celsius; the same temperature on April 13 was 46 degrees Celsius. The temperature of the Spent Fuel Pool seem to be oscillating between 45, 46 degrees and 70, 71 degrees.

It can only mean one thing, and that is that the instruments are broken. (Sorry for stating the ultra-obvious.)

From the plant parameter sheet from NISA on April 14 (Japanese only for now):


Anonymous said...

Are they possibly pumping in liquid nitrogen? That might account for the cold...

M. Simon said...

Or a typo.

Here is my opinion. They are doing feed and bleed to keep the weight of water in the eqpt to a minimum. More earthquakes expected.

So - temperature rises as water level falls - add water. Temperature falls and water level rises - let it vent. Repeat for 2 or 3 years. And hope to hell no one screws up the manual process in that time. What are the odds?

Anonymous said...

Hey, things are looking up! If the RPV chills to absolute zero all molecular motion should stop right? (sarcasm off)

Man, this is just another bad to worse situation to add to the list. I doubt they have the ability to easily change the thermocouples or troubleshoot them either. IIRC RPV #2 wasn't holding any pressure I wonder if something melted through the instrumentation channels in the bottom of the reactor and damaged the thermocouple?

Here's a little SFP tidbit I found yesterday:

NUREG-0933, ―Resolution of Generic Safety Issues: Issue 82: Beyond Design Basis Accidents in Spent Fuel Pools (Rev. 3) (NUREG-0933, Main Report with Supplements 1–33)‖ summarizes current spent fuel storage practices and the risk of radiation release to the atmosphere:

A typical spent fuel storage pool with high density storage racks can hold roughly five times the fuel in the core. However, since reloads typically discharge one third of a core, much of the spent fuel stored in the pool will have had considerable decay time. This reduces the radioactive inventory somewhat. More importantly, after roughly three years of storage, spent fuel can be air-cooled, i.e., such fuel need not be submerged to prevent melting. (Submersion is still desirable for shielding and to reduce airborne activity, however.)

If the pool were to be drained of water, the discharged fuel from the previous two refuelings would still be "fresh" enough to melt under decay heat. However, the zircaloy cladding of this fuel could be ignited during the heatup. The resulting fire, in a pool equipped with high density storage racks, would probably spread to most or all of the fuel in the pool. The heat of combustion, in combination with decay heat, would certainly release considerable gap activity from the fuel and would probably drive "borderline aged" fuel into a molten condition. Moreover, if the fire becomes oxygen-starved (quite probable for a fire located in the bottom of a pit such as this), the hot zirconium would rob oxygen from the uranium dioxide fuel, forming a liquid mixture of metallic uranium, zirconium, oxidized zirconium, and dissolved uranium dioxide. This would cause a release of fission products from the fuel matrix quite comparable to that of molten fuel. In addition, although confined, spent fuel pools are almost always located outside of the primary containment. Thus, release to the atmosphere is more likely than for comparable accidents involving the reactor core.

arevamirpal::laprimavera said...

@anon, nitrogen injection is still only on Reactor 1.

@simon, 4/15 sheet still shows -116 degrees Celsius. About the odds, I wouldn't count much on Japanese; they once transported uranium in a bucket, smoking cigarettes.

@robbie, isn't it a brilliant design, to have spent fuel pools right there at the top?

M. Simon said...

SFPs and containment - statement to Congress 30 March 2011

M. Simon said...

#4 temps up due to cooling lapse

arevamirpal::laprimavera said...

@simon, thanks for the info on reactor 4 spent fuel pool. That was COMPLETELY missing from the news coming out of Japan. Zero. Nothing.

Anonymous said...

Or the temperature is so high that it caused a bit overflow. Its likely that that sensor is a digital device, and perhaps might have topped out at 256 degress C. Beyond 256, the numbers start negative. Its possible that real temperture could have risen to 372 C (256 + 116). It difficult to say for certain without knowing details about the temperture sensor. If we had a constant data log of the data we could probably determine the real temperature, if it cause is indeed a bit overflow with the sensor data.

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