Monday, February 13, 2012

#Fukushima I Nuke Plant: Additional Info on That "Broken" Thermocouple on Reactor 2 RPV

From Yomiuri Shinbun (2/13/2012):

東京電力は13日、温度上昇を示していた福島第一原子力発電所2号機の原子炉圧力容器底部の温度計が同日午後の点検後、記録上限の400度を超えて振り切れるなど、異常な数値を示したと発表した。

TEPCO announced on February 13 that the thermocouple on the bottom of the Reactor 2 Pressure Vessel at Fukushima I Nuclear Power Plant, which had been showing the rising temperature, exhibited the abnormal temperatures after the inspection in the afternoon on February 13, at one time going overscale over 400 degrees Celsius which is the limit.

 東電は「ほぼ確実に故障している」とみている。温度計は炉心溶融で高温にさらされた後、湿度の高い環境に置かれていた。

TEPCO thinks it is "most certainly broken". The thermocouple had been exposed to high temperature from the core meltdown, and has been in the high humid condition [inside the Reactor 2 Containment Vessel].

 東電は同日午後2時頃から、中央制御室内で温度計の電気回路の点検を実施。回路の電気抵抗が通常より大きく、温度計の指示値が高く出やすいことが判明した。検査直後、回路を元に戻した際には342度を示し、一時振り切れるまで数値が上昇した。

TEPCO conducted the test of the electric circuit of the thermocouple from the central control room from 2PM. The electrical resistance was higher than normal, which would result in the temperature indicated by the thermocouple higher [than the actual temperature]. Right after the test, the temperature showed 342 degrees Celsius, and it rose sharply at one time and went overscale.

 温度計は、2種類の金属を接合したセンサー(熱電対(ねつでんつい))で温度を検知する。センサーが熱を受けると電流が流れる仕組みで、回路に異常が生じたために電圧が変化し、極端な値が表示された可能性がある。

The thermocouple is a bi-metal sensor to detect temperature. It produces a voltage when it is heated. It is possible that an abnormality occurred in the circuit which caused the voltage to change, resulting in the extreme measurements displayed.

In the press conference yesterday, TEPCO's Matsumoto said it was a copper-constantan thermocouple. Constantan is a copper-nickel alloy.

I was watching the press conference live, and was quite amused that TEPCO's Matsumoto and the junior PR manager were rather put off and irritated at some of the senior journalists who kept asking tough questions. They are not the usual fixture these days at TEPCO's press conferences.

These journalists, unlike the regulars (dwindling number, these days) who are mostly young boys and girls in their 20s and early 30s at most who hunch over their laptops and ask questions from behind the laptop display screen while they type, looked straight into Matsumoto, and ask questions with a pen in hand and a notebook on the desk.

Old fashioned way of journalism, which I thought was refreshingly effective. You have to knock TEPCO's PR people out of their kilter to get an edge and draw answers which TEPCO didn't intend to give.

As I mentioned in my post reporting the press conference, Matsumoto was particularly announced by the 2 questions:

One was posed by a reporter from Yomiuri Shinbun (he's a regular). The reporter asked if the test itself broke the thermocouple. (Bingo...) Matsumoto denied the possibility, saying the test was conducted distantly from the central control room, not at the thermocouple (no way, as it is inside the CV).

The other was posed by an independent journalist who kept asking Matsumoto if TEPCO was consulting the manufacturer of the thermocouple for insight and technical assistance. That really set off Matsumoto, who immediately said TEPCO was fully capable of the maintenance of the thermocouples at the plant. Despite repeated questions, Matsumoto refused to give the name of the manufacturer or whether the representative of the manufacturer was on hand at Fukushima I Nuke Plant.

Never mind that this is not an ordinary maintenance of the thermocouples in a functioning reactor.

8 comments:

Anonymous said...

well it IS just a god damn thermocouple - two isolated wires made of different metals, joined at one end. that's all there is to it.

i can see how nuke guys may be annoyed when you imply they don't know how to deal with one.

Anonymous said...

Anony, very simple device, so COULD the test done by TEPCO break the sensor? Should they try the exact same test on the OTHER sensors who are reporting what TEPCO wants to hear-see if they break or are okay? Lets see..they test one sensor which has results they dont like. Two others, with the GOOD results..they are not going to test. Would think they could test sample at least one of the others.
Another way to look at Reactor 2, is to ask a simple question. Is radiation increasing in Fukushima since the temperature sensor showed heating? The answer is YES. So that is one reason to test the other sensors--or to try and identify WHAT reactor sources caused the increase. If its not Reactor 2--then which one?

And, it might not hurt for the "nuke boys" to ASK for outside help..they are not Lone Rangers. We are all in this mess, we live on continents and islands with radiation courtesy of TEPCO and its ineffective control of at least 4-6 reactors in Japan.

Anonymous said...

Meanwhile, in Kansai:
"Japan's nuclear safety watchdog on Feb. 13 approved initial stress tests on the first pair of dozens of idled reactors, an early step in efforts to rebuild public trust in atomic energy after the world's worst nuclear accident in 25 years."
http://ajw.asahi.com/article/0311disaster/fukushima/AJ201202130077

Some nuclear engineers are not happy about the decision:
http://gotomasashi.blogspot.com/2012/02/34.html?spref=fb

Anonymous said...

patio888 in Centre Wellington, Ontario, Canada sez "no problem."

Need another means to infer 'temperature' in these conditions rather than thermometer?

Perhaps, pump a known velocity of inert gas into the pressure vessel and measure velocity on the outflow, thereby determining gas expansion while inside.

This velocity measurement would infer temperatures by the expansion of the inert gas. Inert gas is subject to 'Charles's law' by operating a simple calculation of "V1T2=V2T1."

A device constructed of a sealed tantalum probe tube with a smaller diameter internal tantalum tube suppling a velocity of inert gas. Measure differential of inlet and outlet through a 'curved tube coriolis flow meters' on the inlet side and another mass flow meter on the outlet side.

An accurate temperature reading is calculated by "V1T2=V2T1" inferred through velocity change.

By modulating the flow rates a system entropy loss diagram can be built. for this specific alternative temperature measuring system.

Simple.

So, why is everybody being so stupid?

Am I the world's smartest man?

If so, we are all in a lot of trouble.

Looking for work, tired of freezing my petunias off to pay my mortgage.

Any offers? Resume is flying, now just looking for a fat target. Hack my email address, it's o.k.

Anonymous said...

Measuring the resistance of a thermocouple involves placing a protential difference (voltage) across the thermocouple. Of course the test could have damaged it.

Atomfritz said...

It could even have been damaged intentionally.
It's easy to destroy electronic components by "testing" them with inappropriate voltages and currents.

One could suspect an undesirable witness to have been "shot".

Anonymous said...

@patio888

your idea would work just fine if the RPV did NOT have an unknown number of new holes in it, all leading to the atmosphere via the PCV which is also compromised in an unknown manner.

But other than that, jolly good try, ol' chap. Keep chipping at it, something good's bound to come out of it sooner or later. Sorry about your petunias by the way.

I myself was flamed into oblivion early on in the accident progression when I suggested that TEPCO should just drill into the sides of the reactors to instrument them and maybe pour water too.

Lo and behold, eleven months later TEPCO drill into reactor 2 to put a borescope in and we get FOIA disclosure of NRC emails where a noted physicist suggested shaped charges (!) as a means to get at the cores to cool them.

Anonymous said...

The article states "TEPCO's Matsumoto said it was a copper-constantan thermocouple. Constantan is a copper-nickel alloy." This is commonly known as a type "T" thermocouple. Check any manufacturer's web-site and you will find the suggested use range is 0 to 350C. If they were "capable" in the area of thermocouples, why did they select a type "T" when their temperature range required would be far outside of the type "T" range?

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