Sunday, June 5, 2011

#Fukushima I Nuke Plant Reactor 1: RPV's Pressure Turns Out to Be Very Close to Atmospheric Pressure

TEPCO installed the pressure gauge in the Reactor 1 on June 4, and surprise surprise! The pressure measurement of the Reactor Pressure Vessel (RPV) had been all wrong.

The pressure readings of the Reactor 1 RPV had been used by TEPCO to defend their position that the RPV was not damaged, or was damaged but not by much. It had been also used by TEPCO to claim that there was water inside the RPV. Say goodbye to both fantasies for good.

From METI's press releases on the Fukushima Plant Parameters on June 3 and June 5:

Reactor 1 RPV Pressure Measurement in megapascals (MPa):

June 3:
Gauge A: 0.578 MPa g
Gauge B: 1.573 MPa g

June 5:
Gauge A: 0.025 MPa g
Gauge B: discontinued

MPa g = MPa abs - atmospheric pressure (0.1013 MPa)
("g" stands for "gauge, and "abs" stands for "absolute". )

So, if you see the RPV number in MPa g equal to zero, it means the RPV pressure is equal to the atmospheric pressure. If the number is negative, like the Reactors 2 and 3 RPVs, the RPV pressure is lower than the atmospheric pressure.

The next fantasy to go will be the pressure of the Reactor 1 Containment Vessel. It is again being used as the reason to believe the melted core is still within the Containment Vessel. (Never mind that the contaminated water is leaking inside the reactor building...) TEPCO says they will install the pressure gauge for the Containment Vessel soon.

For now, the pressure numbers for Containment Vessel show that it is above the atmospheric pressure in the Drywell, and almost at the atmospheric pressure in the Suppression Chamber. That's not surprising about the SC, as we've seen the gushing of "hot" steam (4 sieverts/hour) from the compartment that houses the SC.

Reactor 1 Containment Vessel Pressure Measurement in megapascals (absolute), from METI's press release on June 5:

Drywell: 0.1301 MPa abs [or 0.029 MPa g]
Suppression Chamber: 0.110 Mpa abs [or 0.0087 Mpa g]

(Why can't they just measure everything in either MPa g or MPa abs?)


Anonymous said...

Next fantasy, pressure of Containment Vessel.

Then, the groundwater is ok.

netudiant said...

Seems that reality is gradually creeping in.
We have three busted and broken reactors, still spewing contaminants into the world at large, three months after the accident. The only good news is that the cooling water has absorbed most of the contamination and that the decay heat is declining slowly.
TEPCOs efforts will begin to bear fruit towards year end, when the plant gradually gets pumped out. Reality is that they were entirely ineffectual in terms of the reactor meltdowns or the subsequent radioactive emissions across central Japan.

Anonymous said...

@ netudiant,

Some of your perspective is good, but the "good news" coming out of Japan is nowhere good.

"cooling water has absorbed most of the contamination" ? It has only just begun.

"decay heat is declining slowly" ?
So slowly as to be of no consequence. Spent fuel pools are "declining slowly", too, yet are a huge threat still.

The full picture is one step beyond the "good news" scenario.

Clear your vision.

Lucy said...

I like to make friends with you,haha.

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