There have been a number of things going on at the plant in recent weeks that do not make the news. These efforts are progress towards improving conditions and also understanding the meltdowns.
Reduce Water Injection To Reactors
TEPCO plans to reduce the reactor water injection rate at units 2 and 3. They indicated that changes to the nitrogen levels in unit 1 showed a temperature rise that gave them concerns about reducing water injection at unit 1. Water injection will be reduced by small increments and then systems will be monitored for changes that may indicate a heat up of the melted fuel. This is something we suggested in our proposals to IRID. This effort is intended to slow the build up of contaminated water at the plant.
TIPS Substances Analyzed
TEPCO has analyzed samples from the TIPS system at unit 2. These probe lines were found to be filled with what appeared to be some sort of melted debris and was significantly radioactive. To gain a better understanding of what it was they ran a substance analysis. While nothing that was obviously melted fuel was found, it does appear to be melted metals from the core along with some other substances. They were unable to run the probes through the lines into the pedestal area, melted materials were found further in the lines.
This is a list of everything found in the samples taken:
Cl = Chlorine
Cr = Chromium
Mn = Manganese
Fe = Iron
Co = Cobalt
Ni = Nickel
Cu = Copper
Zr = Zirconium
Mo = Molybdenum
These are TEPCO’s assumptions about the sources of these materials:
Zr = It is considered to have originated from the fuel cladding and the channel box.
Fe, Cr, Ni = The stainless steel (or the like) is used in the furnace structure or guide tubes.
Co = Origin can not be determined, but it is also contained in the reactor water during normal operation.
Mn = From the RPV (reactor vessel) It is believed to be due to manganese and molybdenum steel that is used for that.
Mo = Molybdenum disulfide , which is applied as a lubricant in the guide tube inner surface. In addition , the structural material , such as sta.inless steel and manganese – molybdenum steel It is considered that due to the material .
Cl = Is due to the film used to prevent contamination of the device main, it may also be due to seawater injection.
Cu = Is used in some sort of plate within the reactor, origin is not clear.
ALPS Still In Testing, Start Bumped To April 2014
ALPS, the water filtration system that has been key to handling the contaminated water problems at Daiichi is still in testing phases with 3 lines now installed but none of them ready to actually function. Toshiba is running the project and has run into problems with control systems and corrosion. Now Japanese news is reporting that the start date has again been pushed back, from November 2013 to April 2014.
Wider Isotope Testing
The testing of water from various locations around Fukushima Daiichi are giving a better idea what is leaking at the plant. Samples of highly contaminated water found underground and assumed to be similar to reactor water were sampled along with water that had been treated by the cesium absorption machines. These documents here and here are available. We are still analyzing what these samples might be able to tell about conditions at the plant.
TEPCO Decontaminating Unit 2 First Floor
TEPCO began work to decontaminate the interior 1st floor of unit 2 with a new set of robots.
TEPCO doing 3D Scans Of Units 1 & 2
TEPCO is conducting both manned and robotic 3D scans of units 1 and 2. It appears the work is towards eventually installing covers or defueling buildings. Unit 2 will have the torus room and corners of the building basement inspected. Both units will have the 1st floor areas done. Unit 1 may have the torus room area done but they are awaiting the creation of a robot capable of doing so.
More Shielding Added At Unit 4
Workers are continuing to have exposure problems at unit 4 while they do spent fuel pool removal work. The exposure is coming from unit 3 that has been cleaned of debris. TEPCO had put shielding in place while unit 4 was being cleaned of debris but has had to put it back in place on the defueling building. Unit 3 has since been cleared of debris. The source of the radiation from unit 3 to unit 4 has not been declared.
TEPCO Seals Drainage Canal & Covers It
TEPCO began a process of cleaning out, sealing and covering the drainage canal that has frequently allowed contaminated water to leave the plant. While Ex-SKF was a bit puzzled by the effort, this concept may have come from IRID. Efforts that prevent more contaminated water from leaking or leaching into the canal or adding rainwater to it will help keep contamination from routing to the sea. The cost of this effort was likely minimal compared to the cost for other efforts at the plant.
TEPCO Investigates Drainage Systems
TEPCO has begun investigating the drainage systems around the plant by looking at radiation levels and potential flow paths. This is something that should have been done soon after the disaster. This appears to be another possible directive from IRID. Many of the water control proposals involved blocking known water escape routes at the plant and utilizing the creek beds that exist outside the plant grounds to reroute groundwater around the plant.
While many of these efforts seem small and disjointed they do represent some small progress at the plant towards preparing for more complex work.
image credit | saynotomean.blogspot.com
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