- Monday’s endoscopic look inside unit #2 containment (PCV) revealed 60 centimeters of water. Previously, the water level was thought to be 3-4 meters deep. This is not inside the reactor pressure vessel (RPV), but rather in the bottom of the massive containment structure surrounding it. The lower-than-expected water level indicates a greater out-flow from the PCV and into the outer suppression chamber (torus) than had been estimated. In addition, the temperature of the water was measured at about 50oC and the radiation level inside the PCV was found to be as high as 73 sieverts per hour. The water temperature indicates that any molten fuel which may have leaked out of the RPV and fallen into the bottom of the PCV is being adequately cooled. However, the radiation levels inside the unit #2 PCV makes it doubtful that similar inspections will be possible for units #1 & 3 because they are believed to have suffered much worse core damage. The videos have considerable gamma radiation interference, and the more intense fields inside units #1 & 3 would probably make the images un-viewable. A small portion of the RPV was examined and there was no evidence of damage, although TEPCO continues to assume there was at least some melt-through. Another surprising discovery was the relative transparency of the water in the bottom of the PCV. (Mainichi Shimbun and NHK World)
- On Tuesday, TEPCO reported more information on the endoscopic inspection. The 73 sievert radiation reading is directly above the water surface in the bottom of the PCV. At the opening for the endoscope, several meters above the water, the reading is about 31 sieverts. Any future endoscopes will have to be built to better withstand the high radiation levels. While these levels are too high for workers to go inside the PCV, it does not mean robots cannot go in. Recent work in unit #2’s outer chambers with the Quince II robot shows it operated in a 20 sievert radiation field for 10 hours without malfunction. Before any robotic access can be planned, however, the robots must be tested for radiation fields two to four times more intense than what they have previously experienced. The increasing radiation level as the probe goes lower into the PCV indicates that the pooled water is extremely radioactive and may well contain some melted core material that may have seeped around RPV bottom-head penetrations, like the control rod drive mechanism (CRDM) housings. While the radiation levels are higher than TEPCO anticipated, it should not affect the current time-table for decommissioning unit #2. (Japan Times)
- On Monday, TEPCO said water from their decontamination system has leaked and some has reached the sea. About 120 liters of water escaped from a pipe feeding one of the external storage tanks. The water had passed through the decontamination system, so its radiation levels are quite low, reading 0.25 Becquerels/cc of Strontium (equivalent to one radioactive disintegration every four seconds) on the outlet of the drainage ditch to the barricaded quay (port area). As of Tuesday morning, the leaking piping had been replaced and the water decontamination system was returned to full operation, treating 40 tons of water per hour. [comment – The Japanese Press says the water that leaked to the quay contains highly radioactive substances, which makes little sense considering the very low activity level.]
- Initial decontamination work in Okuma town has reduced most radiation levels by 60%. Okuma is located immediately adjacent to the F. Daiichi power complex and has some of the highest recorded radiation levels outside of the power station’s property. Most of the work has been stripping the top layer of soil, which contains perhaps 90% of the deposited Cesium. Some 16,000 tons of the stripped soil has been collected. However, high pressure spraying of concrete has been less effective at reducing radiation levels, probably because the material is porous and contamination has become imbedded. Officials are considering stripping off top layers of concrete to see if that helps. Regardless, radiation levels at people’s homes, in parks and on roads were decreased by about 60 percent. With homes, roofs were washed and topsoil was removed which dropped the radiation dosage from as high as 11.5 microsieverts per hour down to 3.9 microsieverts per hour (roughly 20 millisieverts per year). In parking lots and on roads, the level was reduced from 13.8 microsieverts per hour (72.5 millisieverts per year) to 5.3 microsieverts per hour (27.8 millisieverts per year). Meanwhile, similar work in the Fukushima city of Tamura has reduced radiation levels down to about 3 millisieverts per year and forest floors to ~3.7 mSv/year. (Mainichi Shimbun)
- With TEPCO’s shuttering of its last operating nuke, it seems hardships loom on the horizon. These include prolonged power shortages and increased electricity charges to cover fuel costs at thermal (fossil-fueled) power plants. TEPCO will be walking a power-generation “tightrope” this summer if no nukes are allowed to restart. TEPCO has installed nearly 300 portable generators and shifted their thermal plants from “peaking” operation (only during high-demand periods) to base-load (full power, 24/7). Keeping sporadically operated thermal units at constant full power this past winter resulted in at least four complete failures, which stretched TEPCO to its limits. The use of portable generators and the base-loading of thermal units are currently making up for the shuttered nukes, but how long this makeshift situation will last is anybody’s guess. (Yomiuri Shimbun)
- Fukushima Mayor Takanori Seto has taken formal umbrage with statements made by Kobe professor Tomoya Yamauchi. Yamauchi has publicly stated that Fukushima City ought to be completely evacuated in his lecture to an anti-tsunami debris gathering in Osaka on February 18. “Fukushima city needs to be evacuated,” Yamauchi said at the lecture. “The city administration isn’t doing much of anything, but there is one man there doing the right thing: the mayor. He’s living in Yamagata and goes to work in Fukushima every morning by official car.” However, Mayor Seto has done nothing of the sort. Seto said in a written statement that Yamauchi’s claims “are not true, and his comments have badly tarnished my honor. Our residents suffer because of the radiation problem, and Yamauchi’s comments have damaged the trust they put in their mayor.” Seto also demanded that Yamauchi issue a correction and apology to the news media. He may file a criminal complaint for defamation depending on the professor’s response. (Mainichi Shimbun)
- Osaka Mayor Toru Hashimoto says the city resident’s petition for a nuclear referendum has been rejected. He said that there were considerable problems in verifying the authenticity of many of the petition signatures, more than enough to invalidate the petition itself. (Asahi Shimbun)
- The Japanese Nuclear Safety Commission (NSC) plans to brief the governments of Fukui, Shiga, and Kyoto on the results of the stress tests for Oi units #3& 4. It is hoped this will ease opposition to the restart of these two units, and begin to alleviate the nation-wide power crisis. It’s not only people in Fukui who are worried about a resumption of operations at the reactors. The adjacent prefectures of Kyoto and Shiga are also demanding explanations on the stress tests and safety measures at the plant. NSC plans on beginning their briefings on Thursday. (NHK World)
- Prime Minister Noda has addressed the nuclear summit in Korea concerning nuclear safety. Noda said that people in charge of nuclear security around the world must not be lulled into a “myth of safety” concerning a natural disaster or terrorist attack. He stressed, “The workings of nature are beyond comprehension, but there is also no limit to human imagination. We should keep in mind that the man-caused act of sabotage will test our imaginations far more than any natural disaster. Every person who works toward nuclear security should take this to heart.” He also said one of the problems was a lack of coordination between civil and defense authorities in obtaining accurate information, “At times, it was difficult to know who was in charge.” (Japan Times)
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