September 30, 2011

Sep 30, 2011 | Fukushima Accident Updates

  • TEPCO has sampled the gas content of many pipes passing through the containment walls of unit #1, using hydrogen detectors with a greater sensing capacity than those used when the hydrogen was first discovered earlier this week. It turns out the concentrations are in the 61-63% range. TEPCO also analyzed for oxygen, since some oxygen must be present for an ignition or explosion. They found none. Thus, there is no danger of another hydrogen explosion. The extremely high concentration virtually confirms that the hydrogen is residual from the fuel damage period of March 12, and trapped in the piping since then. NISA has ordered TEPCO to also check the containment-penetrating pipes on units 2 and 3, which TEPCO already said they were planning this past Monday. (NHK World)The sampling of the piping in units 2 and 3 could produce some interesting results. If all three fuel cells experienced a full, core-relocating meltdown, then the residual hydrogen concentrations trapped in the three unit’s pipes should be similar. Significant differences could indicate differences in the relative severity of fuel meltage. We suspect the pipes of unit #3 will have hydrogen concentrations similar to unit #1, but unit #2’s pipes will be significantly lower.
  • It seems JAIF has decided to post plant conditions at Fukushima Daiichi on a weekly schedule, rather than daily. Thursday’s posting shows a dramatic drop in temperatures for all three RPVs. Unit #1 is at 76oC, with an injection rate of 3.8 tons per hour. Unit #2 is down to 99oC, with a total injection rate of 10 tons per hour. Unit #3 is at 79oC with a total injection rate of 11 tons per hour. (JAIF)The following diagram of the injection pathways is from Yomiuri Shimbun…Fuku feed injectIt seems the cooling water injections are doing a more efficient job on unit #1 than the other two. It also seems the use of the internal feedwater spray flow-paths on units 2 and 3 have been a success, but the higher relative flows indicate a less efficient cooling effect than unit #1. This indicates there are blockages to cooling flow inside units #2 and #3 that are not the case in unit #1. While it is true that units #2 and #3 have ~50% larger fuel cells than unit #1, this does not account for the differences in flows. The decay heat level for unit #1 is greater than with both other units because it was near the end of its fuel cycle.
  • Spent Fuel Pool temperatures on all four units are constant. Units 1-3 are in the 25oC range, and unit #4 SPF (with the largest number of stored fuel bundles) at 35oC. (JAIF)
  • According to NISA, the principle governmental regulatory group, there was a complete failure of all electrical power at the Fukushima off-site emergency response center, 5km from the power complex, an hour after the earthquake. When the earthquake-caused regional blackout happened, the response center’s emergency diesel generator started automatically. It ran for about 45 minutes, then stopped. Since the response center was a gathering point for TEPCO administrators, local officials, and Tokyo government representatives to meet and decide on public protective actions, it was imperative that the facility be re-powered. The facility blackout made it impossible for anyone at the response center to follow what was happening to the power complex and monitor the emergency systems that were (or were not) operating. At midnight, more than 8 hours into the facility blackout, a diesel generator technician discovered a faulty electrical switch on the control panel. The switch’s failure had stopped the fuel oil pump feeding the diesel. The switch was replaced and the response center was re-powered by about 3am on March 12. (Yomiuri Shimbun)According to control room records, communications between the power plant itself and outside local/federal officials was by a single land line to Fukushima City and Tokyo during the emergency response center blackout. This indicates that public protective action orders came from Fukushima City and/or Tokyo during the first 12 hours at Fukushima, and not from “local officials” nearest the power complex who were necessarily the most familiar with nuclear systems due to their physical proximity.
  • All Japanese news media outlets report that the “evacuation advisory” for 5 municipalities between 20 and 30km from Fukushima Daiichi has been formally lifted.
  • A coalition of minority parties in the Japanese Diet (2 houses of congress) have created a new, independent group to investigate into who may have been responsible for the accident at Fukushima Daiichi. The current government “panel” is trying to decide what caused the accident. The new “council” will go a step further and “clarify responsibility of key individuals” that were involved in the decisions concerning plant emergency operations and public protective actions. The council will be comprised of 10 “private sector experts”. Testimony from witnesses will be presented directly to Diet. Those expected to be called before the Diet include former Prime Minister Naoto Kan and executives of Tokyo Electric Power Co. This will be the first government organ of non-politician, private sector experts to be officially created under the Constitution, in Japan’s history. It seems that the initial wave of those giving testimony will not be sworn in. However, the council will be able to identify key individuals who will be sworn in, which means they can be punished if they commit perjury. (Asahi Shimbun)
  • Tokyo has set the official standards for decontaminating the land areas within the “no-go” and northwest corridor evacuation zones. Those locations known to have radiation fields equal to or greater than 5 millisieverts/yr will be decontaminated. This reduces the total land area which will be deconned from 2,500 km2 down to a bit less than 1,800 km2. As mentioned in previous updates, 70% of the area of concern is forest and some 50% of that is mountainous. The mountainous forest will not need to be deconned because no-one goes there, further reducing the total area to less than 900 km2. In addition, the forested area to be cleansed will not need any soil removed because the leaves and decaying material on the forest floor contains ~90% of the deposited cesium. This means there will be about 650 km2 which will need topsoil stripped down to 5cm depth. Thus, about 400,000 cubic meters of topsoil will be removed. The total material to be handled will be well-below 2 million cubic meters. That’s still a lot of waste to deal with, but not the 28 million cubic meters broadcast a few days ago. (Asahi Shimbun)The central government also says all radioactive materials amassed by decontamination procedures will be stored and or disposed of by the Prefectures within which the material is produced. (NHK World)
  • The Tokyo government has finally decided on how to dispose of the enormous amount of rubble and debris caused by the earthquake and tsunami. Some of the northeast prefectures have already begun disposal themselves, but many have done little rubble removal while waiting for Tokyo to do it for them. One of the on-going issues has been where to put this virtual mountain of debris…and they’re not talking about the cesium-laced stuff near around Fukushima Daiichi. The non-Cesium-laced debris is 10 times greater than the cesium-laced material. Regardless, Tokyo has designated 42 sites across Japan for disposal locations, and Tokyo will foot the bill. At the end of the announcement article, the government says they have found that the Cesium-laced debris within Tokyo itself is 15 times below the national standard for disposal. Thus, handling and disposal of the city’s wastes will proceed as it has for years. (Yomiuri Shimbun)We say, it’s about time! The nation’s quake/tsunami recovery is secondary to soothing unrequitable fears of radiation for way, way too long.