Saturday, February 11, 2012

(Updated) TEPCO Press Conference on Reactor 2 RPV Temperature

TEPCO's Matsumoto opening remarks:

No Xe-135 detected in the latest gas sampling test.
Preparing to increase water.
1090 kilograms of boric acid solution has been poured into the RPV.

At 2:20PM, the temperature exceeded 80 degrees Celsius.
Since other temperatures at the bottom of the RPV remain low and the temperature of the Containment Vessel is not rising, the cold shutdown state remains.

(There are many reporters this time...)

It's the blue line in the chart (screen capture):

TEPCO thinks it is physically "very difficult" for the temperature to rise above 80 degrees Celsius, and it is likely to be the instrument failure.

No cesium-134 and 137 have been detected, so there is no steam being generated inside the RPV/CV.

Graph generated from the automatic digital reading showing 10 degrees "noise" starting 12 noon (before noon, the noise was 1 degree):

Asahi Shinbun's reporter asked how high exactly the temperature went, as the graph seemed to show the spike above 90 degrees Celsius.

Matsumoto answered the graph is plotting all the 1-second readings from the digital display, not visually verified by the workers. The official reporting is every 6 hours, the reference reporting is every hour.

Q: Will the amount of water be increased if the thermometer at that location continues to rise?
A: We will have to be careful. If the increased water doesn't lower the temperature, the instrument failure will be more likely.

Q: How to verify the instrument failure?
A: We want to do the resistance testing from the central control room.

Q: Why has the temperature started to vary widely since noon?
A: We don't quite know.

Q: When will you get back to the normal operation under the safety regulations?
A: To do it, we have to make sure it is the instrument failure.

Q: Does the instrument failure have to do with the variance?
A: It's not that the instrument failure started today, but it may have started late January when this thermometer started to behave differently from the other two at the bottom of the RPV. The 10 degrees Celsius water is right near the thermometer (15 centimeter away), and the thermometer shows rising temperature. The location of the thermometer should be uniformly cooled.

Q: Where do you measure the temperature of the water injected?
A: The temperature of the water is measured at the buffer tank. No place along the way to get heated.

Q: What happens if the temperature doesn't drop?
A: We will wait and see for a day.

Q: Why did you start mentioning "instrument failure" only when the temperature started to approach 80 degrees Celsius?
A: We didn't think it was behaving erratically. The variance of 1 degrees was understood. The trend changed at the end of January. Also, the temperature remained high as more water accumulate inside the RPV, therefore the instrument failure more likely.

A: We want to see if it is possible to have the instrument failure where the temperature drops, instead of going up.

A: The Containment Vessel is still hot and humid, so we have to make sure the other instruments are working properly. At this point, we don't have better alternatives.

9.9 (core spray, from 6.9) + 7.5 (feed water) = 17.4 tonnes/hour of water is to be injected into the RPV.

Q: Why are you increasing the amount of water if you think it is the instrument failure? What do you think of the safety regulations?
A: We have always informed the NISA and followed the safety regulations. (No answer on why they are increasing water.)

Q: Why did you pick this particular thermometer as the representative temperature for the RPV?
A: Perhaps it was one of the first to come back online last fall, but we will confirm.

Q: What happens if other thermometers fail?
A: We have to think about how to monitor the condition of the reactor, as we cannot enter the Containment Vessel.

(The press conference just finished. The above note is not necessarily comprehensive. In short, TEPCO thinks it is more likely to be the instrument failure, not the actual temperature rising, but it will continue to monitor the situation.)


Chibaguy said...

So they went instrument failure. That is expected but if they suggest instrument failure that means all instruments. No auditor in their right mind would take this as an excuse.

Anyway cold shutdown still in place as the idiotic Noda declared (he does not even deserve san). Tepco is not interested in finding the corium at the least. This is all semantics and their suggestion means all data is compromised.

arevamirpal::laprimavera said...

I wouldn't go that far, that all instruments are failing. It does seem unique to this particular location.

There must be a reason why the thermometer started to go wild at noon. I'm treating this like a point-and-click adventure game. Devils in the details.

STeVe the JeW said...

reporter: "There must be a reason why the thermometer started to go wild at noon."

tepco: yes, the thermometer started to stop failing.

Chibaguy said...

Thank you for the update. If proving that an instrument is malfunctioning is the goal they have no plan. At least the reporters seem to be asking more direct questions. Just out loud, does anyone know actually where all the water being pumped in goes?

TokenRing said...

Yes out into the ocean

Atomfritz said...

Yes, it's more convenient to state an instrumentation failure than the factual possibility that the corium grains now have been become dislodged and concentrated on several spots.

(Remember, corium grains and no molten blob were observed at TMI when they finally were able to open the RPV! The Tepco graphics falsely suggest the corium being there in the form of a lense blob!)

Similar to when rainwater drops from the ceiling, cleaning the spot where the drops impact and distributing the dirt around them which was formerly distributed equally everywhere, the corium grains have been sloshed around by the cooling water pouring from above.

There is probably no way to undo this consequence of switching from flood cooling to pour cooling.

In fact, the increase of cooling water quantity could even have contriubuted to increase that effect.

And now these locations where the corium grains pile up get denser and hotter, Tepco increases cooling water quantity again, but in vain, just keeping this vicious cycle going on.

The hot area near the temperature sensor has become so dense and big that it is no longer continuously cooled.

Regularly it heats up, until it gets hit again by the (random) swells of water.

So the temperature spikes may very well indicate how quickly now these concentrated piles of corium debris heat up when they don't get sufficient water for a moment when the (random) water flow from above changes for a moment.

Thus the temperature sensor could as well illustrate the effect of a grossly failed attempt to "improve" the situation in this black box of reactor.

So putting the blame onto a "suspected" instrumentation failure could be a clever face-saving maneuver to avoid admitting that they irreversibly worsened the situation by headlessly trying to "improve" it.

(Just my personal theory.)

CaptD said...

Local Government Officials have a vested interest in protecting their people from further radiologic exposure; or they will lose their OWN jobs and maybe more!

All professionals in Japan should be standing up to hold TEPCO responsible for its policy of nuclear secrecy and spreading Nuclear Baloney (NB) instead of the truth!

Remember the Japanese people now “own” a controlling interest in TEPCO since they had to bail out TEPCO because of this Trillion Dollar Eco-Disaster!

Why does TEPCO and the Japanese Gov't want to declare it's Fukushima disaster Stable and more importantly, what do they hope to accomplish by doing it now; Is it a trial balloon?

A. If the people "swallow" this Nuclear Baloney (NB) then TEPCO and their other Gov't Leaders get to keep their jobs and march onward toward a nuclear future while the Nuclear refugees are "encouraged" to return to their Fukushima homes; letting history be the judge of whether or not this was the RIGHT decision.

B. The people of Japan reject the concept of a "cold shut down" in which case TEPCO, in time, gets nationalized and Japan develops a 20 year plan to replace it's reactors with solar of all flavors!

C. The people of Japan are insulted by what TEPCO and their Gov't is saying and take to the streets to DEMAND immediate change. TEPCO and their Government overseers are both swept away in order to placate the people of Japan. The Nuclear Refugees get settlements and the area