Unit 3 New Water Leak; TEPCO Explanations Fail To Identify Source

TEPCO has reported a leak in unit 3 coming out of the area of the steam tunnel where the main steam isolation valves are. Initially TEPCO reported this as being rainwater with no further proof how they came to that conclusion. Today they claimed it is water from containment without further clarification.

A number of people have suggested it may be the MSIV valve or steam line leaking and have concerns that it broke during the 2011 earthquake. This would have major consequences for the world wide nuclear industry as it would show a serious design failure. What has been missed in these concerns is that the steam pipe has a finite amount of water in it. If the pipe had leaked since 2011, it would now be out of water. The reactor vessel does not hold water up to the level where the steam lines connect to the reactor, by TEPCO’s admissions it does not hold water at all due to the meltdown. So if it is a leak from the steam pipe or MSIV failure it would have to be recent to still be leaking water as there is a finite volume of water left in these pipes.

TEPCO now claims that the leak is water leaking out of containment. This explanation fails because the bottom of the containment structure is 1/2 floor below the steam tunnel and MSIV room. For water collecting in the containment structure to leak out it would have to be extremely high or running uphill. The estimated level for standing water in containment has been documented as being much lower. This makes TEPCO’s explanation very unlikely. Diagram below shows the floor of containment in grey and the steam tunnel room in blue.

containment_steam 

Other possibilities considered have been a leak of an existing cooling system pipe or something similar related to the spent fuel pool. The radiation levels in the water are somewhat similar but the temperatures differ considerably. We have not completely ruled this possibility out as of now.

The other possible source is the injection water being sent into the reactor. The pipes for this run through the steam tunnel. The feedwater pipe is known to be housed in the same location. The radiation levels in the water differ considerably as does the temperature. The water injection is the only known source of ongoing water supply to the building and the gpm rate for water injection is similar to the gpm of the leak.

The actual source is still elusive but the initial causes given do not hold up. Below are some of the details of the issue including temps etc. from TEPCO

Floor plan showing the steam lines and feedwater lines in the steam tunnel:

Floor plan with location of the leak and photo of the leak location. We have estimated the flow rate to be about 10 gpm.

 

 

U3_msivleak 

Analysis of the water leak: (translations from Ex-SKF)

Nuclide analysis of the leaked water: sample taken on 1/19/2014
Cesium-134: 7.0×10^2 Bq/cm3 (700 Bq/cm3)
Cesium-137: 1.7×10^3 Bq/cm3 (1,700 Bq/cm3)
Cobalt-60: 2.5×10^1 Bq/cm3 (25 Bq/cm3)
All-beta: 2.4×10^4 Bq/cm3 (24,000 Bq/cm3)

Temperature of the leaked water: measured at 5PM on 1/19/2014
About 20 degrees Celsius

Related temps:
*Atmospheric temperature at the location of the leak: 7 degrees Celsius (measured at 10AM, 1/19/2014)
Temperature of the water being injected: 7 degrees Celsius (measured at 5PM, 1/19/2014)
We also looked up the current spent fuel pool water temperature and found it to be 7.9 ℃
The leak is considerably warmer than the air in the building, the injection water and the water in the spent fuel pool.

Water radiation levels from other locations:

Latest nuclide analysis of water being injected into reactors: sample taken on 12/10/2013
Cesium-134: below detection level
Cesium-137: below detection level
Cobalt-60: below detection level
All-beta: 2.8 Bq/cm3

“According to that analysis, the highly contaminated water that sits in the reactor building basement (supposedly after having come to full contact with the corium) has:”
Cesium-134: 1.0×10^4 Bq/cm3 (10,000 Bq/cm3)
Cesium-137: 2.5×10^4 Bq/cm3 (25,000 Bq/cm3)
Cobalt-60: 1.4 Bq/cm3 (after treatment with SARRY)
All-beta: 2.3×10^4 Bq/cm3 (23,000 Bq/cm3, before RO treatment)

Also for cross reference, unit 4’s spent fuel pool water radiation levels to understand how the leak water compares to levels found in the spent fuel pools:

(Minutes taken October 17, 2013) Unit 4 spent fuel pool water Reference]
cesium 134:1.8 × 10 ^ 3 Bq / L
cesium-137:7.9 × 10 ^ 3 Bq / L
cobalt-60: 4.1 × 10 ^ 4 Bq / L
manganese-54: 2.7 × 10 ^ 2 Bq / L

TEPCO’s initial handout on the problem
http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140118_03-j.pdf 

 

 

 

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