More On Fukushima Unit 3, TEPCO Fails To Explain Levels

TEPCO released two new handouts on the leak at unit 3. This gives some additional insight but still fails to explain a number of critical issues.
Handout 1: http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140122_05-j.pdf
Handout 2: http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/images/l140120_01-e.pdf

TEPCO does not provide any data to explain their claim for where the water level in containment is. They cite using pressure readings to determine this but give no information to show how they came to such a conclusion. Available pressure readings show a single sensor for the containment structure and one for the suppression chamber (torus). The torus has considerably more pressure than the containment structure. The suppression chamber is around 183 kpa and the containment structure at .22 kpa. TEPCO also does not explain how lower containment penetrations would remain intact yet the MSIV room ones failed. This is a requirement to have happen for their theory that water inside unit 3 containment is unusually high.

u3_pressure

Also not explained is why water leaks from the two containment hatches have created much higher ambient radiation levels than the leak from the MSIV room. If both are simply leaks of water from containment they should be nearly equal in radiation level. Levels near the water leak on one of the hatch doors was over 4 Sv/h while the levels near the MSIV room leak are around 30 mSv/h

A scope inspection is planned to look into the MSIV room. The current plan is to insert a camera scope from the room above and look into the MSIV room to determine leakage and other information. This would be done by workers. TEPCO has opted to go in through the ceiling as they think the room may be partially filled with water. The radiation levels for the room above are estimated to be around 2-3 mSv/h while levels outside the MSIV room are around 30 mSv/h. TEPCO does not say when this work will take place.

U3_msiv_inspection TEPCO also released some temperature readings. The water leak is warmer than a line sensor for the MSIV system and two degrees cooler than readings taken inside the containment structure.

U3_msivtemps

They also included a radiation reading for the unit 3 turbine building that was similar to what is found in the MSIV room leak. These levels also closely match the spent fuel pool radiation levels.

The handout in Japanese included many things not included in the English one released the same day. This diagram of the pipe penetrations used in the MSIV room show that the bellows seal if seated inside containment would provide a clear leak route if the bellows leaks or fails. Previously TEPCO cited that these pipe penetrations are sealed with a “resin” that could have degraded during the meltdown. We found ample evidence that common penetration seal materials like Fireblock-D are subject to corrosion, heat and pressure degradation. Under high heats this type of sealant will degrade. This particular substance was in use at US plants built during the same years as Fukushima Daiichi.

TEPCO_msiv_pipepenetration The new information does give some insight into the issues inside unit 3. Important questions remain to be answered. The planned scope effort could give new important clues to help determine if TEPCO’s assumptions are correct or if another cause is to blame.

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